Performance of Cow Dung Reinforced Biodegradable Poly(Lactic Acid) Biocomposites for Structural Applications

In this work, performance of cow dung (CD) reinforced poly(lactic acid) (PLA) biocomposites was investigated for the potential use in load bearing application. CD of average 4 mm size was blended with PLA at different CD ratios (0–50 wt%) and their effects on the biocomposite properties were studied. The results showed an improvement in the flexural properties, while the tensile and impact strength dropped by 20 and 28% with the addition of 50% CD. The decline in the tensile and impact strength was due to micro-cracking and voids formation at higher CD content. Also, the incorporation of CD slightly decreased the thermal stability of the biocomposite. However, dynamic mechanical properties of the biocomposites generally improved. SEM analysis of tensile and impact fractured surfaces indicated that the CD had a reasonable adhesion with matrix. Moreover, the SEM micrographs of soil burial studies showed an accelerated degradation of higher CD wt% biocomposites.     

Fabrication of Admicelled Natural Rubber by Polycaprolactone for Toughening Poly(lactic acid)

Natural rubber (NR) with polycaprolactone (PCL) core–shell (NR-ad-PCL), synthesized by admicellar polymerization, was acted as an impact modifier for poly(lactic acid) (PLA). PLA and NR-ad-PCL were melt-blended using a co-rotating twin screw extruder. The morphology of PLA/NR-ad-PCL blends showed good adhesion as smooth boundary around rubber particles and PLA matrix. Only 5 wt% of rubber phase, NR-ad-PCL was more effective than NR to enhance toughness and mechanical properties of PLA. The contents of the NR-ad-PCL were varied from 5, 10, 15 and 20 wt%. From thermal results, the incorporation of the NR-ad-PCL decreased the glass transition temperature and slightly increased degree of crystallinity of PLA. Mechanical properties of the PLA/NR-ad-PCL blends were investigated by dynamic mechanical analyser, pendulum impact tester and universal testing machine for tension and flexural properties. The increasing NR-ad-PCL contents led to decreasing Young’s and storage moduli but increasing loss modulus. Impact strength and elongation at break of the PLA/NR-ad-PCL blends increased with increasing NR-ad-PCL content up to 15 wt% where the maximum impact strength was about three times higher than that of pure PLA and the elongation at break increased to 79%.     

Biopolymer (Chitin) from Various Marine Seashell Wastes: Isolation and Characterization

Chitin has been produced from different sea waste sources including, molluscs (mussel and oyster shell), crustacean (prawn and crab) and fish scale (pang and silver scales) using deproteinization and demineralization as chemical methods. The conditions of chemical extraction process determine the quality of chitin. The obtained results revealed that, about 1 and 10% HCl and NaOH were adequate concentrations for deproteinization and demineralization process respectively. Chitin from oyster and crab shell waste had the highest yield of 69.65 and 60.00% while prawn, mussel shell, pang and silver scales had the lowest yield of 40.89, 35.03, 35.07 and 31.11% respectively. Chitin solubility is controlled by the quantity of protonated acetyl groups within the polymeric chain of the chitin backbone, thus on the percentage of acetylated and non-acetylated d-glucos-acetamide unit. Good solubility results were obtained in mussel, oyster and crab shells respectively. The chitin molecular weight characteristics and activity are controlled by the degree of acetylation (DA) and the distribution of acetyl group extending in the polymer chain. DA is determined by acid-base titration methods and molecular weight determined by Brookfield viscometry. Both methods are found to be effective.     

Thermally Stable Pyrolytic Biocarbon as an Effective and Sustainable Reinforcing Filler for Polyamide Bio-composites Fabrication

Natural fibers are limited in their use as reinforcement to commodity polymers. They cannot be used to reinforce engineering polymers due to their low thermal stability at high processing temperatures. This study presents an approach to successfully reinforce polyamides using a derivative of natural fibers as reinforcement without the effects of thermal degradation during melt processing. Biocarbon from miscanthus fibers was used to reinforce polyamide 6 up to 40 wt%. At 40 wt% filler content, the tensile and flexural strengths increased by 19.6 and 47% respectively in comparison to the neat polyamide. The moduli were also increased by 31.5 and 63.7% respectively. A maximum increase in impact strength of 43.7% was achieved at 20 wt% biocarbon loading. The morphology of the tensile fractured samples showed stretched polyamide ligaments attached to the biocarbon particles, indicating the presence of interaction between filler and matrix. Interestingly, more bonded interfaces were observed between the polyamide and biocarbon particles with increasing biocarbon content possibly stemming from increased biocarbon surfaces with functional groups. These composites show great potential to substitute in part or whole, some particulate filled polyamides currently used in the automotive industry.     

