ELASTOMERSRubbers, in other words elastomers, are compatible and soft polymer type. They canrecycle and experience big deformations. This sort of elasticity is found just in long chainpolymers. One property of elastomers is that they are network polymers that have cross-linking density less than thermosets.Elastomers have a long history. They have played an important role in theindustrilization. At the beginning of 1920’s, England Thomas Hancock fabricated a machinein order the chew the natural rubber. So it means that the purpose is to obtain a materialconsistency that can enhance process capability. This technique is called mastication and thisprocedure is still using.Another chemical process which named vulcanization, synthetic or natural rubber’sphysical properties are improved; worked rubber has more resistance and tensile strength8to abrasion and swelling also, it is elastic over with bigger range of temperatures. Withheating sulfur with rubber, vulcanization is brought.In 1839, the U.S. inventor Charles Goodyear discovered the vulcanization. Such amaterial causes vulcanization to advance at lower temperatures or more faster. Rubber andsulfur reactions are not understood completely, however in the product, the sulfur does notdispersed or dissolved in the rubber; between the long-chain molecules, bridges, or mostlyin the form of cross-links it is chemically combined.At electrial and thermal insulators, ashesives, noise and vibration absorbers, springs,tires, seals elastomers are generally used. Rubber metarials have large extensibility and highdamping. Also, under cyclic loading, they have low thermal conductivity and show significantdelay.There are two sections in elastomers:-natural rubber- synthetic rubberAlso, the other important issue is that figure; increase in stiffness of strain for threesection of rubber: hard rubber, vulcanized rubber and natural rubber. Now, we are going tolook the differences between vulcanized and natural rubber:Natural rubber Vulcanized rubbersticky and soft. hard and non-sticky.low tensile strength. high tensile strength.low elasticity. high elasticity.9narrow range of temperature wide range of temperature.low wear and tear resistance. high wear and tear resistance.soluble in solventslike ether, carbon, tetrachloride, petrol, etc.insoluble in all the common solvents.Natural Rubber:Natural rubber is obtained from tropicalrubber tree. Also, it is known as latex. It is anadditional polymer obtained as a milky whiteliquid. Natural rubber is a monomer isoprenejoined diene hydrocarbon.When sulfur and rubber are mixed, thecharacteristics of the rubber advanced inincreased in elasticity, resistant to heat and coldand being tougher. This process is know asvulcanization. Throug the sülfür, shorter chains have cross link caused by vulcanization tolonger chains. Because of the growth vulcanized rubber automobile tires supported thisindustry.Synthetic Rubber:Synthetic rubbers include isoprene, 1,3-butadiene, and chloroprene. During WorldWar II, synthetic rubbers were progressedwhen necessary supplies of natural rubberwere seperated. It can be vulcanized.Synthetic rubber is more resistant to oxidationand abrasion than NRP. SBR is utilized in tire production. In the unvulcanized form, a littleamount is utilized for bubble-gum.The types of synthetic rubber are;? Acrylic Rubber (ACM)It is a type of synthetic rubber including acrylonitrile. Alkyl acrylate copolymer is thechemical name. ACM is widely utilized in hoses and automotive transmissions.? Butadiene Rubber (BR)The chemical name of this rubber is Polybutadiene. This rubber is the second largestvolume synthetic rubber generated.? Butyl Rubber (IIR)10Also known as polyisobutylene, the first major use of this was Tire innertubes, andthis continues to be a significant market today.? Chlorosulfonated Polyethylene (CSM)/ HypalonChlorosulfonated polyethylene or CSM is a synthetic rubber based on polyethylene.Chlorosulfonated polyethylene is used in a variety of industrial and automotive applicationsthat have to withstand extreme weather conditions. and require high performance? Ethylene Propylene Diene Monomer (EPDM)EPDM is one of the most popular types of synthetic rubber. It is an elastomer- ahigh-density rubber that is very durable and has a wide range of applications.? Fluoroelastomers (FKM)/ VitonFKM is a class of synthetic rubber designed for very high temperature operation.FKM provides extraordinary levels of resistance to chemicals, heat and oil.? Isoprene Rubber (IR)The isoprene rubber is very much like natural rubber but made artificially orsynthetically. This rubber is used in the same type of products as natural rubber.? Nitrile Rubber (NBR)Nitrile Rubber