Plastic transparencies having improved resistance to cracking
AssigneeSwedlow, Inc.
InventorsWilliam F. Fischer, Charles A. Bailey, II
Life of this patent
Estimating the term…
Abstract
A plastic transparency for particular use as an airplane window, including 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, the volume of the member varying in accordance with the amount of moisture absorbed. 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.
Claims7
A transparency having improved resistance to crazing and cracking when exposed to an environment of variable humidity, the transparency comprising:
- a transparent, plastic sheet member having a peripheral edge surface, the sheet member being formed of a multiaxially oriented material that is absorptive of moisture, the volume of the sheet member varying in accordance with the amount of moisture absorbed;
- and
- a thin, resinous coating overlying the peripheral edge surface of the sheet member and in direct contact with it, the resinous coating having a moisture permeation rate substantially lower than that of the underlying sheet member, whereby the magnitude of any moisture gradient adjacent the edge surface, caused by an environment of variable humidity, is reduced and the concomitant incidence of crazing and cracking in the transparency is correspondingly reduced.
In a transparency including a transparent, plastic sheet member having a peripheral edge surface, wherein the sheet member is formed of a multi-axially oriented material that is absorptive of moisture, the volume of the sheet member varying in accordance with the amount of moisture absorbed, an improvement comprising:
- a thin, resinous coating overlying the peripheral edge surface of the sheet member and in direct contact with it, the resinous coating having a moisture permeation rate substantially lower than that of the underlying sheet member, whereby the magnitude of any moisture gradient adjacent the edge surface, caused by an environment of variable humidity, is reduced and the concomitant incidence of crazing and cracking in the edge surface of the transparency is correspondingly reduced.
Dependencies are inferred from the claim text.