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Gluing plastic can be difficult because of the smooth surface of the material. The best results will come from the use of the appropriate glue and proper surface preparation. Hobby and craft glues should be labeled for use on plastic to avoid surface damage. Before gluing plastic, always test fit the pieces first to ensure that they fit together well. Adhesives also work best when they are used at room temperature.
Plastic materials that have smooth or glossy surfaces should be cleaned before any glue is applied. Cleaning the surface does not need to be difficult; only water and a mild detergent are required. Dry the pieces with a soft cloth, and remove any lint before gluing the material together. If machining oils remain on the plastic, the materials will not hold together well.
With some plastics, the surface might need to be roughened slightly with fine-grade sandpaper. Plastic materials that have rough surfaces will hold adhesives with less difficulty. Clean away any residue before gluing. When gluing plastic joints, creating a beveled or slightly rounded edge will improve the final bond strength.
When working with soft plastics, polystyrene cement is a good choice of adhesive. For hard plastic materials, polystyrene cement or cyanoacrylate can be used. Cyanoacrylate, also known as instant glue, might not be recommended for use on softer plastics because it might cause melting. Polypropylene and acrylics require specific glue to create a strong adhesive bond. Acrylic cements are solvents that actually fuse the pieces together.
Polyvinyl chloride (PVC) materials require the use of special adhesives. When working with PVC pipe, the contact surfaces must be roughened and cleaned well before the PVC glue is applied. Using a designated PVC cleaner/primer will provide the best results. PVC glue also is a form of solvent for chemical welding, and it should be used with care.
When gluing plastic, be sure to allow the pieces to dry, undisturbed, for as long as the manufacturer recommends. Assembled pieces can be held together with clamps, tape or rubber bands. Flat plastic objects can be weighted down with books.
Always read the label on any adhesives, and follow all safety instructions. Non-toxic cements are available that offer the same durability of regular glues. Plastic glue should be used in a well-ventilated area. Gloves also should be used to keep adhesives off fingers or hands. A solution of mild liquid soap, water and vinegar can be used as a soak to remove most adhesives from the skin.