Sagarika Panigrahi

The potential of sensing devices can be significantly enhanced by utilizing biodegradable polymers with adjustable mechanical, adhesion, and healing properties. In this study, adhesive films made from dopamine (DA) and citric acid (CA) modified polyvinyl alcohol (PVA) are presented. These films are exclusively derived from bio-based materials, following an environmentally friendly and easily reproducible process that is also scalable. They exhibit robust adhesion and easy detachment from various substrates, such as stainless steel (138 – 191 kPa), particularly in the presence of moisture. In contrast to the extended degradation time of pure PVA, the composite films prepared in this study show accelerated degradation under anaerobic conditions. Notably, modified biofilms (P1DA1CA1, P1DA2CA1) exhibit superior degradation compared to conventional plastic PVA, with the exception of P1DA1CA2. The slower degradation in P1DA1CA2 is attributed to the higher acidic concentration contributed by citric acid. The study delves into the morphological changes of the prepared and degraded films using scanning electron microscopy (SEM), and the degradation process is characterized through chromatographic techniques. The study suggests that dopamine (DA) and citric acid (CA) molecules penetrate the interplanar distance of P chains, as supported by powder X-ray diffraction studies, thereby expediting the degradation process. Additionally, the inclusion of CA enhances the stability of DA molecules against oxidation, increases H-bonding, and acts as a plasticizer. These synergistic interactions are further corroborated by Fourier transform infrared (FTIR), SEM, thermogravimetric analysis (TGA), and tensile studies. The introduction of DA and CA imparts self-healing properties to the films due to the presence of multiple H-bonds. Tensile studies reveal that the strength of self-healed samples approaches that of pristine samples. Overall, the findings of this study hold promise for the development of innovative, biodegradable PVA-based self-healing adhesive films with potential applications across various domains.

Recent studies have proposed usage of biochar as a substrate amendment in green infrastructure, such as green roofs and bio-filtration units. However, understanding of the variation in physio-chemical properties of biochar due to the production process and feedstock is still lacking. The present study investigated the effects of pyrolysis temperature and feedstocks on the hygroscopic water content and physio-chemical properties of biochar. Biochars were produced from three feedstock types, invasive vegetation (i.e., water hyacinth), non-invasive vegetation (i.e., wood) and one animal waste (i.e., chicken manure). Biochar was produced at two different pyrolysis temperatures (i.e., 300 °C and 600 °C). Scanning electron microscopy + energy dispersive spectrometry (SEM + EDS), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) were performed on all samples to analyze the surface morphology, pore size, element content, functional groups, and chemical bonds. Relative humidity was adjusted to reflect the biochar’s hygroscopic property by measuring the maximum moisture content at the sample equilibrium state. The characterization reveals that the lowest carbon content (42.78%) was found at 300 °C for water hyacinth biochar (WHB). The highest carbon content (92.14%) was found at 600 °C for wood biochar (WB). As the pyrolysis temperature increased, the mean pore volume (from 0.03 to 0.18 cm³/g) and diameter (from 8.40 to 10.33 nm) of the WHB increased. However, the pore diameter of chicken manure (CB) decreased (from 9.23 nm to 7.53 nm) under an increase in pyrolysis temperature. For a given pyrolysis temperature, the hygroscopicity of WHB was highest among all biochars. With an increase in pyrolysis temperature, the hygroscopicity of biochars changed differently. The hygroscopicity of WHB decreased from 82.41% to 44.33% with an increase of pyrolysis temperature. However, the hygroscopicity of CMB and WB remained unchanged. This study suggests that production process of biochars need to be considered for appropriate selection as substrate material in green infrastructure. Further, it promotes the establishment of commercial production of biochar for usage in green infrastructure.