Polyethylene or polythene (abbreviated PE ; name of IUPAC polyethene or poly (ethylene) ) is the most common plastic. Annual global production is about 80 million tons. Its main use is in packaging (plastic bags, plastic films, geomembrane, containers including bottles, etc.). Many types of polyethylene are known, with most having a chemical formula (C 2 H 4 ) n . PE is usually a mixture of ethylene polymers that are similar to various values ​​of n .
Video Polyethylene
History
Polyethylene was first synthesized by the German chemist Hans von Pechmann, who prepared it by accident in 1898 while investigating diazomethane. When his colleagues Eugen Bamberger and Friedrich Tschirner characterized the white substance, the candle he had created, they knew it contained a long chain of 2 - and called it polymethylene.
The first practical industrial polythylene synthesis (diazomethane is a notoriously unstable substance generally avoided in industrial applications) was discovered in 1933 by Eric Fawcett and Reginald Gibson, again inadvertently, at Imperial Chemical Industries (ICI) working in Northwich, England. After applying very high pressure (several hundred atmospheres) to a mixture of ethylene and benzaldehyde they again produce a white, waxy material. Because the reaction has been initiated by traces of oxygen contamination in their equipment, the experiment was, initially, difficult to reproduce. New in 1935 another ICI chemist, Michael Perrin, developed this accident into a reproducible high-pressure synthesis for polyethylene which became the basis for industrial LDPE production beginning in 1939. Since polyethylene was found to have very low loss properties on radio waves high-frequency commercial distribution in the UK was suspended at the outbreak of World War II, confidentiality was imposed, and new processes were used to generate insulation for UHF and SHF coaxial cables from radar sets. During World War II, further research was conducted on the ICI process and in 1944 Bakelite Corporation in Sabine, Texas, and Du Pont in Charleston, West Virginia, started large-scale commercial production under license from ICI.
The breakthrough marker in the commercial production of polyethylene begins with the development of a catalyst that promotes polymerization at light temperature and pressure. The first is a chromium trioxide based catalyst that was discovered in 1951 by Robert Banks and J. Paul Hogan at Phillips Petroleum. In 1953, German chemist Karl Ziegler developed a catalytic system based on titanium halide and organoaluminium compounds that worked on conditions lighter than Phillips catalysts. Phillips catalysts are cheaper and easier to use, and both methods are widely used in industry. In the late 1950s both Phillips and Ziegler catalysts were used for HDPE production. In the 1970s, the Ziegler system was enhanced by the incorporation of magnesium chloride. The catalytic system based on dissolved catalyst, metallocenes, was reported in 1976 by Walter Kaminsky and HansjÃÆ'¶rg Sinn. Ziegler-based and metallocene-based catalysts have proven to be highly flexible in copolymerizing ethylene with other olefins and have become the basis for a variety of currently available polyethylene resins, including very low density polyethylene and linear low-density polyethylene. Such resins, in the form of UHMWPE fibers, have (in 2005) begun to replace aramid in many high-strength applications.
Maps Polyethylene
Properties
The properties of polyethylene can be divided into mechanical, chemical, electrical, optical, and thermal properties.
Mechanical properties
Polyethylene has low strength, hardness and stiffness, but has a high ductility and impact strength and low friction. It shows a strong creep under continuous strength, which can be reduced by the addition of short fibers. It was a candle when touched.
Thermal property
The usefulness of polyethylene is limited by its melting point of 80 Â ° C (176 Â ° F) (HDPE, the previous type of low softening crystals). For general commercial grades of medium and high-density polyethylene melting points are usually in the range of 120 to 180 ° C (248 to 356 ° F). The melting point for the average, commercial, low-density polyethylene is usually 105 to 115 ° C (221 to 239 ° F). This temperature varies greatly with the type of polyethylene.
Chemical Properties
Polyethylene consists of hydrocarbons with a weight of nonpolar, saturated, and high molecular weight. Therefore, its chemical behavior is similar to paraffin. Individual macromolecules are not covalently linked. Because of their symmetrical molecular structure, they tend to crystallize; polyethylene as a whole partially crystalline. Higher crystallinity increases mechanical and chemical density and stability.
Most LDPE, MDPE, and HDPE have excellent chemical resistance, meaning they are not attacked by strong acids or strong bases, and are resistant to soft oxidants and reducing agents. The crystal sample does not dissolve at room temperature. Polyethylene (other than crosslinked polyethylene) can usually be dissolved at high temperatures in aromatic hydrocarbons such as toluene or xylene, or in chlorinated solvents such as trichlorethane or trichlorobenzene.
