Synthesis and kinetics of ascorbic acid initiated graft copolymerized delignified cellulosic fiber

Graft copolymerization of delignified Grewia optiva fiber with methyl methacrylate (MMA) as vinyl monomer was attempted using ascorbic acid/H₂O₂ as redox initiator. Different reaction conditions affecting the grafting percentage (P_g) were optimized to get the maximum P_g (32.56%) of MMA onto delignified Grewia optiva fibers. Grafted and ungrafted fibers were subsequently subjected to evaluation of physico‐chemical properties such as swelling behavior and acid and alkali resistance. The rate expression for the grafting reaction (R_g = k [ASC]^0.12 [H₂O₂]^0.53 [MMA]^0.05) was evaluated and a suitable mechanism for grafting was suggested. The overall activation energy of the copolymerization reaction was found as 11.97 kJ mol^?1 at temperature range 25–65°C. Further, morphological and structural analysis of raw, delignified, and grafted Grewia optiva‐g‐poly(MMA) were studied by using Fourier‐transform Infrared spectroscopy, scanning electron microscopy, X‐ray diffraction, and thermogravimetric analysis.The tensile properties of grafted and ungrafted fiber samples were also reported. POLYM. ENG. SCI., 55:474–484, 2015. © 2014 Society of Plastics Engineers     

Biodegradable biocomposites from poly(butylene adipate‐co‐terephthalate) and miscanthus: Preparation,compatibilization, and performance evaluation

Miscanthus fibers reinforced biodegradable poly(butylene adipate‐co‐terephthalate) (PBAT) matrix‐based biocomposites were produced by melt processing. The performances of the produced PBAT/miscanthus composites were evaluated by means of mechanical, thermal, and morphological analysis. Compared to neat PBAT, the flexural strength, flexural modulus, storage modulus, and tensile modulus were increased after the addition of miscanthus fibers into the PBAT matrix. These improvements were attributed to the strong reinforcing effect of miscanthus fibers. The polarity difference between the PBAT matrix and the miscanthus fibers leads to weak interaction between the phases in the resulting composites. This weak interaction was evidenced in the impact strength and tensile strength of the uncompatibilized PBAT composites. Therefore, maleic anhydride (MAH)‐grafted PBAT was prepared as compatibilizer by melt free radical grafting reaction. The MAH grafting on the PBAT was confirmed by Fourier transform infrared spectroscopy. The interfacial bonding between the miscanthus fibers and PBAT was improved with the addition of 5 wt % of MAH‐grafted PBAT (MAH‐g‐PBAT) compatibilizer. The improved interaction between the PBAT and the miscanthus fiber was corroborated with mechanical and morphological properties. The compatibilized PBAT composite with 40 wt % miscanthus fibers exhibited an average heat deflection temperature of 81 °C, notched Izod impact strength of 184 J/m, tensile strength of 19.4 MPa, and flexural strength of 22 MPa. From the scanning electron microscopy analysis, better interaction between the components can be observed in the compatibilized composites, which contribute to enhanced mechanical properties. Overall, the addition of miscanthus fibers into a PBAT matrix showed a significant benefit in terms of economic competitiveness and functional performances. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45448.     

Optimization of tensile properties thermoplastic blends from soy and biodegradable polyesters: Taguchi design of experiments approach

Soy meal-based biodegradable blends were prepared by melt extrusion process. The effects of denaturants, i.e., urea and sodium sulfite and plasticizer (glycerol) and polyester type (polybutylene succinate, polycaprolactone, polybutylene adipate terephthalate) on tensile strength and elongation at break were investigated using a Taguchi experimental design approach. The results showed that the sodium sulfite had little or no effect on final properties of the blends. Also, biodegradable polyester type had significant effect on the tensile strength and elongation at break of the blends prepared. The predicted values and experimental were found to be in tune with each other. The chemical structure and morphology of the optimum sample was probed by FT-IR spectroscopy and scanning electron microscopy (SEM). Also, the results provided an insight into how important the plasticization and destructurization of soy protein to obtain the blends with desired mechanical properties.     

Patterns in melanocytic lesions: impact of the geometry on growth and transport inside the epidermis

In glabrous skin, nevi and melanomas exhibit pigmented stripes during clinical dermoscopic examination. They find their origin in the basal layer geometry which periodically exhibits ridges, alternatively large (limiting ridges) and thin (intermediate ridges). However, nevus and melanoma lesions differ by the localization of the pigmented stripes along furrows or ridges of the epidermis surface. Here, we propose a biomechanical model of avascular tumour growth which takes into account this specific geometry in the epidermis where both kinds of lesions first appear. Simulations show a periodic distribution of tumour cells inside the lesion, with a global contour stretched out along the ridges. In order to be as close as possible to clinical observations, we also consider the melanin transport by the keratinocytes. Our simulations show that reasonable assumptions on melanocytic cell repartition in the ridges favour the limiting ridges of the basal compared with the intermediate ones in agreement with nevus observations but not really with melanomas. It raises the question of cell aggregation and repartition of melanocytic cells in acral melanomas and requires further biological studies of these cells in situ.     

