Deepak Srivastava

Process modeling, optimization and analysis of esterification reaction of cashew nut shell liquid (CNSL)-derived epoxy resin using response surface methodology.

Concept of five-levels-four-factors central composite rotatable design was utilized for the optimization of reaction conditions of cardanol-based vinyl ester resin production, by employing response surfaces methodology, to establish a relationship between the process variables and the extent of conversion under a wide range of operating conditions which resulted in different extent of conversions. The maximum extent of conversion of cardanol-based epoxidised novolac resin (CNE) and methacrylic acid (MA) catalyzed by triphenylphosphine was found to be 95% at optimum set of conditions of molar ratio (1:0.9) between CNE and MA, catalyst concentration (1.49%), reaction temperature (89.96 °C) and reaction time (17,991s). Geometrical representation of the mathematical models in three-dimensional response surface plots and isoresponse contour plots served as a good aid in understanding the behavior of reaction under different operating conditions by only limited sets of experiments. A statistical model predicted that the highest conversion yield of novolac resin would be greater than 95% at the optimized reaction conditions. The predicted values thus obtained were close to the experimental values indicating suitability of the model.

Degradation Kinetics of Resole-Modified Epoxy. I

Abstract Blends of resole with epoxy resin (General Purpose) having different weight ratios (0/100, 25/75, 50/50, 75/25, and 100/0) based on physical mixing have been prepared. These blends were cured by adding polyamide in a 60:40 ratio based on blend resins and polyamide. The degradation kinetics of these resins was studied by dynamic thermogravimetric analysis in nitrogen atmosphere at a heating rate of 15°C/min by using the Coats-Redfern equation. It is concluded that the degradation of each sample follows first-order (n = 1) degradation kinetics. This is obtained on the basis of best fit analysis, and all the parameters are confirmed by regression analysis. From the reaction order value, activation energy (E) and preexponential factor (Z) were calculated by the slope and intercept of the plot between X and Y, respectively.

Studies on the effect of concentration of formaldehyde on the synthesis of resole-type epoxidized phenolic resin from renewable resource material

Epoxidized cardanol/formaldehyde resins (ERCF) were synthesized by reacting resole type cardanol/formaldehyde resin and epichlorohydrin in basic medium at 120 °C. Resole-type phenolic resins were synthesized by reacting cardanol and formaldehyde (molar ratios 1:1.3, 1:1.5, 1:1.7, 1:1.9,and 1:2.1) in the presence of sodium hydroxide, as catalyst, at five different temperatures ranging between 60 and 80 °C with an interval of 5°C for a maximum period of 6 h. A set of samples were characterized by Fourier transform infrared and nuclear magnetic resonance spectroscopic analysis. The molecular size distribution of resole phenolics was studied by high-resolution gel permeation chromatography. Differential scanning calorimetry technique was used to investigate the curing behavior of the synthesized epoxy resins. Single-step mass loss in dynamic thermo gravimetric traces for the ERCF was observed.

Studies on the Thermal, Mechanical and Chemical Resistance Properties of Natural Resource Derived Polymers

Cardanol-based epoxidized resole resins (ERCF) were synthesized by reacting resole type phenolic resin (RCF) and epichlorohydrin in basic medium, at 120 °C. Resole type phenolic resins were synthesized by reacting cardanol (C) and formaldehyde (F) in the presence of sodium hydroxide, as catalyst, at five different temperatures ranging between 60-80 °C with an interval of 5 °C for a maximum period of 6h. These prepared samples were cured using 15% polyamide as curing agent at 120 ± 2 °C for 1h. Mechanical and chemical resistance characteristics of prepared samples were evaluated to assess the possibility of using such thermosetting resins as a new eco-friendly material for engineering applications. Upon evaluation, it was found that the prepared resins systems exhibit better properties compared to commercial epoxy resin in term of increase in tensile strength, elongation-at-break and impact strength, of castings and gloss, scratch hardness, adhesion and flexibility of the films. The anticorrosive properties from chemical resistance of the prepared resin systems are found to be superior than unmodified epoxy resins. The TG/DTG thermograms showed two step decomposition behaviors in all the prepared samples.

Studies on mechanical and thermal properties of ternary blends of polyethylenes having fixed percentage of high-density polyethylene - II

Six film samples of varying compositions of low-density polyethylene (LDPE); (20–45 wt%) and linear low-density polyethylene (LLDPE); (25–45 wt%) having a fixed percentage of high-density polyethylene (HDPE) at 30 wt% have been extruded by melt blending in a single screw extruder (L/D ratio = 20:1) of uniform thickness of 2 mil. The tensile strength and elongation at break have been found to increase up to 40 wt% with LLDPE addition, starting from 25 wt% LLDPE, in the blends and then decreased. The blend sample containing 30 wt% LDPE, 40 wt% LLDPE, and 30 wt% HDPE (sample C-300) was found to be more thermally stable blend amongst all the prepared blends. In most of the blends, two exothermic peaks appeared that showed the formation of immiscible blend systems; this was further confirmed by scanning electron microscopic (SEM) analysis.

