While standard polystyrene is known for being brittle, HIPS Granules (High Impact Polystyrene) are modified with rubber to create a material that can absorb significant energy without breaking. This makes it a perfect candidate for the inner liners of refrigerators, toys, and protective packaging. The rubber particles act as "crack stoppers," preventing small fractures from spreading through the part. However, the orientation of these rubber particles during the injection molding process is critical. If the melt is pushed too hard through a narrow gate, the rubber can become overly stretched, which actually reduces the impact resistance in the direction of the flow.
To get the most out of HIPS Granules, the screw speed should be kept moderate to avoid degrading the rubber component of the alloy. Recent developments in the feedstock industry suggest that improved polymerization techniques are yielding granules with a more uniform rubber distribution, leading to even higher toughness. When the material arrives at the factory, it should be kept in a dry, cool area, although it is much less hygroscopic than polycarbonate. A standard usage step involves a quick pre-heat to 60 degrees to ensure any surface moisture is gone. If the final part shows "pearl-like" white marks when bent, it is a sign that the rubber is working correctly to absorb the stress, proving the material's quality.