Solvent cement

Solvent cement joins a specific thermoplastic by softening or partly dissolving its surface. Many formulas also carry dissolved resin. When the parts are pressed together, softened material from both faces mingles. The solvents then leave and the joint hardens. This is closer to welding plastic than filling a gap with a separate universal glue. The useful consequence is strict material matching. PVC pipe cement, ABS cement and acrylic sheet cement are not interchangeable. A cement that works on rigid PVC may craze acrylic or do almost nothing to polyethylene. The joint should fit properly before cement is applied. Large gaps leave a solvent-rich, weak mass and slow the final strength build. Work quickly because the open time can be only a few minutes. Hold or clamp until the parts cannot move, then allow the maker's stated cure before pressure testing, machining or loading. Solvent cement is the right choice for compatible rigid plastic pipe and fittings, acrylic display work and some fabricated plastic housings. It is the wrong choice for unknown plastics, flexible vinyl, stressed polycarbonate without testing, or repairs where trapped solvent cannot escape. Pipe systems also have standards for primer, temperature, pipe size and cure before pressure service. Follow the pipe and cement maker together.

Joining matched PVC, CPVC or ABS pipe systems with the specified cement; edge and face joints in acrylic sheet; rigid plastic signs, display cases, housings and models where the cement explicitly lists the plastic.

Identify the plastic first. Dry-fit the parts and correct the fit before opening the cement. Remove swarf, grease and dust. For pipe, cut square, deburr, chamfer and use the specified cleaner or primer. Apply the stated amount, assemble while both faces are wet and hold against push-out. For sheet, avoid flame-polished or highly stressed edges unless the maker permits them.