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This article focuses on important aspects related to the production of acrylonitrile-butadiene rubber (nitrile rubber or NBR) emulsions using a train of eight continuously stirred tank reactors. The first aspect we discuss concerns miscellaneous operating procedures, targeted toward achieving desired properties of the NBR emulsion and at the same time reducing the amount of off-spec material during the transient period. In one of the operating procedures discussed, the first reactor is started full of 'batch recipe,' whereas the remaining reactors in the train are half full with all reaction ingredients. In another case, we discuss an alternative design scenario, where the first reactor in the train is of a much smaller volume compared with the following reactors. The benefits of these two operating (production) scenarios are illustrated by comparison of different polymer and latex properties obtained with the commonly used procedures. Second, we discuss a novel criterion that can quantitatively distinguish between Cases I and II kinetics emulsion polymerization behavior with respect to continuous reactor stability (oscillatory behavior). Finally, additional feed policies are addressed, such as splitting the more reactive monomer and/or other reaction ingredients among the reactors of the train for better control of certain desired properties. POLYM. ENG. SCI., 53:9-20, 2013. © 2012 Society of Plastics Engineers, INTRODUCTION Acrylonitrile (AN)-butadiene rubber (nitrile rubber or NBR) latexes are produced on a large scale using a train of 6-12 continuous stirred tank reactors (CSTRs). In addition to the advantage [...]

The first part of this article discusses different partitioning options used in modeling emulsion copolymerization of acrylonitrile and butadiene for the production of acrylonitrile-butadiene rubber (NBR) in batch and continuous reactors. It is observed that the performance of the model using different partitioning methods for estimation of monomer concentration in the different phases (i.e., droplet, aqueous and particle) would be very similar by proper selection of the different parameters of the particular partitioning method. In the second part, the effects of important aspects (during the continuous production of NBR) such as desorption and monomer soluble impurities on polymer properties are discussed. The third part of the paper focuses on procedures and benefits of different kinds of reactor start-ups, such as starting the reactor(s) full of water, half full of water, full of 'batch recipe' or empty. All of the above studies and analysis are targeted towards their effect on principal emulsion polymer characteristics such as number-and weight-average molecular weights, monomer conversion, copolymer composition (bound acrylonitrile), tri-and tetra-functional branching frequencies, and number and average size of the polymer particles. POLYM. ENG. SCI., 51:1909-1918, 2011. © 2011 Society of Plastics Engineers, INTRODUCTION Acrylonitrile-butadiene rubber (NBR) latexes are produced by emulsion copolymerization using reactors operated either in batch/semibatch or continuous modes based on demand and quality requirements. Although several mechanistic models have [...]

A process which comprised a tubular reactor (that can be packed with different internal structures) has been modeled and theoretically analyzed for conducting the hydrogenation of nitrile butadiene rubber (NBR). The dynamics of the tubular reactor and the intrinsic hydrogenation kinetics are coupled, and detailed numerical simulations are performed under isothermal and isobaric conditions. The proposed model thus obtained involves coupled, nonlinear, partial differential equations (distributed parameter system). The effect of different reactor design parameters such as Peclet number, carbon-carbon double bond loading, mass transfer to reaction resistance, and solubility of hydrogen with respect to hydrogenation of the NBR has been investigated numerically. The conversions predicted using the proposed model for tubular packed bed reactor are compared with those possible in conventional plug flow reactor and continuous stirred tank reactor models. The optimal parameters and operating conditions for efficient production of hydrogenated NBR are suggested. Finally, the validity of the proposed model is confirmed by comparing the predicted and the experimental degree of hydrogenation obtained in a tubular reactor packed with Intalox saddles. POLYM. ENG. SCI., 49:1979-1989, 2009. © 2009 Society of Plastics Engineers, INTRODUCTION Hydrogenated nitrile butadiene rubber (HNBR), which is known for its excellent elastomeric properties and mechanical retention properties after long time exposure to heat, oil, and air, is produced by [...]

