ABSTRACT

In the study, the bonding strength of phenol-formaldehyde (PF) adhesive on plywood under different hot press temperature and time was evaluated. A mechanical mathematical model was established to analyze the curing process of PF adhesive, in which the parameters of model could be used to predict the bonding strength and change rate of plywood. The thermal curing degree of the adhesive was determined by differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) as well as Nuclear magnetic resonance (NMR) were used to analyze the chemical structure of adhesives with different curing degree. The results show that higher of hot press temperature, the shorter of time to reach the target temperature. The changed rate constant of bonding strength and the maximum bonding strength of plywood could be calculated by the mechanical mathematical model accurately, and the temperature at 130°C was the optimal temperature for plywood manufacture in the study. FTIR analysis indicated that the primary reaction of PF adhesive in the alkaline medium was the condensation occurring between hydroxymethyl groups and residual active position of other phenolic rings. NMR data presented that the ratio of -CH₂- (34.5–35.1 ppm)/CH₂-OH (62.4–63.1 ppm) could be used to evaluate the curing degree of PF adhesive.

摘要

在研究中，评估了不同热压温度和时间下酚醛（PF）胶粘剂在胶合板上的粘合强度。建立了PF胶粘剂固化过程的力学数学模型，模型参数可用于预测胶合板的粘合强度和变化率。采用差示扫描量热法(DSC)、傅里叶变换红外(FTIR)和核磁共振(NMR)等方法测定胶粘剂的热固化程度，分析不同固化程度胶粘剂的化学结构。结果表明，热压温度越高，达到目标温度的时间越短。通过力学数学模型可以准确计算出胶合板胶合强度变化率常数和最大胶合强度，研究中胶合板制造的最佳温度为130℃。FTIR分析表明，PF粘合剂在碱性介质中的主要反应是羟甲基与其他酚环的剩余活性位发生缩合反应。NMR数据表明-CH的比例₂ - (34.5–35.1 ppm)/CH ₂ -OH (62.4–63.1 ppm)可用于评价PF粘合剂的固化程度。