What are the differences in chemical resistance between injection and rotational molds?
The chemical resistance of molded plastic parts depends significantly on the manufacturing process used. Injection molding and rotational molding produce components with distinct chemical resistance properties due to differences in material processing, wall thickness, and structural integrity.
Injection molding creates parts with excellent chemical resistance due to high-density molecular structure and minimal porosity. The high-pressure process forces molten thermoplastic into molds, resulting in uniform, non-porous surfaces that effectively resist chemical penetration. Materials like polypropylene, PVC, and engineered thermoplastics maintain their inherent chemical resistance properties through this process. The consistent wall thickness and dense structure provide reliable barrier protection against acids, solvents, and hydrocarbons.
Rotational molding produces parts with varying chemical resistance characteristics. The process involves heating plastic powder in a rotating mold, creating a more porous structure compared to injection molding. While rotationally molded polyethylene offers good chemical resistance, the process can create microscopic pores that potentially allow chemical penetration. The thicker walls typical of rotational molding provide additional chemical barrier protection, but internal stress points from cooling may create vulnerability areas.
Key factors affecting chemical resistance include material selection (polyethylene vs. polypropylene), wall thickness consistency, part design complexity, and post-molding treatments. Injection molding generally provides superior chemical resistance for applications requiring precision and consistent protection, while rotational molding offers adequate chemical resistance for larger, more durable containers and tanks where some permeability may be acceptable.
Understanding these differences helps manufacturers select the appropriate molding process for chemical exposure applications, ensuring product longevity and safety in corrosive environments.
