Plastics don't experience crystallization, therefore they contain no phases which may solidify at different temperatures and thus form dendrites. Despite the fact that some plastics like polyethylene may have crystallinity , this not what formed by crystallization like metals. Mainly plastics are not crystalline bodies and therefore can not form dendrites

Hello my friend,

As Dr. Sergei Tarasov said, dendrite is not common in plastics, but today it's possible see it, mainly in polymers used in nanotechnology. They are called dendrimers.

http://www.polymerfactory.com/dendritic-materials/

http://wwwcourses.sens.buffalo.edu/ce435/Dendrimers/Dendrimers

I hope to help you

Best regards.

According to our experience in the behavior of metals solidification, the phenomenon of the dendritic structure only appears in the crystalline structure of metallic materials under specific conditions. In case of polymeric materials, a similar phenomenon called Dendrimer structure occurs in certain specific cases of polymeric materials and this has wide applications in nanotechnology.

Polymers, being amorphous in nature, do not solidify by dendritic growth. Dendrimers are the likely resemblance of dendrites in steel and they only occur when polymers are reinforced with steel powders, especially at nano level. Dendritic growth becomes relatively imminent when the steel reinforcement is in appreciable proportion.

Denderites formation is associated with polycrystalline metallic alloys.

Shivraj Singh Kasana