Plastic
Plastic can be one of the most confusing materials to identify for recycling.
Essentially, most thermoplastics (which are flexible and are typically containers for packaging consumer goods like drink bottles) can and should be recycled. Thermoplastics have recycling codes on them that indicate what type of resin they are made from and guide whether they are recyclable or not.
On the other hand, thermosets (which are set like concrete and are typically components of products like TV monitors), should be recycled but are very hard to recycle.
Not all councils or recyclers accept all these plastics, therefore it is important to double check what is acceptable in your council region. Numbers 3 to 7 tend to be rejected as they are less popular and harder to make into new products. The exception is number 5, which is becoming increasingly popular and more recyclable across council regions.
PLA is a compostable plastic alternative made from plant resources and not petrochemicals. Because of its plant composition it cannot be disposed in traditional recyclable plastics. It has the potential of being disposed in commercial composting facilities, where the perfect environment allows for material breakdown.
More information on the different plastics can be found below.
What are thermoplastics?
Thermoplastics are permanently fusible and can be melted down and recycled.
The reason why thermoplastics melt down so easily is because the molecules have a relatively weak attraction between the chains of molecules. Thermoplastic resins have molecules that are generally not cross-linked, meaning, the resin can be repeatedly melted and reused. Usually, no chemical change occurs when thermoplastic is cured. Thermoplastic resin usually starts out in solid pellet form, and changes shape with the addition of heat and pressure.
Thermoplastic polymers are more widely used because of their flexibility, so there are, therefore, more of them. Thermoplastic polymers are known as acrylics (Polymethyl methacrylate), fluorocarbons (PTFE or TFE), nylons, polycarbonates, polyethylene, polypropylene, polystyrene, vinyls and polyester.
Pros:
- High Impact Strength
- Attractive Surface Finish
- Recyclable / Scrap is Reusable
- No Emissions
- Can bond to other thermoplastics
- Can be molded or shaped with reheat
Cons:
- Generally softens with heat
- More difficult to prototype
Common Types of Thermoplastics Resins:
- Polyamide (PA or Nylon)
- Polybutylene terephthalate (PBT)
- Polyethylene terephthalate (PET) as Polyester.
- Polycarbonate (PC)
- Polyethylene (PE)
- Polypropylene (PP)
- Polyvinyl chloride (PVC)
What are thermoset plastics?
Thermosets are cured and will only char and break down.
Thermoset molecules are formed by cross-linked chains of molecules further strengthened by chemical bonds. A thermoset is essentially one large molecule, without a crystalline structure. Thermoset resins generally come in liquid form, and when mixed with a catalyst, a chemical reaction occurs forming a solid. Thermoset molecules crosslink with each other during curing, thus once cured, they cannot change.
Thermoset polymers do not equal thermoplastic polymers in quantity, but they remain present within the manufacturing market. Thermoset polymers are known as epoxies, polyesters, silicones and phenolics.
Pros:
- Easy to process and laminate
- Does not necessarily need pressure or heat to form
- Generally inexpensive
- Generally stronger than thermoplastics
- Generally better suited to higher temperatures then thermoplastics
Cons:
- Often release emissions known as volatile organic compounds (VOCs)
- Cannot be recycled or reclaimed easily
- Short workable pot life, with some exceptions
- Less-than-perfect surface finish
Common Types of Thermoset Resins:
- Epoxy
- Polyester (Not PET) Vinylester
- Polyurethane
- Phenolic
Plastic Recycling
Numerical Code - 1
Plastic Composition - Polyethylene Terephthalate (PET)
Properties - Clear and optically smooth, resists water, oxygen and CO2, resists high impacts, resists most solvents, can be filled with hot liquids.
Typical Applications - Soft Drinks Bottles, Sports Bottles, Condiment/Food Jars, Food Trays.
Products Made with Recycled Content- New Containers, Strapping, Carpet Fibres, Cushion/Jacket Filling.
Numerical Code - 2
Plastic Composition - High-Density Polyethylene (HDPE)
Properties - Resists most solvents, high strength characteristics, stiff material.
Typical Applications - Water Bottles, Milk Bottles, Cleaning Products, Personal Cosmetics.
Products Made with Recycled Content - New Containers, Piping, Edging, Bins.
Numerical Code - 3
Plastic Composition - Poly Vinyl Chloride (PVC)
Properties - High impact and strength, resists grease and chemicals.
Typical Applications - Packaging/Wraps, Plumbing Pipes, Flexible Packaging/Bags.
Products Made with Recycled Content - New Piping, Carpet Backing, Packaging, Traffic Cones.
Numerical Code - 4
Plastic Composition - Low-Density Polyethylene (LDPE)
Properties - Resists acids and oils, tough, flexible and transparency is good.
Typical Applications - Film and Stretch Wrap.
Products Made with Recycled Content- Rubbish Bin Liners, Floor Tiles, Compost Bins, Outdoor Furniture.
Numerical Code - 5
Plastic Composition - Polypropylene (PP)
Properties - Great optical clarity, low moisture vapor penetration, inert towards acids, alkalis and most solvents.
Typical Applications - Hard Containers, Medicine Bottles, Takeaway Containers, Bottle Caps, Refrigerated Food Containers.
Products Made with Recycled Content - Automotive Products, Household Tools/Utensils, Outdoor Tools, Trays.
Numerical Code - 6 PS
Plastic Composition - Polystyrene (PS)
Properties - Great short shelf life moisture barrier, high optical clarity, good rigid structure, light yet stiff, low thermal conductivity.
Typical Applications - Plastic Plates/Cutlery, Food Containers, CD Cases, Small Hard-wearing Bottles, Cable Spools, Toys.
Products Made with Recycled Content - Light Switches, Plastic Mouldings, Packaging, Desk Trays.
Numerical Code - 6 EPS
Plastic Composition - Expanded Polystyrene (EPS)
Properties - Great short shelf life moisture barrier, low thermal conductivity, can absorb knocks.
Typical Applications - Styrofoam Cups, Food Trays, Protective Foam Packaging.
Products Made with Recycled Content - Light Switches, Plastic Mouldings, Packaging, Desk Trays.
Numerical Code - 7 Composite
Plastic Composition - Composite (other)
Properties - Dependent on resins and combination of resins.
Typical Applications - Milk/Fruit Juice Cartons, Oven Bags.
Products Made with Recycled Content - Low Grade Bottles and Outdoor Goods.
