Similar to Polyethylene

Formation of polymethylene by this reaction is not practical for commercial utilization. 

Colloidal gold and fine copper powder also catalyze diazoalkane polymerizations. The reaction appears to proceed by formation of alkylidene or carbene species that are bound to the surfaces of metals. The initiations are completed by additions of diazoalkanes to the bound carbenes followed by liberations of nitrogen. Termination may take place by chain transfer, perhaps to a monomer, or to the solvent.  

Many different diazoalkanes lend themselves to these polymerization reactions. Polypentylid-ine, polyhexylidine, polyheptilidine, and polyoctylidine form with a gold complex catalyst, AUCI3-pyridine.  

An entirely different route to preparation of macroparaffins is through a high-pressure reaction between hydrogen and carbon monoxide. Transition metals, like finely divided ruthenium, catalyze this reaction. At pressures of about 200 atmospheres and temperatures below 140 °C, polymethylene of molecular weight as high as 100,000 forms  

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Although similar to polyethylene both in its structure and its properties, polypropylene has developed different patterns of usage. Estimates for the market breakdown in the United States, which are similar to those in Western Europe, are given in Table 11.8. 

Most properties of polypropylene are similar to polyethylene but polypropylene has higher softening point and at 140°C polypropylene still retains its shape. Polypropylene is more susceptible to oxidation by air at higher temperature. Cross-linking, chlorination and other reactions lead to degradation of Polymer chain and are not very useful commercially. 

Pullulan is a linear, water-soluble polysaccharide containing repeating trimers of 1,4-a-D-glucopyranose and 1,6-a-D-glucopyranose in a 2 1 ratio. Its films are touted for their similarity to polyethylene (Glicksman, 1982). 

PP/PA (polypropylene/polyallomer). These plastics are similar to polyethylene, but each unit of their chains has a methyl group attached. They are translucent, autoclavable, and have no known solvents at room temperature. They are slightly more susceptible than polyethylene to strong oxidizing agents. They offer the best stress-cracking resistance of the polyolefins. Products made of polypropylene are brittle at ambient temperature and may crack or break if dropped from benchtop height. 

PVC (polyvinyl chloride). These plastics are similar to polyethylene, but each of their units contain a chlorine atom. The chlorine atom renders PVC vulnerable to some solvents, but also makes it more resistant in many applications. PVC has extremely good resistance to oils (except essential oils) and very low permeability... 

PLA compares well with petrochemical-based plastics used for packaging. It is clear and naturally glossy like polystyrene, it is resistant to moisture and grease, it has flavour and odour barrier characteristics similar to polyethylene terephthalate (PET). The tensile strength and modulus of elasticity of PLA is also comparable to PET. 

Okopack Film S is semi-transparent with properties similar to polyethylene. Okopack C and S can be used for production of flat films, sleeve films and bags and sacks, which can be used for fruit and vegetable packaging. 

Fischer-Tropsch (FT) technology converts synthesis gas produced by reforming of methane or coal gasification into waxy products. Long alkanes (-CH2 -chains) produced by using FT synthesis are chemically similar to polyethylene. Lubricating oils derived from isomerization of FT waxes are gaining interest due to increased demand for lubricants with the advanced performance and environmental benefits described earlier. 

Oral sodium phosphate 90 ml mixed with 300 ml of clear liquid has been compared with 2 liters of polyethylene glycol solution in a colonoscopist-blinded, randomized trial in 100 patients undergoing colonoscopy as a daycare procedure (40). Sodium phosphate was well tolerated and safe and provided bowel cleansing similar to polyethylene glycol. Five patients who received polyethylene glycol and four who received sodium phosphate reported nausea, and eight patients who received polyethylene glycol and one who received sodium phosphate complained of abdominal fullness. 

Significantly different seemed intiaUy the crystal morphology of polyethylene, polybutene-1, polypropylene, polystyrene, poly(4-methyl pen-tene-1), and polyisoprene polymerized with varying solvents and at varying temperatures (114, 123). Discrete hollow particles with a fibrous texture could be observed. The fibrils had an appearance similar to polyethylene crystallized from solution sheared by rapid stirring (118). A closer analysis of this similarity was carried out by Wikjord and Manley (124), Keller and Willmouth (117), and Ingram and Schindler (125) for polyethylene. 

