RELATION BETWEEN DRAWING TEMPERATURE AND CRITICAL NECKING TENSION ON ZONE-DRAWING FOR POLY(METHYL METHACRYLATE) FILMS

The relation between the drawing temperature (T(d)) and the critical n ecking tension (sigma(c)) has been investigated for amorphous and unor iented poly(methyl methacrylate) (PMMA) films. The sigma(c), defined a s the minimum tension causing a necking at a given T(d), increased wit h a decrease in T(d) in the temperature range of 80-degrees-C to 132-d egrees-C. It was found that the temperature difference between T(g) (1 10.4-degrees-C) and T(d) was proportional to the sigma(c). The relatio n is represented by the following equation: sigma(c) = C(T(g) - T(d)) where C was 0.490 MPa/degrees-C, which is close to that of poly(ether ether ketone) (PEEK) and that of poly(ethylene terephthalate) (PET), b ut is almost a half of that of poly(vinyl chloride) (PVC). The draw ra tios of the films zone-drawn at temperatures below T(g) were higher th an those of films above T(g). The negative birefringence increased wit h decreasing T(d), and that of the film drawn at T(d) = 80-degrees-C w as - 16 X 10(-4). The film drawn at T(d) = 132-degrees-C was almost is otropic.