TITLE: Give information & collect different types of additional polymers ,their properties and uses in domestic purposes.
DESCRIPTION:
In polymer chemistry, an addition polymer is a polymer that forms by simple linking of monomers without the co-generation of other products. Addition polymers are formed by the addition of some simple monomer units repeatedly. ... Generally polymers are unsaturated compounds like alkenes, alkalines etc.
· What are the types of polymers?
There are 3 principal classes of polymers – thermoplastics, thermosets, and elastomers. Differentiation between these classes is best defined by their behaviour under applied heat. Thermoplastic polymers can be either amorphous or crystalline. They behave in a relatively ductile manner but often have low strength.
OUTCOMES:
Thermoplastic:
From Simple English Wikipedia, the free encyclopedia
Jump to navigation Jump to search
Polyethylene crate
A thermoplastic is a material, usually a plastic polymer, which becomes more soft when heated and hard when cooled. Thermoplastic materials can be cooled and heated several times without any change in their chemical or mechanical properties. When thermoplastics are heated to their melting point, they melt to a liquid. They freeze to a glassy state when cooled below their glass transition temperature.
Thermoplastic materials have many features. Some products made from thermoplastic materials are used for electronic applications. They protect against electrostatic discharge and radio frequency interference. Thermoplastics are one of the main two types of plastics.[1]
Thermoplastic can be moulded into any shape. Thermoplastics differ from thermosetting polymers. Thermosets form irreversible chemical bonds during the curing process.
Main types of thermoplastics
PET (polyethylene terephthalate) :- Light, rigid or semi-rigid, naturally transparent or colorless, PET is an excellent moisture and gas barrier and is resistant to impacts. It is one of the most easily recyclable plastics and is used to produce bottles, bags and synthetic fibers for clothing.
HDPE (high-density polyethylene) :- HDPE is translucent, strong and easy to process, resistant to impacts and non-toxic. It is used to make bottles, tanks, bins and containers for transport.[2]
LDPE (low-density polyethylene) :- LDPE can be translucent or transparent. Suitable for contact with food, it is the lightest and most heat-sensitive plastic. It is used for packaging, bags, sacks, cable coatings, containers, pipes and toys.
PVC (polyvinyl chloride) :- PVC is a very versatile plastic, resistant to wear and tear, chemical and atmospheric agents and fire. It is used in the paper industry and for packaging, food containers, credit cards, furnishings, clothing and toys.
PP (polypropylene) :- Transparent, light and strong, this material can be used as both a plastic and a fiber. Easily colored, it does not absorb water. It is used to make textile fibers, couplings, containers for transport, furniture, carpets, ropes and food containers.
PS (polystyrene or styrofoam) :- One of the most important thermoplastic materials, it is transparent, hard and inflammable, very bright and inert against many corrosive agents. It can be given shiny or opaque colors. Polystyrene is commonly used to replace glass, aluminum and wood because it is cheaper. It can also be used in packaging materials (including for foods), containers, boxes, lamps, disposable objects, cups and toys.
Thermosets:
Thermosets are specific class of polymers that form well-defined, irreversible, chemical networks that tend to grow in three dimensional directions through the process of curing, which can either occur due to heating or through the addition of a curing agent [29], therefore causing a crosslinking formation between its chemical components, and giving the thermoset a strong and rigid structure that can be added to other materials to increase strength. Further applications of thermosets include coating and epoxy adhesives. Around 69% of the application of thermosets present in the construction and building industry, other uses of thermosets are in transportation, adhesives, and electrical equipment. Thermosets are also highly used in advanced applications, especially in the aerospace and military industries due to the multiple composites that can be produced with the presence of thermosets, including reinforced carbon fibers and glass.
Elastomer:
Elastomers (rubbers) are special polymers that are very elastic. They are lightly cross-linked and amorphous with a glass transition temperature well below room temperature. They can be envisaged as one very large molecule of macroscopic size. The intermolecular forces between the polymer chains are rather weak. The crosslinks completely suppress irreversible flow but the chains are very flexible at temperatures above the glass transition, and a small force leads to a large deformation (see also rubber elasticity).1 Thus, elastomers have a low Young's modulus and very high elongation at break when compared with other polymers. The term elastomer is often used interchangeably with the term rubber, although the latter is preferred when referring to vulcanized rubbers.
Elastomers can be classified into three broad groups: diene, non-diene, and thermoplastic elastomers. Diene elastomers are polymerized from monomers containing two sequential double bonds. Typical examples are polyisoprene, polybutadiene, and polychloroprene. Nondiene elastomers include, butyl rubber (polyisobutylene), polysiloxanes (silicone rubber), polyurethane (spandex), and fluoro-elastomers. Non-diene elastomers have no double bonds in the structure, and thus, crosslinking requires other methods than vulcanization such as addition of trifunctional monomers (condensation polymers), or addition of divinyl monomers (free radical polymerization), or copolymerization with small amounts of diene monomers like butadiene. Thermoplastic elastomers such as SIS and SBS block copolymers and certain urethanes are thermoplastic and contain rigid (hard) and soft (rubbery) repeat units. When cooled from the melt state to a temperature below the glass transition temperature, the hard blocks phase separate to form rigid domains that act as physical crosslinks for the elastomeric blocks.
Manufacturing elastomeric parts is achieved in one of three ways: injection molding, transfer molding, or compression molding. The choice of the molding process depends on various factors, including the shape and size of the parts, the required tolerance, as well as the quantity, type of elastomer, and raw material cost.
As with almost any material, selecting the right elastomeric product for the application requires consideration of many factors, including mechanical and physical service requirements, exposure to chemicals, operating temperature, service life, manufacturability of the parts, and raw material and manufacturing cost.
· Their uses and properties:
· Different polymers have different properties. This means that different polymers have different uses.
·
· Poly(ethene) is used to make polytunnels, sheltering crops from the weather
· The table gives examples of polymers, their common names, and their typical properties and uses.
Thermoplastics:
Much of it is used by the construction industry, such as for vinyl siding, drainpipes, gutters and roofing sheets. It is also converted to flexible forms with the addition of plasticizers, thereby making it useful for items such as hoses, tubing, electrical insulation, coats, jackets and upholstery.
properties:
Thermoplastics generally provide high strength, flexibility and are resistant to shrinkage, depending on the type of resin (the polymer in melted liquid form). They are versatile materials that can be used for anything from plastic carrier bags to high-stress bearings and precision mechanical parts.
Uses of Thermosetting Polymers
Thermosets are used to produce electrical goods and components, including insulators and panels. These are used to produce construction equipment panels. Because they are heat resistant, they are used to produce heat shields. In automobiles, thermosets are used to produce brake pistons.
Properties: Hard, brittle, opaque, good electrical and heat resistance, resistant to deformation under load, low cost, resistant to most acids.
Elastomers:
Primary uses for elastomer are seals, molded flexible parts and adhesives and used in vehicle manufacturing, food production, scientific applications and chemical processes. ... Polyurethanes are used for electrical potting compounds, spandex fibers, carpet underlay, gaskets, seals and flexible foam seating.
Mechanical Properties of Elastomers
- One of the distinguishing properties of elastomers is their high elasticity. ...
- Energy elasticity: describes the plastic deformation / plastic strain of materials. ...
- Entropy: Physical term in thermodynamics, characterizing thermal processes.
0 Comments