Biodegradable Polymers Flashcards
Biodegradable polymers
Can be made from finite resources such as crude oil but contain additives that cause it to degrade more quickly than traditional polymers
Natural bio-polymers
Polymers made from natural materials such as cellulose, starch and polysaccharides
Synthetic bio-polymers
Polymers made renewable resources but chemically engineered to break down more quickly
Implications of bio-polymers and biodegradable polymers
Can produce methane (greenhouse gas)when they decompose
Biodegradable polymers can take high temperatures to decompose and may leave behind toxic residues
Natural bio-polymers are made from crops and GM crops so require land
Can’t be recycled - discourages people to recycle and contributes to a throwaway culture
Can be processed the same way as thermoplastics - injection moulding, calendaring, vacuum formed and blow moulded
Can have additives added
Similar names of bio-polymers and biodegradable polymers may confuse people
Reduce the demand for oil based polymers
Corn starch polymer
Natural Bio-polymer
Made with high-starch vegetables such as corn, maize and potatoes
Uses:
Packaging Straws Vending cups Disposable cutlery Bags Takeaway food containers
Potatopak
Natural Bio-polymer
Made from potato starch
Cradle-to-cradle approach
Non-toxic, edible, biodegradable
Produces no toxic waste, but the small amounts of solid waste can be used to feed animals
Can be composted - will break down within 4 weeks
Uses:
Single use food items - bowls, cutlery, food trays, serviettes - can be easily formed into this shape using a heated compression mould
Packaging beads (aka peanuts)
Bin bags
Biopol (polyhydroxybutyrate (PHB))
Natural Bio-polymer
Made from bacteria grown in cultures - fermentation of carbohydrates from peas and sweet potatoes
Additive to promote degradation - usually 1% added to thermoplastic (BIO-BATCH ADDITIVE)
Can be composted
Uses:
Packaging film Carrier bags Vending cups Nappies Surgical stitches Pill coverings
Polylactic acid (PLA)
Synthetic bio-polymer
Made from corn kernels or can sugar, fermented to produce lactic acid and then synthesised to produce polylactic acid
Uses:
Single use bottles Carrier bags Plant pots Disposable nappies Medical sutures 3D printing
Polyhydroxyalkanoate (PHA)
Natural bio-polymer
Made from bacteria grown in cultures
Fully compostable
Uses:
Packaging
Medical uses - slow release medication patches, screws and bone plates
Lactide
Synthetic bio-polymer
Fully compostable, water soluble
PLA and cellulose based
Uses:
Biomedical applications
Slow-release medication
Bone repair fixings
Detergents washing sachets
Glycolide (Lactel and Ecofilm)
Synthetic bio-polymer
Fully compostable, water soluble
PLA and cellulose based
Uses:
Food film Bags Packaging wrap Bin bags Agricultural ground sheet Flower wrap
Photodegradable
Polymer bonds are weakened and the polymer breaks down with exposure to UV light such as sunlight
Oxy-degradable
Polymer turns into a fine powder with exposure to oxygen and is subsequently degraded by the action of microorganisms
Hydro-degradable
Polymer quickly breaks down with exposure to water and is subsequently degraded by the action of microorganisms
Degradation by microorganisms
Convert the material into water, carbon dioxide, biomass and methane
The ability of a polymer to biodegrade is dependent on the structure rather than the origin of e raw material
Biodegradable polymer examples
Corn starch polymer
Potatopak
Biopol (polyhydroxybutyrate (PHB))
Polyhydroxyalkanoate (PHA)
Lactide
Glycolide (Lactel and Ecofilm)
PLA
How is Potatopak produced?
The waste water from the processing of potatoes for the production of chips and crisps etc contains starch
This water is fed through a starch extractor
Water can be reused and the dried starch can be processed by a high-speed pressure thermoforming machine that inserts powdered starch onto moulds
The starch is pressurised and ‘cooked’ into a rigid durable shape
Properties of PLA/corn starch polymer
Food safe
UV resistant
Good aroma barrier
Low flammability
Compostable
Issues with PLA/corn starch polymer
Can’t be recycled
Without enough oxygen and light PLA won’t decompose for decades
PHA/PHB closed loop carbon cycle
The quantity of CO2 produced in the biomass process is the same as that absorbed by the corn - carbon neutral
Bacteria is encouraged to grow
Nitrogen deficiency develops
Bacteria absorbs carbon as a copolymer
Processed into PHA/PHB and then into products
End of useful life - degrades harmlessly in soil
Properties of Biopol (PHB) and PHA
Insoluble in water and will sink
Similar tensile strength to PP
High melting point - 175 degrees C
More expensive and more time consuming to produce than traditional polymers
Low resistance to acids and alkalis
Low impact resistance
Potatopak properties
Edible
Non-toxic and food safe
Able to be composted - will break down in 4 weeks
Cradle-to-cradle approach
Small amount of solid waste produced can be used to feed pigs
Produces no harmful gases in its production
Negatives of potatopak
Still ongoing research into finding a suitable sustainable surface coating for protection of the starch
Starch can break down on exposure to hot liquids and some foods such as raw meats
