| 摘要 |
PURPOSE:To enable to easily manufacture a polyester formed part with excellent transparency and strong mechanical strength by a method wherein a substantially un-oriented polyester sheet is firstly biaxially oriented and secondly shrunk thermally and thirdly thermoformed and finally and successively heat-treated at a temperature lower than its melting point. CONSTITUTION:Firstly, an un-oriented polyester sheet is oriented respectively in two axial directions intersecting each other at right angles. Secondly, the polyester sheet is thermally shrunk in two axial directions same as the ones, in which the sheet has been oriented at the stretching process. At this time, the final draw ratio of the sheet is preferably chosen within the range of 100-150% of the length before orientation of the polyester sheet. Thirdly and successively, the polyester sheet is formed into the desired shape through forming. Finally, the formed part is heat-treated at a temperature lower than the melting point of the raw material resin. The heat temperature of the formed part causes to crystallize the polyester. Consequently, the heat transistance of the formed part can be improved and at the same time the transparency and mechanical strength of the formed part can also be maintained. |
