Investigação de gradiente de propriedades ao longo da espessura em amostras de PVDF exposto a fluido nitrogenado

Abstract

In this work, PVDF samples were aged in nitrogen fluid at 93°C and 120°C, for up to 100 days, to investigate the effect of aging on the mechanical, thermal and microstructure properties of the polymer along its thickness. The samples were divided into three groups and were subjected to different aging conditions: samples completely exposed to the fluid, samples partially exposed to the fluid, control group, which consisted of samples exposed to air at high temperature, for evaluation only of the thermal effect over the polymer. After aging, the samples were sectioned into three regions of their thickness, each of which was characterized by TGA, DSC and instrumented microindentation analysis. With the results obtained, it was verified that only the temperature did not impose great changes in the thermal and mechanical behavior of the PVDF, the contact with the fluid induced a high mass gain and promoted changes both in the mechanical properties, EIT and HIT, as in the crystallinity, microstructure and melting temperature, originally presented by the polymer. The second heating in the DSC showed that these changes were permanent. A property gradient was also identified along the thickness of the samples partially in contact with the fluid, evidencing how the presence of the fluid is a key factor for the reordering of the crystalline structure and for the changes in the material properties, which occur gradually and heterogeneously in the different regions of the thickness of the samples, as the diffusion of the fluid from the surface to the interior of the polymer progresses.