Study of the effect of processing conditions on the co‐injection of PBS/PBAT and PTT/PBT blends for parts with increased bio‐content

This work studies the effect of processing parameters on mechanical properties and material distribution of co‐injected polymer blends within a complex mold shape. A partially bio‐sourced blend of poly(butylene terephthalate) and poly(trimethylene terephthalate) PTT/PBT was used for the core, with a tough biodegradable blend of poly (butylene succinate) and poly (butylene adipate‐co‐terephthalate) PBS/PBAT for the skin. A ½ factorial design of experiments is used to identify significant processing parameters from skin and core melt temperatures, injection speed and pressure, and mold temperature. Interactions between the processing effects are considered, and the resulting statistical data produced accurate linear models indicating that the co‐injection of the two blends can be controlled. Impact strength of the normally brittle PTT/PBT blend is shown to increase significantly with co‐injection and variations in core to skin volume ratios to have a determining role in the overall impact strength. Scanning electron microscope images were taken of co‐injected tensile samples with the PBS/PBAT skin dissolved displaying variations of mechanical interlocking occurring between the two blends. © 2014 The Authors Journal of Applied Polymer Science Published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41278.     

Application of electrostatic precipitator in collection of smoke particles from hospital wastes combustion

The paper reports the development and implementation of a cost-effective electrostatic precipitator (ESP) prototype for the medical wastes incinerator of university hospital centre (CHU) of Sidi-Bel-Abbes, using a water washing system for cleaning electrodes. The impact of medical waste incineration on human health is a topical debate. The incineration process is a safe mode of disposal [OK] of such waste, but it is not an effective solution and needs a pollution control system. Generally, in Africa, cost is the major constraint for manufacturers and users. A half-scale ESP model was initially used for an experimental study in the laboratory. Thereafter, a full-scale model was produced and installed for the incinerator based on the optimal values obtained from this preliminary study.     

Statistical design of sustainable composites from poly(lactic acid) and grape pomace

Biocomposites from poly(lactic acid) (PLA) and grape pomace (GP) were created via injection molding to examine the effects of GP in a PLA matrix. To optimize the mechanical performance the biocomposites were compatibilized with maleic anhydride grafted PLA (MA-g-PLA). The objective of this work was to create a model that could accurately predict the mechanical properties of GP/PLA biocomposites. A region of feasibility for the biocomposites was determined using a statistical design of experiments. Linear regression was used to model the mechanical performance and predicted results with an error of 10% for both tensile and flexural strength and 16% for impact strength. The model was verified with a biocomposite of PLA/GP/MA-g-PLA with a ratio of 62/36/2. This biocomposite had a tensile strength, flexural modulus, and impact strength of 25.8 MPa, 40.0 MPa, and 18.4 J/m, respectively. It was found that a linear model can accurately predict the mechanical properties of PLA/GP/MA-g-PLA biocomposites.     

A New Approach to Supertough Poly(lactic acid): A High Temperature Reactive Blending

A novel approach to PLA toughening is proposed in this study. Poly(lactic acid) (PLA) is toughened using poly(ethylene‐n‐butylene‐acrylate‐co‐glycydyl methacrylate) (EBA‐GMA) as a reactive compatibilizer with the aid of an epoxy‐based chain extender. It is found that the toughening effect of EBA‐GMA in the binary blend investigated is strongly influenced by blending temperature. Blending at high temperatures which are non‐typical for PLA processing (over 250 °C) allows toughness to be increased by an order of magnitude when compared to the toughness of blends prepared at low temperatures (below 200 °C). This effect is attributed to a combination of factors, namely an increasing rate of reactive bonding between PLA and EBA‐GMA at elevated temperatures and enhanced interfacial adhesion between PLA and EBA‐GMA phases. DSC studies show that PLA/EBA‐GMA bonding on the interface acts as an efficient nucleator for PLA. The nucleation ability of the PLA/EBA‐GMA interface strongly depends on blend processing temperature and gradually increases with increasing blending temperature. The PLA/EBA‐GMA interface shows its highest nucleation ability at 250 °C.

     

Classification of multifrequency polarimetric SAR imagery using adynamic learning neural network

A practical method for extracting microwave backscatter for terrain-cover classification is presented. The test data are multifrequency (P, L, C bands) polarimetric SAR data acquired by JPL over an agricultural area called “Flevoland”. The terrain covers include forest, water, bare soil, grass, and eight other types of crops. The radar response of crop types to frequency and polarization states were analyzed for classification based on three configurations: 1) multifrequency and single-polarization images; 2) single-frequency and multipolarization images; and 3) multifrequency and multipolarization images. A recently developed dynamic learning neural network was adopted as the classifier. Results show that using partial information, P-band multipolarization images and multiband hh polarization images have better classification accuracy, while with a full configuration, namely, multiband and multipolarization, gives the best discrimination capability. The overall accuracy using the proposed method can be as high as 95% with a total of thirteen cover types classified. Further reduction of the data volume by means of correlation analysis was conducted to single out the minimum data channels required. It was found that this method efficiently reduces the data volume while retaining highly acceptable classification accuracy