Applications of polymers in everyday life
- 1. 1 APPLICATIONS OF POLYMERS 1. Uses of Polymers in Agriculture 1.1 Functionalized Polymers in Agriculture Synthetic polymers play important role in agricultural uses as structural materials for creating a climate beneficial to plant growth e.g. mulches, shelters or green houses; for fumigation and irrigation, in transporting and controlling water distribution. However, the principal requirement in the polymers used in these applications is concerned with their physical properties; such as transmission, stability, permeability or weatherability; as inert materials rather than as active molecules. During the last few years, the science and technology of reactive functionalized polymers have received considerable interest as one of the most exciting areas of polymer chemistry for the production of improved materials. They have found widespread applications as reactive materials based on the potential advantages of the specific active functional groups and the characteristic properties of the polymeric molecules. Their successful utilizations are quite broad including a variety of fields, such as solid-phase synthesis, biologically active systems and other various technological uses. 1.2 Super Absorbent polymers Super Absorbent Polymers, also known as SAP, hydrogel, absorbent polymers, absorbent gels, super soakers, super slurpers, water gel, is a new type of macro molecular synthetic water absorbing polymer material. It has a water uptake potential as high as 100,000% of its own weight in a short period of time by osmosis and form granules in soil to enhance soil properties. SAPs are generally white sugar-like hygroscopic materials that swell in water to form a clear gel made of separate individual particles and can retain moisture even under pressure without risk of conflagration or rupturing/blasting. Super Absorbent Polymers used in agriculture are mostly prepared from acrylic acids and a cross-linking agent like potassium by solution or suspension polymerization. The polymer so formed is called a polyacrylate whose swelling capacity and gel modulus depends greatly on the quantity and type of cross-linker used. Polyacrylates are non-toxic, non-irritating and non- corrosive in nature and tested to be biodegradable with a degradation rate of 10%-15% per year. They demonstrate high water absorbance potential and can freely release 95% of the same under suction pressure by plant roots.
- 2. 2 Fig 1.1 Super absorbant polymer- hydrogel 1.3 Polymers for soil remediation Contamination of soils with toxic metal elements is of great concern to scientists and the general public. Long-term intake of contaminant metals by humans may lead to chronic effects. Effects of metals on ecosystems and biological resources are also increasingly recognized. Metals do not degrade as organic compounds do, and have long residence times in soils. They can however exist in different forms, which include water-soluble (ionic and chelated with soluble compounds), adsorbed on soil surfaces, chelated by insoluble organic matter, precipitated, occluded by soil oxides and hydroxides, present in living organisms or residues, and as part of primary and secondary minerals. Conventional remedial approaches to severely metal-contaminated soils involve removal and replacement of soil with clean materials or capping the soil with an impermeable layer to reduce exposure to contaminants, chelating agent ethylenediaminetetraacetic acid (EDTA) has been used extensively for heavy metals extraction from soil. Water-soluble polymers (WSP) have been used extensively for the removal or recovery of metal ions from aqueous solutions. Polyethylenimine (PEI), a highly branched aliphatic polyamine, was chosen as the backbone polymer for the studies on lead extraction from soil. PEI is readily functionalized with chloroacetic acid to give aminocarboxylate groups which are known to chelate lead effectively. 1.4 Biodegradable Polymers in Agriculture Biodegradable polymers have increasingly been used as plastics substitutes for several applications in agriculture. One of the problems afflicting agricultural production is the presence of parasites in the soil that, along with spontaneous weeds, take away nourishment from the soil. In the past the elimination of parasites and seeds of undesirable plants, before a
