Plastics orientation

There are different techniques that have been used for over a century to increase the modulus of elasticity of plastics. Orientation or the use of fillers and/or reinforcements such as RPs can modify the plastic. There is also the popular and extensively used approach of using geometrical design shapes that makes the best use of materials to improve stiffness even though it has a low modulus. Structural shapes that are applicable to all materials include shells, sandwich structures, and folded plate structures (Fig. 3-8). These widely used shapes employed include other shapes such as dimple sheet surfaces. They improve the flexural stiffness in one or more directions. 

When articles hitherto produced from classic materials (such as wood or metal) are to be made by the injection molding process, it is advisable, to give serious consideration to the special properties of plastics materials, as well as the more salient points of injection molding as a production method. This plastics-oriented procedure requires an understanding of the basic principles of the manufacturing and production processes involved, and also of the plastics material s behaviour. The book provides a comprehensive overview of the principles involved in injection molding. 

Cellulose thin films for documents and book recovery fibres (including optical) biodegradable plastics oriented templates liquid crystal displays luminescent materials fuel cell membranes drag delivery stents covering ophthalmic, cardiovascular and neurological prostheses bulletproof materials... 

Blends of PE (selected fiom VLDPE and/or LLDPE), with 13-17 wt% ethylene-butene plastomer copolymer [Mitsui s TAFMER , p < 900 kg m , Tn, = 55-85 °C], and 35-50 wt% ethylene-vinyl acetate copolymer, EVAc, were used for film blowing, useful as packaging materials for foods. The film had shrink properties in MD and TD similar to those of EVAc film and plastic orientation properties similar to... 

Fig. 12-4 Effect of injection molding on plastic orientation distribution [6].

Crash-simulation in general is performed with explicit solvers like LS-Dyna, Abaqus/Explicit or PamCrash to include mass inertia into simulation. For thermoplastics it has to be based on an exhaustive, plastics oriented material description that includes elastic and plastic deformation as well as failure. The most important influencing factors on the mechanical material behavior of non-reinforced thermoplastics under high deformation speeds are the strain-rate dependency and the non-linear behavior during plastic deformation. A failure criterion has to be applied in order to reflect the amount of energy the material can absorb through deformation until it fails. 

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]. 

Spencer, R. D. The Dependence of Strength in Plastics upon Polymer Chain Length and Chain Orientation, /. Chem. Educ. 1984, 61, 555-563. 

Because of projected nylon-6,6 growth of 4—10% (167) per year in the Far East, several companies have announced plans for that area. A Rhc ne-Poulenc/Oriental Chemical Industry joint venture (Kofran) announced a 1991 startup for a 50,000-t/yr plant in Onsan, South Korea (168,169). Asahi announced plans for a 15,000-t/yr expansion of adipic acid capacity at their Nobeoka complex in late 1989, accompanied by a 60,000-t/yr cyclohexanol plant at Mizushima based on their new cyclohexene hydration technology (170). In early 1990 the Du Pont Company announced plans for a major nylon-6,6 complex for Singapore, including a 90,000-t/yr adipic acid plant due to start up in 1993 (167). Plans or negotiations for other adipic acid capacity in the area include Formosa Plastics (Taiwan) (171) and BASF-Hyundai Petrochemical (South Korea) (167). Adipic acid is a truly worldwide... 

Polymer Composition. The piopeities of foamed plastics aie influenced both by the foam stmctuie and, to a gieatei extent, by the piopeities of the parent polymer. The polymer phase description must include the additives present in that phase as well. The condition or state of the polymer phase (orientation, crystallinity, previous thermal history), as well as its chemical composition, determines the properties of that phase. The polymer state and cell geometry are intimately related because they are determined by common forces exerted during the expansion and stabilization of the foam. 

In the presence of external forces, plastic foams in which the cells are elongated or flattened in a particular direction may be formed. This cell orientation can have a marked influence on many properties. The results of a number of studies have been reviewed (59,60). 

In another extractor (Automatic Machinery and Electronics Inc. (AMC)) the individual fmits are cut in half as they pass a stationary knife. The halves are oriented in a vertical plane, picked up by synthetic mbber cups, and positioned across plastic serrated reamers revolving in a synchronized carrier in a vertical plane. As the fmit halves progress around the extractor turntable, the rotating reamers exert increasing pressure and express the juice. The oil and pulp contents in the juice increase with greater reaming pressure. The recoverable oil is removed in a separate step prior to juice extraction. Needle-sharp spikes prick the peel of the whole fmit, releasing oil that is washed away with water and recovered from the oil—water emulsion. 

Mechanical Properties and Structural Performance. As a result of the manufacturing process, some cellular plastics have an elongated cell shape and thus exhibit anisotropy in mechanical, thermal, and expansion properties (35,36). Efforts are underway to develop manufacturing techniques that reduce such anisotropy and its effects. In general, higher strengths occur for the paraHel-to-rise direction than in the perpendicular-to-rise orientation. Properties of these materials show variabiUty due to specimen form and position in the bulk material and to uncertainty in the axes with respect to direction of foam rise. Expanded and molded bead products exhibit Httie anisotropy. 

Laminates ate a special form of composite material or reinforced plastic because the continuous reinforcing ply of fibrous material imparts significant strength in the x—j plane. The strength along the axis results from interlaminar bonding of resins. Very few fibers ate oriented in the direction, so it tends to be the weak link in this type of composite. 

As the nonwoven fabrics industry has matured and technology has become pubHcly available, emphasis in the various sectors of the industry has changed. In the 1990s, some portions of the nonwovens industry are technology driven, whereas others are market driven. A number of firms are proprietary technology based, and others are turn-key plant operations. Some corporations are commodity roU-goods producers, and others are more oriented to niche market, high value-added products. Many nonwoven produces continue the quest for new markets and more opportunities to compete with textiles, paper, and plastics. 

Prior to deposition on a moving belt or screen, the molten polymer threads from a spinnerette must be attenuated to orient the molecular chains of the fibers in order to increase fiber strength and decrease extendibiUty. This is accompHshed by hauling the plastic fibers off immediately after they have exited the spinnerette. In practice this is done by accelerating the fibers either mechanically (18) or pneumatically (17,19,20). In most processes, the fibers are pneumatically accelerated in multiple filament bundles however, other arrangements have been described wherein a linearly aligned row(s) of individual filaments is pneumatically accelerated (21,22). 

A.STM D2838, Test Methodfor Shrink Tension and Orientation Eelease Stress of Plastic EUrn and Thin Sheeting, Vol. 8.02, ASTM, Philadelphia, Pa., 1989. 

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