Expandable tfe copolymers, method of making, and porous, expanded articles thereof

BACKGROUND OF THE INVENTION

0001The invention relates to fluorocopolymers, as defined herein to denote any fluoropolymer containing tetrafluoroethylene monomer units and at least or more than 1.0% by weight of units of at least one other comonomer,* polymerized to produce an expandable tetrafluoroethylene copolymer of the fine powder type. A process of polymerization of these monomers is described, as well as the porous products produced by expansion (stretching under controlled conditions) of the aforesaid copolymers.

0002Techniques for the dispersion polymerization of tetrafluoroethylene (TFE) monomer are known. Dispersion polymerization of TFE produces a resin that has come to be known as "fine powder". See, e.g., <patcit id="pcit0001" dnum="US4016345A"><text>U.S. Patent 4,016,345 (Holmes, 1977</text></patcit>). In such processes, generally, sufficient dispersing agent is introduced into a water carrier such that, upon addition of tetrafluoroethylene monomer in the presence of a suitable polymerization initiator and, upon agitation and under autogenous tetrafluoroethylene pressure of 10 to 40 kg/cm², the polymerization proceeds until the level of colloidally dispersed polymer particles is reached and the reaction is then stopped.

0003In contrast, particulate tetrafluoroethylene resins have also been produced by a process of suspension polymerization wherein tetrafluoroethylene monomer is polymerized in a highly agitated aqueous suspension in which little or no dispersing agent is employed. The type of particles produced in suspension polymerization has been termed "granular" resin or "granular powder". See, e.g., <patcit id="pcit0002" dnum="US3655611A"><text>U.S. Patent 3,655,611 (Mueller, 1972</text></patcit>).

0004For both polymerization processes, copolymerization of tetrafluoroethylene with various fluorinated alkyl ethylene comonomers has been described. See, for example, <patcit id="pcit0003" dnum="US4792594A"><text>U.S. Patent 4,792,594 (Gangal, et al., 1988</text></patcit>). However, the present invention relates, specifically, to the aqueous dispersion polymerization technique, in which the product of the polymerization reaction is the copolymer of the invention dispersed within an aqueous colloidal dispersion. In this process, tetrafluoro-ethylene monomer is pressured into an autoclave containing water and polymerization initiators, along with paraffin wax to suppress coagulum formation and an emulsifying agent. The reaction mixture is agitated and the polymerization is carried out at suitable temperatures and pressures. Polymerization results in the formation of an aqueous dispersion of polymer particles, and the dispersed polymer particles may subsequently be coagulated by techniques known in the art to obtain what has become known as the fine powder form of the polymer.

0005Various prior patents have disclosed techniques for the homopolymerization of tetrafluoroethylene and for the polymerization of TFE with small amounts (&lt;1.0% by weight) of other monomers. Among those are included <patcit id="pcit0004" dnum="US4576869A"><text>U.S. Pat. No. 4,576,869 (Malhotra, 1986</text></patcit>) and <patcit id="pcit0005" dnum="US6177533B1"><text>U.S. Pat. No. 6,177,533B1 (Jones, 2001</text></patcit>).

0006Fine powder resins are known to be useful in paste extrusion processes and in stretching (expansion) processes in which the paste-extruded extrudate, after removal of extrusion aid lubricant, is stretched to produce porous, strong products of various cross-sectional shapes such as rods, filaments, sheets, tubes, etc. Such a stretching process is disclosed in the pioneering <patcit id="pcit0006" dnum="US3953566A"><text>U.S. Pat. No. 3,953,566 (Gore, 1976</text></patcit>), assigned commonly with the instant invention.

0007The expansion process as it applies to fluorocarbon polymers is fully described in the aforesaid '566 patent, and that process has come to identify what is currently termed the "expanded" form of TFE fluoropolymers, and will serve to define what is meant herein as an expanded or expandable TFE polymer or copolymer.

0008The term "copolymer," as it has been used in connection with fluoropolymers In the prior art has been inconsistently applied. For all purposes herein, as set out in the <i>Fluoroplastics</i> text cited above and in the ISO 12086 classification cited above, the normal convention of polymer science will be followed, and the term "copolymer" will apply to any fluoropolymer containing more than 1.0% by weight of at least one comonomer in addition to TFE. A fluoropolymer containing less than 1.0% comonomer is properly categorized as a "modified" homopolymer (<i>Id</i>.), although the term "copolymer" has been misapplied in the literature when referring, in fact, to "modified" homopolymers. One must examine each particular instance of such use to determine the actual concentrations of comonomers employed to determine whether, in fact, the referenced composition is a "modified" homopolymer or a true copolymer, that is, whether or not the polymeric product, in fact, contains more than 1.0 weight percent comonomeric units. By definition herein, the invention provides a true TFE copolymer, of the fine powder type, that is expandable, as defined above, to produce useful, expanded TFE copolymeric products.

0009<patcit id="pcit0007" dnum="US4837267A"><text>U.S. Patent 4,837,267 (Malhotra, 1989</text></patcit>) discloses a three-component composition termed "core-shell TFE copolymers", which are described as non-melt processible, including chlorotrifluoroethylene (CTFE) monomer residing in the core and having recurring units of a comonomer of perfluoro(n-alkylvinyl) ether of 3-7 carbon atoms (col. 1, lines 45-55). The total comonomer content in the particles is said to be between 0.001 and 2 weight percent. The examples presented all relate to terpolymers having comonomeric concentrations much less than the range described, namely 0.23% CTFE and 0.0145% PPVE (total of 0.2445 wt %) in Example 1, and 0.13% HFP and a minute, undeterminable amount of PPVE in Example 2. The stated upper limit of 2% is therefore unsupported by the specification and examples presented. Moreover, there is no disclosure or suggestion in the '267 patent of an expanded or an expandable TFE copolymeric composition.

0010Japanese Patent Application (Kokai) <patcit id="pcit0008" dnum="JP2005306033A"><text>2005-306033A, published November 4, 2005</text></patcit>, discloses thin films of PTFE which are said to be non-porous, non-gas-permeable (p. 5), and to contain "trace monomer units" in the range of 0.001-2 mol % (p. 7) described as "modified" PTFE. The objective of the invention is said to be obtained by "heat treatment" of "porous PTFE resin film" to render the film "substantially nonporous". There is no disclosure or suggestion in this reference of a porous, expandable TFE copolymeric composition.

0011<patcit id="pcit0009" dnum="US4391940A"><text>U.S. Patent 4,391,940 (Hoechst, 1983</text></patcit>) discloses and describes a partially modified tetrafluoroethylene polymer having a "three-shell" particle structure. The resins are said to be suitable for paste extrusion to produce cable insulation and highly stretchable, unsintered tapes ('940 patent, Abstract). This patent describes fluorinated modifying monomers which are capable of copolymerizing with tetrafluoroethylene, such as perfluoropropene, perfluoroalkyl vinyl ether, and halogen-substituted or hydrogen-substituted fluoro-olefins. The specification cautions that the total amount of the comonomer modifying agent should be so low that the specific properties of the pure polytetrafluoro-ethylene are retained, that is, there remains no possibility of processing from the melt because of the extremely high melt viscosity for such modified polymers. ('940 patent, col. 1, I. 62 et seq.) Products disclosed include modified polymer particles having a core of a polymer of "0.05 to 6% by weight" of at least one modifying fluoroolefin comonomer, a first, inner shell, immediately adjacent the core, of TFE units, and a second, outer shell, immediately adjacent the inner shell, of a polymer comprising "0.1 to 15% by weight" of units of at least one modifying fluoroolefin (col. 3, I. 5, et seq.). Examples of the "three-shell" products provided in this reference for illustration of the principles disclosed therein show that tapes, upon stretching, after removal of lubricant, developed defects or tore completely at relatively modest stretch ratios. For example, the detailed procedure described in Example 31, at col. 94, I. 60 to col. 16, I. 6, produced a product which developed defects at a 4:1 stretch ratio and tore completely at a stretch ratio of 8:1 ('940 patent, Table III).

