What kind of plastics can be easily moulded by just heating ?

A thermoplastic is a plastic that softens when heated and hardens again when cooled. Thermoplastics can generally go through many melt/freeze cycles with no appreciable chemical change, making them suitable for recycling. Nearly all plastics can be catagorized as either a thermoplastic or thermosetting material. A partial list of thermoplastics is given below:

> Acrylonitrile butadiene styrene (ABS)
> Polyvinyl chloride (PVC)
> Polypropylene
> Polyethylene
> Acrylic
> Celluloid
> Polystyrene
> Cellulose acetate

Thermoplastic and thermosetting resins are polymeric materials that have the capability of being moulded or shaped, usually by the application of heat and pressure. This property of plasticity, often found in combination with other special properties such as low density, low electrical conductivity, transparency, and toughness, allows plastics to be made into a great variety of products. These include tough and lightweight beverage bottles made of polyethylene terephthalate, flexible garden hoses made of polyvinyl chloride, insulating food containers made of foamed polystyrene, and shatterproof windows made of polymethyl methacrylate. Polyester thermoplastics are easy to recycle. The thermosetting materials are difficult to recycle, but can be ground into powders and used as fillers.

What causes things to be elastic?

Elasticity is the ability of a solid to return to its original shape and size after it has been deformed by a force. All solids have some elasticity. Familiar materials that have elasticity include the springs in cars and the rubber in tennis balls. Solids return to their original shape and size if the deforming force was not too great. If the stress (deforming force per unit of area) applied to a solid exceeds the solid's elastic limit, the solid will keep its new shape. The elastic limit depends markedly on the type of solid considered; for example, a steel bar or wire can be extended elastically only about 1 percent of its original length, while for strips of certain rubber-like materials, elastic extensions of up to 1,000 percent can be achieved.
The elastic properties of many solids in tension lie between these two extremes. The different macroscopic elastic properties of steel and rubber result from their very different microscopic structures. The elasticity of steel and other metals arises from short-range interatomic forces that, when the material is unstressed, maintain the atoms in regular patterns. Under stress the atomic bonding can be broken at quite small deformations. By contrast, at the microscopic level, rubber-like materials and other polymers consist of long-chain molecules that uncoil as the material is extended and recoil in elastic recovery. For further information on rubber elasticity, please refer the URLs below:

http://www.matter.org.uk/matscicdrom/manual/rb.html

http://www.poco.phy.cam.ac.uk/teaching/A_Donald/rubbers.htm

How is plastic made?

Plastics are synthetic materials that can be shaped in almost any form. Manufacturers make plastics from chemicals. The substances used to make plastics are called synthetic resins. These synthetic resins are made from chemicals that come from such natural materials as coal, limestone, petroleum, salt and water. Making synthetic resins can be thought of as "building" chain molecules or polymers. When a manufacturer combines the chemical compounds, various chemical reactions take place.
The reactions cause certain atoms to cluster together and form the monomer links. The monomers are then connected into a chain-like molecule by a process called polymerisation. This process changes the substance into a synthetic resin. Resin makers can add pigments to produce unlimited varieties of transparency and colour. Manufactures use synthetic resins to make many types of products. These products include paints, lubricants, adhesives, and moulded items such as bottle caps, containers, utensils and hulls of small boats. Various methods are used to make each type of product. The most important methods are moulding, casting, laminating, extrusion and calendering.
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What is piezoelectric materials?

Piezoelectric effect is a property of some crystals (for example, quartz) to develop an electromotive force or voltage across opposite faces when subjected to a mechanical strains, and conversely, to expand or contract in size when subjected to an electromotive force. Piezoelectric crystal oscillators are used as frequency standards (for example, replacing balance wheels in watches), and for producing ultrasound. The crystals are also used in gramophone pickups, transducers in ultrasonics, and certain gas lighters.

How is glass made?

Sand, soda ash, limestone, and borax are raw materials for glassmaking. These materials all are dry powders which look much alike, but are capable of producing greatly different results. They come to the glass plant in railroad cars and are stored in large silos. After they are carefully weighed and mechanically mixed in the proportions, the glassmaker adds cullet. Cullet is either recycled glass or waste glass from a previous melt of the same kind of glass. The addition of cullet reduces the amount of heat needed to melt the new batch. After mixing, the batch goes to the melting units in batch cars, in hoppers, or on conveyor belts. Small quantities of optical glass, art glass and speciality glass are made in refractory pots.
Larger quantities of glass are made in furnaces. The raw materials are fed into the loading end as rapidly as molten glass is removed from the working end. There are four main methods of shaping glass: blowing, pressing, drawing, and casting. After the shaping process, annealing is used to restore the strength of the glass. Tempering and other finishing techniques may also be used to further strengthen the glass.

What is ceramic?

Ceramics denotes the manufacture of any product that is made from a nonmetallic mineral by firing at high temperatures. Industrial ceramics can thus be said to comprise all industrially used solid materials that are neither metallic nor organic. Ceramics include brick, cement, glass, and porcelain. They also include some unusual materials used in electronics and spacecraft. Most ceramics are hard and can withstand heat and chemicals. These properties give them a wide variety of uses in industry.
Most ceramic products, like their mineral ingredients, can withstand acids, gases, salts, water, and high temperatures. But not all ceramic products have the same properties. Common ceramics are good insulators--that is, they conduct electricity poorly. However, certain ceramics lose their electrical resistance and become superconductors when they are cooled. Some ceramic materials are magnetic. Engineers control the properties of ceramics by controlling the proportion and type of materials used.