Similar to polyethylene, the presence of a large number of peaks with relatively equal intensity in the pyrogram suggests that the pyrolysis mechanism starts with a random scission. The presence of alkanes, alkenes, and dienes shows that this process is terminated by disproportionation. The peak with relatively higher intensity is the propylene trimer (2,4-dimethyl-1-heptene), probably the most stable compound in the pyrolysis conditions used for this particular experiment. 

Thermograms of the methane and methyl chloride films and a commercial sample of polyethylene are shown in Figure 6. The latter is presented for comparative purposes. The differences between the methane and methyl chloride films can be seen readily from their thermal stabilities. The behavior of the methane film is similar to polyethylene, losing weight rapidly above 300 °C. The methyl chloride film by contrast loses weight slowly above 300°C. and the loss levels off above 550°C. About 81% of the sample is left at 800°C. 

Polybutylene is another new member of the polyolefin group, being similar to polyethylene but exhibiting better tensile strength. It is frequently used blended with polyethylene or polypropylene to modify the properties of films, i.e. to give a controllable peelable seal, and a good future as copolymers is predicted. 

Tensile Properties Similar to polyethylene, the stress-strain curve of JSR RB has a yield point. Above the yield point, the stress-strain curve continues to increase with elongation, then breaks. This kind of stress-strain curve is similar to EVA and indicates a characteristic property lying somewhere between amorphous and crystalline polymers. The dynamic properties of JSR RB can be improved by stretch-... 

Polypropylene is a versatile polymer used in applications from films to fibers, with a worldwide demand of over 21 million Ib. It is similar to polyethylene in structure except for the substitution of one hydrogen group with a methyl group on every other carbon. On the surface, this change would appear trivial, but this one replacement changes the symmetry of the polymer chain. This allows for the preparation of different stereoisomers, namely, syndiotactic, isotactic, and atactic chains. These configurations are shown in the introduction. 

A thermoplastic copolymer made from ethylene and vinyl acetate. This copolymer is similar to polyethylene but has considerably increased flexibility. 

Similar to polyethylenes the morphology of these polymers is also described as a lamellar stack of crystalline and non-crystalline layers. This so-called two phase model is applied for the interpretation of X-ray diffraction data as well as for heat of fusion or density measurements. However, it is well known that several mechanical properties, as well as the relaxation strength at the glass transition temperature, cannot be described by such a simplistic two-phase approach, as discussed by Gupta [59]. Prom standard DSC measurements [60], dielectric spectroscopy, shear spectroscopy [61], NMR [62], and other techniques probing molecular dynamics at the glass transition (a-relaxation) temperature, the measured relaxation strength is always smaller than expected... 

Butyl rubber n (1940). A synthetic elastomer produced by copolymerizing isobutylene with a small amount (ca 2%) of isoprene or butadiene. It has good resistance to hear, oxygen and ozone, and low gas permeability. Thus, it is widely used in inner tubes and to line tubeless tires. Butyl rubber is a vinyl polymer, and is very similar to polyethylene and polypropylene in structure, except that every other carbon is substituted with two methyl groups. It is made from the monomer isobutylene, by cationic vinyl polymerization. It can also go by the name of polyisobutylene. (1) Generic name for vulcanizable elastic copolymers of isobutylene and small amounts of diolefins. (2) Mixture of isobutylene, 98% and... 

Polybutylene terephthalate (PBTP, PBT, and polytetramethylene terephthalate) n. A member of the polyalkylene terephthalate family, similar to polyethylene terephthalate in that it is derived from a polycondensate of terephthalic acid, but with butanediol rather than glycol. PBTP can be modified easily to overcome its relatively low-operating-temperature limit, making it equivalent to plastics used in... 

Polypropylene n. Poly(l-propene) A plastic polymer of propylene (03 45). Similar to polyethylene, but each unit of the chain has a methyl group attached. It is translucent, autoclavable, and has no known solvent at room temperature. A polymer of propylene (propene). Abbreviation PP. also called polypropene. 

Polyvinyl chloride (PVC) (1933) n. Poly (vinyl chloride), poly(l-chloro-ethylene). A vinyl polymer which is similar to polyethylene, but on every other carbon in the backbone chain, one of the hydrogen atoms is replaced with a chlorine atom. It is produced by the free radical polymerization of vinyl chloride. A white, water-insoluble, thermoplastic resin, derived by the polymerization of vinyl chloride. A hard and tough plastic solid. Stabilizers are necessary to prevent discoloration from exposure to light and heat. Used for plastics and coatings. Commonly known as vinyl. Abbreviation is PVC See image). 

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