Wachstumsmessungen von Kristallen in sauberen und verunreinigten Lösungen: Einzelkristall vs. Kollektiv

Information about crystal growth rates and the influence of impurities are essential for the design of industrial crystallization processes. Here, the influence of trivalent metal ions Fe³⁺ in solution and adsorbed in the crystal on the growth and dissolution rate is investigated. The results clearly show kinetic and thermodynamic effects caused by impurities which have to be taken into account in the equipment design. Furthermore, effects of growth rate dispersion must be excluded by investigation of crystal collectives. Additionally, the crystal growth data should be obtained from real starting solutions.     

On the use of a powder rheometer to characterize the powder flowability at low consolidation with torque resistances

The Anton Paar Powder Cell was used to measure the torque necessary to rotate an impeller in beds of glass beads, sand and alumina powders aerated between no aeration to the minimum for fluidization. Measured torque values depend on the material tested, on the air flow rate applied, on the impeller depth and on the height of the impeller blade. The effect of the impeller depth is linear for low impeller depth and is less than linear at high depth values. A model was developed for the interpretation of the experimental results based on the idea that the material is shearing on the surface described by the impeller rotation. The model allows to estimate an effectiveness of the impeller in the torque determination and also to predict the torque for the impeller at the at deepest positions at which the wall effects have to be considered. © 2017 American Institute of Chemical Engineers AIChE J, 2017     

Progress in Carbon Fiber and Its Polypropylene- and Polyethylene-Based Composites

Due to their lightweight and excellent toughness, carbon fiber (CF) and its reinforced thermoplastic composites are suitable for high-performance applications such as aerospace, aviation, automotive and sport equipments. In this study, comprehensive detail is provided on the production of carbon fiber, its various forms and geometry and their corresponding effects on the mechanical properties of CF and its reinforced polypropylene (PP) and polyethylene (PE) composites. Here we discuss extensively various methods reported in literature on improving the interfacial fiber-matrix adhesion and dispersion in order to achieve better mechanical properties for such composites.     

Weather-Induced Degradation of Plastic Pipes

A number of plastic materials, such as unplasticized poly(viny1 chloride) (uPVC), acrylonitrile-butadiene-styrene (ABS), high-density polyethylene (HDPE), poly-(vinylidene fluoride) (PVDF), and chlorinated poly(viny1 chloride) (cPVC), are available for numerous applications. uPVC and HDPE pipes are used in pressurized piping systems in Saudi Arabia for industrial, agricultural, domestic, and general-purpose applications. Some studies have been carried out to investigate the causes of failure in plastic pipes, which is very high in the area. In this chapter an overview of the failure of plastic pipes is presented, with emphasis given to failure of pipes due to severe weather conditions in Saudi Arabia.     

Optimal design and operation of a steel plant integrated with a polygeneration system

A process integration approach has been applied to integrate a traditional steelmaking plant with a polygeneration system to increase energy efficiency and suppress carbon dioxide emissions from the system. Using short‐cut models and empirical equations for different units and available technologies for gas separation, methane gasification, and methanol synthesis, a mixed integer nonlinear model is applied to find the optimal design of the polygeneration plant and operational conditions of the system. Due to the complexity of the blast furnace (BF) operation, a surrogate model technique is chosen based on an existing BF model. The results show that from an economic perspective, the pressure swing adsorption process with gas‐phase methanol unit is preferred. The results demonstrate that integration of conventional steelmaking with a polygeneration system could decrease the specific emissions by more than 20 percent. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3659–3670, 2013     

Miscibility study of chitosan/polyethylene glycol fumarate blends in dilute solutions

Solution miscibility of chitosan/polyethylene glycol fumarate blends dissolved in acetate buffer solution was investigated in different blend compositions by viscosity, density, and refractive index measurement techniques at 30, 40, and 50°C. In order to quantify the miscibility of the polymer pair, degree of miscibility was studied by means of two criteria known as interaction parameters i.e., μ and α. On the basis of the sign convention involved in these criteria, these values revealed that the blend solution was miscible when the chitosan content was more than 80% (w/w) of the composition. The results were confirmed by density, and refractive index measurements. Furthermore, the results showed that the miscibility window of chitosan/polyethylene glycol fumarate blends was independent with respect to the changes in solution temperature. Therefore, these results suggested due to intermolecular hydrogen‐bonding interaction between amino and hydroxy groups of chitosan and hydroxy groups of polyethylene glycol fumarate which play an important role in the formation of miscible phase. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Modification of Theoretical models to predict mechanical behavior of PVC/NBR/organoclay nanocomposites

Organo‐modified nanoclay (Cloisite 30B) was added via direct melt mixing to the acrylonitrile butadiene rubber/poly(vinyl chloride) (PVC/NBR) to fabricate polymer blend/clay nanocomposites. The states of nano‐fillers dispersion were investigated by transmission electron microscopy (TEM) and X‐ray diffraction (XRD). From the morphological study of nanocomposites, it is concluded that exfoliated morphology is obtainable by introduction of 2.5 vol % of nanoclay. The effect of nano‐filler volume content on the mechanical properties of PVC/NBR matrix reinforced by Cloisite 30B was investigated by tensile test. Experimental results show that the Young's modulus and tensile strength of composites can significantly improved with a small amount of nanofiller. Moreover, to investigate the stress–strain behavior of NBR/PVC nanocomposites, seven constitutive models such as Arruda–Boyce, Mooney–Rivilen, Marlow, second order of polynomial, Van der Waals, and third order Odgen were studied and compared with experimental data. Results showed that Malow and second order polynomial model can be used for nanoclay‐filled compound whereas the other models show more deviation from experimental data. Three micromechanical models named liner rule of mixtures (LROM) and the inverse rule of mixtures (IROM). Halpin–Tsai theory was applied to evaluate the dependence of Young modulus of nanocomposites on volume fraction of nanofiller. Two modifying factors were proposed to evaluate the Young's modulus of nanocomposites which could greatly improve the theoretical prediction obtained from inverse rule of mixtures (IROM) and Halpin–Tsai equation. The modifying factors were introduced by adopting an exponential, power‐law and linear factors in the equation. In order to verify the suitability of the modified models, the ensuing theoretical predictions are compared to the other experimental data available in the literature. Good predictability of the modified models is demonstrated in the results. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3229–3239, 2013