Consolidation systems

Autoclave processing is a process in which individual prepreg plies are laid up in a prescribed orientation to form a laminate (Fig. 5.9). The process involves consolidation of the laminate, which generally results in a three-dimensional flow field. Similar to the IP process the fiber bed is not stationary in the AP process hence, its movement has to be specifically considered when the appropriate conservation equation for this process are developed. If it is assumed that the resin has a relatively constant density (i.e., the excess resin is squeezed out before the gel point is reached) then the appropriate conservation of mass equation for this consolidating system is Equation 5.12. 

Simple and Integrated Consolidation Systems for Degraded Wood... 

The effectiveness of both simple and integrated consolidation systems depends on successful cis penetration of the disintegrated fabric. The methods of simple consolidation are similar to those of integrated consolidation at this phase. Similar materials are often used to make the initial bond with the artifact. 

Because the function of consolidation is stabilization, the quantification and qualification of dysfunction properties are important criteria in developing a consolidation system. The MEC system should only compensate for reduced or lost properties enough to withstand ambient load. Stabilization does not mean restoring an artifact to its original resistance. Excessive restoration can be harmful, particularly when the restoration is in contact with untreated degraded surfaces. 

Consolidants must achieve cis penetration and provide a functional interface and a strength-enhancing matrix. Depending on the consolidation system, materials may either be introduced into the artifact or function externally. Achievement of MEC is further refined if the conservator is able to provide most consolidation external to the artifact, as less material becomes involved with the intrinsic structure. 

Integrated Consolidation Systems. An integrated consolidation system can be defined as any consolidation system that uses two or more materials to achieve stabilization. Although multiple materials may be introduced into the artifact, many advantages are realized in systems where the consolidant system is transferred to an external system. Three components make up the system initial fabric engagement, interfacing or transition, and strength matrix. 

The artifact was evaluated with particular concern for the transport to Australia and for a planned tour across Australia. Because of the radical difference between the anticipated transport load and exhibition load, the primary objective was to design a consolidation system that would be almost entirely reversible, yet replaceable when the artifact was to be moved. 

Potential Load. The artifact will be mounted in a permanent exhibition room in a diagonal position that reflects its original orientation. The room will have moderate environmental controls. The artifact will be lagged to a secure metal stanchion. Interactive energy will most likely consist of static and hygroscopic load the primary concern is material collapse or fatigue and the interface between the consolidation system and intrinsic fabric. 

According to Grattan (9), the most common polymers used in solvent-resin consolidant systems are acrylics, poly(vinyl acetates), poly(vinyl butyrals), and soluble nylon. Of these, soluble nylon has since been shown to be unsuitable because it inevitably cross-links and embrittles within as little time as a few weeks (iO). The others are known to have excellent longterm stability (9). Most likely the stability of polymers placed inside the wood may be even better, because they would be protected from light-catalyzed degradation reactions. Possible wood-polymer interactions, however, are unknown at this time. 

Traditional Methods. Traditional approaches to strength and integrity restoration center around consolidation systems. These consist of natural or synthetic resins that are impregnated into the wood. The natural resins are usually waxes or oils. Synthetic resins are either thermosetting (based on epoxy s, polystyrene, or a poly methyl methacrylate) or thermoplastic (such as poly(vinyl acetate)s, poly(vinyl butyral)s, or acrylics). In general, all of these consolidation systems do not penetrate the cell wall because they are not polar enough or because their molecular size is too large. 

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