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Core/shell fluoropolymer

A technology of polymers and copolymers, which is applied in transportation, packaging, thin material processing, etc., and can solve the problems of PFA tensile strength reduction and toughness reduction

Inactive Publication Date: 2014-10-08
EI DU PONT DE NEMOURS & CO
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] Figure 7 of '533 discloses that the addition of melt-processable PTFE to PFA essentially results in a decrease in the tensile strength of the PFA, characterized in Figure 7 as a decrease in toughness as the amount of PTFE additive increases from 5% by weight

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example

[0036] The tensile strength and elongation (at break) are determined by the method of ASTM D 638-03, as modified by ASTM D3307, Section 9.6, and the determination is made on dumbbell-shaped test specimens, which are 15 mm wide by 38 mm Long and 5 mm thick, stamped from a 60 mil (1.5 mm) thick die block. Tensile strength and elongation were measured at 23°C ± 2°C.

[0037] Compression molding of slabs is performed on the composition by adding a core / shell polymer in Melt compounded in an extruder as described in Comparative Examples. Compression molding was performed at a force of 20,000 lbs (9070 kg) and a temperature of 343°C to produce 7 x 7 inch (17.8 x 17.8 cm) panels. More specifically, 80 grams of this composition was added to a 63 mil (1.6 mm) thick frame. The frame defines a panel size of 17.8 x 17.8 cm. To avoid sticking to the flat plate of the compression molding machine, the frame and composition packing were sandwiched between two aluminum sheets. The combin...

example 1

[0045] Example 1: Melt processable PTFE core / PFA shell

[0046] In this example a core / shell polymer was prepared in which the core of melt processable PTFE constituted 20% by weight of the core / shell polymer and the shell of PFA constituted 80% by weight of the core / shell polymer.

[0047] Preload the polymerization reactor with:

[0048] 54.0lb (24.5kg) water

[0049] 240 mL of 20% by weight aqueous ammonium perfluorooctanoate solution

[0050] 5.0g 157FSL functional fluid (carboxylic acid)

[0051] Solutions and liquids pumped into the reactor:

[0052] 1. 2.6g ammonium persulfate (APS) and 28g disuccinic acid peroxide (DSP), diluted with water to 1000mL (initiator solution 1)

[0053] 2. PPVE (pure)

[0054] 3. 2.0g APS, diluted with water to 1000mL (initiator solution 2)

[0055] Operation process:

[0056] 1. Pressure test at 25°C and 350 psig. Stir at 50 rpm.

[0057] 2. Evacuate and purge 3 times with TFE at 25°C.

[0058] 3. Pressurize the reactor with e...

example 2

[0084] Example 2: PFA Core / Melt Processable PTFE Shell

[0085] In this example a core / shell polymer was prepared wherein the core of melt processable PTFE constituted 20% by weight of the core / shell polymer and the shell of PFA constituted 80% by weight of the core / shell polymer.

[0086] The polymerization, coagulation and drying process of Example 1 was repeated, except that steps 12-17 were performed before steps 3-9, so that TFE / PPVE copolymerization was performed first to form the core of the core / shell polymer, followed by polymerization to form a melt processable PTFE shell.

[0087]The RDPS of the core / shell polymer was 0.182 microns. The MFR of the core / shell polymer is 8.9 g / 10 min and its tensile strength is 3441 psi (23.7 MPa). This tensile strength was 16% higher than that of the comparative composition having the same proportion of the same polymer components.

[0088] Compositions derived from the core / shell polymers of Examples 1 and 2 showed improvements...

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Abstract

A core / shell polymer is provided and is optionally heat aged, wherein the core comprises one of (a) melt-fabricable tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer and (b) melt- processible polytetrafluoroethylene and the shell comprises the other of (a) and (b), wherein the amount of (b) in said core / shell polymer is 15 to 45 wt% based on the total weight of (a) and (b) whether (b) is the core or shell of the core / shell polymer.

Description

technical field [0001] The present invention relates to combinations of melt-processable polytetrafluoroethylene and melt-fabricable tetrafluoroethylene / -perfluoro(alkyl vinyl ether) copolymers which provide improved tensile strength. Background technique [0002] US Patent 6,436,533 discloses dry blending of PTFE and PFA followed by melt extrusion of the dry blend into pellets which can then be melted for melt spinning into fibers or the dry blend is melt extruded Combination with melt spinning without formation of intermediate pellets (column 4, lines 21-35). Extrusion of the dry blend achieves melt mixing of separately supplied PTFE and PFA. Alternatively, PTFE and PFA can be fed into separate extruders, which are then added to a mixing device, such as a third extruder, to form a blend of PTFE and PFA, which can then be melt spun Silk into fibers (column 4, lines 46-51). PTFE is disclosed as having a low molecular weight such that it exhibits a melt viscosity close to ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C08F259/08
CPCC08J7/08C08L2205/02C08L27/18C08F259/08C08J2427/18C08J2327/12Y10T428/2989C08F214/262C08F214/26C08F216/1408
Inventor R.M.阿坦H.E.伯奇
Owner EI DU PONT DE NEMOURS & CO