Investigation of injection moulded poly(lactic acid) reinforced with long basalt fibres

Abstract

In this paper long basalt fibre reinforced Poly(Lactic Acid) (PLA) composites were prepared and analysed. Continuous basalt roving was coated with PLA by using continuous extrusion coating technology and a special die. The continuous basalt roving coated with PLA was cut into 10 mm long pellets, which were injection moulded. The properties of the long fibre reinforced composites were compared to chopped (short) basalt fibre reinforced PLA composites produced by using the conventional dry mixing, extrusion and injection moulding method. The mechanical properties of the long basalt fibre reinforced PLA was found to be superior to short basalt fibre reinforced PLA. Fibre length analysis revealed that the remaining average fibre length highly increased, while electron microscopy demonstrated that there is very strong adhesion between the phases. Finally it was found that the long basalt fibres also have nucleating ability, however, not as efficient as short basalt fibres. 2 KeywordsMechanical properties (B), injection moulding (E), extrusion (E), Long basalt fibre composite (nominated new keyword) IntroductionIn the last decades renewable resource based and inherently biodegradable polymers got into the focus of interest and research, because it is believed that due to their exceptional properties, these polymers will replace some of the petrol based ones used nowadays [1,2]. These exceptional properties are that they can be fully synthesized from renewable resources and they can also be degraded biologically in compost conditions into water, carbon-dioxide and humus, which latter can be used for nutrition of the next generation of plants for renewable resource and thus biodegradable polymer production. According to these features the life cycle of biodegradable polymers can be fit into the life cycle of nature, so they can ensure sustainability in polymer recycling.By the fermentation of starch and sugar received both from renewable resources, lactic acid can be produced, which can be further processed by using ring opening polymerisation of the dimer of lactic acid called lactide into the promising biodegradable polymer currently, Poly(Lactic Acid) (PLA) [3]. PLA has good mechanical properties, high strength and stiffness; however, it is considered as a brittle polymer with a strain at break around 3-5% and a notched and unnotched Charpy impact strength of around 3 and 23 kJ/m 2 respectively. Moreover, the very slow crystallisation of PLA [4][5][6][7][8] prevents it to be used in high temperature applications due its low glass transition temperature (Tg) around 50-55°C. Since PLA is a thermoplastic polymer, it can be processed by using conventional plastic processing equipments like injection moulding, extrusion, thermoforming, blow, sheet, or compression moulding [9] into products like cutleries, cups, flower pots, food containers, films, toothbrush handles or biomedical implants [10].Although the high strength and stiffness of PLA suggest it to be used in engineering applications, nowadays most PLA produ...

Biocomposites based on poly(lactic acid)/willow-fiber and their injection moulded microcellular foams

“…The glass transition temperature (T g ), cold crystallization peak temperature (T cc ), melting temperature (T m ), and enthalpy of melting (!H m ), were analyzed for all the samples using Universal Analysis software from TA Instruments. Percentage crystallinities of all the samples were calculated using Equation (4): where X c is the crystallinity [%], !H m the heat of melting, !H cc the heat of cold crystallization, !H m°h eat of melting of 100% crystalline PLA samples (considered as !H m°= 93 J/g), and W f the PLA weight fraction in the composite [11,12]. From the DSC cold crystallization peak, slope of the peak (S p ) (at lower temperature side) as a measure of rate of crystallization and peak width at a half height (!W d ) as a measure of crystallite size distribution were also calculated.…”

Filling behavior, morphology evolution and crystallization behavior of microinjection molded poly(lactic acid)/hydroxyapatite nanocomposites

“…In the contemporary society, the biodegradable polymer materials [7][8][9], including natural polymer based materials (such as natural cellulose fibers [10][11][12][13][14], lignin [15], starch [16] and protein [17]) and synthetic polymers (such as poly(lactic acid) (PLA), polyhydroxyalkanoate (PHA) and poly(butylene succinate) (PBS)) [18][19][20][21], are attracting the increasing attention of both academic world and industrial world due to their benign properties such as biodegradability, environmental friendliness and acceptable physical-mechanical performance. Among the synthetic biodegradable polymer materials, poly(lactic acid) (PLA) could be believed as the most famous one.…”

Creep behaviour of injection-moulded basalt fibre reinforced poly(lactic acid) composites

“…The strong adhesion was demonstrated by electron microscopy by observing excellent wetting of the fibres. Recently, in our other publication, 27 long basalt fibre reinforced injection moulded PLA composites were prepared by first producing a pre-product of basalt roving extrusion coated with PLA and followed by injection moulding of this pre-product. It was found that the average fibre length within the final composites increased from 159 μm ("classical" extrusion compounding followed by injection moulding) to 658 μm by applying this long fibre injection moulding technology.…”

“…By simply melting the basalt rocks, short or continuous basalt fibres can be made by using the spinneret or the Junkers technology respectively. 22 Although basalt seems to be a good alternative to plant fibres, there are only a limited number of publications in the literature of basalt fibre reinforced PLA based composites [23][24][25][26][27] or basalt fibre reinforced other biodegradable matrix composites like starch 28 or gluten. 29 Xi et al 23 produced PLA based scaffolds for hard tissue repair with basalt fibre reinforcement.…”