Bacterial Cellulose Network from Kombucha Fermentation Impregnated with Emulsion-Polymerized Poly(methyl methacrylate) to Form Nanocomposite

The use of bio-based residues is one of the key indicators towards sustainable development goals. In this work, bacterial cellulose, a residue from the fermentation of kombucha tea, was tested as a reinforcing nanofiber network in an emulsion-polymerized poly(methyl methacrylate) (PMMA) matrix. The use of the nanofiber network is facilitating the formation of nanocomposites with well-dispersed nanofibers without using organic solvents or expensive methodologies. Moreover, the bacterial cellulose network structure can serve as a template for the emulsion polymerization of PMMA. The morphology, size, crystallinity, water uptake, and mechanical properties of the kombucha bacterial cellulose (KBC) network were studied. The results showed that KBC nanofibril diameters were ranging between 20-40 nm and the KBC was highly crystalline, >90%. The 3D network was lightweight and porous material, having a density of only 0.014 g/cm(3). Furthermore, the compressed KBC network had very good mechanical properties, the E-modulus was 8 GPa, and the tensile strength was 172 MPa. The prepared nanocomposites with a KBC concentration of 8 wt.% were translucent with uniform structure confirmed with scanning electron microscopy study, and furthermore, the KBC network was homogeneously impregnated with the PMMA matrix. The mechanical testing of the nanocomposite showed high stiffness compared to the neat PMMA. A simple simulation of the tensile strength was used to understand the limited strain and strength given by the bacterial cellulose network. The excellent properties of the final material demonstrate the capability of a residue of kombucha fermentation as an excellent nanofiber template for use in polymer nanocomposites

Feasibility of Barley Straw Fibers as Reinforcement in Fully Biobased Polyethylene Composites: Macro and Micro Mechanics of the Flexural Strength

Awareness on deforestation, forest degradation, and its impact on biodiversity and global warming, is giving rise to the use of alternative fiber sources in replacement of wood feedstock for some applications such as composite materials and energy production. In this category, barley straw is an important agricultural crop, due to its abundance and availability. In the current investigation, the residue was submitted to thermomechanical process for fiber extraction and individualization. The high content of holocellulose combined with their relatively high aspect ratio inspires the potential use of these fibers as reinforcement in plastic composites. Therefore, fully biobased composites were fabricated using barley fibers and a biobased polyethylene (BioPE) as polymer matrix. BioPE is completely biobased and 100% recyclable. As for material performance, the flexural properties of the materials were studied. A good dispersion of the reinforcement inside the plastic was achieved contributing to the elevate increments in the flexural strength. At a 45 wt.% of reinforcement, an increment in the flexural strength of about 147% was attained. The mean contribution of the fibers to the flexural strength was assessed by means of a fiber flexural strength factor, reaching a value of 91.4. The micromechanical analysis allowed the prediction of the intrinsic flexural strength of the fibers, arriving up to around 700 MPa, and coupling factors between 0.18 and 0.19, which are in line with other natural fiber composites. Overall, the investigation brightness on the potential use of barley straw residues as reinforcement in fully biobased polymer composites

Macro and micro-mechanics behavior of stifness in alkaline treated hemp core fibres polypropylene-based composites

[EN] Traditionally, glass fibre has been used as plastic reinforcement whenever mechanical properties of a matrix, like stiffness, do not meet the specifications. However, current tendencies try to replace glass fibres by more sustainable fibres to obtain eco-friendlier products. Natural fibres show comparatively good physical and mechanical properties and, unlike glass fibres, come from renewable resources and are recyclable and sustainable. In this work, hemp straw discarded from hemp manufacturing was used as reinforcement in polypropylene composites. One drawback associated to hemp straw is its high lignin content that reduces its reinforcing potential. Therefore, a soft alkaline treatment was employed to adjust the lignin contents. In this work, the evolution of the Young's modulus with the NaOH treatment is assessed and discussed. Intrinsic Young's moduli of hemp straw fibres at different alkaline conditions were determined by Hirsch model. Finally, Tsai-Pagano and Halpin-Tsai equations allowed the prediction of the theoretical Young's modulus of the composites. The results showed the competitiveness of a by-product reinforced composite in front of commodity materials.Vilaseca, F.; Rey Tormos, RMD.; Serrat, R.; Alba Fernández, J.; Mutje, P.; Espinach, FX. (2018). Macro and micro-mechanics behavior of stifness in alkaline treated hemp core fibres polypropylene-based composites. Composites Part B Engineering. 144:118-125. doi:10.1016/j.compositesb.2018.02.029S11812514

