Plastic Caps & Closures Wholesale Suppliers

Plastic cap materials, thread standards, and liner types

Plastic screw caps and closures are produced predominantly in polypropylene (PP) and high-density polyethylene (HDPE) — the two materials covering the vast majority of food, beverage, household, and personal care packaging closure applications. PP closures are more rigid, better tolerating higher heat applications (hot-fill beverages, heat-sterilised products), and available in a wider colour range. HDPE closures are slightly more flexible and impact-resistant, widely used for household chemical and personal care applications. Key cap specification parameters are: finish/neck diameter and thread standard — the most important parameter for fitment compatibility. Common standards are PCO 1810 and PCO 1881 (carbonated beverage PET bottle caps, 28mm thread), 28mm 400 and 28mm 410 (common food and beverage standards), 38mm and 43mm (wide-mouth jar caps), and DN25/DN32/DN38 ROPP standards for aluminium ropp closures. Cap liners provide the sealing function between the cap and the bottle or jar rim. Liner types include: foam (PE foam, the most common general-purpose liner for non-carbonated beverage and food products), induction seals (a foil-foam-polymer laminate liner that is bonded to the bottle rim by electromagnetic induction after filling — providing a hermetic seal and tamper evidence), EPE (expanded polyethylene foam with a PE facing — for carbonated beverages and oxygen-sensitive products), and full-lining for chemical resistance in agrochemical and household chemical products.