Improvements in the production of wood fiber insulation boards using hot-air/hot-steam process

Abstract

In times of climate change and shortage of non-renewable resources, building insulation becomes an important issue to save energy and resources. One option could be to use wood fiber insulation boards as a substitute for fossil fuel-based insulation materials. This document presents the manufacturing of wood fiber insulation boards by using the dry process and an innovative curing method combining hot-air and hot-steam. The aim was to reveal the positive physical effects of using hot air and steam in combination for curing of pressure-resistant insulation wood fiber boards. In addition to familiar bonding agents such as polymeric methylene diphenyl diisocyanate (pMDI), urea–formaldehyde resin (UF) and an enzymatic binder system should be partially used here for substitution. At this stage, fibers should be enzymatically pre-treated with laccase in conjunction with a suitable mediator, forming a Laccase-Mediator-System (LMS). A further goal of the paper is to investigate in which quantities LMSs can be added to the binder mixture to achieve results comparable to those of conventionally bonded fiber boards. For this purpose fiber insulating boards with a bulk density of 180 kg/m3 and a thickness of 40 mm were produced and tested in regards to physical technical properties such as internal bond strength (IB), compressive strength (CS) and water absorption (WA) over 24 h. The objective of this study was to understand whether an optimal relationship of hot-air and hot-steam exists in relation to physical technical properties. Present work has shown that the steam treatment offered enhancing effects in regards to both internal bond and water uptake after 24 h. However, the best results were achieved by using hot-air/hot-steam in combination for curing. Here the condensation heat was exploited to obtain higher temperatures for a better lignin repolymerization. In conclusion, the results show that a partial substitution of pMDI by LMS is generally possible and curing via hot-air/hot-steam is advisable; however, the maximum evaporation time should be restricted to 10 s.