Surface Chemical Modification for Bonding

There have been a number of studies concerned with the use of chemical modification for the purpose of providing a means of bonding between wood surfaces. Conventionally, 

Mahlberg etal. (2001) studied the effect of acetylation of wood fibres (20 % WPG) upon the mechanical properties of wood fibre PP fibre composites, with and without the addition of a novalak PF. Acetylation resulted in significant improvements in MOR, MOE and IBS in a composite containing 20 % by weight of PP fibre. With a combination of PF and PP (both 10 % by weight) and acetylated wood fibre, MOR was unchanged, MOE decreased and only IBS showed a significant improvement. Acetylation also contributed to a better dispersion of the wood fibres in the PP matrix. 

2 Reaction of Wood Surfaces with Coupling Agents 

In a study by Felix and Gatenholm (1991), cellulose fibres were heated in a toluene solution of MAPP for 5 minutes at 100 °C. The MAPP was used as received, but also heated at 180 °C for 5 minutes in order to convert any hydrolysed maleic acid groups back to the anhydride form. Treated fibres exhibited contact angles in water of the order 

Fibres reacted with pre-heated MAPP always exhibited larger contact angles compared with fibres reacted with as-received MAPP. FTIR studies showed that there was a higher level of ester linkages when the fibres were reacted with the pre-heated MAPP. Wood polymer composites were made by shear mixing in a twin screw extmder, and the mechanical properties of these composites were found to be superior when pre-heated MAPP was used as the coupling agent. 

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