Recent Advances in Transition Metal-Based Catalysts for Ethylene Copolymerization with Polar Comonomer

The synthesis of polar functionalized polyolefin (PFP) offers improvement in mixing properties, polymer surface, and rheological properties with the potential of upgraded polyolefins for modern and ingenious applications. The synthesis of PFP from metal-based catalyzed olefin (non-polar in nature) copolymerization with polar comonomers embodies energy-efficient, atom-efficient, and apparently an upfront methodology. Despite their outstanding success during conventional polymerization of olefin, 3^rd and 4^th group (early transition metal)-based catalysts, owing to their electrophilic nature, face challenges mainly due to Lewis basic sites of the polar monomers. On the contrary, late transition metal-based catalysts have also made progress, in recent years, for PFP synthesis. The recent past has also witnessed several advancements in the development of dominating palladium-based catalysts while their lower resistance towards ligand functional groups has limited the practical application of abundant and cheaper nickel-based catalysts. However, the relentless efforts of the scientific community, during the past half-decade, have indicated rigorous progress in the development of nickel-based catalysts for PFP synthesis. In this review, we have abridged the recent research trends in both early as well as late transition metal-based catalyst development. Furthermore, we have highlighted the role of transition metal-based catalysts in influencing the polymer properties.

Engineered biochar supported layered double hydroxide-cellulose nanocrystals composite-: Synthesis, characterization and azo dye removal performance

In this work, engineered biochar decorated layered double hydroxides and cellulose nanocrystals (B-CuFe-CNC) biocomposites were synthesized by the facile ultrasonicated-co-precipitation technique. The biocomposite was investigated for purification of Eriochrome Black T (EBT) dye from water. The characterization results showed that the presence of CNC in biochar-layered double hydroxides resulted in a two-dimensional rod-like structure with excellent crystallinity, improved surface functionalities, and provides an attractive platform for the enhanced adsorption of azo anionic dye molecules. The adsorption system was appropriately demonstrated by the BBD-RSM (R² > 0.994). The biocomposite exhibited higher EBT adsorption in the acidic pH range (2-5) due to strong electrostatic and chemical interactions. The kinetic and isotherm results were well demonstrated by pseudo-second order, Freundlich, and Redlich Peterson models. The maximum adsorption capacity of biocomposite was 876.2 mg/g achieved within 45 min. The spectroscopic analyses imply that the high removal of EBT by biocomposite is mainly governed by electrostatic attraction, hydrogen bonding, and chemical/metal complexation mechanisms. The biocomposite maintained high EBT removal after six successive adsorption cycles and excellent dye adsorption in the different water matrices. The results suggest that tailoring biochar properties with layered double hydroxide and CNC is a promising way for the enhanced removal of dye contaminants from wastewater.

Effect of the Surface Functionalization of Graphene and MWCNT on the Thermodynamic, Mechanical and Electrical Properties of the Graphene/MWCNT-PVDF Nanocomposites

The nanocomposites of poly(vinylidene fluoride) (PVDF) with pristine graphene nanoflakes (GNF) and a multi-wall carbon nanotube (MWCNT) were prepared by the solution casting method. Additionally, the GNF and MWCNT were functionalized by acid treatment, and nanocomposites of the acid-treated MWCNT/GNF and PVDF were prepared in the same method. The effect of the acid treatment of MWCNT and GNF on the mechanical, thermal and thermo-oxidative stability and the thermal conductivity of the MWCNT/GNF-PVDF nanocomposites was evaluated, and the results were compared with the untreated MWCNT/GNF-PVDF nanocomposites. In both cases, the amount of GNF and MWCNT was varied to observe and compare their thermal and mechanical properties. The functionalization of the GNF or MWCNT resulted in the change in the crystallization and melting behavior of the nanocomposites, as confirmed by the differential scanning calorimetry analysis. The addition of the functionalized GNF/MWCNT led to the improved thermal stability of the PVDF nanocomposites compared to that of the non-functionalized GNF/MWCNT-PVDF nanocomposites. The thermal and electrical conductivity of the functionalized and non-functionalized GNF/MWCNT-PVDF composites were also measured and compared. The functional groups, crystal structure, microstructure and morphology of the nanocomposites were characterized by Fourier transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively.

