Methods for Incombustibility Evaluation of Fast-Hardening Cement-bonded Particleboard

Three methods for incombustibility evaluation of fast-hardening cement-bonded particleboard, produced by carbon dioxide injection pressing process using thinned Taiwania particles blended with Portland cement, were conducted. Impacts of board foaming conditions were also investigated. Result showed that carbon dioxide injection pressing was able to form the board in five minutes with modulus of rupture of 53.24–69.95 kgf/cm2 for board made by 2.5, 3.0, 3.5 cement/particle ratio. Various methods led different incombustibility evaluation results. Proper cement/particle ratio was critical to strength and fire performance improvement. Thermogravitational analysis (TGA) and differential thermogravimetric (DTG) analysis demonstrated that cement boards degrading by three stages. Residues decreased with increasing heating temperature, increased with increasing cement content. Although satisfactory ignitability (tc) and fuming factor (ca) readings were recorded, the cement boards were only rated as incombustibility class 3 by method of test for incombustibility of interior finish material of buildings (CNS-6532) due to excessive heat generation (tdθ). Incombustibility class 2 was obtained by cone calorimeter method (CAN/ULC S 135). High correlation (R2＝0.9527) between heat generation (tdθ) readings (CNS-6532) and peak heat release rates (CAN/ULC S 135) suggested feasibility for comparison between two evaluation methods.

本研究针对以硅酸盐水泥（Portland cement）拌合间伐台湾杉（Taiwania）刨花、采用二氧化碳注入压制成型工艺（carbon dioxide injection pressing process）制备的快硬水泥刨花板（fast-hardening cement-bonded particleboard），开展了三种不燃性评价方法的测试，并探究了板材发泡工艺条件的影响。结果表明，当水泥/刨花比（cement/particle ratio）为2.5、3.0、3.5时，采用该工艺可在5分钟内完成板材成型，其静曲强度（modulus of rupture）可达53.24–69.95 kgf/cm²。不同评价方法得到的不燃性测试结果存在差异，合适的水泥/刨花比对板材强度与防火性能的提升至关重要。热重分析（Thermogravimetric Analysis, TGA）与微分热重分析（Differential Thermogravimetric, DTG）结果显示，该水泥刨花板的热降解过程分为三个阶段；其残留固体质量随加热温度升高而降低，随水泥掺量增加而升高。尽管测试得到了合格的可点燃性（ignitability, tc）与发烟因子（fuming factor, ca）数值，但依据《建筑内部装修材料不燃性试验方法》（CNS-6532）的测试标准，由于产热量（heat generation, tdθ）过高，该水泥刨花板仅被评为不燃等级3级。采用锥形量热计法（cone calorimeter method, CAN/ULC S 135）进行测试时，该板材被评为不燃等级2级。产热量（tdθ，对应CNS-6532标准）与峰值热释放速率（peak heat release rates）之间的决定系数R²=0.9527，表明两种评价方法具备较好的可比性。