Microscopic studies of Mylar film and its low molecular weight extracts

Abstract

Abstract Mylar polyester film has some low molecular weight material which may be extracted by various organic solvents as well as oil. This extract crystallizes in different crystal forms depending upon conditions of crystallization. Regardless of the crystal form, the Mylar extracts act alike on a hot stage, subliming without melting at 300°C. to form a sublimate which will melt sharply at 322°C. This characteristic behavior, as well as its crystallization from chloroform, forms a basis for microscopic identification of very small quantities of low molecular weight Mylar. The presence of a sublimate of low molecular weight material from raw Mylar film and the complete absence of any sublimate from extracted Mylar film makes possible rapid differentiation between raw and extracted films. This sublimate has characteristics similar to those of low molecular weight material obtained by solvent extraction. There exist in Mylar film minute areas of different refractive index which make a definite contribution to the haze level of the film. These areas are assumed to be different in crystallinity than the matrix in which they exist.