Amino Resins
(a) Urea Formaldehyde (UF) Resins:
Urea formaldehyde resins are preferred for bonding plywood and other wood based panels mainly due to the easy availability of raw materials required for resins at lower costs, colourless glueline and fast setting at elevated temperatures. The studies on thermal softening of cured resins indicate that molecular motion resulting in free volume changes within the polymer contributes to instability of UF resins above 60ºC. In view of these UF resins bonded panel products will be suitable best for interior locations only.
(b) UF Resins Fortified With Melamine:
Urea-Melamine Formaldehyde (UMF) resin for bonding warm water Resistant (WWR) grade panels and UF resin fortified with melamine for bonding Moisture Resistant (MR) grade panels have been developed. Adhesive formulations to meet the relevant requirements with respect to type of extender and its percentage, percentage of fortifier to be incorporated, catalyst and its percentage and processing parameters have been optimized.
(c) Extenders For Uf Resin
Extensive study have been conducted to review the use of extenders for UF resin adhesive as several protein and starch based materials were in use. Under this studies extenders were categorized as excellent, moderate and poor to enable the industry to select the right type of extender to be used. Most of the plywood industries are already using the extenders and also mixture of extender in their products which are cost effective and have several advantages over there use of naked resin.
(d) Amino Resin With Low Formaldehyde Releasing Property
The conventional Urea formaldehyde resin when used for making panels releases excess formaldehyde to the atmosphere during the manufacture and use. Keeping this in view an Amino resin system for bonding plywood and other wood based panels with reduced free formaldehyde have been developed. In this study the proportion of Urea, formaldehyde, suitable scavengers/adsorbing agents and the process parameters for resin manufacture and resin properties have been standardised.
(e) Melamine Formaldehyde/Melamine Urea Formaldehyde Resin
Among the Amino resins, Melamine formaldehyde-Melamine Urea formaldehyde resins, possess better water resistance properties compared to Uf resins. Studies have been made to develop MF/MUF resin adhesives for the manufacture of flooring tiles from bamboo, Bamboo laminates and also for finger jointing of Saw mill waste timbers. The required percentage of hardener for cold setting at room temperature have been worked out. The process parameters for manufacture laminates/tiles like spread, Assembly time, hot press temperature, pressure, time have been optimized.
