title: Phase transition in poly(vinylidene fluoride) investigated with micro-Raman spectroscopy.
abstract: The phase transition from the non-polar alpha-phase to the polar beta-phase of poly(vinylidene fluoride) (PVDF) has been investigated using micro-Raman spectroscopy, which is advantageous because it is a nondestructive technique. Films of alpha-PVDF were subjected to stretching under controlled rates at 80 degrees C, while the transition to beta-PVDF was monitored by the decrease in the Raman band at 794 cm(-1) characteristic of the alpha-phase, along with the concomitant increase in the 839 cm(-1) band characteristic of the beta-phase. The alpha-->beta transition in our PVDF samples could be achieved even for the sample stretched to twice (2x-stretched) the initial length and it did not depend on the stretching rate in the range between 2.0 and 7.0 mm/min. These conclusions were corroborated by differential scanning calorimetry (DSC) and X-ray diffraction experiments for PVDF samples processed under the same conditions as in the Raman scattering measurements. Poling with negative corona discharge was found to affect the alpha-PVDF morphology, improving the Raman bands related to this crystalline phase. This effect is minimized for films stretched to higher ratios. Significantly, corona-induced effects could not be observed with the other experimental techniques, i.e., X-ray diffraction and infrared spectroscopy.
authors.affiliation: Faculdade de Ciências e Tecnologia--UNESP, 19060-900--Presidente Prudente, SP, Brazil. case@prudente.unesp.br
authors.forename: C J L
authors.initials: CJ
authors.lastname: Constantino
authors.forename: A E
authors.initials: AE
authors.lastname: Job
authors.forename: R D
authors.initials: RD
authors.lastname: Simões
authors.forename: J A
authors.initials: JA
authors.lastname: Giacometti
authors.forename: V
authors.initials: V
authors.lastname: Zucolotto
authors.forename: O N
authors.initials: ON
authors.lastname: Oliveira
authors.forename: G
authors.initials: G
authors.lastname: Gozzi
authors.forename: D L
authors.initials: DL
authors.lastname: Chinaglia
mesh_terms: D003461:Crystallography / Q000379:methods*; D008422:Materials Testing / Q000379:methods*; D008567:Membranes, Artificial; D044367:Phase Transition; D010812:Physical Stimulation / Q000379:methods; D011145:Polyvinyls / Q000032:analysis* / Q000737:chemistry*; D013059:Spectrum Analysis, Raman / Q000379:methods*; D013314:Stress, Mechanical; D013696:Temperature; D013718:Tensile Strength; D005465:Fluorocarbon Polymers
chemical_list: D008567:Membranes, Artificial; D011145:Polyvinyls; C024865:polyvinylidene fluoride; D005465:Fluorocarbon Polymers