Question

give reasons
(ii) bakelite is used for making handles of utensils and pvc is used as an insulation cover in electric wires.
(ii) why should we use two types of bins for disposing waste.
2) why is rayon known as regenerated fibre.

Answer 1

"Plastic" is a term applied to any material which can be molded or bent into shape. So for instance soft toffee, modeling clay or red hot iron is plastic because it can be reshaped. In general though when we speak of plastic, we mean polymers or synthetic materials made from petrochemicals.
There are at least 10 different types of plastics used in the home, the type used depending on the application. Many of these plastics can be recycled and are marked with a symbol and numeric code indicating the plastic type.

Types of Plastic Used Around the Home

There are lots of different types of plastics used in and about the home. The most common ones are:

Polyethylene (Polythene)Poly Vinyl Chloride (PVC) also known as vinylPolypropylenePolystyrenePolytetrafluoroethylene (Teflon)NylonPolyesters, polyethylene terephthalate (PET) being the most commonAcrylicPolycarbonatePolyurethane

What is Plastic Used For?

Well virtually everything! From the sixties onwards, plastic began to replace or supplement many items which were traditionally made from materials such as metal, wood, glass, stone, ceramic and natural textiles. Some examples:

Textiles - Cotton, wool, silk, linen and hemp were the original textiles used from ancient times. We now have acrylic, polyester and nylonFootwear - Shoes originally had leather uppers and soles. PVC is now used for sneakers, and soles are made from PVC or polyurethane foamWindows and doors - Originally made from timber, they are now also made from PVCFood storage, eating and drinking utensils and bottles - They were originally ceramic, glass or metal but are now also made from polyester, polypropylene and polyethylene (Polythene)Electrical insulation - Originally rubber, now also PVCFurniture - Plastics such as polystyrene are used for stackable hard seating. Padded seating coverings are often made from PVC or "vinyl" and soft, flexible, polyurethane foam forms the internal paddingCar and machine parts - Many parts in cars were made from metals such as steel, brass, aluminium alloy and rubber. These are now often replaced by plastics such as PVC, nylon, ABS and polystyreneCasings of electronic/electrical devices and appliances - Originally made from wood, metal or Bakelite, they are now generally made from polystyrene or polypropyleneFixtures and fittings in homes - Lighting, electrical fittings and bathroom fittings

Why is Plastic Used So Much?It's cheap and made from a relatively inexpensive raw materialIt's relatively strong and can be used for many applicationsMany plastics are inert so can be used in contact with solvents, water and other chemicals without suffering any ill effectsUnlike organic materials such as wood and natural textiles, plastic doesn't decay when exposed to wet or damp conditions for long periodsThermoplastics can be molded into lots of different shapes using an industrial process called injection molding (basically forcing soft plastic into a mold under high pressure). So no machining is necessary as is the case with metals. Plastics can also easily be 3D printedPlastics can be easily coloredNylon, a tough and durable type of plastic can be used for moving parts in machinery without the requirement of lubrication (it has a relatively low coefficient of friction like Teflon)Plastic is non conductive of electricityMany plastics can be easily recycled by being melted down or shredded to make new productsAs a synthetic fiber, it can be more durable than natural fibers in textiles

What Are the Disadvantages of Plastic?Unlike scrap metals for instance, it is such a ubiquitous and cheap material that there has been very little incentive to recycle it until recent decadesFor some applications, plastics cannot be used because they lack the strength of metals. Composite materials such as carbon fiber (a fiber reinforced polymer) will eventually become more widely usedWhile plastic parts are often used in machines and tools, they aren't as tough or durable as metal, so plastic parts can wear or break more easilyUltra Violet (UV) exposure from sunlight can cause plastics to crack and degrade over time unless special additives are added to the material during manufactureThere are concerns about carcinogens used as fillers or trapped monomers leaching out of plastics used in food storage containers and drinking vesselsIt can't be used for applications where it is exposed to very high temperatures