Plastics memory

Plastic memory is a phenomenon of TPs that has been stretched while hot beyond its heat distortion point to return to its original processed or molded form. Different plastics have varying degrees of this characteristic and degree of return is basically dependent on temperature (Chapter 4, Thermoforming, Memory). 

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Corrosion is fundamentally a problem associated with metals. Since plastics are electrically insulating they are not subject to this type of damage. Plastics are basically non-corrosive. However, there are those that can be affected when exposed to corrosive environments. It is material deterioration or destruction of materials and properties brought about through electrochemical, chemical, 

Basically corrosion resistance is the ability of a material to withstand contact with ambient natural factors or those of a particular artificially created atmosphere without degra- 

Temperature Elevated, depressed, cyclic around the norm  

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Thermoplastics can be bent, pulled, or squeezed into various useful shapes. But eventually when heat is added, they return to their original form. This behavior, known as plastic memory, can be annoying. If property applied, however, plastic memory offers interesting design possibilities for all types of fabricated products. 

The time/temperature-dependent change in mechanical properties results from stress relaxation and other viscoelastic phenomena that are typical of these plastics. When the change is an unwanted limitation it is called creep. When the change is skillfully adapted to use in the overall design, it is referred to as plastic memory. 

PROCESS AND APPARATUS FOR PRODUCING MATERIALS HAVING PLASTIC MEMORY Filed July 15,1960... 

In the brain, NO acts both as a neurotransmitter and as a paracrine hormone. Its functions involve regulation of synaptogenesis, synaptic plasticity, memory formation, cerebral blood flow, olfaction, visual transduction, and neuroendocrine secretion (Schmidt and Walter, 1994). In brain ischemia-reperfusion phenomena -NO has been reported to serve a protective role by inducing vasodilation and reducing neutrophil/platelet adhesion and aggregation, thus leading to increased blood flow, tissue perfusion, and attenuation of the ischemic insult. -NO may also protect the patient from ischemic-induced brain injury by -NO-mediated down-modulation of N-methyl-D-aspartate (NMDA) receptors, thus diminishing NMDA-induced neurotoxicity (Lipton et al., 1993 Choi, 1993 Wink et al., 1993). 

Critical requirements for PE are rapid processing, thinner yet stronger films, ease of direct printing or adherence of labels, rapid heat sealing, high strain rate at high strain for stretch wrap, plastic memory for shrink wrap, cross-linkability to resist creep and stress relaxation, cross-linking to resist elevated temperatures when the... 

Protein phosphorylation has been shown to be intimately involved in the assembly and function of the post-synaptic density (Yamauchi 2002), synaptic vesicle turnover (Turner, Burgoyne et al. 1999), LTP (Hedou and Mansuy 2003) and synaptic plasticity/memory (Schulman 1995). It is therefore obvious that study of protein phosphorylation on a proteomic platform will yield a wealth of data relevant to the molecular basis of brain function. 

Mechanical properties PTFE maintains its tensile, compressive, and impact properties over a broad temperature range. Hence, it can be used continuously at temperatures up to 260 °C, while still possessing a certain compressive plasticity at temperatures near absolute zero. PTFE is quite flexible and does not break when subjected to stresses of 0.7 MPa according to ASTM D 790. Flexural modulus is about 350-650 MPa at room temperature, about 2000 MPa at —80 °C, and about 45 MPa at 260 °C. The Shore D hardness, measured as per ASTM D 2240, has values between D50 and D60. PTFE exhibits plastic memory, that is, if subjected to tensile or compression stresses below the yield point, part of the resulting deformations remain after the discontinuance of the stresses. If the piece is reheated, the induced strains tend to release themselves within the piece, which resumes its original form. 

Memory zone (elastic memory, plastic memory) n. The tendency of a plastic article to revert in dimensions to a size previously existing at some stage in its manufacture. For example, a film that has been oriented by hot stretching and chilled while under tension, will, upon reheating, tend to revert to its original pre-stretched size due to its memory . 

Aluminium honeycomb, in contrast to polymeric honeycombs, undergo permanent deformation under load plastics honeycombs recover ( plastic memory ). 

Polyvinyl alcohol (PVA) foams can have plastic memory capabilities similar to those of polyurethanes (Tadavarthy et al., 1975). Currently PVA is mostly used as a foam in... 

When most materials are bent, stretched, or compressed, they somehow alter their molecular structure or grain orientation to accomodate the deformation permanently, but this is not so with polymers. Polymers temporarily assume the deformed shape, but they always maintain the internal stresses that keep wanting to force the material back to its original shape. This desire to change shape is what is usually called plastic memory. 

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