Fungus and fire resistance of insulation mats based on water glass bonded non-textile flax fibres

Excerpt

Field retted flax crop were processed to fine non-textile fibres as specified elsewhere (Grohe 2003) and the material employed for the manufacturing of insulation mats. Water glass was applied as an adhesive and a solution prepared by adding 50 vol.% water to the received viscous water glass (Betol 39T1, 36 wt.% solids in water, Woellner Silikat GmbH, Ludwigshafen, Germany;) leading to 18 wt.% solids in water (pH~11). An aqueous borate solution of 14 wt.% boric acid and 10 wt.% sodium hydroxide (33 wt.% NaOH solution) was mixed, giving 24 wt.% solids in water (ph~13). Thus, the mixture contains a fraction of ~21.6 wt.% of the flame retardant and fungicide Borax (Na₂B₄O₇⋅10 H₂O). The B(OH)₃-solids and the NaOH-solution were received as technical grade by Zschimmer und Schwarz, Lahnstein, Germany. Insulation mats were fabricated via a pilot plant, as described by Grohe 2003. During the process flax fleeces were sprayed either with (A) water glass or with (B) water glass and subsequently with the boric compound. Some insulation mats were fabricated by primarily spraying them with (C) boron-solution followed by another cycle comprised the spraying of water glass and boric compound. Test-series were carried out (Bundesanstalt für Materialforschung und -prüfung, Berlin, Germany) to investigate the biological resistance of insulation mats fabricated via the production runs (A), (B) and (C) (see Table 1). Thereby, five samples (90×90×40–55 mm) of each production run were exposed to pure cultures of the wood destroying fungal species Aspergillus niger, Aspergillus terreus, Aureobasidium pullulans, Paecilornyces variotii, Penicillium funiculosum, Penicillium ochro-chloron, Scopulariopsis brevicaulis and Trichoderma viride and the degree of fungal attack verified, according to DIN IEC 68-2-10. To investigate the fire properties of insulation mats five samples of the series (B) were tested according to DIN 4102-1 (FIW—München, München, Germany). …