German Chemist Hans von Pechmann first synthesized Polyethylene by accident in 1898 by heating diazomethane. His colleagues characterized the waxy substance polyethylene due to the fact that they recognized that it consisted of long ethene chains. It was then first industrially synthesized by accident in 1933 by applying extremely high pressure to ethylene and benzaldehyde. Over the years, development of polyethylene has increased due to the additions of catalyst. This makes ethylene polymerization possible at lower temperatures and pressures.1
Polyethylene is a polymer that is made of a long chain of CH2 monomers bonded together. It is one of the most commonly used polymers in everyday items. Grocery bags, soap bottles, children’s toys, and even bullet proof vests are all made from polyethylene.2 This polymer is very versatile and can be used in many materials but this all depends on the way that the polymer is chemically made or enhanced. There are many different types of polyethylene classified by density and branching. 2
Higher density polyethylene is very linear and has no branching. Lower density polyethylene is a result of some of the carbon atoms bonding with other polyethylene
chains instead of hydrogen atoms. Cross-linking is another way in which the polymer can be made stronger. This involves ultraviolet radiation that bombards the polymer with electrons and formulates bonds between the molecular chains of the polymers. This is like linear polyethylene but different in that it is more impact resistant, and it has a much higher density. This allows it to be stored or be used with different chemicals that would normally cause the polymer to desolve.3 This can start to become a problem because as the polymer continues to become chemically enhanced. So the ways of dissolving and recycling the polymer become more difficult.
Other alterations such as dying the polymer are less cost efficient to recycle and can be more difficult as well. There are certain types of HDPE (high density polyethylene) that are blown into shapes such as bottles. Different chemicals are used in this process and therefore have to be separated into their own category when recycling. The reason people have moved away from landfill dumping and moved towards recycling is due to the fact that it is much more cost effective to recycle compared to paying engineers and environmentalist to designing landfills.4 The HDPE can also be mechanically recycled through curb side pick ups.
In this essay, the author
- Explains that people have moved away from landfill dumping and moved towards recycling because it is much more cost effective than paying engineers and environmentalists to design landfills.
- Explains that many people don't recycle polyethylene because it's cheap to make and does not biodegrade.
- Opines that the recycling of polyethylene is increasing and more people are becoming aware of the problem that it posses today.
- Describes juliet lapidos' thoughts on the future of plastic bags.
- Explains that the waxy substance polyethylene was first synthesized by accident in 1898 by heating diazomethane.
- Explains how polymers are recycled and what are the end products of the recycling process. many stores around california are starting to accept bags made from ldpe.
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- Polyethylene Research Paperexplanatory essayThe synthesis of polymers starts with ethylene, (or ethene). Ethylene is obtained as a by-product of petrol refining from crude oil or by dehydration of ethanol. Ethylene molecules compose of two methylene units (CH2) linked together by a double carbon
In this essay, the author
- Explains that polyethylene terephthalate (pet) is a polymer commonly used in plastic bottles. the chemical formula for pet is (c10h8o4)n) compiled by monomers of ethylene glycol or 1,2-ethanedio
- Describes condensation polymerisation, where a carboxylic acid is reacted with an alcohol to produce an ester and water.
- Explains the chemical formula for polyethylene, which is –(ch2-ch2)n– for both hdpe and ldpe.
- Explains the chemical formula for polytetrafluoroethylene, which is produced by heating chlorodifluoromethane (chclf2) at temperatures around 600 to 700 degrees celsius.
- Explains that polyvinyl chloride (pvc) has a chemical formula of –(ch2-chcl)n.
- Explains that the isotactic polyvinyl chloride structure is produced very little, while the syndiotic pvc has similar properties of flexibility, rigidity, and strength.
- Explains that nylon 6,6 is synthesised by the condensation polymerisation reaction of 1,6-dihexanoic acid (adipic acid) and 1'-diaminohexane.
1165 wordsRead More - Stainless Steel Essayexplanatory essayPolymer-Polyethylene is partially crystalline as well as amorphous because it has crystalline and amorphous regions. Also it has linear chains so this is the simplest structure compared to a branched or network chain. This can be of an advantage to it over other types of materials as its good toughness and elongation makes it very significant in the engineering industry as it can be moulded or extruded into shape...
In this essay, the author
- Explains that stainless steel has a strong lattice structure that makes it more suited to engineering applications such as tools, engines, electrical motors, and hydraulic systems.
- Explains that polymer-polyethylene is partially crystalline and amorphous. it can be moulded or extruded into shapes such as pipes.
