Electron Beam Cured Resins for Wood Composites

Adoption of rapid, low temperature electron beam curable resin systems provide a great potential for energy saving to the wood composites industry. Other considerable advantages benefit from the radiation progression including: cost saving, reduction curing time, increased throughout capacity, minimal volatile emissions, increased the design flexibility.

The research was mainly focused on radiation dose optimization, resin structure-property relationships investigation, and resin-wood bonds evaluation. Resin chemical, physical, and mechanical properties were explored in detail by means of various testing methods. The formulating studies were concentrated on the radiation curable monomers (polyfunctional and monofunctional) and their effects to the network performance. Mechanical evaluation of resin-wood bonds was carried out, and particular attention was paid to bondline investigation.

The research found that the radiation dose for a complete curing was in the range of 20 kGy to 40 kGy for most acrylate or methacrylate based resins. The resin formulating studies revealed that polyfunctional monomers increased brittleness of the resin matrix, whereas monofunctional monomers d improved energy dissipation in the polymer network. Investigation of the correlation of resin properties and bond performance indicated that energy dissipation of resin is an important factor affecting the mechanical performance of bonded joints. Thus the adhesive-wood bond strength can be manipulated by adjusting formulation. The study also showed no statistically significant correlations between wetting (indicated by contact angle and viscosity) and bond mechanical properties. However, results showed a strong relationship between resin viscosity and penetration into the wood substrate. This suggests that formulation variables can be used to control the breadth of the interphase, and ultimately composite properties.

Finally, the experiments suggest that external, uncontrolled factors created by the conditions of joint preparation may have complicated analysis and interpretation of the data. Specifically, long times between resin application and subsequent cure may have led to over-penetration or other bondline defects.