- 3. 3 new sowing, was performed through fumigation with methyl bromide, which has been indefinitely banned for its toxicity. The optical properties are important because during the day, visible radiation, which passes through the film, warms the soil. During the night, when the soil cools by emitting infrared radiation, the film which is impermeable to infrared radiation, traps it and thus prevents heat loss. Actually, a film with these optical properties has a micro-greenhouse effect on the soil. This technique is largely used today, particularly at those latitudes with temperate climate. It makes use of low-density polyethylene with fillers, such as phosphates, that increase the opacity to infrared radiation. Solarization guarantees the decontamination of soils assigned to insemination within 4-6 weeks. At the end of the treatment, the problem of the removal and disposal of films has to be resolved. Films made of synthetic polymers should be treated as waste with additional costs. A biodegradable film made of natural polymers, for solarization offers advantage that it does not have to be removed from the soil after they are used. Polymer films for solarization containing alginates, polyvinyl alcohol and glycerol has been reported. Alginates are water soluble linear copolymer, containing agluronic and mannuronic acid units, present in seaweed. Fig 1.2 Biodegradable Mulch film
- 4. 4 2. Use of Polymers in Sports 2.1 Synthetic Turf The original construction of a synthetic grass surface comprised a stone sub-base, a macadam base, a foam shock pad layer and the synthetic carpet. The carpet is a knitted or tufted, three- dimensional fabric in which the ‘grass blades’ are incorporated into the fabric structure, approximately perpendicular to the fabric backing. In a knitted carpet the filaments forming the turf and the backing yarns are interlaced in a single production step. With tufting, a separate woven fabric acts as a substrate into which the turf filaments are inserted and fixed with a latex backing. Synthetic grass has been made from nylon, polyolefins or polyester, normally as extruded monofilaments. Variations in the dimensions and characteristics of the individual filaments, the pile density and its angle to the base have been used to significantly vary properties such as friction and ball roll. However, in sand-filled constructions most of such effects are masked. Contrasting colour carpet can be inserted to form permanent line markings. Needlepunch carpet has been successfully used for such sports as bowls and could be considered as very short and fine synthetic turf. Fig 2.1 Synthetic turf 2.2 Athletics Track Polymeric track construction can be solid cast rubber, resin bound rubber crumb or shred, or prefabricated rubber sheet. Outside tracks are generally laid on a macadam base. The original systems were cast rubber, either polyurethane or a natural rubber or polychloroprene latex, with a dressing of rubber chips or granules. They have particularly good wear resistance but are impermeable. Tracks have also been constructed from prefabricated sheets of a number of polymers including styrene butadiene rubber, polychloroprene and polyvinyl chloride. These are mostly used for indoor installations where an uneven base is likely to cause fewer problems.
- 5. 5 Fig 2.2 Athletics Track 2.3 Clothing The fire resistant Nomex fabric is used in underwear, balaclavas, gloves, boots and race suits for motorsports. A combination of Kevlar, silicone gel and closed-cell foam has been used in knee pads for mechanics and Kevlar heat sleeves can protect them when working on hot engines. Protective helmets used in motorsports, cycling and horse riding activities are made from thermoplastics or reinforced plastics. In a number of sports there is need for goggles, visors or face masks. These utilise such materials as polycarbonate for the lenses. A variety of polymers are used in sports footwear. Trainers commonly have a rubber outsole, which may be multicoloured or include clear thermoplastic elements. Common materials for midsoles are cellular ethylene vinyl acetate and polyurethane, and there can be inserts such as polyurethane air bags and torsion bars made from thermoplastics or even carbon fibre reinforced polyester. Uppers are often made from polyvinyl chloride coated fabrics and there can be additional components such as Goretex linings, foam cushioning and polyurethane heel supports. Shoes for such sports as football and running have semi-rigid soles made from such materials as thermoplastic polyurethane. Fig 2.3 Football shoes Fig 2.4 Sports goggles 2.4 Equipment The construction of the three-part golf ball is a complicated process; polyisoprene thread is wound over a small solid rubber core and the cover formed from balata or Surlyn. The solid or two-part ball has a solid rubber core with a Surlyn cover and can be compression or