- Explains the properties of alumina, such as strength, corrosion resistance and wear resistance, which makes it important in engineering. aluminium oxide is the second hardest mineral after diamond and is non-reactive.
- Explains that carbon-fibre is made up of layers of fibrous composite materials, bonded together in minuscule crystals, and has a high strength to weight ratio.
- Explains that nitinol is an alloy of nickel and titanium. it can be used in engines and couplings in aerospace applications due to its useful properties.
1180 wordsRead More - Chemistry of PNA Peptide Nucleic Acidexplanatory essayvery special polymer that is unique in its characteristics, functions, and use in the modern
In this essay, the author
- Explains that the molecule is stable over a wide ph range, and does not degrade by degrading.
- Opines that the delivery of such new strands needs a vector, or transporter of genetic.
- Explains that messenger rna (mrna) can still inhibit various processes of the body.
- Opines that pna will be used in a more regulated manner in the future.
- Opines that though it is only a subtopic of gene therapy, it's bound to summary:
- Opines that gene therapy can make its way onto the big screen in just a few years.
- Explains that they chose to study pna, or peptide nucleic acid, a biological polymer that was related to the biomedical field of research.
- Explains that their main goal was to learn about the structure, significance, and clinical uses of ribonucleic acid.
- Explains that peptide nucleic acid, or pna, is a polymer that is similar to dna and can bind with high specificity to target genes.
- Explains that peptide nucleic acid is a very special polymer that is unique in its characteristics, functions, and use in the modern world.
- Explains that archiral nucleic acids can be synthesized without stereoselective reactions, where one reactant is favored over another.
- Explains that pna as a vector is one of the few ways to carry out targeted gene delivery.
- Explains that gene therapy is the new and improved pattern for treating diseases found in humans.
- Explains that an antisense molecule is a nucleotide sequence, either dna or rna or an analogous form of the two, that modifies genes.
- Explains that pna has been used in the evaluation of genetically modified content in foods.
1435 wordsRead More - Essay On Polyesterexplanatory essayAfter this compound is formed, then comes the polymerisation stage1. In the polymerisation stage the compound that is produced is heated at a temperature of 260oC and at a low pressure1. A catalyst is required at this stage to speed up the reaction - there are many options for catalysts such as antimony (iii) oxide1. After this step the polyester is formed and half of the ethane1,2- diol is restored which is removed1.
In this essay, the author
- Explains the two basic forms of polyester produced are filament yarn and staple fiber2.
- Explains that adding a delusterant to the polyester fiber would make the fiber lose its brightness.
- Explains that by changing the spinneret shape different shapes of fibers can be obtained, like square, oval, triangle, and even bean shaped.
- Explains that the polyester fiber can be stretched more than five times its original length, creating a now popular fiber called microfiber3. drawing it out more would affect elasticity, strength and tenacity of the fiber3.
- Explains that polyester’s original color is transparent off white but this can be changed by adding a color dye in the manufacturing stage3. this would make the fiber more attractive and change its appearance.
- Explains the process of heat setting, which gives the fabric a permanent shape3.
- Explains singing is a process to remove extra, unnecessary fiber from the fabric by quickly passing in over fire.
- Explains that water and stain repellency make it easier to clean the fabric and also makes it more comfortable3.
- Explains that after the fabric is produced a coating of resin is applied to it and it permanently retains the shape it is pressed into4.
- Explains that calendering is a process in which the fabric is passed between two huge rollers which apply huge pressure over it.
- Explains that embossing is a process of creating an attractive design over the fabric. the fabric is passed between two huge rollers.
- Explains that polyester and cotton are one of the standard blends3. the polyester keeps the fabric in shape and also makes it resistant to stains and wrinkles.
- Explains that polyester with wool makes the fabric resistant to wrinkles and helps it retain its shape3.
- Explains that polyester and rayon are another blending combination3. the polyester fabric is cut into 2 inch pieces when it is blended with rayon2.
- Opines that the combination of nylon and nylon produces a strong, durable, and stable fabric, but it has its drawbacks, as neither is absorbent, so the fabric may feel wet in hot weather3.
- Explains polyesters - terylene and pet.
- Explains how polyester is made, n.p., is available at madehow.com.
- Explains that polyester is an example of condensation polymerisation, which is formed by joining molecules together and loosening a small molecule such as water.
- Explains the process of polymerization, which results in a monomer alcohol which is combined with terephthalic acid at 280 oc2.
- Explains that crimping can give the fiber a nice texture and increase its insulation properties and its elasticity. winding is the process of forming yarn, which is then wound to large rolls and woven into fabric.
