Plasticization explanation

Steps 3 and 4, however, can be described as chemical plasticization since the rate at which these processes occur depends on the chemical properties of molecular polarity, molecular volume, and molecular weight. An overall mechanism of plasticizer action must give adequate explanations for this as weU as the physical plasticization steps. 

The explanation is almost the same as that for the transverse modulus the cell walls bend like beams, and collapse occurs when these beams reach their plastic collapse load. As with the moduli, moisture and temperature influence the crushing... 

The second factor listed above that affects the growth of plastics, namely improved capability, is self-explanatory, but the third, the decrease in relative costs for plastics, requires some explanation, particularly as this may have relevance to future prospects. 

Table 3-1 gives typical mechanical property data for four materials, the exact values of which are unimportant for this discussion. Aluminum and mild steel have been used as representative metals and polypropylene (PP) and glass fiber-TS polyester reinforced plastics (GRP) as representative plastics. Higher-performance types could have been selected for both the metals and plastics, but those in this table offer a fair comparison for the explanation being presented. 

In the following list of materials brief explanations of performances and limited applications are given for a few of the different plastics. What is presented will provide some degree of familiarity with the variations of properties existing in the different plastics. Throughout this book many different properties are reviewed. The order in which the following descriptions of plastics are arranged... 

Acetylene (ethyne), C2H2, can be polymerized, (a) Draw the Lewis structure for acetylene and draw a Lewis structure for the polymer that results when acetylene is polymerized. The polymer has formula (CH), where n is large, (b) Consider the polymers polyacetylene and polyethylene. The latter has the formula (CH2)W and is an insulating material (plastic wrap is made of polyethylene), whereas polyacetylene is a darkly colored material that can conduct electricity when properly treated. On the basis of your answer to part (a), suggest an explanation for the difference in the two polymers. 

The nice thing about the neural-plasticity hypothesis is that it seems to explain so much. In fact, it is a better explanation of the effects of psychotherapy than of drugs. If recovery from depression depends on learning new ways of thinking, then psychotherapy - and especially cognitive behavioural psychotherapy - ought to be effective, and indeed it is, as we shall see in Chapter 7. The... 

The problem with the neural-plasticity hypothesis is that it does not explain how all of these very different treatments -including drugs that are supposed to have biochemical effects that are directly opposite to each other - produce their hypothesized effects on neural networks. In seeming to explain so much, the neural-plasticity hypothesis (at least as it is used as an explanation of antidepressant treatment) may actually explain nothing at all. And if placebos produce changes in neural plasticity, why bother with antidepressant drugs ... 

When describing the effect of an external force, we must first define the force itself. A lay person s definition of a force is the amount of effort to get the desired effect. As scientists, we need a more precise definition of force. With a precise definition we can understand and quantify the effect of an applied force on a polymeric material. The mathematical definition of force is the work (which is a form of energy) required to move an object over some distance. Another way to define a force is in terms of the acceleration it creates when applied to some object of a mass m. In our everyday experiences, the first explanation is a simple idea to relate to. When we push a stalled car we exert a force on it. We could easily quantify the force from the weight of the car, the slope of the hill it is sitting on, and how far we must push it. Once we begin to talk about forces in polymer systems, the ideas become a bit more complicated. For example, the force required to open a bag of candy is defined by the work required to deform the bag until it ruptures by overcoming the intermolecular forces which hold the plastic together. 

One of the special features is the extensive discussion and explanation of the interdependence between polymer structure, properties, and processing. The book contains numerous application-oriented examples and is presented at an intermediate level for both practicing plastics engineers and advanced engineering students. 

Those possible explanations are investigated in this chapter. We will shortly describe the LCA methodology in Sect. 2. We will review case studies on plastics and printed matter/paper in Sect. 3. In Sect. 4 we will address the data situation for LCI databases and LCIA characterization factors. In Sect. 5 we will come to some conclusions and recommendations. 

In the next section, we will investigate for two materials, plastics and paper, which possible explanations are correct for the invisibility of additives in LCA case studies. 

There is a simpler explanation. The evolutionary path that leads to humans has produced organisms with profoundly plastic, adaptable brains/minds and ways of living. Humans have created societies, and invented technologies and cultures. We, the inheritors of not merely the genes, but also the cultures and technologies of our forebears, are profoundly shaped by them in ways that make our future as individuals, societies, and species, radically unpredictable. In short, the biological nature of being human enables us to create individual lives and collective societies whose futures lie at least in part in our own hands. 

A typical time profile of the excited PMMA-Phe fluorescence intensity decay is shown in Figure 2. The MEK permeation commences at 24 sec. The SPR increases during the plasticization period until it becomes constant, the onset of the steady state. It is characterized by a linear relationship between the amount of solvent absorbed and time. It was determined from a linear regression analysis that the PMMA-Phe fluorescence intensity starts to deviate from linearity at 197 sec. This indicates a decrease in the SPR and/or the unquenched PMMA-Phe. The decrease in SPR is unexpected at this film thickness since the SPR in thicker PMMA-Phe films show no anomaly at 1 /tm. A more plausible explanation is the reduction in available PMMA-Phe, which is expected when the front end of the SCP reaches the substrate. 

In early twentieth century, plastics were largely obtained from natural products and the industry was a minor one. Most of the plastics were discovered by trial and error and no scientific explanation was available for their properties. 

A traditional explanation of solid friction, which is mainly employed in engineering sciences, is based on plastic deformation.12 Typical surfaces are rough on microscopic length scales, as indicated in Figure 3. As a result, intimate mechanical contact between macroscopic solids occurs only at isolated points, typically at a small fraction of the apparent area of contact. 

Most of the personal details collected need no explanation (e.g. height weight number of cigarettes smoked per day). Men were also asked to measure the length and width of their left testis to the nearest millimetre, using plastic callipers. From these measures, testis volume was estimated in cm3, using the equation for an ovoid. 

In a subsequent communication, Elliott and coworkers found that uniaxially oriented membranes swollen with ethanol/water mixtures could relax back to an almost isotropic state. In contrast, morphological relaxation was not observed for membranes swollen in water alone. While this relaxation behavior was attributed to the plasticization effect of ethanol on the fluorocarbon matrix of Nafion, no evidence of interaction between ethanol and the fluorocarbon backbone is presented. In light of the previous thermal relaxation studies of Moore and co-workers, an alternative explanation for this solvent induced relaxation may be that ethanol is more effective than water in weakening the electrostatic interactions and mobilizing the side chain elements. Clearly, a more detailed analysis of this phenomenon involving a dynamic mechanical and/ or spectroscopic analysis is needed to gain a detailed molecular level understanding of this relaxation process. 

Dannenberg s experiments were carried out in a dry environment, and he found results that satisfied Equation (1). These stresses were only slightly relaxed when the sample was placed in a wet environment, showing small plasticization by water, and also this effect was shown to be reversible. Therefore, Dannenberg s satisfaction of Equation (1) was for low plasticization by moisture, putting doubt on Croll s explanation for moisture as the reason for variation between thick and thin coatings. 

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