Plastics Show, The

Table 4.12 Results of analysis of metal spiked HDPE, PET and PMMA plastics showing the results and percentage recoveries...

FIGURE 1.1 Schematic representation of the structure of plastics, showing the three major types of macromolecular arrangements. Approximately 1 000000 times actual size and greatly simplified. (Crystallites can also occur as the result of chain folding.)... 

Concentrated polymer systems containing plasticizer show the existence of slow and fast relaxations which are temperatnre dependent Slow motions are characteristic of a polymer. Fast reorientations are characteristic of relatively small molecnles of a plasticizer. The dynamics of molecules and their rates of motion can be estimated based on... 

By sorting the plastics, students should recognise common features in how each material is used, as weU as differences between the uses for the different plastics. Showing the different monomers wiU help connect the uses to the formulae. 

Saran plastic shows the lowest permeability to O2, CO2, and very low for water. This feature makes Saran wrap an excellent packaging material for food in which freshness and flavor are to be preserved. 

One more application area is composite materials where one wants to investigate the 3D structure and/or reaction to external influences. Fig.3a shows a shadow image of a block of composite material. It consists of an epoxy matrix with glass fibers. The reconstructed cross-sections, shown in Fig.3b, clearly show the fiber displacement inside the matrix. The sample can be loaded in situ to investigate the reaction of matrix and fibers to external strain. Also absorption and transmission by liquids can be visualized directly in three-dimensions. This method has been applied to the study of oil absorption in plastic granules and water collection inside artificial plant grounds. 

A number of friction studies have been carried out on organic polymers in recent years. Coefficients of friction are for the most part in the normal range, with values about as expected from Eq. XII-5. The detailed results show some serious complications, however. First, n is very dependent on load, as illustrated in Fig. XlI-5, for a copolymer of hexafluoroethylene and hexafluoropropylene [31], and evidently the area of contact is determined more by elastic than by plastic deformation. The difference between static and kinetic coefficients of friction was attributed to transfer of an oriented film of polymer to the steel rider during sliding and to low adhesion between this film and the polymer surface. Tetrafluoroethylene (Telfon) has a low coefficient of friction, around 0.1, and in a detailed study, this lower coefficient and other differences were attributed to the rather smooth molecular profile of the Teflon molecule [32]. 

Fomialdehyde is a basic chemical budding block for the production of a wide range of chemicals finding a wide variety of end uses such as wood products, plastics, and coatings. Table 6 shows the distribution of formaldehyde production in the United States from 1966 through 1989 (115). Production percentages reported in the following discussion are for the United States. 

Phthalocyanine pigments account for approximately 23% of the total worldwide organic pigment consumption of 225,000 tons. Approximately 20,000 t are used in printing inks, 10,000 t in paints, 9,000 t in plastics, 3,000 t in textiles, 7,000 t in dyes, and 2,000 t in specialty uses. Table 1 shows the worldwide distribution of cmde phthalocyanine capacity. The production history of phthalocyanine in the United States from 1980 to 1990 is given in Table 2 (161). The 1990 prices of phthalocyanine blue and green pigments were ca 11—22/kg and 21—27/kg, respectively. 

Polarity Parameter. Despite their appareat simplicity, these parameters, ( ), show a good correlatioa with plasticizer activity for nonpolymeric plasticizers (10). The parameter is defiaed 2ls (j) = [M A j Po)]/1000 where M = molar mass of plasticizer, = number of carboa atoms ia the plasticizer excluding aromatic and carboxyHc acid carbon atoms, and Pg — number of polar (eg, carbonyl) groups present. The 1000 factor is used to produce values of convenient magnitude. Polarity parameters provide useful predictions of the activity of monomeric plasticizers, but are not able to compare activity of plasticizers from different families. 

The Solid—Gel Transition Temperature. This temperature, T, is a measure of plasticizer activity and is the temperature at which a single grain of PVC dissolves ia excess plasticizer. The more efficieat plasticizers show lower values of as a result of their higher solvatiag power. This can be correlated with the ease of processiag of a given plasticizer, but all measurements should be conducted with a control PVC resia siace clearly the choice of resia has an effect here also. 

A range of plasticizer molecule models and a model for PVC have been generated and energy minimized to observe their most stable conformations. Such models highlight the free volume iacrease caused by the mobiHty of the plasticizer alkyl chains. More detailed models have also been produced to concentrate on the polar region of the plasticizer and its possible mode of interaction with the polymer. These show the expected repulsion between areas on the polymer and plasticizer of like charge as weU as attraction between the negative portions of the plasticizer and positive portions of the PVC. 

Plastisol Viscosity and Viscosity Stability. After the primary contribution of the resin type in terms of its particle size and particle size distribution, for a given PVC resin, plastisol viscosity has a secondary dependence on plasticizer viscosity. The lower molecular weight and more linear esters have the lowest viscosity and hence show the lowest plastisol viscosity, ie, plastisol viscosity for a common set of other formulation ingredients... 

Overall Assessment of Properties. Table 3 shows the effect for each criterion of increasing plasticizer concentration, increasing the size of the plasticizer molecule, increasing the linearity of the plasticizer molecule, and changing the acid constituent of the ester. An I indicates improved performance for a particular property, a P indicates poorer performance. I and P in parentheses indicate that any changes tend to be marginal. 

The principal worldwide manufacturers of nylon resins are given in Table 6. Total sales of nylon plastics in the United States and Canada in 1993 were 331,000 metric tons (37). West European sales were 352,000 t and Japanese sales 220,000 t (37). Figure 7 shows how sales in the United States have steadily increased since 1967 (38) and also how the price of nylon-6,6 has changed (39). The effect of the oil price rises, the boom of the mid-1980s, as well as the oil price reduction and the recession that followed are clearly evident. Table 7 shows the variation of price across different polyamide types. 

There are 12 producers of ethylene oxide ia the United States. Table 9 shows the plant locations, estimated capacities, and types of processes employed. The total U.S. production capacity for 1992 was ca 3.4 x 10 metric tons. The percentages of total domestic production made by the air- and oxygen-based processes are ca 20 and 80%, respectively. The largest producer is Union Carbide Corp. with approximately one-third of the United States ethylene oxide capacity. About 94% of domestic ethylene oxide capacity is located on the Gulf Coast near secure and plentiful ethylene suppHes. Plans for additional U.S. production ia the 1990s have been announced by Union Carbide (incremental expansions), Eormosa Plastics (at Pt. Comfort, Texas), and Shell (at Geismar, Louisiana) (101). 

A common use of screw extruders is in the forming and compounding of plastics. Table 20-54 shows typical outputs that can be expected per horsepower for various plastics and the characteristics of several popular extruder sizes. 

But the two curves still do not exactly match, as Fig. 8.7 shows. The reason is a displacement of (for example) u = l f2 in tension and compression gives different strains) it represents a drawing out of the tensile specimen from 1q to 1.5 1q, but a squashing down of the compressive specimen from /q to 0.5/q. The material of the compressive specimen has thus undergone much more plastic deformation than the material in the tensile specimen, and can hardly be expected to be in the same state, or to show the same resistance to plastic deformation. The two conditions can be compared properly by taking small strain increments... 

In making the edge dislocation of Fig. 9.3 we could, after making the cut, have displaced the lower part of the crystal under the upper part in a direction parallel to the bottom of the cut, instead of normal to it. Figure 9.7 shows the result it, too, is a dislocation, called a screw dislocation (because it converts the planes of atoms into a helical surface, or screw). Like an edge dislocation, it produces plastic strain when it... 

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