Plasticity-Controlling Factors

The mechanical behavior of plastics is dominated by such viscoelastic phenomena as tensile strength, elongation at breaks, stiffness, and rupture energy, which are often the controlling factors in a design. The viscous attributes of plastic melt flow are also important considerations in the fabrication of plastic products. (Chapter 8, INFLUENCE ON PERFORMANCE, Viscoelasticity). 

Time, pressure, and temperature controls indicate whether the performance requirements of a molded product are being met. The time factors include the rate of injection, duration of ram pressure, time of cooling, time of piastication, and screw RPM. Pressure requirement factors relate to injection high and low pressure cycles, back pressure on the extruder screw, and pressure loss before the plastic enters the cavity which can be caused by a variety of restrictions in the mold. The temperature control factors are in the mold (cavity and core), barrel, and nozzle, as well as the melt temperature from back pressure, screw speed, frictional heat, and so on in the plasticator. 

The discovery that several controlling factors in decay of polysaccharide -plastic composites are physico-chemical in nature (rather than environmental or biological) should make it possible to develop an accurate simulation model to define structural and biodegradable boundaries to achieve the best balance between the two conflicting requirements. This type of model would facilitate development of materials that are satisfactory by both engineering and biodegradability criteria a model of this type is currently being developed in my laboratory. 

The effect of transportation facilities and rates on plant loeation can be a controlling factor in plant siting. Industries such as the plastic industry, which must deliver many small shipments to various users in the minimum amount of lime, find setting the location near the majority of users mandatoty. 

The influence of factors such as chemical structure, molecular weight, cross-linking and plasticizers in the glass transition of polymers can be related to the changes that they provoke on the free volume fraction, which, as we already know, reaches a critical value at the glass transition temperature. The factors affecting the glass transition can be classified into two types (1) molecular factors, i.e., those related to the chemical structure of the polymer chain, and (2) external or controllable factors. 

Cylinders subject to in-plane shear stresses can also fail in the elastic, inelastic, and plastic range. Though shear buckling is rarely a controlling factor in the design of... 

Stream channel characteristics and adversely affect aquatic plant and terrestrial life. The erosion effects of water can be minimized by mechanical control, varying the employed irrigation technology, reducing the water flow rates, by waterway vegetation or lining by concrete, stone, or plastics. These factors decrease the abiUty of a water flow to detach and move soil particles along surfaces, and increase the resistance of the soil surfaces to the force of the water flow. 

It starts in plastic selection and modification to provide either high or low friction as required by the application. There is also determining the required geometry to supply the frictional force level needed by controlling contact area and surface quality to provide friction level. A controlling factor limiting any particular friction force application is heat dissipation. This is true if the application of the friction loads is... 

Materials used in early respirators were of cellulose fiber. Cellulose, plastic, glass, wool and combinations of two or more of these materials are more common today. A controlling factor is cost. As the filters have a limited life span and reuse is impossible because there is no way to clean them, disposability is a key factor. Two items come into consideration at this point resistance to flow by clogging and channeling. 

Disassembly and recovery for re-use of components, metals, glass, and plastics is a problem when the electronic product has not been designed for efficient recovery. The cost of recycling, no matter how well intentioned, is the controlling factor when processing discarded electronic... 

The furnace process involves injecting low end fraction of cmde oil, eg. Bunker Euel C, into a heated chamber. The temperature, shape of the injectors of the oil, rate of injection, and other factors are controlled to produce black fillers of different particle si2e and stmcture. The particle si2e and stmcture control the reinforcing character of the carbon black. There are 30 common grades of carbon black used in the mbber industry. There are numerous specialty grades produced, and several hundred are used in plastic, conductive appHcations, and other uses. 

Electrical Applications. Plastics are used for electrical insulation, conduit and enclosures, lighting fixtures, and mechanical devices. The most widely used plastic for wire and cable insulation is flexible, plasticized PVC, which constitutes well over half the market in insulating wires for buildings, automobiles, appHances, and power and control lines. Polyethylene is also a factor. Higher performance plastics such as nylon and fluoropolymers also play a smaller role in this area. 

Plasticization Gas solubility in the membrane is one of the factors governing its permeation, but the other factor, diffusivity, is not always independent of solubility. If the solubility of a gas in a polymer is too high, plasticization and swelhng result, and the critical structure that controls diffusion selectivity is disrupted. These effects are particularly troublesome with condensable gases, and are most often noticed when the partial pressure of CO9 or H9S is high. H9 and He do not show this effect This problem is well known, but its manifestation is not always immediate. 

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