Incorporation of biochar to improve mechanical, thermal and electrical properties of polymer composites

The strive for utilization of green fillers in polymer composite has increased focus on application of natural biomass-based fillers. Biochar has garnered a lot of attention as a filler material and has the potential to replace conventionally used inorganic mineral fillers. Biochar is a carbon rich product obtained from thermochemical conversion of biomass in nitrogen environment. In this review, current studies dealing with incorporation of biochar in polymer matrices as a reinforcement and conductive filler were addressed. Each study mentioned here is nuanced, while addressing the same goal of utilization of biochar as a filler. In this review paper, an in-depth analysis of biochar and its structure is presented. The paper explored the various methods employed in fabrication of the biocomposites. A thorough review on the effect of addition of biochar on the overall composite properties showed immense promise in improving the overall composite properties. An analysis of the possible knowledge gaps was also done, and improvements were suggested. Through this study we tried to present the status of application of biochar as a filler material and its potential future applications

Determining the Mechanical Properties of Microcrystalline Cellulose (MCC)-Filled PET-PTT Blend Composites

Polymer composite materials consisting of poly(ethylene terephthalate) (PET)-poly(trimethylene terephthalate) (PTT) blends and microcrystalline cellulose (MCC) were prepared by injection molding. The composites were analyzed for tensile, flexural, and impact strength as well as density determinations. There was no statistical difference in terms of mechanical properties between the control PET-PTT blend and 2.5 wt% MCC-filled composites. Because of better compatibility as well as better stress-transfer properties, the tensile strength of the composites was larger (reaching values from 24.8-36.3 MPa with the addition of 20 wt% MCC). Elongation at break of the composites was greater (reaching values from 2.3-3.3% with the addition of 20 wt% MCC). The tensile modulus of MCC-filled composites systemically increased with increasing MCC loading (reaching values from 1.11-1.68 GPa with the addition of 30 wt% MCC). The flexural modulus of composites was higher than the control PET-PTT blend. The modulus also increased with increasing MCC loading (reaching values from 2.10-3.37 GPa with the addition of 30 wt% MCC). The Izod impact strength of the composites decreased as the MCC loading increased and this observation was in good agreement with commonly observed filled polymer systems

Multifunctional PA6 composites using waste glass fiber and green metal organic framework/graphene hybrids

Glass fiber-polyamide 6 (PA6) composites are widely used for various automotive applications, yet the ability to exhibit multifunctional properties and the cost of it remains challenging. Herein this work introduces a cost-effective approach for utilization of waste glass fiber (GF), green aluminium metal organic framework (Al-MOF), and industry-grade graphene nanoplatelets (GNPs) for the fabrication of multifunctional PA6 thermoplastic composites with enhanced mechanical performance and fire retardancy. The results demonstrate that hybrid filler of Al-MOF and GNPs have a synergistic effect in improving the mechanical properties and fire retardancy of GF reinforced PA6 composites. Compared to the neat PA6, the PA6 composite containing 20 wt% GFs, 5 wt% GNPs, and 5 wt% Al-MOF exhibited ~97% and ~93% improvements in tensile and flexural strength, respectively. Also, compared to the neat PA6, 27 and 55°C increases were observed in glass transition temperature (Tg) and heat deflection temperature, respectively. Thermal stability and fire retardancy of the GFs/PA6 composites were significantly improved when hybridized with GNPs and Al-MOF

Microcrystalline Cellulose-Filled Engineering Thermoplastic Composites

The overall objective of this study was to investigate the influence of microcrystalline cellulose (MCC) filler loading on the mechanical and thermal properties of MCC-filled engineering thermoplastic composites. MCC and engineering thermoplastics (nylon 6 and a polyethylene terephthalate (PET)/polytrimethylene terephthalate (PTT) blend) were chosen as the filler/matrix combination. Engineering thermoplastic composites have attracted much interest over the past several decades due to potentially superior material properties and a wide range of applications such as in automotive, electrical and aerospace materials. MCC is thermally stable compared to other wood constituents and has the advantage of high specific surface area in comparison with conventional cellulose fibers. Because of these properties, MCC can use as a filler in polymer matrices. Differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and thermogravimetric analysis (TGA) were used to determine thermal properties of the composites. Infrared Spectroscopy (diffuse reflectance infrared Fourier transform (DRIFT)) was also used to identify chemical differences between the neat PET-PTT blend and MCC filled composites. The DSC results indicated that there was not a significant change in the glass transition (Tg) or melting temperature (Tm) of the nylon 6 and PET/PTT blend with the addition of MCC. With increasing MCC content, dynamic mechanical properties improved because of the reinforcing effect of the MCC. The TGA data show that as the MCC filler loading increased, the thermal stability of the composites decreased slightly because of the lower thermal stability of MCC compare to neat nylon 6 and PET/PTT blend. Thermogravimetric analysis also indicated that the MCC did not show significant initial degradation under 300°C, which implies thermal stability so that MCC-filled composites could be used for high temperature circumstances, like in under the hood applications in the automobile industry. No significant chemical changes were observed in the DRIFT spectra of the composites. Tensile, flexural and impact tests were used to evaluate the mechanical properties of the composites as well as determining the composite densities. The composites reinforced with higher MCC filler loadings displayed enhanced tensile and flexural properties in comparison with the neat nylon 6 and PET/PTT blend. The Izod impact strength of the composites decreased in comparison with the neat nylon 6 and PET/PTT blend. The density of the composites increased slightly with increased MCC loading

