1. Muhammad Umair Bukhari Engr.umair.bukhari@gmail.comwww.bzuiam.webs.com 03136050151

2. Polymers. Macromolecules. Natural & synthetic Their unique properties have allowedthem to replace metals.1. strength: weight ratio2. Designing with plastics3. Cost of using plastics4. Ease of manufacturing 3. plastic is cheaper than most metal weighs a lot less (better fuel economy). Plastic can be injection molded, vacuummolded, cast and generally machined or"worked" faster and cheaper than metal. for winter cold areas where the roads aresalted, the corrosion resistance of plastics 4. Bio-plastic green phonesUrethane bumpers 5. Thermoplastics:Amorphous structure. Secondary bonds.Linear & branched polymers have weaksecondary bonds. Return to their originalhardness when cooled. Reversibleheating possible. Examples: acrylics, nylon, PVC,polyethene 6. Thermosets:Cross-linked in a 3d network. Strength ofbond. Hardness & strength in material notaffected by temperature. Polymerization will require heat &pressure so that the shape of the part ispermanently set.(curing) Irreversible. Decomposes. Chars. 7. Tg not sharply defined. Become rubberyover a narrow range. Polymerization in 2 steps. At chemicalplant & at parts-producing plant. Phenolics. Pots & pans. Possess better insulating, mechanical &chemical properties. Also betterdimensional stability. 8. theyneed to be painted for UVprotection. Tooling: Normally more expensive forplastic because of the surface finishrequired (in the mold) and the number ofcavities are larger, thus increasing thecost. 9. Various chemical reactions were used tomake cellulose in to cellulose acetate.Photographic films. Packaging sheets. So additives are added to impart certainspecific properties. Modify properties like stiffness, strength,color, flammability, weatherability. 10. Fillers: improve mechanical properties.Decreases the cost/unit weight. Plasticizers: add flexibility & softness tothe polymer by reducing Tg . Stabilizers: UV rays & oxygen tend toweaken & break the primary bonds.Degradation. Colorants Flame retardants 11. Cellulosics Fluorocarbons Polyamide(nylons) Polycarbonates Polyesters Polyethylenes Polypropylenes Polystyrenes PVC 12. Acrylicis a useful, clear plastic thatresembles glass, but has properties thatmake it superior to glass in many ways.Common brands of high-grade acrylicinclude Plexiglass. moderate strength, good optical quality &weather resistance. Transparent but can bemade opaque. Generally resistant tochemicals. Typical applications: lenses, signs,automotive lenses, window glazing, artificialnails, paints 13. For all of its advantages, there are twodisadvantages of acrylic: it is moreexpensive than glass, and if exposed to adirect flame it will melt and eventually burn. Has good impact strength, higher than thatof glass or polystyrene, but significantlylower than that of polycarbonate orengineering polymers. In the majority ofapplications, it will not shatter but insteadbreaks into large dull pieces. 14. ABSis impact resistant, abrasion &chemical resistant. Resistance tochemicals & corrosion. Does not igniteeasily. Typical applications: pipes & fittings, toolhandles, telephones & appliances. High performance at high & lowtemperatures. (-400 F to 1800 F) 15. The main disadvantage to using ABS pipefittings are that it is not very durablewhen it comes to solvents or fatigueresistance. It also has minimal UVresistance, so should not be left exposedto the sun. The nitrile groups from neighboringchains, being polar, attract each otherand bind the chains together, makingABS stronger than pure polystyrene 16. PVC has many advantages over pipesmade of galvanized steel and copper. To begin with, it is the most lightweight ofthe three. This makes it easier to install.Also, it is the least expensive of the threetypes. Also, it can withstand higher waterpressure than the copper. Also, PCV isnon-conductive, will not rust, and is not asconducive to condensation. 17. Another advantage is that PVC can be placed under concrete slab without reacting to the concrete. Moreover, it is self-insulating. That is why it can handle hotter temperature water. 18. Eventhough it can withstand hot watertemperatures, it is less flame resistant.That is one of the biggest disadvantagesof PVC. Also, PVC contains volatile compoundswhich are harmful to the environment.Furthermore, some people havecomplained that PVC pipes cause waterto have a slight plastic taste. 19. ElasticModulus & tensile strengthdecrease with increasing temperature.Toughness increases. Water absorption. Adverse affect. Solvents. Residual stresses. Radiation & visible light. Anisotropy due to cold rolling. 20. Friction& wear (self-lubricating,TEFLON) (gears, roller skate wheels,prosthetic joints) Thermal & electrical conductivity Low specific gravity (0.9-2.2) High coefficient of thermal expansion