Effect of Fabrication Method on the Thermo Mechanical and Electrical Properties of Graphene Doped PVDF Nanocomposites

Nanocomposites of poly (vinylidene fluoride) PVDF with graphene nanoflakes (GNF) were prepared using two different routes. Initially, a mix-melting method was used to prepare composites, and their thermal and mechanical properties were evaluated to choose the better method for future experiment and properties investigation. Then, nanocomposite films were prepared by a simple solution-casting technique using a PVDF/graphene solution. In both cases, the amount of graphene was varied to observe and to compare their thermal and mechanical properties. The addition of graphene to the PVDF matrix resulted in changes in the crystallization and melting behaviors as confirmed by DSC analyses. Increasing the graphene content led to improved thermal stability of the PVDF nanocomposites prepared using both methods. Improvements in mechanical properties by the addition of graphene were also observed. Better performance was observed by the nanocomposites prepared by a mix-melting technique suggesting better dispersion and strong interface bonding between PVDF and graphene particles. Thermal and electrical conductivity were measured and compared. Microstructure and morphology were characterized using FTIR, XRD, and SEM analyses.

Enhanced removal of Eriochrome Black T from water using biochar/layered double hydroxide/chitosan hybrid composite: Performance evaluation and optimization using BBD-RSM approach

In this research work, a novel hybrid composite consisting of biochar (B), layered double hydroxide (CuFe) and chitosan (CS) (B-CuFe-CS) was produced using an ultrasonication-assisted co-precipitation method. The resultant composite was employed for adsorptive removal of Eriochrome black T (EBT) from water. Physicochemical characterization indicated that the B-CuFe-CS containing 10 wt % CS exhibited a heterogeneous structure with better crystallographic and textural characteristics. The B-CuFe-CS with abundant surface functionalities (-CO, -C-O, -OH, -NO_3, and MMO), facilitates faster and enhanced removal of the EBT. The kinetic results showed better fitting to the pseudo-second order model, and equilibrium was achieved within 30 min. Equilibrium data was well explained by Langmuir and Redlich Peterson isotherm models (R² > 0.98), indicating the EBT removal onto B-CuFe-CS followed monolayer adsorption. The maximum adsorption capacity was 806.4 mg/g, which was higher than pristine B-CuFe (476.19 mg/g) and many other adsorbents. The spectroscopic analysis (FTIR and XPS) and experimental results suggested that EBT adsorption is mainly governed by electrostatic, chemical and anion-exchange interactions. It is evident from these results that coupling B-CuFe composite with bio-filler (chitosan) resulted in an efficient bio-adsorbent to effectively purify dye-contaminated water streams.

Thermal Degradation Kinetics Analysis of Ethylene-Propylene Copolymer and EP-1-Hexene Terpolymer

LLDPE is a less crystalline polymer with vast industrial and domestic applications. It is imperative to understand the synthesis, processing conditions, and thermal degradation mechanism of the co- as well as terpolymers. This paper reports the in-situ synthesis and thermal degradation studies of the ethylene-propylene copolymer and ethylene-propylene-1-hexene terpolymer and its nanocomposite with ZnAL LDH sheets. The 1-hexene dosing during the in-situ process influenced the product yield and immensely affected the thermal stability of the resultant polymer. One milliliter 1-hexene in-situ addition increased the product yield by 170 percent, while the temperature at 10 percent weight loss in TGA was dropped by about 60 °C. While only 0.3 weight percent ZnAL LDH addition in the terpolymer improved the thermal stability by 10 °C. A master plot technique and combined kinetics analysis (CKA) were deployed to access the thermal degradation mechanism of the synthesized polymers.

Sustainable wastewater treatment by biochar/layered double hydroxide composites: Progress, challenges, and outlook

Biochar/layered double hydroxide (LDH) composites have gained considerable attention in recent times as low-cost sustainable materials for applications in water treatment. This paper critically evaluates the latest development in applications of biochar/LDH composites in water treatment with an emphasis on adsorption and catalytic degradation of various pollutants. The adsorption of various noxious contaminants, i.e., heavy metals, dyes, anions, and pharmaceuticals onto biochar/LDH composites are described in detail by elaborating the adsorption mechanism and regeneration ability. The synergistic effect of LDH with biochar exhibited significant improvement in specific surface area, surface functional groups, structure heterogeneity, stability, and adsorption characteristics of the resulting biochar/LDH composites. The major hurdles and challenges associated with the synthesis and applications of biochar/LDH composites in water remediation are emphasized. Finally, a roadmap is suggested for future research to assure the effective applications of biochar/LDH composites in water purification.

Degree of conversion of two self-adhesive resin luting cements through different lengths of fiber post

PURPOSE

To evaluate the degree of conversion (DoC) of self-adhesive resin luting cements when irradiated through different fiber post lengths.

