Cellulosic materials as natural fillers in starch-containing matrix-based films: a review

In this work, the different cellulosic materials, namely cellulose and lignin are analyzed. In addition, the starch-containing matrices (isolated starch and flour) reinforced with cellulosic materials to be used in packaging applications are described. Many efforts have been exerted to develop biopackaging based on renewable polymers, since these could reduce the environmental impact caused by petrochemical resources. Special attention has had the starch as macromolecule for forming biodegradable packaging. For these reasons, shall also be subject of this review the effect of each type of cellulosic material on the starch-containing matrix-based thermoplastic materials. In this manner, this review contains a description of films based on starch-containing matrices and biocomposites, and then has a review of cellulosic material-based fillers. In the same way, this review contains an analysis of the works carried out on starch-containing matrices reinforced with cellulose and lignin. Finally, the manufacturing processes of starch/cellulose composites are provided as well as the conclusions and the outlook for future works.Fil: Gutiérrez Carmona, Tomy José. Universidad Central de Venezuela; Venezuela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Alvarez, Vera Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Styrene-assisted maleic anhydride grafted poly(lactic acid) as an effective compatibilizer for wood flour/poly(lactic acid) bio-composites

This study aimed to evaluate the effect of styrene-assisted maleic anhydride-grafted poly(lactic acid) (PLA-g-St/MAH) on the interfacial properties of wood flour/poly(lactic acid) (PLA) bio-composites. PLA-g-St/MAH was synthesized by free-radical melt grafting using styrene as a comonomer and dicumyl peroxide as an initiator. The structure of PLA-g-St/MAH was characterized by Fourier transform infrared spectroscopy. Wood flour/PLA composites were prepared by compression molding using PLA-g-St/MAH as a compatibilizer. The effects of PLA-g-St/MAH on the rheological and mechanical properties, as well as on the fractured surface morphology of the composites were investigated. Results indicated that storage modulus, complex viscosity, equilibrium torque, and shear heat were significantly increased. The mechanical properties of the wood flour/PLA composites were also significantly increased after the addition of PLA-g-St/MAH. The maximum values were achieved at the loading rate of 3 wt % because of the improved interfacial adhesion between the wood flour and the PLA matrix

Composites and foams based on polylactic acid (PLA)

Cette étude est destinée à la production et à la caractérisation des composites d'acide polylactique (PLA) et des fibres naturelles (lin, poudre de bois). Le moussage du PLA et ses composites ont également été étudiés afin d'évaluer les effets des conditions de moulage par injection et du renfort sur les propriétés finales de ces matériaux. Dans la première partie, les composites constitués de PLA et des fibres de lin ont été produits par extrusion suivit par un moulage en injection. L'effet de la variation du taux de charge (15, 25 et 40% en poids) sur les caractéristiques morphologique, mécanique, thermique et rhéologique des composites a été évalué. Dans la deuxième étape, la poudre de bois (WF) a été choisie pour renforcer le PLA. La préparation des composites de PLA et WF a été effectuée comme dans la première partie et une série complète de caractérisations morphologique, mécanique, thermique et l'analyse mécanique dynamique ont été effectués afin d'obtenir une évaluation complète de l'effet du taux de charge (15, 25 et 40% en poids) sur les propriétés du PLA. Finalement, la troisième partie de cette étude porte sur les composites de PLA et de renfort naturel afin de produire des composites moussés. Ces mousses ont été réalisées à l'aide d'un agent moussant exothermique (azodicarbonamide) via le moulage par injection, suite à un mélange du PLA et de fibres naturelles. Dans ce cas, la charge d'injection (quantité de matière injectée dans le moule: 31, 33, 36, 38 et 43% de la capacité de la presse à injection) et la concentration en poudre de bois (15, 25 et 40% en poids) ont été variées. La caractérisation des propriétés mécanique et thermique a été effectuée et les résultats ont démontré que les renforts naturels étudiés (lin et poudre de bois) permettaient d'améliorer les propriétés mécaniques des composites, notamment le module de flexion et la résistance au choc du polymère (PLA). En outre, la formation de la mousse était également efficace pour le PLA vierge et ses composites car les masses volumiques ont été significativement réduites.This study reports on the production and characterization of natural fiber reinforced polylactic acid (PLA) composites. Foaming PLA and its composites was also undertaken to investigate the effect of injection molding conditions (shot size) and natural fiber (flax and wood flour) content on the final properties of the final products. In the first part, PLA was mixed with flax fiber via extrusion and further processed by injection molding to manufacture the final parts. The effect of flax fiber content (15, 25, and 40% wt.) on the morphological, mechanical, thermal, and rheological properties of the composites was evaluated. In the second step, wood flour (WF) was selected to reinforce PLA. Compounding of PLA and WF was carried out in a twin-screw extruder followed by injection molding to obtain the test specimens. A complete series of morphological, mechanical, thermal, and dynamic mechanical analysis was performed to get a complete evaluation of WF addition (15, 25, and 40% wt.) on the properties. Finally, the last step studied PLA composites with natural fibers for the purpose of foaming. Foaming was carried out using an exothermic foaming agent (azodicarbonamide) via injection molding. Injection foaming proceeded after mixing PLA and natural fibers by extrusion. In this case, the shot size (amount of material injected into the mold: 31, 33, 36, 38, and 43% of the machine capacity) and reinforcement content (15, 25, and 40% wt.) were varied. The characterization included mechanical and thermal properties. The results showed that both flax and wood flour led to increased mechanical properties including flexural modulus and impact strength. Moreover, foaming was also effective for neat PLA and PLA composites, i.e. the overall density of the parts was significantly reduced

