A design of experiments study on the factors affecting variability in the melt index measurement

Melt index (MI) is universally accepted as the primary specification in the thermoplastics industry. The standard according to which the MI measurement is made is ASTM D-1238. However, some variation in the MI measurement is possible, even when all ASTM D-1238 specifications are met. A thorough understanding of the sources and magnitude of variation is essential, since measurement error can have significant economic implications. Error in the MI measurement can cause a resin lot (about 190,000 pounds) to be erroneously classified as off-spec (leading to a loss of over US $20,000). A Resolution IV, six-factor, 1/4 fractional factorial design of experiments (DOE) study [with three replicates] was done to quantify the effect of various factors affecting variability in the MI measurement using two high-density polyethylene monitor resins with MI of 1.91 g/10 min (“low” MI) and 36.4 g/10 min (“high” MI). A major challenge was dealing with qualitative (e.g., “cleanliness”) and quantitative (e.g., “sample mass” or “temperature”) factors in the same DOE. For the high MI monitor, among the factors considered, the most significant (for the ranges considered) were found to be (in the order of importance): die orifice diameter, temperature, die cleanliness, barrel cleanliness, and sample mass. The following factors were also considered but not found (in the ranges considered) to be as significant: piston land (tip) diameter, load, piston cleanliness, preheat time, and piston curvature. For the low MI monitor, among the factors considered, the two most significant (for the ranges considered) were temperature and barrel cleanliness. This article gives practical and useful information for those who make and/or use MI measurements. As others have pointed out, much of such discussion related to melt indexers is also applicable to more sophisticated capillary rheometers. © John Wiley & Sons, Inc. J Appl Polym Sci 65:277–288, 1997     

Comparative stability of aspartame and neotame in yoghurt

The comparative stability of aspartame and neotame was monitored in yoghurt during its processing, fermentation and storage. A solid‐phase extraction method was suggest changing it to developed for the isolation of aspartame and neotame. Pasteurisation (85 °C/30 min) resulted in approximately 47% and 3% loss of aspartame and neotame, respectively. During fermentation, 3% loss of aspartame was observed, but no loss of neotame. There was no significant effects on the stability of either aspartame or neotame during storage (4–7 °C/15 days). The results indicated that neotame was more stable than aspartame under both pasteurisation and fermentation conditions; however, during storage, both sweeteners exhibited excellent stability.     

Optimisation of a process for production of pomegranate pulp and flaxseed powder fortified probiotic Greek dahi

Fortified probiotic Greek dahi was formulated with pomegranate pulp (PP) and flaxseed powder (FP). The product variables, viz. PP, FP and incubation time, were optimised based on chemical, sensory and textural attributes. The study revealed that PP significantly affected the acidity and antioxidant content, while FP influenced the sensory and textural properties of the product. The optimum conditions were 15% PP, 2% FP and 12‐h incubation time. The developed fortified probiotic Greek dahi is a potential synbiotic food.     

Experimental Investigation and optimization of Process Parameters for Shear Strength of Compound Cast Bimetallic Joints

Joining of A356 alloy and magnesium was carried out by vacuum assisted sand mold compound casting process. Microstructure at the joint interface was studied by using optical microscope, scanning electron microscope, energy dispersive X-ray spectroscopy and X-ray diffractometer. Characterization indicated that a relatively uniform joint interface was obtained. The joint interface was composed of three distinct layers containing Mg₂Al₃ on aluminum side, Mg₁₇Al₁₂?+?δ eutectic structure on magnesium side and Mg₁₇Al₁₂ as middle layer. As a result of interaction between silicon, present in A356 with magnesium, Mg₂Si compound was formed. Push out test was conducted on electronics universal testing machine to measure the shear strength across the joint interface. The important process parameters (grit size of sand paper, insert temperature, pouring temperature and vacuum pressure) were optimized to maximize the shear strength. Optimization was carried out by using response surface methodology, desirability analysis and genetic algorithm (GA) techniques. It was observed that the shear strength increased by 14.21, 8.60 and 4.80% with genetic algorithm, desirability analysis and regression model respectively. GA reported the optimal value of shear strength.     

GA Approach for Optimization of Surface Roughness Parameters in Machining of Al Alloy SiC Particle Composite

Experiments were carried out using carbide turning inserts on AA7075/10?wt.% SiC (particle size 10-20???m) composites to get actual input values to the optimization problem, so that the optimized results are realistic. By using experimental data, the regression model was developed. This model was used to formulate the fitness function of the genetic algorithm (GA). This investigation attempts to perform the application of GA for finding the optimal solution of the cutting conditions minimum value of surface roughness. The analysis of this investigation shows that the GA technique is capable of estimating the optimal cutting conditions that yield the minimum surface roughness value. With the highest speed, the lowest feed rate, the lowest depth of cut, and the highest nose radius of the cutting conditions' scale, the GA technique recommends 1.039???m as the best minimum predicted surface roughness value. This means that the GA technique has decreased the minimum surface roughness value of the experimental sample data, regression modeling and desirability analysis by about 3%, 1%, and 2.8%, respectively.     

