Laminated structure

A specialized form of the monolithic device consists of several adhered or laminated polymeric layers, which has the active ingredient impregnated in a central layer (active agent reservoir layer) between two outer plastic layers. The inner layer 

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The important point to note from this Example is that in a non-symmetrical laminate the behaviour is very complex. It can be seen that the effect of a simple uniaxial stress, or, is to produce strains and curvatures in all directions. This has relevance in a number of polymer processing situations because unbalanced cooling (for example) can result in layers which have different properties, across a moulding wall thickness. This is effectively a composite laminate structure which is likely to be non-symmetrical and complex behaviour can be expected when loading is applied. 

REQUIRED FIND THE LAMINATE STRUCTURAL CONFIGURATION NECESSARY TO CARRY THOSE LOADS... 

Vermiculite is a naturally occurring group of hydrated aluminum-iron-magnesium silicates having a laminate structure. When subjected to direct heat in a furnace, the pulverized material exfoliates or expands in size, and then consists of a series of parallel plates with air spaces between. 

Developments in glued laminated structures and panel products such as plywood and chipboard raises the question of the durability of adhesives as well as wood. Urea-formaldehyde adhesives are most commonly used for indoor components. For exterior use, resorcinol adhesives are used for assembly work, whilst phenolic, tannin and melamine/urea adhesives are used for manufactured wood products. Urea and casein adhesives can give good outdoor service if protected with well-maintained surface finishes. Assembly failures of adhesives caused by exudates from some timber species can be avoided by freshly sanding the surfaces before glue application. 

The recycled plastic will also have a degree of different contaminants that would eliminate its use in certain devices or products, such as in medicine, electronics, and food packaging. However, within these market applications there are acceptable designs with three-layer coextruded, coinjected, or laminated structures having the contaminated plastic as the center layer, isolated by clean plastics around it and no migration occurring. 

Nylon, aluminum, PVC (OPA-aluminum-PVC) composites offer functional alternatives to traditional ther-moformed materials. With a laminate structure of 25 pm OPA, 45 pm aluminum, with 60 pm PVC (1 mL OPA 1.8 mL aluminum-2.4 mL PVC), it is possible to almost completely eliminate water-vapor permeability [25]. 

Thus, any laminate may consist of plies selected from paper, polyester, numerous other plastic films, foils, coatings, adhesive layers, metalization, etc. The choice of laminate structure is usually governed by technical requirements, cost of base materials, cost of lamination processes, cost of printing cylinder and process, and the amount of laminate required (quantity), the yield from which the cost per area of laminate is derived. 

According to filler theory, connectivity can be achieved at lower values when the filler form is plates rather than spheres. Depending on the proportions of the plates and whether or not an inactive phase is included in the blend, connectivity can be achieved at 8 to 16% (v/v) filler (4). The starch-plastic blends developed by Otey (2) have a laminate structure when the starch content is under 30% by volume (Figure 1) and the threshold for microbial attack on these materials is under 13% starch by volume (Figure 2). This low threshold value can be explained by considering the LDPE as a non-conductive (enzyme-impermeable) phase combined with a conductive phase of starch-EAA complex. 

Cellulose, which is more fibrous than wood flour, is used as a filler for urea and melamine plastics. Melamine dishware is a laminated structure consisting of molded resin-impregnated paper. Starch and soybean derivatives are biodegradable, and the rate of disintegration of resin composites containing these fillers may be controlled by the amount of these fillers present in polymers. 

The process by which a thermoplastic matrix composite consolidates to form a laminated structure has been attributed to autohesive bond formation at the ply interfaces. Autohesive bond formation is controlled by two mechanisms (1) intimate contact at the ply interfaces, and (2) diffusion of the polymer chains across the interface (healing). The rate of autohesive bond formation and hence the speed of the composite consolidation process is directly related to the temperature-pressure-time processing cycle. 

Tack (or building tack) A property of an elastomer or rubber compounds that causes two layers of compound that have been pressed together to adhere firmly in the areas of contact. It is very important for building tires or other laminated structures. 

Wood (qv) is aiguably the oldest building material used by humans to construct their dwellings. It is a natural product obtained from trees, used in both structural and decorative applications. The chemical composition of wood is largely cellulose (qv) and lignin (qv). Today there are a variety of composite or reconstituted wood products, such as plywood, particle board, wood fiber boards, and laminated structural beams, where small pieces of wood or wood fiber are combined with adhesives to make laiger sheets or boards (see Laminates). 

With increasing rank, the differences between macerals become progressively smaller in electron as in light microscopy. Exinite in particular becomes difficult to distinguish in medium volatile coals, and could not be positively identified in the electron micrographs of low volatile bituminous coals so far examined. Similarly, the laminate structure of vitrinite described above could not be observed in low volatile bituminous coals. 

Figure 4-9 A scanning tunneling microscopic (STM) image of three glycogen molecules. The corrugated surface suggests a laminated structure. These molecules have been purified from tissues by treatment with strong alkali, which breaks the larger aggregates into particles of Mr = 1-10 x 106 and diameter 25 -30 nm. Courtesy of Fennell Evans.93...

There are four major types of barrier materials used now in the US for military purposes a)Water-proof b)Greaseproof c)Water-vapor-proof and d) Combinations of a,b c. Almost all the barrier materials in use today are composed of several layers or plies. The plies are usually cemented together with suitable adhesives(/< mi anrs) to form a laminated structure, although several other methods of making multi-ply sheets are also used. Materials used for making plies include kraft paper, cotton scrim, aluminum foil, polyethylene, cellulose acetate, Mylar, etc... 

The process of mould filling should not be considered as completely understood and controlled 98>, though some important features of gas-filled system flow were established by Fridman and co-workers 99 100) who have explained the formation of laminated structures in low-pressure moulding of foaming melts and found the correlation between moulding conditions and morphologic macro-structure and properties of foam articles. 

M 1] [P 1] Microscopic observations of the flow were made to detect the changes induced by switching on an electric field for DC operation [91]. Initially a bi-laminated structure resulted owing to the T-junction contact. When the fluids passed the region of the adjacent electrodes, perturbations of the flow became clearly visible, i.e. the interfaces were deformed. The result was a color, i.e. species, distributed in a cross-sectional direction. 

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