Development of Melamine Modified Urea Formaldehyde Resins Based on Strong Acidic Ph Catalyzed Urea Formaldehyde Polymer.
Forest Products Journal 2009, May, 59, 5
Forest Products Journal
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Exterior-grade melamine-urea-formaldehyde (MUF) resin adhesives are considered too costly to replace urea-formaldehyde (UF) resins for interior applications. Melamine-modified UF resins with reduced melamine content levels have been developed to improve durability and moisture resistance properties. These low-melamine content UF resins have been relatively popular in Europe (Dunky 1995) and in the Asia-Pacific region (Maylor 1995, Parker and Crew 1999) for many years. More recently, melamine-modified UF resins were also shown to yield particleboards with significantly lower formaldehyde emissions than the control UF resins (Graves 1993, Rammon 1997). It is generally recognized that formulation of low formaldehyde emission UF resins are accomplished primarily by decreasing the formaldehyde/urea (F/U) ratio (i.e., down to 1.2 or even 1.1 ratio). But, it was shown that lower F/U ratio, while yielding substantially lower formaldehyde emission, also resulted in longer resin cure time and lower internal bond (IB) strength (Hse et al. 1994). A method most commonly used to cope with this formaldehyde problem is to react formaldehyde with urea initially at a much higher F/U ratio and strong acidic condition to form the backbone of the resin system; then, after attaining a desired degree of condensation, additional urea is added to adjust the F/U ratio to meet the desired low F/U ratio in final resin products. Similar methods of reacting urea and formaldehyde at strong acidic pH and adjusting F/U ratio to attain the desired low formaldehyde emission were applied in formulating MUF resin adhesives.
- 2,99 €
- Category: Business & Personal Finance
- Published: 01 May 2009
- Publisher: Forest Products Society
- Print Length: 21 Pages
- Language: English