Polyethylene hardly absorbs water. The permeability of water vapor and water (only polar gases) is lower than most plastics; oxygen, carbon dioxide and flavors on the other side can pass through easily.
PE can become brittle when exposed to sunlight, black carbon is usually used as a UV stabilizer.
Polyethylene burns slowly with a blue flame that has a yellow tip and gives off a paraffin odor (similar to a candle flame). The material continues to burn at the removal of the source of the flame and produces the infusion.
Polyethylene can not be printed or pasted without pretreatment.
Electrical properties
Polyethylene is a good electrical insulator. It offers good tracking resistance; However, it becomes easily electrostatic charged (which can be reduced by the addition of graphite, carbon black or antistatic agents).
Optical properties
Depending on the heat history and thickness of the PE film may vary between almost transparent, such as milk (translucent) or opaque. LDPE thus has the largest, less LLDPE and the least transparent HDPE. Transparency is reduced by the crystal if it is larger than the visible light wavelength.
Manufacturing process
Monomer
The material or monomer is ethylene (IUPAC name ethene), gaseous hydrocarbon of formula C 2 H 4 , which can be seen as a pair of methylene groups (- CH 2 -) connect to each other. Because this compound is highly reactive, ethylene must have high purity. Typical specifications are & lt; 5 ppm for water, oxygen, and other alkenes. Acceptable contaminants include N 2 , ethane (common precursors for ethylene), and methane. Ethylene is usually produced from petrochemical sources, but is also produced by dehydration of ethanol.
Polymerization
Ethylene is a rather stable molecule that only polymerizes after contact with the catalyst. The conversion is very exotermic. Coordination polymerization is the most pervasive technology, which means that metal chloride or metal oxide is used. The most common catalyst consists of titanium (III) chloride, called the Ziegler-Natta catalyst. Another common catalyst is Phillips catalyst, which is prepared by depositing chromium (VI) oxide on silica. Polyethylene can be produced by radical polymerization, but this route has only limited utility and usually requires high pressure tools.
Join
The common methods used to combine polyethylene parts together include:
- Hot gas wastes
- Tighten
- Infrared wire
- Laser lasers
- Ultrasonic welding
- Heat sealing
- Hot mix
Adhesives and solvents are rarely used because polyethylene is nonpolar and has a high resistance to solvents. The pressure-sensitive adhesive (PSA) is feasible if the surface of the fire is treated or the corona is treated. Commonly used adhesives include:
- Solvent type PSA dispersion
- Polyurethane contact adhesive
- Two parts polyurethane or epoxy adhesive
- Vinyl acetate copolymer melts the hot adhesive
Classification
Polyethylene is classified by its density and branching. Its mechanical properties rely heavily on variables such as breadth and type of branching, crystal structure, and molecular weight. There are several types of polyethylene:
- Ultra-high-strength polyethylene (UHMWPE)
- Ultra-low molecular weight polyethylene (ULMWPE or PE-WAX)
- High molecular weight polyethylene (HMWPE)
- High-density polyethylene (HDPE)
- High-density cross-linked polyethylene (HDXLPE)
- Crosslinked polyethylene (PEX or XLPE)
- Medium density medium (MDPE)
- Polyethylene low-density linear (LLDPE)
- Low density polyethylene (LDPE)
- Very low density polyethylene (VLDPE)
- Chlorinated polyethylene (CPE)
With regard to volume being sold, the most important values ​​of polyethylene are HDPE, LLDPE, and LDPE.
Polyethylene ultra-high-molecular dimension ( UHMWPE)
UHMWPE is a polyethylene with molecular weight numbering in the millions, usually between 3.5 and 7.5 million amu. The high molecular weight makes it a very hard material, but produces less efficient chain packing into the crystal structure as evidenced by less density of high density polyethylene (eg, 0.930-0.935 g/cm 3 ). UHMWPE can be made through any catalyst technology, although the Ziegler catalyst is most common. Due to its exceptional toughness and excellent cutting, wear and chemical resistance, UHMWPE is used in a wide variety of applications. These include can-and-bottle-handling machine parts, moving parts in weaving machines, bearings, gears, artificial joints, edge protectors on ice flickers, and cutting butcher boards. This is usually used for the construction of articular parts of implants used for hip and knee replacements. As a fiber, he competes with aramid in bulletproof vests.
