Production of High Yield Animal Hide Glue for Bonding High Moisture Resistant (HMR) Grade Plywood

The driving force of this research study was the recovery of unwanted animal by-products such as animal skin and hide trimmings and flesh from the slaughter houses, or the scrap of animal skin and hide remains from leather industry. The collected animal by-products was firstly pretreated and later converted into gelatin. The study investigated a new extraction process using a dispersed micro-bubble technique to increase the recovery of animal glue (gelatin) within shorter time and disperse mixing process by using high shear mixing that worked to wipe the hydrolyzed glue from the surface of the collagen-containing material by providing a gentle and uniform agitation of the vessel content during the extraction stages. It was extremely effective to improve the yield of the glue production during the extraction process. The second stage of the study evaluated the possibility of fortifying and blending this glue with melamine-based resins to improve its moisture resistance and shear strength, suitable for plywood industry. Two types of melamine crosslinker were used: (i) Melamine urea formaldehyde and (ii) Melamine formaldehyde. The highest total yield obtained using the new extraction technique was 89.3% using 4500 rpm disperse mixing speed in which 16.9% was collected at an extraction temperature of 75°C, 50% at 85°C, and 22.5% at 95°C. The total yield obtained from the conventional extraction method over the same period of time was 36.9% with 12.1% collected at the temperature of 75°C, 16.9% at 85°C, and 7.9% at 95°C. Comparing the percentage yield by the new extraction method and the of conventional method, there was an improvement of 58.6% in yield recovery and there was about 4-10% improvement in yield and the extraction time was reduced to about 50-72% when compared to the existing commercial procedures used in both the glue and gelatin manufacture. Both the gelling strength and the viscosity of the gelatins produced by both methods were within the same range. High shear strength and superior moisture resistant properties were obtained from plywood bonded with animal glue blended with melamine urea formaldehyde resin. The shear strength being 3.2 MPa for the dry treatment, 1.0MPa for the cold treatment, and 2.5 MPa for the hot treatment. The shear strength of plywood bonded with 100% animal glue were l.4MPa, 0.1MPa and 0.6MPa for dry, cold and hot treatments, respectively. The improved animal glue gave a better performance compared to the traditional melamine urea formaldehyde with shear of 2.7MPa (dry), 2.7MPa (cold), and 1.9MPa (hot) treatments, respectively.

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