What Type of Caulk Adheres Best to Plastic?

It's important to know which materials work best for which jobs when starting home improvement or other DIY projects. Using the right kind of caulk for your plastic will determine the longevity, security, and appearance of the seal. Choose your caulk type based on the conditions the seal will be under, such as exposure to moisture, light and heat, and whether the seal will be visible or concealed.

Silicone caulk dries quickly and is a top choice for creating a seal between plastic surfaces. Silicone holds up when exposed to water or high humidity and is a good insulator. However, silicone caulk cannot be painted, and silicone can attract dirt if used on an exposed surface. Silicone is also one of the more expensive caulk options.

A silicone-polyurethane blend gives the flexibility of silicone with the longevity and strength of polyurethane. Polyurethane on its own will eventually erode plastic but, when blended with silicone, will greatly increase the lifespan and durability of the seal.

Acrylic latex caulk is best for many home repairs and is safe to use on plastic. When cured, latex acrylic caulk can last as long as 15 years. It can be used in high-humidity areas, such as plumbing fixtures, and is known for its flexibility. Latex acrylic caulk can also be painted with latex-based paint.

Synthetic rubber caulk can be used to join just about any two surfaces. Synthetic rubber withstands a great deal of pulling and stretching and regains its shape well. Synthetic rubber caulk can be painted with water-based paint. The downside of this caulk is that it is flammable until it cures completely and shrinks significantly after curing. Synthetic rubber caulks can contain high levels of volatile organic compounds (VOCs), so they should be used only in outdoor applications.