- Explains the process of polymerization, drying, and melt spinning to produce staple fiber, which is produced in a rope like bundles of polyester.
1248 wordsRead More - Recycling And Recycling Of Recyclingexplanatory essayRecycling is the process by which a waste material is converted again into reusable process and disposal is a process by which we get rid of something. Polymers are not very reactive so this property makes them very useable for storing food but this property makes it difficult to recycle or dispose of polymer. This difficulty in recycling and disposing of polymer is a major cause of environment hazard. Since the waste of polymer is increasing day by day so proper measurement should be taken to reduce the use of polymer and different method should be made to properly dispose and recycle waste. Following are the process by which a polymer is recycled or disposed.
In this essay, the author
- Explains recycling is the process by which a waste material is converted again into reusable process and disposal is disposed of. polymers are not very reactive, which makes them useable for storing food, but this property makes it difficult to recycle or dispose of polymer.
- Opines that we can reduce the use of polymer by simple source reduction stop making unnecessary packaging.
- Explains that the use of an alternative material is not very easy, since it requires proper implication of agriculture to meet desire need and use more energy consumption.
- Explains that landfill is a useful process of disposal of waste products which cannot be reused. it makes land less available for agriculture.
- Explains that landfills emit dangerous gases such as carbon dioxide and methane, which are flame-able and explosive. they also cause different types of infection, noise and land pollution.
- Explains that incineration reduces the mass of waste by 85% and requires minimum space for landfills. the energy produced by burning waste material can be used to generate electricity and heat the waste.
- Explains that the incineration process is not suitable for all polymers because it produces hcl acid fumes which are dangerous and cause acid rain.
- Explains that biodegradation is the technology in which a material is consumed by bacteria or other biological means.
- Argues that the modification of polymer to increase the degradable rate may cause them to consume in normal condition.
- Explains that biodegradable polymer adds to compost material and a lot of studies are in progress to make this process efficient.
- Explains that non-polymer material is lost and a proper infrastructure is required to remove non degradable material.
- Explains recycling is the process in which a material is reprocessed and became able to reuse.
- Explains that recycling of industrial product of polymer is very simple because it only contains one type of material. the waste treatment solution is dispose in oceans or in lands by digging hole cause a lot of diseases to marine and human beings.
- Explains that recycling is environmentally friendly and reduces the amount of trash that is disposed in landfills. it is also energy friendly because some products require less energy to reproduce.
- Explains that the process of recycling is costly and if the polymer contains other type of material then it can contaminate the whole melted batch. the recycling sites are unhygienic and spreading disease and other harmful chemical and waste.
- Explains that by hydrolysis and pyrolysis polymer may be degraded to lower molecular weight and by filtration they are separated from non-polymer.
- Explains that junk automobiles contain 12% to 13% of polymer material of their weight, so they have to be recycled in order to recover it.
- Explains that post-consumer recycling is difficult than industrial recycling. recycling of consumer products involves collection of recycled material from different bins and collection centers and they are sent for processing.
1317 wordsRead More - The Evolution Of Plastics: The Evolution Of Plasticsargumentative essayPlastic, like most inventions, was accidentally invented. Charles Goodyear was a perfect example of how things accidently started. He started the process of making plastic by dropping India-rubber mixed with sulfur on a hot stove. The in the late 1930s, chemist Wallace Carruthers invented nylon, which is a synthetic polymer. Polymers have a high melting and boiling point. Synthetic polymers are also known by the word we use today, plastic. The evolution of plastic started during World War II. Ever since then, plastic has been remolded and created to be used for our convenience in our everyday lives. For example, using a plastic cup or plate is more convenient than using a glass cup or bowl. People encounter many different types of plastic each day and may not be aware of it. In fact, during the first two hours of a typical morning, a female college student might encounter the following products which contain plastics: her alarm clock, mirror frame, the tape used to hang her posters, the toilet seat, the shower curtains, her deodorant, her toothbrush, her shampoo and conditioner bottles, her blow dryer, the light switch, bottled water, her refrigerator, a bread bag, her roommate's glasses, her fan, and phone.
In this essay, the author
- Explains that phthalates are used as plasticizers in the manufacture of vinyl flooring and wall coverings, food packaging, and medical devices.
- Explains that plastic is harmful to humans, animals, and sea creatures, because of the lack of recycling. animals mistakenly eat these plastics for food, causing cadmium and mercury poisoning.
- Explains that reducing the use of plastic can help with the health and environmental issues with plastic.
- Analyzes how charles goodyear invented plastic by dropping india-rubber mixed with sulfur on a hot stove, and wallace carruthers invented nylon, which is also known by the word we use today.
