Plastics. Also

Table 1 shows that most acryflcs have low glass-transition temperatures. Therefore, in copolymers they tend to soften and flexibHize the overall composition. Plasticizers also lower the transition temperature. However, unlike incorporated acryflc comonomers, they can be lost through volatilization or extraction. 

Secondary Plasticizers. Also known as extenders, secondary plasticizers continue to play a significant role ia flexible PVC formulations. They do not impart flexibiHty to the PVC resia alone, but when combiaed with a primary plasticizer act ia such a way as to add flexibiHty to the final product. 

Plasticizers. Addition of plasticizers (qv) to polyether elastomers alters physical properties, improves processing, and can improve low temperature flexibiUty. Plasticizers also reduce vulcanizate costs by allowing the use of higher levels of less expensive fillers. 

Plastics also find increasing use in vehicles for both water and air transport. Glass-fibre-reinforced plastic boats are widely used as a result of their economy in manufacture, ease of maintenance, lightness of weight and, for military purposes, antimagnetic characteristics. The non-corrosive nature of plastics also leads to their widespread use in boat fixtures and fittings. In aircraft, plastics are particularly useful on account of their low density. 

Chemical that acts as a stabilizer by chemically combining with an acid that may be present initially in trace quantities in a plastic also may be formed via decomposition of the resin. 

Plastics also have the ability to recover when the applied stress is removed and to a first approximation this can often be considered as a reversal of creep. This was illustrated in Fig. 1.8 and will be studied again in Section 2.7. At present it is proposed to consider the design methods for plastics subjected to steady forces. 

Small amounts (usually <10%) of plasticizer could be used in the blending system to improve the processing properties of the material by lowering the melting and glass-transition temperatures. The addition of liquid plasticizer also makes the material soft but at the same time, the strength and toughness of the material decreases. 

Methods are used to produce the more costly rapid prototypes include those that produce models within a few hours. They include photopolymerization, laser tooling, and their modifications. The laser sintering process uses powdered TP rather than chemically reactive liquid photopolymer used in stereolithography. Models are usually made from certain types of plastics. Also used in the different processes are metals (steel, hard alloys, copper-based alloys, and powdered metals). With powder metal molds, they can be used as inserts in a mold ready to produce prototype products. These systems enable having precise control over the process and constructing products with complex geometries. 

Fig. 4-9 Over 26% of this McDonald-Douglas AV-8B Harrier aircraft s weight uses carbon fiber-epoxy reinforced plastic other plastics also used extensively.

The term s plastic, polymer, resin, elastomer, and reinforced plastic (RP) are some-what synonymous. However, polymer and resin usually denote the basic material. Whereas plastic pertains to polymers or resins containing additives, fillers, and/or reinforcements. Recognize that practically all materials worldwide contain some type of additive or ingredient. An elastomer is a rubberlike material (natural or synthetic). Reinforced plastics (also called composites although to be more accurate called plastic composites) are plastics with reinforcing additives, such as fibers and whiskers, added principally to increase the product s mechanical properties. 

Plastic also refers to a material that has a physical characteristic such as plasticity and toughness. The general term commodity plastic, engineering plastic, advanced plastic, advanced reinforced plastic, or advanced plastic composite is used to indicate different performance materials. These terms and others will be reviewed latter in this chapter. Plastics are made into specialty products that have developed into major markets. An example is plastic foams that can provide flexibility to rigidity as well as other desired properties (heat and electrical insulation, toughness, filtration, etc.). 

Barrier plastic Also called barrier layer. They are materials such as plastic films, sheets, etc. with low or no permeability to different products. 

In summary, the attributes of the elastomer that contribute to the enhanced impact strength of a plastic in plastic mbber blend include the type of mbber, plastic to mbber ratio, particle size, particle size distribution, cross-Unk density, and degree of grafting, if any. Molecular weight and molecular weight distribution of the plastic also exert some influence. For example, for high-impact PS, the optimal molecular weight of PS is between 170,000 and 220,000. The dispersity index is... 

