Effect of Crystallinity on Physical Properties of PCTFE at Liquid Oxygen Temperatures (-320F)
PCTFE has long been the go to material for valve seats, seals and gaskets used in cryogenic applications. But one thing that makes PCTFE unique is that it can be processed to meet a broad molecular state, i.e. crystalline or amorphous. PCTFE is a melt fluoropolymer and when molded in either sheet, rod or tube form it can be set at a specific crystalline state through a unique quenching process. This process is not as easily manipulated with extruded PCTFE rod so if you are looking for controlled molecular values you need to consider molded product.
As an example of some of the differences in physical properties between the amorphous PCTFE and crystalline PCTFE, consider these values:
Property Amorphous Semi Crystalline Crystalline
% Crystallinity 40% 55% 65%
Ultimate Tensile (psi) 25,000 17,200 15,600
Elongation at Break (%) 4 2 1.5
Tensile Modulus of Elast. (psi) 1,110,000 NA 760,000
Compressive Strength (psi) 34,000 37,500 38,000
Flexural Strength (psi) 58,000 43,000 37,000
Flex Mod. Of Elast. (psi) 1,800,000 1,700,000 1,650,000
Crystalline/amorphous values are monitored by specific gravity and performance in cryogenic service utilizing amorphous grades of PCTFE has been well documented in terms of service life, sealability and property retention.
Ask The Experts at TriStar for more information on how PCTFE can be “custom tailored” to your application through molecular manipulation!
Tags: amorphous PCTFE, crystalline PCTFE, PCTFE in cryogenic applications, plastics for liquid oxygen service