- 6. 6 injection moulded. One-part balls can be of rubber, polyurethane or Surlyn but the optimum performance characteristics cannot be achieved by this construction and they are used by beginners to practice and on driving ranges. Tennis balls also require specialised production techniques and are again regulated by a specification. The bounce characteristics of pressurised tennis balls are dependent on the internal pressure, which is typically 100 kPa above atmospheric. As air permeates out, the pressure drops and the playing characteristics change. The loss can be reduced by filling with a gas that permeates more slowly than air or by using an elastomer with lower permeability. Special containers manufactured from such materials as acrylonitrile-butadiene-styrene are produced to maintain the pressure of gas-filled balls. Unpressurised balls rely on the material which forms the wall (such as butadiene) to provide the necessary resilience. Titanium has been added to the rubber compound to improve performance. Football balls are made from polyvinyl chloride, ethylene vinyl acetate or polyurethane. Balls for basketball, handball and softball are essentially similar to those for football. A polymeric coating on high-class rugby balls enhances the grip in wet conditions. Shuttlecocks are used in roughly the same way as a ball. A method of making plastic shuttlecocks by an advanced injection process whereby the polyamide skirt is fully formed in the mould has been reported and which is claimed to yield a product closer to the traditional hand-built feather designs than hitherto. Tennis and squash racquets have been revolutionised by polymers with the introduction of advanced composites. The earlier rackets used glass fibre reinforced polyester but now more advanced composites with carbon, aramid and boron fibres have been introduced with high modulus carbon fibre being standard. The advantages are based on the stiffness to weight ratio and the control of the racket’s characteristics which can be achieved through geometry of the reinforcement. Also, composites have better fatigue resistance and higher damping. Other parts of the racket also utilise polymers: polyamide bumper guards, polyamide and polyester strings and rubber grips. Fig 2.5 Tennis kit Fig 2.6 Golf Ball
- 7. 7 3. Uses of Polymer in Household 3.1 Polyvinylchloride It is commonly used for water pipes and is able to withstand large amounts of pressure. Other applications for polyvinyl chloride are door frames, waterproof fabric, electrical wire insulation, door, roof sheet, floor tiles, wall lining, hoses, etc. 3.2 High Density Polyethylene It is used in bottles, pipes, inner insulation (dielectric) of coax cable 3.3 Polyacrylamides Polyacrylamides are used in water purifiers. 3.4 Low Density Polyethylene They are used in Squeeze bottles, toys, flexible pipes, insulation cover (electric wires). 3.5 Polypropylene Poplypropylene can be used in luggage, stacking chairs, parts of washing machine etc. 3.6 Polystyrene The articles made from polystyrene are drinking cups, computer cabinet, small jars, switches, knobs, hair drier, toys etc. 3.7 Poly methyl methacrylate It is used for ceiling lightings, transparent roof shadings. 3.8 Polyethylene Terephthalate
- 8. 8 It is used in making water bottles, decorative items, containers, electrical capacitors etc. Fig 3.1 PET containers 3.9 Polyurethane It is used for making bath room accessories, wire and cable jackets etc. 3.10 Phenol formaldehyde resin It is used in Insulation of wires, manufacturing sockets, electrical devices, etc. 3.11 Polytetrafluoroethylene(PTFE) It is used for making non-stick pans. Fig 3.2 Household plastic articles Fig 3.3 Non-stick pan
- 9. 9 4. Uses of polymers in medical field 4.1 Packaging of drugs and devices Plastic ampullas and prefilled syringes are convenient to use, but adsorption and migration of the bioactive substance into the polymer, pH shifts, oxygen permeation, optical properties and the release of leachable components have to be considered carefully for the individual applications. The interaction may affect not only the drug, but also the function of the polymer container. Polyolefins, HDPE or PP are the most frequent polymer for compressible vials, but frequently also multilayer containers are used to achieve required properties of inertness, oxygen- or UV protection. For prefilled polymer syringes, cyclic