Recently, different forms of rubber modifiers such as block copolymers have been used, and these can form complex microstructures. Thermoplastics such as polyethersulfone and polyetherimide have also been used. Among these, a very successful approach has been the addition of carboxyl-terminated butadiene acrylonitrile (CTBN) rubber which phase-separates into micron-sized particles during curing. The addition of a rubber, thermoplastic or block copolymer phase which is soluble in the resin but phase-separates during curing of the epoxy is commonly used to toughen epoxy polymers. It is thus essential to increase the toughness of epoxies. They are used in safety-critical structural applications, as they enable lightweight construction and promote fuel efficiency, for example in the construction of aircraft, cars and ships. It is difficult to detect cracks in adhesively-bonded and fibre-composite structures, as the critical flaw size is very small due to their brittle nature, so the epoxies must be modified to prevent premature failure. Due to this brittle nature, the resultant stresses will cause further damage or propagation of existing cracks, which will greatly affect the lifetime of the component and may lead to catastrophic failure. In service, the epoxy will experience static, cyclic or impact loading. However, this microstructure makes epoxies extremely brittle, and they have a poor resistance to the initiation and propagation of cracks from the defects which are naturally present. They exhibit many useful properties such as a high modulus, high service temperature and no creep due to their highly cross-linked structure. This shows how epoxies can be toughened successfully for use in industrial and transport applications.Įpoxies are thermosetting polymers which are used as adhesives, coatings and matrices of fibre-reinforced composites. Toughening using silica nanoparticles is especially efficient at low particle contents. Analytical models were used to predict the modulus and fracture energy the predictions agreed very well with the measured values. The fracture and toughening mechanisms were identified by scanning electron microscopy of the fracture surfaces. The fracture energy was measured at ambient and low temperature (− 40 ☌ and − 80 ☌) to understand the brittle fracture behaviour. An anhydride-cured thermosetting epoxy polymer has been modified by the addition of different wt% of silica nanoparticles, core–shell rubber particles and hybrids with equal wt% of both. Users should refer to the original published version of the material for the full abstract.The highly cross-linked thermosetting polymers used as adhesives and as the matrices of fibre composites for the construction of lightweight vehicles are very brittle, and finding effective toughening solutions for such engineering applications is a long-standing problem. No warranty is given about the accuracy of the copy. However, users may print, download, or email articles for individual use.
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