Other Softening Materials

For all the calculations presented in this paper, the input for the material was kept the same. It may be clear that a parameter study with regard to these input parameters is also possible. It is surmised that this macro-structural effect can also play a role in the post-peak behaviour of other softening materials than normalweight or lightweight concrete. Besides for tensile tests, it is supposed that the model can also be used for studying features in bending tests on plain beams. This, however, has not been checked so far. 

Plastic Pipe In contrast to other piping materials, plastic pipe is free from internal and external corrosion, is easily cut and joined, and does not cause galvanic corrosion when coupled to other materials. Allowable stresses and upper temperature limits are low. Normal operation is in the creep range. Fluids for which a plastic is not suited penetrate and soften it rather than dissolve surface layers. Coefficients... 

Stress relief is of little practical value as a means of preventing stress-corrosion cracking in austenitic steels, as cracking occurs at quite low stress levels even in fully softened material and it is difflcult to ensure that stresses are reduced to a safe level in a real structure. The technique can however be useful in small items but, even in this case, phase changes which reduce stress-corrosion resistance or have other deleterious effects can occur at the stress relieving temperature. 

Nomnetallics As stated, corrosion of metals apphes specifically to chemical or electrochemical attack. The deterioration of plastics and other nonmetallic materials, which are susceptible to sweUing crazing, cracking, softening, and so on, is essentially physiochemical rather than electrochemical in nature. Nonmetallic materials can either be rapidly deteriorated when exposed to a particular enviromnent or, at the other extreme, be practicidly unaffected. Under some conditions, a nonmetallic may show evidence of gradual deterioration. However, it is seldom possible to evaluate its chemical resistance by measurements of weight loss alone, as is most generally done for metals. 

Applications Although Soxtec combines the best qualities of reflux and Soxhlet extractions up to now fairly little evidence has been reported concerning the efficacy of this system for polymer and rubber analysis. Nevertheless, it appears that oligomers and other reaction residues, softeners, antioxidants (e.g. BHT) and several other additives used to modify polymers are easily extracted from PVC, PP, PE, PS, rubber and many other polymeric materials. Also, some leading international plastic, rubber and packaging companies have made Soxtec an integral part of their quality control routines. Some application examples where Soxtec has proved successful are [148] ... 

The highly aromatic resins are often used as coumarone/indene resin substitutes. A range of soft aromatic resins is available, produced from the alkylation of xylene and other aromatic hydrocarbons with dicyclopentadiene. These are excellent softeners for a wide range of rubbers. In common with other aromatic materials derived from petroleum sources, some of the resins used within the rubber industry are deemed to be carcinogenic. 

The major difference between injection and extrusion blow molding is the way the soft hollow tube (called a preform or parison) is made. In injection blow molding, two different molds are used. One mold forms the preform and the other mold is used in the actual blow-molding operation to give the final shaped article. In the molding process, the softened material preform, from the preform mold, is introduced into the blowing mold and blow-molded to... 

FIGURE 18.11 Steps employed in simple extrusion blow molding of a test tube. From left to right mold closed softened material introduced air or other gas injected forcing the softened thermoplastic against the walls of the mold and, after suitable cooling, the mold is opened giving the molded plastic test tube. 

PYROMETRIC CONES. Small cones that differ in the temperatures at which they soften on heating. They are made of clay and other ceramic materials and are used in the ceramic industries to show furnace temperatures within ranges. In practice, three or four of the cones which... 

Silicon dioxide is found as sand, flint, quartz, agate, and other common materials. The compound melts at 1710 °C, but it softens at temperatures below that when some of the Si-O-Si bridges are broken. Molten Si02 is a thick liquid that cools to give a glass in which only part of the Si-0 bonds have been disrupted. 

Quaternary ammonium compounds are the next largest group of non-durable antistats. The most widely used are ditallowdimethylammonium chloride and dihydrogenated tallowdimethylammonium chloride (Fig. 10.2). These are common ingredients in laundry and dryer applied consumer softeners. Like many other cationic materials, cationic antistats have an affinity for textile fibres and can be applied by exhaustion processes. 

SIIiIGEN FA imparts a soft handle, so that it is often unnecessary to add any other softening agent. It acts like SlblGEN E in smoothing the surface of the textile material and imparts good hydrophilic properties to the goods at the same time. 

CNC MEL DFC is a viscous, water clear liquid thermosetting resin which is soluble in water at any concentration. The product is fully compatible with other thermosetting resins, organic and inorganic catalysts, synthetic softeners and other thermoplastic materials. 

Shear band formation and evolution, and the change of shear displacement from one location to another, can be analysed numerically. The small and finite displacement on each band, after which the shear displacement is transferred elsewhere, can be explained by a progressive reduction of one or more stress components (and lower mean stress), thus dissipating strain energy. It is not necessary to invoke strain hardening or softening, change of pore pressure or any other intrinsic material weakness in the band. 

The first products were made of 4 to 6% active, a fragrance, and a viscosity modifier [5], The dispersions of cationic actives indeed remain easily pourable as far as their concentration does not exceed 7% by weight since the softening efficacy levels off at concentrations above 6%, this was not a concern. In the mid-1970s improved softening systems made of two actives appeared on the market. They were still based on the same quaternaries, but synergistically combined with other fatty materials called co-softeners to enhance their performance/cost ratio. 

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