Plastics physical nature

Uses. Phthabc anhydride is used mainly in plasticizers, unsaturated polyesters, and alkyd resins (qv). PhthaUc plasticizers consume 54% of the phthahc anhydride in the United States (33). The plasticizers (qv) are used mainly with poly(vinyl chloride) to produce flexible sheet such as wallpaper and upholstery fabric from normally rigid polymers. The plasticizers are of two types diesters of the same monohydric alcohol such as dibutyl phthalate, or mixed esters of two monohydric alcohols. The largest-volume plasticizer is di(2-ethylhexyl) phthalate [117-81-7] which is known commercially as dioctyl phthalate (DOP) and is the base to which other plasticizers are compared. The important phthahc acid esters and thek physical properties are Hsted in Table 12. The demand for phthahc acid in plasticizers is naturally tied to the growth of the flexible poly(vinyl chloride) market which is large and has been growing steadily. 

An important subdivision within the thermoplastic group of materials is related to whether they have a crystalline (ordered) or an amorphous (random) structure. In practice, of course, it is not possible for a moulded plastic to have a completely crystalline structure due to the complex physical nature of the molecular chains (see Appendix A). Some plastics, such as polyethylene and nylon, can achieve a high degree of crystallinity but they are probably more accurately described as partially crystalline or semi-crystalline. Other plastics such as acrylic and polystyrene are always amorphous. The presence of crystallinity in those plastics capable of crystallising is very dependent on their thermal history and hence on the processing conditions used to produce the moulded article. In turn, the mechanical properties of the moulding are very sensitive to whether or not the plastic possesses crystallinity. 

The quality of the fiber matrix interface is significant for the application of natural fibers as reinforcement fibers for plastics. Physical and chemical methods can be used to optimize this interface. These modification methods are of different efficiency for the adhesion between matrix and fiber. 

This paper deals with the plate-out characteristics of a variety of materials such as metals, plastics, fabrics and powders to the decay products of radon and thoron under laboratory-controlled conditions. In a previous paper, the author reported on measurements on the attachment rate and deposition velocity of radon and thoron decay products (Bigu, 1985). In these experiments, stainless steel discs and filter paper were used. At the time, the assumption was made that the surface a-activity measured was independent of the chemical and physical nature, and conditions, of the surface on which the products were deposited. The present work was partly aimed at verifying this assumption. 

A third issue arises with NCEs that bind to plastic surfaces due to the hydrophobic physical nature of the molecule. A significant loss due to this type of non-specific binding to the Caco-2 device may lead to underestimation of permeability. Addition of protein (e.g., bovine serum albumin) in the receiver compartment appears to be capable of preventing some non-specific binding [23],... 

The solubility of sterilising gases in polymers is important in determining the retention of residues which may, as in the case of ethylene oxide residues, be toxic. The quality control problems of polymers and plastics are considerable. Both the chemical and physical nature of the material has to be taken into account, as well as purity. 

Semi-synthetic plastics are natural polymers which have been treated chemically to modify their properties with the aim of producing physically stable, mouldable products. The Swiss chemist, Schonbein, unwittingly prepared the first semi-synthetic polymer by treating paper (cellulose) with a mixture of nitric and sulphuric acids in 1846. The resulting cellulose nitrate was soluble in organic liquids and was softened by heat. It was highly flammable and only thought to be useful as an explosive, which was named gun cotton . 

The change of a material over time under defined natural or synthetic environmental conditions, leading to improvement or deterioration of properties. Also, changes caused by exposure to physical and chemical factors (viz., light, temperature, chemicals, weather), leading to irreversible deterioration. A process of exposing plastics to natural or artificial environmental... 

The physical nature of the acetic, propionic, butyric, isobutyric and valeric esters of sucrose ranges from crystalline solids to low-viscosity liquids. As coatings modifiers, the crystalline compounds have a tendency to form crystals within the film while the liquid compounds cause the film to soften as a plasticizer would do. In the search for a coatings modifier which would perform as an extender, mixed esters were investigated. It was discovered that the completely esterified mixed acetic and isobutyric ester of sucrose produced some unusual properties alone and also when combined with various film formers. A major aspect of sucrose acetate isobutyrate (SAIB) is its capability of extending polymers to... 

It is said that polyvinylchloride is a particular polymer which can be continuously transformed from rigid-state to flexible-state with a proper quantity of plasticizer which is necessary to be used in itself. However, plasticizer is essentially apt to bleed out and is not so good for the physical nature after long periods of outdoor exposure. 