0012For comparison and to place various of the prior art disclosures in context, recently <patcit id="pcit0010" dnum="US6841594B"><text>issued U.S. Patent 6,841,594 (Jones, 2005</text></patcit>) instructs that polytetrafluoroethylene (PTFE) refers to the polymerized tetrafluoro-ethylene by Itself without any significant comonomer present, and that "modified" PTFE refers to TFE polymers having such small concentrations of comonomer that the melting point of the resultant polymer Is not substantially reduced below that of PTFE. The concentration of such comonomer, consistent with prior citations above, is preferably less than 1 weight %, more preferably less than 0.5 weight %. The modifying comonomers cited include, for example, hexafluoro-propylene (HFP), perfluoro(methyl vinyl ether) (PMVE), perfluoro (propyl vinyl ether) (PPVE), perfluoro (ethyl vinyl ether) (PEVE), chlorotrifluoroethylene (CTFE), perfluoro-butyl ethylene (PFBE), or other monomer that introduces side groups Into the molecule. These instructions are consistent with the disclosures above and with the definitions contained herein, i.e., that the term "copolymer", as contrasted with the term "modified homopolymer", shall mean any fluoropolymer containing more than 1.0% by weight of at least one comonomer In addition to TFE.

0013<patcit id="pcit0011" dnum="US6127486A"><text>U.S. Patent 6,127,486 (Burger, et. al., 2000</text></patcit>) discloses a blend of a fluoropolymer and a "thermoplastic", wherein the "thermoplastic" is said to include a "PTFE copolymer" (col. 4, I. 46). The specification instructs that, for the resins described therein, the amount of comonomer is limited such that the [modified] PTFE exhibits properties of "not being processable in the melt." (Emphasis in original). The PTFE is referred to as modified PTFE "in which the comonomers are contained In an amount below 2, preferably 1 wt. % in PTFE." (Col. 4, I. 50) No examples are provided of any copolymer having greater than 1.0 weight % of an additional comonomer, and the patent concerns blends of polymers, a different physical form entirely from the true copolymers which form the subject matter of the present invention.

0014Another recent reference, Japanese Patent Application No. <patcit id="pcit0012" dnum="JP10243976A"><text>10-243976</text></patcit> (<nplcit id="ncit0001" npl-type="b"><text>Asahi Glass Co., Ltd., claiming priority to December 26, 1997</text></nplcit>) Is still further instructive of the state of the art in the field of copolymers and modified homopolymers of TFE. That patent application, titled "Tetrafluoroethylene Copolymer and Application Thereof", contains claims to polymers having, <i>inter alia</i>, additional comonomer content in the range of 0.005 to 0.05 mol % (about 0.012 to 0.123 wt %). The patent discusses known copolymerization techniques and discloses that a further, related Japanese application, <patcit id="pcit0013" dnum="JP3066926B"><text>JP (Kokoku) 3-66926</text></patcit>, proposes a method for modifying PTFE by employing R_f-CH=CH₂ (where R_f is a C_1-10 perfluoroalkyl group) as a comonomer. In the proposed method, the comonomer Is continuously added during the polymerization process in order to enhance modification in the initial period. The modification Is said to be primarily performed in order to improve the paste extrudability of fine powders, for example, to reduce extrusion pressure, and the content of polymerization units based on comonomers, <i>while less than 0.5 wt%,</i> is "still comparatively high in substantial terms" (0.1 wt% or higher). Consequently, the product has substantially no melt moldability and possesses markedly reduced crystallinity. The reference describes "another draw-back", that such modified PTFE becomes less heat-resistant because of the structure of the comonomers introduced. Finally, the Asahl patent application concludes, quoting therefrom: <ul id="ul0001" list-style="none" compact="compact"><li>In addition, the comonomer structure Impairs molecular orientation, causing breakage during stretching and making the product substantially unusable for the manufacture of stretched porous articles.</li><li>An object of the present invention is to provide a PTFE product that has excellent extrudability, can be uniformly stretched, and yields high-strength porous articles.</li></ul>

0015This objective is then said to be obtained by <i>limiting</i> the introduction of polymerization units based on comonomers copolymerizable with TFE to an amount that has no discernible effect on processibility.

0016Specifically, the Asahi application provides a product of TFE and a fluorinated comonomer expressed by the general formula CH₂=CH-R_f (where R_f is a C_1-10 perfluoroalkyl group, wherein this polymer contains 0.005 to 0.05 mol% polymerization units based on the fluorinated comonomer. Further, a porous polymer article is provided, obtained by a process in which a powder composed of the aforementioned modified PTFE is paste-extruded and then stretched at a temperature of 250°C or higher. This reference, however, specifically cautions against polymerization In which the amount of copolymerized monomer exceeds certain limits. The application states, again quoting directly: <ul id="ul0002" list-style="none" compact="compact"><li>The content of the polymerization units based on fluorinated comonomer in the present invention must be rigorously controlled because of considerations related to stretchability. The content of the units in the PTFE must fall within a range of 0.005 to 0.05 mol%. A content above 0.05 mol% brings about a slight reduction in polymer crystallinity, results in a lower paste extrusion pressure, and has a markedly adverse effect on stretchability. A content below 0.005 mol% makes it substantially more difficult to improve the physical properties of a stretched article or to obtain other modification effects. A range of 0.01 to 0.04 mol% is particularly preferred.</li></ul>

0017This, again, is consistent with the other teachings of the prior art references discussed hereinabove. In Example 4 of this Asahi reference, in which a "high" content (by applicant's definition), 0.42wt%, of perfluorobutylethylene comonomer was employed, the paste extrusion pressure was desirably low, and "excellent" extrudability was obtained. However, a test specimen, on stretching, broke. The specification discloses, at this "high" level of comonomer concentration of 0.42 wt%, "...breakage occurred during stretching, and it was impossible to obtain a porous article." (p. 12, §0050).

0018In spite of these cautionary teachings, and in contrast thereto, the present invention is directed to true TFE copolymers, all containing in excess of 1.0 weight percent comonomer units, all of which are expandable to form porous expanded articles, to a process for their manufacture, and to the expanded articles produced thereby. No known prior art reference discloses or suggests such porous, expanded copolymeric articles or the resins from which they are produced.

0019<patcit id="pcit0014" dnum="WO2007005361A1"><text>WO 2007/005361 A1</text></patcit> (Gore Enterprise Holdings, Inc.) describes a polymerisation process for producing a tetrafluoroethylene copolymer of the dispersion/fine powder type" and the copolymer produced thereby.

