Thermal modification dimensional stability

The Royal (or Royale) process was originally developed as a method for drying timber, in which the wood is heated in oil under vacuum. The temperatures used are low (60-90 °C) compared to other thermal oil treatments, and although sufficient to lead to some curing of the oil itself, there is no direct modification of the wood as a result of this process. The oil does not penetrate the cell wall. In this process, wet timber is placed in a treatment vessel and oil is then introduced, which is heated to the desired temperature, whilst a vacuum is applied. Water is removed from the timber and the vapour is transported away by the vacuum system. When the wood has reached the desired MC, the oil is removed from the treatment vessel. After this, a vacuum is applied to removed excess oil from the wood. Some dimensional stability is imparted to the timber due to the water repellency of the oil. This treatment is marketed by Osmose as the Royale process. 

The hydrophilic character of wood, intrinsically connected with the structure of its three main macromolecular components, has been a longstanding source of problems, mostly arising from its lack of dimensional stability in moist environments. An additional major drawback is its susceptibility to photolytic and biological degradation. The interest of both scientists and technologists in modifying wood in order to overcome these drawbacks has called upon specific treatments like chemical, thermal, enzymatic or purely physical modifications. This chapter examines recent contributions to these issues, based on approaches which only involve the chemical modification of wood, carried out in bulk or at its surface. The other treatments have been aptly covered in a recent book [1] and a thorough review [2]. 

It was found by Cho s research group [24] that the thermal expansion of neat poly(butylene succinate) dramatically reduced by reinforcing it with chopped silk fibers, which are animal-based natural fibers, without any surface treatment or modification, indicating much improved dimensional stability of silk/PBS biocomposites, as seen in Figure 4.19. The linear coefficients of thermal expansion (GTE) were 294 x 10 for neat PBS and 10 x 10 to 52 x 10 °G for silk/PBS biocomposites, depending on the fiber content incorporated. This result implied that such a reduction of the GTE may be further performed by enhancing the fiber-matrix adhesion through optional surface modification of raw silk fibers. 

A well-accepted definition of nanocomposite material is that one of the phases has dimensions in the order of nanometers [51]. Roy et al. [52] present in their paper on alternative perspectives on nanocomposites a summary of features of particle properties when particle size decreases beyond a critical size. As dimensions reach nanoranges, interactions improve dramatically at the interfaces of phases, as do the effect of surface area/volume on the structure-property relationship of the material [53]. There is definite increase in the modulus of the material reinforced with composites, higher dimensional stability to thermal treatment, as well as enhanced barrier, membrane (conductive properties) and flame resistance. Thus, as Paul and Robeson [54] rightly put it, the synergistic advantage of nanoscale dimensions ( nano effect ) relative to larger-scale modifications is an important consideration ... 

No modification is observed in the dimensionality compared with that of the parent gold cyanide complex, but an increment in the thermal stability is described in the final compound. In the structure of [Cu(tmeda)][Au(CN)2]2 (tmeda = N,N,N, N -tetramethylenediamine) aurophilic interactions connect ID chains which contain copper(II)-bridging and pendant [Au(CN)2] units. In this case the aurophilic interactions increase the structural dimensionality from one to three. The compound is synthesized by reaction of Cu(C104)2.6H20, tmeda (tetramethylethylenediamine) and K[Au(CN)2]. The structure of Au2Cu(CN)4(tacn)] (tarn = 1,4,7- triazacyclono-nane) contains two different sort of chains. One of them contains gold atoms in an ABCDABCD- pattern (Figure 2.16a), and the other is built from two kinds of... 

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