| 摘要 |
PURPOSE:To obtain the titled sheet large in strength by mixing St-butadiene block copolymer (SB) containing a large quantity of styrene (St) and polybutadiene or a suitable quantity of SB containing a small quantity of St with polystyrene. CONSTITUTION:When SB containing St component of 60-90wt% (A) and polybutadiene or SB containing St component of 50% or less (B) are mixed with polystyrene, resin composition wherein the weight ratio of component A to component B ranges from 0.25-2.0 and the content of component B to the whole component of the sheet ranges from 2-10% is extruded from an extruder and stretched biaxially at the stretching magnification of 1.8 or more by the inflation or tenter process, etc. to obtain the desired sheet. Besides, a test piece is cut from a biaxially stretched sheet, a crossed notch which is 100mm. in longitudinal and lateral direction is provided in the central part, the test piece is heated at 130 deg.C for 30min., the longitudinal and lateral length lM, lT of the crossed notch of the shrunk test piece are measured and the elongation percentages alpha, beta in the longitudinal and lateral directions are obtained from formulaI, II and the stretching magnification is from formula III. |
