Abstract
The following facts have been clarified by DTA, PSPC X-ray scattering, ultrasonic measurements, optical microscopy, and Raman spectroscopy under high pressure. At high pressure on heating polyethylene has a transition from an extended-chain orthorhombic phase to a liquid crystal-like hexagonal phase after passing through a lamella-thickening of the folded-chain orthorhombic phase and finally melts. On cooling polyethylene has a transition from the liquid crystal-like hexagonal phase to the extended-chain orthorhombic phase after passing through a two-dimensional diffusion controlled crystallization. At high pressure on heating poly(vinylidene fluoride) has a transformation from the folded-chain form II crystal to the folded-chain form I crystal. On further heating folded-chain and extended-chain form I crystals melt after passing through a lamella-thickening stage. On cooling a two-step crystallization of extended-chain and folded-chain form I crystals occurs. Furthermore, the crystal transformation from form II to form I was observed to proceed with an activation energy of 30 kcal/mol on annealing at 4000 kg/cm2. The high-pressure annealing procedure was utilized to improve piezoelectricity of poly(vinylidene fluoride) film. The mechanism of improvement is discussed.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
