2.6 ~ Performance characteristics of biodegradable polymers

Most polymers are produced from

Finite, non-renewable resources such as crude oil. But can be produced from natural and renewable resources such as wood (cellulose), vegetable oils, sugar and starch, therefore saving finite resources

What are polymers a major cause for?

Discarded polymers are a main cause of pollution and can kill marine and bird life, as well as cause environmental scarring due to landfill

Two main categories of biopolymers

Natural polymers and Synthetic bio polymers

Natural bio polymers

Made from natural materials such as cellulose, starch, and polysaccharides

Synthetic bio polymers

Made from renewable resources but chemically engineered (synthesised) to break down more quickly

Biodegradable polymer

Can be made from finite resources such as crude oil and contains additives that cause it to degrade more quickly than traditional polymers

Implications of using bio polymers and biodegradable polymers

Biodegradable polymers produce methane gas when they decompose in landfill. Methane gas is a greenhouse gas that contributes to global warming. Biodegradable polymers can take high temps to decompose and may leave toxic residue. Natural biopolymers need land to grow crops to make them, including genetically modified crops. Biopolymers and biodegradable polymers can't be recycled. Their use may not encourage people to recycle and may contribute to throw away culture Bio polymers and biodegradable polymers can be processed same way as thermoplastics eg injection moulded, blow moulded, calenderd, vacuum formingBio polymer and biodegradable polymer different meaning which can be confusing making it harder to make positive environmental choice when shoppingAdditives can be added to any thermoplastic and are often used in LDPE, HDPE,PP, PVC AND PET

Biodegradable and bio polymers example

Corn starch polymer Potatopak Biopol (PHB)Polylactic acid (PLA)Polyhydroxyalkanoate (PHA)Lactide Glycolide (Lactel and Ecofilm)

Corn starch polymer (type and source)

Natural biopolymer made from high starch vegetables like corn, potatoes and maize

Corn starch polymer uses

Packaging products Straws Vending cups, disposable cutlery Bags Takeaway food containers

Potatopak (type and source)

Natural biopolymer made from potato starch

Potatopak uses

Single-use food items such as bowls, cutlery, food trays, serviettes. Packaging peanuts bin bags

Biopol (bio batch additive) (trade name for polyhydroxybutyrate PHB)(type and source)

Natural biopolymer made from bacteria grown in cultures. Additive to promote degradation; usually 1% added to thermoplastics

Biopol (bio batch additive) (trade name for polyhydroxybutyrate PHB)( uses )

Packaging products such as film, carrier bags, vending cups nappies, surgical stitches, pill coverings

Polylactic acid (PLA) (type and source)

Synthetic biopolymer made from corn kernels or cane sugar, fermented to produce lactic acid, then synthesised to produce polylactic acid

Polylactic acid (PLA) (uses)

Packaging, single-use bottles, carrier bags, plant pots, Disposable nappies, Medical sutures, 3D printing

Polyhydroxyalkanoate (PHA) (type and source)

Natural biopolymer made from bacteria grown in cultures; fully compostable

Polyhydroxyalkanoate (PHA) (use)

Packaging; medical uses such as slow-release medication patches Films Screws and bone plates

Lactide (type and source)

Synthetic biopolymer, fully compostable, water-soluble PLA and cellulose-based

Lactide (uses)

Biomedical applicationsSlow release medicationBone repair fixings Detergent washing sachets

Glycolide (lactel and ecofilm) (type and source)

Synthetic biopolymer, fully compostable PLA and cellulose-based

Glycolide (lactel and ecofilm) (uses)

Food film, bags, packaging wrap Bin bags, agricultural ground sheet, flower wrap

How long can polymers be designed to degrade?

From months to a couple of years

Degradation occurs in the presence of:

light (photodegradable) - polymer bonds are weakened, and the polymer breaks down with exposure to ultraviolet (UV) light such as UV rays from sunlight; oxygen - polymer turns into a fine powder with exposure to oxygen and is subsequently degraded by the action of microorganisms; water - polymer quickly breaks down with the exposure to water and is subsequently degraded by the action of microorganisms

Degradation occurs

As the action of microorganisms, which convert the material into water, carbon dioxide, biomass and possibly methane

What is the ability of the polymer to biodegrade dependent on?

The structure of the polymer rather than the origin of the raw material