Numerical investigation of hydrogen absorption in a stackable metal hydride reactor utilizing compartmentalization

In this paper, a three-dimensional model for hydrogen absorption in a metal alloy has been developed, validated against the experimental data in the literature, and then applied to a novel design for a hydrogen storage unit. The proposed design is similar to the fuel cell stack, but here the Membrane Electrode Assembly (MEA) has been replaced by a metal hydride (MH) reactor placed between the flow-field plates. These are stacked together to achieve the required amount of hydrogen storage. The flow-field plates have channels engraved on one side for hydrogen supply and on the other, for coolant/heating medium. It is known that the effectiveness of a hydrogen storage unit is directly related to its heat transfer area, and therefore, the choice of its geometry is very important. The larger the size, the more the resistance to heat transfer. Although, the internal tubular heat exchangers have proven to be effective in heat transfer, they pose severe challenges such as cooling/heating medium leakage due to tube erosion, stresses generated, etc. and they displace the active metal hydride from the tank. The present stacked MH reactor configuration helps to overcome these challenges by stacking small MH reactors together and there is no chance of the cooling/heating medium leaking into the metal hydride. Numerical simulations were performed to investigate the effect of coolant flow rate and percentage of flow-field plate rib area exposed to the MH reactor on temperature evolution and the amount of hydrogen stored. Further, a detailed study was carried out to understand the effect of compartmentalization of the MH reactor on temperature distribution. The results revealed that compartmentalization substantially helps to uniformly distribute the temperature in the metal bed, which is very important to maintain uniform utilization of the metal powder. Consequently, the uniform metal powder density for repeated absorption-desorption cycles without significant loss of its hydrogen storage capabilities.     

Removal of 17α‐ethinylestradiol,salicylic acid,trimethoprim, carbamazepine and nonylphenol through biological carbon and nitrogen removal processes

This study investigated five different trace organic contaminants (TOrCs) (one hormone: 17α‐ethinylestradiol (EE2), two pharmaceuticals: salicylic acid (SA) and trimethoprim (TMP), one analgesic drug: carbamazepine (CBZ), and one surfactant metabolite: nonylphenol (NP)) removal efficiency at a full‐scale Advanced Wastewater Treatment Plant (AWTP). The AWTP achieved average EE2, SA and NP removal over 80% at the biological carbon removal stages. The results also showed a 66% removal of TMP at the nitrogen removal stages. CBZ was recalcitrant throughout the plant, due to its high solubility and low distribution coefficient between wastewater and sludge. Batch experiments were conducted on active and inactive secondary, nitrification and denitrification sludge by adding TOrCs to understand the removal mechanism through sorption and biodegradation. Sorption was the dominant mechanism to remove EE2, SA and NP in secondary treatment processes. In nitrification and denitrification processes, higher percentage of TOrCs removal through biodegradation were observed compared to removal through sorption.     

Reduction of Escherichia coli O157:H7 population on baby spinach leaves by liquid sanitizers

The effectiveness of various liquid sanitizers and methods of application against Escherichia coli on baby spinach was investigated. Inoculated spinach was treated with (i) Pro‐San L (commercially prepared solution containing 0.66% citric acid, 0.036% sodium dodecyl sulfate (SDS); (ii) chlorine solution (200 ppm), alone or with addition of 0.036% SDS; and (iii) aqueous solution of 0.66% levulinic acid with 0.036% SDS. Population reduction in response to these treatments ranged between 2.1 and 2.8 log CFU/g. No significant difference (p > .05) was found among tested sanitizers in microbial count reduction. Spraying, dipping, and “dry” vacuum impregnation methods of Pro‐San L application were compared. Dipping was the most effective in reducing E. coli O157:H7 population (4.4 log CFU/g reduction). Dry vacuum impregnation was less effective (3.3 log CFU/g reduction) and caused damage to the produce. The effectiveness of spray Pro‐San L application and holding for prolonged time (up to 3 days) was also evaluated. However, increasing time of exposure to organic acid sanitizer did not increase sanitizing effectiveness and led to progressive damage of spinach leaves.     

Production and structural characterisation of dextran from an indigenous strain of Leuconostoc mesenteroides BA08 in Whey

In this work, the production of dextran was carried out in whey‐supplemented media using Leuconostoc mesenteroides BA08. Different growth and nutritional parameters were optimised to maximise the dextran production. Batch production in whey‐based media under optimised nutritional and growth conditions yielded a dextran concentration of 17.25 g/L. Structural analysis of the purified polymer by FT‐IR, 1D ¹H and ¹³C nuclear magnetic resonance methodology revealed that polymer was a linear dextran having 93% α‐(1→6) linkage in the main chain. The morphology of the dried dextran and dextran‐producing cells was also studied by scanning electron microscope which showed a granular and porous or weblike structure, respectively. The results obtained showed that the industrial whey supplemented with nutrients such as sucrose, yeast extract and K₂HPO₄ can serve as an ideal growth medium for dextran production. The optimised fermentation and nutritional parameters can be further scaled up to establish the potential for the commercial production of food‐grade dextran from whey as part of a novel cost‐effective and environment‐friendly approach.