is a synthetic rubber produced by polymerization of acrylonitrilewith butadiene. ? Perfluoroelastomer (FFKM)Perfluoroelastomers are a type of synthetic rubber having even greater heatand chemical resistance than the fluoroelastomers. Perfluoroelastomers are widely used asseals on semiconductor wafer processing equipment. The basic disadvantages of this rubberare difficult processing, very high cost, poor physical properties at high temperature, andtheir high glass transition temperatures which limit their use at low temperatures.? Polychloroprene (CR)/ NeoprenePolychloroprene rubber has a perfect balance of mechanical properties andfatigue resistance which is second only to natural rubber. Neoprene rubber also has superioroil, chemical and heat resistance. This type of rubber is widely used in general engineeringapplications.? Silicone Rubber (SiR)Silicone rubber is the most commonly used synthetic ruuber or polymer. Thecharacteristic of silicone rubber is such that it provides the perfect balance of mechanical11and chemical properties that is required in today's most demanding industrial rubberapplications.? Styrene Butadiene Rubber (SBR)These rubber is considered to be the highest volume general purpose andthe most common type of synthetic rubber.POLYMER RECYCLING AND BIODEGRADABILITYPolymer RecyclingIt is an option to decrease environmental troubles caused by polymeric waste savingcreated from day to day practices of polymer materials such construction and packing. Sincepolymer materials’ are often created from gas and oil, the recycling of polymeric waste aidsto protect natural resources.Stages in Plastic RecyclingThere is five different stages, before the plastic recycling starts:Sorting: It is important for all plastic product is separated according to its type it can beoparated accordingly in the shredding machine.Washing: Once the sorting has done, the waste of plastic wants to be washed to removeimpurities like adhesives. This improves the quality of the completed item.Shredding: After washing part, the waste is going into different conveyer belts which run thewaste via the different shredders. These shredders preparing them for recycling and tear upthe plastic into small pellets, into other products.Identification and Classification of Plastic: After shredding, a proper testing of the plasticpellets is conducted to ascertain their quality and class.Extruding: This involves melting the plastic so, it can be extruded into pellets, then utilizedfor making different types of plastic products.Processes of Plastic RecyclingThis two processes are the most popular in the industry.? Heat Compression: It takes plastic waste which is unsorted and cleaned then, mixesit in huge tumblers which churn the entire mixture. The main advantage of thisprocess ; it does not require matching forms of plastic to be recycled together.? Monomer: Through the accurate and elaborate monomer recycling process, mainchallenges of plastic recycling can be overcome. This process reverses the12polymerization reaction for recycling the same type of condensed polymer. Thisprocess is not only purifies but also cleans the waste to create a new polymer.Benefits of Plastic RecyclingTwo of the benefits of plastic recycling are:? There’s A Ton of Plastic: One of the biggest reasons for recycling plastic is its hugequantity. This will not help increase the plastic production however it takes care ofthe environment.? Conservation of Energy and Natural Resources: The recycling of plastic helps save alot of natural resources and energy . Saving water, petroleum, and other naturalresources help conserve the balance in nature.Polymer BiodegrabilityBiodegradable polymers are described as polymers that have unstable contacts in thebackbone and they are contained of monomers connected to one another via functionalgroups. They are demolished into biologically admissible molecules removed andmetabolized from the body through normal metabolic ways. Based on biodegrabilitypolymers are graded as:1.Biodegradable polymersFor example: collagen, poly glycolic acid etc…2.Non biodegradable polymersFor example: poly vinyl chloride, polyethylene etc…The examples of biodegradable polymers are polyglycolic acid(PGA), Polyhydroxybutyrate (PHB), Polyhydroxy butyrates-co- beta hydroxyl valerate( PHBV),Polycaprolactone(pcl), Nylon-2- nylon-6.These polymers are used majorly for medical products such as surgical sutures, tissues ingrowth materials, for controlled drug release,plasma substitutes etc.They are also used in agriculturematerials,such as films,seed coatings,fast food wrappers,personal hygiene products etc.Poly-?-hydroxybutyrate-CO-?- hydroxyvalerate (PHBV) is a biodegradable polyester.