Vinyl chloride material factor

It is obvious that the range of possible formulations based on poly(vinyl chloride) and related copolymers is very wide indeed. For each end-use the requirements must be carefully considered and a formulation devised that will give a compound of adequate properties at the lowest cost. In assessing cost it is not only important to consider the cost of the compound but also comparative processing costs, the possible cost of storing additional materials and many other cost factors. 

Poly (vinyl chloride) occurs as a colourless rigid material. It is having a high density and low softenting point. It is also having a higher dielectric constant and power factor. The high chlorine content of poly (vinyl chloride) makes it flame retardant polymers. 

So far, the phenomena discussed pertain to isothermal ageing after a quench (rapid cooling) from above to below Tg. Under such circumstances, ageing always runs in the same direction (increasing retardation times). Peculiar phenomena occur, however, when after a period of ageing at temperature T, the material is heated to a final temperature between T and Tg T < Too < Tg). A good example is poly(vinyl chloride) (PVC) with Tg 80 °C. Struik (1978) compared two samples for which the ageing times at T = 20 °C differ by a factor of 18. When tested at 20 °C, their creep properties differed considerably, but all differences disappeared when the tests were done at 50 °C. 

Note Use of PVC in rigid and semirigid food containers such as bottles, boxes, etc., is under restriction by FDA as well as in coatings for fresh citrus fruits. Its use in thinner items such as films and package coatings is permissible. Possibility of migration of vinyl chloride monomer into food products is the critical factor this tends to increase with the thickness of the material. 

The first macromolecular substances which fotmd technical interest were based on chemically modified natural materials, for example cellulose nitrate (Celluloid) or crosslinked casein (Galalith). Only with the onset of industrialisation in the nineteenth century did these renewable raw materials become the limiting factor for further growth, and chemists began developing artificial macromolecules based on fossil carbon sources like coal, oil, and gas. Polymers like condensation products from phenol and formaldehyde (Bakelite) started the plastics age in 1910 and polymers of styrene or vinyl chloride were used since about 1930 and until nowadays as important plastics. Presently, worldwide more than 260 million tons polymers per year are produced and used as plastics, films, fibres, and synthetic rubber. 

Poly (vinyl chloride) (PVC) is one of the most important thermoplastics produced by the chemical industry [276,277]. For the year 1999, the worldwide total production of PVC was estimated at about 24.3 million tons [278]. Well-known PVC materials, for example, are tubes, valves, flexible pipes, or floor coverings. As can be seen in this short enumeration, it is possible to produce rubberlike up to hard PVC. This variety of applications is attributed to the polar structure of the macromolecule, which permits the use of specific plasticizers [279-281] and specific additives useful for manufacturing [282-285]. Another important factor in PVC technology is grain morphology [286-289]. 

Straight poly(vinyl chloride) is a colourless rigid material. It has a relatively high density and low softening point. (See Table 4.1 for some comparative properties.) Poly(vinyl chloride) has a higher dielectric constant and power factor than polyethylene owing to the polar carbon-chlorine bond. However, at... 

On the other hand, Chickering and Mathiowitz prepared hard microspheres made of both fumaric and sebacic acid and found that these microspheres strongly adhered to the mucosa of a rat intestine. Because such material cannot interpenetrate, it is hypothesized that hydrogen bonding is the cause of mucoadhesion [3]. Mortazavi and Smart measured the adhesive force of disks made of various mucoadhesive materials using a DiaStron rheometer. They concluded that the interaction between the adhesive and mucous is not an important factor because the disk adhered more strongly to poly(vinyl chloride) (used as a reference) than to the rat intestinal mucosa [4]. 

In any application, cost is an important factor. The price of the polymer in the form of a powder, latex, solution, or bale is just part of the economic picture. The cost of other ingredients, equipment for fabrication, labor, power, and all the indirect costs, may well overshadow the polymer s share. A first-line tire containing the best rubber sells for 10-20 times the cost of the raw rubber it contains. Even in a much less complicated structure, such as plasticized poly(vinyl chloride) laboratory tubing, the raw material cost may be less than one-tenth of the selling price. Some properties that might be considered for a single application are as follows ... 

Or you might be more concerned about which uses the cheaper, or more readily available, starting materials—this was probably also a factor in the choice of methylmagnesium chloride and the unsaturated aldehyde in the second example. Both can be bought commercially, while the alternative route to this secondary alcohol would require a vinyllithium or vinylmagnesium bromide reagent that would have to be made from a vinyl halide, which is itself not commercially available, along with difficult-to-dry acetaldehyde. 

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