High-density polyethylene (HDPE) Crosslinked polyethylene (PEX or XLPE)
PEX is a medium to high-intensity polyethylene containing crosslinking inserted into the polymer structure, converting thermoplastics into thermosets. The high temperature properties of the polymer are improved, the flow is reduced, and the chemical resistance is improved. PEX is used in some drinking water pipe systems because the tubes made from the material can be expanded to fit the metal nipple and slowly return to their original shape, forming a permanent and waterproof joint.
Medium-density polyethylene (MDPE)
MDPE is defined by the density range 0.926-0.940 g/cm 3 . MDPE can be produced by chromium/silica catalysts, Ziegler-Natta catalysts, or metallocene catalysts. MDPE has good shock and drop resistance properties. It's also less sensitive-notch than HDPE; Stress-cracking resistance is better than HDPE. MDPE is commonly used in gas pipelines and fittings, sacks, shrink films, packing films, carrier bags, and screw covers. Linear low-density polyethylene (LLDPE)
LLDPE is defined by the density range 0.915-0.925 g/cm 3 . LLDPE is a highly linear polymer with a significant number of short branches, generally made by ethylene copolymers with short chain alpha-olefins (eg, 1-butene, 1-hexene, and 1-octane). LLDPE has a higher tensile strength than LDPE, and this implies a higher impact and puncture resistance than LDPE. Lower film thickness (gage) can be blown, compared to LDPE, with better environmental stress-crack resistance, but not easy to process. LLDPE is used in packaging, especially film for bags and sheets. Lower thickness can be used compared to LDPE. It is used for cover cables, toys, lids, buckets, containers, and pipes. While other applications are available, LLDPE is used primarily in film applications due to their toughness, flexibility, and relative transparency. Examples of products range from agricultural films, Suggest wrappings, and bubble wrap, to multilayer and composite films. In 2013, the world's LLDPE market reached US $ 40 billion. Low density (LDPE)
LDPE is defined by the density range 0.910-0.940 g/cm 3 . LDPE has a high short and long chain branching level, which means that the chain does not pack into the crystal structure as well. Hence, the less robust intermolecular forces as the momentary dipole-dipole appeal is less. This results in lower tensile strength and increased ductility. LDPE is made with free radical polymerization. A high branching rate with long chains provides unique and desirable LDPE properties. LDPE is used both for rigid containers and plastic film applications such as plastic bags and film wrappers. In 2013, the global LDPE market has a volume of nearly US $ 33 billion.
The radical polymerization process used to make LDPE does not include catalysts that "oversee" the radical sites on the growing PE chain. (In HDPE synthesis, the radical site is at the end of the PE chain, because the catalyst stabilizes its formation at the end.) The secondary radical (in the middle of the chain) is more stable than the primary radical (at the end of the chain), and the tertiary radicals (at the branch point) are more stable. Each time an ethylene monomer is added, it creates a primary radical, but often it will be rearranged to form a more stable secondary or tertiary radical. The addition of ethylene monomers to secondary or tertiary sites creates branching.
Polyethylene (VLDPE)
VLDPE is defined by the density range 0.880-0.915 g/cm 3 . VLDPE is a highly linear polymer with a high degree of short chain branch, generally made by ethylene copolymerization with short chain alpha-olefins (eg, 1-butene, 1-hexene and 1-octene). VLDPE is most often produced using metallocene catalysts because of the greater co-monomer incorporation exhibited by this catalyst. VLDPE is used for hoses and tubes, ice and frozen food bags, food packaging and stretch wrapping and impact modifiers when mixed with other polymers.
Recently, many research activities have focused on the nature and distribution of long chain branches in polyethylene. In HDPE, a relatively small amount of these branches, perhaps one in 100 or 1,000 branches per carbon backbone, can significantly affect the polymer rheological properties.
Copolymers
In addition to copolymerization with alpha-olefins, ethylene can also be copolymerized with various monomers and other ionic compositions that create ionized free radicals. Common examples include vinyl acetate (the resulting product is an ethylene-vinyl acetate copolymer, or EVA, widely used in athletic shoe soles) and various acrylates. Acrylic copolymer applications include packaging and sporting goods, and superplasticizers, used for cement production.
