Performance Effectiveness On Addition Of SOLID-UF-RESIN TO LIQUID-UF-RESIN During Plywood Manufacturing

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Urea–formaldehyde (UF) resins are one of the most widely used wood adhesives with wide applications in manufacturing of wood-based composite panels such as plywood, particle board, and medium-density fiberboard. Some of the advantages of UF resins over other adhesives are easy handling, low cost, and good performance in panel products. UF resin is most important type of adhesive in the wood industry since last 60 years especially for the production of wood based panels. More convenient spray dry UF powder is in the market for the last two decades. Small and medium private based wood panel industry prefers to use powder resin since they are more convenient for small capacity production. During last two decades, certain efforts have been undertaken for its improvement like reduction of gel time, free formaldehyde emission, adhesive bond fortifying,

prolongation of storage life and more= convenient transport and application. Liquid UF resin concentration up to 50 to 55% solid content were prepared within wood industry complex is having storage life of 40 days maximum were more convenient but at the same time spread. UF powder resin can be used by re-dissolved and re-dispersed in water at different concentration just before application. So efforts have been made to make a glue system for wood based panel industry by combination of powder resin with liquid UF resin.

The purpose of this study is to investigate the effect of solid powder urea formaldehyde resin on the quality of the plywood when manufactured by mixing with liquid urea formaldehyde resin. The finding obtained would benefit the manufacture of urea formaldehyde adhesive bonded composite panels. The study is focused on new solution for production of high quality wood based panels by using technique of mixing of powder resin with liquid urea-formaldehyde resin to make better adhesive system. In order to improve the adhesive and bonding properties solid powder urea formaldehyde resin was mixed with liquid Urea formaldehyde resin, 12mm plywood was manufactured and bond quality was studied as per IS:848:2006. Conventional hardener – so called latent catalyst namely ammonium chloride was used to react with existing free formaldehyde of the resin forming a strong acid that promotes resin cure.

From the study, data shows that glue shear strength for both dry state, weight state and in mycological state, tensile strength and static bending strength values shows satisfactory results. There is a significant change in results of MoR and MoE of plywood samples manufactured by using powder resin mixed with liquid resin. It was also found that after using 10% concentration of solid UF resin, the pre press tackiness was improved drastically which helps to improve the quality of plywood.

The study developed a new solution or technique that can give a solution to manufacture plywood by using pre press technique and manufacture of wood based composites having more mechanical and bonding strength by using urea formaldehyde resin. Adhesive mix for plywood manufacture using UF solid powder resin with liquid resin shows homogeneous mixture after mixing of 30 minutes in glue spreader. The powder resin doesn’t shows any chemical reactions with liquid UF and MUF resin even if after mixing ith hardener and buffer Powder resin shows satisfactory results for adhesive mix.

From Viscosity study data shows that viscosity of adhesive mix measured in terms of flow time in B6 (IS 3944,1982) shows satisfactory result at extension level 5 to 10 % on the basis of liquid uf resin for smooth operation of Glue Spreader. From the data, it has been observe that the viscosity of adhesive mix increases with increasing extension level. Solid content of adhesive mix increase as significantly as the concentration of the powder resin increases in the adhesive mix with satisfactory PH and pot life.

Bonding quality was tested according to IS 848:2006 for UF solid powder resin after mixing with liquid UF resin. The results are summarized for UF solid resin at 10% (w/w) of liquid resin used to test for MR Grade plywood and results showed that UF powder resin shows excellent results in cyclic test. Glue shear strength value shows more in comparison to MR and UF control. From the analyze data shows that during study glue shear strength for Dry, Wet and Mycological, Tensile strength and Static bending strength values shows satisfactory results, there is a significant change in results of MOR and MOE of plywood samples manufactured by using powder resin mixed with liquid resin.

In plywood industries the former process is known as cold pressing and the later is known as hot pressing .Both process leads to curing of resin. After mixing of solid powder UF resin in liquid UF and MUF resin analyze data shows satisfactory press tackiness to achieve the desired cold press bonding as applicable in plywood manufacturing.

 The results and analysis of studies leads to the conclusion that the UF powder resin having solid content 100% doesn’t show any chemical reaction with Liquid resin even after mixing with hardener and buffer rather than forming creamy and is lump-free during mixing. The satisfactory rheological properties of the adhesive and physicomechanical properties of the plywood made with mixing resin technology were achieved. Satisfactory pre-press results have been achieved at higher concentration of powder resin mix. The chances of pre-cure of dry out were reduced because veneers are held in close contact with each other. The adhesive wets the veneer surface since the layers of veneers have an opportunity to come into intimate contact with each other for greater period of time. Hence the quality of the plywood improved by overcoming warping, pre-curing etc. Plywood manufactured by adding 10% (w/w) solid powder UF resin with liquid confirms to MR Grade in all the cases when tested as per IS 848 – 2006.


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