Transfer of Graphene CVD to Surface of Low Density Polyethylene (LDPE) and Poly(butylene adipate-co-terephthalate) (PBAT) Films: Effect on Biodegradation Process

Here, the influence of graphene as a coating on the biodegradation process for two different polymers is investigated, poly(butylene adipate-co-terephthalate) (PBAT) (biodegradable) and low-density polyethylene (LDPE) (non-biodegradable). Chemical vapor deposition graphene was transferred to the surface of two types of polymers using the Direct Dry Transfer technique. Polymer films, coated and uncoated with graphene, were buried in a maturated soil for up to 180 days. The films were analyzed before and after exposure to microorganisms in order to obtain information about the integrity of the graphene (Raman Spectroscopy), the biodegradation mechanism of the polymer (molecular weight and loss of weight), and surface changes of the films (atomic force microscopy and contact angle). The results prove that the graphene coating acted as a material to control the biodegradation process the PBAT underwent, while the LDPE covered by graphene only had changes in the surface properties of the film due to the accumulation of solid particles. Polymer films coated with graphene may allow the production of a material that can control the microbiological degradation, opening new possibilities in biodegradable polymer packaging. Regarding the possibility of graphene functionalization, the coating can also be selective for specific microorganisms attached to the surface.     

Catalytic upgrading pyrolysis of pine sawdust for bio-oil with metal oxides

The catalytic upgrading pyrolysis of pine sawdust was performed at 500 °C with various metal oxides to improve the quality of the bio-oil. The aim of this study was to investigate the potential of the metal oxides instead of traditional zeolites for catalytic upgrading pyrolysis with the analysis of Gas Chromatograph/Mass Spectrometer. In this study, the used catalysts were Calcium-oxide, Magnesium oxide, Titanium dioxide, and Zeolite (Si/Al?=?80). The influence of catalysts on products yields and compositions were investigated. Most metal oxides can enhance the bio-gas with the bio-oil yields decreased. The metal oxides led to a decrease of Acids, Aldehydes, Ketones and an increase of Furfural, Cresols, Catechols in Furans and Phenolics. Among the catalysts, the MgO catalysts was the most effective to convert the high molecular into lights ones (6.65% Cresols) with yield of 20.48% for Furfural. The deoxygenation reaction in bio-oil was suggested to convert oxygenated compounds into the low molecular weight of the materials (6.39% Guaiacols). Thus, the used metal oxides can improve the quality of bio-oil by decreasing undesirable compounds as well as increasing the desirable compounds with low oxygen contents via deoxygenation reaction.     

Household water insecurity and its cultural dimensions: preliminary results from Newtok,Alaska

Using a relational approach, I examine several cultural dimensions involved in household water access and use in Newtok, Alaska. I describe the patterns that emerge around domestic water access and use, as well as the subjective lived experiences of water insecurity including risk perceptions, and the daily work and hydro-social relationships involved in accessing water from various sources. I found that Newtok residents haul water in limited amounts from a multitude of sources, both treated and untreated, throughout the year. Household water access is tied to hydro-social relationships predicated on sharing and reciprocity, particularly when the primary treated water access point is unavailable. Older boys and young men are primarily responsible for hauling water, and this role appears to be important to male Yupik identity. Many interviewees described preferring to drink untreated water, a practice that appears related to cultural constructions of natural water sources as pure and self-purifying, as well as concerns about the safety of treated water. Concerns related to the health consequences of low water access appear to differ by gender and age, with women and elders expressing greater concern than men. These preliminary results point to the importance of understanding the cultural dimensions involved in household water access and use. I argue that institutional responses to water insecurity need to incorporate such cultural dimensions into solutions aimed at increasing household access to and use of water.     

