Epoxy systems for low temperature applications
Epoxy-based formulated products are finding increased utility in a wide variety of structural and electrical applications that are required to operate in low temperature environments. Cryogenic technology is accelerating the growth in these fields. This versatile thermosetting polymer offers many attractive features such as high mechanical strength, outstanding dielectric characteristics, excellent adhesive properties, very good chemical resistance and excellent thermal endurance. Such features make them materials of choice for high and medium voltage electrical apparatus that operate in below zero Celsius environments. At lower operating temperatures, many factors come into play affecting overall performance. Among these factors are: speed and effectiveness of cure, fracture toughness characteristics, and thermal expansion properties.
Factors influencing the glass transition of DGEBA-anhydride epoxy resins
Abstract A number of chemical and physical factors influence the glass transition behaviour of anhydride-cured diglycidyl ether of bisphenol A (DGEBA) type epoxy resins. Several of these were investigated using differential scanning calorimetry to assess the nature of the glass transition, the transition temperature and the glass- and liquid-phase specific heats. The influence of molecular weight and chemical functionality, cooling rate and silica fillers were investigated for unreacted epoxy prepolymers. Two anhydride-cured systems were also considered and the influence of cure with and without silica fillers and the effect of phase separation and cooling rate were investigated.
SMC composites waste management as reinforcing fillers in polypropylene by combination of mechanical and chemical recycling processes
A new process of management of waste of composite materials from Sheet Moulding Compounds (SMC), as reinforcing fillers for thermoplastic materials, including both mechanical and chemical processes is proposed in this paper. Communited SMC being composed of coated glass fibres intimately mixed with calcium carbonate powder, their reinforcing power is low. First, the fibrous part was increased by partial dissolution of calcium carbonate present in the crushed products SMC. Second, a process of partial solvolysis was developed aiming at strong increasing the interfacial mechanical properties by functionalising of SMC load incorporated into polypropylene/grafted maleic anhydride polypropylene (PP/PPgma). At this effect, we investigated a treatment with a hot triamine (diethylenetriamine, DETA) in order to create a functionalisation, after scission of the bond ester of unsaturated polyester, as bridging amino-succinimide.The effect of this recycling way by partial solvolysis was checked from the mechanical properties of the resulting reinforced PP/PPgma material: Although a lower of Young modulus, better yield stress and especially resilience were observed.