酚醛改性环氧类玻璃体的制备及其自修复性能

Preparation and self-healing property of phenolic modified epoxy vitrimer

类玻璃体(Vitrimer)在保持交联的状态下还具有塑性变形能力,意味着传统的热固性树脂具有了二次热加工成型的能力,有效地减少废品率,从源头减少垃圾。利用Vitrimer具有的塑性变形能力也可以进行材料自修复而延长使用寿命,从而对环境保护、减排作出贡献。本文以异辛酸亚锡为催化剂、酚醛树脂为改性剂制备了环氧Vitrimer材料。研究结果表明:催化剂含量的增加会使体系固化更加完全,因此对材料弯曲强度有一定的改善,最高可达到87.5 MPa。引入酚醛树脂后弯曲强度由改性前的87.5 MPa提高到126.9 MPa,拉伸强度达63.3 MPa。但酚醛树脂的加入量过高时,材料的交联密度有所降低,其力学性能在达到顶点后出现下降趋势。对酸酐固化的环氧Vitrimer体系松弛过程研究表明:增加催化剂含量和提高温度都可以降低材料的松弛时间,但是高温后固化会抑制松弛过程,影响自焊接强度。酚醛改性后材料的应力松弛明显快于纯酸酐固化的环氧试样。10mol%催化剂试样在180℃至190℃松弛速率产生一个突变,190℃明显加快,而酚醛的引入则可以将突变温度Ts提前到180℃。在无压力条件下,样品可以实现划痕的修复。在松弛的突变温度以上修复的试样剪切强度和划痕修复效果明显提高。相对未加酚醛样品,酚醛改性样品修复效果更好。催化剂对试样修复强度和修复速度有明显影响。

Vitrimer can undergo plastic deformation while maintaining a cross-linked state,which means that traditional thermosetting resins have the ability to undergo secondary thermal processing and molding,which will effectively reduce scrap rates and reduce waste from the beginning.The plastic deformation of vitrimer can also endow item self-healing ability and extended its service life,and so contribute to environmental protection and emission reduction.In the paper stannous iso-octanoate as a catalyst and phenolic resin as a modifier was used to prepare anhydride cured epoxy vitrimer materials.The research results indicate that the increase in catalyst content could make the system cure more completely,so there is a certain improvement in the bending strength of the material,up to 87.5 MPa.With introduction of phenolic resin,the bending strength increases from 87.5 MPa before modification to 126.9 MPa,and the tensile strength reaches 63.3 MPa.When the amount of phenolic resin added is too high,the crosslinking density of the material decreases,and the mechanical properties of the material show a downward trend.The study on the relaxation behavior of the epoxy vitrimer system cured with pure anhydride shows that increasing the catalyst content reduces the relaxation time of the materials,but the post curing reaction at high temperature could inhibit the relaxation process and suppress the self-welding strength.The stress relaxation of epoxy vitrimer material modified with phenolic resin is significantly faster than that of epoxy vitrimer system cured with pure anhydride.The relaxation of the samples with 10mol%catalyst shows a sudden change,and there is a significant acceleration when the temperature rises to 190℃,and the introduction of phenolic resin could advance the sudden change temperature Ts to 180℃.Under no pressure conditions,scratches are repaired.The tensile shear strength and scratches repair effect of the samples repaired above Ts are significantly improved.Compared to samples without phenolic resin,phenolic modified samples could be repaired better.Catalyst have a significant impact on the repair strength and repair speed of the samples.