Commercial polyethylene origin

LDPE, the original commercial polyethylene, is a highly branched polymer... 

Another subclass of substituted amides that is of great commercial value is the ethoxylated amides. They can be synthesized from alkanolamides by chain extending with ethylene or propylene oxide or by ethoxylation directly from the primary amide (46—48). It was originally beheved that the stepwise addition of ethylene oxide (EO) would produce the monoethano1 amide and then the diethanolamide when sufficient ethylene oxide was added (49), but it has been discovered that only one hydrogen of the amide is substituted with ethylene oxide (50—53). As is typical of most ethylene oxide adducts, a wide distribution of polyethylene oxide chain length is seen as more EO is added. A catalyst is necessary to add ethylene oxide or propylene oxide to a primary or an ethoxylated amide or to ethoxylate a diethoxy alkanolamide synthesized from diethanolamine (54). 

An inflammable PE sponge that does not release any toxic gas when in contact with fire has been developed by Sanwa Kako Co.Ltd. The inner side of the polyethylene is chemically coated with a flame retardant using electron beam technology. The material is claimed to be suitable for use in car seats, furniture and cushions. Commercial production of the material is planned for late 1993. This abstract includes all the information contained in the original article. 

The original recipe involved the aqueous impregnation of chromic acid on silica, although nowadays less-poisonous chromium(III) salts are used. Over the years, a family of Phillips-type catalysts has emerged producing no less than 50 different types of polyethylene, and this versatility is the reason for the commercial success of the Phillips ethylene polymerization process. The properties of the desired polymer product can be tailored by varying parameters such as calcination temperature, polymerization temperature and pressure, by adding titania as... 

Plastics are not, as many people believe, new materials. Their origin can be traced to 1847 when Shonbein produced the first thermoplastic resin, celluloid, by reaction of cellulose with nitric acid. However, the general acceptance and commercialization of plastics began during the Second World War when natural polymers, such as natural rubber, were in short supply. Thus, polystyrene was developed in 1937, low density polyethylene in 1941, whereas other commodity plastics such as high density polyethylene and polypropylene were introduced in 1957. 

The original, simplest polyolefins, polyethylene and polypropylene, continue to dominate the scene, even after two decades, to such an extent that no other polyolefin even appears on the production charts. Nevertheless, a great many (we may assume all) available olefins have been tested, and many have been found capable of being converted to stereoregular polymers. As was mentioned above, poly(l-butene) and poly(4-methy1-1-pentene) are being offered commercially and may be expected to achieve significant volume in the future. Isotactic and syndiotactic polystyrene are of much theoretical interest (26) but are not yet commercial products. 

The evolution of dispensers into a yet stronger point-source-emission mode and further away from the original uniform fog mode occurred in the mid-1980s with the commercial appearance of the Shin-Etsu ropes. These were made up of the pheromone of the target species residing in sealed polyethylene tubes that were hand-applied in a twist-tie manner around plant stems. The reduction in the number of point sources per hectare from tens of thousands (fibers) to now only 1,000 or even 500/ha was achieved with fewer, but higher-strength point sources with no loss of efficacy. 

I won t dwell on the implications of all this, but I will mention that Barbara didn t get her chemistry right. The original Barbie dolls were made not of polyethylene but of polyvinyl chloride, or PVC. When this plastic was made commercially available in 1942, it became the basis of a whole slew of vinyl products. The problem with pvc is that it is extremely britde. In order to give it flexibility, manufacturers mix it with substances that can account for as much as 70 percent of the product s total weight. At one point, plasticizers such as dibutyl phthalate were used to separate the long polymer chains of pvc, allowing them to slide over one another, making the plastic pliable. 

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