About Polypropylene|A semi-crystalline thermoplastic with excellent chemical resistance, low density, and good fatigue resistance (living hinges). Cheaper than most engineering plastics. Machines adequately but the low stiffness can cause chattering and deflection. Use sharp tools with high positive rake and support thin sections well. Used for chemical tanks, acid-resistant cabinets, and lab equipment. Compare to
HDPE (similar chemical resistance, tougher) and
Nylon (much stronger and stiffer).