Material Choice: TPE VS TPU for Injection Molding

[PATERLEY]

Hello All,

First post here. I have a quandary that I would love some input on.

A little background: About 4 months ago I designed a new sink strainer that I have started the process to manufacture here in the US. At the time, I felt 75 Shore A TPE (unisoft) would be the best option in terms of flexibility and durability. The strainer is slightly larger than the drain opening, and it compresses and countersinks into the opening below the surface. I did not consider LSR at the time, and from what I understand the mold would not be compatible for LSR (correct?) due to shrinkage, flash, etc.. The mold is almost finished per TPE spec, and I am starting to have second thoughts on TPE, and wondering if TPU might be a better option. The things I care most about are:

1. Durability
2. Compression set (boiling water is the upper end here)
3. Household chemical resistance
4. Color fade
5. Low "tackiness" so food does not stick (if that makes sense)

Basically, I want this strainer to be durable against boiling water, food scraps, dishwasher use, being inverted to empty, etc for at least 2-3 years. Average material thickness is about 80 thou.

I know TPU forms an actual cross-linked bond and changes its make-up, making it stiffer and perhaps more durable? Do you think TPE is an appropriate material for the job? I have urethane molded samples that are holding up well, with some color fade.

I have reached out to materials suppliers and they are not super excited to talk to me about the matter.

I really appreciate all of your input.

Cheers,
Pat E

 

[PATERLEY]

This should probably be in plastics engineering instead. Apologies. I am not sure how to move it...

 

[btrueblood]

TPEs are typically fairly durable stuff, and (depending on formulation) may react less with chemicals than urethanes. You really need to dig into details to see what the individual formulations can do. Hytrel and Santoprene both have some of the chemical and thermal durability of molded EPDM, with hytrel having really good tear strength (they make fire hose linings from the stuff).