No abstract

In this study, bamboo charcoal (BC) was used as a substitute filler for bamboo powder (BP) in a lignocellulose-plastic composite made from polylactic acid (PLA), with aluminum hypophosphite (AHP) added as a fire retardant. A set of BC/PLA/AHP composites were successfully prepared and tested for flame-retardancy properties. Objectives were to (a) assess compatibility and dispersibility of BC and AHP fillers in PLA matrix, and (b) improve flame-retardant properties of PLA composite. BC reduced flexural properties while co-addition of AHP enhanced bonding between PLA and BC, improving strength and ductility properties. Adding AHP drastically reduced the heat release rate and total heat release of the composites by 72.2% compared with pure PLA. The formation of carbonized surface layers in the BC/PLA/AHP composites effectively improved the fire performance index (FPI) and reduced the fire growth index (FGI). Flame-retardant performance was significantly improved with limiting oxygen index (LOI) of BC/PLA/AHP composite increased to 31 vol%, providing a V-0 rating in UL-94 vertical flame test. Adding AHP promoted earlier initial thermal degradation of the surface of BC/PLA/AHP composites with a carbon residue rate up to 40.3%, providing a protective layer of char. Further raw material and char residue analysis are presented in Part II of this series.

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Five sets of three-layer OSB were made from aspen and/or Moso bamboo strands in the following three configurations: Aspen strands in the surface and core layers; Moso strands in the surface and core layers; and Moso strands in the surface and aspen strands in the core. Boards containing Moso strands in the surface layers had two sub groups: (1) all strands contain a node in the middle, and (2) all strands are node free (internode). All 30 boards were comprised of 50 % w/w surface furnish and 50 % core furnish, fabricated to 737 mm 9 737 mm 9 11.1 mm. Standard mechanical (thickness, density, surface and core density) and strength properties [internal bond (IB), flexure, lateral nail withdrawal resistance (LNR)], and water resistance [2 and 24 h thickness swell (TS) and water absorption (WA)] were assessed. Complete replacement of the aspen in the surface layers with internode Moso strands resulted in over 45 % greater MOR. Panels made with Moso surface layers met CSA O437.0 (2011) minimum requirements TS/WA without the need for wax addition, possibly because no densification of the surface material was observed. Due to high variance in LNR, effects of board type and core composition were not statistically significant, but LNR of boards exceeded CSA O437.0 minimum requirements. Moso bamboo surface OSB were low in MOE which is consistent with unadulterated tissue being high in bending strength and fracture toughness but low in specific stiffness. The presence of nodes in the bamboo strands significantly reduced the strength properties of OSB, a problem which could be mitigated by minimising the incidence of nodes in the strands, particularly those used in the surface layers.

The flexural properties in the longitudinal direction for natural and thermo-hydromechanically densified Moso bamboo (Phyllostachys pubescens Mazel) culm wall material are measured. The modulus of elasticity (MOE) and modulus of rupture (MOR) increase with densification, but at the same density, the natural material is stiffer and stronger than the densified material. This observation is primarily attributed to bamboo's heterogeneous structure and the role of the parenchyma in densification. The MOE and MOR of both the natural and densified bamboo appear linearly related to density. Simple models are developed to predict the flexural properties of natural bamboo. The structure of the densified bamboo is modelled, assuming no densification of bamboo fibers, and the flexural properties of densified bamboo are then predicted using this structure and the same cell wall properties of that of the natural material modelling. The results are then compared with those for two analogous structural bamboo products: Moso bamboo glulam and scrimber.