| In recent years, due to frequent occurrences of fires in China, which is a serious threat to people’s life and property safety. Therefore the requirements of energy-saving, flame retardant construction materials have been gradually increased. The demand of flame retardant materials will further increase. Although phenolic foam has excellent thermal insulation performance and excellent flame retardant performance, its strength is low, which limits its application. Phenolic foam sandwich composite board is prepared by phenolic foam as core material, flame retardant MDF as a reinforcing material. This sort of flame retardant lightweight wall materials has broad application prospects. In this paper, a variety of chemical analysis, FT-IR, scanning electron microscopy and the cone calorimeter and other methods were used. Taking phenolic resin and phenolic foam as the research object, this thesis discussed the influence of the amount of catalyst on the properties of phenolic resin and foam. PF resin of high solid content was well prepared. In addition, the foaming process is optimized in this study. Meanwhile, phenolic foam sandwich composite board of one-step forming and secondary adhesive technology were investigated. Combustion properties of phenolic foam sandwich board was analyzed effectively. The specific research contents and results are as follows:(1)Effects of amount of catalyst on the properties of PF resin and foam was studied and analyzed. Solid content of five kinds of phenolic resins prepared in the research fall in the range of 74%~76%. With the increase of the amount of catalyst, the viscosity of PF resins increased and the content of free formaldehyde and free phenol decreased. Tensile strength of phenolic foam increased to some extend with the increase of viscosity. And the compressive strength and flexural strength were comparatively better with the resin synthetized from 4% catalyst, and the compressive strength and flexural strength was 0.15 MPa, 0.34 MPa, respectively. The LOI of foam prepared from different amount of catalyst were all about 39%. Cell size of PF foam made from the corresponding resins significantly decreased and more evenly distributed. Foam cell size distributed in the 100μm~140μm prepared from resins synthetized from catalysts amount of 6%, 8%.(2) The effect of foaming conditions on the foam(pre prepared from PF resin with high solid content) properties was studied, the optimum foaming conditions were as follows: resin viscosity is 3000~5000mPa.s, the foaming temperature 70℃, the chosen curing agent is complex acid(phosphoric acid: p-toluene sulfonic acid: concentrated sulfuric acid: water =2:1:6:5), the dosage of the curing agent was 15%. Foaming agent is petroleum ether(boiling point 60~90℃), foaming agent dosage is 6%~8%. Apparent density of phenolic foam prepared under these conditions is 58.29~61.17 kg.m-3, the bending strength was 0.22~0.34 MPa, compressive strength is 0.18~0.20 MPa.(3)One-step molding parameters of phenolic foam sandwich composite panel were obtained: hot pressing temperature is 70℃, hot pressing time is 40 min. 24 h thickness swelling rate of the composite panel was 10%(<15%, meet the requirements of the subject). Thus Phenolic foam pre prepared has a higher obturator rate. Changes in size is mainly caused by fibers’ expansion after water absorption.(4) Three kinds of adhesive were selected for cold pressing, white latex(MDI ratio of 5%), PF(the toluene sulfonic acid ratio of 6%), urea formaldehyde glue(phosphoric acid ratio was 0.5% and 2% ammonium chloride), sizing weight 200g/m2, pressure 0.02 MPa. After placed at room temperature for 24 h. The bonding strength of foam sandwich composite panel were investigated, and the foam was interrupted which meets requirement of the bonding strength. Phenolic foam sandwich panels were also prepared by hot pressing process. The optimum PF resin single sizing weight is 200g/m2, hot pressing temperature is 120 ℃, hot pressing time 6min. The optimum MUF single sizing weight is 180g/m2, hot pressing temperature is 125℃, hot pressing time 6min. Results of the bonding strength of sandwich panels are in line with the requirements.(5)The CONE test was applied to study the flame retardant performance of phenolic foam, FR-MDF and foam sandwich composite board prepared by three kinds of adhesives. Through the evaluation of the heat release rate(HRR), total heat release(THR),specific extinction area(SEA), effective heat of combustion(EHC), oxygen consumption(O2C), oxygen consumption(TOC) and total smoke release(TSR) and other indicators, the test results showed that during the combustion process, the ignition time of phenolic foam is the longest, heat release and the total smoke release is the minimum, Phenolic foam’s flame retardant performance was significantly higher than that of FR-MDF. Through the analysis and comparison on the combustion properties of FR-MDF and three kinds of phenolic foam sandwich composite panel prepared by three kinds of adhesive, results illustrated that four kinds of material test results illustrates the basically same parameter curve. Foam sandwich panel maintained the integrity of morphology after burning, high char yield, and comparatively excellent flame retardant properties. |
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