Plastics also make it possible to re-examine the policy of medical wastes. The incineration of plastics, provided these resins are incinerated with negligible impact on the environment, poses fewer problems than the incineration of glass, which leaves significant residues. 

Some liquid nitro compounds have found past use in explosive compositions. A mixture of 2,4-dinitroethylbenzene and 2,4,6-trinitroethylbenzene, known as K-10, currently finds use as an energetic plasticizer in some propellant formulations. K-10 plasticizer, also known as Rowanite 8001, is manufactured by Royal Ordnance in the UK and also finds use as a plasticizer in PBXs. 

Uses. As a curing agent for epoxy and other resins and as a vinyl plasticizer also found in anticorrosive surface coatings, polymers, paints, dyes, and pharmaceuticals... 

External plasticizers are not permanent. Plasticizer molecules associate with one another eventually creating preferred migration routes to the material s surface where the plasticizer is rubbed or washed away. The preferential association of plasticizers also leaves some sites less flexible and creates variations in the material s stress-strain and expansion-contraction behaviors. 

The steady-state luminescence spectra of three different plastics are characterized by blue luminescence with Amax = 445-465 nm, while much broader liuninescence band with yellow color characterizes the dolomite rocks. These spectra are different, but not enough to differentiate between them from big distance. The decay properties have been also checked in order to improve the selective feature. It was found that luminescence intensity of rocks in the blue part of the spectrum is drastically diminished after specific delay time, while the decrease of intensity in the yellow part of the spectrum is mush more moderate. Liuninescence intensity of all plastics also diminishes after such delay, nevertheless remaining mush stronger then intensity of rocks luminescence in the blue part of the spectrum. The comparison of plastic and rock time-resolved spectra in specific time window clearly demonstrate that they are absolutely different, which made confident discrimination possible (Fig. 7.3). 

The energetic plasticizers also enhance flexibility and elasticity in addition to increase in the overall energy of a system and its spontaneous ignition properties. In explosives and propellants, they are preferred over non-energetic plasticizers... 

Paramount among the outlets for petroleum raw materials outside the field of fuels and lubricants are the elastomers and plastics. It is expected that synthetic rubber production in 1951 will exceed 800,000 long tons (1.8 billion pounds) while, during the same period, nearly two billion pounds of plastics also will be produced. It has been demonstrated to the American consumer that synthetic rubber is equal or superior to the natural product for many applications, and plastic products such as nylon fabrics, polyvinyl chloride upholstery, and polystyrene toys and gadgets are now considered a part of our way of life. 

A distinction should be made between solvent plasticizers and nonsolvent plasticizers. With an amorphous polymer, any plasticizer is a solvent plasticizer— i.e., under suitable conditions the polymer would eventually dissolve in the plasticizer. With a crystalline or semicrystalline polymer, there are some compounds which enter both the crystalline (ordered) and the amorphous (disordered) regions. These are true plasticizers-sometimes they are called primary plasticizers. If, on the other hand, only the amorphous regions are penetrated, the compound may be considered as a nonsolvent plasticizer, also known as a secondary plasticizer, or softener. Such softeners are used sometimes as diluents for the primary plasticizer. 

In summary, our studies have show n that graft copolymers of PVN with PEO form homogeneous, rubbery materials. The properties of copolymers having low PEO content remain to be investigated to evaluate the use of PEO as an internal plasticizer. Also, the effect of the size of side chains will have to be considered. 

The polycarbonate films containing the additives were completely transparent, and x-ray diffractometric curves gave no indication of crystallinity. Films with a thickness of about 2 mils could be tightly creased without cracking, but 3- to 4-mil films often cracked under these conditions. Film properties of the polymers from bisphenols I and II and from bisphenol A are listed in Tables I to III, respectively. Some conventional plasticizers also are listed at the bottoms of the tables to show their effect on the film properties. 

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