Abstract
Epoxy resins are widely used for different commercial applications, particularly in the aerospace industry as matrix carbon fibre reinforced polymers composite. This is due to their excellent properties, i.e., ease of processing, low cost, superior mechanical, thermal and electrical properties. However, a pure epoxy system possesses some inherent shortcomings, such as brittleness and low elongation after cure, limiting performance of the composite. Several approaches to toughen epoxy systems have been explored, of which formation of the interpenetrating polymer network (IPN) has gained increasing attention. This methodology usually results in better mechanical properties (e.g., fracture toughness) of the modified epoxy system. Ideally, IPNs result in a synergistic combination of desirable properties of two different polymers, i.e., improved toughness comes from the toughener while thermosets are responsible for high service temperature. Three main parameters influence the mechanical response of IPN toughened systems: (i) the chemical structure of the constituents, (ii) the toughener content and finally and (iii) the type and scale of the resulting morphology. Various synthesis routes exist for the creation of IPN giving different means of control of the IPN structure and also offering different processing routes for making composites. The aim of this review is to provide an overview of the current state-of-the-art on toughening of epoxy matrix system through formation of IPN structure, either by using thermoplastics or thermosets. Moreover, the potential of IPN based epoxy systems is explored for the formation of composites particularly for aerospace applications.
Highlights
Epoxy thermosetting resins were discovered between the 1930s and 40s by P
The results revealed the enhancement in the mechanical properties of epoxy system as a function of increasing content of polysulfide due to its flexible nature
The results showed an increase in energy dissipation mechanisms by increasing PDCPD content in epoxy
Summary
Epoxy thermosetting resins were discovered between the 1930s and 40s by P. An IPN structure, which is typically formed by the interpenetration and grafting reaction, for example between both polymers, respective of their monomers, remain soluble with a clear transparent solution, (ii) phase separation occurs during polymerization through nucleation and growth mechanism, (iii) which can in some cases transition to formation of interconnected cylinders, spinodal decomposition and (iv) further polymerization results in growth of domains [30]. The list of abbreviations is provided in homogeneously blended at the molecular scale [32,33]
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