You’ve probably noticed on most plastic products a recycling symbol with 1, 2, 3, 4, 5, 6 or 7 along with letters. So what are these exactly? The SPI resin identification coding system is a set of symbols placed on plastics to identify the polymer type. The symbols used in the code consist of arrows that cycle clockwise to form a rounded triangle and enclosing a number, often with an acronym representing the plastic below the triangle. Let’s take a look at the 7 plastic identification codes.
Polyethylene Terephthalate (PET or PETE)
Polyethylene Terephthalate (PET or PETE)Description: PET is the most well known member of the polyester family of plastic polymers. It initially gained widespread use as a wrinkle-free fiber (commonly called “polyester”), and the majority of its production still goes toward textile manufacturing. It has become extremely popular for food and drink packaging purposes because of its strong ability to create a liquid and gas barrier – so oxygen cannot get in to spoil food, and the carbon dioxide that makes drinks fizzy cannot get out. Properties: clarity, lightness, strength, toughness, barrier to liquid and gas.
Typical Use: Bottles (water, soft drink, juice, beer, wine, mouthwash, salad dressing), peanut butter/jam jars, oven-ready and microwaveable meal trays, detergent and cleaner containers.
High Density Polyethylene (HDPE)
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. HDPE has long virtually unbranched polymer chains which align and pack easily making it dense and very crystalline (structurally ordered) and thus a stronger, thicker form of of polyethylene. Properties: stiffness, strength, toughness, resistance to moisture, permeability to gas, ease of processing.
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.
Polyvinyl Chloride (V or Vinyl or PVC)
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. 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.
Low density polyethylene (LDPE)
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, resistance 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.
Polypropylene (PP)
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).
Polystyrene (PS)
Polystyrene (PS)Description: PS synthesis requires benzene, a known carcinogen, to form the monomer styrene, which is reasonably anticipated to be a human carcinogen. Apart from low cost, low strength foam, PS can be made as a clear, glassy, hard polymer used for things like cutlery and cd cases; also higher impact versions exist for harder applications. Properties: versatility, clarity, easily formed.
Typical Use: Egg cartons; packing peanuts; disposable cups, plates, trays and cutlery; disposable take-away containers, bike helmets, hangers, smoke detector housing, licence plate frames, medecine bottles, test tubes, petri dishes.
Other (O) – All Other Plastics
Other (O) – All Other PlasticsThis category does not identify one particular plastic resin. It is a general catch-all for all plastics other than those identified by numbers 1-7, and can include plastics that may be layered or a mixture of various plastics. It includes the new bioplastics.
Polycarbonate (PC) is an extremely common plastic in this category and is often associated with this category (sometimes a product will have the number 7 on it with the letters “PC” underneath).
Typical Use: Beverage bottles; baby milk bottles; electronic casing.
