Natural fiber reinforced polymer composites

The use of natural fibers as a reinforcement for various materials was recorded already in ancient Egypt; however, their rediscovery can be dated to the beginning of 20th century. Currentspecial issueisdevoted to theroleofnatural fibersas reinforcements for various biodegradable and nonbiodegradable polymer matrices. The application of natural fillers can be seen as an approach to adjust material performance of polymer composites supposing that filler/matrix interactions will be optimized and a hygroscopicity of natural fillers will be hindered. This special issue contains 16 papers that highlight a number of reasons for applications of natural fillers in polymer composites. In recent years the discussion about a balance in carbon footprint increased an attractiveness of natural fibers/fillers derived from agricultural sources predominantly from one-year plants

Influence of FFF Process Conditions on the Thermal, Mechanical, and Rheological Properties of Poly(hydroxybutyrate-co-hydroxy Hexanoate)

Polyhydroxyalkanoates are natural polyesters synthesized by microorganisms and bacteria. Due to their properties, they have been proposed as substitutes for petroleum derivatives. This work studies how the printing conditions employed in fuse filament fabrication (FFF) affect the properties of poly(hydroxybutyrate-co-hydroxy hexanoate) or PHBH. Firstly, rheological results predicted the printability of PHBH, which was successfully realized. Unlike what usually happens in FFF manufacturing or several semi-crystalline polymers, it was observed that the crystallization of PHBH occurs isothermally after deposition on the bed and not during the non-isothermal cooling stage, according to calorimetric measurements. A computational simulation of the temperature profile during the printing process was conducted to confirm this behavior, and the results support this hypothesis. Through the analysis of mechanical properties, it was shown that the nozzle and bed temperature increase improved the mechanical properties, reducing the void formation and improving interlayer adhesion, as shown by SEM. Intermediate printing velocities produced the best mechanical properties.This work has received funding from the Basque Government through grant IT1503-22, the Gipuzkoa Provincial Council (Red I+D+i 2022-CIEN-000022-01), and the project National Centre of Competence in Polymer Materials and Technologies for the 21st Century no. TN02000051 (TA CR, Czech Republic)

Designing packaging materials with viscoelastic and gas barrier properties by optimized processing of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with lignin

Microbial poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) bio-polyester was combined by thermoforming with Kraft lignin in order to design new advanced composite materials for packaging purpose. After assessing the compatibility of the two raw materials, the thermoformed composite sheets were investigated in order to assess the impact of the lignin fraction (between 0 and 10 wt.%) on melting and crystallization, behavior, thermo-oxidative stability, mechanical and viscoelastic properties, and permeability for oxygen and carbon dioxide. It turned out that the applied Kraft lignin is highly compatible with microbial PHBHV, and by exerting a reinforcing effect, acts as an active additive. As aspired, the gas permeability was decreased by combining PHBHV with 1 wt.% lignin; here, a reduction of permeability for oxygen by 77% and by 91% for carbon dioxide, respectively, was observed if compared to the native bio-polyester specimens. Also the low thermo-oxidation stability, a typical characteristic of pure PHBHV, was increased for the lignin-containing materials. This first report on thermoformed composite materials of microbial PHBHV and lignin suggests a new class of bio-based polymer materials to be applied for packaging of various easily perishable goods. (C) 2015 Elsevier B.V. All rights reserved.Operational Programme 'Research and Development for Innovations'; European Regional Development Fund (ERDF); national budget of the Czech Republic, within the project 'Centre of Polymer Systems' [CZ.1.05/2.1.00/03.0111