0020<patcit id="pcit0015" dnum="EP1201689A1"><text>EP-A1 -1201689</text></patcit> (Asahi Glass Co. Ltd. &amp; Asahi Glass Copolymers Co., Ltd.) relates to a tetrafluoroethylene polymer described as having high stretchability, a fibrillatable character and a non-melt fabric a bulk quality and as being suitable for stretching after paste extrusion.

0021It is wholly unexpected, and contrary to prior art teachings, that a TFE copolymer, having comonomeric unit concentrations in the high ranges claimed herein, can be expanded as disclosed hereinbelow, to and beyond a 25:1 stretch ratio, to form a uniform, viable shaped article. This synergistic result is truly surprising to one skilled in this art.

SUMMARY OF THE INVENTION

0022A process is provided for the copolymerization of an expandable tetrafluoroethylene (TFE) copolymer of the fine powder type, the copolymer containing 98.0% or less by weight tetrafluoroethylene (TFE) monomer units and at least, or greater than, 2.0% by weight, of units of at least one other comonomer, that is, other than tetrafluoroethylene. The other comonomer is an ethylenically unsaturated comonomer having a sufficiently high reactivity ratio to TFE to enable polymerization therewith. The process includes the steps of copolymerizing the TFE monomer and the at least one other monomer in a pressurized reactor by feeding 98.0% or less by weight of the TFE monomer into the reactor, feeding at least or greater than 2.0% by weight of the other comonomer into the pressurized reactor, wherein percentages are based upon total weight of monomers fed, initiating polymerization of the monomers with a free radical initiator, and stopping the feeding of the other monomer at a point in time in the polymerization reaction prior to completion of the reaction. Optionally, excess comonomer is removed (evacuated) from the reactor, as needed, prior to completion of the reaction. The at least one other comonomer may be an olefin such as ethylene, propylene or isobutylene, a fluorinated monomer selected from the group consisting of chloro-trifluoroethylene (CTFE), hexafluoropropylene (HFP), vinylidene fluoride (CFH=CH₂), vinylidene difluoride (CF₂=CH₂), hexafluoroisobutylene (HFIB) and trifluoro-ethylene (CF₂=CFH), a fluorodioxole of the general formula: <chemistry id="chem0001" num="0001"><img file="EP2201050B1_D0001.tif" /></chemistry> wherein R₁ and R₂ = F or a 1-3 carbon alkyl group containing at least one fluorine, and X, Y may be F and/or H; a fluorodioxole of the general formula: <chemistry id="chem0002" num="0002"><img file="EP2201050B1_D0002.tif" /></chemistry> wherein R_f is a perfluoroalkyl carbon of 1-5 atoms, and R₁, R₂ may be F and/or CF₃; and a fluorodioxalane of the general formula: <chemistry id="chem0003" num="0003"><img file="EP2201050B1_D0003.tif" /></chemistry> wherein R₁, R₂ may be F and/or a perfluoroalkyl carbon of 1-5 atoms. Alternatively, the at least one other comonomer may be a perfluoroalkyl ethylene monomer such as a monomer selected from the group perfluoro-butylethylene (PFBE), perfluorohexylethylene (PFHE) and perfluoro-octylethylene (PFOE), or it may be a perfluoroalkyl vinyl ether monomer such as a monomer selected from the group consisting of perfluoro(methyl vinyl ether) (PMVE), perfluoro(ethyl vinyl ether) (PEVE), and perfluoro(propyl vinyl ether) (PPVE). More than one other comonomer may be fed into the pressurized reactor, to produce multicomponent copolymers, i.e., terpolymers, etc.

0023The monomer feeds may be introduced as a precharge in the polymerization, or the at least one other comonomer may be introduced incrementally or intermittently during the reaction.

0024The process preferably includes stopping the feeding of the at least one other comonomer at less than 90% of the reaction completion.

0025Higher concentrations of comonomer in the copolymer produced are achieved by feeding the at least one other comonomer at higher concentration levels, such as exceeding 5.0% by weight of the at least one other comonomer to the reactor.

0026The aforesaid process produces an expandable tetrafluoroethylene (TFE) copolymer of the fine powder type containing 98.0% or less by weight of polymerized tetrafluoroethylene (TFE) monomer units and at least, or greater than, 2.0% by weight, of polymerized comonomer units of the at least one other comonomer fed into the reaction, based on total weight of polymer produced. This true copolymer is expandable to a porous, expanded copolymeric material having a microstructure characterized by nodes 1 interconnected by fibrils 2, as shown in <figref idref="f0001">Fig. 1</figref>, described more fully below.

0027The expandable copolymer produced contains at least one other polymerized comonomer within the following group: olefins such as ethylene, propylene and isobutylene; fluorinated comonomers such as chloro-trifluoroethylene (CTFE), hexafluoropropylene (HFP), vinylidene fluoride (CFH=CH₂), vinylidene difluoride (CF₂=CH₂), hexafluoroisobutylene (HFIB), trifluoroethylene (CF₂=CFH), fluorodioxoles and fluorodioxalanes; and perfluoroalkyl ethylene monomers, including perfluoro-butylethylene (PFBE), perfluorohexylethylene (PFHE) and perfluorooctylethylene (PFOE), and a perfluoroalkyl vinyl ether monomer, including perfluoro(methyl vinyl ether) (PMVE), perfluoro(ethyl vinyl ether) (PEVE), and perfluoro(propyl vinyl ether) (PPVE).

0028The copolymer produced may include more than one other polymerized comonomer, and the comonomer content in the copolymer may exceed 5.0 weight % of polymerized units of the other comonomer(s).

0029The invention further provides an expandable TFE copolymer of the fine powder type as defined in claim 4.

0030The copolymer of the invention is produced in the form of fine particles dispersed within an aqueous medium which may be coagulated using known techniques to produce fine powder resins. Porous, expanded TFE copolymer materials, as defined in claim 10, having a microstructure of nodes interconnected by fibrils are further provided according to the invention. These porous, expanded copolymeric materials can be produced in the form of shaped articles such as sheets or films, tubes, rods, and continuous filaments, and these articles are generally strong, that is, their matrix tensile strengths in at least one direction exceed 344.7 bar (5,000 psi). The invention further provides such articles, as defined in claim 15. Matrix tensile strengths in at least one direction can, for certain products, exceed 2068.4 bar (30,000 psi.), thus providing extremely strong, porous, true copolymeric expanded TFE articles useful in many applications.

BRIEF DESCRIPTION OF THE DRAWING

0031The accompanying drawing, <figref idref="f0001">Fig. 1</figref>, is a SEM photomicrograph of an expanded sheet of the copolymeric resin produced according to the invention herein, taken at 200X magnification, showing the node 1 and fibril 2 microstructure of this material, the respective nodal intersections being interconnected by the multiplicity of fibrils 2.

DETAILED DESCRIPTION OF THE INVENTION

AND PREFERRED EMBODIMENTS

0032A process for the polymerization of a true tetrafluoroethylene (TFE) copolymer of the fine powder type is provided, wherein the copolymer contains polymerized comonomer units of at least one comonomer other than TFE in concentrations of at least or exceeding 2.0 weight percent, and which can exceed 5.0 weight percent, wherein the copolymer is expandable, that is, the copolymer may be expanded to produce strong, useful, expanded TFE copolymeric articles having a microstructure of nodes interconnected by fibrils.

