Chemical composition plasticity affected

Many materials used for food and beverage packaging have characteristic odors or sensory active compounds (Torri et ah, 2008). The intensity and description of the odor may be affected by the number and type of volatile compounds that are released under environmental conditions at the time of evaluation. Chemical composition of the material and polymer morphology may play a role in the sensory characterization. Sensory descriptors do not define a specific chemical compound but may be related to different compounds, a blend of compounds, and even a limited concentration range of a compound or class of compounds. For example, frans-2-nonenal in water changes in sensory (taste) description from "plastic (0.2 gg/1) to "woody" (0.4-2.0 p.g/1), "fatty" (8-40 pg/1), and "cucumber" (1000 gg/1) (Piringer and Ruter, 2000). Such terms are descriptive of the sensation and perception by human response to the chemical stimuli (Table 2.1). 

All other conditions being the same (chemical composition, volumetric weight, closeness of cells), the cell size can considerably affect the properties of foamed plastics. For instance, the thermal conductivity coefficient of foams always increases when the cell size increases due to the growing number of radiation and convection paths of heat transfer (for more information see Sect. 12). An increase of the... 

The chemical composition, the physical form, and the manner and arrangement in which plastics are stored greatly affect the degree of fire hazard that is present. Large quantities of smoke are usually generated when stored plastics are involved in fire, a condition made more or less difficult by the amount of ventilation present or available in a given storage area. 

Resistance of plastic piaterials to chemically active media may be affected by the presence of additives such as asbestos fibers [8], lubricants [2], or fillers. Effects of fillers depend on their nature and on their content in the plastic material [9-12]. But, in general, the resistance of a plastic to chemically or physically active media depends above all on the chemical composition and the structure of the basic polymer, on the temperature, and on other factors. 

Chemical Composition. Along with additives such as plasticizers and moisture content, the chemical structure of the macromolecules used as agropolymers also affects their mechanical properties. For starch, the amylopectin... 

An ever-present issue when working with plastics and elastomers is that nearly every one of them is affected by chemicals upon exposure. A chemical environment often poses one of the most demanding tests of a polymer s durability. There are two basic ways that a chemical can affect a polymer chemical and physical. The extent of the impact of the chemicals varies based on a variety of factors. Foremost among these factors are the chemical structure and composition of the polymers, and the properties of the impacting chemical. Increasing the temperature of the environment compounds the effects. There are other factors that influence the severity of the effect of chemicals on plastics and rubbers, which are described in this chapter. 

The thermal degradation of mixtures of the common automotive plastics polypropylene, ABS, PVC, and polyurethane can produce low molecular weight chemicals (57). Composition of the blend affected reaction rates. Sequential thermolysis and gasification of commingled plastics found in other waste streams to produce a syngas containing primarily carbon monoxide and hydrogen has been reported (58). 

The origins and composition of plastics wastes and factors affecting their recycling are discussed. Partieular attention is paid to chemical recycling and incineration, with and without energy recovery, and a number of developments in chemical recycling techniques are examined. 19 refs. 

The dynamic mechanical behavior of most homogeneous and heterogeneous solid and molten polymeric systems or composite formulations can be determined by DMA. These polymeric systems may contain chemical additives, including fillers, reinforcements, stabilizers, plasticizers, flame retardants, impact modifiers, processing aids, and other chemical additives, which are added to the polymeric system to impart specific functional properties and which could affect the process-ability and performance. 

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