Molecular structure of different types of PE
The diverse material behavior of different types of polyethylene can be explained by its molecular structure. Molecular weight and crystallinity have the greatest impact, crystallinity in turn depends on the molecular weight and the degree of branching. The less branched chain polymers, and the smaller the molecular weight, the higher the crystallinity of polyethylene. Crystallinity is between 35% (PE-LD/PE-LLD) and 80% (PE-HD). In crystallites, polyethylene has a density of 1.0 g  ± cm -3 , in the amorphous region of 0.86 gÃ,  · cm -3 . Thus, a nearly linear relationship exists between density and crystallinity.
The branching rates of different types of polyethylene can be described schematically as follows:
This figure shows the polyethylene backbone, short chain branch and side chain branch. The polymer chain is represented linearly.
Chain branch
The properties of polyethylene greatly depend on the type and number of chain branches. The chain branches in turn depend on the process used: either high pressure process (PE-LD only) or low pressure process (all other PE values). Low density polyethylene is produced by high pressure processes by radical polymerization, so that many short chain branches and long chain branches are formed. Short chain branches are formed by intramolecular chain transfer reactions, they are always butyl or ethyl chain branches because the reaction takes place after the following mechanism:
Environmental issues
Polyethylene is produced from ethylene. Although ethylene can be produced from renewable resources, it is mainly obtained from petroleum or natural gas.
In addition, widespread use of polyethylene makes it difficult to manage waste if it is not recycled. Polyethylene is not readily biodegradable, and thus accumulates in landfills. Incineration can cause harmful gas emissions.
In Japan, getting rid of plastics in an environmentally friendly way is a major issue discussed until the Fukushima disaster in 2011 becomes a bigger problem. It's listed as a $ 90 billion market for solutions. Since 2008, Japan has rapidly increased the recycling of plastics, but still has a large amount of disposable plastic wrapping.
In 2010, a Japanese researcher, Akinori Ito, released a prototype machine that creates oil from polyethylene using a small independent steam distillation process.
Biodegradability
Polyethylene is not readily biodegradable, and thus accumulates in landfills. However, there are a number of species of bacteria and animals that are able to degrade polyethylene.
In May 2008, Daniel Burd, a 16-year-old Canadian, won the Canadian Science Fair in Ottawa after discovering that Pseudomonas fluorescens, with the help of Sphingomonas, could lower more than 40% of the weight of the plastic bag in less than three months.
Thermophilic bacteria Brevibacillus borstelensis (strain 707) was isolated from soil samples and was found using low density polyethylene as a single carbon source when incubated together at 50 ° C. Biodegradation increased with time exposed to ultraviolet radiation.
Acinetobacter sp. 351 can degrade low-molecular weight PE oligomers. When the PE is subjected to thermo and photo-oxidation, the product includes alkanes, alkenes, ketones, aldehydes, alcohols, carboxylic acids, keto acids, dicarboxylic acids, lactones, and esters are released.
In 2014, a Chinese researcher found that Indian mealmoth larvae can metabolize polyethylene from observing that the plastic bag in his house has a small hole in it. By concluding that the hungry larva must have digested the plastic somehow, he and his team analyzed their intestinal bacteria and found some who could use plastic as their only carbon source. Not only do bacteria of intestinal Plodia interpunctella moth larvae metabolize polyethylene, they are significantly degraded, dropping its tensile strength by 50%, its mass by 10% and the molecular weight of its polymeric chain. by 13%.
In 2017, researchers reported that caterpillar Galleria mellonella consumed plastic waste such as polyethylene.
Chemically modified polyethylene
The polyethylene may be modified in polymerization by polar or non-polar comonomers or after polymerization by reaction of the polymer-analog. The general reaction of the polymer-analog is in the case of crosslinking of polyethylene, chlorination and sulfochlorination.
Non-polar ethylene copolymer
? - olefins
In the low pressure process? -olefins (eg 1-butene or 1-hexene) may be added, incorporated in the polymer chain during polymerization. These copolymers introduce short side chains, resulting in reduced crystallinity and density. As described above, the mechanical and thermal properties are changed accordingly. In particular, PE-LLD is produced in this way.
Metallocene polyethylene (PE-MC)
Metallocene polyethylene (PE-M) is prepared using a metallocene catalyst, usually including a copolymer (Z. B. ethene/hexene). Metallocene polyethylene has a relatively narrow molecular weight distribution, excellent toughness, excellent optical properties and uniform comonomer content. Because of the narrow molecular weight distribution it behaves less pseudoplastic (especially below the larger shear rate). Polyethylene metallocene has low proportion of low molecular weight component (extraction) and low welding and sealing temperatures. Thus, it is suitable for the food industry.