olefin polymers and copolymers found wide application due to their mechanical and optical properties, inertness and stability at steam sterilization; the stopper and the tip cap are usually made of elastomers. PVC containing the phthalate plasticizer DEHP is used for many extracorporeal perfusion tubes to provide medicines, or also in blood leading tubes in extracorporeal dialysis or extracorporeal oxygenation. In reaction to the phthalate concerns, alternative plasticizers partly are applied for storage of red blood cells, such as butyryl-trihexyl-citrate (BTHC) or di-iso-nonyl-1,2-cyclohexanedicarboxylate (DINCH). For platelet storage, also alternative polymers like polyolefins are used, and polyethylene and polyurethanes are used for tubings. The tubings of the peristaltic pumps are typically made of silica. Fig 4.1 Syringe 4.2 Haemodialysis Membranes Hemodialysis membranes are produced as bundles of hollow fibers with a blood contacting surface of 1.0–1.5 m2 . Synthetic membranes mainly are composed of a hydrophobic base material and hydrophilic components; the co-precipitation membranes of polyarylsulfones, polysulfone (PSf) and polyvinylpyrrolidone (PVP) are most prominent. But also multiple other membrane materials are used, such as polyamide (PA), polycarbonate (PC), and polyacrylonitrile (PAN), PMMA, polyester polymer alloy (PEPA), ethylene vinyl alcohol copolymer (EVAL), and molecular-thin nanoporous silicon membranes. The hydrophilic component PVP or poly(ethylene glycol) (PEG) in the membrane is pore-forming agent and also improves antifouling properties and blood compatibility.
- 10. 10 4.3 Suture Materials Degradable biological suture materials are collagen based materials, catgut; non-degradable bio-polymers are silk or cellulose (cotton). Synthetic resorbable materials are PGA, polyglactic acid (Vicryl), PDS, poliglecaprone 25 (Monocryl); non-resorbable suture materials are nylon, polyethylene, polypropylene (Prolene), polyester, polybutester, and Polyvinylidenfluorid (PVDF). Generally fast healing tissue, such as peritoneum and inner organs is treated with resorbable suture material, whereas slow-healing tissue and tissue with high mechanical exposure, such as skin or tendons, are treated with non-resorbable material. The biological degradable materials degrade by proteolysis with significant tissue response, whereas hydrolytically degrading synthetic polymers show less tissue response. Also for the non-resorbable suture materials, the biopolymers silk or cotton cause more intense inflammation than the synthetic polymers. Fig 4.2 Types of suture materials
- 11. 11 4.4 Surgical Meshes Reconstructive meshes in general surgery support organs or tissue to prevent a prolapse or hernia. The main classifications of the surgical meshes are according to the mash size or the weight of the mesh, because this is more relevant for the biological response than the material. The main polymers for non-resorbable meshes are expanded PP, ePTFE, PET or PVDF, however, also they show significant signs of degradation at the surface and even fragmentation. Among these materials PVDF meshes usually induce less foreign body response than PP meshes do. Large pores (<1 mm) generally show less inflammation and bridging scare formation than small pores do. Fig 4.3 Surgical Mesh 4.5 Joint Prostheses In orthopedic surgery, joint prostheses most frequently have a pairing of metal on UHMWPE (ultrahigh molecular weight polyethylene). UHMWPE is a semi-crystalline polymer with superior strength, creep- and wear resistance; however, it still is the weaker component of the pairing due to wear, oxidation and fatigue fractures. Long lived free radicals in the polymer induced by gamma sterilization caused significant ageing of the UHMWPE devices upon storage in oxygen containing ambience. While other means of sterilization are possible, gamma sterilization is generally preferred, because it induces crosslinking and improves the mechanical stability of the polymer. This highly crosslinked PE is referred to as HXPE. Antioxidants, like vitamin E are added to the UHMWPE to quench free radicals and improve mechanical properties as a plasticizer. In small joint replacement flexible silicon spacers dominate. However, inorganic pyrolytic carbon (Pyrocarbon) with graphite-like structure finds increasing attention for small joints or as interposition material because of its inertness, low friction behaviour and a Young׳s modulus close to bone. Fig 4.4 Joint Prosthesis
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