Which factors contribute to crazing in transparent plastic windows and windshields?

• A. Exposure to ultraviolet light, stress, solvents, and improper handling
• B. Exposure to ultraviolet light only
• C. Stress and solvents only
• D. Improper handling only

Answer: (C)

Crazing shows up as fine, networked cracks in a clear plastic when the material is stressed and exposed to chemicals. The glassy appearance comes from microcracks that form and propagate along internal stress fields. When a polycarbonate or similar transparent window is under mechanical stress—such as from mounting, bending, or temperature cycling—any cleaning agents or solvents that can soften or swell the polymer will diffuse into the surface. This solvent uptake lowers the cohesive strength locally, allowing tiny cracks to develop and connect under the existing stress, creating the visible craze pattern.

Ultraviolet light can age plastics, but on its own it isn’t the primary driver of crazing in these windows, especially where UV stabilizers are used. Improper handling by itself tends to cause scratches rather than the distinct craze cracks, though rough handling can contribute if it creates stress or exposes the surface to solvents. So the combination of stress with solvent exposure best explains crazing, making stress and solvents the most relevant factors.