Cost per volume of plastic

The ID profession has embraced plastics with enthusiasm for several reasons. First, plastics provide enormous freedom of shape compared with traditional materials of design. They also permit product production that is faster and more consistent, and they can do it all at a fraction of the cost for making nonplastic products. This low product cost does not stem from the fact that plastics are low in cost. On a per-pound basis, they are actually more costly than many competing materials. But the processability and relatively low density of plastics (which translates into lower costs per volume) gives them a big economic advantage. The net result is that the ID can now achieve quality products at disposable price levels (216). 

Another factor to consider in the early stages of design is material selection in relation to cost per volume rather than by weight. This subject volume vs. weight will be reviewed latter in this chapter entitled Analysis Method. Since the material value in a plastic product is usually over one-half of its overall cost, it becomes important to select a candidate material with extraordinary care. 

Plastics and polymer composites are much more expensive than metals, even more-specialized ones such as nickel. As for the specific mechanical properties, the high densities of metals modify the classification of the various materials. According to the cost per volume, plastics are competitive. Only the very high performance plastics or composites are more expensive than metals. 

Ext. D C. Colorants not certifiable for use in oral products but considered safe for use in externally applied products specifically excludes colorants that may have oral toxicity, extender. A low-gravity material used in paint, ink, plastic, and rubber products to reduce cost per volume by increasing bulk. Some example of extenders are diatomaceous earth, wood floe, mineral rubber, etc. In the food industry, soybean is used as an extender in meat products, providing equivalent nutritional value at a lower cost, extract. A product derived from vegetable matter by the application of solvents, heat or pressure to separate it from the other constituent parts, extraction. The process of treating a natural raw material with an organic solvent. The solvent portion containing the extracted material is filtered and the solvent removed. The extract will contain nonvolatile as well as volatile components. Oleoresins, resinoids, concretes, and absolutes are all produced by extraction. 

According to these data, the moduli of elasticity of plastics lie below those of wood, concrete, and metals thus, these materials are more rigid than plastics. But the yield stress limit of plastics is significantly higher than that of concrete (particulate filled cement), and about the same as that of wood, copper, and aluminum, but it is much lower than that of cast iron, titanium, and steel. Concrete and wood are less expensive materials, whereas plastics and metals cost about the same per unit mass. But, because of their low densities, plastics cost considerably less than metals on a volume basis. Plastics compare relatively poorly with concrete, wood, and metals in terms of the performance per unit cost with respect to the modulus of elasticity. But plastics compete successfully with concrete and metals in respect to the cost per unit of tensile strength. 

When plastics are used for a molded article, a specified volume of material must be used to achieve a certain effect. However, prices for plastics usually are given on a unit weight basis. If acetal resin is to compete on a cost-per-volume basis with polypropylene in a given application, what must the price ratio be on a weight basis (see Appendix C) ... 

Calculating the volume (in.3 or cm3) of the product and multiplying it by cost per the volume unit derives the cost of the plastic material content. Once the volumes of the product are established, one will utilize these data as the basis for obtaining the remainder of the information. 

Plastic materials manufacturing is primarily a large-volume, low-cost, low-unit profit margin business with great overall economies. The plastics generally compete with each other on a money value basis in which an economic analysis takes into account the differing densities of the various plastics in order to judge them on a cost per pound or volume basis. 

The preliminary cost analysis was conducted with the help of Mr. Peter Chan of Chiaphua Industries Ltd. Table 12.8-2 compares the cost of subcontracting the manufacture of plastic and metal appliance components versus manufacturing in-house for a production volume of 1000 units per month. All calculated costs are below the US 100 limit. A cost saving of twenty percent was forecasted assuming that the facility will be built and operated in China where the land and labor costs are cheaper. 

Today there are between 45 and 50 plastic materials. Physical volume, averaging a 13% per year growth rate for the past ten years, reached an estimated 16 billion pounds in 1968, higher than that of any metal except iron and steel, and approaching the total for non-ferrous metals. The number of formulas, grades, and types of these materials is greatly expanded by the use of plasticizers, fillers, and polymerization alternatives. All of these formulations are presumably different from one another and offer the user a broad material selection to fit his property and cost requirements. 

EXTENDER. A low-graxily material used in paint, ink. plastic, and rubber formulations chiefly to reduce cost per unit volume by increasing bulk, Extenders include dialomaccou.s earth, wood flock, mineral rubber, liquid asphalt, etc. Microscopic droplets of water fixed permanently in a plastic matrix are an efficient extender tor polyester resins. In the food industry, the term refers to certain extruded proteins, especially those derived from soybeans, which are used in meat products to provide equivalent nutrient values at lower cost. Made from defatted soy flour, they are often called textured proteins. 

Similar to these hard plastic applications, the use of elastomers has a number of advantages over silicon as biosensor housing material. Besides fabrication cost and brittleness as described above (PDMS is about 50 times less expensive than siUcon on a per volume basis), moving parts are extremely difficult to make in the stiff silicon material without increasing the overall size significantly. Also, valves, which will be discussed in more detail below, need a soft material as valve seat to close completely (thus, elastomers have to be... 

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