Compiled by: Rashi Goel July 2015 Thermocol/Styrofoam – Correctly called, Expanded Polystyrene 1. Forms of Polystyrene 2. Polystyrene Foam – About the Material 3. Chemical composition & Manufacturing process 4. Chemical properties 5. General Properties 6. Uses of Thermocol 7. Thermocol in India – Production & Wastage 8. Impact of Thermocol on the Environment 9. Impact of Thermocol on Human Health 10. Ways to Reduce Thermocol – Alternatives & their Feasibility 11. Ways to Reuse Thermocol - Reuse Potential 12. Ways to Recycle Thermocol – Recycling potential 13. Thermocol – Facts & Figures 14. Thermocol – Laws, Policies, Regulations Some of the basic questions answered by this research: 1. What exactly is Thermocol? What is it made of? 2. How is it made of? Can it be made as a small scale industry? 3. Does its manufacturing cause any pollution? 4. How strong is Thermocol on its own? Is its fragility an issue when handling waste? 5. What is the situation in Indian waste regards Thermocol? 6. What have people done around the world to replace Thermocol? What can Thermocol be replaced by? 0 1. Forms of Polystyrene Did you know? Thermocol and Styrofoam are both actually brand names of the foam version of a chemical compound called Polystyrene. So, the actual name to refer to this material by is Expanded Polystyrene or EPS. Also, EPS is basically a PLASTIC. For the sake of ease, uniformity and relevance of this research in India, the word Thermocol will be used to refer to any type of Polystyrene foam for most part of this research. An introduction to Polystyrene Polystyrene was discovered by Eduard Simon in Berlin in 1839.It has the numerical code 6 amongst all plastics. Polystyrene based products are classified as Plastic/Foam #6. Included in this category are Expanded Polystyrene (EPS) and Polystyrene Paper Foam (PSP Foam). In addition, packing peanuts are Plastic #6. Most foam #6 products can be identified by the resin identification code stamped on the material. Polystyrene is one of the most versatile plastics. Polystyrene is the fourth biggest polymer produced in the world after polyethylene, polyvinyl chloride and polypropylene. Polystyrene – C8H8 – is a synthetic, thermoplastic, petroleum product. It is manufactured from a liquid hydrocarbon that is commercially manufactured from petroleum. Polystyrene is obtained by the polymerization1 of Styrene or Phenylethene. The chemical properties of Phenylethene are identical to Polyethene, which is the most common plastic. Polystyrene can be solid or foamed. 1 Polymerisation – a process in which individual molecules are linked to produce extremely large, multiple-unit molecules. In chemistry, it is defined as a process of combining several monomers to form a polymer. 1 Polystyrene (PS) can be divided into three varieties: General Purpose Polystyrene (GPPS), High-impact Polystyrene (HIPS) and Expanded polystyrene (EPS): 1) General Purpose Polystyrene (GPPS) GPPS is a transparent crystalloid with many specifications depending on its molecular weight. It is also known as Sheet or Molded Polystyrene. General purpose polystyrene is clear, hard, and rather brittle. Polystyrene is one of the most widely used plastics, the scale of its production being several billion kilograms per year. 2) High Impact Polystyrene (HIPS) General purpose polystyrene (GPPS) is a glasslike polymer with a high processability. When modified with rubber it results in a high impact polystyrene (HIPS) with a unique combination of characteristics, like toughness, gloss, durability and an excellent processability. Used in food service disposables and packaging, to name a few – Yogurt tubs, Salad bowls, Disposable knives, forks and spoons and in other displays and packaging - Refrigerator linings, CD Cases, Medical trays. 2 3) Polystyrene Foam (EPS) Polystyrene foams are good thermal insulators and are therefore often used as building insulation materials, such as in insulating concrete forms and structural insulated panel building systems. Grey polystyrene foam, incorporating graphite has superior insulation properties. They are also used for non-weight-bearing architectural structures (such as ornamental pillars). PS foams also exhibit good damping properties, therefore used widely in packaging. To make an EPS moulding product, first the PS resin is impregnated with a blowing agent (Pentane Gas) to allow pre-expansion to take place (Polymerization). It is then re-expanded using superheated steam in a batch pre-expander to the required expansion ratio (can be up to 50:1) before it is conditioned in the silos for aging. The aged pre-expanded material is next fed into a moulding machine with a dedicated tooling where steam is used to expand the material within the mould cavities into the desired shape. Finally the parts are dried in ovens before they are inspected and packed for delivery. 3 Polystyrene foam is the main form of Polystyrene that we are concerned with for our research and we will delve into it in detail from the next section onwards. 