bioresources. com
PEER-REVIEWED ARTICLE
Chemical modification of the fibre not only can improve the adhesion between the surface of the fibre and the polymer, but the specific fibre strength can increase, the water absorption by the composite can be decreased, and the mechanical properties of the entire composite material can also be improved (Li HWDO 2007). However, the disadvantage of traditional methods of chemical surface modification is the production of hazardous substances that may endanger the environment and human health. From this perspective, surface treatment using plasma is a more benign method toward the environment. Plasma is an ionized gas containing ions, electrons, neutral and excited molecules, and photons (Baltazar-y-Jimenez HWDO 2008). Two methods of surface treatment using plasma can be distinguished at low pressure and at atmospheric pressure. Plasma surface treatment at atmospheric pressure is less demanding for instrumentation and has been a progressive method in recent years (Cheng HWDO 2010). The interaction of plasma with a solid surface results in varying changes in surface properties depending on the type of gas used. Surface energy may be increased or decreased, cross-linking of cellulose in the surface layer may occur, or the forming of free reactive groups may take place (Podgorski HWDO 2000; Baltazar-y-Jimenez HWDO 2008). Cold plasma does not cause any changes deeper in the material, but rather only affects the surface layers (Mahlberg HWDO 1999). The most important parameters when treating a surface with plasma are the plasma surface contact time, the distance between nozzle and surface, and the size of the current (Baltazar-y-Jimenez HWDO 2008). Primarily the following gases are used to modify the surface of lignocellulosic materials to better bond with the polymer: oxygen (Mahlberg HWDO 1999), air (Baltazar-y-Jimenez HWDO 2008), and argon (Zanini HWDO 2005). The aim of this research was to clarify the effect of a cold plasma surface treatment of crushed winter wheat stalk particles, prior to board manufacturing, on the physical and mechanical properties of thereof produced particleboards. Specifically, this is a determination of the impact of plasma treatment on the bending strength, tensile strength perpendicular to the plane of the board (internal bonding), vertical density profile, water uptake, and thickness swelling of boards manufactured from plasma-treatedwheat straw bonded with urea-formaldehyde adhesive.
EXPERIMENTAL Materials 6WUDZSDUWLFOHV
Commercially-sold chopped wheat straw particles were used to manufacture the boards (Mikó Stroh, Borota, Hungary). Using digital image analysis, the proportion of individual fractions was defined per 100 g of material sample using a particle analyzer CAMSIZER (Retsch Technology GmbH, Haan, Germany). The sample was poured into the feed chute, allowing the material to enter the measurement field through the feed guide, which prevented unwanted turbulence of the particles and gave the particles the correct orientation. The maximum range was set to 50 mm. The shortest (width) and the longest particle distance (length), measured by the Feret diameter during the projection, was assessed.
5066
Hýsek et al . (2018). “Cold plasma & straw board,” B io R esources 13(3), 5065-5079.
Made with FlippingBook Ebook Creator