D.N. Goswami and Shravan Kumar
Insulating varnishes are widely used for coating of armatures/coils of electric motors, transformers and also for finishing electrical components. Natural resin shellac finds…
Abstract
Insulating varnishes are widely used for coating of armatures/coils of electric motors, transformers and also for finishing electrical components. Natural resin shellac finds considerable use in the manufacture of insulating varnishes. Improved dielectric properties have been obtained for varnishes prepared from shellac modified with synthetic resins, drying oils etc. The present article provides information about the researchers so far carried out on both the air‐drying and baking type of insulating varnishes based on shellac.
Dipanjan Goswami, Sakun Boon-Itt, Neera Jain and D.R. Agarwal
The quality and reliability of medical communication for branded drug adoption is extremely critical, not only for safeguarding patient interests but also for ensuring successful…
Abstract
Purpose
The quality and reliability of medical communication for branded drug adoption is extremely critical, not only for safeguarding patient interests but also for ensuring successful investments by multinational pharmaceutical firms. This paper predicts doctors’ prescribing intentions based on communication relationship among factors for late entrant branded drugs, compared with pioneering brand choice, for treating chronic diseases such as hypertension.
Design/methodology/approach
The constructs were validated with structural equation model for a sample set of 151 doctors from private hospitals in the National Capital Region of India.
Findings
This research reveals communication drivers and draws on theory to suggest that the doctor’s behavioural prescription intentions, subject to social influence from their colleagues, leads to lower adoption responses.
Research limitations/implications
Given that limitations on sample size are often unavoidable, this study reveals that, due to the availability of substituting brands, alternate therapeutic routes and lack of availability of a practical guide for prescription, a communication model needs to be developed and validated.
Practical implications
Furthermore, managers of pharmaceutical firms should differentiate between the effects of direct and indirect communication–integration efforts for minimizing uncertainty in drug adoption in the context of the fragmented and unpredictable Indian market.
Originality/value
A late entrant may lose its dominant market share to alternate brands from other suppliers due to communication gaps in an unstructured market, leading to low adoption intentions. The study provides business theorists, drug marketers and health-care professionals with unique insights into specific communication drivers of prescribing decisions, aimed at ensuring reliable and appropriate drug adoption in Indian markets.
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D.N. Goswami, P.C. Jha and K. Mahato
The melt‐viscosity of shellac at various temperatures, the solution viscosity of shellac and the solution viscosity of several shellac‐based varnishes were investigated using a…
Abstract
The melt‐viscosity of shellac at various temperatures, the solution viscosity of shellac and the solution viscosity of several shellac‐based varnishes were investigated using a cone and plate rheometer. The study revealed information regarding yield stress (minimum force required for initiating flow) and thixotropic properties of shellac and shellac‐based materials. Such information will be useful for developing shellac‐based moulded articles and shellac‐based varnish compositions.
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D.N. Goswami and Shravan Kumar
The curing of shellac with epoxy resin by fusion was studied in detail by Tripathi et al. An improvement in the film properties was noticed for the varnishes prepared from the…
Abstract
The curing of shellac with epoxy resin by fusion was studied in detail by Tripathi et al. An improvement in the film properties was noticed for the varnishes prepared from the cured products of 70 parts of shellac with 30 parts of epoxy resin. Similar study was made on the modification of shellac with phenolic resin by Kumar and Sankaranarayanan and Kumar. The films obtained from the modified varnishes showed improved heat and water resistance.
Rawya Ben Jaballah, Mohamed Bechir Ben Hamida, Jehad Saleh and Mohammed A. Almeshaal
The purpose of this paper is to investigate the enhancement of the performance of bubble absorber using hybrid nanofluid as a cooled NH3/H2O absorption system to reduce their size…
Abstract
Purpose
The purpose of this paper is to investigate the enhancement of the performance of bubble absorber using hybrid nanofluid as a cooled NH3/H2O absorption system to reduce their size and to find the best fitting model. A numerical model for ammonia-water bubble absorber was developed to show the influence of operating conditions and design parameters on the absorber performance.
Design/methodology/approach
A finite difference numerical method is used to solve the numerical model. The model is subjected to the inlet conditions of liquid, vapor and coolant flow regimes. The absorber modeling was divided into small elements along the absorber length.
Findings
The model proposed is validated with previously published works. Then agreement between the both is considered as good.
Research limitations/implications
Numerical results/The use of hybrid nanofluids.
