Fabrication and characterization of HDPE resins as adhesives in plywood

Demand has been growing for plywood utilizing novel formaldehyde-free wood adhesives which are more durable and require environmental protection and sustainable development during the service life. In this study, a series of HDPE film as novel adhesives in plywood due to many advantages are fabricated using hot-press process followed by cold-press process. The effects of moisture content, HDPE dosage, hot-press temperature and pressure at different levels on physical–mechanical properties were evaluated by tensile shear strength, compression ratio, water absorption and thickness swelling. The results indicated that HDPE film can independently be used as adhesive in plywood, meeting the requirement for type II grade plywood of GB/T 9846.3 (Plywood-part 3: General specification for plywood for general use. Chinese National Committee for standardization, 2004) and opening up a new way for formaldehyde-free adhesives in plywood used as interior grade. Moreover, analysis of variance showed that the most important effect factor on tensile shear strength and water absorption is HDPE layer; on compression ratio and thickness swelling it is moisture content of veneer. To study the optimal hot-press condition, optimization of preparation process for plywood was carried out by response surface methodology analysis (RSMA), and then analysis by Design-Expert software. The simulation results of tensile shear strength were validated by experimental findings, indicating that RSMA can be used as an effective method to predict optimal fabrication condition.