Effects of Block Copolymer Terminal Groups on Toughening Epoxy-Based Composites: Microstructures and Toughening Mechanisms

Abstract

Despite the considerable research attention paid to block copolymer (BCP)-toughened epoxy resins, the effects of their terminal groups on their phase structure are not thoroughly understood. This study fills this gap by closely examining the effects of amino and carboxyl groups on the fracture toughness of epoxy resins at different temperatures. Through the combination of scanning electron microscopy and digital image correlation (DIC), it was found that the amino-terminated BCP was capable of forming a stress-distributing network in pure epoxy resin, resulting in better toughening effects at room temperature. In a 60 wt.% silica-filled epoxy composite system, the addition of a carboxyl-terminated BCP showed little toughening effect due to the weaker filler/matrix interface caused by the random dispersion of the microphase of BCPs and distributed silica. The fracture toughness of the epoxy system at high temperatures was not affected by the terminal groups, regardless of the addition of silica. Their dynamic mechanical properties and thermal expansion coefficients are also reported in this article.

Delamination of Plasticized Devices in Dynamic Service Environments

“…Its optimal delamination resistance index was 74, demonstrating excellent delamination resistance ( Table 6 ). Amino end-capped PCBs prepared by Li et al [ 113 ] as a second-phase modifier increased the fracture toughness of EP/Amino-BCP/SiO 2 at room temperature by 31.2% in the presence of 60 wt% SiO 2 ; CTE1 increased by 6.1 ppm/K; and CTE2 was largely unaffected. Through comparative experiments, Yang et al [ 114 ] found that amino block copolymers and silicone block copolymers showed a good toughening mechanism as toughening agents for bottom filling.…”

Modification on PBS using epoxy-functionalized core-shell starch particles

“…Additionally, the performance of core-shell particles can be regulated by altering the types of monomers [14,15] . However, due to weak interfacial interactions and poor dispersibility [16,17] , simply blending core-shell modi ers with the matrix polymer often fails to achieve satisfactory toughening effects [18][19][20][21] . Reactive compatibilization is an effective method to enhance the interfacial strength and compatibility between the toughening agent and the matrix [22] .…”