PLASTICS

INTRODUCTION

A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs. Monomers of plastic are either natural or synthetic organic compounds.

Plastic is an organic substance and it consists of natural or synthetic binders or resins with or without moulding compounds. In general, it may be stated that plastics are compounds of carbon with other elements such as hydrogen, nitrogen and oxygen. The carbon combines with itself and other elements and it forms more complicated compounds.

Plastics are capable of flow when necessary heat and pressure are applied at some stage of their manufacture. The tern plastic is therefore accepted to be the best one to describe various diverse products of the plastic industry.

Classification of Plastics

1. Behavior with respect to heating2. Physical and mechanical

properties

Behavior with respect to heating

2. Thermoplastic

- Become soft when heated, hard when cooled.

- Shape and reshape is possible- Can be reused

2. Thermosetting

- Become rigid when moulded, at suitable pressure and temperature.

- When heated at 1270C to 1770C, they set permanently.

- Further application of heat does not alter the form.

- Soluble in alcohol and other solvents, hence used in making paints, varnishes.

- Durable, strong and hard. Available in different colors.

Physical and mechanical properties

1. Rigid plastics2. Semi rigid plastics3. Soft plastics4. Elastomers

RESINS

1. Thermoplastic resins- Alkyd – used in making thin films of plastic- Cellulose – tough and strong. Colors can be obtained.- Cumarone-indene – brittle in nature. Used for floor tiles, rubber

manufacture.- Methyl methacrylate – Acrylic- Styrene – light in weight, and high electric resistance.- Vinyl – odorless, non-toxic, transparent, and colorless. Used in wire and

cable coatings. Used in safety glass.

2. Thermosetting resins- Casein – absorbs moisture and not very strong. Workable, attractive

appearance. Used for buckles, buttons.- Melamine-formaldehyde – used in laminates for wall and ceiling lining.- Phenol formaldehyde – paints, varnishes, laminates, adhesives for

plywood.

ACRYLIC RESIN

1. Breaking resistance – it has more breaking resistance than glass. Due to its lower brittleness, the acrylic sheets can be used in thickness less than that of glass.

2. Chemical resistance – unaffected by most household detergents, cleaning agents and solutions of inorganic acid.

3. Clarity – used for windows and skylights.4. Easy formability – shapes like flat, square, spherical, circular can be

achieved.5. Finishing – available in all colors and can be joined by simple methods.6. Weather resistance – can be used in the exterior.7. Weight – light in weight and easy to handle.

UsesAcrylic sheets are used for skylights, door panels, window glazing, sun

screens, partition walls, bank cash counters, aquariums, etc.

PVC

PVC or Polyvinyl chloride is the most versatile plastic and the use of PVC pipes in buildings is being popular day by day.

The use of PVC for doors and windows is also going to be popular because of the following properties.

1. Rust-proof, rot-proof, termite-proof, and water-proof.2. Unaffected by air, dry heat, sub-zero temperatures and tropical rains.3. They do not fade, corrode, warp, require no maintenance.4. They provide an alternative to wood.5. They hold good for air-conditioned and heated rooms.6. They restrict dust penetration hence used in operation theatres, computer

rooms, food processing plants, electronic factories, etc.

Advantage of PVC pipes7. Permit high, smooth flow of water.8. Economical, resistant to chemicals, easy installation, etc.

A construction site illustration of the toughness properties of PVC-O Pipes

Pipes and Gutters

• Some of the advantages gained are a reduction in weight, ease of fabrication and installation, ease of repair and in many cases a reduction in cost. Because plastic pipes have a smoother bore than their metal counterparts, flow rates can be increased and scale formation is reduced. Plastic pipes also offer advantages in corrosion resistance.

Polyethylene pipes• With potable water distribution,

polyethylene pipes are now widely used. Pipes are available in diameters from a nominal 8 mm bore up to 1000 mm and above, made from specially developed grades of MDPE (medium density polyethylene) which meet a range of water industry specifications .

• One advantage of plastic pipes over more traditional materials is that in the smaller diameter sizes they are available in continuous lengths of up to 100m or even 250m in some cases. This reduces the number of joints needed and hence the number of potential leaks.

Roofing Systems• Corrugated plastic sheeting

has been used for roofing in conservatories and buildings where transparent panels have been required. However, in more recent times double and triple walled polycarbonate sheeting has become increasingly used, since this provides not only diffuse daylight for illumination but also heat insulation and hence reduced heating costs.