METHODS

A total of 60 teeth were sectioned to achieve lengths of 4 mm, 7 mm, and 10 mm, while 60 fiber posts were trimmed to give 3 mm, 6 mm, and 9 mm lengths. Post space was created to accommodate the fiber post and 1 mm of luting cement apically. Two self-adhesive resin luting cements (Multilink Speed and RelyX U200) were used. A total of four cycles of 20 s irradiation was done with an attenuated total reflectance Fourier transform infrared spectroscopy reading between each cycle.

RESULTS

The mean ± standard deviation DoC achieved with a light-emitting diode and quartz tungsten halogen for Multilink Speed was 67.4 ± 2.7% and 72.4 ± 4.0%, respectively, while for RelyX U200, the corresponding values were 56.5 ± 2.7% and 62.0 ± 3.8%, respectively. For Multilink Speed, there was no significant difference between the control and the 3 mm group, while for RelyX U200, no significant difference was found between the 6 mm and 9 mm groups. All the other groups showed significant differences.

CONCLUSION

The DoC reduced as the post length increased.

Sewage Sludge ZnCl2-Activated Carbon Intercalated MgFe-LDH Nanocomposites: Insight of the Sorption Mechanism of Improved Removal of Phenol from Water

Keywords: sludge-activated carbon; MgFe layered double hydroxide; nanocomposite materials; phenol aqueous uptake; mechanistic studies; reusability performance.

Effect of Different Levels of Multienzymes on Immune Response, Blood Hematology and Biochemistry, Antioxidants Status and Organs Histology of Broiler Chicks Fed Standard and Low-Density Diets

This study was executed to investigate the effect of supplementing three multienzyme levels (0, 0. 1, and 0.2%) with two types of diet [standard diet (SD) vs. low-density diet (LDD)] on immune response, blood hematology and biochemistry, antioxidant status, and organ histology of broilers during 1–38 days of age. A total of 216 unsexed 1-day-old Arbor Acres broiler chicks were randomly distributed, on a factorial design (2 × 3), to six treatments each with six replicates. There were six chicks per replicate. Results showed that LDD significantly decreased body weight gain (BWG) of broilers, but did not affect the European Production Efficiency Index (EPEI). Addition of multienzymes at both levels (0.1 and 0.2%) significantly increased BWG and improved EPEI, compared to the control diet. Alanine aminotransferase (ALT), aspirate aminotransferase (AST), malondialdehyde (MDA), lymphocyte, lymphocyte transformation test (LTT), and phagocyte activity (PA) were significantly higher for LDD than the SD, but eosinophil was lower. Supplementation of multienzymes significantly decreased ALT, AST, and MDA, compared to the control group, but increased packed cell volume (PCV), hemoglobin (Hgb), lymphocytes, and monocytes. Immune organs, such as spleen, thymus, and the bursa of Fabricius were significantly increased with multienzyme supplementation. It could be concluded that multienzyme supplementation at either 0.1 or 0.2% to SD or LDD improved EPEI and immune status of broiler chicks.

Blood Hematological and Biochemical Constituents, Antioxidant Enzymes, Immunity and Lymphoid Organs of Broiler Chicks Supplemented with Propolis, Bee Pollen and Mannan Oligosaccharides Continuously or Intermittently

This study investigate the effect of bee pollen (BP) and/or propolis (Pro) as an alternative to Mannan oligosaccharides (Bio-MOS, a hydrolyzed yeast with natural and artificial flavors Alltech Inc) when given continuously or intermittently on antioxidant enzymes, immunity, weight and morphology of lymphoid organs of broilers. Thus, 324 unsexed one-day-old Arbor Acres broilers were randomly distributed into nine treatment groups, each replicated 6 times of 6 birds per replicate. The chicks were kept in wire cages and fed the same basal diet and were submitted to the following treatments: control without supplementation (control) or supplemented with BP at 300 mg, Pro at 300 mg, BP+Pro at 300 mg each and Bio-MOS at 0.5 g/kg diet. Each supplemented group was subdivided into two subgroups in which the additives were supplied continuously or intermittently. In the continuously supplemented groups, supplementations were given from one till 36 days of age, and in the intermittently supplemented groups, the administration was only three days before, on the day of and day after vaccination. The BP and Pro supplied continuously or intermittently was equally potent for improving immunity, antioxidant enzymes similar to Bio-MOS. All supplements supplied either continuously or intermittently resulted a significantly higher thymus (P < .04) and bursa weights (P < .001) than the control group. Combining BP with Pro resulted in a further increase in thymus weights and small follicle diameter compared to the control group. In addition, thymus percentage in the group received BP+Pro showed a further increase compared to the control and Pro supplemented intermittently. Bio-MOS, when supplied continuously or intermittently, resulted in the greatest response in splenic lymphoblasts. Supplementation with either BP or Pro intermittently, is adequate to promote health and immune response of broiler chicks, with 40% saving of supplementation costs.