Polyethylene with multimodal molecular weight distribution
Polyethylene with multimodal molecular weight distribution consists of several polymer fractions, which are homogeneously mixed. This type of polyethylene offers very high stiffness, toughness, strength, stress crack resistance and increased crack propagation resistance. They consist of the same proportions of higher and lower molecularly polymeric fractions. The lower molecular weight unit crystallizes easier and relaxes faster. Higher molecular weight fractions form molecules that connect between crystals, thereby increasing the toughness and resistance of stress cracking. Polyethylene with a multimodal molecular weight distribution can be prepared either in a two-stage reactor, by a catalyst with two different active centers on the carrier or by mixing in the extruder.
Cyclic olefin copolymers (COC)
The cyclic olefin copolymers are prepared by the ethene and cycloolefin copolymerization (usually norbornene) produced by the metallocene catalyst. The resulting polymer is an amorphous and highly transparent and heat-resistant polymer.
Polar ethylene copolymers
The basic compounds used as polar comonomers are vinyl alcohols (Ethenol, unsaturated alcohols), acrylic acids (propenoic acid, unsaturated acids) and esters containing one of the two compounds.
Ethylene copolymer with unsaturated alcohol
Ethylene/vinyl alcohol copolymer (EVOH) is (formally) a copolymer of PE and vinyl alcohol (etenol), made with (partial) hydrolysis of ethylene-vinyl acetate copolymer (as the vinyl alcohol itself is unstable). However, EVOH usually has a higher comonomer content than the commonly used VAC.
EVOH use in multilayer films for packaging as a barrier layer (plastic barrier). Because EVOH is hygroscopic (attracts water), it absorbs water from the environment, in which he lost the barrier effect. Therefore, it should be used as a core surrounded by a layer of plastic (such as LDPE, PP, PA, or PET). EVOH is also used as a coating against corrosion on street lights, traffic light poles and noise protection walls.
acid copolymers of ethylene/acrylic acid (EAA)
Ethylene copolymers and unsaturated carboxylic acids (such as acrylic acid) are characterized by good adhesion to different materials, by resistance to cracking stress and high flexibility. However, they are more sensitive to heat and oxidation than ethylene homopolymers. Ethylene/acrylic acid copolymer is used as an adhesion promoter.
If a salt of an unsaturated carboxylic acid exists in the polymer, there is formed a network of thermo-reversible ions, they are called ionomers. Ionomer is a highly transparent thermoplastic characterized by high adhesion to metal, high abrasion resistance and high water absorption.
Ethylene copolymer with unsaturated esters
If the unsaturated ester is copolymerized with ethylene, one part of the alcohol may be present in the backbone of the polymer (as in ethylene-vinyl acetate copolymer) or of the acid group (eg, ethylene-ethyl acrylate copolymer). Ethylene-vinyl acetate copolymer is made equal to LD-PE with high pressure polymerization. The proportion of comonomers has a decisive influence on polymer behavior.
Density decreased to 10% comonomer share due to the formation of disturbed crystals. With a higher proportion it is close to one polyvinyl acetate (1.17 g/cm 3 ). Because crystallinity decreases, the ethylene vinyl acetate copolymer is increasingly softened by increasing comonomer content. The polar side groups change the chemical properties significantly (compared with polyethylene): weather resistance, adhesiveness and welding ability increase with comonomer content, while chemical resistance decreases. Also mechanical properties change: stress fracture resistance and toughness in cold rise, while yield stress and heat resistance decreases. With a very high proportion of comonomer (about 50%) thermoplastic rubber is produced (thermoplastic elastomer).
Ethylene-ethyl acrylate copolymers behave similarly to ethylene-vinyl acetate copolymers.
Crosslinking
A basic difference is made between peroxide crosslinking (PE-Xa), silane crosslinking (PE-Xb), crosslinked electron beam (PE-Xc) and cross-crosszone (PE-Xd).
What is shown is peroxide, silane and irradiation crossing. In each method, radicals are produced in the polyethylene chain (top center), either by radiation (h Ã, Â ·?) Or by peroxide (R-O-O-R). Then, two radical chains can be directly opposite (lower left) or indirectly by the silane compound (lower right).
