Addition Polymers

Addition Polymers

1. Depending on method used, different densities of polymers can be made. HIGH DENSITY poly(ethene) has linear chains giving it strength so it is used in toys, detergent bottles, and water pipes. LOW DENSITY poly(ethene) has branched chains giving it little strength and making it flexible so it is ideal for plastic films and bags.

2. Environmental Concerns

   • Disposing of waste polymers
     • Readily available, cheap to purchase, more convenient than alternatives. However, the lack of reactivity that makes polymers good for storage, makes it challenging to dispose of them. They are often non-biodegradable and polymer waste can kill marine life by suffocating them.
     • Recycling conserves finite fossil fuels and decreases the amount of waste going to landfill. First they have to be sorted by type, then chopped into flakes, washed, dried, and melted. Recycled polymer is cut into pellets before being used to make new products!
     • PVC Dispoal is hazardous due to high chlorine content and range of additives present in polymer. Landfill is not sustainable and if you burn PVC, you produce corrosive HCl gas and other pollutants like toxic dioxins.
       • So recycling PVC is better for the environment. New tech uses solvents to dissolve the polymer. High-grade PVC then precipitates from solvent.
     • Some polymers are difficult to recycle but they are derived from fossil fuels so have a high stored energy value.
       • Waste polymers can be incinerated to produce heat, generating steam to drive a turbine producing electricity.
     • Feedstock recycling= the thermal and chemical processes that can reclaim monomers, gases, or oil from waste polymers. These materials can be used as raw materials for the production of new polymers. Major advantage is that it is able to handle unsorted and unwashed polymers!
   • Bioplastics are produced from plant starch, cellulose, plant oils, and proteins. They offer a renewable and sustainable alternative to oil-based products. Protects environment and conserves valuable oil reserves!
     • Biodegradable polymers are broken down by microorganisms into water, CO2, and biological compounds. Made from starch or cellulose or contain additives that alter the structure so that they can biodegrade. Compostable polymers degrade leaving no visible or toxic residues e.g. PLA formed by condensation polymerisation.
     • Photodegradable oil-based polymers contain bonds that are weakened by absorbing light to start the degradation, or light-absorbing additives are used.