- Explains that plastic provides convenience, efficiency, and flexibility to consumers and manufacturers, but it is becoming a problem for the environment. the negative effect of plastic use worldwide outweighs the positives.
- Explains that plastic is economical because it can be molded into a thin and hollow object, which reduces carbon dioxide, making transportation energy efficient.
- Explains that plastic is a good molding tool because it is weather-resistant compared to things like metal, fabric, wood, and glass.
- Explains that plastic is economical and a good molding tool, and it saves time and is convenient for our everyday use. bottled water is one of the main usages of plastic.
- Explains that plastic allows us to manufacture goods cheaply, but its long-term environmental costs are significant. overuse of plastic is what is making plastic bad for the environment.
- Recommends educating the public to reduce the long-term effects of plastic by recycling crates, detergent and cleaning product bottles, plastic bags, and plastic foam.
1806 wordsRead More - Crude Oil and Hydrocarbonsexplanatory essayScifun. (date unknown) Chemical of the week – polymers, date accessed 18th August 2010, http://scifun.chem.wisc.edu/chemweek/polymers/polymers.html
In this essay, the author
- Explains petroleum, also known as crude oil, is formed from fossilized remains of marine plants and animals that settled on the sea floor millions of years ago.
- Explains how cracking processes break down longer chain hydrocarbons into shorter chains. hydrocracking produces no residues, only light oils, while maximising the yield of petrol components.
- Explains that decane can be cracked to produce octane and ethene.
- Describes a process that converts naphthas into high octane petrol and petrochemical products using heat, pressure, and catalysts.
- Explains that many plastics are made from hydrocarbon monomers, that combine together to make polymer backbones. thermoplastics and thermosets undergo a chemical change when heater
- Explains that bio-fuels are created from plant or animal matter or from metabolic by-products. ethanol reduces fuel mileage as it has a lower heat content compared with petroleum.
- Explains that there has been a steady increase in atmospheric carbon dioxide levels, as well as methane, ozone and cfc’s, which are all green house gases.
- Cites kovarik w. & hermes e. m. (date unknown), chemistry of petroleum cracking.
- Explains that oil drilling occurs at land and at sea, and is transported to an oil refinery. fractional distillation is the process in which the different length hydrocarbon chains are separated by their boiling points, which are dependent on the length.
- Explains that polymers are complex compounds, consisting of monomer chains, created by polymerization.
- Explains combustion is an exothermic reaction that produces heat and sometimes light when a chemical reaction occurs between fuel and an oxidant.
- Cites scifun's chemical of the week – polymers, accessed 18th august 2010, at http://sciffun.chem.wisc.edu/chemweek/polymers.html. american chemistry council (2010), life cycle of a plastic product
1127 wordsRead More - Recycling of Polyethylene Terephthalateexplanatory essayThere are six classifications of plastics, each assigned a number. Numbers 1 and 2 are commonly recycled, 4 is recycled less, and the others are generally not recycled. The first is polyethylene terephthalate (PET).[2] PET is commonly used in making liquid containers such as plastic soda and water bottles and has many other applications.[1] Recycled PET also has many applications, including textiles, sheets for tapes, and the bottle market.[2] The second type of plastic is high-density polyethylene (HDPE). HDPE is used in milk, detergent, and oil bottles and plastic bags. It is crushed into flakes and washed, then dried and shaped into pellets. Some uses for recycled HDPE are trash cans, flower pots, lumber, and other non-food applications.[2] The third type of plastic is vinyl or poly vinyl chloride (PVC). Low-density polyethylene (LDPE) is the fourth type of plastic, and is used in many plastic bags and shrink wraps. It has the same chemical makeup as HDPE but is less dense and more flexible. Recycled LDPE is used for plastic trash bangs and grocery sacks and plastic lumber, as well as several other applications.[2] The fifth type of plastic is polypropylene (PP), which is used in food wrap, some carpets, and bottle tops. P...
In this essay, the author
- Explains that over 245 million tons of municipal solid waste (msw) were produced by consumers in 2005.
- Explains that there are six classifications of plastics, each assigned a number. numbers 1 and 2 are commonly recycled, 4 is recycled less, and the others are generally not recycled.
- Explains that grace and i chose polyethylene terephthalate for water and soft drink bottles, peanut butter jars, and other impact-resistant bottles as well as textiles.
- Explains that the post consumer pet recycling industry was initiated by the fact that it is non-degradable in nature. primary recycling is the most popular, inexpensive method as it deals only with uncontaminated, clean waste pet.
