Plastic windshields are extremely durable and less susceptible to breaking than glass windshields. Unlike glass windshields, the majority of plastic windshields are safe when put under stress. But, finding a replacement plastic windshield can be difficult. Fortunately, plastic can be repaired with acrylic solvent cement and plastic buffing compounds.
Wash the windshield on both sides with dish washing detergent and hot water. Thoroughly clean the crack. Only use a 100-percent cotton rag for cleaning the windshield to avoid scratching the polished surface. Dirt and grease can form a barrier that impedes the solvent cement from fusing the broken plastic. A crack may continue to split if not properly cemented.
Tape the area around the crack with painter masking tape, leaving a ¼" border of exposed plastic around the crack. Solvent cement can scar the finish of a plastic windshield if it spills onto the windshield surface. The tape creates a barrier between the windshield and the cement.
Fill the applicator bottle halfway with solvent cement. Acrylic solvent cement works for nearly all transparent plastics. Using the thumb and index finger, apply pressure to the sides of the bottle until the liquid is near the bottle top. Slightly release the pressure. A vacuum has now been created within the bottle, keeping the cement from spilling when the bottle is tilted during the application process.
Apply a thin bead of cement down the length of the crack on one side of the windshield. Capillary action will cause the cement to be pulled into the crack. After the cement has dried for two hours, remove the masking tape. Apply masking tape around the crack on the other side of the windshield, leaving a ¼" boarder around the crack. Apply a thin bead of cement, and allow 24 hours of drying time before proceeding to Step 5.
Apply a small amount of buffing compound onto a 100-percent cotton rag. Remove any remaining masking tape from around the crack. Buff the area around the crack until any residual cement has been polished away. The buffing compound contains an abrasive that grinds down the residual glue, while still leaving the plastic clear. Wash the windshield once more, on both sides, with dish washing detergent. The project is complete.
If the gap is too large for liquid solvent cement, use a gap filling version of the acrylic solvent cement. This is a thicker version of the popular solvent cement, specifically designed for gaps. Because it's thicker, it will remain suspended in the crack until the cement fuses the plastic together