Load bearing product

LLDPE. See linear low density polyethylene (LLDPE) load-bearing products 139 ... 

These TSEs and TPEs serve engineering s needs in fields dealing with shock absorption, noise and vibration control, sealing, corrosion protection, abrasion and friction resistance, electrical and thermal insulation, waterproofing, and all types of load-bearing products [470-81]. 

Kohlrausch-Williams-Watts Equation n This empirical equation aids designers of load-bearing products made of plastics and reinforced plastics. 

Tbe term structural foam was originally coined by Union Carbide to describe an injection moulded thermoplastic cellular material with a core of relatively low density and a high-density skin. The term has also been used to describe rigid foams that are load bearing. Today it is commonly taken to imply both of the above requirements, i.e. it should be load bearing and with a core of lower density than the skin. In this section the broader load-bearing definition will be used. Whilst structural foams are frequently made from polymers other than polystyrene, this polymer is strongly associated with such products and it is convenient to deal with the topic here. 

It is worth while, now, to analyse the motivation for making metallic single crystals and how, in turn, their production affected physical metallurgy. Initially, metallurgists were concerned to prevent the accidental generation of coarse grains in parts of objects for load-bearing service, and studied recrystallisation with this objective in view. To quote Keith, Iron crystals... were achieved subsequently by... 

The low Mg -t- Si content of H9 facilitates the production of complex extrusions with a good surface finish making H9 a natural choice for glazing sections and other architectural features. Higher mechanical properties are obtainable with the H20 and H30 compositions, which are therefore more suitable for load bearing structures. 

One of the earliest steps in product design is to establish the configuration of the product that will form the basis on which a suitable material is selected to meet performance requirements. During this phase certain design features have to be kept in mind to avoid problems such as reduction of properties. Such features are called detractors or constraints. Most of them are responsible for the unwanted internal stresses that can reduce the available stress level for load bearing purposes. Other features may be classified as precautionary measures that may influence the favorable performance of a product if they are properly incorporated. 

For those not familiar with this type information recognize that the viscoelastic behavior of plastics shows that their deformations are dependent on such factors as the time under load and temperature conditions. Therefore, when structural (load bearing) plastic products are to be designed, it must be remembered that the standard equations that have been historically available for designing steel springs, beams, plates, cylinders, etc. have all been derived under the assumptions that (1) the strains are small, (2) the modulus is constant, (3) the strains are independent of the loading rate or history and are immediately reversible, (4) the material is isotropic, and (5) the material behaves in the same way in tension and compression. 

It should be evident that the full spectrum of the possible materials and applications in load-bearing situations involves many factors that may have to be taken into account. Fortunately, most products involve only a few factors, and others will not be significant or relevant. Regardless, the methods of design analysis must be made available to handle any possible combinations of such factors as the materials characteristics, the product s shape, the loading mode, the loading type, and other service factors and design criteria. 

The product designer should caution the tool designer to keep the gate area away from load-bearing surfaces and to make the gate size such that it will improve the quality of the product. It so happens that the product wall in the gate area develops the minimum tolerance due to the high melt pressure in that area. 

Large, complicated products will usually require more critical structural evaluation to allow better prediction of their load-bearing capabilities under both static and dynamic conditions. Thus, predictions require careful analysis of the structural foam s cross-section. 

The pace of development has increased with the commercialization of more engineering plastics and high performance plastics that were developed for load-bearing applications, functional products, and products with tailored property distributions. Polycarbonate compact discs, for example, are molded into a very simple shape, but upon characterization reveal a distribution of highly complex optical properties requiring extremely tight dimension and tolerance controls (3,223). 

The relatively high concentrations of radon decay products when the fireplaces were open demonstrated that the seal between the floor and the walls had not significantly improved the situation. However, it seemed very unlikely that the new seal was so poor as to permit the rapid changes in concentration that were being observed. The most likely path by which radon from the soil could enter the dwelling therefore appeared to be the walls, particularly the internal load-bearing walls which were in contact with the subsoil. 

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