OAK BROOK, ILL. — An Association of Rotational Molders study has found that regrind from rotational molded parts can be added to injection molding resins and can improve some mechanical properties of those parts.
The comprehensive study examined cross-linked regrind flake and chips and powder from rotomolded scrap for its ability to be injection molded. Regrind content varied from 15-75 percent.
The study found:
Depending on the base polyethylene, shrinkage decreased as recycled content increased.
High density PE had a decrease in tensile modulus but an increase in flex modulus of almost one-third. Linear medium density PE had a significant increase in tensile and flexural moduli.
Izod impact strength improved 10-30 times with 50 percent HDPE flake; with LMDPE there were no breaks.
Elongation at yield did not change significantly with HDPE scrap, but decreased sharply with at least 15 percent LMDPE regrind. Ultimate elongation did not change in HDPE, and it decreased slowly with increasing amounts of LMDPE.
The 68-page study can be purchased from Oak Brook-based ARM for $25 by calling (630) 571-0611.