Carrier Systems for Cellulose Nanofibers in Hydrophobic Polymer Composites

Recent years have seen a sharp increase in interest around the world regarding cellulose nanocomposites. The number of publications including research papers and patents on the preparation of nanocomposites containing cellulose nanofibers has dramatically increased. One of the major challenges in cellulose nanocomposite applications is the lack of compatibility with hydrophobic polymer matrices. Cellulose nanofibers cannot simply be added to the polymer melt in thermal compounding processes because of the potential for agglomeration. To prevent cellulose nanofibrils from aggregating, and also to improve their dispersion in hydrophobic polymer matrices, modification of cellulose surfaces or use of a carrier system for cellulose nanofibrils is required. In this study, cellulose nanofiber suspensions were processed with novel carrier systems, using thermoplastic starch (TPS), functionalized TPS, polyvinyl alcohol (PVA) and poly-hydroxybutyrate (PHB) in an attempt to create compatibility between the cellulose nanofibril (CNF) suspension and hydrophobic polymer matrices including polyolefin matrices (polypropylene (PP), polyethylene (PE)) and a biodegradable polymer matrix (polylactic acid (PLA). Experimental cellulose nanocomposite process mixing using conventional thermoplastic processing techniques took place on a C.W. Brabender Prep Mixer® temperature controlled mixing head. Tensile, flexural and impact tests were used to evaluate the mechanical properties of the composites, and the composite densities were determined. Results indicate that CNF with carrier system-filled composites showed comparable or lower mechanical properties compared to control samples without the addition of compatibilizers. Several analytical tools were used to screen the composite materials including: scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and cone and plate rheometry to determine rheological behavior including shear rate and viscosity. It is believed that this research provides insight into potential applications of CNF-filled hydrophobic polymers. Possible applications for the composites studied in this research are packaging materials, construction materials and auto parts for interior applications

Rheological and Mechanical Properties of Ultra-fine Cellulose-Filled Thermoplastic Epoxy Composites

Thermoplastic epoxy resin (TPER)-based composites containing different amounts of ultra-fine cellulose (UFC) were prepared via melt compounding and injection molding. The effect of UFC loading on the mechanical properties and dynamic rheological behavior of the UFC-filled TPER composites was analyzed. The UFC-filled composites displayed higher complex viscosities than those of the neat TPER composites, especially at low frequencies. The elastic modulus of the 20 wt.% UFC-filled composite was up to 6- and 2-fold higher than that of TPER at 0.1 and 100 Hz, respectively. The loss factor decreased over the entire frequency range with the incorporation of UFC. The tensile modulus of elasticity (TMOE) of neat TPER was 3.13 GPa, and it increased as a function of UFC loading. The neat TPER exhibited the lowest flexural strength (108.1 MPa), and the flexural strength increased by 14% with the incorporation of 20 wt.% UFC. The results of the TMOE and the flexural modulus of elasticity (FMOE) were in agreement with rheological data on complex viscosity, elastic modulus, and viscous modulus. Ultra-fine cellulose-filled TPER composites may provide special capabilities for automotive applications and may also meet requirements for end-of-life vehicle (ELV) directives

Synthesis of bacterial cellulose using hot water extracted wood sugars

Bacterial cellulose (BC), a type of nanopolymer produced by Acetobacter xylinum is a nanostructured material with unique properties and wide applicability. However, a standard medium used for the cultivation of BC, the Hestrin-Schramm medium, is expensive and prevents wide scale extension of BC applications. In this research, a relatively low-cost culture media was successfully developed from wood hot water extracts for the Acetobacter xylinus 23769 strain. Hot water extract (HWE) is a residual material originating from pulp mills and lignocellulosic biorefineries and consists of mainly monomeric sugars, organic acids and organics. The effects of different pH (5, 6, 7 and 8) and temperatures (26,28 and 30 degrees C) were also examined in this research. There were no significant differences in the crystallinity and the recorded I-alpha, fraction of cellulose produced between Hestrin-Schramm and the HWE medium. The maximum production of 0.15 g/l of BC was obtained at a pH of 8 and temperature of 28 degrees C. Glucose and xylose in the HWE were the main nutrient sources utilized in all BC cultivations based on high-pressure liquid chromatography (HPLC) results. HWE was shown to be a suitable carbon source for BC production, and a process was established for BC production from lignocellulosic feedstocks without using any modification of the HWE. HWE is an abundant and relatively inexpensive forest by-product. Using HWE for BC production could reduce burdens on the environment and also, achieve the goal of large scale BC production at low cost without using added culture nutrients. (C) 2015 Elsevier Ltd. All rights reserved