0033The copolymer of this invention is produced by a polymerization process wherein the copolymerization reaction is started by a suitable initiator, after which initiator addition is stopped, allowing the reaction to slow down and proceed to completion, at a point between 15% and 90% of the progression of the reaction toward completion. Preferably the initiator addition is stopped at about the mid-point of the reaction, i.e., at 20-60% to completion.

0034Substantially non-telogenic dispersing agents are used. Ammonium perfluoro octanoic acid (APFO or "C-8") is one acceptable dispersing agent. Programmed addition (precharge and pumping) is known and is preferred.

0035Attention must be paid to ingredient purity to achieve the desired properties in polymerizations as described herein. Ionic impurities, which can increase ionic strength, in addition to soluble organic impurities, which can cause chain transfer or termination, must be minimized. It is clearly important to employ ultra pure water in all such polymerization reactions.

0036The break strength associated with an extruded and expanded (stretched) TFE polymeric beading produced from a particular resin is directly related to that resin's general suitability for expansion, and various methods have been employed to measure break strength. The following procedure was used to produce and test expanded beading specimens made from the copolymers of this invention, the data for which are reported hereinbelow.

0037For a given resin, 113.4 g of fine powder resin is blended together with 130 cc/lb (24.5 g) of Isopar® K. The blend is aged for about 2 hours at 22 °C in a constant temperature water bath. A 2.54 cm (1-inch) diameter cylindrical preform is made by applying about 18.6 bar (270 psig) of preforming pressure for about 20 seconds. The preform is inspected to ensure it is crack free. An extruded beading is produced by extruding the preformed, lubricated resin through a 0.254 cm (0.100 in) diameter die having a 30 degree included inlet angle. The extruder barrel is 2.54 cm (1-inch) in diameter and the ram rate of movement is 5 cm/min (20 in./min). The extruder barrel and die are at room temperature, maintained at 23 °C, plus or minus 1.5°C. The Isopar K is removed from the beading by drying it for about 25 minutes at 225-230 °C. Approximately the first and last 2.4 m (8 ft.) of the extruded beading are discarded to eliminate end effects. A 5.1 cm (2.0 in.) section of the extruded beading is expanded by stretching at 290 °C to a final length of 127 cm (50 in.) (expansion ratio of 25:1) and at an initial rate of stretch of 100% per second, which is a constant rate of 5.08 cm (2 in.) per second. Approximately a 30.5 cm (1 ft.) length from near the center of the expanded beading is removed, and the maximum break load of the removed sample held at room temperature (23 °C plus or minus 1.5°C) is measured using an Instron® tensile tester using an initial sample length of 5.08 cm (2 in.) and a crosshead speed of 30.5 cm/min (12 in/min). Measure-ments in duplicate are obtained and reported as the average value for the two samples. This procedure is similar to that described in <patcit id="pcit0016" dnum="US6177533B1"><text>U.S. Patent 6,177,533B1</text></patcit>. The expansion here is carried out at 290 °C instead of 300 °C.

0038Core-shell resin structures containing polymerized monomers additional to TFE, structurally similar to those produced by the techniques described herein, and as described earlier herein, have been known for some time. See, e.g., <patcit id="pcit0017" dnum="US4576869A"><text>U.S. Patents 4,576,869 (Malhotra</text></patcit>), <patcit id="pcit0018" dnum="US6541589B1"><text>6,541,589B1 (Baillie</text></patcit>) and <patcit id="pcit0019" dnum="US6841594B2"><text>6,841,594B2 (Jones</text></patcit>). In the examples which follow, and for the claimed compositions, the resins produced according to the present invention are all true copolymers, i.e., comonomer content exceeding 1.0 weight percent, verified using solid state NMR spectroscopy, as well as mass balance and detection of residual monomer in the gas phase of the polymerization batch, through gas chromomatography. The compositions are all expandable to a stretch ratio of at least 25:1, to form expanded copolymeric articles having their unique node, <b>1</b>, and fibril, <b>2</b>, microstructure as shown in <figref idref="f0001">Fig. 1</figref>, verifiable through SEM examination, as demonstrated below.

0039The following examples are intended to be illustrative of the invention, but are not to be construed as limiting the scope of the invention in any way.

EXAMPLE 1

0040To a 50-liter, horizontal polymerization reactor equipped with a 3-bladed agitator was added 1.5 Kg wax, 28 Kg of deionized (DI) water, 18g of ammonium perfluorooctanoic acid (APFO) and 5g of succinic acid dissolved in about 50g of DI water. The reactor and contents were heated above the melting point of the wax. The reactor was repeatedly evacuated and pressurized (to about 1 Atm or less) with TFE until the oxygen level was reduced to 20 ppm or less. The contents were briefly agitated at about 60 rpm between evacuation and purge cycles to ensure that the water was deoxygenated.

0041The reactor was heated to 83 C and agitated at 60 rpm. Subsequently, 0.8 Mpa of VDF was added followed by addition of TFE until the pressure reached 2.8 Mpa. At this time, KMNO4 in a DI water solution (0.063g/L) was injected at 80mL/min until approximately 2 kg of TFE was added. After addition of the 2nd Kg of TFE, the pressure in the reactor was reduced to 50 Kpa using vacuum and pressurized with fresh TFE to 2.8 Mpa. The KMnO4 was added at 20mL/min for the 3rd Kg of TFE and further reduced to 10mL/min for the 4th Kg of TFE. After the 4th Kg of TFE was added, KMnO4 was no longer added.

0042Approximately 320g of 20% APFO solution was added in 40mL increments, the first increment being added after about 1 Kg of TFE had been added, followed by increments after each additional Kg of TFE, so that the final increment was added after 8Kg of TFE had been reacted.

0043The polymerization reaction was then allowed to continue and the reaction stopped after 14.3Kg of TFE had been added to the reactor. The weight of the dispersion produced was 44.73 Kg containing 32.6% solids. The dispersion was coagulated with Nitric acid and dried at 170° C. The raw dispersion particle size (RDPS) of the polymer particle was 0.296 microns and the standard specific gravity was 2.156. The VDF concentration in the copolymer was measured to be 3.48 mol% (2.26 wt %). The break strength of the beading was 29.36 N (6.6 lbs).

0044The matrix tensile strength of the specimen was measured to be 2571.7 bar (37,299 psi).

Example 2

0045To a 50-liter, horizontal polymerization reactor equipped with a 3-bladed agitator was added 1.5 Kg wax, 28 Kg of deionized (DI) water, 18g of ammonium perfluoro-octanoic acid (APFO) and 5g of succinic acid dissolved in about 50g of DI water. The reactor and contents were heated above the melting point of the wax. The reactor was repeatedly evacuated and pressurized (to about 1 Atm or less) with TFE until the oxygen level was reduced to 20 ppm or less. The contents were briefly agitated at about 60 rpm between evacuation and purge cycles to ensure that the water was deoxygenated.

0046The reactor was heated to 83° C and agitated at 60 rpm. Subsequently, 0.8 Mpa of trifluoroethylene (herein designated TrFE) was added followed by addition of TFE until the pressure reached 2.8 Mpa. At this time, KMNO4 in a DI water solution (0.1 g/L) was injected at 80mL/min until approximately 0.5 kg of TFE was consumed. At this time, the rate was reduced to 40 mL/min until a second Kg of TFE was consumed. The pressure in the reactor was reduced to 50 Kpa using vacuum and pressurized with fresh TFE to 2.8 Mpa. The KMnO4 was again added at 40mL/min for the next 0.5 Kg of TFE and continued until 4 Kg of TFE was consumed. After 4 Kg of TFE was consumed, KMnO4 was no longer added.

