Recent Advances in Boron Nitride Based Hybrid Polymer Nanocomposites

Boron nitride (BN) is an eminent inorganic compound having many interesting characteristics such as improved oxidation resistance, mechanical strength, good thermal conductivity (TC), higher bandgap, high chemical stability, thermal stability, high hydrophobicity, and electrical insulation. The use of BN as a filler in polymers is a well-established strategy to tailor the properties of polymer composites. Recent studies depict an interesting urge to reap the synergistic effect of various nanofillers with BN in the form of hybrids. Hence the consolidation of the works on BN based hybrid fillers would definitely attract researchers so that these new filler systems could be transformed into useful polymer nanocomposites in future. This review article focuses on the synthesis and characterization of various boron nitride based hybrids in detail. Moreover, the review also throws light on different BN hybrid reinforced polymer nanocomposites (PNCs) and their thermal, electrical, electronic as well as biomedical applications in a detailed manner. Thus the review anticipates serving as a tool toward understanding the recent trends in the field of boron nitride hybrid based ternary polymer composites.     

Hemp seed oil: Minor components and oil quality

Owing to its high content of omega‐6/omega‐3 fatty acids and bioactive minor components with antioxidant activities, hemp seed oil is now recognized for its health benefits by a large number of consumers. This paper primarily discusses the profile of minor components in hemp seed oil and their beneficial and adverse effects on oil quality. While tocopherols, polyphenols and phytosterols prevent oxidative deterioration of hemp seed oil, the high amount of chlorophyll can be detrimental to oil quality.     

Evaluation of kinetics and transport mechanism of solvents through natural rubber composites containing organically modified gadolinium oxide

The solvent transport properties of the prepared composites were analysed using solvents of varying cohesive energy density and the effect of both modified as well as unmodified filler on the sorption and diffusion behaviour of NR vulcanisates has been investigated. It is found that the equilibrium uptake decreases with increase in filler content, as anticipated owing to the restrictions offered by the filler for solvents to diffuse into the polymer matrix. The mechanism of transport in natural rubber composites was carefully tracked and it was found to exhibit an anomalous mode of solvent transport where the polymer relaxation is in par with the rate of diffusion. Theoretical modelling of the swelling parameters was done and the results were found to be in agreement with existing models. The excellent swelling resistance coupled with the simultaneous improvement in mechanical properties would definitely pave way for the utilisation of these composites as barrier membranes.     

MIXED CONVECTION INDUCED BY MEMS-BASED THERMAL SHEAR STRESS SENSORS

The effect of buoyancy caused by heat generation from a microelectromechanical system (MEMS)-based thermal shear stress sensor is investigated. Due to the small size and relatively low power consumption of such sensors, the buoyancy effect on the overall flow structure is generally negligible. However, its impact on the flow variables such as shear stresses can be significant because such quantities are local and depend on the gradients of the velocity profile next to the sensor. Due to the small dimension of the MEMS sensor, a multiscale modeling approach is adopted to examine the effect of buoyancy on the velocity and wall shear stress profiles. Full-length channel computations are initially performed with finer resolution near the sensor region. Using the boundary conditions derived from the full-length computations, another simulation is performed concentrating on a small region near the shear stress sensor. Based on the temperature distribution in the region of the sensor, the effective thermal length scale is several times the streamwise dimension of the sensor. For a state-of-the-art MEMS sensor dimension of 200\,\mu {\bf m} , the effect of buoyancy on the accuracy of shear stress measurement can be noticeable.     

Role of solvent interaction parameters in tailoring the properties of chlorobutyl rubber nanocomposites

Chlorobutyl rubber, a special class of butyl rubber, which exhibits superior air impermeability, is the elastomer of choice for the inner tubes and liners of tires. Chlorobutyl rubber nanocomposites containing layered silicates were prepared using solvents with varying cohesive energy density and the effect of solvent–clay and solvent–rubber parameters in determining the properties of the nanocomposites were studied. The nanocomposites so prepared were characterized by X‐ray diffraction, scanning electron microscopy and transmission electron microscopy. The results were interpreted with the help of thermodynamic concepts and a correlation between the mechanical properties of the nanocomposites and the difference in the interaction parameters was done. The same correlation was then applied to gas barrier properties and trends identical to mechanical properties were observed. Thereby it was shown that a strong relationship exists between properties of a system and solubility parameters in solution mixing process. POLYM. COMPOS., 37:353–359, 2016. © 2014 Society of Plastics Engineers     

Mechanical,thermophysical, and diffusion properties of TiO2‐filled chlorobutyl rubber composites

The mechanical and thermophysical properties of TiO₂‐filled chlorobutyl rubber composites were investigated. These materials exhibited enhanced mechanical properties such as increased modulus, tensile strength, and hardness. The morphology of filler dispersion in the matrix was analyzed by scanning electron microscopy and atomic force microscopy. Moreover, the effect of TiO₂ content on the molecular transport of solvents was examined by means of degree of swelling, volume fraction of rubber, penetration rate of solvent, mean diffusion coefficient, etc. A periodic method was used to estimate the thermophysical behavior of samples. It was shown that the thermal conductivity and diffusivity of composites increase with increasing of TiO₂ filler content. Finally, the utilization of the material as effective chemical protective clothing against volatile organic chemicals was analyzed. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Effect of lysine incorporation,annealing and heat moisture treatment alone and in combination on the physico-chemical,retrogradation, rheological properties and in vitro digestibility of kithul (Caryota urens L.) starch

Physico-chemical, retrogradation, rheological properties and in vitro digestibility of lysine incorporated kithul starch modified by annealing, heat moisture treatment and its combinations were studied. LS-AHMT (annealed-heat moisture treated lysine incorporated kithul starch) exhibited lowest amylose leaching. LS-AHMT showed significantly (P ≤ 0.05) higher relative crystallinity. LS-ANS (annealed lysine incorporated kithul starch), LS-HMT (heat moisture treated lysine incorporated kithul starch) and LS-AHMT formed more weak gel by the effect of annealing, heat moisture treatment and its combination. LS-AHMT showed lowest pasting viscosities, G′ and G″ values among the modified kithul starch, which indicates its lower retrogradation properties. In vitro digestibility of kithul starch decreased after modifications and LS-ANS, LS-HMT and LS-AHMT showed significantly higher resistant starch content. The current study showed that annealing, heat moisture treatment and its combination on NS-LS (lysine incorporated kithul starch) effectively modified kithul starch properties.     

