Abstract
Low viscosity, potentially renewable aliphatic epoxy resins, appropriate for processing with injection techniques were flame retarded with the use of resorcinol bis(diphenyl phosphate) (RDP), acting predominantly in the gas phase, ammonium polyphosphate (APP), acting in the solid phase, and their combination. Samples of gradually increasing phosphorus (P) content (1%, 2%, 3%, 4%, and 5%) and mixed formulations with 2% P from APP and 2% P from RDP were prepared. The fire retardancy of matrix and carbon fibre reinforced samples was examined by limiting oxygen index (LOI), UL-94 tests, and mass loss calorimetry. The thermal stability of the matrices was investigated by thermogravimetric analysis, whereas the effect of flame retardants (FRs) on the crosslinking process and glass transition temperature was evaluated by differential scanning calorimetry in matrices and by dynamic mechanical analysis in composites. According to the results, although the trifunctional glycerol -based (GER) and the tetrafunctional pentaerythritol-based (PER) epoxy resins have a similar initial LOI and horizontal burning rate, GER has an approximately 1.5 times higher peak of heat release rate (pHRR) than PER. At least 4% P content is necessary to reach a reasonable improvement in fire performance in these resin transfer molding (RTM)-compatible systems and with the same FR-content PER reaches better fire performance. RDP has an early gas phase effect at the beginning of degradation, while later on the solid phase action of APP prevails, although in composites hindered by the reinforcing carbon fibres. In PER composites, the combination of APP and RDP had a synergistic effect, leading to a pHRR of 218 kW/m2 and total heat release of 18.2 MJ/m2.
Highlights
Carbon fibre reinforced polymer composites, which are capable of replacing metallic structures, are emerging in several high-tech sectors due to their excellent mechanical properties
The solid-phase action of ammonium polyphosphate (APP) was hindered by the of 13 reinforcing carbon fibres, but the differences between the flame retarded samples are minor.10Among the flame retarded PER composites, PER 4% P resorcinol bis(diphenyl phosphate) (RDP) ignited earliest (it is assumed again that the gas the flame retarded PER composites, PER 4% P RDP ignited earliest, leading to a reduced peak of heat release rate (pHRR) in comparison to the phase action starts in the early phase of degradation), leading to a reduced pHRR in comparison to composite
We investigated the fire retardancy of a low viscosity glycerol- (GER) and a pentaerythritol (PER)-based epoxy resin (EP) and their carbon fibre reinforced composites applying ammonium polyphosphate (APP), acting in the solid phase, resorcinol bis(diphenyl phosphate) (RDP), acting predominantly in the gas phase, and their combination
Summary
Carbon fibre reinforced polymer composites, which are capable of replacing metallic structures, are emerging in several high-tech sectors due to their excellent mechanical properties. Polymers 2018, 10, 1081 viscosity of the polymer matrix, which is a key property during the production of composites by injection technologies such as resin transfer molding (RTM) commonly used in high-tech industries [6]. The reinforcement can filter out the solid phase flame retardants during the injection of the matrix, which may lead to non-uniform particle distribution [7,8], and to uneven fire performance. The thermal stability of the matrices was investigated by thermogravimetric analysis, whereas the effect of FRs on the crosslinking process and glass transition temperature was evaluated by differential scanning calorimetry in matrices and by dynamic mechanical analysis in composites
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