Stiffness critical products

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

In discussions to this point, no significant interaction between a guest and its medium has been considered. This is probably the case in the reaction cavity model of Cohen [13] as well, since product selectivity was attributed mainly to the presence or absence of free volume within the cavity. The analogy of guests in hosts to balls in boxes is very deficient, but is really not different from the situation in the kinds of crystal systems which first inspired the Cohen nomenclature. Interatomic attraction and repulsion was important in analyzing those systems and was even critical to the crystal engineering used to assemble some of the systems used in the studies by Schmidt and his co-workers [1,48,89]. In addition to being stiff or flexible, cavity walls must... 

For the above-mentioned products, critical fluid technology faces stiff competition from molecular (vacuum) distillation techniques, a time-honored technique, although greater selectivity is potentially available utilizing critical-fluid-based methods. This, coupled with the fact that C02-derived extracts exhibit, in many cases, extended shelf-lives due to the prophylactic action of the residual, nonoxidative CO2 atmosphere, as well as micro-organism de-... 

As the mold cavity is filled with polymer melt, the pressure increase within the cavity can produce stresses of up to 10,000 to 180,000 psi in the mold cavity material. The resulting deformation is substantial but can be accommodated provided the elastic limit of the material is not exceeded. However, where the dimensional tolerance of the molded part is critical, it is imperative that the mold material modulus is sufficiently stiff to ensure part dimensional accuracy. Maintenance of proper temperature of the mold cavity and core is also necessary in this respect as well as for the production of a molded part with good physical and mechanical properties. Dimensional accuracy of the part also demands that the dimensions... 

The type of testing that is required will depend upon the nature of the structure of which the product will form a part and the intended use. For example, ultimate load tests would be inappropriate for an element that will only be lightly loaded. Conversely deflections may be critical and hence the stiffness must be known accurately. 

Acrylic Filament Yarns. Continuous filament acrylic yams face stiff competition from nylon and polyester. Since they are more costly, acrylics have penetrated only those markets where they have a clear advantage in a critical property. In Japan, continuous filament yarns in very fine deniers are valued as a silk replacement. In this market, the yarn is a premium product used in high fashion dress fabrics, satins, and poplins, or to produce a cloth suitable for siuTace raising to give a suede or fine velour effect. 

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