Diffusion and morphological properties of syndiotactic polypropylene (sPP) films

Abstract

Four different fabrication procedures were used for casting thin films of syndiotactic polypropylene (sPP). A hot press system operated at 200°C and 30 MPa pressure was used to melt polypropylene powder and make the cast films. Different cooling procedures were used to anneal the films, including cooling in liquid nitrogen (LN), ice water, and air at room temperature (RT). The morphological and mass transfer properties of the films were studied with XRD, polarized optical microscopy, bulk flow, and diffusion experiments. All sPP films contained amorphous and crystalline phases. The crystalline phase was determined to be disordered Form I. The sPP films annealed with LN had the lowest crystallinity whereas the sPP films cooled in air at RT had the highest crystallinity. Diffusion of toluene in the films and comparison with Maxwell's equation indicated that the crystalline phase mass permeability is much lower than the amorphous phase, which causes films with low crystallinity to have a higher effective diffusion constant and permeability compared with high crystallinity films. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

Characterization of toluene and 2-methylnaphthalene transport separated by syndiotactic polystyrene having various crystalline forms

“…The diffusivity for the d e -and b-sPS films was smaller because of the existence of crystalline regions. As reported in our previous paper concerning toluene transport in syndiotactic polypropylene film, 30 the lag time strongly depends on the level of crystallinity, and the crystallinities of d e -and b-sPS are 38.6 and 55.7%, respectively. Therefore, the diffusivity of the b-sPS film was smaller, on the order of 10 2 , than that of the d e -sPS film.…”

“…30 The diffusion cell was separated into two compartments (reservoir and sink) by sPS film. The reservoir was filled with 10 mM toluene or 2-methylnaphthalene in hexane, while the sink was filled with hexane.…”

“…We previously reported the separation of toluene from a hexane solution by diffusion through syndiotactic polypropylene films, which has four different crystallinities. 30 As toluene diffuses only in the amorphous phase of syndiotactic polypropylene but not in crystalline phase, the toluene diffusivity depended on the crystallinity.…”