Abstract
In this study, ammonium polyphosphate (APP) and aluminum hydroxide (ALH) with different mass contents were used as fire retardants (FRs) on plant-based natural flax fabric-reinforced polymer (FFRP) composites. Thermogravimetric analysis (TGA), limited oxygen index (LOI), and the Underwriters Laboratories (UL)-94 horizontal and vertical tests were carried out for evaluating the effectiveness of these FR treatments. Flat-coupon tensile test was performed to evaluate the effects of FR treatment on the mechanical properties of the FFRP composites. For both fire retardants, the results showed that the temperature of the thermal decomposition and the LOI values of the composites increased as the FR content increases. Under the UL-94 vertical test, the FFRP composites with 20% and 30% APP (i.e., by mass content of epoxy polymer matrix) were self-extinguished within 30 and 10 s following the removal of the flame without any burning drops, respectively. However, the mechanical tensile tests showed that the APP treated FFRP composites reduced their elastic modulus and strength up to 24% and 18%, respectively. Scanning electronic microscopic (SEM) for morphology examination showed an effective coating of the flax fibres with the FRs, which improved the flame retardancy of the treated composites.
Highlights
Plant-based natural fibre-reinforced polymer (NFRP) composites have attracted increased attention as a replacement of synthetic fibre-reinforced polymer composites in various engineering applications.This is because of the biodegradability, low price, energy efficiency, low carbon footprint, and good specific tensile properties of these composites
Compared to the specimen without fire retardants. Their maximum strains increased on average by 60–90%, which was significantly different compared to the specimen without treatment. These results suggested that the addition of aluminium hydroxide (ALH) fire-retardant compounds in the fabric-reinforced polymer (FFRP) composite increased the ductility of the composites
The thermal stability investigations revealed that the composite treatments using the two investigated fire retardants, ammonium polyphosphate (APP) and ALH, led to a substantial increase in
Summary
Plant-based natural fibre-reinforced polymer (NFRP) composites have attracted increased attention as a replacement of synthetic fibre-reinforced polymer composites in various engineering applications. This is because of the biodegradability, low price, energy efficiency, low carbon footprint, and good specific tensile properties of these composites. Specific mechanical properties (e.g., specific tensile strength and specific tensile modulus of flax fibres) are comparable to those of synthetic E-glass fibre [1] This comparison is, somewhat misleading, since the natural fibres are not endless (compared to glass or carbon fibers) but are used in the form of yarns, which will generally have lower mechanical properties compared to the ones of individual fibres. It is estimated that the market of Polymers 2019, 11, 699; doi:10.3390/polym11040699 www.mdpi.com/journal/polymers
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