Interactive Influence of Biofiber Composition and Elastomer on Physico-Mechanical Properties of PLA Green Composites

The objective of this work was to improve the impact and thermal properties of polylactic acid (PLA)-based biocomposite by appropriate application of cellulosic fiber and a bioelastomer. Biocomposites formulations with fiber contents of up to 20% in combination with a bioelastomer were extrusion-compounded in a twin-screw extruder followed by molding in an injection molding system. Fibers used in the formulations included three types of cellulosic fiber; namely, raw fiber from oat hull biomass (RF), hydrolysis byproduct (ATF) which was the solid fraction obtained from an acid-catalyzed hydrolysis of RF, and delignified fibers (AD30, AD65, AD100) which were the products of delignification of ATF. Formulated biocomposites were characterized for thermal (glass transition and melting temperatures, and enthalpy of melting) and physico-mechanical (tensile and bending strengths, stiffness, impact energy, and water absorption) properties. Among all types of biofibers, RF resulted in poor properties in the biocomposites due to the high hemicellulose content in the structure. On the other hand, the ratio of lignin to cellulose (in the absence of hemicellulose) in the modified fibers did not significantly affect the physico-mechanical and thermal properties of the biocomposites. The elastomer applied in the formulations improved the impact energy, thermal properties, and elongation at break of the composites. However, it adversely affected the strength and water resistance of biocomposites, especially in the presence of hemicellulose. The results indicated that, depending on the application, a wide range of PLA green composites with different physico-mechanical properties can be achieved.     

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.     

Polychlorinated biphenyls (PCBs) and halogenated flame retardants (HFRs) in multi-matrices from an electronic waste (e-waste) recycling site in Northern China

The present study investigated the occurrence of polychlorinated biphenyls (PCBs) and halogenated flame retardants (HFRs) in soil, water, reed, air and dust samples collected from the e-waste recycling region in Ziya Town, Northern China. The results showed that the concentrations of PCBs reached relative high level in environmental matrices in the study area. HFRs including polybrominated diphenyl ethers (PBDEs), dechlorane plus (DP), allyl 2,4,6-tribromophenyl ether (ATE), tetrabromoethylcyclohexane (TBECH), pentabromotoluene (PBT), pentabromoethylbenzene (PBEB), 2,3-dibromopropyl 2,4,6-tribromophenyl ether (DPTE), 1,2-bis-(2,4,6-tribromophenoxy) ethane (BTBPE) and so on were also widely detected in multi-matrices. Long-range atmospheric transport (LRAT) potentials of non-BDE HFRs were assessed to address the LRAR abilities of these compounds. Analysis of soil–air exchange of PCBs and HFRs showed that soil acted as a secondary source to the atmosphere only for a few low molecular weight compounds, while the direction of the flux of most detected chemicals was from air to soil.     

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.     

Improved traceability of Shiga-toxin-producing <Emphasis Type="Italic">Escherichia coli</Emphasis> using CRISPRs for detection and typing

Among strains of Shiga-toxin-producing Escherichia coli (STEC), seven serogroups (O26, O45, O103, O111, O121, O145, and O157) are frequently associated with severe clinical illness in humans. The development of methods for their reliable detection from complex samples such as food has been challenging thus far, and is currently based on the PCR detection of the major virulence genes stx1, stx2, and eae, and O-serogroup-specific genes. However, this approach lacks resolution. Moreover, new STEC serotypes are continuously emerging worldwide. For example, in May 2011, strains belonging to the hitherto rarely detected STEC serotype O104:H4 were identified as causative agents of one of the world’s largest outbreak of disease with a high incidence of hemorrhagic colitis and hemolytic uremic syndrome in the infected patients. Discriminant typing of pathogens is crucial for epidemiological surveillance and investigations of outbreaks, and especially for tracking and tracing in case of accidental and deliberate contamination of food and water samples. Clustered regularly interspaced short palindromic repeats (CRISPRs) are composed of short, highly conserved DNA repeats separated by unique sequences of similar length. This distinctive sequence signature of CRISPRs can be used for strain typing in several bacterial species including STEC. This review discusses how CRISPRs have recently been used for STEC identification and typing.     

Depth-dependence and monthly variability of charophyte biomass production: consequences for the precipitation of calcium carbonate in a shallow <Emphasis Type="Italic">Chara</Emphasis>-lake

The month-to-month variability of biomass and CaCO₃ precipitation by dense charophyte beds was studied in a shallow Chara-lake at two depths, 1 and 3 m. Charophyte dry weights (d.w.), the percentage contribution of calcium carbonate to the dry weight and the precipitation of CaCO₃ per 1 m² were analysed from May to October 2011. Physical-chemical parameters of water were also measured for the same sample locations. The mean dry weight and calcium carbonate precipitation were significantly higher at 1 m than at 3 m. The highest measured charophyte dry weight (exceeding 2000 g m^?2) was noted at 1 m depth in September, and the highest CaCO₃ content in the d.w. (exceeding 80 % of d.w.) was observed at 3 m depth in August. The highest CaCO₃ precipitation per 1 m² exceeded 1695 g at 1 m depth in August. Significant differences in photosynthetically active radiation (PAR) were found between 1 and 3 m depths; there were no significant differences between depths for other water properties. At both sampling depths, there were distinct correlations between the d.w., CaCO₃ content and precipitation and water properties. In addition to PAR, the water temperature and magnesium and calcium ion concentrations were among the most significant determinants of CaCO₃ content and d.w. The results show that light availability seems to be the major factor in determining charophyte biomass in a typical, undisturbed Chara-lake. The study results are discussed in light of the role of charophyte vegetation in whole ecosystem functioning, with a particular focus on sedimentary processes and the biogeochemical cycle within the littoral zone.     

Increasing CACNA1C expression in placenta containing high Cd level: an implication of Cd toxicity

Cadmium (Cd) has known to produce many adverse effects on organs including placenta. Many essential transporters are involved in Cd transport pathways such as DMT-1, ZIP as well as L-VDCC. Fourteen pregnant women participated and were divided into two groups: high and low Cd-exposed (H-Cd, L-Cd) groups on the basis of their residential areas, Cd concentrations in the blood (B-Cd), urine (U-Cd), and placenta (P-Cd). The results showed that the B-Cd and U-Cd were significantly increased in H-Cd group (p < 0.05). Interestingly, the P-Cd in H-Cd group was elevated (p < 0.05) and positively related to their B-Cd and U-Cd values (p < 0.05). However, the mean cord blood Cd (C-Cd) concentration in H-Cd group was not significantly increased about 2.5-fold when comparing to L-Cd group. To determine the Cd accumulation in placental tissues, metallothionein-1A (MT-1A) and metallothionein-2A (MT-2A) expressions were used as biomarkers. The results revealed that mean MT-1A and MT-2A mRNAs and MT-1/2 proteins were up-regulated in H-Cd group (p < 0.05). In addition, the Ca channel alpha 1C (CACNA1C) mRNA and protein expressions were noticeably elevated in H-Cd group (p < 0.05). From these findings, we suggested that CACNA1C might be implicated in Cd transport in human placenta.