Waterborne epoxies as secret performance enhancers in fiber and textile applications
Epoxy is a general term used to describe polymers that contain an epoxide functional group. These molecules have been around for a long time and are well-known for many applications, including composite matrices, coatings, civil engineering and adhesives. However, less know is the fact that epoxy treated fibers and textiles play a significant role in our daily lives by contributing to the proper functioning of wind blades, under the hood components, water filtration, kitchen appliances and even some protective clothing, just to name a few! For epoxies to be successful in these applications, they must be compatible with water, particularly when synthetic fibers (e.g. PBT, PET) are used, given that their performance could be compromised by the presence of organic solvents. A major advantage of using waterborne epoxy dispersion is the reduction of Volatile Organic Compounds (VOCs) and the absence of free phenol and formaldehyde. This, in fact, makes waterborne epoxies a more sustainable technology. We will therefore be taking a closer look at how epoxy dispersions are the “secret ingredient” that help fibres perform in two key areas: as fibre sizing film formers and as an adhesive for fibre binder applications.
- Film former in fiber sizings
Image 1 | Fiberglass chopped strand mat
Fibre sizings serve a multitude of requirements starting with the manufacturing of the fibre to maximise the performance of the final product. The film former is the main component in a sizing formulation, and it plays a crucial role in the production and use of carbon, glass and basalt fibers. During the fiber manufacturing process, the sizing lubricates and protects the fiber as it is gathered into tows, chopped or woven into fabrics. The compatibility of the film former with both the fibre and the matrix is crucial for the final performance of the composite part and can be achieved by the presence of unreacted epoxy groups on the fibre surface to react into the matrix thus forming an indestructible chemical bond. The fibre sizing also helps achieve faster throughput of composites production, since it protects the fibres during aggressive processing such as Resin Transfer Moulding (RTM), pultrusion and others. Additionally, the film former dispersion can be designed to impart specific composite properties such as toughness, fatigue, moisture resistance and handling. The typical matrixes reinforced with epoxy treated fibre would be epoxy, phenolic and several engineering thermoplastics.
- Binders for non-wovens and Textile treatments
Non-woven fabric is a fabric-like material made from staple fibre and long fibres, bonded together by chemical, mechanical, heat or solvent treatment. The term is used in the textile manufacturing industry to denote fabrics such as felt which are neither woven nor knitted. The desired orientation of the fiber will determine the final properties of the fabric; therefore, it is essential to maintain this preferred orientation. The epoxy binders are used as adhesives to hold non-woven fibers in the desired orientation whether they are crosslinked or not. Epoxies are used as textiles treatments to provide specific performance benefits. In order to accomplish the desired performance improvement, epoxies are typically crosslinked using water soluble or water compatible curing agents and cured at elevated temperatures. Typical properties that can be improved by using epoxy dispersions are chemical, thermal and abrasion resistance among others. Epoxy water dispersions are a sustainable solution for these applications as it extends the product life cycle compared to other less expensive competing technologies. Typical end-use products in our daily life would be oil filters, water membranes or geotextiles, coated and structural abrasives, and even protective clothing.
Images 2 & 3 | Typical end products for waterborne epoxy dispersions: protective clothing (left) and oil filter (right)