Effect of NaOH treatment on the flexural modulus of hemp core reinforced composites and on the intrinsic flexural moduli of the fibers

This paper describes the potential of using hemp core waste in the composite industry. These lignocellulosic residues can be used to produce environmentally friendly and economically viable composites and improve the overall value chain of hemp production. To this purpose, hemp core residues were alkaline treated at different NaOH concentrations and then mechanically defibrated. Hemp core fibers were mixed with polypropylene and injection molded to obtain testing specimens. The effect of sodium hydroxide on the flexural modulus of composites was studied from macro and micro mechanical viewpoints. Results showed remarkable improvements in the flexural modulus due to the presence of hemp core fibers in the composites. At a 50 wt % of reinforcement content, increments around 239%, 250% and 257% were obtained for composites containing fibers treated at a 5, 7.5 and 10 wt % of NaOH, respectively. These results were comparable to those of wood composites, displaying the potential of hemp core residues. The intrinsic flexural modulus of the hemp core fibers was computed by means of micromechanical analysis and was calculated using the ratios between a fiber flexural modulus factor and a fiber tensile modulus factor. The results agreed with those obtained by using models such as Hirsch and Tsai-Pagano. Other micromechanical parameters were studied to fully understand the contribution of the phases. The relationship between the fibers\u27 intrinsic flexural and Young\u27s moduli was studied, and the differences between properties were attributed to stress distribution and materials\u27 anisotropy

Research on the suitability of organosolv semi-chemical triticale fibers as reinforcement for recycled HDPE composites

The main objective of this research was to study the feasibility of incorporating organosolv semi-chemical triticale fibers as the reinforcing element in recycled high density polyethylene (HDPE). In the first step, triticale fibers were characterized in terms of chemical composition and compared with other biomass species (wheat, rye, softwood, and hardwood). Then, organosolv semi-chemical triticale fibers were prepared by the ethanolamine process. These fibers were characterized in terms of its yield, kappa number, fiber length/diameter ratio, fines, and viscosity; the obtained results were compared with those of eucalypt kraft pulp. In the second step, the prepared fibers were examined as a reinforcing element for recycled HDPE composites. Coupled and non-coupled HDPE composites were prepared and tested for tensile properties. Results showed that with the addition of the coupling agent maleated polyethylene (MAPE), the tensile properties of composites were significantly improved, as compared to non-coupled samples and the plain matrix. Furthermore, the influence of MAPE on the interfacial shear strength (IFSS) was studied. The contributions of both fibers and matrix to the composite strength were also studied. This was possible by the use of a numerical iterative method based on the Bowyer-Bader and Kelly-Tyson equations

Advances in Natural Fibers and Polymers

The use of natural fibers as reinforcement for polymer-based composites has been attracting the interest of the scientific community for a long time [...

Characterization of CaCO3 Filled Poly(lactic) Acid and Bio Polyethylene Materials for Building Applications

