The Hot Pressing of Dry-formed Wood-based Composites. Part III. Predicted Vapour Pressure and Temperature Variation with Time, Compared with Experimental Data for Laboratory Boards

Abstract

KeywordsWood-bascd compositcs Particlcboard Hot prcssing Modclling Tcmpcrature Vapour prcssurc Hcat and moisturc transfcr Sitka sprucc Ptcea sitchensis SummaryUsing a thcorctical modcl, thc Variation of tcmpcraturc and vapour prcssurc within a particlcboard mattrcss during thc hot prcssing Operation is prcdictcd. Changc in thcsc variables with timc at a givcn Position in thc mattrcss, or with position in cithcr a vcrtical or a horizontal plane at a givcn timc, can rcadily bc studicd.Thc cffcct of a numbcr of proccssing variables on tcmpcraturc and vapour prcssurc Variation is analyscd, with the prcdictions of thc modcl bcing comparcd with cxpcrimcntal data. Thc prcdictcd data agrce well in trcnd, if not in absolute magnitudc, with thosc obscrvcd cxpcrimcntalty.

Influence of Aluminum Oxide Nanoparticles on the Physical and Mechanical Properties of Wood Composites

“…Core Temperature Profile Figure 6a shows the effect of nanofiller loading on the heat transfer properties of MDF during the hot pressing process in the form of the core temperature profile. At the beginning of the press cycle, there was a rapid rise in the core temperature, which was due to a steep vapor pressure gradient (Bolton et al 1989) that developed during the period of 15 to 70 s. From 70 to 130 s, a constant temperature in the central plane was observed, which was due to a phase change occurring in the board. The vapor formed was observed to exit from the edges of the board due to the higher vapor pressure formed at the core.…”

Properties of particleboard produced from post-industrial UF- and PF-bonded plywood

“…An increased share of the recovered particles resulted in a less compact structure of the core layer, so that, steam easily penetrated the mat and heat transfer was accelerated. Numerous literature reports are coherent with that explanation Bolton et al 1989;Thoemen and Humphrey 2001). In addition, the recovered particles are partially densified material that exhibits higher heat conductivity (Kollmann 1955).…”

“…As a result a target mat core temperature was achieved in a shorter time. Taking into account the phenomenology reported by Graser (1962) and Bolton et al (1989), the maximum effect was observed in phase II (water evaporation) that lasted from 20 to 120 s. In consequence, the time necessary to heat a mat bearing 20% of the recovered particles to 60, 80 and 100 °C was shortened by 22, 16 and 8%, respectively. Under alike conditions, times of heating a mat containing 100% recovered particles were 29, 25 and 15% shorter than those for the reference.…”

Monitoramento Do Tempo De Prensagem E Do Comportamento Da Temperatura Através Da Espessura De Painéis LVL (Laminated Veneer Lumber)

“…De uma forma geral o perfil da elevação da temperatura observado no centro dos painéis e nas faces foi semelhante aos observados em outros compósitos de madeira, conforme descrito por Bolton et al (1989), Zombori (2001) e Calegari et al (2000.…”