A major issue concerned with using synthetic polymers as packaging materials is the difficulty in the disposal or reuse which in turn is leading to environmental pollution. Design of eco‐friendly alternative materials or modified polymers is being done to overcome or address this issue. In this article, a design is proposed of a new cellulose derivative which consists of cellulose layered with nonacosan‐10‐ol and nonacosane‐5,10‐diol molecules targeted toward achieving superior nonwettability while assuring both physical strength and reusability. An atomistic model of this new material (called as Adulose from now) that had 24 cellulose chains and 48 molecules of each of the other wax materials is used in this study. Molecular dynamic simulations are performed on this material using LAMMPS software at 0 atm and 300 K for an isothermal‐isobaric ensemble. The stress–strain behavior is studied by conducting deformation simulations while the contact angle simulations of this material are evaluated to confirm the nonwettability (or hydrophobicity). Preliminary simulations show that Adulose has very good mechanical properties like its ultimate stress value is almost similar to that of polyethylene and an average contact angle of over 150° is achieved from the simulations. [ABSTRACT FROM AUTHOR]

Chemical processes with complex reaction mechanisms generally lead to dynamic models which, while beneficial for predicting and capturing the detailed process behavior, are not readily amenable for direct use in online applications related to process operation, optimisation, control, and troubleshooting. Surrogate models can help overcome this problem. In this research article, the first part focuses on obtaining surrogate models for emulsion copolymerization of nitrile butadiene rubber (NBR), which is usually produced in a train of continuous stirred tank reactors. The predictions and/or profiles for several performance characteristics such as conversion, number of polymer particles, copolymer composition, and weight-average molecular weight, obtained using surrogate models are compared with those obtained using the detailed mechanistic model. In the second part of this article, optimal flow profiles based on dynamic optimisation using the surrogate models are obtained for the production of NBR emulsions with the objective of minimising the off-specification product generated during grade transitions. [ABSTRACT FROM AUTHOR]

Long glass fiber-reinforced polypropylene composites (LGFPP) are widely used in the industrial field, especially in automotive applications, due to their excellent mechanical properties and low cost. This article focuses on obtaining optimal mechanical properties of LGFPP for different objectives. The primary objective is to minimize the cost of the composite. The other objective is to obtain specific, desired properties of the composite (irrespective of the composite cost). The latter case is useful in designing products where quality of the composite cannot be compromised (while the cost of the composite is secondary). The properties that were optimized include tensile Young’s modulus, flexural Young’s modulus, and notched Izod impact. Surrogate models were obtained and used to predict these properties as functions of corresponding compositions of the composites. Furthermore, optimization framework that employs these models either as constraints or as objective functions was developed with the aim of developing tailored fiber-reinforced polypropylene. All simulations are programmed using MATLAB version 7.10.0 (R2010a). [ABSTRACT FROM PUBLISHER]

Bayesian design of experiments can be very useful for complex polymerizations and other chemical engineering processes. The technique has many practical benefits; it incorporates prior information, allows for adjustment of design levels, increases the information content, and optimizes experimental resources. In this work, Bayesian design is applied to the simulated emulsion copolymerization of NBR in a series of CSTRs. Statistical comparisons show that the Bayesian design is as good as (or better than) standard design techniques. This makes the Bayesian design superior overall, as it provides the extra flexibility of designing sequences of fewer trials and an increased information content. [ABSTRACT FROM AUTHOR]

Fuel cell technology is at the forefront of sustainable energy solutions, and polyvinyl alcohol (PVA) membranes play an important role in improving performance. This article thoroughly investigates the various varieties of PVA membranes, their production processes, and the numerous modification tactics used to solve inherent problems. Various methods were investigated, including chemical changes, composite blending, and the introduction of nanocomposites. The factors impacting PVA membranes, such as proton conductivity, thermal stability, and selectivity, were investigated to provide comprehensive knowledge. By combining various research threads, this review aims to completely investigate the current state of PVA membranes in fuel cell applications, providing significant insights for both academic researchers and industry practitioners interested in efficient and sustainable energy conversion technologies. The transition from traditional materials such as Nafion to PVA membranes has been prompted by limitations associated with the former, such as complex synthesis procedures, reduced ionic conductivity at elevated temperatures, and prohibitively high costs, which have hampered their widespread adoption. As a result, modern research efforts are increasingly focused on the creation of alternative membranes that can compete with conventional technical efficacy and economic viability in the context of fuel cell technologies.