Reactively compatibilised polyamide6/ethylene-co-vinyl acetate blends: mechanical properties and morphology

Mechanical properties and morphological studies of compatibilised blends of PA6/EVA-g-MA and PA6/EVA/EVA-g-MA were studied as functions of maleic anhydride content (MA) and dispersed phase (EVA-g-MA) concentrations, respectively at blending composition of 20 wt% dispersed phase (EVA-g-MA or combination of EVA and EVA-g-MA). The maleic anhydride (MA) was varied from 1 to 6 wt% in the PA6/EVA-g-MA blend, whereas MA concentration was fixed at 2 wt% in the ternary compositions with varying level of EVA-g-MA. ATR-IR spectroscopy revealed the formation of in situ copolymer during reactive compatibilisation of PA6 and EVA-g-MA. It was found that notched Izod impact strength of PA6/EVA-g-MA blends increased significantly with MA content in EVA-g-MA. The brittle to tough transition temperature of reactively compatibilised blends was found to be at 23 °C. The impact fractured surface topology reveals extensive deformation in presence of EVA-g-MA whereas; uncompatibilised PA6/EVA blend shows dislodging of EVA domains from the matrix. Tensile strength of the PA6/EVA-g-MA blends increased significantly as compared to PA6/EVA blends. Analysis of the tensile data using predictive theories showed an enhanced interaction of the dispersed phase and the matrix. It is observed from the phase morphological analysis that the average domain size of the PA6/EVA-g-MA blends is found to decrease gradually with increase in MA content of EVA-g-MA. A similar decrease is also found to observe in PA6/EVA/EVA-g-MA blends with increase in EVA-g-MA content, which suggest the coalescence process is slower in presence of EVA-g-MA. An attempt has been made to correlate between impact strength and morphological parameters with regard to the compatibilised system over the uncompatibilised system.     

Host-Assisted Delivery of a Model Drug to Genomic DNA: Key Information from Ultrafast Spectroscopy and in silico Study

Drug delivery to a target without adverse effects is one of the major criteria for clinical use. Herein, we have made an attempt to explore the delivery efficacy of SDS surfactant in a monomer and micellar stage during the delivery of the model drug, Toluidine Blue (TB) from the micellar cavity to DNA. Molecular recognition of pre-micellar SDS encapsulated TB with DNA occurs at a rate constant of k₁ ∼652 s⁻¹. However, no significant release of encapsulated TB at micellar concentration was observed within the experimental time frame. This originated from the higher binding affinity of TB towards the nano-cavity of SDS at micellar concentration which does not allow the delivery of TB from the nano-cavity of SDS micelles to DNA. Thus, molecular recognition controls the extent of DNA recognition by TB which in turn modulates the rate of delivery of TB from SDS in a concentration-dependent manner.     

Melt‐mixed polypropylene/acrylonitrile‐butadiene‐styrene blends with multiwall carbon nanotubes: Effect of compatibilizer and modifier on morphology and electrical conductivity

Cocontinuous blends of 45/55 polypropylene (PP)/acrylonitrile‐butadiene‐styrene (ABS) with multiwall carbon nanotubes (MWNT) were prepared by melt‐mixing in a conical twin‐screw microcompounder. PP‐grafted‐maleic anhydride (PP‐g‐MA) and styrene MA were used as compatibilizers for PP/ABS blends. Scanning electron microscopic observations showed phase segregation of PP‐g‐MA in the blends. State of dispersion of MWNT in the presence or absence of the compatibilizers was assessed through AC electrical conductivity measurements and crystallization studies of the blends. An improvement in AC electrical conductivity was observed in blends in presence of either styrene MA or dual compatibilizers. The lowest electrical percolation threshold was achieved at 0.1 wt % of MWNT using sodium salt of 6‐amino hexanoic acid‐modified MWNT. Significant increase in crystallization temperature of PP phase of blends with MWNT was observed in the presence of compatibilizers as compared to blends without compatibilizers. An attempt has been made to address the complex issues of phase segregation, compatibilization, and dispersion of MWNT in cocontinuous blends of PP/ABS. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Impacts of conservation agriculture on soil aggregation and aggregate-associated N under an irrigated agroecosystem of the Indo-Gangetic Plains