Effect of aluminum nitride concentration on different physical properties of low density polyethylene based nanocomposites

In this study, blends of low-density polyethylene (LDPE)/aluminum nitride (AlN) ceramic nanocomposites have been prepared through melt blending technique. Increased loading of AIN leads to reduction in tensile properties but improvement in rheological property (storage modulus). The rheological behavior tends to become unique at higher frequencies (≥10 rad/s). Differential scanning calorimetry (DSC) results show that the total crystallinity has decreased with the increase in AlN loading in the composites. It is seen that there is an improvement in electrical conductivity, dielectric constant, and flammability properties with the addition of AlN in the nanocomposites. The experimental data of tensile modulus, electrical conductivity, and dielectric constant have been fitted with some available theoretical models to check the models’ applicability for the present composite systems. Results show that only Nicolais-Nicodemo model, McCullough model, and Rahaman-Khastgir model are applicable for predicting the tensile modulus, electrical conductivity, and dielectric constant of the composites, respectively.

Crystallization and melting behavior of i-PP: a perspective from Flory's thermodynamic equilibrium theory and DSC experiment

A novel conceptual framework that generates insightful new results about crystallization and melting behaviors of i-PP.

Effect of zinc bacitracin and phytase on growth performance, nutrient digestibility, carcass and meat traits of broilers

A total of 336 one-day-old Hubbard broiler chickens were randomly distributed among 8 groups, each containing six replicates (7 chickens/replicate). From 1 to 40 days of age, the groups fed the same starter, grower and finisher diets. The control group was unsupplemented; zinc bacitracin (ZnB) group received the antibiotic at 0.5 g/kg; fungal phytase (FP) groups received 250, 500 and 1000 U/kg diet of Aspergillus niger phytase (FP_250, FP_500 and FP_1000 groups), respectively; bacterial phyatse (BP) groups received 250, 500 and 1000 U/kg diet of Escherichia coli phytase (BP_250EP, BP_500EP and BP_1000EP groups) respectively. Considering the whole experimental period, body weight gain was unaffected by ZnB and different concentrations of bacterial and fungal phytase; however, the feed conversion ratio of the group fed a diet supplemented with 500 U of BP was better (p < 0.01) than those fed with a diet supplemented with 500 U of FP. BP_250 group had a higher (p < 0.05) apparent digestibility of ether extract compared to FP_250 group. In conclusion, bacterial phytase at 500 U may enhance performance of broiler chickens fed during days 1-40 of age and yield similar growth performance and economic efficiency to those of eB-supplemented groups.

Effect of titanium nanofiller on the productivity and crystallinity of ethylene and propylene copolymer

Bis(cyclopentadienyl) zirconium (IV) dichloride of empirical formula C10 H10 Cl2 Zr was used as a catalyst. Doped titania with iron (TiO2/Fe) nanofillers were used to study the effect of nanofillers on ethylene homopolymer and ethylene/propylene copolymer properties. Using titanium dioxide doped with iron (TiO2/Fe) resulted in the increase in the molecular weight (Mw) of polyethylene and ethylene/propylene copolymer nanocomposites of up to 80% when compared to the neat polymer. The catalyst activity was increased by using TiO2/Fe nanofiller for both ethylene polymerization and ethylene/propylene copolymerization. Besides the investigation of the catalyst activity and the molecular weight (Mw) of the obtained polymer, molecular weight distribution, copolymer composition, crystallinity and thermal characteristics of polyethylene and polyethylene/polypropylene nanocomposites were also studied. Non-isothermal crystallization kinetics of polyethylene and polyethylene/polypropylene nanocomposites fits well with the Avrami-Erofeev model.

Natural weather ageing of starch/polyvinyl alcohol blend: effect of glycerol content

Starch plasticized with glycerol and blended with polyvinyl alcohol (PVA) is recommended for use as a biodegradable material. The present article reports the results of studies of the natural weather ageing of starch/PVA blends having various amounts of glycerol in natural weather conditions of Saudi Arabia, with special reference to morphology and thermal behavior. Neat PVA has been used as a control to understand its behavior in its blend with starch. Differential scanning calorimeter studies indicated that an increase in the exposure time of samples to natural environment increases the crystallinity of PVA due to the breakage of intermolecular hydrogen bonding, thus facilitating the removal of the amorphous portion of the polymers in the blend. Thermogravimetric analysis revealed that an increase in glycerol content enhanced the degradation of the polymer, which is corroborated with the findings from the surface morphology using scanning electron microscopy and Fourier transfer infrared spectroscopy analyses.