Surface modification of napier stem strand used in non-wood low density particleboard

Napier stem (Pennisetum Purpureum) is a non-wood lignocellulosic biomass and was identified as a potential raw material for the production of particleboard because of its strong rigidity and wide availability. However, the composite polymer nature in Napier constituent and fibre morphology, particularly the lignin portion, presents resistance and recalcitrance to biological and chemical degradation during enzymatic hydrolysis, therefore fibre refining by pretreatment is a main process that significantly influences the overall fibre properties in Napier. Thus, Napier structure requires initial breakdown of the lignocellulosic matrix. In this study, Napier grass in the form of Napier stem strand (NpSS) was used to produce the low density standard particleboard for internal general purpose use. The objective of this study is to establish the operating conditions that bring the optimum properties of the NpSS particleboard with minimal variance. At the first stage of the study, the strands of Napier stem were alkali-treated using sodium hydroxide (NaOH) solutions to reduce the lignin content in native NpSS. The pretreatments were conducted using NaOH solutions of different concentrations of 5.50/o(w/v), 8.00/o(w/v), and 10.50/o(w/v) and were incubated at controlled temperature of 70°C for five hours. Aspect ratio analysis (diameter examination), chemical analysis, Thermogravimetric Analysis (TGA), Fourier Transform Infrared Analysis (mR), and Scanning Electron Microscope (SEM) were used to examine the physical properties of the treated and the untreated NpSS. From the single-strand particle characterisation results and through a characterisation of Napier strand, the 10.5 wt. % alkali-treated NpSS exhibited the lowest lignin content. 93.78% of lignin was removed and 80.59% of cellulose and 63.57% of solid were recovered as compared to the control sample (untreated NpSS). Next, the second stage of the study was the board production using urea formaldehyde (UF) resin. For screening purpose, Taguchi approach was employed and the type of NpSS factor (categoric form), and the two numerical factors that consist of percentage of resin content and the hot press temperature were identified as the independent variables. Subsequently, Response Surface Methodology (RSM) of Central Composite Design (CCD) was employed using Design Expert (DE10) software to analyse the relationship between the three variables and their influence on the internal bond (IB) strength, static bending (MOE and MOR) strength, screw withdrawal (SW) strength, thickness swelling (TS) and water absorption (WA) properties were studied. The panels were produced with target thickness of 12 mm and density of 640 kg/m3. A variety of mechanical and physical tests were performed in accordance to British Standard (EN310-317:1993, EN 320:2011). It was found that the formations of NpSS boards were best fit by a quadratic regression model for MOR and WA. Reduced cubic models were in compatible with IB, MOE, SW and TS