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Adhesion Strength of Block Copolymer Toughened Epoxy on Aluminum
ACS Applied Polymer Materials ( IF 4.4 ) Pub Date : 2019-12-26 , DOI: 10.1021/acsapm.9b00909
Vincent Pang 1 , Zachary J. Thompson 2 , Guy D. Joly 2 , Frank S. Bates 1 , Lorraine F. Francis 1
Affiliation  

The effect of poly(ethylene-alt-propylene)-b-poly(ethylene oxide) block copolymer modifiers on the adhesion strength of epoxies was evaluated. Three block copolymer modifiers of varying block weight fractions were synthesized and mixed into the epoxy precursors and cured, forming well-dispersed nanoscale structures in the epoxy matrix. The symmetric block copolymers formed spherical micelles, and the asymmetric block copolymer with shorter poly(ethylene oxide) blocks formed small bilayer vesicles in the epoxy matrix. For both block copolymer nanostructure morphologies, compact tension tests of bulk specimens showed that modified epoxies exhibited a significant improvement in critical strain energy release rate, GIc, over the neat epoxy with no reduction in the elastic modulus. When spherical micelle modified epoxies were used as adhesives for aluminum, single-lap-joint shear tests showed an apparent adhesion strength enhancement of up to ∼46%, with increased cohesive failure. Electron micrographs of the topological features on the fracture surfaces of these materials indicate that micelle cavitation plays a role in both the toughening and adhesion strength enhancement of these epoxies. By contrast, a 28% reduction in adhesion strength was observed in the bilayer vesicle modified epoxies. Possible mechanisms for the disparate adhesion strength results for the two types of block copolymer modified epoxies are discussed.

中文翻译:

嵌段共聚物增韧环氧树脂在铝上的粘合强度

聚的效果(乙烯ALT -丙烯) - b上的环氧树脂的粘合强度-聚(环氧乙烷)嵌段共聚物改性剂进行评价。合成了三种具有不同嵌段重量分数的嵌段共聚物改性剂,并将其混合到环氧前体中并固化,从而在环氧基质中形成分散良好的纳米级结构。对称嵌段共聚物形成球形胶束,具有较短聚环氧乙烷嵌段的不对称嵌段共聚物在环氧基质中形成小的双层囊泡。对于这两种嵌段共聚物的纳米结构形态,大块试样的致密拉伸试验表明,改性环氧树脂在临界应变能释放速率G Ic上有显着改善。在纯环氧树脂上,弹性模量没有降低。当球形胶束改性的环氧树脂用作铝的粘合剂时,单搭接剪切试验显示表观的粘合强度提高了约46%,并且内聚破坏增加了。这些材料的断裂表面上的拓扑特征的电子显微照片表明,胶束空化在这些环氧树脂的增韧和粘合强度增强中均起着作用。相反,在双层囊泡修饰的环氧树脂中观察到粘合强度降低了28%。讨论了两种类型的嵌段共聚物改性环氧树脂产生不同粘合强度结果的可能机理。
更新日期:2019-12-27
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