What is the difference between PVC, PE and PP and when do you use these specific plastics?
3. Polyvinyl chloride (V or Vinyl or PVC)
Description: Long the second most widely used plastic resin in the world (after polyethylene), PVC (or vinyl) use has decreased because of serious health and environmental pollution issues associated with its manufacture, use and disposal - it's whole life cycle is toxic. But it is still popular and in common use because of its cost-effective versatility.
The base monomer is vinyl chloride - the presence of chlorine is the cause of many of PVC's problems - which can be combined and blended with numerous chemicals (including plasticizers such as phthalates) to create resins with properties ranging from rigid to filmy to soft to leathery. Properties: versatility, ease of blending, strength, toughness, clarity, transparency.
Typical Use: Soft PVC (softened with plasticizers) used in toys, clear food (e.g., take-out) and non-food packaging (e.g., blister wrap, cling wrap), squeeze bottles, shampoo bottles, mouthwash bottles, cooking oil and peanut butter jars, detergent and window cleaner bottles, loose-leaf binders, shower curtains, blood bags and medical tubing, "pleather" clothing, Naugahyde upholstery, wire and cable insulation, carpet backing and flooring. Rigid PVC used for blister packs and clamshell packaging, credit cards, piping (e.g., for plumbing), vinyl siding, window frames, fencing, decking, and other construction materials.
Toxicity: PVC is widely considered the most toxic and hazardous plastic that is still - unbelievably so - commonly used to make numerous consumer products. It may contain and/or leach a variety of toxic chemicals including, but not limited to: bisphenol A (BPA), phthalates, lead, dioxins, mercury, and cadmium. Here is a taste of the toxic life cycle of PVC:
• The vinyl chloride monomer from which PVC is made is a known carcinogen, thus putting manufacturing workers and surrounding communities at risk.
• Soft forms of PVC, such as toys and packaging and bottles, may leach phthalates. For example, di(2-ethylhexyl) phthalate (DEHP) and butyl benzyl phthalate (BBzP) are two phthalates commonly used as plasticizers or softening agents (usually DEHP). DEHP and BBzP are endocrine disruptors mimicking the female hormone estrogen and have been strongly linked to asthma and allergic symptoms in children living in homes where PVC dust was present and to ADHD in children; may cause certain types of cancer, including breast cancer. Recent consumer product legislation in Europe, Canada and the US, bans DEHP and BBzP and other dangerous phthalates from use in children's products in concentrations greater than 0.1%
• When PVC is burned (e.g., via waste incineration, car or home fires), dioxins are formed. Dioxins are known human carcinogens and persistent organic pollutants, and are considered one of the most toxic types of chemicals ever tested.
Recycling Rate: Very low. Rarely recycled because it is difficult to do so on an industrial scale. It should not be recycled because it contaminates the recycling stream. Recycled PVC can become packaging, binders, decking, paneling, insulation, mud flaps, film and sheet, flooring, garden hoses.
Polyethylene (PE)…there are many types of polyethylene (I've described 2 below)…
2. High density polyethylene (HDPE)
Description: Polyethylenes are the most widely used family of plastics in the world. The versatile polyethylene polymer has the simplest basic chemical structure of any plastic polymer (repeating units of CH2: one carbon and two hydrogen molecules) making it very easy to process and thus extremely popular for numerous low value applications - especially packaging.
Typical Use: Plastic bags (grocery), opaque milk, water, and juice containers, bleach, detergent and shampoo bottles, garbage bags, dishes, yogurt and margarine tubs, cereal box liners, some medecine bottles. Also used in Tyvek insulation, PEX piping, plastic/wood composites.
Toxicity: Being relatively stable, it is generally considered a safer plastic for food and drink use, although some studies have shown that it can leach the endocrine disruptor nonylphenol (added to HDPE as a stabilizer), especially when exposed to ultraviolet light - i.e., sunlight - and possibly other additive chemicals with estrogen-mimicking activity.
Recycling: About 29%. Recycled material made into bottles for non-food items like shampoo, laundry detergent, motor oil; plastic lumber and furniture, piping, recycling bins, fencing, floor tiles, buckets, crates, flower pots, garden edging, film and sheeting.
4. Low density polyethylene (LDPE)
Description: LDPE polymers have significant chain branching including long side chains making it less dense and less crystalline (structurally ordered) and thus a generally thinner more flexible form of of polyethylene. Properties: strength, toughness, flexibility, resist
ance to moisture, ease of sealing, ease of processing.
Typical Use: Mostly for film applications like bags (grocery, dry cleaning, bread, frozen food bags, newspapers, garbage), plastic wraps; coatings for paper milk cartons and hot & cold beverage cups; some squeezable bottles (honey, mustard), food storage containers, container lids. Also used for wire and cable covering.
Toxicity: see HDPE
Recycling Rate: Low. Difficult to recycle. Recycled material can be made into compost bins, paneling, plastic lumber.
5. Polypropylene (PP)
Description: Polypropylene is used for similar applications as polyethylenes, but is generally stiffer and more heat resistant - so is often used for containers filled with hot food. It too has a simple chemical structure (many methyl groups of CH3 - one carbon and three hydrogen molecules) making it very versatile. It's crystallinity (structural order affecting hardness & density) is quite high, somewhere between LDPE and HDPE. Properties: strength, toughness, resistance to heat, chemicals, grease & oil, barrier to moisture.
Typical Use: Food containers (ketchup, yogurt, cottage cheese, margarine, syrup, take-out), medicine containers, straws, bottle caps, Britta filters, Rubbermaid and other opaque plastic containers, including baby bottles. Other uses include disposable diaper and sanitary pad liners, thermal vests, appliance parts and numerous car parts (bumpers, carpets, fixtures).
Toxicity: Being relatively stable, it is generally considered a safer plastic for food and drink use, although it has been shown to leach plastic additives (such as the stabilizing agent oleamide) when PP labware was used in scientific experiments and one older study has suggested heated PP may be linked to occupational asthma based on the exposure of a worker in a PP factory.
Recycling Rate: Low, because often pigmented or mixed with other resins, therefore difficult to sort. Recycled material made into brooms, brushes, bins pallets, auto battery cases, flower pots.