Reinforcement of poly(lactic acid) with spray-dried lignocellulosic material

Effects of the addition of spray-dried lignocellulosic material in polylactic acid ( PLA) were evaluated in this work. The lignocellulosic material was produced by spray-drying unbleached fibrous material provided by a paper mill. Beforehand, this material was made hydrophobic in the sizing step of the papermaking process. We propose that size present on the lignocellulose powder may act as a potential alternative to commonly-used coupling agents in the compounding of cellulosic filler with PLA. The lignocellulose powder was compounded with PLA in various amounts by extrusion and injection-moulding. Homogeneous dispersion of the lignocellulose powder in PLA was achieved. However, comprehensive mechanical and microscopic characterisation revealed only minor positive effects of the filler on PLA in a limited number of cases. Further investigation by gel permeation chromatography ( GPC) showed a reduction of the average molar mass of the PLA matrix with increasing filler content, partly due to the residual inorganic matter in the spray-dried powder. This effect overshadowed the homogeneous dispersion and resulted in composites with weaker mechanical properties in most cases.Austrian Research Promotion Agency FFG [836650]; European Regional Development Fund (ERDF) Upper Austria, project Biorest [IWB 2014-2020]; Ministry of Education, Youth and Sports of the Czech Republic within the NPU I program [LO1504

Anti-hydrolysis effect of aromatic carbodiimide in poly(lactic acid)/wood flour composites

Poly(lactic acid) (PLA) filled with wood flour (WF) is more susceptible to hydrolysis compared to pure PLA. This work shows that the hydrolysis reactions leading to chain scission can be hindered by using 2 wt% of bis(2,6-diisopropylphenyl)carbodiimide (ZIKA). It was found that the addition of ZIKA supports the crosslinking of PLA/WF composite. The crosslinking slightly hindered the annealing efficiency of wood flour and increased the stiffness of biocomposites. The thermal stability of biocomposites containing ZIKA was slightly improved. The relevance of the antihydrolysis effect of ZIKA during melt processing of biocomposites was correlated with the rheological and molar mass properties. The hydrolytic stability of biocomposites was determined under buffer solution conditions at accelerated temperature 80 °C and pH of 7. The determined lower depolymerisation and hydrolysis rates of PLA/WF-ZIKA composites indicate that the service lifespan of biocomposites can be prolonged by the addition of ZIKA additive. © 2017 Elsevier LtdERDF, European Regional Development Fund; ERDF, European Regional Development Fund; 17-16928Y, GACR, Grantová Agentura České Republiky; LO1211, MŠMT, Ministerstvo Školství, Mládeže a Tělovýchovy; LO1504, MŠMT, Ministerstvo Školství, Mládeže a TělovýchovyEuropean Regional Development Fund (EFRE); province of Upper Austria through program IWB - Upper Austria [project BioRest]; Ministry of Education, Youth and Sport of the Czech Republic (MEYS) through the project "Materials Research Centre - Sustain ability and Development" [LO1211]; Czech Science Foundation (GACR) [17-16928Y]; Ministry of Education, Youth and Sports of the Czech Republic (MEYS) [LO1504]; Research & Development Operational Programme – ERD

Reinforcement of Poly (Lactic Acid) with Spray-dried Lignocellulosic Material

Effects of the addition of spray-dried lignocellulosic material in polylactic acid (PLA) were evaluated in this work. The lignocellulosic material was produced by spray-drying unbleached fibrous material provided by a paper mill. Beforehand, this material was made hydrophobic in the sizing step of the papermaking process. We propose that size present on the lignocellulose powder may act as a potential alternative to commonly-used coupling agents in the compounding of cellulosic filler with PLA. The lignocellulose powder was compounded with PLA in various amounts by extrusion and injection-moulding. Homogeneous dispersion of the lignocellulose powder in PLA was achieved. However, comprehensive mechanical and microscopic characterisation revealed only minor positive effects of the filler on PLA in a limited number of cases. Further investigation by gel permeation chromatography (GPC) showed a reduction of the average molar mass of the PLA matrix with increasing filler content, partly due to the residual inorganic matter in the spray-dried powder. This effect overshadowed the homogeneous dispersion and resulted in composites with weaker mechanical properties in most cases

Copolymer of natural fibre reinforced polyester urethane: effect on physico-chemical properties through modification to interfacial adhesion

