碳化钨粉末注射成形一步热脱脂的脱脂动力学

Degreasing Kinetics of One-Step Thermal Debindingof Tungsten Carbide Powder for Feedstock Injection Molding

采用热重分析法测定了在氮气气氛中5℃/min、10℃/min、15℃/min和20℃/min不同升温速率下的石蜡、保形聚合物(PP与HDPE的混合物)、石蜡/保形聚合物和碳化钨(WC-10%Ni)粉末注射成形专用料的热解过程,采用Kissinger法和Flynn-Wall-OZAWA法对4种专用料的热分解动力学进行分析,并用Coats-Redfern研究反应级数。结果表明,用Kissinger法分析不能很好地反映混合物的复杂的热解过程,不能支持碳化钨粉末注射成形一步热脱脂的工艺制定。用Flynn-Wall-OZAWA法分析,石蜡的热分解活化能在59~72 k J/mol,保形聚合物的热分解活化能在143~252 k J/mol,石蜡/保形聚合物的热分解活化能在60~240 k J/mol和WC-10%Ni的专用料的热分解活化能在93~220 k J/mol。用CoatsRedfern法分析,石蜡与保形聚合物的热解可用一级反应来描述,而石蜡/保形聚合物与WC-10%Ni的专用料的热解则适用3个连续一级反应来描述。

In this paper,the decomposition process of paraffin waxes,conformal polymers（ mixtures of PP and HDPE）,paraffin/conformal polymerization（ PP/HDPE） and tungsten carbide（ WC-10% Ni） Ni powder injection molding feedstock was analyzed by thermogravimetric methodin nitrogen at four different heating rates（ 5 ℃/min,10℃/min,15 ℃/min and 20 ℃/min）. The thermal decomposition kinetics of these four materials was analyzed by Kissinger method and Flynn-Wall-OZAWA method,and the reaction order was studied by Coats-Redfernformulation. The results show that the Kissinger method does not reflect the complex pyrolysis process of the mixture welland can not support the one-step thermal debinding process of tungstencarbide powder for feedstock injection molding. Determined by Flynn-Wall-OZAWA method,the pyrolysis activation energy of paraffin wax,conformal polymer,paraffin/conformal polymer and tungsten carbide（ WC-10% Ni） nickel powder injection molding feedstock is respectively 59 ~ 72 k J/mol,143 ~ 252 k J/mol,60 ~ 240 k J/mol and 93 ~ 220 k J/mol respectively. The pyrolysis of paraffin and conformal polymers can be described by the first order reaction,while the mixture of paraffin/conformal polymer and WC-10% Ni is described by three successive first-order reactions.