Polymers and Energy

Energy has always been an important cost element in polymer production, but the world modeling exercises of the 1960s drew attention to the limited availability of fossil energy and for the first time highlighted potential conservation problems [1, 2], The oil crises of the mid-1970s sharply focused the dependence of most industries on oil and firmly put oil and gas on the conservation agenda. 

Plastics and the Environment, Edited by Anthony L. Andiady. ISBN 0-471-09520-6 2003 John Wiley Sons, Inc. 

Energy used by any transport operations within the processing sequence 

Energy equivalent of any feedstock taken into the system 

Energy used by the fuel producing industries in supplying components 1-3, sometimes referred to as precombustion energy 

Since plastics are generally made from hydrocarbon feedstocks they should be recycled to conserve energy. The most effective 

Burning of plastics is not a favourable option, given the widespread concern over the global increase in carbon dioxide. Nonetheless these materials are potentially useful as fuels, and burying them simply wastes their potential in this respect. On the other hand, burning plastics may release not only CO-j but also trace amounts of other pollutants, all of which are undesirable. 

Since plastics are generally made from hydrocarbon feedstocks they should be recycled to conserve energy. The most effectives energy conservation is to refabricate plastic items, though this is not always technically feasible. Under circumstances where recycling is not a feasible option the use of plastics in waste-derived fuels may be an acceptable conservation measure. 

Poly(ethylene terephthalate) Drinks bottles, oven-ready tray meals  

High density poly(ethylene) Bottles for milk and washing-up liquid  

PVC Food trays, cling film, squash bottles.  

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Carbon nanotubes (CNTs) have potential applications in fields such as molecular electronics , conductive polymers , and energy storage. " - - ... 

The complexity of polymeric systems make tire development of an analytical model to predict tlieir stmctural and dynamical properties difficult. Therefore, numerical computer simulations of polymers are widely used to bridge tire gap between tire tlieoretical concepts and the experimental results. Computer simulations can also help tire prediction of material properties and provide detailed insights into tire behaviour of polymer systems. A simulation is based on two elements a more or less detailed model of tire polymer and a related force field which allows tire calculation of tire energy and tire motion of tire system using molecular mechanisms, molecular dynamics, or Monte Carlo teclmiques 1631. 

As already discussed, in general, polymer flow models consist of the equations of continuity, motion, constitutive and energy. The constitutive equation in generalized Newtonian models is incorporated into the equation of motion and only in the modelling of viscoelastic flows is a separate scheme for its solution reqixired. 

A range of plasticizer molecule models and a model for PVC have been generated and energy minimized to observe their most stable conformations. Such models highlight the free volume iacrease caused by the mobiHty of the plasticizer alkyl chains. More detailed models have also been produced to concentrate on the polar region of the plasticizer and its possible mode of interaction with the polymer. These show the expected repulsion between areas on the polymer and plasticizer of like charge as weU as attraction between the negative portions of the plasticizer and positive portions of the PVC. 

Melt Viscosity. The study of the viscosity of polymer melts (43—55) is important for the manufacturer who must supply suitable materials and for the fabrication engineer who must select polymers and fabrication methods. Thus melt viscosity as a function of temperature, pressure, rate of flow, and polymer molecular weight and stmcture is of considerable practical importance. Polymer melts exhibit elastic as well as viscous properties. This is evident in the swell of the polymer melt upon emergence from an extmsion die, a behavior that results from the recovery of stored elastic energy plus normal stress effects. 

Plots of loss modulus or tan 5 vs temperature for polymers give peaks at energy absorbing transitions, such as the glass transition and low temperature secondary transitions (Fig. 20). Such plots are useful for characterizing polymers and products made from them. 

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