Heat Post-Treatment to Reduce Thickness Swelling of Particleboard from Fast-Growing Poplars

According to the high thickness swelling and low dimensional stability of Poplars particleboard, this paper studied the effect of heat post-treatment on the board properties. The results indicated that the post-treatment could be a very effective way to produce dimensinaly stable fast-growing poplars particleboard. The thickness swelling of the board decreased with increasing the time and temperatures of post-heat treatment. So under190℃, being treated for 15 min., the total thickness swelling (TS1) of the board was 8.96%, reduced by 22.88%. The irreversible thickness swelling (TS2) was also reduced with the post-treatment of 190 ℃ or 220℃; The reversible thickness swelling (TS3) was not signifcantly changed when the time of treatment increased up to 25 min. under 190℃.

Study on the Effect of Two-Step Saturated Steam Heat Treatment Process on the Properties of Reconstituted Bamboo

With the aim of utilizing reconstituted bamboo as a carbon cycle oriented material,the improvement of physical and mechanical properties has been actively studied to solve using problems The saturated steam heat treatment process has been widely used in worldwide.With the development and exploration of this technology,two step satu-rated steam heat treatment process appears in some practical production,that is,affer a period of saturated steam heat treatment at a lower temperature,the bamboo bundles are taken out and seasoned for a period of time,and then put back into the heat tank again,and heated at a higher temperature for another period of time.During the two-step saturated steam heat treatment,the physical and mechanical properties of bamboo changed.However,the mechanism of two step saturated steam heat treatment has not been thoroughly discussed.For purpose that this paper all discuss and find out the mechanism of two step saturated steam heat treatment on the change of physical and mechanical properties of reconstituted bamboo.In this work,the one and two step saturated steam heat treat-ments were carried out according to the actual production parameters,and the physical and mechanical properties of the reconstituted bamboo board made of treated bamboo bundles were analyzed,including the color change,the thickness swelling(TS),modulus of elasticity(MOE),modulus of rupture(MOR)and shear strength.The results indicate that two-step saturated steam heat treatment is better than one step.Based on the detailed study of the chemical composition,crytalinity and micro morphologial characteristics of the heated bamboo bundles,it is further revealed that during two-step saturated steam heat treatment,oxygen air is added to the reaction system between the two heat treatment processes to further catalyze the oxidation of hemicellulose and enhance the crystal-linity of cellulose,so as to improve the properties of the final products.Our work has optimized the saturated steam heat treatment process which is widely used in industry,pointing out a new idea in the experimental and theoretical basis for the development of recombinant bamboo manufacturing industry.

Dimensional Stability Properties of Medium Density Fibreboard (MDF) from Treated Oil Palm (Elaeis guineensis) Empty Fruit Bunches (EFB) Fibres

The aim of the study was to investigate the effect of pre-treatments by using sodium hydroxide (NaOH) and acetic acid on oil palm Empty Fruit Bunch (EFB) fibres for the production of Medium Density Fibreboard (MDF). The EFB fibres were treated with chemicals in the concentration range of 0.2%, 0.4%, 0.6% and 0.8% prior to refining. Single-homogenous layer MDF with 12 mm thickness and density of 720 kg/m3 was produced. Urea-Formaldehyde (UF) was applied at 10% loading (based on dry weight of dry fibres) as a binder. The physical properties (Water Absorption (WA) and Thickness Swelling (TS)) of the produced panels were tested according to European Standard, EN 622-5:2006. The results show that types of chemical used had greater effects than concentration on the dimensional stability of the MDF. EFB fibres treated with acetic acid produced MDF with better dimensional stability compared to the MDF NaOH treated fibres. High concentration of NaOH produced poor dimensional stability in the panels.

A METHOD TO IMPROVE DIMENSIONAL STABILITY OF PF PARTICLEBOARD

A method of alkaline pretreatment of particles was designed to produce three types of chips. The pretreatmentet of particles in 1% water solution of NaOH for 30 minutes offered a possibility of producing PF bonded particleboards with minimal irrecoverable swell and a reduction in thickness swelling. The method used in this work could be used to produce more stable PF particeboard.

Study on Water Resistance of Polydopamine Treatment Wood Flour/Polypropylene Composites

This paper aims to investigate the water absorption of wood flour/polypropylene composites and its effects on dimensional stability and crystallization properties. Wood-plastic composites (WPCs) makes using polydopamine modified wood flour (WF-D), virgin polypropylene, maleic anhydride-grafted polypropylene (MA) and antioxidant, by using hot-pressing moulding. Water absorption (WA), thickness swelling (TS) and failure of flexural properties of the composites have studied for a range of immersion times. It is found that the WA and TS have increased with WF content and immersion time. The water absorption and thickness swelling of WPCs are 0.85% and 0.99%, respectively, after 8 days immersion. With the prolonging of immersion time, the impact strength, flexural strength and flexural modulus of WPCs increase first and then decrease. The impact strength decreases from 3.32 kJ/m2 to 2.94 kJ/m2, the retention rate is 88.55%;the flexural strength and flexural modulus by 68.58 Mpa and 3.92 Gpa, respectively. WPCs crystallization and thermal properties decrease slightly. Microstructures of the composites are examined to understand the mechanisms for the wood-plastic interaction which affects the water absorption and thickness swelling. Our work demonstrates that using polydopamine treatment wood flour for preparing WPCs can be an efficient way to improve the water resistance of WPCs.

Effect of Ratio of Face to Core Particles on Mechanical and Physical Properties of Particleboard Manufactured from Ethiopian Highland Bamboo

The study was conducted to evaluate effect of ratio of face to core particles on mechanical and physical properties of oriented strand board produced from Ethiopian highland bamboo.Three-layered oriented particleboards were manufactured with 4 proportions of face to core particles at 750 kg/m^3 target density.Ten percent urea formaldehyde resin was used as a binder.Strength and dimensional stability performances of all boards were assessed based on ISO standards.The results showed that modulus of rupture...