Polymer synthesis and structure-property analysis, synthesis of various nanomaterials, surface modifications, polymer nanocomposites, polymer formulation and melt processing, polymer nanofibers and blends, super hydrophobic and super hydrophilic materials, especially polyurethanes, water dispersible polyurethanes, emulsion polymerizations for coating and painting, also for fire retardant, adhesives, textiles, antibacterial, biodegradable, biological and packaging applications.
Recent update on photocatalytic degradation of pollutants in waste water using TiO2-based heterostructured materials Nawal Madkhali, Cheera Prasad, K. Malkappa, Hyeong Yeol Choi, V. Govinda, Indra Bahadur, R.A. Abumousa Results in Engineering, 2023 To address the difficulties of global energy demand and pollution, developing photocatalytic materials for renewable energy production and environmental decontamination has long been an extremely attractive prospect. The production of a stable and well-organized nanostructured photocatalyst, like titanium dioxide (TiO2), is still a difficult task. Due to its unique physical and chemical properties, low toxicity, biological inertness, low energy consumption, low operating temperature, water insolubility, ease of availability, high chemical stability and environmentally benign nature, TiO2 photocatalysts were widely used as an exciting photocatalyst for pollution remediation. But, their photocatalytic applications are limited by their broad band gap energy, which can only be stimulated under UV light and rapid charge carrier recombination. Moreover, its band gap energy was reduced in a number of ways for visible light activity. In this review, we summarize recent research advances in TiO2 based heterostructure as a photocatalyst, preparation strategies. After that, a comprehensive and critical analysis of the many recent advancement made in order to improve the visible light photocatalytic characteristics of TiO2 for the degrading organic dyes, as well as a selection of results and significant photodegradation mechanisms is provided. In conclusion, this review concludes with a summary and perspectives on the current challenges faced and new directions in this emerging area of research.
Superior flame retardancy, antidripping, and thermomechanical properties of polyamide nanocomposites with graphene-based hybrid flame retardant Kuruma Malkappa, Jayita Bandyopadhyay, Vincent Ojijo, Suprakas Sinha Ray Journal of Applied Polymer Science, 2022 Abstract Graphene is considered one of the most prominent halogen‐free multifunctional flame retardants for polymers, and the resultant nanocomposites also display a good balance of properties. However, the biggest concern nowadays is thermal oxidative degradation, which mainly affects the flame retardant (FR) efficiency of graphene. To improve the flame retardancy and thermal oxidative degradation efficiency, graphene was functionalized with a combination of polycyclotriphosphazes and siloxanes via a sol–gel surface modification method, yielding a graphene‐based hybrid FR (PSGO) containing multiple elements (P, N, S, and Si). The PSGO‐containing PA6 composite exhibited significant improvements in the water resistance, thermal, mechanical, and FR properties, as compared with those of 3‐isocyanatopropyltriethoxysilane functionalized graphene oxide (ITS‐GO) and siloxane‐modified polycyclotriphosphazenes (m‐PZS) individually. The peak heat release rate and total heat release values of the PA6 composites with 10 wt% PSGO decreased by 45.7% and 36.9%, respectively, compared to those of pristine PA6. Moreover, it was confirmed that 10 wt% PSGO in the PA6 composite resulting in a V–0 rating in the UL‐94 tests, even after the water immersion test. These attractive properties are attributed to the resistance to thermal‐oxidative degradation of PSGO and the improved interfacial interactions with the polymer matrix. Therefore, this PSGO can be used as a multifunctional modifier to improve the water resistance, thermal, mechanical, and FR properties of polymers.
Effect of nanofillers characteristics and their selective localization on morphology development and rheological properties of melt-processed polylactide/poly(butylene adipate-co-terephthalate) blend composites Reza Salehiyan, Mohammadreza Nofar, Kuruma Malkappa, Suprakas Sinha Ray Polymer Engineering and Science, 2020 Abstract This article reports the effects of the characteristics and selective localization of nanofillers on the morphology development and rheological properties of melt‐processed polylactide/poly(butylene adipate‐co‐terephthalate) (PLA/PBAT) blend composites. Four types of nanofillers (1 wt%) are used: nanoclay (Cloisite30B [C30B]), carbon nanotubes (CNTs), nanosilica, and graphene oxide (GO). Transmission electron microscopy studies reveal that C30B is localized mainly at the PLA/PBAT interface, whereas silica, GO, and CNT are localized in PBAT droplets, although some CNTs also appear toward the interface inside the PBAT. Despite their selective localization inside the PBAT, CNTs are found to be the most effective particles for droplet size reduction, whereas silica nanoparticles are ineffective. The CNT bundles recoil during melt blending, and eventually, their breakage facilitates droplet breakup. The effects of nanofiller localization and annealing under dynamic shear on the blend morphologies are also explored through rheological analysis. The results show an anomalous relationship with the morphologies of the composites. It is also found that both coalescence and thermal degradation are involved in the annealing process of the blends. Interestingly, the CNT‐filled composites may have been transformed into co‐continuous‐like structures during annealing, unlike the other blends studied here.
