| 摘要 |
PURPOSE:To improve strength of impact remarkably by a method wherein poly methyl methacrylate having a specific molecular weight is oriented biaxially at a specific magnification of orientation to a specific thickness. CONSTITUTION:Polymethyl methacrylate having an average molecular weight 1,000,000 or more is oriented biaxially over the point of glass transition, under the melting point and at a magnification of orientation of 1.5 times or more. A biaxially oriented sheet obtained has a thickness between 1mm. and 10mm.. A sheet which is oriented biaxially up to 1.5 times or more means a biaxially oriented sheet which is oriented up to 1.5 times or more and can be shrunk down to 1.5 times or more when the sheet is heated at the melting point or more. The polymethyl methacrylate is a polymer which contains methyl methacrylate as the main substance, including copolymer containing some comonomer, a blend substance containing some additives. |