Originality/value
The results showed that the hybrid nanofluid is the best cooling medium. Very high heat transfer rates are obtained because of the high thermal conductivity and specific heat of hybrid nanofluid, and consequently, the absorber size decreases. It was also found that the absorber thermal load and the mass absorption flux increase with increasing of solid volume fraction. Also, the existence of an optimal absorber length was revealed, required for complete absorption when using hybrid nanofluid as a cooling medium. It is recommended that using hybrid nanofluid to remove the heat from the absorber is the best candidate for NH3/H2O absorption performance enhancement.
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To explore compatibility of natural resin shellac with acrylic resin in order to make a more eco‐friendly coating composition and also to open a new avenue for consumption of…
Abstract
Purpose
To explore compatibility of natural resin shellac with acrylic resin in order to make a more eco‐friendly coating composition and also to open a new avenue for consumption of shellac.
Design/methodology/approach
Different compositions of paint were prepared by varying the contents of shellac and acrylic resin. Selection was made for the composition yielding the best combination of properties like water resistance, alkali resistance, washability, etc.
Findings
Modification of shellac with acrylic resin showed improved film performance. The modified product showed good adhesion, finish; the films were smooth, flexible and no flaking/detachment was observed from the surfaces. This resulted in from esterification linkages between shellac and acrylic resin.
Research limitations/implications
The concentration of shellac in the composition was limited to a certain extent. Increase in shellac content impairs the film performance of the composition, especially with regard to alkali resistance.
Practical implications
Shellac was found to be very compatible with acrylic resin at all concentrations, this may be adopted in developing other shellac‐acrylic based products.
Originality/value
The modification of shellac with acrylic resin has been done, for the first time, to open a new vista for the consumption of shellac in surface coating.
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Mohammad Fahim Ansari, Gautam Sarkhel, Dipendra Nath Goswami and Bangali Baboo
The purpose of this paper is to improve the properties of shellac by blending with novolac and to study the thermal behaviour of the blends with an ultimate aim to use as surface…
Abstract
Purpose
The purpose of this paper is to improve the properties of shellac by blending with novolac and to study the thermal behaviour of the blends with an ultimate aim to use as surface coating material.
Design/methodology/approach
Novolac was synthesized by reaction of phenol with formaldehyde in a molar ratio of 1:0.8, in acidic condition. Blending of shellac with novolac was done in solution and films of the blends, prepared on glass slides and tin panels, were baked at 150°C for 15 minutes. Properties of the films were studied as per standard procedures.
Findings
Films of shellac‐novolac blends showed improvement in gloss and impact resistance compared to those of shellac alone. Gloss of blends increased with the increase in concentration of novolac and further increased on baking the films. Scratch hardness of shellac decreased on blending with novolac. Baked films of the blends showed resistance to heat and water. Films of shellac‐novolac blends were found to be more resistant to polar solvents compared to non‐polar solvents.
Research limitations/implications
Shellac, prepared from kusmi seedlac, was used in the study. Besides shellac, dewaxed decolorized lac (DDL), dewaxed lac (DL) and bleached lac (BL) could also be used for study on blending with novolac.
Practical implications
Blending of shellac with novolac improved the film properties of shellac. The study suggests that the compositions can be utilised in developing formulations of coating material with improved properties for metal surfaces.
Originality/value
The formulations based on modification of shellac with novolac and study of the film properties utilising various instruments are novel. The formulations based on shellac and novolac can find applications in the field of surface coating with desired purposes.
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Mohammad Fahim Ansari and Gautam Sarkhel
The purpose of this study is to improve the coating properties of shellac–epoxidised novolac blends by treatment with melamine formaldehyde resin (MF) at ambient temperature for…
Abstract
Purpose
The purpose of this study is to improve the coating properties of shellac–epoxidised novolac blends by treatment with melamine formaldehyde resin (MF) at ambient temperature for its use as a coating material.
Design/methodology/approach
Epoxidised-novolac resin was synthesised by epoxidation of novolac resin with epichlorohydrin. Novolac resin was synthesised by reaction of phenol with formaldehyde in acidic medium. Shellac was blended with the epoxidised-novolac resin in solution in varying ratios and treated the blends with MF resin in fixed ratio. Coating properties of the treated compositions were studied using a standard procedure. The compositions were characterised with Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and scanning electron microscopic (SEM) spectroscopy.
