CHEM181 Notes: Polymers (PDF)

EXPERIMENT #9: POLYMERS Chemically, plastics are chainlike molecules of high molecular weight called polymers and are built from simpler chemicals, the individual links, called monomers. A different monomer or combination of monomers is used to manufacture each different type or family of...

EXPERIMENT #9: POLYMERS Chemically, plastics are chainlike molecules of high molecular weight called polymers and are built from simpler chemicals, the individual links, called monomers. A different monomer or combination of monomers is used to manufacture each different type or family of polymers. There are many polymers around us that are so familiar we take them for granted. Examples of man-made polymers are Teflon, nylon, Dacron, polyethylene, polyester, Orlon, epoxy, vinyl, polyurethane, silicones, Lucite and boat resin. Examples of natural polymers are starch and cellulose (from glucose), rubber(from isoprene) and proteins(from amino acids). Certainly, polymers have had and continue to have a great influence on our society. As these materials have been created, problems have arisen concerning their use. Many are not biodegradable so they contribute a significant volume to the garbage we create and the raw materials for their manufacture are a finite source. Plastic recycling is an important process for reducing waste and recovering potentially valuable raw materials. Different Types of Plastics and Their Classifications The Society of the Plastics Industry (SPI) established a classification system in 1988 to allow consumers and recyclers to identify different types of plastics. Manufacturers place an SPI code, or number, on each plastic product usually moulded into the bottom. This guide provides a basic outline of the different plastic types associated with each code number. Polyethylene Terephthalate sometimes absorbs odours and flavours from foods and drinks that are stored in them. Items made from this plastic are commonly recycled. PET(E) plastic is used to make many common household items like beverage bottles, medicine jars, rope, clothing and carpet fibre. High-Density Polyethylene products are very safe and are not known to transmit any chemicals into foods or drinks. HDPE products are commonly recycled. Items made from this plastic include containers for milk, motor oil, shampoos and conditioners, soap bottles, detergents, and bleaches. It is NEVER safe to reuse an HDPE bottle as a food or drink container if it didn’t originally contain food or drink. Polyvinyl Chloride is sometimes recycled. PVC is used for all kinds of pipes and tiles, but is most commonly found in plumbing pipes. This kind of plastic should not come in contact with food items as it can be harmful if ingested.  Low-Density Polyethylene is sometimes recycled. It is a very healthy plastic that tends to be both durable and flexible. Items such as cling-film, sandwich bags, squeezable bottles, and plastic grocery bags are made from LDPE. Polypropylene is occasionally recycled. PP is strong and can usually withstand higher temperatures. It is used to make lunch boxes, margarine containers, yogurt pots, syrup bottles, prescription bottles. Plastic bottle caps are often made from PP Polystyrene is commonly recycled, but is difficult to do. Items such as disposable coffee cups, plastic Code 7 is used to designate miscellaneous types of plastic not defined by the other six codes. Polycarbonate and Polylactide are included in this category. These types of plastics are difficult to recycle. Polycarbonate (PC) is used in baby bottles, compact discs, and medical storage containers. Their properties and common household uses are the following: Plastic Type General Proerties Common Household Uses Good gas & moisture barrier Mineral Water, fizzy drink and beer bottles properties Pre-prepared food trays and roasting bags High heat resistance Boil in the bag food pouches Clear Soft drink and water bottles Hard Fiber for clothing and carpets Tough Strapping Polyethylene Microwave transparency Some shampoo and mouthwash bottles Terepthalate Solvent resistant Excellent moisture barrier Detergent, bleach and fabric conditioner bottles properties Snack food boxes and cereal box liners Excellent chemical resistance Milk and non-carbonated drinks bottles Hard to semi-flexible and Toys, buckets, rigid pipes, crates, plant pots strong Soft waxy surface Plastic wood, garden furniture Permeable to gas Wheeled refuse bins, compost containers High Density HDPE films crinkle to the Polyethylene touch Pigmented bottles stress resistant  Excellent transparency Credit cards Hard, rigid (flexible when Carpet backing and other floor covering plasticised) Window and door frames, guttering Good chemical resistance Pipes and fittings, wire and cable sheathing Long term stability Synthetic leather products Good weathering ability Polyvinyl Stable electrical properties Chloride Low gas permeability Tough and flexible Films, fertilizer bags, refuse sacks Waxy surface Packaging films, bubble wrap Soft – scratches easily Flexible bottles Good transparency Irrigation pipes Low Density Low melting point Thick shopping bags (clothes and produce) Polyethylene Stable electrical properties Wire and cable applications Good moisture barrier Some bottle tops properties Excellent chemical resistance Most bottle tops High melting point Ketchup and syrup bottles Hard, but flexible Yoghurt and some margarine containers Waxy surface Potato crisp bags, biscuit wrappers Translucent Crates, plant pots, drinking straws Polypropylene Strong Hinged lunch boxes, refrigerated containers Fabric/ carpet fibres, heavy duty bags/tarpaulins Clear to opaque Yoghurt containers, egg boxes Glassy surface Fast food trays Rigid or foamed Video cases Hard Vending cups and disposable cutlery Brittle Seed trays High clarity Coat hangers Polystyrene Affected by fats and solvents Low cost brittle toys There are other polymers Nylon (PA) Acrylonitrile butadiene styrene (ABS) that have a wide range of Polycarbonate (PC) Layered or multi-material mixed uses, particularly in polymers engineering sectors. They are identified with the number 7 and OTHER (or a triangle Others with numbers from 7 to 19). Density of Plastic Materials Other Properties PETE Yellow flame Slow flame Does not ignite /self extinguishes Little or no smoke Plastic drips Does not char Sinks in water Insoluble in acetone HDPE and LDPE Blue, yellow tipped flame Burns slowly Plastic drips Smells like candle wax(parrafin) Floats in water Insoluble in acetone PVC Green flame Sinks in water Black smoke with soot in air Insoluble in acetone PP Blue, yellow tipped flame Plastic drips when burned Burns slowly Floats in water Insoluble in acetone PS Yellow flame Plastic drips when burned Dense black smoke with soot in air Burns rapidly Sinks in water Soluble in acetone