三聚氰胺改性对木质素酚醛树脂胶合性能的影响

Synthesis and bonding performance analysis of melamine-modified lignin phenolic resin

【目的】通过三聚氰胺对木质素酚醛树脂(LPF)改性,提高LPF的胶合性能,降低固化温度,为人造板的绿色生产和节能降耗提供新思路。【方法】对比三聚氰胺与(苯酚+木质素)、三聚氰胺/(苯酚+木质素)与甲醛不同摩尔比对三聚氰胺改性木质素酚醛树脂(MLPF)的性能影响,得到MLPF的最佳合成条件。并与相同酚醛比和木质素取代率的酚醛树脂(PF)和LPF进行性能对比,利用FTIR和DSC对PF、LPF和MLPF的结构和固化温度进行比较分析。【结果】当三聚氰胺与(苯酚+木质素)的摩尔比为4∶6、三聚氰胺/(苯酚+木质素)与甲醛的摩尔比为1∶2时,MLPF的凝胶时间最短,为318.62 s,所压制的MLPF胶合板干、湿胶合强度为2.04和1.43 MPa,甲醛释放量为0.088 mg/m^(3),且与PF和LPF胶合板相比MLPF的胶合强度更高,满足GB/T14732—2017和GB/T 9846—2015国家标准性能要求。FTIR结果显示,相较于PF和LPF,MLPF在3 327 cm^(-1)和3 214 cm^(-1)处拥有属于-OH和-N-H的双峰,在1 079 cm^(-1)和1 036 cm^(-1)处出现的N-C-N特征峰以及在809 cm^(-1)处属于三嗪环面外震动的吸收峰,都证明了三聚氰胺经过羟甲基化并参与到MLPF的合成中。DSC结果显示,经过三聚氰胺改性后的MLPF放热峰值温度出现在140℃,其固化温度相较于LPF和PF分别降低了17.16%和22.22%。【结论】三聚氰胺的加入使得MLPF的凝胶时间更短,固化温度更低,MLPF胶合板的性能相较于LPF无论是胶合强度还是耐水性均有明显提升。

【Objective】Through adding melamine to lignin phenol formaldehyde resin(LPF),its bonding strength was enhanced and its cure temperature was decreased.Therefore,a novel strategy was presented for the environmentally friendly manufacture of wood-based panels.【Method】The performance of melamine-modified lignin phenol formaldehyde resin(MLPF)was tested to study the effect of different molar ratios of melamine and(phenol+lignin),melamine/(phenol+lignin)and formaldehyde,and find the best MLPF synthesis conditions.In addition,the performances of phenolic resin(PF)and LPF with the same phenolic ratio and lignin replacement rate were compared.The structure and curing temperature of PF,LPF,and MLPF were compared by FTIR and DSC.【Result】The MLPF gel time was shortest at 318.62 s,when the molar ratios of melamine to(phenol+lignin)and melamine/(phenol+lignin)to formaldehyde were 4:6 and 1:2,respectively.The MLPF plywood’s dry and wet bonding strengths were 2.04 MPa and 1.43 MPa,respectively,and its formaldehyde release was 0.088 mg/m^(3).MLPF had a stronger bonding strength than PF and LPF plywood,fulfilling the performance requirements of GB/T 14732-2017 and GB/T 9846-2015 national standards.According to FTIR studies,MLPF differed from PF-1 and LPF in that it possessed double peaks for-OH and-N-H at 3327 cm and 3214 cm^(-1),-1 N-C-N characteristic peaks at 1079 cm and 1036 cm^(-1),and triazine torus absorption peaks at 809 cm^(-1).It was proved that melamine was hydroxymethylated and involved in the synthesis of MLPF.The exothermic peak temperature of MLPF was 140℃,which was lower by 17.16%and 22.22%compared to that of LPF and PF,respectively.【Conclusion】The addition of melamine decreased the curing temperature and shortened the gel time of MLPF.The performance of MLPF plywood was much superior to that of LPF in terms of bonding strength and water resistance.