[EN] Noise pollution has been identified as a cause of a broad spectrum of diseases, motivating researchers to identify building materials capable of attenuating this pollution. The most common solution is the use of gypsum boards, which show a good response for low frequencies but have a poorer response for high frequencies. In addition, due to environmental concerns associated with buildings, the use of materials that minimize environmental impacts must be favored. In this research, two biopolymers, a poly(lactic) acid and a bio-polyethylene, were filled with two typologies of calcium carbonate, and their soundproofing properties were tested using impedance tubes. In addition, the morphology of the fillers was characterized, and here we discuss its impact on the mechanical properties of the composites. The results showed that the incorporation of calcium carbonate into bio-based thermoplastic materials can represent a strong alternative to gypsum, because their mechanical properties and sound barrier performance are superior. In addition, the inclusion of mineral fillers in thermoplastic materials has a positive impact on production costs, in addition to preserving the advantages of thermoplastics in terms of processing and recycling. Although the use of carbonate calcium decreases the mechanical properties of the materials, it enables the production of materials with insulation that is four-fold higher than that of gypsum. This demonstrates the potential of these materials as building lightweight solutions.This research was funded by Agencia Estatal de Investigación, project METASON (PID2019-109175GB-C22).Serra-Parareda, F.; Alba, J.; Tarrés, Q.; Espinach, FX.; Mutjé, P.; Delgado-Aguilar, M. (2021). Characterization of CaCO3 Filled Poly(lactic) Acid and Bio Polyethylene Materials for Building Applications. Polymers. 13(19). https://doi.org/10.3390/polym13193323131

High Stiffness Performance Alpha-Grass Pulp Fiber Reinforced Thermoplastic Starch-Based Fully Biodegradable Composites

Alpha-grass was studied as the reinforcement in a starch-based polymer matrix. Mater-bi®-Y was chosen as a matrix due to its Young’s modulus, in line with that of polypropylene. The test specimens were injection molded and tensile tested. The obtained results were compared to glass fiber reinforced polypropylene. The reinforcing fibers increased the Young’s modulus significantly, obtaining values up to 7.2 GPa, comparable to those obtained with reinforced polypropylene. The contribution of the fibers to the final composite Young’s modulus was also studied, and it was found that was in line with other natural fibers contribution to polypropylene-based composites. Finally, it was found that the value of the efficiency factor of the module remained similar to that of natural fiber reinforced polypropylene

An Approach to Understanding the Hydration of Cement-Based Composites Reinforced with Untreated Natural Fibers

The use of untreated natural fibers to reinforce cementitious composites improves their environmental friendliness, resulting in a more sustainable material. Moreover, the influence of the untreated natural fibers on the hydration process of Portland cement composites presents some uncertainties. According to the literature, the most usual tests to analyze the degree of hydration of cement composites are the differential thermal and thermogravimetric analyses (TGA/dTGA). Several authors propose to analyze data methods to establish the degree of hydration of cement composites. This paper presents the TGA/dTGA test carried out on mortar samples with and without fibers at age 2, 3, 7, 14, and 28 days. The degree of hydration was calculated according to Bhatty’s method. To characterize the raw materials, the quantitative chemical was determined using scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM–EDX). The main findings of this study were that the presence of untreated natural hemp fibers in the OPC composites increased the hydration degree by 9%. The presence of fibers affected the formation of several components. Thus, their presence increased the formation of monosulphate, reduced portlandite, did not affect ettringite, and increased the formation of calcite, thereby improving the sustainable footprint due to the increased CO2 fixation

Study on the macro and micromechanics tensile strength properties of orange tree pruning fiber as sustainable reinforcement on bio-polyethylene compared to oil-derived polymers and its composites

Agroforestry creates value but also a huge amount of waste outside its value chain. Tree pruning is an example of such a low value waste, that is typically discarded or incinerated in the fields or used to recover energy. Nonetheless, tree prunings are rich in wood fibers that can be used as polymer reinforcement. Although there are some bio-based polymers, the majority of industries use oil-based ones. The election of the materials is usually based on a ratio between properties and cost. Bio-based polymers are more expensive than oil-based ones. This work shows how a bio-polyethylene matrix can be reinforced with fibers from orange tree prunings to obtain materials with notable tensile properties. These bio-based materials can show a balanced cost due to the use of a cheap reinforcement with an expensive matrix. The matrix used showed a tensile strength of 18.65 MPa, which reached 42.54 MPa after the addition of 50 wt.% of reinforcement. The obtained values allow the use of the studied composite to replace polypropylene and some of its composites under tensile loads. © 2020 by the authors. Licensee MDPI, Basel, Switzerland