用接枝后的聚四氟乙烯(PTFE)对酚醛树脂进行化学增韧改性并探究最佳工艺及配方,以提高酚醛树脂的力学和磨削性能。通过钠-萘四氢呋喃活化液对PTFE进行化学活化后进行丙烯酸接枝,以期获得带有羧基的PTFE(PTFE-g-PAA),并通过返滴定法测定其接枝率。利用羧基与羟基的酯化反应使得PTFE-g-PAA参与酚醛树脂的合成反应,测定酚醛树脂的力学性能和磨削性能。结果发现,采用20mL浓度为0.3mol/L的钠-萘四氢呋喃活化液活化3min的PTFE活化效果最佳。在50℃、过硫酸铵浓度8×10-3mol/L、反应20h条件下,PTFE-g-PAA的接枝率最高为8.02%。随着PTFE-g-PAA接枝率的增加,改性酚醛树脂的抗冲击强度、抗折强度、硬度和磨削比均提高;随着PTFE-g-PAA加入量的增大,PTFE-g-PAA改性酚醛树脂的抗冲击强度、抗折强度和磨削比先提高后下降,而硬度一直上升。PTFE-g-PAA接枝率越高,对材料的力学性能提高越明显,而当PTFE-g-PAA的添加量为1%～2%时,材料的综合性能最佳。
The phenolic resin(PF) was chemically toughened and modified by grafted polytetrafluoroethylene powder and the optimum process and formulation were explored to improve the mechanical and grinding properties of the PF.The polytetrafluoroethylene was chemically activated by a sodium-naphthalene tetrahydrofuran activation solution,followed by acrylic acid grafting to obtain a carboxyl group-containing polytetrafluoroethylene,and the graft ratio was determined by a back titration method.The esterification reaction of carboxyl group and hydroxyl group made PTFE-g-PAA participate in the synthesis reaction of the PF,and the mechanical properties and grinding performance of the PF were determined.The activation effect was best when activated by a 20mL concentration of 0.3mol/L sodium-naphthalene tetrahydrofuran activation solution for 3min.The grafting rate of PTFE-g-PAA was up to 8.02% at 50℃,ammonium persulfate concentration of 8×10-3mol/L and reaction for 20h.As the graft ratio of PTFE-g-PAA increased,the impact strength,flexural strength,hardness and grinding ratio of the modified PF increased.As the amount of PTFE-g-PAA added increased,the impact strength,flexural strength,and grinding ratio of the PTFE-g-PAA modified PF increased first and then decreased,and the hardness increased.The higher the grafting rate of PTFE-g-PAA,the more obvious the mechanical properties of the material were improved,while the addition amount of PTFE-g-PAA was 1%～2%,and the comprehensive performance of the material was the best.
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