Claims
- 1. A method of improving stress crack resistance comprising the steps of:
a) providing a fluorothermoplastic composition comprising interpolymerized units derived from:
about 94 to about 97.5 mole percent (mol %) tetrafluoroethylene (TFE); about 2 to about 3 mol % perfluoro (propyl vinyl ether) (PPVE); and about 0.5 to about 3 mol % hexafluoropropylene (HFP); wherein the fluorothermoplastic lacks a significant melt peak above 300° C. as measured via differential scanning calorimetry (DSC), and/or a number of double flexure cycles to failure that fits the equation:log(flex life cycles)≧0.71+4.0*(MFI(−0.294));b) shaping an article from the composition; and c) exposing the article to a stress cracking agent.
- 2. The method of claim 1 wherein the stress cracking agent is selected from alkanes, lower alcohols, and fluorinated surfactants.
- 3. The method of claim 1 wherein the step of exposing the article endures for at least 30 days without the occurrence of stress cracking.
- 4. The method of claim 1 wherein the article is selected from tubing, tube fittings, films, and coatings.
- 5. The method of claim 1 wherein the resultant fluorothermoplastic additionally has at least one property selected from: lacking a significant melt peak above 300° C. as measured by DSC; a surface roughness below about 150 nm as measured by optical interferometry; a Stress Crack Resistance greater than a comparative fluorothermoplastic composition having a similar melt flow index; and a Stress Crack Resistance greater than a comparative fluorothermoplastic composition having a similar melt flow index and a higher level of PPVE.
- 6. The method of claim 1 further comprising one or more comonomers selected from the group consisting of: CF2═CFOCF3, CF2═CFOCF2CF3, CF2═CFOCF2CF(CF3)OCF2CF2CF3, CF2═CFOCF2CF(CF3)OCF2CF(CF3)OCF2CF2CF3, CF2═CFOCF2CF2OCF3, and CF2═CFOCF2CF2CF2OCF3.
- 7. A method of improving stress crack resistance comprising the steps of:
a) providing a fluorothermoplastic composition comprising interpolymerized units derived from:
about 94 to about 97 mole percent (mol %) tetrafluoroethylene; about 0.75 to about 3 mol % perfluoro (propyl vinyl ether); and about 1.5 to about 3.5 mol % hexafluoropropylene; wherein the fluorothermoplastic lacks a significant melt peak above 300° C. as measured via differential scanning calorimetry (DSC); and/or a number of double flexure cycles to failure that fits the equation:log(flex life cycles)≧0.71+4.0*(MFI(−0.294));b) shaping an article from the composition; and c) exposing the article to a stress cracking agent.
- 8. The method of claim 7 wherein the stress cracking agent is selected from alkanes, lower alcohols, and fluorinated surfactants.
- 9. The method of claim 7 wherein the step of exposing the article endures for at least 30 days without the occurrence of stress cracking.
- 10. The method of claim 7 wherein the resultant fluorothermoplastic additionally has at least one property selected from: a surface roughness below about 150 nm as measured by optical interferometry; a Stress Crack Resistance greater than a comparative fluorothermoplastic composition having a similar melt flow index; and a Stress Crack Resistance greater than a comparative fluorothermoplastic composition having a similar melt flow index and a higher level of PPVE.
- 11. The method of claim 7 further comprising one or more comonomers selected from the group consisting of: CF2═CFOCF3, CF2═CFOCF2CF3, CF2═CFOCF2CF(CF3)OCF2CF2CF3, CF2═CFOCF2CF(CF3)OCF2CF(CF3)OCF2CF2CF3, CF2═CFOCF2CF2OCF3, and CF2═CFOCF2CF2CF2OCF3.
- 12. The method of claim 7 wherein the article is selected from tubing, tube fittings, films, and coatings.
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional of U.S. Ser. No. 09/904,235, filed Jul. 12, 2001, now allowed, the disclosure of which is herein incorporated by reference.
Divisions (1)
|
Number |
Date |
Country |
Parent |
09904235 |
Jul 2001 |
US |
Child |
10680537 |
Oct 2003 |
US |