0047Approximately 320g of 20% APFO solution was added in 40mL increments, the first increment being added after about 1 Kg of TFE had been added, followed by increments after each additional Kg of TFE, so that the final increment was added after 8Kg of TFE had been reacted.

0048The polymerization reaction was then allowed to continue and the reaction stopped after 16Kg of TFE had been added to the reactor. The weight of the dispersion produced was 45.74 Kg containing 35.8% solids. The dispersion was coagulated with Nitric acid and dried at 170 C.

0049The raw dispersion particle size (RDPS) of the polymer particle was 0.283 microns and the standard specific gravity was 2.213. The trifluoroethylene concentration in the copolymer was measured to be 3.2 mol% (2.6 wt %). The break strength of the beading specimen was 32.21 N (7.24 lbs).

0050The matrix tensile strength of the specimen was measured to be 1972.0 bar (28,602 psi).

EXAMPLE 3

0051To a 50-liter, horizontal polymerization reactor equipped with a 3-bladed agitator was added 1.5 Kg wax, 28 Kg of deionized (DI) water, 18g of ammonium perfluorooctanoic acid (APFO) and 5g of succinic acid dissolved in about 50g of DI water. The reactor and contents were heated above the melting point of the wax. The reactor was repeatedly evacuated and pressurized (to about 1 Atm or less) with TFE until the oxygen level was reduced to 20 ppm or less. The contents were briefly agitated at about 60 rpm between evacuation and purge cycles to ensure that the water was deoxygenated.

0052To the evacuated reactor, 8 mL of PFBE was charged, and the reactor was heated to 83° C and agitated at 60 rpm. Subsequently, 0.8 Mpa of VDF was added followed by addition of TFE until the pressure reached 2.8 Mpa. At this time, KMNO4 in a DI water solution (0.1 g/L) was injected at 80mL/min until approximately 2 kg of TFE was added. After addition of the second Kg of TFE, the pressure in the reactor was reduced to 50 Kpa using vacuum and pressurized with fresh TFE to 2.8 Mpa. The KMnO4 was added at 40mL/min until the 4th Kg of TFE was consumed. After the 4th Kg of TFE was added, KMnO4 was no longer added.

0053Approximately 320g of 20% APFO solution was added in 40mL increments, the first increment being added after about 1 Kg of TFE had been added, followed by increments after each additional Kg of TFE, so that the final increment was added after 8Kg of TFE had been reacted.

0054The polymerization reaction was then allowed to continue and the reaction stopped after 16Kg of TFE had been added to the reactor. The weight of the dispersion produced was 42.76 Kg containing 29.0% solids. The dispersion was coagulated with Nitric acid and dried at 170° C.

0055The raw dispersion particle size (RDPS) of the polymer particle was 0.263 microns and the standard specific gravity was 2.157. The VDF concentration in the copolymer was measured to be 4.30 mol% (2.80 wt %). The PFBE concentration in the copolymer was measured to be 0.03 mol % (0.07 wt %), yielding a total copolymer concentration in the composition of 2.87 wt%. The break strength of the beading specimen was 60.50 N (13.6 lbs).

0056The matrix tensile strength of the specimen was measured to be 3094.2 bar (44,878 psi).

EXAMPLE 4

0057To a 50-liter, horizontal polymerization reactor equipped with a 3-bladed agitator was added 1.5 Kg wax, 28 Kg of deionized (DI) water, 18g of ammonium perfluorooctanoic acid (APFO) and 5g of succinic acid dissolved in about 50g of DI water. The reactor and contents were heated above the melting point of the wax. The reactor was repeatedly evacuated and pressurized (to about 1 Atm or less) with TFE until the oxygen level was reduced to 20 ppm or less. The contents were briefly agitated at about 60 rpm between evacuation and purge cycles to ensure that the water was deoxygenated.

0058To the evacuated reactor, 19.94g of PFOE was charged, and the reactor was heated to 83 C and agitated at 60 rpm. Subsequently, 0.8 Mpa of VDF was added followed by addition of TFE until the pressure reached 2.8 Mpa. At this time, KMNO4 in a DI water solution (0.1g/L) was injected at 80mUmin until approximately 2 kg of TFE was added. After addition of the second Kg of TFE, the pressure in the reactor was reduced to 50 Kpa using vacuum and pressurized with fresh TFE to 2.8 Mpa. The KMnO4 was again added at 40mL/min until an additional 0.5 Kg of TFE was consumed and reduced to 20mL/min until 4Kg of TFE was consumed. After the 4th Kg of TFE was added, KMnO4 was no longer added.

0059Approximately 320g of 20% APFO solution was added in 40mL increments, the first increment being added after about 1 Kg of TFE had been added, followed by increments after each additional Kg of TFE, so that the final increment was added after 8Kg of TFE had been reacted.

0060The polymerization reaction was then allowed to continue and the reaction stopped after 16Kg of TFE had been added to the reactor. The weight of the dispersion produced was 42.82 Kg containing 28.4% solids. The dispersion was coagulated with Nitric acid and dried at 170° C.

0061The raw dispersion particle size (RDPS) of the polymer particle was 0.240 microns and the standard specific gravity was 2.159. The VDF concentration in the copolymer was measured to be 3.50 mol% (2.20 wt %). The PFOE concentration in the copolymer was measured to be 0.03 mol % (0.16 wt %), yielding a total copolymer concentration in the composition of 2.36 wt %. The break strength of the beading specimen was 62.72 N (14.1 lbs).

0062The matrix tensile strength of the specimen was measured to be 3325.8 bar (48,236 psi).

EXAMPLE 5

0063To a 50-liter, horizontal polymerization reactor equipped with a 3-bladed agitator was added 1.5 Kg wax, 28 Kg of deionized (DI) water, 18g of ammonium perfluorooctanoic acid (APFO) and 5g of succinic acid dissolved in about 50g of DI water. The reactor and contents were heated above the melting point of the wax. The reactor was repeatedly evacuated and pressurized (to about 1 Atm or less) with TFE until the oxygen level was reduced to 20 ppm or less. The contents were briefly agitated at about 60 rpm between evacuation and purge cycles to ensure that the water was deoxygenated.

0064To the evacuated reactor, 8mL of PFBE were charged, and the reactor was heated to 83° C and agitated at 60 rpm. Subsequently, TFE was added until the pressure reached 2.8 Mpa. At this time, KMnO4 in a DI water solution (0.063g/L) was injected at 80mL/min until approximately 1 kg of TFE was added. At this time the pressure in the reactor was reduced to 50 Kpa using vacuum and pressurized with 0.8 Mpa of VDF followed by addition of TFE until the pressure reached 2.8 Mpa. The KMnO4 was again added at 80mL/min until an additional 1 Kg of TFE was consumed at which time it was reduced to 40mL/min until 4Kg of TFE was consumed. After the fourth Kg of TFE was consumed the pressure in the reactor was reduced to 50 Kpa using vacuum and pressurized with fresh TFE to 2.8 Mpa. An additional amount of KMnO4 was added at 10mL/min until the fifth Kg of TFE was consumed. After the consumption of the fifth Kg of TFE, no more KMnO4 was added.

