Lee Miller Smith

The push for sustainability in all facets of manufacturing has led to an increased interest in biomass as an alternative to non-renewable materials. Hemp bast fiber mats were produced from a bacterial retting process, named BFM, as the fiber reinforcement. The objective of this study was to evaluate the feasibility of laminating BFM with polylactic acid (PLA) for a composite panel product. Since both BFM and PLA are biodegradable, the resulting BFM-PLA composites will be 100% biodegradable. PLA pallets were processed into thin polymer sheets which served as the matrix. The BFM and PLA plates were laminated in five layers and compression-molded into composite panels. Experiments were conducted on the three BFM-to-PLA ratios (35/65, 45/55, and 50/50). Mechanical properties (tensile and bending properties) and physical properties (thickness swell and water absorption) were tested and compared to the currently commercial sheet molding compound (SMC) from fiber glass. The thermal behavior of the BFM/PLA composites was characterized using dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). The developed BFM/PLA composite product is a sustainable alternative to existing synthetical fiber-reinforced polymer (FRP) that is biodegradable in landfill at the end of life.

Carbon nanomaterials-based electric double-layer capacitors (EDLCs) are reliable and appealing energy-storage systems offering high power density and long cycling stability. However, these energy storage devices are plagued with critical shortcomings, such as low specific capacitance, inefficient physical/chemical activation process, and self-discharge of electrode materials, hindering their future application. In this work, we use a self-activation process, an environmentally benign and low-cost process, to produce high-performance activated carbon (AC). Novel activated carbon from pecan shells (PS) was successfully synthesized through a single-step self-activation process, which combines the carbonization and activation processes. The as-synthesized pecan shell-derived activated carbon (PSAC) provides a high-porosity, low-resistance, and ordered pore structure with a specific pore volume of 0.744 cm³/g and BET surface area of 1554 m²/g. The supercapacitors fabricated from PSAC demonstrate a specific capacitance of 269 F/g at 2 A/g, excellent cycling stability over 15,000 cycles, and energy and power density of 37.4 Wh/kg and of 2.1 kW/kg, respectively. It is believed that the high-efficiency PSAC synthesized from the novel self-activation method could provide a practical route to environmentally friendly and easily scalable supercapacitors.

For the pyrolysis process, the inability to monitor the system greatly affects the pyrolysis efficiency of different raw feedstocks to produce pyrolysis oil, synthesis gases (syn gases), and activated carbon. To address such limitation, development of a model is needed in order to better understand what types of gases that are produced during the pyrolysis. In this study, a triple Gaussian model was developed to effectively describe the gas production during the biomass pyrolysis process at different dwelling temperatures and ramping rates. A CO 2 gas sensor array was built to monitor and collect the gas production data of southern yellow pine (SYP), which was then fitted to the gaussian model. The Gaussian model was constructed from three separate Gaussian functions, which represented three ranges of the gas production curve: Carbonization Range, Gasification Range, and Modification Range. The amplitude A (relating the peak gas production), mean µ (relating the time that the gas production reaches its peak), and standard deviation σ (relating the rate of gas production) components of the triple Gaussian function were compared against the ramping rate and dwelling temperature. The relationship between ramping rate and dwelling temperature and the Gaussian components at the different ranges showed the impact of CO 2 production on the biomass pyrolysis process. It was observed that as the ramping rate and dwelling temperature increased, the peak production of CO 2 increased. In the carbonization range, A increased with ramping rate and dwelling temperature, achieving the peak gas production values. The µ and σ of this range decreased as ramping rate increased, demonstrating that the peak production of CO 2 was increased early. In the Gasification range, the σ decreased as the ramping rate and dwelling temperature increased which indicated the decrease in CO 2 production. These relationships between Gaussian components and ramping rate and dwelling temperature, showed clear linear trends.

The focus of this report was to understand the tensile properties and dynamic mechanical properties of bamboo powder (BP) reinforced polylactic acid (PLA) composite filaments which were treated with nano calcium carbonate (CaCO₃), cellulose nanofibers (CNF), and micro-crystalline cellulose (MCC) using impregnation modification technology. The storage modulus (E’) of nano CaCO₃-BP/PLA, MCC-BP/PLA, and CNF-BP/PLA composite filaments increased compared with BP/PLA composite filaments before the glass transition temperature T_g. When the temperature was above T_g, the reinforcement effect of nano CaCO₃, MCC, and CNF gradually became less apparent. The loss modulus (E’’) and loss factor (tan δ_max) of the nano CaCO₃-BP/PLA, MCC-BP/PLA, and CNF-BP/PLA composite filaments was higher than that of BP/PLA composite filaments produced by the “one-step” method. The tensile strength (TS) results showed a similar trend. Compared with the control samples, the TS of nano CaCO₃-BP/PLA, MCC-BP/PLA, and CNF-BP/PLA composite filaments produced by the “one-step” method (and the “two-step” method) increased by 40.33% (and 10.10%), 32.35% (and −8.61%), and 12.32% (and −12.85%), respectively. The TS of nano CaCO₃-BP/PLA, MCC-BP/PLA, and CNF-BP/PLA composite filaments produced by the “one-step” method was slightly higher than those produced by the “two-step” method. The elongation at break (EAB) of BP/PLA composite filaments was higher than that of BP/PLA samples treated with nano CaCO₃, MCC, or CNF. The PLA and modified BP were readily accessible through a simple mixing process. The rheological investigation of such mixtures showed that nano CaCO₃, CNF, and MCC have different effects on the processability and rheological properties of composites.

The focus of this study was to observe the mechanical properties of bamboo plastic composites (BPCs) with bamboo pulp fiber (BPF) or white mud (WM). The essential work of fracture (EWF) methodology was used to characterize the impact toughness of BPCs. The results revealed an increase in flexural, tensile and impact properties, when adding the BPF in the BPCs. While the flexural properties of WM-reinforced BPCs revealed increasing, there was a decrease in tensile and impact strength. In an impact strength analysis study, BPF-filled BPCs showed excellent impact property over WM-filled BPCs; scanning electron microscopy (SEM) helps to explain impact fracture behavior of BPCs. EWF analysis of impact results showed that the specific essential work of fracture (w_e) increased significantly with the amount of BPF used in BPCs but decreased with the increase of WM in the BPCs. There was similar variation for the non-essential plastic work (βw_p) of BPCs. This result indicates that the fracture initiation and fracture propagation of BPCs are different.