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Processing Aid (processing + aid)
Selected AbstractsIMPROVED VIABILITY OF SPRAY DRIED BREWER'S YEAST BY USING STARCH (GRITS) AND MALTODEXTRIN AS PROCESSING AIDSJOURNAL OF FOOD PROCESS ENGINEERING, Issue 6 2000GUADALUPE LUNA-SOLANO ABSTRACT Active dry brewer's yeast was prepared by spray drying (Tout 50 and 60C). Addition of processing aids to the yeast cream was necessary in order to dry at these temperatures. Corn starch (grits) and maltodextrins (DE-6) two levels of additions (10 and 20%) were used as processing aids. Statistical analyses proved that processing aids concentration, air outlet temperature and rotor speed had significant effects on yeast viability. Dried samples could be preserved at least 4 months stored at 5 and 25C with a loss of 1 and 2 log cycles of viable cells, respectively. [source] Reactive processing of syndiotactic polystyrene with an epoxy/amine solvent systemMACROMOLECULAR SYMPOSIA, Issue 1 2003Jaap Schut Abstract Syndiotactic polystyrene (sPS) is a new semi-crystalline thermoplastic which is believed to fill the price-performance gap between engineering and commodity plastics. In order to reduce the high processing temperature of sPS (>290°C), an epoxy-amine model system was used as a reactive solvent. Such a processing aid can be used to achieve a 50 to 500 fold lowering of the melt viscosity. When initially homogeneous solutions of sPS in a stoechiometric epoxy-amine mixture are thermally cured, Reaction Induced Phase Separation (RIPS) takes place, leading to phase separated thermoplastic-thermoset polymer blends. We focus our study on low (wt% sPS < 20%) and high concentration blends (wt% sPS > 60%) prepared by two processing techniques (mechanical stirring in a laboratory reactor or internal mixer/ reactive extrusion respectively). These blends have different potential interests. Low concentration blends (sPS domains in an epoxy-amine matrix) are prepared to create new, tunable blend morphologies by choosing the nature of the phase separation process, i.e. either crystallisation followed by polymerization or polymerization followed crystallisation. High concentration blends (sPS matrix containing dispersed epoxy-amine particles after RIPS) are prepared to facilitate the extrusion of sPS. In this case, the epoxy amine model system served as a reactive solvent. The time to the onset of RIPS is in the order of 7-9 min for low concentration blends, while it increases to 20-45 min for high concentration samples, as the reaction rates are substantially slowed down due to lower epoxy and amine concentrations. During the curing reaction the melting temperature of sPS in the reactive solvent mixture evolves back from a depressed value to the level of pure sPS. This indicates a change in the composition of the sPS phase, caused by (complete) phase separation upon reaction. We conclude that our epoxy amine system is suited for reactive processing of sPS, where final properties depend strongly on composition and processing conditions. [source] Effect of diatomite/polyethylene glycol binary processing aid on the melt fracture and the rheology of polyethylenesPOLYMER ENGINEERING & SCIENCE, Issue 7 2005Xiaolong Liu The influence of polyethylene (PE) glycol (PEG), diatomite, and diatomite/PEG binary processing aid (BPA) on the rheological properties and the sharkskin melt fracture of three PEs was studied using a capillary rheometer. When diatomite or PEG is added to the PE matrix, they have little effect on the viscosity reduction of PEs, while the diatomite/PEG BPA shows a synergetic effect on the viscosity reduction of PEs. The incorporation of small amount of BPA was found to increase the shear-thinning behavior and decrease the melt viscosity significantly. Meanwhile, the critical apparent shear rate for the onset of sharkskin melt fracture of PEs is increased. The mechanism for BPA to improve the rheological properties and the melt flow instability of PEs was discussed. POLYM. ENG. SCI., 45:898,903, 2005. © 2005 Society of Plastics Engineers [source] The effect of surface energy of boron nitride on polymer processabilityPOLYMER ENGINEERING & SCIENCE, Issue 8 2004Nimish Rathod Flow instabilities manifest themselves as distortions on the extrudate surface (melt fracture). They are usually observed at high production rates in many polymer processing operations. Certain fluoropolymers/fluoroelastomers have long been used as processing aids for surface melt fracture elimination. Recent developments have shown that a small amount of boron nitride (BN) powder may successfully eliminate surface melt fracture and also delay the onset of gross melt fracture to higher rates. It has also been reported that a combination of BN and fluoropolymer/fluoroelastomer enhances the effectiveness of the polymer processing even further. The main objective of the present work was to measure the surface properties of a number BN powders, mainly surface energy, in order to gain a better understanding of its performance as a processing aid. Based on this study, it can be concluded that surface energy plays an important role in deciding the possible interactions between the processing aid, polymer melt and the extruding