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Plastics are polymers that are made of longchains of repeating molecules. Instead, the plastic isheated and then forced through a die in a lengthwise direction,which causes the polymer's chains to align accordingly. Whenreheated, the polymer tends to soften and get gummy, butdoes not shrink.
Subsequently, one may also ask, does plastic shrink in the cold?
No, plastic expands with heat and contracts withcold. This property is called the coefficient of thermalexpansion. All plastic moves to one degree or another and itis very important to keep in mind when designing parts. Especiallyparts of different materials that have very closetolerances.
Moreover, what happens to plastic when heated?
These types of plastics do not soften whenheat is applied, they do not melt. Once enough heathas been applied the primary bonds between the monomers break whichdestroys the crosslinks between the polymers as well as the polymerchains themselves. The plastic degrades andburns.
Shrinky Dinks and other shrink plastic crafts aresafe because the oven temperatures are low enough thattoxins like dioxin are not released. Dioxins form at very hightemperatures, typically above 700 degrees Fahrenheit. It's truethat the smell of shrink plastic is unpleasant. Unpleasant,but not harmful.