Twin or triple walled polycarbonate

• Provides a number of advantages during installation since it can be cut with conventional tools, is rigid to handle, does not require closely spaced supports, is light in weight and can be easily fitted. In addition, it can be cold formed or thermoformed into a variety of shapes to provide attractive and functional curved surfaces. Edges and joints can be sealed to prevent draughts. Another major advantage is its resistance to breakage.

Cladding Panels• Products are available in a

variety of colours, including wood grain finishes. These may be of solid UPVC, double skin or foam filled double skin construction.

• When fixing UPVC products, unlike their timber counterparts, due allowance must be made for expansion and contraction to prevent buckling of the sheets due to the heating effect of sunlight. Normally an allowance of 2 mm per metre length must be provided between sections. To allow for this special UPVC jointing and corner sections are available.

Plastic Fascia

Plastic Window Frames

Plastic Decorative Laminate• The normal structure of a plastic

decorative laminate includes a sheet of decorative paper impregnated (saturated) with one or several aminic resins, • covering the surface of a supporting

structure formed by a particleboard (for low pressure laminates) or by

• kraft paper sheets impregnated with Phenolic resin (high pressure laminates).

• Plastic decorative laminates have a wide range of uses, they can be used in the furniture industry for kitchen cabinet counters, bookshelves and door linings, among many other things. In the building industry they can be used for partitions screens in order to divide space in offices, houses, etc

Fiberglass reinforced PlasticFRP is a lightweight, extremely strong, and robust material. Although strength properties are somewhat lower than carbon fiber and it is less stiff, the material is typically far less brittle, and the raw materials are much less expensive. Its bulk strength and weight properties are also very favorable when compared to metals, and it can be easily formed using molding processes.

Properties – Aesthetic appealing, corrosion resistance, dimensional stability, durability, easy to repair, energy saving, freedom of design, light transmission, light weight, maintenance.

Uses – Concrete shuttering, Doors and window frames, Internal partitions, Roof sheets, Structural sections, temporary shelters, water storage tanks, etc.

Glassfibre Reinforced ConcreteGlass Fiber Reinforced Concrete (GFRC) is a type of fiber reinforced concrete. Glass fiber concretes are mainly used in exterior building façade panels and as architectural precast concrete.

Glass fiber reinforced(GFR) composite materials consist of high strength glass fiber embedded in a cementitious matrix. In this form, both fibers and matrix retain their physical and chemical identities, yet they produce a combination of properties that can not be achieved with either of the components acting alone. In general fibers are the principal load-carrying members, while the surrounding matrix keeps them in the desired locations and orientation, acting as a load transfer medium between them, and protects them from environmental damage. In fact, the fibers provide reinforcement for the matrix and other useful functions in fiber-reinforced composite materials. Glass fibers can be incorporated into a matrix either in continuous lengths or in discontinuous (chopped) lengths.

The design of GFRC panels proceeds from a knowledge of its basic properties under tensile, compressive, bending and shear forces, coupled with estimates of behavior under secondary loading effects such as creep, thermal and moisture movement.

Glass fiber reinforced concrete architectural panels have general appearance of pre-cast concrete panels, but are different in several significant ways. For example, GFRC panels will, on the average, weigh substantially less than pre-cast concrete panels due to their reduced thickness. The low weight of GFRC panels decrease superimposed loads on the building’s structural components. The building frame becomes more economical.

Glassfibre Reinforced Concrete (GRC) applications including:

Architectural claddingMoulding and landscapingRoofing, walls and windowsBuilding renovationFoundations and flooringModular buildingPermanent formworkRail cable channelingAcoustic barriers and screensBridge and tunnel lining panelsWater and drainage

Properties of GRC

GRC products are lightweight, easy to handle and fast to erectGRC products reduce loadings on buildings leading to significant savings in superstructure and foundationsGRC is excellent for reproduction and renovationGRC is environmentally friendlyGRC can be painted, faced with fine aggregate, coloured or simply left with a natural white or grey, smooth or textured finish. GRC is an excellent alternative for door surrounds and coping.GRC does not suffer from corrosion of the reinforcement and unlike traditional concrete, GRC does not require a minimum of concrete cover to the reinforcement.GRC is an ideal material for use in renovation. Thin lightweight panels are easy to fix and minimise the weight imposed on the existing structure. In many cases the opportunity is taken not only to improve the aesthetics of the building but also to improve the thermal and acoustic properties.GRC panels are light and easy to transport, small units .The strength of GRC is sufficient so that, even thin skin construction, small modular buildings can be designed without heavy structural frames.Aesthetically, the full range of natural and applied finishes, and the freedom of design, which characterise GRC permit solutions to satisfy any architectural requirement.