Plastics mass production

Of these materials zein, the maize protein, has been used for plastics on a small scale. It can be cross-linked by formaldehyde but curing times are very long. Complicated bleaching processes have led to the production of almost colourless samples in the laboratory but the process cannot readily be extended to large-scale operation. The cured product has a greater water resistance than casein. Proteins from soya bean, castor bean and blood have also been converted into plastic masses but each have the attendant dark colour. 

The ebonite compound before cure is a rather soft plastic mass which may be extruded, calendered and moulded on the simple equipment of the type that has been in use in the rubber industry for the last century. In the case of extruded and calendered products vulcanisation is carried out in an air or steam pan. There has been a progressive reduction in the cure times for ebonite mixes over the years from 4-5 hours down to 7-8 minutes. This has been brought about by considerable dilution of the reactive rubber and sulphur by inert fillers, by use of accelerators and an increase in cure temperatures up to 170-180°C. The valuable effect of ebonite dust in reducing the exotherm is shown graphically in Figure 30.3. 

From a practical review, perhaps it can be stated that buildings and construction materials are exposed to the most severe environments on earth, particularity when the long time factor is included. The environments include such conditions as temperature, ultraviolet, wind, snow, corrosion, hail, wear and tear, etc. Basically the following inherent potentials continue to be realized in different plastics ease of maintenance, light weight, flexibility of component design, combine with other materials, corrosion/abrasion/weather resistance, variety of colors and decorative appearance, multiplicity of form, ease of fabrication by mass production techniques, and total cost advantages (combinations of base materials, manufacture and installation). 

Wegeng et al. refer to the low-cost, mass production of microstructures from metals, ceramics, and plastics as a crucial element for widespread application [Ij. Micro technologies, they say, are generally conducive for mass production however, this has so far only been proven for the field of microelectronics. 

A great potential for new compounds is provided by structures with two carbon and two silicon atoms around the central silicon. These polysilanes with organic groups lead to silicon-carbide ceramics. A wide field of application would be opened up if one could make a polysilane as a plastic mass which could be extruded and modeled and if after pyrolysis silicon-carbide is formed without a strong contraction (this means a high ceramic yield). Polysilane fibers are only one product in a range of many... 

Economical plastics are the economical answer for mass production as well as for specific packaging. 

Plastic manifolds are not only used on mass production cars but also on sports cars such as Porsche models, the Chevrolet Camaro and so on. For the intake manifolds used on the Camaro and Firebird, PPA is replacing PA because of several advantages ... 

Costs of environment-friendly plastics in a mass-production scenario are forecast between 1 per kg up to 4 per kg and more. 

Other contaminants that can originate from plastic containers are the additives necessary to turn the raw polymer into adequate containers. While PE may be used without any additive, the other plastics are virtually useless alone but are converted into highly serviceable products by combining them with other substances or materials. The additives most commonly found in plastics used for pharmaceutical products are antioxidants, heat stabilizers, lubricants, plasticizers, fillers, and colorants. These additives can be in liquid, solid, or fine particle forms and are used in amounts varying from less than 1% to more than 50% of the plastic mass. The additives necessary for each of the selected types of polymers are described in Table 23. 

Arsenic Pentasulphide, As2S5.—When arsenic is fused with an excess of sulphur the product contains arsenic, sulphur and arsenic pentasulphide the last-named may be extracted with liquid ammonia 8 or, by careful fractionation, the arsenic and sulphur may be removed, leaving the sulphide. If the elements are fused together in stoichiometric proportions, a greenish-yellow plastic mass is obtained which gradually hardens and becomes lemon-yellow if this product is powdered and digested with aqueous ammonia, a yellow solution results and insoluble sulphur remains. After filtering, the addition of an acid to the yellow solution precipitates the pentasulphide. 

In the processing of plastic masses the destruction is traditionally considered as a negative factor deteriorating physical and mechanical properties of products and manufacturers try to avoid it in every possible way. Mechanical destruction of molten polymers takes place, primarily, under the action of shear strains effectuating the tension of macromolecules 65-661 in this case, molecules with a high molecular mass... 

The plastic chips are more effective and attractive due to their inexpensiveness with rapid mass productivities. SU-8 has versatile applications in the... 

Due to these properties, oligoorganosiloxane oils are especially usable for lubricating mechanisms which operate in veiy low or high (sometimes sharply changing) temperatures, e.g. for ball bearings, automatic distribution valves and stuffing boxes, for lubricating pressure molds in the production of plastic masses, rubber technical articles, metalware, etc. 

The use of silicone emulsions for detaching rubber articles from pressure molds greatly increases the productivity of pressing, reduces spoilage (by 90%) and costs of cleaning the pressure molds (by 80%). If plastic masses are pressed, the introduction of 1-2% of silicone liquid into the composition helps to detach the article from the mold easily, improves its surface and, besides, keeps the pressure mold in use without cleaning for 4 months. When gypsum molds for ceramic articles are manufactured, lubri-... 

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