| 摘要 |
<p>The invention relates to a plastic transparency having improved resistance to cracking. Plastic transparencies have been used as airplane windows, but have been subject to cracking, especially when subjected to a high humidity environment. The disclosed plastic transparency includes a transparent sheet member and a thin resinous coating overlying the peripheral edge surface of the sheet member. The sheet member is formed of a multi-axially oriented plastic material that is absorptive of moisture, preferably polymethyl methacrylate. The edge coating has a moisture permeation rate substantially less than that of the underlying sheet member, so when the window is exposed to an environment of high or variable humidity, any moisture gradient adjacent the peripheral edge surface is reduced, and the resultant tensile stress and incidence of cracking in the window are correspondingly reduced.</p> |
