Polypropylene’s common uses are packaging, household goods, car parts, building products, electrical parts, pipes and tanks, fibers and nonwoven fabrics, and medical and lab products. It covers that many uses because it is light, resists water and most chemicals, and can be made into film, molded parts, fiber and pipe.
In OECD’s figures on plastics use in 2019, packaging took about half of the polypropylene that did not go into fibers, ahead of consumer and institutional products and transport. Those figures count fiber as a separate category and do not list medical products as a sector, so fiber and medical uses are not ranked against the rest, although a large share of polypropylene is melt-spun into fiber.
Of the three types of polypropylene, homopolymer is the most widely used and turns up in nearly every sector. The copolymers have narrower uses. Impact copolymer is used for parts that must take knocks in the cold, such as bumpers and appliance parts, and random copolymer for clear packaging and hot- and cold-water pipe.
Two of polypropylene’s weaknesses limit where it goes as supplied: unmodified homopolymer turns brittle in the cold, and any grade degrades in sunlight unless it carries UV stabilizers. Parts that need more stiffness or heat resistance than polypropylene gives are usually made from engineering plastics such as nylon, though talc- and glass-filled polypropylene compounds are used for some of them.
Packaging
Packaging uses polypropylene as film for flexible packs and as rigid containers, cups and closures molded or thermoformed from the resin.
Flexible Packaging
Flexible polypropylene packaging is mostly BOPP or CPP film. BOPP is the stiff film of snack and confectionery bags, labels, clear overwrap and packaging tape. CPP is used for garment bags and as the sealing layer inside laminated pouches.
The sealing layer is usually a random copolymer or a terpolymer.
Rigid Packaging
Rigid polypropylene packaging is injection molded into thin-wall tubs, cups and lids for dairy and takeaway food, and into caps and closures. It is also thermoformed into cups and trays and blow-molded into bottles for food, shampoo and household liquids.
Thin-wall containers are molded from high-flow homopolymer or impact copolymer grades, and clear tubs and cups from random copolymer with a clarifier.
Polypropylene is the usual material for microwavable and hot-filled food containers.
Household and Consumer Goods
Household and consumer goods made from polypropylene include storage boxes and bins, kitchenware and dishwasher-safe food containers, toys, outdoor furniture, luggage, folders and binders, and appliance parts such as washing-machine tubs and small-appliance housings.
Items that get dropped or knocked, such as bins and appliance parts, are usually molded from an impact copolymer.
Automotive Parts
In a car, polypropylene is in the bumpers, instrument panel, door and pillar trim, console, airbag housings, battery case and energy-absorbing foam.
Bumpers and instrument panels are molded from impact copolymer grades, usually compounded with talc and an elastomer.
Building and Construction
Polypropylene goes into house wraps and air and moisture barrier membranes, roofing underlayment and single-ply roofing membranes, siding, drainage mats for green roofs, carpet, and fibers mixed into concrete to reduce cracking while it sets.
Electrical and Electronic Uses
Electrical and electronic uses of polypropylene include the dielectric film of film capacitors, the separator film in some lithium-ion batteries, the case of lead-acid batteries, and the insulation or filler in some cables.
Capacitor film is stretched from homopolymer grades with very low ash content.
Pipes, Tanks and Industrial Equipment
Polypropylene pipe carries hot and cold drinking water, heating water and chilled water inside buildings, and industrial process fluids, effluents and sewage. Polypropylene sheet is welded into chemical storage tanks, plating tanks, fume ducting and scrubbers, and the resin is molded into filter-press plates.
Pressure pipe for hot and cold water and heating is extruded from random copolymer, PP-R, or from PP-RCT, a random copolymer that holds its strength at higher temperatures. Cold-water and drainage pipe can also be made from impact (block) copolymer.
Fibers and Textiles
Polypropylene fiber goes into woven sacks and bulk bags, nonwoven fabrics, carpet, rope and twine, upholstery and, in small amounts, clothing.
Woven Bags and FIBC
Woven polypropylene sacks carry cement, fertilizer, animal feed, grain, sugar and chemicals, and FIBC bulk bags carry the same kinds of powders and granules in much larger loads. Both are woven from slit, stretched polypropylene tape extruded from homopolymer raffia grades.
Nonwoven Fabrics
Polypropylene nonwovens go into diapers and feminine hygiene products, surgical gowns and drapes, face masks, filters, crop covers, geotextiles, and furniture and bedding.
Most of these fabrics are spunbond, meltblown or a laminate of the two (SMS). Spunbond is spun from homopolymer fiber grades, and meltblown from grades of much higher melt flow.
Carpet, Rope and Apparel Fibers
Carpet makers use polypropylene as bulked continuous filament (BCF) face yarn, especially for low-cost and indoor-outdoor carpets and rugs, and as woven carpet backing. Rope, twine and netting are made from its monofilament and tape.
Carpet yarn is spun from homopolymer BCF grades, and rope and backing from tape and monofilament grades.
In clothing, polypropylene is a minor fiber, used mainly in thermal underwear, sports base layers and socks.
Medical and Laboratory Products
Hospitals and labs use polypropylene for disposable syringes, specimen containers, centrifuge and sample tubes, pipette tips, sutures and hernia mesh, and nonwoven gowns, drapes and masks.
Devices sterilized by gamma radiation are molded from radiation-stabilized grades.