Design of Poly(cyclotriphosphazene)-Functionalized Zirconium Phosphate Nanoplatelets To Simultaneously Enhance the Dynamic Mechanical and Flame Retardancy Properties of Polyamide 6 Kuruma Malkappa, Jayita Bandyopadhyay, Suprakas Sinha Ray ACS Omega, 2020 To obtain polyamide 6 (PA6) composites with improved flame retardancy and thermomechanical properties, highly cross-linked supramolecular poly(cyclotriphosphazene)-functionalized α-zirconium phosphate (f-ZrP) nanoplatelets were synthesized and melt-blended with PA6 in a twin-screw extruder. The performance enhancements of composites were investigated through measuring the dynamic mechanical property and observing cone calorimeter data, toxic gas evolution, and UL-94 rating. The thermomechanical performance of PA6 was increased by 37.2% after composite formation with f-ZrP. As for the fire retardancy performance, compared to neat PA6, the composite containing 10 wt % f-ZrP showed 41.7 and 30.4% decrease in the peak heat and total heat release rates, respectively, and the UL-94 rating of the composite was V-0. Moreover, the thermogravimetric analysis combined with infrared spectroscopy revealed that the addition of f-ZrP to the PA6 led to decrease in the evolution of the volatile compounds and toxic gases, with the formation of highly cross-linked P–N-containing dense char with microspheres, providing a strong barrier to the inhibition of the heat and flammable volatile components transferring between the flame zone area and substrate during the combustion test. Finally, based on the obtained results, the possible mechanisms for improved mechanical and fire retardancy properties of the composites were proposed.
Thermal Stability, Pyrolysis Behavior, and Fire-Retardant Performance of Melamine Cyanurate@Poly(cyclotriphosphazene- co-4,4′-sulfonyl diphenol) Hybrid Nanosheet-Containing Polyamide 6 Composites Kuruma Malkappa, Suprakas Sinha Ray ACS Omega, 2019 A novel halogen-free highly cross-linked supramolecular poly(cyclotriphosphazene-co-4,4′-sulfonyl diphenol) (PZS)-functionalized melamine cyanurate (MCA) (MCA@PZS) hybrid nanosheet fire-retardant (FR) was synthesized and thoroughly characterized using scanning electron microscopy, Fourier-transform infrared (FTIR), X-ray diffraction, and X-ray photoelectron spectroscopy analyses. The polyamide 6 (PA6) composites comprising MCA, PZS, and the MCA@PZS hybrids were prepared via the melt-blending technique. The thermogravimetric analysis combined with FTIR and mass spectroscopy revealed that during thermal degradation, the PA6/MCA@PZS composites released less toxic gases and small organic volatile compounds than the neat PA6 and composites containing MCA or PZS solely. Moreover, compared to neat PA6, the PA6 composite with a 5 wt % MCA@PZS hybrid exhibited enhanced fire retardation properties, with a 29.4 and 32.1% decrease in the peak heat and total heat release rates, respectively. Besides, the PA6 composites with MCA@PZS-5% content achieved a V-0 rating in the UL-94 test. Finally, based on the obtained results from gaseous and condensed phases, the possible mechanism responsible for improved FR properties of the PA6/MCA@PZS composites was proposed.
Ferrocene grafted hydroxyl terminated polybutadiene: A binder for propellant with improved burn rate Billa Narasimha Rao, Kuruma Malkappa, Nagendra Kumar, Tushar Jana Polymer, 2019 In this work, iron containing hydroxyl terminated polybutadiene (Fe-HTPB) based binder cum burn rate catalyst has been developed without altering the crucial physical properties of HTPB. Ferrocene, the source of Fe in the Fe-HTPB, has been grafted at the terminal carbons of HTPB to ensure no alternation in microstructure of HTPB which in turn helped in retaining physical properties of pristine HTPB. The structure and the presence of ferrocene as the end cap groups of the Fe-HTPB were confirmed by solid-state NMR and MALDI-TOF-MS analysis. Control over the viscosity and Fe content of the Fe-HTPB was achieved by varying the grafting reaction recipes and conditions. The Fe content, as measured by inductively coupled plasma - atomic emission spectroscopy (ICP-AES) in the Fe-HTPB varied from 0.06% to 0.165% (by weight) and found to be responsible for increasing viscosity of Fe-HTPB from 5857 mPa S to 11,890 mPa S. Non aluminized composite solid propellants (CSPs) with 86% (wt%) ammonium perchlorate loading were prepared using Fe-HTPB as a binder for studying the burn rate efficiency. Burn rates of CSPs made from Fe-HTPB binders were found to be enhanced by ∼125% compared to CSPs of pristine HTPB. At 40 bar pressure, the burn rate of CSPs made from Fe-HTPB and pristine HTPB binders are 20.56 and 9.07 mm/s burn rate, respectively. In addition, all the CSPs made from Fe-HTPB were found to be very stable as their pressure index is less than 0.5.