We evaluated impacts of conservation agriculture (zero tillage, bed planting and residue retention) on changes in total soil N (TSN) and aggregate-associated N storage in a sandy loam soil of the Indo-Gangetic Plains. Cotton (Gossypium hirsutum) and wheat (Triticum aestivum) crops were grown during the first 3 years (2008–2011) and in the last year, maize (Zea mays) and wheat were cultivated. Results indicate that after 4 years the plots under zero tillage with bed planting (ZT-B) and zero tillage with flat planting (ZT-F) had 15 % higher TSN concentrations than conventional tillage and bed planting plots (CT-B) (0.63 g kg^?1 soil) in the 0–5 cm soil layer. CT-B plots had lower soil bulk density that ZT plots in that layer. Plots under ZT-B (0.57 Mg ha^?1) contained 20 % higher TSN stock in the 0–5 cm soil layer than CT-B plots (0.48 Mg ha^?1). However, tillage had no impact on TSN concentration or stock in the sub-surface (5–15 and 15–30 cm) soil layers. Thus, in the 0–30 cm soil layer, ZT-B plots contained 6 and 5 % higher (P > 0.05) TSN stock compared with CT-B (2.15 Mg N ha^?1) and CT-F (2.19 Mg N ha^?1) plots respectively after 4 years. Plots that received cotton/maize + wheat residue (C/M + W RES) contained 16 % higher TSN concentration than plots with residues removed (N RES; 0.62 g kg^?1 soil) in the surface (0–5 cm) layer. Plots with only cotton/maize residue (C/M RES) or only wheat residue (W RES) retention/incorporation had similar TSN concentrations and stocks in the subsurface layer. Plots under ZT-B also had more macroaggregates (0.25–8 mm) and greater mean weight diameter with lower silt + clay sized particles than CT-B plots in that layer. A greater proportion of large macroaggregates (2–8 mm) in the plots under C/M + W RES compared with N RES were observed. In the 5–15 cm soil layer ZT-B and C/M + W RES treated plots had more macroaggregates and greater mean weight diameter than CT-B and N RES treated plots, respectively. Because of the greater amount of large aggregates, plots under ZT-B and C/M + W RES had 49 and 35 % higher large macroaggregate-associated N stocks than CT-B (38 kg TSN ha^?1) and N RES (40 kg TSN ha^?1) plots, respectively, in the 0–5 cm soil layer, although aggregates had similar TSN concentrations in all plots. Both tillage and residue retention had greater effects on aggregate-associated N stocks in the 5–15 cm layers. In addition to N content within large macroaggregates, small macroaggregate-associated N contents were also positively affected by ZT-B and C/M + W RES. Tillage and residue retention interaction effects were not significant for all parameters. Thus, the adoption of ZT in permanent beds with crop residue addition is a better management option for improvement of soil N (and thus possibly a reduced dose of fertilizer N can be adopted in the long run), as the management practice has the potential to improve soil aggregation with greater accumulation of TSN within macroaggregates, and this trend would likely have additive effects with advancing years of the same management practices in this region.     

Mechanical,electrical and thermal performance of hybrid polyethylene-graphene nanoplatelets-polypyrrole composites: a comparative analysis of 3D printed and compression molded samples

ABSTRACT

The paper focuses on the investigation of the 3D printing of multi-functional composites using graphene nanoplatelets (GNP), polypyrrole (PPY) and linear low-density polyethylene (LLDPE). A holistic approach was performed and characterization methods to assess the properties of 3D printed composites and compared with those of compression molded composites and neat LLDPE to understand the factors affecting their performance. It has been noted that the 3D printed composites have superior mechanical and electrical properties than neat LLDPE, but slightly lower compared to those of compression molded composites having high packing density of fillers. The nominal increases were 13.2% (tensile strength), 31.9% (flexural strength), 29.4% (flexural modulus) and 24.7% (storage modulus).     

Impact of adhesive ingredients on adhesion between rubber and brass-plated steel wire in tire

Proficiency on underlying mechanism of rubber-metal adhesion has been increased significantly in the last few decades. Researchers have investigated the effect of various ingredients, such as hexamethoxymethyl melamine, resorcinol, cobalt stearate, and silica, on rubber-metal interface. The role of each ingredient on rubber-metal interfacial adhesion is still a subject of scrutiny. In this article, a typical belt skim compound of truck radial tire is selected and the effect of each adhesive ingredient on adhesion strength is explored. Out of these ingredients, the effect of cobalt stearate is found noteworthy. It has improved adhesion strength by 12% (without aging) and by 11% (humid-aged), respectively, over control compound. For detailed understanding of the effect of cobalt stearate on adhesion, scanning electron microscopy and energy dispersive spectroscopy are utilized to ascertain the rubber coverage and distribution of elements. X-ray photoelectron spectroscopy results helped us to understand the impact of Cu_XS layer depth on rubber-metal adhesion. The depth profile of the Cu_XS layer was found to be one of the dominant factors of rubber-metal adhesion retention. Thus, this study has made an attempt to find the impact of different adhesive ingredients on the formation of Cu_XS layer depth at rubber-metal interface and establish a correlation with adhesion strength simultaneously.     

