Mechanical properties for bio-based thermoset composites made from lactic acid, glycerol and viscose fibers

Abstract

Regenerated cellulose fibers were used to produce thermoset composites from a bio-based thermoset resin synthesized from lactic acid and glycerol. The resin was impregnated into the regenerated cellulose fiber and compression molded at elevated temperature to produce thermoset composites. Different fiber alignments (unidirectional and bidirectional), different reinforcement type (warpknitted and non-woven) and varying fiber loading (65, 70 and 75 wt%) were investigated. The composites were characterized by flexural, tensile and Charpy impact testing and by dynamical mechanical thermal analysis. Water uptake and ageing properties in climate chamber were also characterized for the composites. The results showed that the composites had good mechanical properties. They can be produced with up to 70 wt% fiber content when using unidirectional (UD) and bidirectional fiber (BD) alignment, and with up to 65 wt% fiber content when using the non-woven (NW) reinforcement. The tensile modulus ranged between 11 and 14 GPa for UD composites, 7 and 8.5 GPa for BD composites and 5 and 7.5 GPa for NW composites. The flexural modulus ranged between 10 and 11.5 GPa for UD composites, 5 and 6.5 GPa for BD composites and 5 and 6 GPa for NW composites. The impact strength ranged between 130 and 150 kJ/m 2 for UD composites, 98 and 110 kJ/m 2 for BD composites and 17 and 20 kJ/m 2 for NW composites. The result of the ageing test showed that the mechanical properties of the composites deteriorate with ageing but the addition of styrene somewhat counteracts the degradation, making the composite applicable for indoor use.

Performance of biocomposites from surface modified regenerated cellulose fibers and lactic acid thermoset bioresin

“…Our former study showed that soybean oil based thermoset nonwoven fiber composites had tensile strength between 70 and 100 MPa at 40-60 wt% fiber loading (Ramamoorthy et al 2012(Ramamoorthy et al , 2013. Tensile modulus of the composites was between 6 and 10 GPa while the Cellulose maximum elongation was about 2.1 %, which follow the results from our earlier studies (Ramamoorthy et al 2012(Ramamoorthy et al , 2013Esmaeili et al 2014). Further, acoustic emissions could be used to analyze microstructural damage analysis (Bravo et al 2015).…”

“…The glass transition temperature of the composites was over 100°C; higher than that of the neat resin. T g increase on addition of cellulosic fibers was due to restricted mobility of the polymer chains in the interphase and was observed previously by several authors (Å kesson et al 2011;Esmaeili et al 2014).…”

“…The flexural strength and modulus of untreated fiber reinforced composites were 116 MPa and 5 GPa respectively which can be compared to the results from previous studies (Ramamoorthy et al 2013;Esmaeili et al 2014). On silane treatment, there was insignificant increase in flexural strength but the modulus increased by 24 %.…”

“…Similar results were obtained when using cellulose fibers in a thermoplastic polymer as reinforcement (Bledzki et al 2009;Oksman et al 2003), and when using a lactic acid based thermoset resin, which was impregnated in a nonwoven natural fiber mat (Å kesson et al 2009). Our prior studies showed that the impact strength increased on changing the alignment of fibers (Ramamoorthy et al 2012;Esmaeili et al 2014).…”

End-Of-Life Textiles as Reinforcements in Biocomposites

“…Similar results were noticed in cellulose based composites, and the tensile properties decreased due to brittleness of thermoset matrix [9,17]. Modulus could suggest the toughness of the composites; high moduli of polymer composites in many cases indicate less tough materials [11,18]. Toughness of the composites is discussed with impact properties.…”