Effects of Water and Chemical Solutions Ageing on the Physical, Mechanical, Thermal and Flammability Properties of Natural Fibre-Reinforced Thermoplastic Composites

Abstract

Biocomposites comprising a combination of natural fibres and bio-based polymers are good alternatives to those produced from synthetic components in terms of sustainability and environmental issues. However, it is well known that water or aqueous chemical solutions affect natural polymers/fibres more than the respective synthetic components. In this study the effects of water, salt water, acidic and alkali solutions ageing on water uptake, mechanical properties and flammability of natural fibre-reinforced polypropylene (PP) and poly(lactic acid) (PLA) composites were compared. Jute, sisal and wool fibre- reinforced PP and PLA composites were prepared using a novel, patented nonwoven technology followed by the hot press method. The prepared composites were aged in water and chemical solutions for up to 3 week periods. Water absorption, flexural properties and the thermal and flammability performances of the composites were investigated before and after ageing each process. The effect of post-ageing drying on the retention of mechanical and flammability properties has also been studied. A linear relationship between irreversible flexural modulus reduction and water adsorption/desorption was observed. The aqueous chemical solutions caused further but minor effects in terms of moisture sorption and flexural modulus changes. PLA composites were affected more than the respective PP composites, because of their hydrolytic sensitivity. From thermal analytical results, these changes in PP composites could be attributed to ageing effects on fibres, whereas in PLA composite changes related to both those of fibres present and of the polymer. Ageing however, had no adverse effect on the flammability of the composites.

Effect of Eco-Friendly Peanut Shell Powder on the Chemical Resistance, Physical, Thermal, and Thermomechanical Properties of Unsaturated Polyester Resin Composites

“…The most common natural filler is wood fiber or flour, which is a waste product in the production of paper [13][14][15]. However, waste rice husks, nut shells, stalks of hemp, sisal, jute, or corn cobs are being used more often [16][17][18]. These natural ingredients reduce the polymer product costs, and on the other hand, they are characterized by good reinforcing properties and biodegradability.…”

Effect of Hydrothermal Aging on Damping Properties in Sisal Mat-Reinforced Polyester Composites

“…Inside the fibers, water penetrates via microcapillary transition chains within the cell wall, thus causing swelling, which alters the dimensional stability [ 28 ]. Kandola et al report that capillary water can be absorbed if the fiber structure is swollen, and the relative humidity is close to 100% [ 29 ].…”

Moisture Absorption Effects on the Mechanical Properties of Sandwich Biocomposites with Cork Core and Flax/PLA Face Sheets

“…This behaviour could be attributed to higher moisture absorption by sample C, creating a weak fibre matrix interface as a result, reducing the tensile properties. The paper layer present in sample C is sensitive to moisture absorption, which, in turn, affects its properties and initiates delamination when subjected to tensile tests [ 38 ].…”