surface. It is observed that the lubricious nature of BN along with an optimum balance of its polar (non-dispersive) and non-polar (dispersive) components of surface energy renders BN a successful processing aid in eliminating both sharkskin and gross melt fracture phenomena. Polym. Eng. Sci. 44:1543,1550, 2004. © 2004 Society of Plastics Engineers. [source] IMPROVED VIABILITY OF SPRAY DRIED BREWER'S YEAST BY USING STARCH (GRITS) AND MALTODEXTRIN AS PROCESSING AIDSJOURNAL OF FOOD PROCESS ENGINEERING, Issue 6 2000GUADALUPE LUNA-SOLANO ABSTRACT Active dry brewer's yeast was prepared by spray drying (Tout 50 and 60C). Addition of processing aids to the yeast cream was necessary in order to dry at these temperatures. Corn starch (grits) and maltodextrins (DE-6) two levels of additions (10 and 20%) were used as processing aids. Statistical analyses proved that processing aids concentration, air outlet temperature and rotor speed had significant effects on yeast viability. Dried samples could be preserved at least 4 months stored at 5 and 25C with a loss of 1 and 2 log cycles of viable cells, respectively. [source] Role of processing aids in the extrusion of molten polymers,JOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 1 2002E. C. Achilleos Product quality and, in general, processing windows and rates of production in the extrusion of molten polymers are limited by various flow instabilities (mainly melt fracture) that are observed at high production rates. While there still are unresolved issues in comprehending these phenomena, industry demands for process optimization dictate the employment of processing aids (PAs) for product quality improvement and energy requirement reduction. In this review paper, most commercially used processing aids (PAs) are discussed, namely, fluoroelastomers, stearates, small amounts of polymers blended with the process polymer, and the newly discovered boron nitride as pure and in combination with other fluoroelastomers. This paper focuses on the appropriate and optimum usage of the various PAs as well as on the mechanism that underlies their action for flow enhancement and instability elimination. Finally, numerous experimental observations are discussed, and several examples are illustrated. [source] The effect of surface energy of boron nitride on polymer processabilityPOLYMER ENGINEERING & SCIENCE, Issue 8 2004Nimish Rathod Flow instabilities manifest themselves as distortions on the extrudate surface (melt fracture). They are usually observed at high production rates in many polymer processing operations. Certain fluoropolymers/fluoroelastomers have long been used as processing aids for surface melt fracture elimination. Recent developments have shown that a small amount of boron nitride (BN) powder may successfully eliminate surface melt fracture and also delay the onset of gross melt fracture to higher rates. It has also been reported that a combination of BN and fluoropolymer/fluoroelastomer enhances the effectiveness of the polymer processing even further. The main objective of the present work was to measure the surface properties of a number BN powders, mainly surface energy, in order to gain a better understanding of its performance as a processing aid. Based on this study, it can be concluded that surface energy plays an important role in deciding the possible interactions between the processing aid, polymer melt and the extruding surface. It is observed that the lubricious nature of BN along with an optimum balance of its polar (non-dispersive) and non-polar (dispersive) components of surface energy renders BN a successful processing aid in eliminating both sharkskin and gross melt fracture phenomena. Polym. Eng. Sci. 44:1543,1550, 2004. © 2004 Society of Plastics Engineers. [source] Comprehensive Review of Campylobacter and Poultry ProcessingCOMPREHENSIVE REVIEWS IN FOOD SCIENCE AND FOOD SAFETY, Issue 2 2004K.M. Keener ABSTRACT Campylobacter has been recognized as a leading bacterial cause of human gastroenteritis in the United States, with 40000 documented cases annually. Epidemiological data suggest that contaminated products of animal origin, especially poultry, contribute significantly to campylobacteriosis. Thus, reduction of contamination of raw poultry would have a large impact in reducing incidence of illness. Contamination occurs both on the farm and in poultry slaughter plants. Routine procedures on the farm such as feed withdrawal, poultry handling, and transportation practices have a documented effect on Campylobacter levels at the processing plant. At the plant, defeathering, evisceration, and carcass chillers have been documented to cross-contaminate poultry carcasses. Carcass washings and the application of processing aids have been shown to reduce populations of Campylobacter in the carcasses by log10 0.5 log10 1.5; however, populations of Campylobacter have been shown to enter a poultry processing plant at levels between log10 5 colony-forming units (CFU)/mL and log10 8 CFU/mL of carcass rinse. The purpose of this article is to review Campylobacter, the infection that it causes, its association with poultry, contamination sources during processing, and intervention methods. [source] | ||||||||||