0065Approximately 320g of 20% APFO solution was added in 40mL increments, the first increment being added after about 1 Kg of TFE had been added, followed by increments after each additional Kg of TFE, so that the final increment was added after 8Kg of TFE had been reacted.

0066The polymerization reaction was then allowed to continue and the reaction stopped after 16Kg of TFE had been added to the reactor. The weight of the dispersion produced was 48.8 Kg containing 34.5% solids. The dispersion was coagulated with Nitric acid and dried at 170° C.

0067The raw dispersion particle size (RDPS) of the polymer particle was 0.234 microns and the standard specific gravity was 2.151. The VDF concentration in the copolymer was measured to be 3.15 mol% (2.04 wt %), and the PFBE concentration in the copolymer was measured to be 0.03 mol % (0.07 wt %), yielding a total copolymer concentration in the composition of 2.11 wt %. The break strength of the beading specimen was 38.25 N (8.6 lbs).

0068The matrix tensile strength of the specimen was measured to be 2161.0 bar (31,342 psi).

EXAMPLE 6

0069To a 50-liter, horizontal polymerization reactor equipped with a 3-bladed agitator was added 1.5 Kg wax, 28 Kg of deionized (DI) water, 18g of ammonium perfluorooctanoic acid (APFO) and 5g of succinic acid dissolved in about 50g of DI water. The reactor and contents were heated above the melting point of the wax. The reactor was repeatedly evacuated and pressurized (to about 1 Atm or less) with TFE until the oxygen level was reduced to 20 ppm or less. The contents were briefly agitated at about 60 rpm between evacuation and purge cycles to ensure that the water was deoxygenated.

0070The reactor was heated to 83° C and agitated at 60 rpm. Subsequently, TFE was added until the pressure reached 2.8 Mpa. At this time, KMnO4 in a DI water solution (0.063g/L) was injected at 80mL/min until approximately 1 kg of TFE was added. At this time the pressure in the reactor was reduced to 50 Kpa using vacuum and pressurized with 0.8 Mpa of VDF followed by addition of TFE until the pressure reached 2.8 Mpa. The KMnO4 was again added at 80mL/min until an additional 2 Kg of TFE was consumed at which time it was reduced to 40mL/min until 4Kg of TFE was consumed. After the fourth Kg of TFE was consumed the pressure in the reactor was reduced to 50 Kpa using vacuum and pressurized with fresh TFE to 2.8 Mpa. An additional amount of KMnO4 was added at 40mL/min until the fifth Kg of TFE was consumed. After the consumption of the fifth Kg of TFE, no more KMnO4 was added.

0071Approximately 320g of 20% APFO solution was added in 40mL increments, the first increment being added after about 1 Kg of TFE had been added, followed by increments after each additional Kg of TFE, so that the final increment was added after 8Kg of TFE had been reacted.

0072The polymerization reaction was then allowed to continue and the reaction stopped after 16Kg of TFE had been added to the reactor. The weight of the dispersion produced was 46.86 Kg containing 35.0% solids. The dispersion was coagulated with Nitric acid and dried at 170° C.

0073The raw dispersion particle size (RDPS) of the polymer particle was 0.265 microns and the standard specific gravity was 2.158. The VDF concentration in the copolymer was measured to be 3.35 mol% (2.17 wt %). The break strength of the beading specimen was 29.36 N (6.6 lbs).

0074The matrix tensile strength of the specimen was measured to be 1796.3 bar (26,053 psi).

EXAMPLE 7

0075To a 50-liter, horizontal polymerization reactor equipped with a 3-bladed agitator was added 1.5 Kg wax, 28 Kg of deionized (DI) water, 18g of ammonium perfluorooctanoic acid (APFO) and 5g of succinic acid dissolved in about 50g of DI water. The reactor and contents were heated above the melting point of the wax. The reactor was repeatedly evacuated and pressurized (to about 1 Atm or less) with TFE until the oxygen level was reduced to 20 ppm or less. The contents were briefly agitated at about 60 rpm between evacuation and purge cycles to ensure that the water was deoxygenated.

0076To the evacuated reactor, 8mL of PFBE was charged, and the reactor was heated to 83° C and agitated at 60 rpm. Subsequently, TFE was added until the pressure reached 2.8 Mpa. At this time, KMnO4 in a DI water solution (0.063g/L) was injected at 80mL/min until approximately 1 kg of TFE was added. At this time the pressure in the reactor was reduced to 50 Kpa using vacuum and pressurized with 0.8 Mpa of TrFE followed by addition of TFE until the pressure reached 2.8 Mpa. The KMnO4 was again added at 80mL/min until an additional 3 Kg of TFE was consumed. After the fourth Kg of TFE was consumed the pressure in the reactor was reduced to 50 Kpa using vacuum and pressurized with fresh TFE to 2.8 Mpa. An additional amount of KMnO4 was added at 40mL/min until the fifth Kg of TFE was consumed. After the consumption of the fifth Kg of TFE, no more KMnO4 was added.

0077Approximately 320g of 20% APFO solution was added in 40mL increments, the first increment being added after about 1 Kg of TFE had been added, followed by increments after each additional Kg of TFE, so that the final increment was added after 8Kg of TFE had been reacted.

0078The polymerization reaction was then allowed to continue and the reaction stopped after 16Kg of TFE had been added to the reactor. The weight of the dispersion produced was 46.9 Kg containing 33.1% solids. The dispersion was coagulated with Nitric acid and dried at 170° C.

0079The raw dispersion particle size (RDPS) of the polymer particle was 0.227 microns and the standard specific gravity was 2.217. The TrFE concentration in the copolymer was measured to be 4.2 mol% (3.5 wt %), and the PFBE concentration in the copolymer was measured to be 0.03 mol % (0.07 wt %), yielding a total copolymer concentration in the composition of 3.57 wt %. The break strength of the beading specimen was 15.48 N (3.48 lbs).

0080The matrix tensile strength of the specimen was measured to be 922.7 bar (13,382 psi).

EXAMPLE 8

0081To a 50-liter, horizontal polymerization reactor equipped with a 3-bladed agitator was added 1.5 Kg wax, 28 Kg of deionized (DI) water, 18g of ammonium perfluorooctanoic acid (APFO) and 5g of succinic acid dissolved in about 50g of DI water. The reactor and contents were heated above the melting point of the wax. The reactor was repeatedly evacuated and pressurized (to about 1 Atm or less) with TFE until the oxygen level was reduced to 20 ppm or less. The contents were briefly agitated at about 60 rpm between evacuation and purge cycles to ensure that the water was deoxygenated.

0082The reactor was heated to 83° C and agitated at 60 rpm. Subsequently, TFE was added until the pressure reached 2.8 Mpa. At this time, KMnO4 in a DI water solution (0.063g/L) was injected at 80mL/min until approximately 1 kg of TFE was added. At this time the pressure in the reactor was reduced to 50 Kpa using vacuum and pressurized with 0.8 Mpa of TrFE followed by addition of TFE until the pressure reached 2.8 Mpa. The KMnO4 was again added at 80mL/min until an additional 3 Kg of TFE was consumed. After the fourth Kg of TFE was consumed the pressure in the reactor was reduced to 50 Kpa using vacuum and pressurized with fresh TFE to 2.8 Mpa. An additional amount of KMnO4 was added at 40mL/min until the fifth Kg of TFE was consumed. After the consumption of the fifth Kg of TFE, no more KMnO4 was added.

