Dilpreet S. Bajwa

Optimal Substitution of Cotton Burr and Linters in Thermoplastic Composites

A study was conducted to evaluate various substitutions of cotton burr and linters from cotton gin waste (CGW) as natural fiber reinforcements in ligno-cellulosic polymer composites (LCPC). Samples were fabricated with approximately 50 percent natural fiber, 40 percent high-density polyethylene, 4 percent mineral filler, and 6 percent lubricant, by weight. The experiment included substituting wood fiber in LCPC with 25, 50, 75, and 100 percent (by weight) cotton burr (CB) and cotton burr mixed with 2 percent (by weight) second-cut linters (CBL), respectively, with the remaining fraction as wood fiber and comparing it against the control (100% wood). Samples were extruded into rectangular profiles and tested for physical and mechanical properties such as specific gravity (SG), water absorption, thickness swelling, coefficients of linear thermal expansion (CLTE), flexural strength and modulus, compressive strength, hardness, and nail withdrawal force (NWF). The CB and CBL treatments exhibited SG, CLTE, hardness, and NWF comparable to the control. However, the water absorption and thickness swelling, flexural strength and modulus, and compressive strength all deteriorated at high substitution rates of CB and CBL. The favorable properties of cotton burr included its tendency to decrease CLTE and increase hardness of LCPC.

Effect of Laboratory Aging on the Physical and Mechanical Properties of Wood-Polymer Composites

The long-term performance of wood-polymer composites (WPC) under severe weather conditions is not well known. This study evaluates the changes in physical and mechanical properties of three commercially available WPC and treated southern yellow pine (SYP) under a modified 6-cycle accelerated aging process. The accelerated aging causes warping, splitting, discoloration, and significant changes in physical and mechanical properties of SYP. The compressive and flexural strength of the WPCs show negligible changes whereas stiffness, hardness, and screw withdrawal force show considerable deterioration and some recovery during accelerated aging. The composition and manufacturing process influence the performance of WPC under accelerated aging.

Application of bioethanol derived lignin for improving physico-mechanical properties of thermoset biocomposites

Lignin is the most abundant of renewable polymers next to cellulose with a global annual production of 70million tons, largely produced from pulping and second generation biofuel industries. Low value of industrial lignin makes it an attractive biomaterial for wide range of applications. The study investigated the application of wheat straw and corn stover based lignin derived from ethanol production for use in thermoset biocomposites. The biocomposite matrix constituted a two component low viscosity Araldite(®)LY 8601/Aradur(®) 8602 epoxy resin system and the lignin content varied from 0 to 25% by weight fraction. The analysis of the physical and mechanical properties of the biocomposites show bioethanol derived lignin can improve selective properties such as impact strength, and thermal stability without compromising the modulus and strength attributes.

Oriented Strandboard (OSB) Panels Made from Kenaf Stalks and Aspen

Abstract The specific gravity of these panels varied from 0.68 to 0.75. The amount of kenaf, resin content significantly affected the modulus of rupture and the modulus of elasticity values of aspen-kenaf boards. Boards with 25% kenaf and 75% aspen produced MOR and MOE values comparable to commercial oriented strandboard (OSB). Percentage of kenaf and resin levels were significant factors influencing the internal bond (IB) strength when compared to the commercial OSB. The 25% kenaf and 75% aspen boards produced IB values that could meet the required standard. Aspen-kenaf boards obtained lower values for linear expansion. Lower percentage of kenaf flakes and higher resin content controlled thickness swelling. However, boards with 50% kenaf and 50% aspen flakes made with 6% resin resulted in a thickness swelling of less than 10%.

Spin-coating: A new approach for improving dispersion of cellulose nanocrystals and mechanical properties of poly (lactic acid) composites

This study systematically evaluated the influence of masterbatch preparation techniques, solvent casting and spin-coating methods, on composite properties. Composites were manufactured by combining CNCs masterbatches and PLA resin using twin screw extruder followed by injection molding. Different microscopy techniques were used to investigate the dispersion of CNCs in masterbatches and composites. Thermal, thermomechanical, and mechanical properties of composites were evaluated. Scanning electron microscopy (SEM) images showed superior dispersion of CNCs in spin-coated masterbatches compared to solvent cast masterbatches. At lower CNCs concentrations, both SEM and optical microscope images confirmed more uniform CNCs dispersion in spin-coated composites than solvent cast samples. Degree of crystallinity of PLA exhibited a major enhancement by 147% and 380% in solvent cast and spin-coated composites, respectively. Spin-coated composites with lower CNCs concentration exhibited a noticeable improvement in mechanical properties. However, lower thermal characteristics in spin-coated composites were observed, which could be attributed to the residual solvents in masterbatches.