This work is dedicated to polyester urethane (PEU)-based biocomposites, with special focus placed on techniques for compatibilisation to heighten interfacial adhesion between the PEU matrix and flax fibres. Tests were conducted on the effects of modification so as to increase interfacial adhesion between the flax fibres and the polyester matrix. These tests involved a commercial silane-based compatibilising additive, two experimentally synthesised agents, oleic acid (OA) and di-tert-butyl peroxide (DTBP). Furthermore, the flax fibres underwent acid or alkali treatment. The biocomposites were characterised by gel permeation chromatography, infrared spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Mechanical properties were investigated through tensile testing. Biocomposites with a commercial silane-based additive and synthesised agent, based on maleic-anhydride, were assessed as the best solution. Nevertheless, all modifications, excluding alkali treatment of fibres, significantly increased the performance of the material.Ministry of Education, Youth and Sports of the Czech Republic - Program NPU I [LO1504]; program EUPRO [LE12002]; program Mobility [7AMB13AT024]; Internal Grant Agency of Tomas Bata University in Zlin [IGA/CPS/2015/003]; Austrian Agency for International Cooperation in Education and Research (OeAD - GmbH) [CZ 06/2013

Nucleating efficiency and thermal stability of industrial non-purified lignins and ultrafine talc in poly(lactic acid) (PLA)

Poly(lactic acid) (PLA) with D – lactide content of 1.2 wt% has been modified by melt mixing with 3 wt% of lignin (Kraft or Organosolv). Gel permeation chromatography and thermogravimetric analysis were employed to determine the thermal stability of PLA and nucleated PLA compounds during melt blending. The nucleating efficiency of industrial lignins was compared with the nucleation efficiency of ultrafine talc (UT). The feasibility of using industrial lignins and UT as nucleating agents for PLA was investigated by polarized light optical microscopy and differential scanning calorimetry, through non-isothermal and isothermal crystallization, whereas their structure was studied through in-situ synchrotron X-ray diffraction at wide and small angles. Both lignins, as well as UT induced heterogeneous nucleation and their nucleating action in PLA increased the crystallization rate and shortened the overall crystallization half time for isothermal crystallization. All tested nucleating agents increased the degree of crystallinity of PLA. The nucleation efficiency of Kraft and Organosolv lignin and ultrafine talc was 31%, 27%, and 80%, respectively. It was found that the thermal processing window of PLA was not influenced by the addition of lignins or ultrafine talc. © 2017 Elsevier LtdIWB 2014-2020, ERDF, European Regional Development Fund; LO1504, MŠMT, Ministerstvo Školství, Mládeže a TělovýchovyEuropean Regional Development Fund (EFRE); province of Upper Austria through program IWB Upper Austria; Ministry of Education, Youth and Sports of the Czech Republic [LO1504]; POLYMAT Basque Center for Macromolecular Design and Engineering; ALBA synchrotron facility [2016091863

Characterization of polyhydroxyalkanoates produced by Synechocystis salina from digestate supernatant

The current commercial production of polyhydroxyalkanoates (PHA) is based on heterotrophic bacteria, using organic carbon sources from crops. To avoid the competition with food and feed production, cyanobacteria, metabolising PHA from carbon dioxide can be used. This research focuses on the investigation of the thermal and rheological properties of PHA polymers accumulated by Synechocystis salina, which had been cultivated in digestate supernatant and a mineral medium. The dried bacterial cells had a polymer content of 5.5-6.6%. The relevance of the derived PHA polymers for the common melt polymer processing was correlated with their molecular mass distribution as well as with their thermal and rheological properties. The determined thermal and rheological properties showed that PHA polymers accumulated by S. salina on digestate supernatant or mineral medium are comparable with the commercial available poly(3-hydroxybutyrate). However, the results showed that PHA polymers in general require modification before melt processing to increase their stability in the molten state. © 2017 Elsevier B.V.Austrian Climate and Energy Funds (Austrian Research Promotion Agency) [834422]; EVN AG; ANDRITZ AG; European Regional Development Fund (ERDF) through the program IWB Upper Austria; project Biorest; Ministry of Education, Youth and Sports of the Czech Republic within the NPU I program [LO1504