Natural fibers, as replacement of engineered fibers, have been one of the most researched topics over the past years. This is due to their inherent properties, such as biodegradability, renewability and their abundant availability when compared to synthetic fibers. Synthetic fibers derived from finite resources (fossil fuels) and are thus, affected mainly by volatility oil prices and their accumulation in the environment and/or landfill sites as main drawbacks their mechanical properties and thermal properties surpass that of natural fibers. A combination of these fibers/fillers, as reinforcement of various polymeric materials, offers new opportunities to produce multifunctional materials and structures for advanced applications. This article intends to cover recent developments from 2013-up to date on hybrid composites, based on natural fibers with other fillers. Hybrid composites preparation and characterization towards their applicability in advanced applications and the current challenges are also presented.

Recent progress on natural fiber hybrid composites for advanced applications: A review

Biocomposites were manufactured with biochar and polypropylene at five loading levels (0, 15, 25, 30, and 35 wt%) by compounding and injection moulding. Biocomposites were tested by tension, bending, cone calorimeter, thermogravimetry, differential scanning calorimetry, X–ray diffraction, and infrared spectroscopy. Incorporation of increasing amount of biochar to neat polypropylene continuously improved its tensile modulus and flexural strength/modulus. The peak heat release rate and smoke production of the biocomposites were significantly reduced as a result of biochar addition. The high surface area of biochar allowed polypropylene to flow in creating a mechanical interlocking and improving the mechanical properties. The thermally stable biochar provided a compact char structure during combustion which prevented the heat and mass transfer between the polypropylene and the ambient O2. Thermal stability of polypropylene was increased as a result of biochar inclusion, as observed in thermogravimetry.

Mechanical and flammability characterisations of biochar/polypropylene biocomposites

A review of flammability of natural fibre reinforced polymeric composites

Various compositions of epoxy/hardener with flame retardant (FR) as additives were used to produce natural fiber composite through the resin infusion technique. The effects of natural fiber (NF), ammonium polyphosphate (APP), alumina trihydrate (ATH) and ATH/APP hybrid on flammability, thermal and mechanical properties of the composites were investigated. Incorporation of NF into neat epoxy matrix reduced the gross heat of combustion with improved thermal degradation properties. Addition of APP enhanced the flame resistant properties of the composite with a much reduced total flame time and zero drip. The 10 wt·% ATH and 5 wt·% APP hybrid showed the most promising flame retardancy with a self-extinguishing property as well as the lowest gross heat and greatest char residue amongst the various formulations investigated. In general, the formulations containing only ATH couldn't provide the effective flame resistivity as compared to that of the APP-filled composites. The ATH-filled formulations reduced the tensile strength, elongation at break and flexural properties while an increase in the flexural strength of APP-loaded formulations was observed. An increase in moduli of the FR-filled composites was measured as compared to that of the NF/epoxy composite, owing to a more brittle characteristic.

Synergistic of ammonium polyphosphate and alumina trihydrate as fire retardants for natural fiber reinforced epoxy composite

Biocomposite of wood flour (WF)/polypropylene (PP) composite (WPC) is not easily flame-retarded because of the different flame retardant mechanisms of PP and WF. In order to improve the flame retardancy of WPC, a single flame retardant of ammonium polyphosphate (APP) modified via ion exchange reaction with ethanolamine, which is named as ETA-APP, was used to prepare flame-retardant WPC. The flammability was investigated by limiting oxygen index (LOI), UL-94 vertical burning test, and cone calorimeter. The results show the flame retardant properties of the flame-retardant WPC are improved greatly. The limiting oxygen index is 43.0%, which is increased by 71.6% compared with that of WPC with the same content of APP. And the vertical burning test can pass UL-94 V-0 rating. The results of cone calorimeter test show that the heat release rate (HRR) and total heat release (THR) of the WPC with ETA-APP are decreased in comparison with WPC/APP. The flame-retardant mechanism of WPC/ETA-APP system was investigated ...

An Effective Way To Flame-Retard Biocomposite with Ethanolamine Modified Ammonium Polyphosphate and Its Flame Retardant Mechanisms

Improvement on fire retardancy of wood flour/polypropylene composites using various fire retardants

Synergy effects of wood flour and fire retardants in flammability of wood-plastic composites

Addition of wood flour improve the mechanical properties of thermoplastics, on the other hand it increases the burning speed of the materials. To modify the flammability of wood-plastic composites(WPC), various fire retardants, such as ammonium polysphosphate (APP), melamine polyphosphate (MPP) and aluminum hydroxide were added to WPCs. Burning tests based on UL94 and cone calorimetry were conducted to evaluate a fire performance of WPCs with fire retardants. The addition of fire retardants could lead to self-extinguishing materials when 10 wt% of APP was used. However, in the case of pure polypropylene, addition of 10 wt% of APP did not improve the flammability. Wood flour accelerates the burning behavior of PP, but it can reduce the use of APP to achieve self-extinguishing materials. Synergy effects between wood flour and APP was confirmed. Wood flour facilitates the forming of foamed char layer by APP during the combustion. This protective char surface can reduce the heat and oxygen diffusion toward the WPCs. The effect of fire retardants of mechanical properties of WPCs was also investigated. Tensile strength and modulus of composites decreased with addition of fire retardants. © 2014 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of COE of Sustainalble Energy System, Rajamangala University of Technology Thanyaburi (RMUTT).

11th Eco-Energy and Materials Science and Engineering (11th EMSES) Synergy effects of wood flour and fire retardants in flammability of wood-plastic composites

Yuta Tomita

Papers

Improvement on fire retardancy of wood flour/polypropylene composites using various fire retardants

Synergy effects of wood flour and fire retardants in flammability of wood-plastic composites

11th Eco-Energy and Materials Science and Engineering (11th EMSES) Synergy effects of wood flour and fire retardants in flammability of wood-plastic composites