Findings
Treatment of shellac–epoxidised-novolac blends with MF resin improved water and alkali resistance of the blends, besides enhancing gloss. Gloss in all the blends was uniformly increased on treatment with MF resin. Water resistance of the blends tremendously improved after treatment with MF resin. Contact angle of the blends against water increased while decreased against ethylene glycol and dioxane. The compositions were more resistant to polar solvent than non-polar ones, suggesting that the compositions shifted to hydrophobic (lipophilic) nature on treatment with the MF resin.
Research limitations/implications
A specified concentration of MF resin was used in the study. Different concentrations of the MF resin can also be tried for treatment of shellac–epoxidised-novolac blends to see the effect of the resin on the blends.
Practical implications
Treatment of shellac–epoxidised-novolac blend with MF resin improved the coating properties of the blends. The formulation SeNB-64 is the best with high gloss, good impact, scratch hardness and water resistance, and hence can be used as coating material for metal surfaces.
Originality/value
Blending of shellac with epoxidised-novolac resin and treatment of the blends with the MF resin was done for the first time. The formulation SeNB-64 can be used as coating material for metal surfaces.
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Mohammad Fahim Ansari, Gautam Sarkhel, Dipendra Nath Goswami and Bangali Baboo
– The purpose of this paper is to improve the properties of shellac by blending with epoxidised novolac resin for its use as coating material for metal surfaces.
Abstract
Purpose
The purpose of this paper is to improve the properties of shellac by blending with epoxidised novolac resin for its use as coating material for metal surfaces.
Design/methodology/approach
Epoxidised-novolac resin was synthesised by epoxidation of novolac resin, which in turn was synthesised by reaction of phenol with formaldehyde. The epoxidised-novolac resin was blended with different weight ratios of shellac ranging 10-50 weight per cent with an interval of 10 weight per cent. Films of the blends were studied for different coating properties using standard procedure.
Findings
Significant improvement in coating properties of shellac such as gloss, scratch hardness and impact resistance was observed on blending with epoxidised novolac resin. Resistance towards water and alkali increased, while acid resistance decreased, with the increase in concentration of epoxidised novolac resin in the blends. Contact angle measurement revealed that blends showed more resistance towards polar solvent than non-polar ones.
Research limitations/implications
Epoxidised-novolac resin used in the study was synthesised of epoxy equivalent of 187. Epoxidised-novolac resin of different epoxy equivalent can also be synthesised and used for blending and studying the properties.
Practical implications
Blending of shellac with epoxidised-novolac resin improved the coating properties of shellac, which was further enhanced with the treatment of butylated melamine formaldehyde resin. The formulation can be used as coating material for metal surfaces.
Originality/value
Blending of shellac with epoxidised-novolac resin was done for the first time. The formulation can be utilised for developing coating material for metal surfaces.
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D. Bhatia, P.C. Sarkar and M. Alam
To investigate changes at molecular level in lac‐resole blends, occurring due to the effect of thermal stress at higher temperatures and different intervals of baking time.
Abstract
Purpose
To investigate changes at molecular level in lac‐resole blends, occurring due to the effect of thermal stress at higher temperatures and different intervals of baking time.
Design/methodology/approach
Films of lac‐resole blends were applied on tin‐panels and baked at 200°C for different time intervals. The baked films were examined by specular reflectance spectroscopy, as they were otherwise difficult to examine through conventional IR techniques, using KBr pellet method. The results obtained were compared and reported.
Findings
When lac‐resole blends are baked at 200°C, in addition to possible chromic ring structures, esters linkages are formed between lac and resole molecules through cross linkages among different reactive sites of lac and PF resin. Blend of 70 per cent lac: 30 per cent resole, baked at 200°C for 20 min was found to be the best in terms of different physico‐chemical properties.
Research limitations/implications
Lac‐synthetic resin blends are structurally complex in nature. Chemical researches on such blends have been typically limited due to lack of modern tools. The present method, to determine molecular level changes in lac‐resole blends due to heating effects, using state‐of‐the‐art instrumentation and computational techniques, opens a new field for research and industry.
Practical implications
Lac and its blends retain their significance in the surface coatings and food applications, in the formulation of lacquers, varnishes and in the finishing industry. This study could have significant implication for such industries from application point of view.
Originality/value
As of now, there is no report of specular reflectance data on lac‐synthetic resin blends. This paper represents the first attempt to obtain and correlate reflectance data on such blends. It also highlights the convenience of the method and the scope of sophisticated data analysis, including derivative spectrometry.