Preparation And Properties Of Modified Epoxy By Polyimide With Trifluoromethyl

As we all know, epoxy resin （EP） has excellent performance, but some of their inherentdisadvantages such as poor heat resistance, poor toughness and great hygroscopicity etc.affect their more widespread use. Therefore, modifying EP becomes necessary.Studies show that fluorine-containing groups have low molar polarization degree, stronghydrophobicity and thermal stability, and can also improve the dielectric properties ofmaterials that include them. In addition, polyimide not only can enhance the heat resistance ofthe epoxy resin, but also can improve toughness. In this thesis, two modified methods wereconducted.The first method: synthesized5kinds of amino-terminal polyamic acid withtrifluoromethyl group, then they will serve as amine curing agent and cure EP, finally,conducted a series of characterization of the cured. FT-IR results showed that the epoxycompletely cured and the polyamic acid completely dehydrated into polyimide. Tg aftermodificating were higher than the previous6⁴0℃range, showed this modified method canimprove heat resistance of EP, TGA results also confirmed this point. Cross-sectionsobservation by SEM, we found sections were rough, but smooth before modificating, showthis method can improve toughness of EP. Water absorption of materials after modificatingwas reduced from0.7%to1.0%, and contact angle increased6¹0°, showed lower affinity forwater after modificating. Tensile shear strength tests showed that results after modificatingwere less than those before modificating. The reason may be introduction of trifluoromethylgroup reduced the force between the molecular chains and thereby reduced the adhesive.The second method: synthesized3kinds of CIM polyimides with trifluoromethyl group,then mixed them into EP system as additives. FT-IR shows the peak915cm^-1of epoxy groupdisappeared, indicated completely cured. DSC results showed polyimide had an optimaladdition amount, the system had the highest Tg in this critical mass, to PI^-1, the critical masswas10%, but to PI-2and PI-3, the critical mass was20%. Similarly, cross-section were roughshowed this method can also improve toughness of EP. Water absorption test andcharacterization of the contact angle showed a good hydrophobicity after modificating. Tensile shear strength was the same as before for similar reasons.In summary, through the above two methods can improve heat resistance, toughness ofepoxy as well as reducing its absorbency, provides effective modified methods for widerapplication of EP.