Polyethylene sinks are a great product for several reasons.
First, polyethylene has great thermal shock resistance. Many labs use dry ice for various purposes in their sinks. Polyethylene when exposed to dry ice will not stress or crack; like a more rigid material such as epoxy which will crack under the stress of super cooling.
Second, the waste outlet in a polyethylene sink can be molded into the part. This eliminates the need for a separate waste. This also allows for complete drainage so no chemical residue will be present.
Last but certainly not least, polyethylene sinks are lighter than metal sinks and much lighter than epoxy sinks. This saves on shipping costs to the job site.
For a complete line of Polyethylene Sinks check out Scientific Plastics.