Environmental Requirements in Compounding

In addition to developing products to satisfy customers, the environmental implications of the technology must be taken into consideration. The environmental impact on compound development must be viewed in two parts (1) product use and long-term ecological implications (2) health and safety, in both product service and product manufacture. 

An example of the impact of product usage and the environmental implications is tire rolling resistance and its effect on vehicle fuel consumption. Reduction in tire rolling resistance results in a drop in vehicle fuel consumption. This has an immediate impact on the generation of exhaust gases such as carbon monoxide, carbon dioxide, and nitrous oxide. 

The crown area of the tire, which includes the tread and belts, accounts for approximately 75% of the radial passenger tire rolling resistance. Improvements in the hysteretic properties of the tread compound will therefore enable a reduction in tire rolling resistance and consequent improvements in vehicle fuel economy. The crown area and particularly the tread compound also affect the life cycle of the tire. Longer-wearing tires (including retreading) delay the point in time when used tires must enter the solid waste disposal system. 

Critical to a tire s life cycle performance is the ability to maintain air pressure. Tire innerliners composed of halobutyl-based compounds exhibit very low air and moisture permeability. Therefore, tires built with the proper selection of compounds can reduce the rate of premature failure, again delaying entry into the scrap tire and solid waste streams. 

Improved tire designs have enabled reduction in noise levels. This has become an important environmental consideration. Optimum footprint 

TABLE XXXVI Relationship Between HIIR/IIR Content and Permeability, ICP, and Step-Load Endurance 

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I. Introduction n. Polymers in. Filler Systems rv. Stabilizer Systems V. Vulcanization System VI. Special Compounding Ingredients Vn. Compound Development Vm. Compound Preparation DC Environmental Requirements in Compounding X. Summary References... 

Performance requirements, environmental issues, and avaUabUity/cost of the material will mainly drive material requirement in the future. In order to face the huge tire wastage problem causing major hazards to the environment, future development in mbbery materials will be focused on development of thermoplastic polymer so that used polymer could be recovered by thermal treatment and separation, biological degradation by radiation/addition of chemical into the mbber compound that could be activated by exposure to radiation and development of biopolymer. 

Aromatic nitro compounds undergo nucleophilic aromatic substitutions with various nucleophiles. In 1991 Terrier s book covered (1) SNAr reactions, mechanistic aspects (2) structure and reactivity of anionic o-complexes (3) synthetic aspects of intermolecular SNAr substitutions (4) intramolecular SNAr reactions (5) vicarious nucleophilic substitutions of hydrogen (VNS) (6) nucleophilic aromatic photo-substitutions and (7) radical nucleophilic aromatic substitutions. This chapter describes the recent development in synthetic application of SNAr and especially VNS. The environmentally friendly chemical processes are highly required in modem chemical industry. VNS reaction is an ideal process to introduce functional groups into aromatic rings because hydrogen can be substituted by nucleophiles without the need of metal catalysts. 

Similarly, legislation has been, or will be, introduced to deal with the disposal of treated wood waste at the end of a product lifetime. No longer will it be acceptable to dispose of treated wood waste by dumping in landfill. Proper disposal will require the incineration of treated wood waste in appropriate facilities that have the necessary equipment to prevent stack emissions of toxic compounds. This requires expensive investment to build plant that can meet the relevant environmental requirements. Such methods probably represent the best option for the permanent removal of these potential pollutants. The ash generated in these plants may contain high concentrations of arsenic, which will then have to be disposed of as hazardous waste. 

Irrespective of the sources of phenolic compounds in soil, adsorption and desorption from soil colloids will determine their solution-phase concentration. Both processes are described by the same mathematical models, but they are not necessarily completely reversible. Complete reversibility refers to singular adsorption-desorption, an equilibrium in which the adsorbate is fully desorbed, with release as easy as retention. In non-singular adsorption-desorption equilibria, the release of the adsorbate may involve a different mechanism requiring a higher activation energy, resulting in different reaction kinetics and desorption coefficients. This phenomenon is commonly observed with pesticides (41, 42). An acute need exists for experimental data on the adsorption, desorption, and equilibria for phenolic compounds to properly assess their environmental chemistry in soil. 

Let us now evaluate how we can assess the baseline toxicity of organic chemicals in a quantitative way. We have already mentioned that certain membrane functions may be disrupted if a chemical occupies a certain volume fraction of that membrane. This means that for two compounds of the same size, we would anticipate that when they are present at equal concentrations in the membrane they would exert the same effect. Furthermore, since the majority of chemicals of interest to us do not differ in size by more than a factor of 3 to 4 (compare molar volumes in Chapter 5, e.g., Fig. 5.2), the membrane concentration required for any compound to cause a narcotic effect will be in the same order of magnitude. Therefore, we may expect that the concentration of a compound required in an environmental medium (e.g., water, air) to cause a narcotic effect in an organism should be inversely proportional to the tendency of the compound to accumulate from that medium into biological membranes. 

Removing benzene and other aromatic compounds from a plant s effluent water is an increasingly common environmental requirement. This is typically achieved with a steam stripper. There is a rather neat trick, which can increase the stripper s efficiency adding saltwater to the stripper feed. Aromatics, especially benzene, are far less soluble in brine than they are in freshwater. But, of course, the brine will be more corrosive than salt-free freshwater. 

The fact that only naked molecules are refined is based on the problem that for crystal lattices at least 27 unit cells would have to be included (with at least one unit per cell, including counter ions and solvents of crystallization), and in solution at least 200 molecules of water must be refined in the solvent sheath interacting with the compound to be modeled. Since CPU time f(m2), where m is the number of nuclei, the time required for a single optimization cycle increases dramatically under these conditions. Even more importantly, the initial configuration of the molecule and its environment is not easy to predict since the intermolecular contacts (crystal lattice, ion-pairing and solvation) of a compound to be modeled are not known beforehand. Thus, inclusion of environmental effects in modeling studies has necessitated the use of some severe approximations176-781. 

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