Electrical conductivity of poly(vinyl alcohol)/carbon nanotube multilayer thin films: Influence of sodium polystyrene sulfonate mediated carbon nanotube dispersion

This investigation was aimed to enhance the dispersibility of multi-walled carbon nanotubes (MWCNT) using sodium polystyrene sulfonate (Na-PSS) polyelectrolyte. Subsequently, electrically conducting, multi-layer thin films are prepared utilizing layer by layer assembly method with poly(vinyl alcohol) as a host matrix. The highest extent of MWCNT dispersion was observed in MWCNT:Na-PSS ratio of 1:9 (wt/wt), which was estimated from UV-Vis spectroscopic analysis. Zeta potential measurements of Na-PSS modified MWCNT dispersion showed large negative potentials ranging from −52 to −64 mV in the most stable pH range of 4 to 10, suggesting the colloidal stability is due to the long-range repulsive nature of electrostatic interactions from negatively charged sulfonate groups. Complementary molecular dynamics simulations showed that adsorption of Na-PSS imparts a large negative potential to the carbon nanotube surface, which increases with an increase in Na-PSS concentration. The multi-layer thin film of (1:9) MWCNT:Na-PSS exhibited a DC electrical conductivity of 2.96 × 10² S/m.     

The simultaneous addition of styrene maleic anhydride copolymer and multiwall carbon nanotubes during melt‐mixing on the morphology of binary blends of polyamide6 and acrylonitrile butadiene styrene copolymer

The effect of simultaneous addition of multiwall carbon nanotubes (MWNTs) and a reactive compatibilizer (styrene maleic anhydride copolymer, SMA) during melt‐mixing on the phase morphology of 80/20 (wt/wt) PA6/ABS blend has been investigated. Morphological analysis through scanning and transmission electron microscopic analysis revealed finer morphology of the blends in presence of SMA + MWNTs. Fourier transform infrared spectroscopic analysis indicated the formation of imide bonds during melt‐mixing. Non‐isothermal crystallization studies exhibited the presence of a majority faction of MWNTs in the PA6 phase of 80/20 (wt/wt) PA6/ABS blend in presence of SMA + MWNTs. Rheological analysis, dynamic mechanical thermal analysis, and thermogravimetric analysis have demonstrated the compatibilization action of simultaneous addition of a reactive compatibilizer (SMA copolymer) and MWNTs in PA6/ABS blends. An attempt has been made to investigate the role of simultaneous addition of SMA copolymer and MWNTs on the morphology of 80/20 (wt/wt) PA6/ABS blend through various characterization techniques. POLYM. ENG. SCI., 55:457–465, 2015. © 2014 Society of Plastics Engineers     

Iron-Based Nanoparticles for Toxic Organic Degradation: Silica Platform and Green Synthesis

Iron and iron oxide nanoparticles (NPs) are finding wide applications for the remediation of various toxic chloro-organic compounds (such as trichloroethylene, TCE), via reductive and oxidative processes. In this study, Fe NPs (30-50 nm) are synthesized by reduction from ferric ions immobilized (by ion exchange) on a platform (two types of sulfonated silica particles), in order to prevent the NP agglomeration. Next, the Fe NPs are oxidized and their effectiveness for the oxidative dechlorination of TCE via the heterogeneous decomposition of hydrogen peroxide to OH? on the surface of the iron oxide NPs was demonstrated. For the reductive approach, the use of ascorbic acid as a "green" reducing agent in conjunction with a secondary metal (Pd) inhibits NP oxidation and agglomeration through surface adsorbed species. The Fe/Pd NPs have been successfully applied for the dechlorination of TCE (k(SA), surface-area normalized reaction rate, = 8.1 ×10(-4) L/m(2)h).     

Isothermal crystallization kinetics of polypropylene in melt‐mixed composites of polypropylene and multi‐walled carbon nanotubes

The isothermal crystallization behaviour of the polypropylene (PP) phase in PP/multi‐walled carbon nanotubes (MWCNTs) composites has been investigated via differential scanning calorimetric analysis, which showed the influence of the varying dispersion level of MWCNTs in the respective PP matrix. PP/MWCNTs composites were prepared via melt‐blending technique, wherein two different grades of MWCNTs of varying average “agglomerate” size and varying entanglements (N‐MWCNTs and D‐MWCNTs) were utilized. Furthermore, the influence of melt‐viscosity of the PP phase was investigated on the crystallization kinetics of the PP/MWCNTs composites. Heterogeneous nucleation ability of MWCNTs has resulted in a decrease in half time of crystallization (t _1/2) from ～14 min for pure PP to ～6 min for PP/N‐MWCNTs and ～11 min for PP/D‐MWCNTs composites at 1 wt% of MWCNTs at 132 °C. Overall rate of crystallization (k) has significantly increased to 4.9 × 10^?2 min^?1 for PP/N‐MWCNTs composite as compared with 6.2 × 10^?3 min^?1 for PP/D‐MWCNTs composite at 0.5 wt% of MWCNTs at 132 °C. Moreover, the effect of a novel organic modifier, Li‐salt of 6‐amino hexanoic acid along with a compatibilizer (PP‐g‐MA) has also been investigated on the crystallization kinetics of the PP phase in PP/MWCNTs composites. POLYM. ENG. SCI., 57:1136–1146, 2017. © 2017 Society of Plastics Engineers