Plastic product design criticality

Beyond this initial theoretical drawing-board-and-slide-rule approach, of course, lies the critical need for experimental proof in actual process machinery and prototype field trials, which should be included as a 4th dimension in such a schematic diagram, and is the final pragmatic judgment to determine technical success of any plastic product. This is the direction in which applications research and product design must grow in the future, in order to convert plastics art into plastic science. 

This review shows what the veteran plastic designer knows that plastic products are often stiffiiess critical, whereas metal products are usually strength critical. Consequently, metal products are often made suffer than required by their service conditions, to avoid failure, whereas plastic products are often made stronger than necessary, for adequate stiffiiess. 

The SF usually used based on experience is 1.5 to 2.5, as is commonly used witli metals. Improper use of a SF usually results in a needless waste of material or even product failure. Designers unfamiliar with plastic products can use tlie suggested preliminary safety factor guidelines in Table 7.3 tliat provide for extreme safety intended for preliminary design analysis only. Low range values represent applications where failure is not critical. The higher values apply where failure is... 

Clearly, if you had experience of the product and application none of this discussion would be relevant. However, indirect experience can be applied, i.e., information about the same material in another application and how other materials performed in this application, including information generated by other people. The majority of products, both plastic and metal, are probably designed largely on the basis of experience. It is not an inferior approach, rather one that is critically dependent on the quality of the experience and the validity of the way it is applied to the new circumstance. 

For a two-level factorial design, only two excipients can be selected for each factor. However, for the filler-binder, a combination of brittle and plastic materials is preferred for optimum compaction properties. Therefore, different combinations such as lactose with MCC or mannitol with starch can count as a single factor. Experimental responses can be powder blend flowability, compactibility, blend uniformity, uniformity of dose unit, dissolution, disintegration, and stability under stressed storage conditions. The major advantage of using a DOE to screen prototype formulations is that it allows evaluation of all potential factors simultaneously, systematically, and efficiently. It helps the scientist understand the effect of each formulation factor on each response, as well as potential interaction between factors. It also helps the scientist identify the critical factors based on statistical analysis. DOE results can define a prototype formulation that will meet the predefined requirements for product performance stability and manufacturing. 

To control use of critical chemicals, various types of regulations were used. The basic one (NPA order M-45) was designed to provide for distribution and use of limited supplies of chemicals so as best to serve the interests of national defense and civilian production. Approximately 10 chemicals were controlled by this order. These included naphthenic acid, polyethylene, resorcinol, sebacic acid, methylene chloride, methyl chloride, Thiokol, Teflon, sulfuric acid, and plastic-type nylon. 

Carbon black finds its way into many products inks, paints, paper, fertilizer, plastics, and explosives to name a few. By far the major use, however, is in automotive tires which consume 65% of the total production. The present day tire contains roughly 1 pound of carbon black for each 2 pounds of rubber and provides both the bounce and wear characteristics desired by the user. The properties carbon black imparts to rubber compounds are so critical that there are currently more than 20 classified grades of oil blacks. Most distinctions between grades are mainly a function of particle size and structure, although surface chemistry is sometimes a factor for specialty uses. The more important grade designations are illustrated in Table I. Each of those listed are also subdivided according to their structure levels. 

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