0083Approximately 320g of 20% APFO solution was added in 40mL increments, the first increment being added after about 1 Kg of TFE had been added, followed by increments after each additional Kg of TFE, so that the final increment was added after 8Kg of TFE had been reacted.

0084The polymerization reaction was then allowed to continue and the reaction stopped after 16Kg of TFE had been added to the reactor. The weight of the dispersion produced was 47.22 Kg containing 34.8% solids. The dispersion was coagulated with Nitric acid and dried at 170° C.

0085The raw dispersion particle size (RDPS) of the polymer particle was 0.276 microns and the standard specific gravity was 2.219. The TrFE concentration in the copolymer was measured to be 4.17 mol% (3.5 wt %). The break strength of the beading specimen was 17.57 N (3.95 lbs).

0086The matrix tensile strength of the specimen was measured to be 1056.9 bar (15,329 psi).

EXAMPLE 9 (not an example of the invention)

0087To a 50-liter, horizontal polymerization reactor equipped with a 3-bladed agitator was added 1.5 Kg wax, 28 Kg of deionized (DI) water, 18g of ammonium perfluorooctanoic acid (APFO) and 5g of succinic acid dissolved in about 50g of DI water. The reactor and contents were heated above the melting point of the wax. The reactor was repeatedly evacuated and pressurized (to about 1 Atm or less) with TFE until the oxygen level was reduced to 20 ppm or less. The contents were briefly agitated at about 60 rpm between evacuation and purge cycles to ensure that the water was deoxygenated.

0088The reactor was heated to 83° C and agitated at 60 rpm. Subsequently, TFE was added until the pressure reached 2.8 Mpa. At this time, KMnO4 in a DI water solution (0.063g/L) was injected at 80mL/min until approximately 1 kg of TFE was added. At this time the pressure in the reactor was reduced to 50 Kpa using vacuum and pressurized with 1.2 Kg of HFP followed by addition of TFE until the pressure reached 1.9 Mpa. The KMnO4 was again added at 80mL/min until an additional three Kg of TFE was consumed. After the 4^th Kg of TFE was consumed the pressure in the reactor was reduced to 50 Kpa using vacuum and pressurized with fresh TFE to 2.8 Mpa. An additional amount of KMnO4 was added at 80mL/min until the fifth Kg of TFE was consumed. After the consumption of the fifth Kg of TFE, no more KMnO4 was added.

0089Approximately 320g of 20% APFO solution was added in 40mL increments, the first increment being added after about 1 Kg of TFE had been added, followed by increments after each additional Kg of TFE, so that the final increment was added after 8Kg of TFE had been reacted.

0090The polymerization reaction was then allowed to continue and the reaction stopped after 16Kg of TFE had been added to the reactor. The weight of the dispersion produced was 48.54 Kg containing 30.4% solids. The dispersion was coagulated with Nitric acid and dried at 170° C.

0091The raw dispersion particle size (RDPS) of the polymer particle was 0.302 microns and the standard specific gravity was 2.157. The HFP concentration in the copolymer was measured to be 0.77 mol% (1.25 wt%). The break strength of the beading specimen was 33.81 N (7.60 lbs).

0092The matrix tensile strength of the specimen was measured to be 2356.5 bar (34,178 psi).

EXAMPLE 10

0093To a 50-liter, horizontal polymerization reactor equipped with a 3-bladed agitator was added 1.5 Kg wax, 28 Kg of deionized (DI) water, 18g of ammonium perfluorooctanoic acid (APFO), 0.2g FeSO4 and 5g of succinic acid dissolved in about 50g of DI water. The reactor and contents were heated above the melting point of the wax. The reactor was repeatedly evacuated and pressurized (to about 1 Atm or less) with TFE until the oxygen level was reduced to 20 ppm or less. The contents were briefly agitated at about 60 rpm between evacuation and purge cycles to ensure that the water was deoxygenated.

0094The reactor was heated to 83° C and agitated at 60 rpm. Subsequently, 0.81 Mpa of CTFE was added followed by addition of TFE until the pressure reached 2.8 Mpa. At this time, a solution containing 3g ammonium persulfate and 3g sodium hydrosulfite in 2000mL of DI water was injected at 40mL/min until 2Kg of TFE was consumed. After addition of the second Kg of TFE, the pressure in the reactor was reduced to 50 Kpa using vacuum and pressurized with fresh TFE to 2.8 Mpa. Additional initiator solution was again added at 20mL/Min until a total of 2.5Kg of TFE was consumed. At this time the rate was reduced to 10mL/min. After 3Kg of total TFE was consumed no more initiator was added.

0095Approximately 320g of 20% APFO solution was added in 40mL increments, the first increment being added after about 1 Kg of TFE had been added, followed by increments after each additional Kg of TFE, so that the final increment was added after 8Kg of TFE had been reacted.

0096The polymerization reaction was then allowed to continue and the reaction stopped after 16Kg of TFE had been added to the reactor. The weight of the dispersion produced was 48.07 Kg containing 35.0% solids. The dispersion was coagulated with Nitric acid and dried at 170° C. The raw dispersion particle size (RDPS) of the polymer particle was 0.245 microns and the standard specific gravity was 2.228. The CTFE concentration in the copolymer was measured to be 3.9 mol% (4.5 wt %). The break strength of the beading specimen was 33.81 N (7.6 lbs).

0097The matrix tensile strength of the specimen was measured to be 1654.1 bar (23,991 psi).

EXAMPLE 11

0098To a 50-liter, horizontal polymerization reactor equipped with a 3-bladed agitator was added 1.5 Kg wax, 28 Kg of deionized (DI) water, 18g of ammonium perfluorooctanoic acid (APFO), 0.2g FeSO4 and 5g of succinic acid dissolved in about 50g of DI water. The reactor and contents were heated above the melting point of the wax. The reactor was repeatedly evacuated and pressurized (to about 1 Atm or less) with TFE until the oxygen level was reduced to 20 ppm or less. The contents were briefly agitated at about 60 rpm between evacuation and purge cycles to ensure that the water was deoxygenated.

0099To the evacuated reactor, 8 mL of PFBE was charged, and the reactor was heated to 83° C. and agitated at 60 rpm. Subsequently, 0.81 Mpa of CTFE was added followed by addition of TFE until the pressure reached 2.8 Mpa. A solution containing 3g ammonium persulfate and 3g sodium hydrosulfite in 2000mL of DI water was injected at 40mL/min until 2 Kg of TFE were consumed. After addition of the second Kg of TFE, the pressure in the reactor was reduced to 50 Kpa using vacuum and pressurized with fresh TFE to 2.8 Mpa. Additional initiator solution was again added at 20mL/Min until a total of 3.0 Kg of TFE was consumed. After the third Kg of TFE was consumed, no more initiator was added.

0100Approximately 320g of 20% APFO solution was added in 40 mL increments, the first increment being added after about 1 Kg of TFE had been added, followed by increments after each additional Kg of TFE, so that the final increment was added after 8 kg of TFE had been reacted.

0101The polymerization reaction was then allowed to continue and the reaction stopped after 16 Kg of TFE had been added to the reactor. The weight of the dispersion produced was 48.07 Kg containing 35.0% solids. The dispersion was coagulated with Nitric acid and dried at 170° C.

