The aerospace industry has been looking for hard, strong, and lightweight materials to cope with rapid changes in temperature and a wide range of chemical substances in contact with the environment. At the same time, the material must have a long service life with excellent fatigue resistance. Thanks to composite-intensive aircraft-such as the introduction of Boeing ’s 787 Dreamliner in 2011 and Airbus SE ’s A350 XWB in 2015, due to the ability of composite materials to reduce weight and weight, the use of composite materials on commercial aircraft Greatly reduce fuel consumption and maintenance, improve corrosion resistance and fatigue resistance. To better support customers in the US aviation / aerospace industry, Sumitomo Chemical has developed two new grades of higher viscosity epoxy resins for easier processing, and also developed a new grade of polyethersulfone (PES) Additives to improve the fracture toughness and micro-crack resistance of carbon fiber reinforced epoxy composites.
To meet the aviation industry's demand for high-performance and high-productivity carbon composite materials, Sumitomo Chemical has developed two new grades of epoxy resins for prepreg production. Compared with standard aerospace grades – Sumi-Epoxy ELM 434 has a viscosity of 11,900 mPa-s – the new -434L has a viscosity of 8,200 mPa-s and the new 434VL has a viscosity of 5,100 mPa-s. Sumitomo also offers two high-temperature grades (Sumi-Epoxy ELM-100 and 100H), and their Tgs are both 260 ° C, while the standard temperature of ELM-434 is 230 ° C.
Sumitomo has also expanded its supply of SumikaExcel PES micron powder tougheners for epoxy resin composites. In addition to its standard grade SumikaExcel 5003P, a new lower molecular weight 2603P grade has also been introduced. Standard 5003P grades have a viscosity of 0.52 dl / g, while the new 2603P grades have a viscosity ratio of 0.26 (both measured in 1% PES in N at 25 ° C, N-dimethylformamide (DMF) ). The molecular weight (Mw) of 5003P is 42,000, while the molecular weight of 2603P is 16,000. In addition, the Tg of 5003P measured with a differential scanning calorimeter is 227 ° C, and the Tg of 2603P is 220 ° C. The new 2603P grade also has more terminal -OH groups than standard grades (4.5 to 1.1 per 100 units).
SumikaExcel 2603P is a low-viscosity PES additive, which is beneficial to aerospace composite materials. In epoxy / PES matrix combinations, even at low pressure control ratios, its viscosity is highly dependent on the molecular weight of PES. Although the original SumikaExcel 5003P additive can effectively improve the fracture toughness of epoxy composites, due to the high viscosity of the mixed resin system, formulators cannot always easily add the required amount of additives, especially in prepreg Material production process. By choosing to use the lower viscosity 2603P grade, formulators can now increase the ratio of PES to epoxy resin, thereby further improving the toughness of the final composite. Alternatively, formulators can add other polymers and additives to further change the functional properties of the composite. Another option is that formulators can choose a new lower viscosity Sumi-Epoxy grade instead of using lower molecular weight PES to reduce the viscosity of the combined polymer matrix.
Epoxy resins are thermosetting polymers, known for their heat and chemical resistance, electrical resistivity and high mechanical properties-especially when reinforced with carbon fiber, aramid, boron or glass fiber. It can be easily modified through mineral fillers, reinforcing fibers, tackifiers, viscosity reducers, viscosity thickeners, colorants, accelerators, plasticizers, co-reactants, etc., and can be formulated to provide a wide range of properties. It can be used in a wide range of industries-from high-performance coatings, structural adhesives to tools for forming plastic and composite parts, structural composites for the wind energy, automotive, marine and aerospace industries, and electronic components (from circuits Board to half are used as conductor sealants and potting compounds for transformers and inductors).
PES is an amber transparent amorphous engineering thermoplastic. The material has the following advantages: high temperature performance, high strength and impact resistance, creep resistance under high temperature and high load, very good dimensional stability, in Low coefficient of linear thermal expansion (CLTE) over a wide temperature range, inherent flame retardancy, low smoke, minimal outgassing, good and extensive chemical resistance and hot water resistance. It is used in granular form for injection molding, extrusion and film processes, in powder form for cast films, filter membranes, and as an additive for epoxy-based composite materials, high-temperature coatings / coatings and adhesives. PES materials are used in the aerospace, automotive, electrical / electronics, medical equipment, and food processing industries.
When ground into micron powder, PES proves to be a very effective additive that can enhance the fracture toughness and micro-crack resistance of epoxy composites, whether in the form of prepregs or polymerization of resin transfer molding (RTM) Thing. It can provide these properties over a wide temperature range without negatively affecting dimensional stability, flame / smoke / toxicity (FST), creep resistance, modulus, impact strength or yield strength. Specific PES grades with hydroxyl (-OH) end groups are used as functional additives for epoxy composites and can react with glycidyl groups on epoxy substrates to form cross-linked interpenetrating polymer networks (IPN). Even if the additive is usually used at a rate of 2-12 wt%, it adds greater flexibility to the IPN, which in turn improves the toughness of the epoxy composite. PES usually has a glass transition temperature (Tg) of 225-230 ° C, which is higher than the temperature of aviation-grade epoxy resins with an average of 120-200 ° C. Because PES additives also have good rigidity and strength, they can improve impact resistance and crack resistance without affecting other thermomechanical properties. Especially important in aerospace applications, it can do all this without affecting FST or molding and maintaining very tight tolerances. Although it is most commonly used with high-performance carbon fiber-reinforced epoxy composites, it is also effective for glass, aramid or basalt-reinforced epoxy resins.
Sumitomo can customize its epoxy and PES grades (and even provide epoxy grade PES additives) to meet customers' specific requirements for processability and functionality.