Resistência à umidade e emissão de formaldeído em painéis de partículas de média densidade fabricados com diferentes resinas melamina ureia formaldeído

Abstract

The search for wood base panels more durable and sustainable over time give impulse to medium density panel producers to develop special products much more efficient in relation to humidity behavior. Cost impact is higher due to the utilization of special adhesive class, like melamine urea formaldehyde (MUF) increase in raw material use and productivity reduction. This research focused on investigating influence of variables like final molar ratio and percentage of melamine on melamine urea formaldehyde (MUF) formulations used for laboratory fabrication of particleboard and analyzing panel properties behavior like internal bond formaldehyde emission and resistance to humidity cycles. The melamine urea formaldehyde (MUF) utilized in this study were processed in laboratory with molar ratios 1.05 1.22 1.30 and melamine percentages of 5% and 15%. Adhesives formulation (MUF) were evaluated for reactivity by DSC, molecular weights through gel permeation cromatography and spectroscopic tests (FTIR). These tests showed typical behavior of amino resins and on reactivity tests were observed that higher molar ratios gives higher reactivity and increase on melamine percentage will need longer press times. Twenty particleboards panels were produced utilizing Pinewood using 10% MUF, paraffin emulsion and ammonium sulfate as hardener. Samples of these panels were submitted to classical tests, accelerated aging test (V313) and formaldehyde emission (perforator). Panels with higher molar ratios and higher melamine percentages gave higher internal bond values, lower swelling and more resistance on humidity cycling (V313). For formaldehyde emission panels met E1 and E2 specifications however for higher molar ratios higher formaldehyde emissions values obtained and were not influenced by melamine percentages.