Plastic selection

Plastics, such as PE, PP, polystyrene (PS), polyester, and nylon, etc., and elastomers such as natural rubber, EPDM, butyl rubber, NR, and styrene butadiene rubber (SBR), etc., are usually used as blend components in making thermoplastic elastomers. Such blends have certain advantages over the other type of TPEs. The desired properties are achieved by suitable elasto-mers/plastic selection and their proportion in the blend. 

If the wire is to be used to carry much higher frequency currents, the design problem in geometry and plastic selection becomes more complicated. The dielectric constant and dielectric loss values for the plastics become important in the design. At a frequency of one megahertz the effect of the dielectric on the power transmission behavior of the wire is substantial and, even at frequencies of 10 to 100 kilohertz, the insulation on the wire must be considered in the design as a major electrical element in the circuit. More on the subject of insulation will be following this section. 

Table 7-20 Plastic selection guide based on different properties... 

Rosato, D. V., Product Design Plastic Selection Guide, SPE ANTEC, May 1990. 

Plasticizers. With over 300 chemical moieties to choose from, plasticizer selection is complex. Some reason for specific choice may become apparent if these materials are divided into general classes, and their contribution, good and bad, to ultimate performance is noted. 

Plastic selection ultimately depends upon the performance criteria of the product that usually includes aesthetics and cost effectiveness. Analyzing how a material is expected to perform with respect to requirements such as mechanical space, electrical, and chemical requirements combined with time and temperature can be essential to the selection process. The design engineer translates product requirements into material properties. Characteristics and properties of materials that correlate with known performances are referred to as engineering properties. They include such properties as tensile strength and modulus of elasticity, impact, hardness, chemical resistance, flammability, stress crack resistance, and temperature tolerance. Other important considerations encompass such factors as optical clarity, gloss, UV stability, and weatherability.1 248>482... 

Journal of Materials Science. Materials in Medicine 14, No.10, Oct.2003, p.905-12 BLOOD RESPONSE TO PLASTICIZED POLYVINYL CHLORIDE. DEPENDENCE OF FIBRINOGEN ADSORPTION ON PLASTICIZER SELECTION AND SURFACE PLASTICIZER LEVEL... 

Typical industrial plastic selection criteria have focused on pin-on-disk tests (involving plastic sliding over steel) and sand slurry abrasion tests. The CMP environment, however, is very different from these typical industrial tests. In CMP, the retaining ring plastic is subjected to a plastic-to-plastic adhesive force component involving the polyurethane pad, chemical attack from the chemicals in the slurry, as well as an abrasive component associated with slurry particles. 

Since plasticizers are typically incorporated into film coating formulations in significant concentrations, their inclusion commonly affects the permeability of polymer films and consequently drug release from coated substrates. Therefore, plasticizer selection for film coating applications mu.st be carefully considered as plasticizers substantially... 

In a study by Bodmeier et al., it was demonstrated that plasticizer selection strongly influenced the rate of theophylline release in 0.1N HCl from beads coated with Aquacoai ECD (68). The results of this. study are shown in Figure 11. From this figure it can be seen that incomplete film formation resulted from plasticization with triacetin as a result of incompatibility between the hydrophilic plasticizer and the hydrophobic ethylcellulose latex particles. Complete film formation was achieved with all other investigated plasticizers TEC, Myvacet, tributyl citrate, DBS, and acetyl tributyl citrate however, faster drug release was seen with TEC due to the water solubility of TEC versus the water-insolubility of the other investigated plasticizers. 

The selection of the proper plastic for a given corrosion environment is not a simple process. It requires careful analysis of the properties of the plastic contemplated. Equally importantly, it requires careful analysis of what is to be protected (tanks, exhaust systems, piping, etc.) and the environment to which they are being subjected. The following "check points" will be of assistance in establishing the environment to which the plastic will be subjected and the subsequent plastic selected. 

Clearly, the problem originates from the poor melt flowability of the composition at the processing conditions and can be preventively identified by considering rheology of the filled composition, or maybe even of the plastic itself, at an earlier step of plastic selection. 

Impact resistance for a system containing 50% PMM, 25% PS, and 25% block copolymer PS-PMM (42% PS, Mn = 120,000) is plotted in Figure 6. PS, the dispersed phase of the system, was plasticized selectively with increasing amounts of diisobutylazelate. Impact resistance is maximum when the amount of plasticizer is 50% with respect to the dispersed PS phase. 

The conflict betweai low creep and high impact strength mentioned earlier is not confined to fibers, but is also a problem encountered in plastic selection. It is an important point to consider for the engineering requirements of the material when... 

The above table shows that a large number of products manufactured from PVC require plasticizers. The table also shows that there is a large variety of plasticizers (the Plasticizers Database contains 1475 plasticizers). The data ranges of properties included at the end of Table 3.1 show that there is a variety of choices to fulfil requirements, but the section Potential adverse effects also shows that not very well thought-out plasticizer selection may affect the properties of the end product. 

It starts in plastic selection and modification to provide either high or low friction as required by the application. There is also determining... 

Follow by determining the specific plastic within the plastic group selected. The plastic with the lowest final total will be the best for the application on a cost-performance basis. Tables 9.10 and 9.11 are examples in the plastic selection of a chain saw and pump. 

Over the past decade, researchers and citizen advocates have developed several tools to assist in decision making about plastics selection. The plastics pyramid (Fig. 5.1] developed by Thorpe and Van der Naalde in 1998 was an early attempt to visually display the life cycle hazards of different plastics to assist in materials selection. This ranking focused on the toxicity of the material, considering production hazards, use of harmful additives, hazards in use, and disposal hazards. In this pyramid, bio-based polymers form the bottom of the pyramid, indicating they are most preferable, as they are made from renewable resources, and theoretically are biodegradable and compostable (Rosalia et al., 2012]. 

The thermal properties of plastics, particularly Tg, influence process-ability in many different ways. Plastic selection should take these properties into account. A more expensive plastic could cost less to process because of a shorter processing time, requiring less energy per pound. 

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