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Mechanical properties - the working properties with the influence of other…
Mechanical properties - the working properties with the influence of other forces
Toughness - the toughness of polymers determines their ability to absorb energy and deform plastically without cracking. A product that would have to be tough is a cycle helmet so it could protect the person's head if they fall off. The polymer material absorbs the energy from the impact and s specifically designed to split, dissipating the energy.
Flexibility - the ability of a material to be bent or folded without breaking whilst stiffness is a measure of how rigid a material is. Flexible PVC sheet is often sold by the the roll and used for protective coverings - films is used for laminating. Thermoplastics vary in their level of flexibility, often relating to their thickness in comparison, thermosets tend to be very stiff when set.
Elasticity - is a material's resistance to distortion and ability to return to its original shape. Polyurethane is used in the textile industry to produce fabrics that have good elasticity. Balloons are made from polymers called elastomers such as rubber or latex. Inflatable products include things like airbeds, balloons, tire or life jacket.
Moldability - a polymers ability to be shaped into a form or mould will dictate the type of product it is used for. Thermoplastics are usually moulded in a hot or molten state, usually under mechanically exerted pressure, using compressed air, hydraulics or rotation. Thermosets are usually moulded in cold liquid form and cured using a catalyst.
The ability to cut and score depends on the hardness of the material. Acrylic is hard and easily scored and snapped however it may chip or crack when machine cut. HDPE and HIPS are softer and more flexible so will score less well it can be cut more easily without chipping.
Additives and recyclability
Additives for processing - Additives are sometimes used to make polymers easier and more efficient to process. Plasticisers enhance flow characteristics and enable polymers to be moulded at higher temperatures. Thermal antioxidants help to prevent oxidation due to heat exposure during the manufacturing process.
Additives for performance - Additives may also be added to prolong the lifespan of products. Antioxidants reduce the degradation and deterioration from exposure to air and water and help prevent cracking and discoloration. UV light stabilisers help improve the material’s resistance to degradation by UV light.
Additives to improve function - Additives are used to enhance the performance characteristics of polymers. Fire retardants increase the materials resistance to fire. Plasticizers are used to make materials more stretchy. Antistatic additives are used to reduce the build up of static charge.
Additives for biodegradability - additives are also used to increase the biodegradability of thermoplastic polymers. Thermoplastics degrade very slowly, ultimately breaking into particles that will not assimilate into the soil but instead pollut and find their way to the food chain. Bio-batch materials are additives that enable a thermoplastic to biodegrade meaning they can be broken down more quickly and safely by natural bacteria.
Recyclability - recycling is the process of recovering waste polymers and reprocessing them into useful materials and products. Recycling polymer waste prevents it from being sent to landfill or dumped. It reduces reliance on the production of new materials from finite resources.
Physical properties - the materials inherent characteristics
Thermal Insulation - thermal insulators reduce heat transfer, especially between objects and people. The insulating properties of polymers are exploited in products such as saucepan handles and kitchen utensils. Some polymer materials are formed with air trapped inside them to create foams that are used as insulation in packaging and in the construction industry.
Electrical insulation - an electrical insulator is a material that does not allow electricity to flow freely through it. Polymers are very good electrical insulators, making them especially useful for product casings and shielding. Electrical light fittings and sockets are often made from urea formaldehyde, a thermoset which is heat and burn resistant.
Melting points - is the temperature at which a material changes state from solid to liquid. When heated, thermoplastics become soft, pliable and ‘plastic’ can then be shaped and moulded. The melting point of a polymer will often dictate its application. Thermosetting polymers do not melt but start to decompose and char at high temperatures.
UV resistance - in the same way that skin is burnt by exposure to the sun, polymers are also affected by its UV radiation. UV bleaches the colour from polymers like ABS, which is commonly used for products such as garden furniture. It also affects the polymer mechanical properties, degrading it and making it more brittle. Acrylonitrile styrene acrylate has been developed as an alternative for ABS as it retains its colour and has greater UV resistance
Resistance to liquid and chemicals
Chemical resistance - Some polymers are selected specifically for their resistance to chemicals. High density polyethylene is particularly resistant to chemicals and is used to manufacture bleach bottles and chemically resistant piping. HDPE is also used in large sheets to line landfill sites, acting as a barrier between the waste and the soil.
Resistance to liquids - generally most polymers are resistant to liquids however the length of time they can be used for varies. Both HDPE and polyethylene terephthalate PET are used in plastic water bottles however there are differences. HDPE is reusable and recyclable however PET is recyclable but should not be reused as overtimes the plastic may leach chemicals into the water.