Lamination process

The process can be used to recover scrap or low quaUty resins by using them as the core layer, and using outer layers of virgin resins designed for the specific functional needs of the product such as sHp or gloss and appearance. The inner core may be a foamed resin with surface layers of supedor finish resins. Coextmded films often eliminate the need for cosdy lamination processes. 

Free mono- and multilayer films may be adhesive- or extmsion-bonded in the laminating process. The bonding adhesive may be water- or solvent-based. Alternatively, a temperature-dependent polymer-based adhesive without solvent may be heated and set by cooling. In extmsion lamination, a film of a thermoplastic such as polyethylene is extmded as a bond between the two flat materials, which are brought together between a chilled and backup roU. 

By this process lemon oils are found to contain some 2 5 to 3 per cent, aldehydes, hand-pressed lime oil 8 per cent., citron or cedrat oil 4 per cent., and orange oil 0 75 to 1 per cent, but more recent work has shown that these results are somewhat too low, due probably in part to some of the aldehydes distilling over with the terpenes, and for oils containing only a small percentage of aldehydes, a volumetric method, such as the hydroa lamine process, as modified by A. H. Bennet is much to be preferred, as being both simpler and more rapid to carry out, and also. more accurate. 

Transient Heat Conduction. Our next simulation might be used to model the transient temperature history in a slab of material placed suddenly in a heated press, as is frequently done in lamination processing. This is a classical problem with a well known closed solution it is governed by the much-studied differential equation (3T/3x) - q(3 T/3x ), where here a - (k/pc) is the thermal diffuslvity. This analysis is also identical to transient species diffusion or flow near a suddenly accelerated flat plate, if q is suitably interpreted (6). 

Tonkovich, A. L. Y, Roberts, G. L, Fabrication of a stainless steel microchannel microcombustor using a lamination process, in Proceedings of the SPIE Gonference on Micromachined Devices and Gompo-nents IV, pp. 386-392 (September 1998),... 

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. 

In the lamination process, films of different materials are bonded using heat and/ or biodegradable adhesives [23, 34]. A metallized film (e.g., from PLA) with high barrier and stiffness can also be laminated on a Ecoflex /starch or Ecovio compound with good welding performance to produce e.g., a stand pouch for detergents. 

For thick epoxy laminates processed in the autoclave, voids once formed and stabilized can only be removed by dissolution or by resin flow. Furthermore, resin gradients are deleterious to structural laminates. These two key phenomena make an understanding of resin transport vital to the development of any processing model. 

Figure 7.13 Typical scanning acoustic microscopic image obtained from a [0/90.0]r APC-2 laminate processed at 370°C with 276 kPa for 50 s...

The PMR-15 chemistry looks very straightforward and ideal for the application as a composite matrix resin. In addition, the starting monomers are readily available and cheap. The fact that the imidization reaction, which forms the prepolymer at moderately low temperatures, could be separated from the crosslinking reaction was thought to be the key to easy laminate processing and void free laminates. However, after more than twenty years of research and development, it is known that both reactions are very complex and dependent... 

The texturing sheet may also contain a plastic coating that transfers to the laminate surface during the laminating process to provide special surface properties. The caul plate itself may be smooth or textured and act directly as the release. Immediately beneath this release sheet, there may be a decorative layer or a ply that imparts special properties such as a metallic foil for electrical conductivity or a static dissipating layer. If the decorative layer is a printed... 

Multi-layer films can be produced, composed of different polymers. For each polymer a separate extruder is applied the extruders discharge into an accumulator, in which the separate streams are guided to their own position in the film. A laminated film can thus be made, in which one of the layers provides the strength, another one acts as a gas barrier, other layers promote adhesion and weldability, etc. This laminating process is applied with flat film extrusion as well as with film blowing. 

Integration of the active-matrix backplane and the electronic ink frontplane is a simple lamination process at a low temperature. After lamination the final stage of display processing is removal of the display from its rigid support. This support can then be re-used in the fabrication process. The cross-section of the complete stack of the Tollable active-matrix display is shown in Fig. 14.11. The complete display is only 100 pm thick, which is the same thickness as a normal piece of paper. 

In this review we will present an approach to modeling the stability, growth, and transport of voids during autoclave laminate processing. Before presenting the model formulation and some results, it will be helpful to briefly examine the process details and some of the evidence for voids. 

One of the most often used production procedures for fabricating a high-performance structural laminate is the Autoclave/Vacuum Degassing (AC/VD) laminating process. In this process, individual prepreg plies are laid up in a prescribed orientation to form a laminate. The laminate is laid against a smooth tool surface and covered with successive layers of glass bleeder fabric, Mylar or Teflon sheets, and finally a vacuum... 

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