0102The raw dispersion particle size (RDPS) of the polymer particle was 0.178 microns and the standard specific gravity was 2.247. The CTFE concentration in the copolymer was measured to be 3.1 mol % (3.70 wt %) and the PFBE concentration in the polymer was measured to be 0.03 mol % (0.07 wt %), yielding a total copolymer concentration in the composition of 3.77 wt %.

0103The break strength of the beading specimen was 15.48 N (3.48 lbs).

EXAMPLE 12

0104To a 50-liter, horizontal polymerization reactor equipped with a 3-bladed agitator was added 1.5 Kg wax, 28 Kg of deionized (DI) water, 18g of ammonium perfluorooctanoic acid (APFO)and 5g of succinic acid dissolved in about 50g of DI water. The reactor and contents were heated above the melting point of the wax. The reactor was repeatedly evacuated and pressurized (to about 1 Atm or less) with TFE until the oxygen level was reduced to 20 ppm or less. The contents were briefly agitated at about 60 rpm between evacuation and purge cycles to ensure that the water was deoxygenated.

0105The reactor was heated to 83° C, and agitated at 60 rpm. Subsequently, 2.0 Mpa of VDF was added followed by addition of TFE until the pressure reached 2.8 Mpa. At this time, KMnO4 in a DI water solution (0.063g/L) was injected at 80mL/min until approximately 4 kg of TFE were added. The KMnO4 was added at 40mL/min during addition of the next 2 kg of TFE. After 6 Kg of TFE was consumed, no more KMnO4 was added.

0106Approximately 320g of 20% APFO solution were added in 40mL increments, the first increment being added after about 1 kg of TFE had been added, followed by increments after each additional Kg of TFE, so that the final increment was added after 8 kg of TFE had been reacted.

0107The polymerization reaction was then allowed to continue and the reaction stopped after 16 Kg of TFE had been added to the reactor. The weight of the dispersion produced was 48.64 Kg containing 31.2% solids. The dispersion was coagulated with Nitric acid and dried at 170° C.

0108The raw dispersion particle size (RDPS) of the polymer particle was 0.321 microns and the standard specific gravity was 2.137. The VDF concentration in the copolymer was measured to be 11.8 mol % (7.90 wt %).

0109The break strength of the beading specimen was 46.84 N (10.53 lbs). The matrix tensile strength of the specimen was measured to be 2551.1 bar (37,000 psi).

0110A summary of the results given in the above Examples is provided in Table 1. The foregoing examples are provided to illustrate, without limitation, certain preferred embodiments of copolymers produced according to the principles described herein. Additional copolymers, terpolymers, etc., incorporating comonomers that are known to be reactive with TFE, can also be used. These additional comonomers can be added in a predetermined concentration and allowed to react, with or without evacuation, based on the monomers' reactivity ratio to TFE, all of which is known to one skilled in the art, as illustrated in the published literature (see, e.g., <nplcit id="ncit0002" npl-type="b"><text>Well-Architectured Fluoropolymers: Synthesis, Properties, and Applications; Elsevier; Amsterdam 2004, pp. 209</text></nplcit>). <tables id="tabl0001" num="0001"><table frame="none"><title>Table 1</title><tgroup cols="8" colsep="0" rowsep="0"><colspec colnum="1" colname="col1" colwidth="18mm" /><colspec colnum="2" colname="col2" colwidth="26mm" /><colspec colnum="3" colname="col3" colwidth="17mm" /><colspec colnum="4" colname="col4" colwidth="14mm" /><colspec colnum="5" colname="col5" colwidth="28mm" /><colspec colnum="6" colname="col6" colwidth="30mm" /><colspec colnum="7" colname="col7" colwidth="19mm" /><colspec colnum="8" colname="col8" colwidth="18mm" /><thead><row><entry valign="middle">Example</entry><entry valign="top">Added comonomer(s)</entry><entry valign="top">Particle size, microns</entry><entry valign="middle">SSG</entry><entry valign="top">Extrusion pressure, bar (psig)</entry><entry valign="top">Extrudate strength, bar (psi)</entry><entry valign="top">Break Strength, N (lbs)</entry><entry valign="top">MTS, Bar (psi)</entry></row></thead><tbody><row><entry>1</entry><entry>VDF</entry><entry>0.296</entry><entry>2.156</entry><entry>241.3 (3500)</entry><entry>72.12 (1046)</entry><entry>46.26 (10.40)</entry><entry>2571.7 (37,299)</entry></row><row><entry>2</entry><entry>TrFE</entry><entry>0.283</entry><entry>2.213</entry><entry>241.4 (3501)</entry><entry>63.8 (926)</entry><entry>32.21 (7.24)</entry><entry>1972.0 (28,602)</entry></row><row><entry>3</entry><entry>VDF/PFBE</entry><entry>0.263</entry><entry>2.157</entry><entry>272.8 (3956)</entry><entry>78.53 (1139)</entry><entry>60.50 (13.60)</entry><entry>3094.2 (44,878)</entry></row><row><entry>4</entry><entry>VDF/PFOE</entry><entry>0.240</entry><entry>2.159</entry><entry>296.1 (4294)</entry><entry>86.67 (1257)</entry><entry>62.72 (14.10)</entry><entry>3325.8 (48,236)</entry></row><row><entry>5</entry><entry>VDF/PFBE</entry><entry>0.234</entry><entry>2.151</entry><entry>236.8 (3434)</entry><entry>65.1 (944)</entry><entry>38.25 (8.60)</entry><entry>2161.0 (31,342)</entry></row><row><entry>6</entry><entry>VDF</entry><entry>0.265</entry><entry>2.158</entry><entry>215.3 (3123)</entry><entry>59.4 (862)</entry><entry>29.36 (6.60)</entry><entry>1796.3 (26,053)</entry></row><row><entry>7</entry><entry>TrFE/PFBE</entry><entry>0.227</entry><entry>2.217</entry><entry>242.8 (3522)</entry><entry>66.4 (963)</entry><entry>15.48 (3.48)</entry><entry>922.7 (13,382)</entry></row><row><entry>8</entry><entry>TrFE</entry><entry>0.276</entry><entry>2.219</entry><entry>212.7 (3085)</entry><entry>58.4 (847)</entry><entry>17.57 (3.95)</entry><entry>1056.9 (15,329)</entry></row><row><entry>9</entry><entry>HFP</entry><entry>0.300</entry><entry>2.157</entry><entry>231.0 (3350)</entry><entry>68.1 (988)</entry><entry>33.81 (7.60)</entry><entry>2356.5 (34,178)</entry></row><row><entry>10</entry><entry>CTFE</entry><entry>0.245</entry><entry>2.228</entry><entry>251.0 (3640)</entry><entry>65.7 (953)</entry><entry>33.81 (7.60)</entry><entry>1654.1 (23,991)</entry></row><row><entry>11</entry><entry>CTFE/PFBE</entry><entry>0.177</entry><entry>2.247</entry><entry>263.2 (3817)</entry><entry>73.84 (1071)</entry><entry>24.47 (5.50)</entry><entry>1084.0 (15,722)</entry></row><row><entry>12</entry><entry>VDF</entry><entry>0.321</entry><entry>2.137</entry><entry>283.4 (4110)</entry><entry>71.98 (1044)</entry><entry>46.84 (10.53)</entry><entry>2551.1 (37,000)</entry></row></tbody></tgroup></table></tables>