Segmentation of tumor using PCA based modified fuzzy C means algorithms on MR brain images

In the field of medical sciences, automatic detection of tumor using magnetic resonance (MR) brain images is a major research area. The goal of the proposed work is to identify the tumors in MR images using segmentation methods and to locate the affected regions of the brain more accurately. Medical images have vast information but they are difficult to examine with lesser computational time. An innovative process is proposed to extract tumor cells using the discrete wavelet transform (DWT). After extracting features with DWT feature reduction is carried out with the principal component analysis (PCA). Modified fuzzy C means (MFCM) technique is used for segmenting the tumor cells. The efficiency of the proposed method to identify different abnormalities in real MR images for intracranial neoplasm detection, tuberculoma, and bilateral thalamic fungal granulomas identification is tested. The results obtained are shown in-terms of Accuracy, Dice Similarity Index (DSI), and Jaccard Index (JI) measures. The performance of the proposed method is tested in terms of performance measures like Accuracy, DSI, and JI. These results are compared with the conventional fuzzy C means (FCM) method.     

Effect of inhibitory extracts derived from liquid smoke combined with postprocess pasteurization for control of Listeria monocytogenes on ready-to-eat meats

Surface pasteurization was examined in combination with low-phenolic antimicrobial extracts derived from liquid smoke to inhibit and prevent the growth of Listeria monocytogenes during the shelf life of ready-to-eat meats. In preliminary trials with retail frankfurters, one smoke derivative (2-min dip) produced a 0.3-log reduction of L. monocytogenes and a 1-min in-bag pasteurization (73.9 degrees C) produced a 2.9-log reduction, whereas a combination of the two treatments produced a 5.3-log reduction that resulted in no detectable Listeria by week 3 under accelerated shelf-life conditions (10 degrees C). In trials with frankfurters manufactured without lactate or diacetate that were treated with a shortened 1-s dip, this smoke extract and one with reduced smoke flavor and color both produced a > 4.5-log reduction of L. monocytogenes on frankfurters when heated at 73.9 degrees C for 1 min, with no recoverable Listeria detected for 10 weeks when stored at 6.1 degrees C. When deli turkey breast chubs manufactured without lactate, diacetate, or nitrite were treated with a 1-s dip in combination with radiant-heat pasteurization (270 degrees C), growth of L. monocytogenes was retarded but not prevented. However, in a similar study in which smoke extract treatment of deli turkey breast was combined with in-bag postpackage pasteurization (water submersion at 93.3 degrees C), a 60-, 45-, or even 30-s heat treatment resulted in a 2- to 3-log reduction of L. monocytogenes, with no growth on the meat during 10 weeks of storage at 6.1 degrees C. These findings indicate that reduced-acid low-phenolic antimicrobial liquid smoke derivatives combined with surface pasteurization are capable of reducing or preventing growth of L. monocytogenes to meet the criteria for the U.S. Department of Agriculture Food Safety and Inspection Service Alternative 1 process for ready-to-eat deli meat products manufactured without lactate or diacetate.     

Effect of inhibitory liquid smoke fractions on Listeria monocytogenes during long-term storage of frankfurters

Listeria monocytogenes is a potential health hazard that sometimes finds harborage in facilities that manufacture ready-to-eat meats, including frankfurters. Our objectives were to examine the effect of select liquid smoke extracts on control of L. monocytogenes on frankfurters. Frankfurters were either obtained locally at retail (containing lactate-diacetate) or manufactured for us in-house or by a local processor (without added lactate-diacetate). In challenge studies of retail franks containing lactate-diacetate, low levels of L. monocytogenes were able to increase by 2 to 8 log on 5 of 10 brands tested when held at 1.6 degrees C (35 degrees F). Treatments with liquid smoke extracts were able to reduce and control growth of L. monocytogenes on the most permissive franks for 10 weeks when treated for as long as 90 s to as little as 5 s versus untreated controls. Effective control of L. monocytogenes was also obtained when dipped for as short as 1 s or when dropped through an atomized mist produced by a pressurized spray canister. Frankfurters manufactured without lactate-diacetate by a large commercial manufacturer of franks were sprayed with liquid smoke by using a commercial device as they exited the peeler. When inoculated at three different levels (10(1), 10(2), and 10(3) CFU) with a four-strain cocktail of L. monocytogenes and stored at 6 degrees C (43 degrees F), the smoke-treated samples again demonstrated effective control of L. monocytogenes relative to untreated control samples. Frankfurters produced in-house without lactate-diacetate and treated while still in the casing also showed suppression of Listeria compared with controls. The data show that surface application of liquid smoke extracts by dipping or spraying may inhibit the growth of L. monocytogenes on frankfurters during shelf life and should facilitate a claim as an alternative 2, and possibly alternative 1, process for (U.S. Food and Drug Administration) hazard analysis and critical control point purposes.