9-biodegradable polymers

• Biodegradable polymers


  Polymers that can be broken down by the action of microorganisms
• Characteristics of biodegradable polymers

  • Most polymers are produced from finite, non-renewable resources such as crude oil which take hundreds of years to break down
  • Discarded polymers are a major cause of pollution and can kill marine and bird life, as well as cause environmental scaming due to landfil
  • Polymers can be produced from natural and renewable resources such as wood (cellulose), vegetable oils, sugar and starch, therefore saving finite resources
• Bio-polymers categories


  • 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)
• Implications of the use of bio-polymers and biodegradable polymers

  • Biodegradable polymers can produce methane gas when they decompose in landfil, which is a greenhouse gas that contributes to global warming
  • Biodegradable polymers can take high temperatures to decompose and may leave behind toxic residues
  • Natural bio-polymers need land to grow the crops to make them, including genetically modified (GM) crops
  • Bio-polymers and biodegradable polymers cannot be recycled. Their use may not encourage people to recycle and may contribute to a 'throwaway' culture
  • Bio-polymers and biodegradable polymers can be processed in the same way as thermoplastics-for example, injection moulded, blow moulded, calendared and vacuum formed
  • The terms 'bio-polymer' and 'biodegradable polymer' have different meanings, which may be confusing to the lay person, potentially making it harder for them to make a positive environmental choice when shopping
  • Additives can be added to any thermoplastic and are often used in LDPE, HDPE, PP, PVC and PET
• Classification of polymers


  • Bio-polymer (natural)
  • Bio-polymer (synthetic)
  • Biodegradable polymer
• 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 non-renewable resources such as crude oil and contains additives that cause it to degrade more quickly than traditional polymers
• Don't forget to include environmental implications, both positive and negative, when discussing bio-polymers and biodegradable polymers
• Examples of bio-polymers and their uses

  • Biopol (bio-batch additive) - Packaging products such as carrier bags, vending cups, nappies
  • Polylactic acid (PLA) - Packaging, medical uses such as slow-release medication patches
  • Polyhydroxyalkanoate (PHA) - Biomedical applications, slow-release medication, bone repair fixings, detergent washing sachets
  • Lactide and Glycolide (Lactel and Ecofilm) - Food film, bags, packaging wrap, bin bags, agricultural ground sheet, flower wrap
• Degradation of bio-polymers


  1. 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)

  2. Degradation occurs in the presence of oxygen (oxy-degradable - polymer turns into a fine powder with exposure to oxygen and is subsequently degraded by the action of micro-organisms)

  3. Degradation occurs in the presence of water (hydro-degradable - polymer quickly breaks down with exposure to water and is subsequently degraded by the action of micro-organisms)

  4. Degradation occurs because of the action of micro-organisms, which convert the material into water, carbon dioxide (CO2), biomass and possibly methane
• The ability of a polymer to biodegrade is dependent on the structure of the polymer rather than the origin of the raw material