- Explains that mechanical recycling of pet consists of contamination removal and extrusion into the appropriate shape for the desired use after recycling.
- Explains that polyethylene terephthalate is chemically processed by total depolymerization into monomers, oligomers and other products. karayannidis and achilias define hydrolysis as the method of pet waste recycling.
- Explains that the fourth method of recycling polyethylene terephthalate is energy recovery by combustion, carried out in special combustion chambers in waste-to-energy facilities.
- Explains that many plastic bottle factories prefer not to use recycled pet because it is pricier than just using the new resin. recycling and reuse of plastics has several beneficial economic and environmental impacts.
- Explains that most plastic bottles are made from either pet or hdpe, depending on which type of plastic is needed. the recycling rates for plastics bottles remain at 25%.
- Explains that biodegradable plastics have been around for a long time, but the high expense has never made it appealing.
- Explains jenny gitlitz's findings that even though 167 million pounds of pet bottles were recycled last year, 271 millions pounds still went to waste.
- Explains that the recycling industry adds $236 billion a year to the us economy and gives 1.1 million workers jobs.
- Reports that the volume of polyethylene terephthalate plastic bottles recycled in 2005 rose to 1,170 million lbs and the recycling rate increased 1.4 percentage points, from 21.6% to 23.1%.
- Explains that patagonia, global green, e-wear, deja shoe, wickers, reebok, and ford motor company use recycled pet plastic in their products.
- Cites lotfi, ahmad, and karayannidis, george and dimitris s. achilias.
- Cites subramian, p.m., and hoy, valerie. plastic bottle recycling fails to keep up with increasing sales.
- Cites the national recycling coalition's "top 10 reasons to recycle" and "plastics recycling 201."
1599 wordsRead More - Polyethylene: Manufacturing Cycle and Environmental Impactanalytical essayThe most common form of polyethylene is petroleum based or olefins based; as before mentioned polyethylene compounds have a wide commercial applicability and are made from non-renewable resources (Harding, Dennis, von Blottnitz, Harrison, & S.T.L., 2007). Its manufacturing processes are regarded as energy intensive and release significant amount of CO2 and heat into the atmosphere (Broderick, 2008). Next a little more detailed description of polyethylene’s production processes will be presented, with a focus on the way the material inputs are extracted and synthesized.
In this essay, the author
- Explains that stephenson, r., and blackburn, j.j. (1998), the industrial wastewater systems handbook.
- Explains that polyethylene is petroleum based or olefins-based. its manufacturing processes are energy intensive and release co2 and heat into the atmosphere.
- Evaluates the environmental impact of polyethylene by considering input materials, energy and emissions/wastes generated by the production processes.
- Cites abonyi, al, and broderick, r. (2008, spring). process analysis and product quality estimation by self-organizing maps with an application to polyethylene production.
- Explains frosch, gallopoulos, and harding, k, dennis, j, von blottnitz, h, harrison, & s.t.l.
- Cites piringer, o., and baner, a. (2008). plastic packaging: interactions with good and pharmaceuticals.
885 wordsRead More - Kevlar Aramid Fiberexplanatory essayKevlar Aramid Fiber is a synthetic (man-made) material known as a Polymer. A polymer is a chain that is made up of many similar molecular groups, better known as ‘monomers’ that are bonded together. ‘Monomers’ are made up of fourteen Carbon atoms, two Nitrogen atoms, two Oxygen atoms and ten Hydrogen atoms. A single Kevlar polymer chain could possibly have anywhere from one to five million monomers bonded together.
In this essay, the author
- Describes kevlar aramid fiber as a synthetic (man-made) material that is made up of many similar molecular groups, better known as ‘monomers’.
- Explains how the polymer chains are put together improves the properties of the material. the flexibility, strength, and stiffness of kevlar fiber, is dependent on the orientation.
- Explains that the crystallinity of kevlar polymer strands contributes to the unique strength and stiffness of the material.
- Explains that polymer chains are long, individual chains, although they behave as if they are attached to each other. scientists discovered this by using a special type of x-ray microscopy called ‘xanes’.
- Explains that kevlar aramid fiber is an improved material, which is lightweight, man-made organic fiber. it has high strength, low weight, chemical resistance and high cut resistance.
- Explains that kevlar fiber is flame resistant and stable at high temperatures, as well as at normal temperature and storage conditions. it is a better thermal insulating material than most conventional fibers.
- Explains that kevlar has a good balance of key properties, which is suitable for high performance applications.
- Explains that although kevlar has poor abrasion resistance, finish oil protects the material. most organic solvents (oil) have little effect, and most salt solutions (sodium chloride).
736 wordsRead More