Influences of Layered Structure on Physical and Mechanical Properties of Kenaf Core Particleboard

Kenaf (Hibiscus cannabinus), a fast-growing fiber crop, is a potential substitute for wood to make composition boards. This work investigated single- and three-layer kenaf core particleboards (KPBs) and kenaf core-cedar wood composite particleboard (KCPB) with polymeric methylene diphenyl diisocyanate (pMDI) and phenol formaldehyde (PF) resins. The physical and mechanical properties including bending modulus (MOE) and strength (MOR), internal bond (IB) strength, water absorption (WA), thickness swelling (TS), and linear expansion (LE) were tested following the ASTM D 1037 and ANSI A 208.1 standards. It was shown that kenaf core can be made into standard-satisfying particleboards with comparable performances to cedar-based wood panels. Three processing factors, i.e., board density, resin content, and layered construction, had significant influences on panel properties. KPBs denser than 0.70 g/cm(3) and with 6% PF met with the standard specifications. The WA, TS, and LE of single-layer KPBs decreased with increased density. Three-layer KPBs showed improved MOE, MOR, and IB strengths, and effectively avoided the unbalanced structure shown in the single-layer KPBs in thickness direction. The three-layer KPBs with a 50: 50 surface-to-core ratio had the best comprehensive performances. The results can be helpful for the application of kenaf residues in the wood composites industry.