- Peroxide crosslinking (PE-Xa) : Crosslinking of polyethylene using peroxides (eg dicumyl or di-tert-butyl peroxide) is still very important. In the so-called Engel Process, a mixture of HDPE and 2% peroxide are initially mixed at low temperatures in the extruder and then cross at high temperatures (between 200 and 250 ° C). Peroxides break down into peroxide radicals (ROOs), which abstract (eliminate) hydrogen atoms from polymer chains, leading to radicals. When this merges, a cross linked network is formed. The resulting polymer network is uniform, with low voltage and high flexibility, where it is softer and harder than (irradiated) PE-Xc.
- cross-cross (PE-Xb) : In the presence of silanes (eg polyethylenail silsil), polyethylene can initially be functioned by irradiation or with little peroxide. Then the Si-OH group can be formed in a water bath by hydrolysis, which condenses and binds a PE cross with the formation of Si-O-Si bridge. [16] Catalysts such as dibutyltin dilaurate can speed up the reaction.
- Cross-linked irradiation (PE-Xc) : Polyethylene cross linking is also possible by a downstream source of radiation (usually an electron accelerator, sometimes an isotope radiator). The PE product is crosslinked below the melting point of the crystal by separating the hydrogen atoms. ? -Radiation has a penetration depth of 10 mm, -Radiation of 100 mm. Thus, certain interiors or areas may be exempted from such cross-links. However, due to high capital and operating costs, cross-radiation only plays a small role compared to peroxide crosslinks. Unlike peroxide crosslinking, this process is done in a solid state. Thus, the crosslinking occurs mainly in amorphous regions, whereas crystallinity remains largely intact.
- Cross-ethos (PE-Xd) : In the so-called process of lubonyl polyethylene is a previously azo-linked compound after extrusion in a hot salt bath.
Chlorination and sulfochlorination
Chlorinated polyethylene (PE-C) is a cheap material having a chlorine content of 34-44%. It is used in the mixture with PVC because the soft and elastic chloropolyethylene is embedded in the PVC matrix, thus increasing the impact resistance. In addition, it also improves weather resistance. In addition, it is used to soften PVC foil, without the risk of migrating from the plasticizer. Chlorinated polyethylene can be crosslinked peroxide to form elastomers used in the cable and rubber industry. When chlorinated polyethylene is added to other polyolefins, it reduces flammability.
Chlorosulfonated PE (CSM) is used as a starting material for ozone-resistant synthetic rubber.
Polyethylene based bio
Braskem and Toyota Tsusho Corporation started joint marketing activities to produce polyethylene from sugarcane. Braskem will build a new facility in the existing industrial unit in Triunfo, Rio Grande do Sul, Brazil with an annual production capacity of 200,000 short tons (180,000,000 kg), and will produce high density polyethylene and low-density from sugar-cane bioethanol.
Polyethylene can also be made from other raw materials, including wheat and buckwheat. This development uses renewable resources rather than fossil fuels, although current plastic source problems can be ignored in the wake of plastic waste and especially polyethylene waste as shown above.
Nomenclature and general description of process
The name polyethylene is derived from a material and not a chemical compound produced, which does not contain double bonds. The scientific name polyethene is systematically derived from the scientific name of the monomer. The alkenes monomers change into long, sometimes very long, alkanes in the polymerization process. In certain circumstances, it is useful to use structure-based nomenclature; in such cases IUPAC recommends poly (methylene) (poly (methanadiyl) is an unlikely alternative). The difference in name between the two systems is due to opening the monomer double bonds in the polymerization. This name is abbreviated to PE . In the same way polypropylene and polystyrene are shortened to PP and PS, respectively. In the UK, polymers are generally called polythene, from ICI trade names, although this is not scientifically recognized.
References
Bibliography
- Piringer, Otto G.; Baner, Albert Lawrence (2008). Plastic Packaging: Interaction with Food and Pharmaceuticals (issue 2). Wiley-VCH. ISBN: 978-3-527-31455-3 . Retrieved 2014-02-20 .
- Plastics Design Library (1997). Handbook of Plastics Joined: A Practical Guide (illustration ed.). William Andrew. ISBN: 978-1-884207-17-4 . Retrieved 2014-02-20 .
External links
- Polythene Story: Birth of an accidental plastic bag
- Technical Properties of Polythene & amp; Application
- An article explaining the discovery of Sphingomonas as Kawawada's plastic bag biodegrader, Karen,
(May 22, 2008).
Source of the article : Wikipedia
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