Below we consider the results of our systematic research of deformation kinetics for glassy polymers over the wide ranges of temperatures and deformations, using the laser-interferometric technique under consideration [11,278,280-287], This research allowed us (1) to study the dependencies of kinetic parameters of creep on these factors, (2) to reveal the regular relations between the activation parameters of polymer creep, (3) to demonstrate their intimate connection with the parameters of relaxation transitions, and (4) to confirm directly the intermolecular physical nature of potential barriers of polymer plasticity. ... 

Degradation mechanisms of the polymeric matrices and the contamination effects due to migration of additives coming from the plastics into the fuel cell environment are significant concerns for the choice of bipolar plate materials. For a deeper understanding of the relevant processes a brief introduction of the chemical and physical nature of polymers is necessary. 

Food. The primary use of chicle is as the gum base in chewing gum its use level in chewing gum is about 20%. The rest of the chewing gum is sugar and corn syrup, with small amounts of flavorings. This gum is not a true gum (see glossary) but is close in chemical and physical nature to natural rubber and resins hence it is soft and plastic when chewed and is reportedly not soluble in saliva. 

When plastics are brought in contact with physically active media, the latter can penetrate into the polymer microstructure as well as into microscopic defects or sink holes and reduce the intermolecular bond forces, thus increasing macro-molecular mobility. The consequences include swelling, reduction in the modulus of elasticity, glass transition temperature, strength and hardness, influence on electrical properties, changes in dimensions and discoloration. These processes are of a physical nature and mostly reversible, unless polymer components have been extracted and the structure has changed, e.g., because of secondary crystallization [502]. 

All reversible processes of a physical nature can be reversed to some extent, i.e., the solvent molecules can be extracted by drying at elevated temperatures and/or reduced pressure so that the swelling recedes. Plastics treated in this manner often indicate only minor changes in their properties compared to their original condition. However, if the result is removal of plasticizers or other additives, properties may decrease. 

Creep rupture strength of plastic pipes depends on the acting medium influences can be of chemical or physical nature and both types of influence often act simultaneously [810]. 

The action of particulate fillers on a thermoplastic is dependent on factors that can be classified as extensity, intensity and geometrical factors. The extensity factor is the amount of filler surface area per m of the composite in contact with the plastic. The intensity factor is the specific activity of this solid surface per m of interface, determined by the chemical and physical nature of the filler surface in relation to the plastic. Geometrical factors are the structure including shape of filler (anisotropic such as such as lamellar, plate, needle and isotropic such as spherical), their particle size and size distribution as well as porosity. Among those the chemical nature of the filler surface plays most vital role in determining the degree of plastic-filler interaction. 

Emulsion Adhesives. The most widely used emulsion-based adhesive is that based upon poly(vinyl acetate)—poly(vinyl alcohol) copolymers formed by free-radical polymerization in an emulsion system. Poly(vinyl alcohol) is typically formed by hydrolysis of the poly(vinyl acetate). The properties of the emulsion are derived from the polymer employed in the polymerization as weU as from the system used to emulsify the polymer in water. The emulsion is stabilized by a combination of a surfactant plus a coUoid protection system. The protective coUoids are similar to those used paint (qv) to stabilize latex. For poly(vinyl acetate), the protective coUoids are isolated from natural gums and ceUulosic resins (carboxymethylceUulose or hydroxyethjdceUulose). The hydroHzed polymer may also be used. The physical properties of the poly(vinyl acetate) polymer can be modified by changing the co-monomer used in the polymerization. Any material which is free-radically active and participates in an emulsion polymerization can be employed. Plasticizers (qv), tackifiers, viscosity modifiers, solvents (added to coalesce the emulsion particles), fillers, humectants, and other materials are often added to the adhesive to meet specifications for the intended appHcation. Because the presence of foam in the bond line could decrease performance of the adhesion joint, agents that control the amount of air entrapped in an adhesive bond must be added. Biocides are also necessary many of the materials that are used to stabilize poly(vinyl acetate) emulsions are natural products. Poly(vinyl acetate) adhesives known as "white glue" or "carpenter s glue" are available under a number of different trade names. AppHcations are found mosdy in the area of adhesion to paper and wood (see Vinyl polymers). 

Properties. Table 1 hsts many of the physical, thermal, mechanical, and electrical properties of indium. The highly plastic nature of indium, which is its most notable feature, results from deformation from mechanical twinning. Indium retains this plasticity at cryogenic temperatures. Indium does not work-harden, can endure considerable deformation through compression, cold-welds easily, and has a distinctive cry on bending as does tin. 

In addition to time-related effects, the soUd-state physical properties are also affected by adsorbed water, which functions as a plasticizer. Water pickup is affected by the nature of the cation, with sodium ionomers absorbing about 10 times the level of the zinc equivalent (6) under the same conditions. Drying must be carried out at temperatures below 100°C and is therefore a slow process. In commercial practice, ionomers are suppUed dry, and techniques have been developed to minimize moisture absorption during processing. 

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