The Influence of Polymers Impregnation on Bending Behaviour of Phyllostachys pubescens (Mosso) Bamboo

As the consumption of natural resources in today's industrialized society is increasing and the supply of these resources tends to deplete, the search for alternative and environmentally friendly raw materials becomes mandatory. Bamboo is a very abundant resource and presents short growth, carbon sequestration ability, easy processing and good mechanical properties. However, bamboo is hygroscopic material and presents functional gradation of properties along the culm wall thickness. Cracks may occur in bamboo’s wall as a consequence of a radial moisture gradient, that generate stress perpendicularly to natural fiber alignment, and this occurrence may compromise the durability and structural performance of the material. Aiming to minimize these shortcomings and to enhance physical properties, different polymers were used to impregnate samples of Phyllostachys pubescens bamboo through immersion: styrene butadiene rubber (SBR), carboxylated styrene butadiene rubber (XSBR) and polyvinyl alcohol (PVOH). Three temperatures of impregnation were investigated (23, 60 and 100 ºC, and the most effective in relation to polymer penetration and retention was identified. Results of water absorption tests showed that PVOH resulted in better physical behaviour and smaller water absorption values, compared with non impregnated samples. Three-points bending test was carried out employing samples with 20 × 2 × 0.5 cm. The samples were extracted from the internodes of the middle portion of a 3 years old culms. The obtained parameters (bending strength, stiffness and toughness) were compared among the 4 conditions (plain, SBR, XSBR, PVOH) in order to understand how the impregnation process affected the mechanical performance under bending loads.