Resistance of Conifer Needle Polyolefin Composites (CNPCs) Against Biodecomposition Caused by Fungi

Abstract

This study describes the resistance of composites filled with conifer needles to biodecomposition processes caused by a single strain of Aspergillus niger as well as by a consortium of microorganisms present in the compost substrates (forest or spent mushroom composts). The impact of various types of conifer needles on the growth of A. niger was studied to determine whether the filler can show the fungistatic effect. The changes in chemical composition of the composites surfaces were examined using attenuated total reflectance Fourier transform infrared spectroscopy (FTIR/ATR). The results showed that the fungistatic effects of conifer needles polyolefin composites (CNPCs) were associated with type, content and fragmentation of fillers. The most effective were composites that contained 30 or 50 wt% of pine or spruce needles flour, since respectively the mycelial growth was inhibited by approximately 50%, or totally. Moreover, the 90 days experiment conducted in the forest compost showed that the addition of 50 wt% mercerized conifer needles and 10 wt% natural resin increased the resistance to biodecomposition for about 40% in comparison with composite containing unmodified needles. Even higher about 60% increase in resistance was observed comparing to sample with mercerized filler. In turn in the spent mushroom compost, these differences amounted respectively to 50 and 78%, what confirmed that the addition of natural sources of resin established a protective barrier against the impact of examined fungus.