Influence of Hybridizing Flax and Hemp-Agave Fibers with Glass Fiber as Reinforcement in a Polyurethane Composite

In this study, six combinations of flax, hemp, and glass fiber were investigated for a hybrid reinforcement system in a polyurethane (PU) composite. The natural fibers were combined with glass fibers in a PU composite in order to achieve a better mechanical reinforcement in the composite material. The effect of fiber hybridization in PU composites was evaluated through physical and mechanical properties such as water absorption (WA), specific gravity (SG), coefficient of linear thermal expansion (CLTE), flexural and compression properties, and hardness. The mechanical properties of hybridized samples showed mixed trends compared to the unhybridized samples, but hybridization with glass fiber reduced water absorption by 37% and 43% for flax and hemp-agave PU composites respectively.

Current Progress, Trends and Challenges in the Application of Biofiber Composites by Automotive Industry

ABSTRACT The use of biofiber, or natural fiber, composites by the U.S. automotive industry is on the rise. Biofiber composites are now being considered a meaningful alternative to glass fiber composites. This paper examines the current status of biofiber composites in the automotive sector. The investigation highlights the progress of the application of different types of non-woody and woody cellulosic fibers for designing and fabricating composite automotive components. The improvements in the processing techniques, production methods of different biofiber composites, and the potential applications of these composites in the automotive sector have been taken into consideration. The global emerging trends towards designing and deploying biofiber composite components by leading manufacturers are discussed. Further this study highlights the strengths and obstacles encountered for commercialization and adoption of biofiber composite materials. Current research priorities and global sustainability initiatives further offer insight to future trends.

Feasibility of Reprocessing Natural Fiber Filled Poly(lactic acid) Composites: An In-Depth Investigation

Poly(lactic acid) (PLA) based composites are biodegradable; their disposal after single use may be needless and uneconomical. Prodigal disposal of these composites could also create an environmental concern and additional demand for biobased feedstock. Under these circumstances, recycling could be an effective solution, since it will widen the composite service life and prevent the excessive use of natural resources. This research investigates an in-depth impact of recycling on the mechanical and thermomechanical properties of oak wood flour based PLA composites. Two composite formulations (30 and 50 wt% filler), each with 3 wt% coupling agent (PLA-g-MA), were produced and reprocessed six times by extrusion followed by injection molding. Measurements of fiber length and molecular weight of polymer were, respectively, carried out by gel permeation chromatography (GPC). Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR) tools were used to study morphological and molecular alterations. With consecutive recycling, PLA composites showed a gradual decrease in strength and stiffness properties and an increase in strain properties. The 50% and 30% filler concentration of fibers in the composite showed an abrupt decrease in strength properties after six and two reprocessing cycles, respectively.

Commercial-scale evaluation of two agricultural waste products, cotton burr/stem and module wraps, in thermoplastic composites and its comparison with laboratory-scale results

Laboratory-scale research had shown the potential of using cotton burr/stem (CBS) as fiber filler in thermoplastic composites. This study evaluates the potential of using waste materials from cotton harvesting/ginning operations, CBS and cotton module wraps (CMWs), as a filler and substrate in thermoplastic composites at commercial scale. The study also compares the effect of scale-up from laboratory to commercial scale on the properties of the thermoplastic composite materials. Two separate commercial trials were conducted to manufacture thermoplastic composite boards with (a) 0, 12.5, 25 and 37.5% by weight of CBS and (b) up to 30% by weight of CMW. Testing of these samples showed that commercial-scale samples with 12.5% CBS had all properties comparable to those made with wood filler. At higher substitution rates, CBS tended to increase water absorption and coefficient of thermal expansion, and increase nail-holding capacity (NHC) and hardness in commercial-scale samples. This study also showed that CMW can be substituted by up to 30% by weight without deterioration of properties in comparison with a commercially available product. Scaling of the process had significant influence on all properties tested, expect NHC. In general, all commercial-scale samples exhibited physicomechanical properties within the range of properties reported for commercially available wood–plastic composite decking materials.