Ternary Blended Polyethylene Films: A Study on Its Mechanical and Thermal Properties

Six film samples of varying compositions of low-density polyethylene (LDPE) (40–70 wt%) and high-density polyethylene (HDPE) (5–35 wt%) having a fixed percentage of linear low-density polyethylene (LLDPE) at 25 wt% have been extruded by melt blending in a single-screw extruder (L/D ratio=20:1) of uniform thickness of 2 (mil). The mechanical and thermal properties of these films were evaluated. The tensile strength has been found to increase up to 25 wt% HDPE addition in LDPE and then decreased, whereas the elongation at break decreased up to 20 wt% addition of HDPE in the blend and then increased up to 55 wt% addition. The impact failure load increased with the HDPE content in the blend up to 25 wt% addition and then decreased. The initial degradation temperature has been evaluated for a blend composition having LDPE:LLDPE:HDPE=50:25:25 from thermogravimetric analysis and it was found to be 310°C. Differential scanning calorimetric analysis was also performed for all composition ranges to investigate the effect of melting temperature with HDPE content in LDPE. The morphology of this blend composition was investigated by scanning electron microscopic analysis.

Mechanical, chemical, and curing characteristics of cardanol–furfural-based novolac resin for application in green coatings

The present research work focuses on the mechanical, chemical, and curing characteristics of novolac resin based on renewable resource materials such as cardanol and furfural. Cardanol, a metasubstituted phenol, is a renewable organic resource obtained as a byproduct of the cashew industry. Furfural, an aromatic aldehyde, is also a renewable resource obtained as an agricultural waste product. Novolac resin has been synthesized by the condensation of cardanol with furfural in the presence of an oxalic acid catalyst and using varied molar proportions of the reacting monomers. The reaction was performed at 120°C. The progress of the reaction was monitored by determining the free formaldehyde and free phenol content. The prepared cardanol–furfural-based novolac resins were further characterized by various techniques such as infrared and nuclear magnetic resonance spectroscopic analysis. The resins were cured using the most suitable agent, hexamethylenetetramine. The differential scanning calorimetric technique was used to investigate the curing behavior of the prepared samples. The cured film samples were used for the determination of mechanical properties such as adhesion, flexibility, scratch hardness, gloss, and impact resistance; these cured film samples were also used to observe the effect of various chemicals and solvents (chemical resistance properties) such as sulfuric acid, acetic acid, sodium hydroxide, sodium carbonate and methanol, methyl ethyl ketone, xylene, and deionized water, respectively, on the surface of the film. The resulting coatings based on prepared cardanol–furfural resin were found to have excellent mechanical and chemical resistance properties.

Compatibility, thermal, mechanical and morphological properties of cardanol based epoxidized resin modified with liquid rubber

An epoxy resin based on cardanol and varying content of CTBN was cured using polyamine as a hardener. The ultimate aim of the study was to modify the brittle epoxy matrix by the liquid rubber to improve toughness characteristics. FTIR of the modified was performed to understand the structural transformations taking place during the uncured and cured stage of the modified systems. Also, the structures were proposed on the basis of the results of NMR and MALDI-TOF mass spectroscopic analysis along with GPC analysis. Mechanical properties of neat as well as modified networks have been studied to observe the effect of rubber modification. The improvement in these properties indicates that the rubber-modified resin would be more durable than the pure epoxy based on cardanol. A clear-cut two-step mass loss in dynamic thermogravimetric trace of unmodified and CTBN-modified systems was observed. Modified cardanol based epoxy network displayed two phase separated morphology.

Decomposition behavior of vinyl ester resins prepared in presence of tertiary amines

Vinyl ester resins V1, V2, and V3of acid value (∼6 mg KOH/g solid) were synthesized using bisphenol-A epoxy and acrylic acid in the presence of triethyl, tripropyl, and tributyl amines, respectively. The synthesized resins were characterized by Fourier transform infrared spectroscopy and a new peak at 2360 cm−1was observed due to attachment of amines to resin structure by a hydrogen bond. All the resins containing styrene (40% w/w) as reactive diluent were cured with benzoyl peroxide (2 phr) at 90°C for 1 hr. Decomposition behavior of the samples was studied by dynamic thermogravimetry at a heating rate of 10°C min−1under nitrogen atmosphere. For all the samples, the order of reaction was found to be 1. This was calculated using Coats and Redfern equation in accordance with best-fit analysis and was confirmed further by linear regression analysis. From this value of reaction order, activation energy (E) and pre-exponential factor (Z) were calculated. The activation energy increases from 25.90 to 30.72 kcal mol−1for V1to V3. The validity of data was checked by t-test statistical analysis.

Fullerene as radical inhibitor in polymerization of acrylonitrile initiated by arsonium ylide

Kinetics of polymerization of acrylonitrile (AN) in presence of fullerene (C60) has been studied using p-acetyl benzylidine triphenyl arsonium ylide as initiator in dioxane at 60 ± 0.1°C under the blanket of nitrogen. The rate of polymerization (R p ) at low concentration of fullerene may be represented as R p ∝ [Ylide]0.5[AN]1.0 [Full]−0.6, indicating inhibition effect of fullerene on the polymerization. The energy of activation for the polymerization was found to be 71.5 ± 0.5 kJ mol−1. Fourier transform infrared spectroscopic analysis (FTIR) confirmed the insertion of fullerene in to the final polymer. The mechanism for the polymerization has also been proposed.