Recent Advances in Flame Retardant and Mechanical Properties of Polylactic Acid: A Review.

The large-scale application of ecofriendly polymeric materials has become a key focus of scientific research with the trend toward sustainable development. Mechanical properties and fire safety are two critical considerations of biopolymers for large-scale applications. Polylactic acid (PLA) is a flammable, melt-drop carrying, and strong but brittle polymer. Hence, it is essential to achieve both flame retardancy and mechanical enhancement to improve safety and broaden its application. This study reviews the recent research on the flame retardant functionalization and mechanical reinforcement of PLA. It classifies PLA according to the type of the flame retardant strategy employed, such as surface-modified fibers, modified nano/micro fillers, small-molecule and macromolecular flame retardants, flame retardants with fibers or polymers, and chain extension or crosslinking with other flame retardants. The functionalization strategies and main parameters of the modified PLA systems are summarized and analyzed. This study summarizes the latest advances in the fields of flame retardancy and mechanical reinforcement of PLA.pre-print3656 K

Development of antibacterial hemp hurd/poly(lactic acid) biocomposite for food packaging

Contemporary research in food packaging is being progressively focused on the development of biodegradable food packaging from biobased materials for exploring alternatives to traditional, non-biodegradable petroleum based plastics. Consequently, bioplastics are increasingly gaining attention in the food packaging industry because of their potential of biodegradability and versatility in processing. The utilization of bioplastics however is limited because of their inherent shortcomings in thermal and mechanical stability. Recently, bioderived fillers and plant fibres are being extensively used to address the thermo-mechanical stability and to lower the overall material cost in comparison to the baseline bioplastics. Incorporation of biobased fillers and functional nanoparticles to bioplastics not only offers functionality but also enhances the cost-to-performance ratio of the biocomposites. To that end, this study focused on the development of cost effective, biodegradable, and functional food packaging material. Poly(lactic acid) has been used in food packaging to replace conventional petroleum based plastics, because it possesses higher mechanical properties, greater versatility in process selection and it is deemed safe for use in food contact. However, apart from the high cost, a major shortcoming of poly(lactic acid) is a slow crystallization, and hence often requiring an added nucleating agent. The addition of low cost biobased filler to poly(lactic acid) not only lowers the overall material cost but also accelerates crystallization kinetics acting as a nucleating agent. Industrial hemp hurd is explored as a biobased filler with poly(lactic acid) for biocomposites to lower material cost and to address environmental concerns associated with plastic recycling. However, a major concern for the combination of biobased fillers with polymer matrices to produce biocomposites is the weak fibre-matrix interfacial bonding. In recent years, several forms of glycidyl methacrylate-grafted polyolefins have been prepared through reactive extrusion or solution copolymerization to address this issue. The glycidyl methacrylate grafted copolymer is a potential compatibilizing agent for reducing the interfacial incompatibility in biocomposites. Hence, development of functional biocomposites for food packaging with poly(lactic acid) as bioplastic matrix, hemp hurd as biobased filler and glycidyl methacrylate as compatibilizer was the goal of this study. Accordingly, a biocomposite was developed using extrusion and injection moulding utilizing hemp hurd and poly(lactic acid) with properties comparable to poly(lactic acid) with grafting based interfacial compatibilization. Interfacial compatibility between poly(lactic acid) and hemp hurd increased with grafted glycidyl methacrylate in comparison to the noncompatibilized control, as corroborated by scanning electron microscopy fractography. The mechanical properties showed increases in the glycidyl methacrylate-grafted hemp hurd/poly(lactic acid) biocomposite, retaining 94% of the neat polymer strength, with increases in crystallinity at 20% (w/w) loading of hemp hurd. The impact strength data demonstrated that the addition of GMA possesses the potential of improving physical and mechanical properties of HH/PLA composites. The onset of thermal decomposition of the biocomposites obtained through TGA was marginally lower than that of neat PLA. The antibacterial property of hemp hurd is anecdotally reported, but not systematically investigated and reported. In this study, the antibacterial activity of hemp hurd against Escherichia coli was investigated. The antibacterial activity of hemp hurd inhibiting the growth of E. coli was significant. To further increase the antibacterial efficacy of hemp hurd, silver nanoparticles was encapsulated into hemp hurd that exhibited high effectiveness. The silver nanoparticles were synthesized into the hemp hurd using a proprietary method developed in collaboration with Ecofibre Pty Ltd. The inclusion of glycidyl methacrylate further assisted in elastic moduli and strength increase at 10–30 wt. % fraction of silver nanoparticle-loaded hemp hurd in poly(lactic acid), with 20 wt. % hemp hurd-filled biocomposite exhibiting the highest range of properties within the biocomposites investigated. Effective antibacterial activity was achieved with distinct decreases of 85% and 89% in bacterial growth at 0.025 wt. % and 0.05 wt. % loading of silver nanoparticle in the biocomposite. The biocomposites also maintained a safe level of heavy metal migration at 0.20–3.08 mg/kg which meets the European Union (EU) legislation (2002/72/EC), substantially lower than the permitted value of 60 mg/kg. Overall, the properties of these developed biocomposites demonstrated discernible potential in development of food packaging applications. Cost-benefit analysis was performed to assess the viability in commercial manufacturing for producing rigid food packaging. The biocomposite sensitivity and financial analyses provided data on the degree and magnitude of uncertainties related to investment to afford better product design, and establish the potential of PLA-industrial hemp biocomposites for food packaging applications. The findings of this study could create a platform upon which packaging designers, food scientists and engineers could initiate to employ biobased materials in their food packaging solutions

