Epoxy Resin
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Epoxy Laminating Resin
Epoxy 5752-105 Laminating System for hand-layup. Combines both epoxy resin...Read more -
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Laminating epoxy resins are suitable for a wide range of wet lay-up applications.
These resins are intended for the production of performance composites when paired with carbon fibre and other fibre-based reinforcements.
They demonstrate superior physical properties at room temperature and are amenable to post-curing at for enhanced performance.
Key features of epoxy resins include, but are not limited to:
+ High moisture resistance
+ Heat resistance and thermal resistance
+ Fatigue resistance
+ High adhesive strength
+ Low shrinkage
How does epoxy resin work?
The benefits of epoxy resin are fully realised when it is in a solid state. The epoxy thermoset reaction involves a molecule that is functionalised with epoxide groups and a hardener (cross-linking agent). Mixing epoxy resin with a hardener will initiate a chemical reaction with transitions the epoxy from a viscous liquid into a solid structure. The curing process takes several hours and as the epoxy cures, it moves through a gel state prior to a solid state. This process is often referred to as the crystallisation of epoxy.
Most epoxies are categorised as cycloaliphatic, epoxied oils or glycidated resin. Diglycidyl ethers of bisphenol A (DGEBPA) are obtained via the bisphenol A (BPA) reaction with epichlorohydrin (ECH).
The chemical features of epoxy resin, such as molecular weight and viscosity, can be tailored towards manufacturing and product application requirements. Molecular weights can be adjusted based upon the ratio of ECH to BPA; higher ratios generate lower molecular weights. BPA itself exerts toughness, rigidity and thermal performance, with ether links exert chemical resistance and hydroxyl and epoxy functional groups exert adhesiveness.
Epoxy Coatings
As coatings, epoxy present several advantages centring on its temperature stability, adhesiveness and resistance to solvents.
Epoxy Composite Reinforcements
In addition to uses as adhesives and coatings, the primary benefits of epoxy resin are realised when used in conjunction with fibre-based reinforcements like carbon fibre, glass fibre and aramid fibre.
The process of applying epoxy resin to reinforcement is referred to as ‘laminating’. The purpose here is to infuse the resin into the reinforcement, ensuring a desirable resin-reinforcement ratio is achieved, that air pockets are removed and resin is uniformly dispersed. These are all important features in ensuring effective composite performance and a deviation from these often leads to failure, evidenced by cracks, splits and an overall loss of mechanical performance.
This can be achieved via hand lay-up, resin transfer moulding and prepreg practices, the latter involving the use of resin that is pre-impregnated into reinforcement fabric. This means it can be trimmed, stacked and placed onto a mould surface. Following the application of heat, the prepreg can be consolidated and cured.
Note: it is important to select reinforcements based upon resin compatibility. Emulsion bound chopped strand glass fibre mat contains styrene and should not be used with epoxy resin as it cannot be dissolved.
Epoxy Fillers
Resins like epoxy offer excellent strength-to-weight ratios, versatility and chemical resistance, but they are limited when compared to metals in the context of machinability, thus limiting their applications in the context of wear.
Resin fillers and powders add an additional dimension to the properties of epoxy-based coatings and parts. It has long been known that fillers can benefit the properties of epoxies, overcoming some of the limitations in terms of corrosion resistance and wear- and tear-related friction.
Classic examples include glass beads, graphene powders, as well as fibre-based fillers such as forged carbon, with others in development. Their benefits centre on enhanced abrasion resistance, friction reduction and improvements in overall durability – one of the main aims being to better match the characteristics of the metals they are aiming to replace. Indeed, combining the properties of the individual components, such as the excellent specific strength of epoxy resin with the wear-resistance of a filler leads to a superior material. Such improvements in epoxy resin via fillers are widely published.
Epoxy Aggregates
Larger particulates (aggregates) are preferred for more rigorous applications like flooring. Epoxy resin is a popular choice for flooring. Epoxy resins encapsulate the aggregate, enabling the resultant structure to be mechanically superior to resin alone.
As with other reinforcements, it is important to ensure that the aggregate is adequately blended into the epoxy resin, ensuring air pockets are removed, the aggregate itself is well dispersed and each particle is adequately encapsulated by resin. These types of systems are often multi-layered and are applied to primer-coated concrete surfaces. A final layer of protective resin is applied to the aggregate-based based mid-layer offering abrasion resistance and overall aesthetics.
Epoxy Resin Laminating
Laminating is a primary use of epoxy resin. Composite parts are created from carbon fibre, glass fibre and other reinforcements, its applications include aircraft, space, military, marine, construction, sports, automotive industrial sectors.
Epoxy resin has a broad range of applications in the fabrication of composite parts. Formulation adjustments have been made to the resin to ensure optimal processing and performance.
Epoxy laminating resin is specially formulated to enable optimal processing and curing. They are formulated for the binding of fibre-based reinforcement materials like glass, carbon and aramid.
Note: before starting a laminating procedure, please test the resin-reinforcement in advance.
Note: when using an epoxy resin, pease ensure that any reinforcement material is compatible with it. Epoxy resin is not compatible with styrene-soluble binders.
Laminating fabrics can be wetted out by hand or using roller impregnating machines.
In the context of laminating, epoxies are adaptable and are formulated for different laminating procedures:
Laminating reinforcements include carbon fibre, glass fibre and aramid fibres in plain, twill, and other weave types.
Whilst epoxies demonstrate a higher up-front cost, their longevity and performance means they are more economical in the long-run.
Epoxy resins present several benefits that make them ideal for a range of applications:
Versus traditional resins like unsaturated polyester, epoxies possess several advantages:
Conversely, epoxy resin does have some drawbacks in some aspects of its use. These are listed below, but note these instances would involve the resin being used outside of specification. In addition, many of the limitations ca be overcome via protective coatings and correct application environments.
The ability for epoxy resin to form a single, unified structure via cross-linking means it can be engineered to create seamless, mechanically strong structures.
With significant resistance to water, chemicals, abrasion and other physical stressors, it has applications in the marine, construction, automotive, aerospace and various manufacturing industries.
These include as the matrix phase in composite structures, as well as adhesives and protective coatings. This level of versatility means it is an excellent alternative to metals and welding, particularly in the context of composite structures and can be used to make repairs in existing structures.
The choice of epoxy resin should be carefully selected based upon the intended application. Epoxy should be used with carbon fibre, glass fibre (powder bound matting), aramid fibre (Kevlar®) and or woving roving matt.
