PLASTICS. Chapter 5. Materials of Construction-Plastics 1

Transcription

1 PLASTICS Chapter 5 Materials of Construction-Plastics 1

2 Plastics Plastics are synthetic materials which are composed of high molecular weight substances consisting of macromolecules of colloidal dimensions. Colloidal substance: larger than atomic and simple molecular dimension but smaller than particles visible to naked eye. Materials of Construction-Plastics 2

3 The monomers in linear or branched chains are linked by primary covalent bonds Large chain-like molecules are held together by intermolecular (secondary) forces of attraction. Intermolecular Forces are electrostatic forces of attraction that exist between an area of negative charge on one molecule and an area of positive charge on a second molecule. The monomers in the cross-linked structure are connected with each other by strong covalent bonds. Materials of Construction-Plastics 3

4 Classification of Plastics: Thermoplastics- Thermosets Thermosets - are those plastics that do not soften upon being heated. Heating makes these polymerize further. Thus, cross-links between molecules in adjacent chains are developed. The result is a complex, interconnected network in which the chains are no longer free to move. All thermosetting plastics are brittle. Phenol-formaldehyde (bakelite), epoxies, polyesters, silicones.. The main use of thermosets in building are as adhesives, binders for glass-fiber reinforced plastics and binders in paints. Materials of Construction-Plastics 4

5 Some types of plastics commonly used in construction Materials of Construction-Plastics 5

6 Polyethylene (PE) Thermoplastic material, cheap and versatile, resistant to chemicals, classified by its density. Low Density Polyethylene: (sg: ) used for sheeting to resist moisture penetration, e.g. damp proof membranes. Softens about 70 to 105 o C High Density Polyethylene: (sg: ) due to their chemical stability and toughness, they are used in underground pipes. PE should be protected from UV rays, high thermal movement of PE precludes its use for conveying hot water in buildings. Materials of Construction-Plastics 6

7 Polyvinyl Chloride (PVC) PVC in either the natural rigit form or made flexible by the addition of plasticizers is versatile and low in cost. It has good weathering properties and is unaffected by acids and alkalies. It softens about 70 o C. Materials of Construction-Plastics 7

8 Polyvinyl Chloride (PVC) Thermoplastic material, mostly used in construction as; insulation material on electric wires, pipes (drainage or water supply sistems), sidings.. windows... Materials of Construction-Plastics 8

9 Polypropylene (PP) Thermoplastic material, resistant to chemicals, softens at higher temperatures than other thermoplastics Used for waste systems, manholes PP fibers has tensile strength values approaching to that of steel, used to improve toughness of brittle materials such as concrete. Materials of Construction-Plastics 9

10 Teknoyapi.com Polystyrene (PS) Thermoplastic material, used to produce: Wikipedia.org Expanded polystyrene (EPS) is produced by expanding polystrene with blowing agent. The solid plastic is expanded into a foam through the use of heat, usually steam. Extruded polystyrene (XPS), is commonly known by the trade name Styrofoam. The voids filled with trapped air give it low thermal conductivity. This makes it ideal as a construction material and it is therefore sometimes used in structural insulated panel building systems. Materials of Construction-Plastics 10

11 Uses of Plastics in Construction Plastic materials produced by reinforcing the plastic with a fibrous material are commonly used for structural purposes Reinforcing materials: glass fibers (fiberglass), cotton, asbestos, metallic fibers Fiberglass (also called glass fibre) is a material made from extremely fine fibers of glass. It is used as a reinforcing agent for many polymer products; the resulting composite material, properly known as fiberreinforced polymer (FRP) or glass-reinforced plastic (GRP), is called "fiberglass" in popular usage. Materials of Construction-Plastics 11

12 Uses of plastics for structural purposes Glass-fiber-reinforced corrugated panels are used for roofing, for room dividers, patio covers These have good dimensional stability, good resistance to weathering and breakage, and transparent or translucent properties. Ref: alibaba.com Materials of Construction-Plastics 12

13 Uses of plastics for structural purposes Flat plastic sheets, with or without reinforcing, are often used for glazing. These are lighter in weight than glass and have greater impact resistance. paintfilmlamination.com/ Materials of Construction-Plastics 13

14 Uses of plastics for structural purposes Plastic sheets thermoformed into transparent roof domes are used for covering showrooms, stadiums, etc. Materials of Construction-Plastics 14

15 Sandwich Panels Plastics are used in the manufacture of sandwich panels to be employed in curtain-wall construction. The common composite sandwich structure is made up of two major elements, the skin and the core. Sandwich panel skins are the outer layers and are constructed out of a variety of materials. Wood, aluminum, and plastics are commonly used. The core materials provide many of the panels desirable properties and are often composed of wood, aluminum, foam or plastic as grid or honeycomb structure. Acrylics, polyprophylenes, polyurethanes, polycarbonates and polysters are used in the production of sandwich panels. Materials of Construction-Plastics 15

16 Uses of plastics Nonstructural plastic materials such as wall and floor coverings, vapor or moisture barriers, expansion joint materials, pipes Rd.com Plasticpipesgroup.com Materials of Construction-Plastics 16

17 Auxiliary Uses of Plastic Materials Making forms for precast concrete products, As adhesives in the manufacture of gluelaminated wood, plywood... For material coating, In the manufacture of lighting systems, As the basis of various paints and varnishes, As sealing compounds and fillers for expansion joints. Materials of Construction-Plastics 17