Water absorption of Wood Plastic Composite and Biopolymer reinforced with Switchgrass-fiber Biocomposite Materials

Biocomposites have become widely used materials these days. Due to their light weight and ability to be tailored for specific end uses they have gained a considerable ground in the high performance applications, such as aerospace and automobile industry. However, the use of polymers that can be recycled with carbon and other niche fibers renders the composite non-recyclable. The objective of this present research work was to study the resistance of the Biocomposite and Wood Plastic Composite materials to water. A Biocomposite made up of biopolymer reinforced with switchgrass fibers and a WPC prepared from High density polyethylene reinforced with wood flour fillers were studied for the water absorption behaviour at three different temperatures were evaluated. In addition, density changes, dimensional stability and acoustic properties of the WPC and switchgrss/biopolymer composite were evaluated

Effect of oxidized wood flour as functional filler on the mechanical, thermal and flame-retardant properties of polylactide biocomposites

Based on the biodegradable material-polyethylene glycol (PEG)-as the plasticizer, oxidized wood flour (OWF) as the charring agent for polylactide (PLA), a series flame-retardant PLA biocomposites were prepared via melt-compounding and hot-compression. The effect of OWF on the thermal, mechanical and flame retardant properties of biocomposites was investigated systemically. We have found that after the incorporation of PEG and OWF with 10¿wt% into PLA, the biocomposite showed higher tensile elongation than pure PLA. Furthermore, the presence of OWF and ammonium polyphosphate (APP) imparted the biocomposite good flame-retardant performance, shown a remarkable reduction on the peak of heat release rate (PHRR), improved LOI value and passed UL94 V-0 rating. Moreover, Scanning electron microscopy-energy dispersive spectra (SEM/EDS) and thermogravimetric analysis coupled with infrared spectrometer (TG-FTIR) were also performed to understand the flame retardant mechanism. These results proved that OWF could be as new functional filler for polymer composites to further improve their flame retardancy.Peer ReviewedPostprint (published version

Highly loaded cellulose/poly (butylene succinate) sustainable composites for woody-like advanced materials application

We report the manufacturing and characterization of poly (butylene succinate) (PBS) and micro cellulose (MCC) woody-like composites. These composites can be applied as a sustainable woody-like composite alternative to conventional fossil polymer-based wood-plastic composites (WPC). The PBS/MCC composites were prepared by using a melt blending of 70 wt% of MCC processed from bleached softwood. MCC was modified to enhance dispersion and compatibility by way of carbodiimide (CDI), polyhydroxy amides (PHA), alkyl ester (EST), (3-Aminopropyl) trimethoxysilane (APTMS), maleic acid anhydride (MAH), and polymeric diphenylmethane diisocyanate (PMDI). The addition of filler into PBS led to a 4.5-fold improvement of Young’s modulus E for the MCC composite, in comparison to neat PBS. The 1.6-fold increase of E was obtained for CDI modified composition in comparison to the unmodified MCC composite. At room temperature, the storage modulus E′ was found to improve by almost 4-fold for the APTMS composite. The EST composite showed a pronounced enhancement in viscoelasticity properties due to the introduction of flexible long alkyl chains in comparison to other compositions. The glass transition temperature was directly affected by the composition and its value was −15 °C for PBS, −30 °C for EST, and −10 °C for MAH composites. FTIR indicated the generation of strong bonding between the polymer and cellulose components in the composite. Scanning electron microscopy analysis evidenced the agglomeration of the MCC in the PBS/MCC composites. PMDI, APTMS, and CDI composites were characterized by the uniform dispersion of MCC particles and a decrease of polymer crystallinity. MCC chemical modification induced the enhancement of the thermal stability of MCC composites