Two sampling strategies for an overview of pesticide contamination in an agriculture-extensive headwater stream

Two headwaters located in southwest France were monitored for 3 and 2 years (Auvézère and Aixette watershed, respectively) with two sampling strategies: grab and passive sampling with polar organic chemical integrative sampler (POCIS). These watersheds are rural and characterized by agricultural areas with similar breeding practices, except that the Auvézère watershed contains apple production for agricultural diversification and the downstream portion of the Aixette watershed is in a peri-urban area. The agricultural activities of both are extensive, i.e., with limited supply of fertilizer and pesticides. The sampling strategies used here give specific information: grab samples for higher pesticide content and POCIS for contamination background noise and number of compounds found. Agricultural catchments in small headwater streams are characterized by a background noise of pesticide contamination in the range of 20–70 ng/L, but there may also be transient and high-peak pesticide contamination (2000–3000 ng/L) caused by rain events, poor use of pesticides, and/or the small size of the water body. This study demonstrates that between two specific runoff events, contamination was low; hence the importance of passive sampler use. While the peak pesticide concentrations seen here are a toxicity risk for aquatic life, the pesticide background noise of single compounds do not pose obvious acute nor chronic risks; however, this study did not consider the risk from synergistic “cocktail” effects. Proper tools and sampling strategies may link watershed activities (agricultural, non-agricultural) to pesticides detected in the water, and data from both grab and passive samples can contribute to discussions on environmental effects in headwaters, an area of great importance for biodiversity.     

Photocatalytic reduction of carbon dioxide over Cu/TiO<Subscript>2</Subscript> photocatalysts

The photocatalytic reduction of CO₂ with H₂O was investigated using Cu/TiO₂ photocatalysts in aqueous solution. For this purpose, Cu/TiO₂ photocatalysts (with 0.2, 0.9, 2, 4, and 6 wt.% of Cu) have been synthesized via sol-gel method. The photocatalysts were extensively characterized by means of inductively coupled plasma optical emission spectrometry (ICP-OES), N₂ physisorption (BET), XRD, UV-vis DRS, FT-IR, Raman spectroscopy, TEM-EDX, and photoelectrochemical measurements. The as-prepared photocatalysts contain anatase as a major crystalline phase with a crystallite size around 13 nm. By increasing the amount of Cu, specific surface area and band gap energy decreased in addition to the formation of large agglomeration of CuO. Results revealed that the photocatalytic reduction of CO₂ decreased in the presence of Cu/TiO₂ in comparison to pure TiO₂, which might be associated to the formation of CuO phase acting as a recombination center of generated electron-hole pair. Decreasing of photoactivity can also be connected with a very low position of conduction band of photocatalysts with high Cu content, which makes H₂ production necessary for CO₂ reduction more difficult.     

Spatial distribution of metals within the liver acinus and their perturbation by PCB126

Animal studies show that exposure to the environmental pollutant 3,3′,4,4′,5-pentachlorobiphenyl (PCB126) causes alterations in hepatic metals as measured in acid-digested volume-adjusted tissue. These studies lack the detail of the spatial distribution within the liver. Here we use X-ray fluorescence microscopy (XFM) to assess the spatial distribution of trace elements within liver tissue. Liver samples from male Sprague Dawley rats, treated either with vehicle or PCB126, were formalin fixed and paraffin embedded. Serial sections were prepared for traditional H&E staining or placed on silicon nitride windows for XFM. With XFM, metal gradients between the portal triad and the central vein were seen, especially with copper and iron. These gradients change with exposure to PCB126, even reverse. This is the first report of how micronutrients vary spatially within the liver and how they change in response to toxicant exposure. In addition, high concentrations of zinc clusters were discovered in the extracellular space. PCB126 treatment did not affect their presence, but did alter their elemental makeup suggesting a more general biological function. Further work is needed to properly evaluate the gradients and their alterations as well as classify the zinc clusters to determine their role in liver function and zinc homeostasis.