2. Polystyrene Foam – About the Material In 1941, The Dow Chemical Company manufactured and trademarked a brand of closed-cell extruded polystyrene foam made for thermal insulation and craft applications. They called it Styrofoam. In 1951, a German company, BASF successfully restructured the chemical bonding of polystyrene molecules and developed a substance named stretch polystyrene. This substance was named Thermocol. Its chemical formula is (C6H5CHCH2)n. So essentially, Thermocol and Styrofoam are both generic names for the same product – expanded polystyrene. Polystyrene foam can be further divided into two types 1) Extruded Polystyrene (Brand name: Styrofoam) Extruded polystyrene foam (XPS) consists of closed cells, offers improved surface roughness and higher stiffness and reduced thermal conductivity. Also called PSP Foam, it is also made from polystyrene resin (beads). The resin beads are put into an extruder that is heated, basically melting the beads. The extruded foam is then put into a “paper” roll and then molded into appropriate shape. Extruded polystyrene material is also used in crafts and model building, in particular architectural models. Because of the extrusion manufacturing process, XPS does not require facers to maintain its thermal or physical property performance. Thus, it makes a more uniform substitute for corrugated cardboard. The trademark ’Styrofoam’ by Dow Chemical Company is informally used for all foamed polystyrene products, although strictly it should only be 4 used for 'extruded closed-cell' polystyrene foams made by Dow Chemicals. 2) Expanded Polystyrene or Thermocol Expanded polystyrene (EPS) is a rigid and tough, closed-cell foam. It is usually white and made of pre-expanded polystyrene beads. EPS is used for many applications e.g. trays, plates, bowls and fish boxes. Other uses include molded sheets for building insulation and packing material ("peanuts") for cushioning fragile items inside boxes. Sheets are commonly packaged as rigid panels (size 4 by 8 or 2 by 8 feet in the United States), which are also known as "bead-board". EPS is made by combining the polystyrene and an physical foaming agent (usually pentane), and used to produce goblets, snack cases, insulated packaging, EPS is also made from polystyrene resin. In this case, the resin beads are expanded (due to steam) by 50 times in volume from PS resin size. Once the beads are expanded they are able to be molded into their intended shape. Difference between EPS or PSP Foam? The rule of thumb is if you can see the individual beads, then you have EPS. If the foam is smooth and you cannot see individual beads, then you most likely have PSP Foam. Usually, EPS is used for protective packaging, shipping containers (like coolers), and for construction products. PSP Foam (Styrofoam) is almost exclusively used for food products. 3. Manufacturing process of Thermocol 5 EPS is nowadays manufactured through a simple process. At room temperature, polystyrene is normally a solid thermoplastic, but can be melted at higher temperature for molding or extrusion, then resolidified. Styrene is an aromatic monomer, and polystyrene is an aromatic polymer. It is a rigid cellular plastic foam \material derived from petroleum and natural gas byproducts. The spherical beads of resin are subjected to steam, which causes the thermoplastic polystyrene to soften and expand up to 40 times its original volume. Each small bead of polystyrene is fully sealed. Watch this video to see the manufacturing process. An accidental discovery by American Chemist, Dr Baekeland: Foaming plastics were discovered indirectly, because in the beginning no one could see their advantages. Dr. Leo H. Baekeland, the American chemist who developed the first completely synthetic plastic, bakelite, experimented with phenol (an acidic c\\ompound) and formaldehyde (a colorless gas) while trying to make a nonporous resin. When one of his mixtures unexpectedly began to foam, Baekeland tried to control the foam before realizing that it could have advantages. Following Baekeland's death in 1944, the first foamed phenolics were developed, soon followed by epoxy foam. A short time later, polystyrene was foamed. Raw Materials for the production of Thermocol ● main component is styrene (C 8 H 8 ) ● which is derived from petroleum or natural gas ● and formed by a reaction between ethylene (C 2 H 4 ) ● and benzene (C 6 H 6 ); benzene is produced from coal or synthesized from petroleum The process (Summarized) Styrene is polymerized either by heat or by an initiator such as benzoyl peroxide. Stopping the polymerization is difficult; however, inhibitors such as oxygen, sulfur, or quinol can be used. To form the low-density, loosely attached cells EPF is noted for, polystyrene must first be suspended in water to form droplets. A suspension agent, such as specially precipitated barium sulfate or copolymers of acrylic and methacrylic acid and their esters (organic product formed by the reaction between of an acid and an alcohol), is then added to the water. Numerous suspension agents are used commercially. All are similarly viscous and serve to hold up the droplets, preventing them from sticking together.