Pultrusion die pressure response to changes in die inlet geometry

Pultrusion is a process of manufacturing composites that requires a high resin pressure rise in the tapered die inlet region. A sufficiently high pressure rise is important for a good quality pultruded product, thereby necessitating a study of the mechanisms affecting the die inlet pressure rise. Various process control parameters affect the resin pressure rise in the die inlet. The geometry of the tapered die inlet region can have a significant effect on the pressure rise in the pultrusion die. In this study a finite element model was developed to predict this pressure rise as a function of the tapered die inlet geometry. The composite matrix being pultruded was modeled on the assumptions of Darcy's laws for flow in porous media. A Galerkin's weighted residual based finite element technique was used to solve the governing equations. The pressure rise in the tapered inlet region of the die, as well as in the straight portion of the die, is predicted by this finite element model. Circular, parabolic, and wedge shaped die inlets have been modeled to compare their shapes on the resin pressure rise in the pultrusion die. Different angles for wedge shapes, different radii for circular shapes, and different foci for parabolic shapes were modeled to predict the influence of varying key geometrical parameters for each die inlet contour on pressure rise. The finite element model developed provides insight as to how to design the die inlet to produce a suitable pressure rise in the pultrusion die inlet.     

Two-layer tensioned-web-over-slot die coating: Effect of die lip geometry

Tensioned-web-over-slot die coating (TWOSD) takes advantage of the elastohydrodynamic interaction between the curved web under tension and the coating liquid to sustain a very small coating gap that enables ultra thin coating at relatively high speed. When the product requires two liquid layers, dual slot TWOSD coating can be used to coat those layers simultaneously. In this case, the liquid pressure along the coating bead sets not only the web configuration and meniscus locations but also the interlayer separation point. An easy way to control the pressure distribution is through the die lip geometry.Here, we analyze the effect of four different die lip geometric parameters, e.g. the downstream lip radius, the mid lip radius, the downstream lip offset and the mid lip apex point, on the coating window of the dual slot TWOSD coating. Using the model proposed by Nam and Carvalho (2009c) and a direct tracking of flow features, the boundaries of the vortex-free operating window, area inside the parameter spaces that ensure a uniform coating without vortex inside the flow, were obtained and compared for each die lip configuration.We found that the mid lip radius is one of the important parameters to control the location of the upstream meniscus. Also the location of the interlayer separation point can be controlled by the lip offset and location of the apex point.     

Über die Lipasen und die Lipolyse der Milch

Lipases and Lipolysis of Milk After a review of the latest literature in this field, the lipase-activity of the Finnish milk is dealt with. Extensive work was carried out on the isolation of lipases from milk, whose lipase-activities were known. Preliminary results have been obtained on the concentration and identification of the lipases. With partly purified lipase fractions, hydrolysis was observed in which different proportions of short and long chain fatty acids were liberated under varying conditions. These observations are of interest from the viewpoint of a possible use of lipases in the food technology.     

Über die Auswirkungen von Tensiden auf die Mundschleimhaut

Action of Surfactants on the Mucous Membrane of the Mouth Besides suitable brush and cleaning agents, a definite time is also required for the removal of mucoproteids, that are held rather rigidly on the tooth surface, thus forming matrix for tartar and pigment deposits. Mostly, a layman does not devote this amount of time for dental care. A proper dental care is one of the most important prophylactic measures against caries and paradentopathies. Extensive cytological investigations carried out for several years have shown that certain surfactants at concentrations below 2%, preferably between 1.2 and 1.5%, facilitate the cleansing without impairing the mucous membrane of the mouth.     

Über die Nitril-Carboxamid-Umlagerung und die Heterocyclenbildung aus 2-Cyancyclohexenylharnstoff

The Nitrile Carboxamide Rearrangement and the Formation of Heterocycles via Cyano-cyclohexenyl-urea Anthranilic amide and cyanogen bromide form Cyano-phenyl-urea ( 7 ) via Nitrile Carboxamide Rearrangement. Cyclisation of cyano-cyclohexenyl-urea ( 4 ) yields 4-amino-2,3,5,6,7,8-hexahydroquinazolin-2-one ( 10 ). 4 and amines form N-cyano-cyclohexenyl-N'-alkyl-ureas ( 11a–e ) or 3-alkyl-4-amino-hexahydroquinazolin-2-ones ( 12a–g ). 4 and α-aminoacids yield octahydro-imidazolo-quinazolindiones ( 14a–b ). Oxo-cyclohexane-2-carboxamide ( 1 ) and amino benzimidazole form hexahydrobenzimidazo-quinazolinone 17 .     

Investigation of the relationships between die build up and die swell

Die build up (DBU) is a common problem encountered during extrusion of polymers where material accumulates around the die exit and may cause defects in the surface of the product. This study was initiated to better understand the fundamental relationships between DBU and die swell. The study was conducted on a strand die extrusion system using an ethylene‐octene polyolefin elastomer resin. This study demonstrated that die swell is not a root cause of DBU. It was shown that at constant shear rate, increasing the die L/D ratio results in an increase in DBU, while die swell decreases. The important variables influencing DBU for the resin used in this study were: the shear rate or shear stress in capillary portion of the die, the nominal residence time that the resin is exposed to the high shear stress in the die capillary, and the concentration of oligomers present in the resin or generated during processing. These data support the conclusion that DBU is due to the shear‐induced migration of oligomeric species in the polymer to the die surface. Higher shear rates and stresses in the die promote this migration and result in a higher concentration of oligomeric species near the die wall. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers     

Flow in tensioned-web-over-slot die coating: Effect of die lip design

Tensioned-web-over-slot die (TWOSD) coating is one of the most successful high-speed liquid coating process. It deploys elastohydrodynamic interaction to control the distance between the moving substrate and the coating die lip surface in order to be able to coat an ultra-thin liquid layer. However, flow instabilities that come from the gas–liquid interface and microvortices inside the flow may lead to coating defects. Therefore, the range of operating conditions of uniform coating is limited. The operating window of the process is a strong function of the geometry of the die. However, this relationship and, in general, the fundamental mechanisms of the elastohydrodynamic interaction are not known. In this study, we analyze TWOSD coating flow by solving the Navier–Stokes equation coupled with thin cylindrical shell equation using the finite element method. The boundaries that define the regions in the parameter space of uniform coating are automatically computed by a direct tracking method, based on multi-parameter continuation. The results show that the coating window of the process can be enlarged by designing the appropriate lip geometry.     

Correlation between die opening gauge and die swell for steel-rubber composite extrusion

Steel-belted tires are usually made by extruding rubber onto a bank of wires. The resulting steel-polymer composite must meet a gauge specification. However, the composite swells extensively after leaving the die throat, taking on a more or less corrugated appearance. This paper presents an experimental study to understand the influences different parameters have on die swell for this sort of extrusion. Basically, the experiment is conducted to correlate die opening gauge to die swell. Parameters that affect die swell extrudate expansion are identified and investigated. Die opening is varied throughout the experimental process, and the die opening and belt gauge are measured to calculate die swell. To achieve a more uniform gauge across the width of the belt, the die throat opening is divided into five zones. Each zone of each die throat is considered. Experimental parameters held constant include wire parameters, polymer parameters, and setup parameters. The experimental data result in an overall plot of die swell percent vs. die throat opening gauge. This plot can be used as a guideline for predicting required gauge opening in a steel belt gauge development. The study shows that die swell percents for extruded belts is more predictable than previously thought, and debunks the notion that die swell percent is constant. With regard to the time and effort for optimizing future die throat development, some concluding remarks and recommendations are made based on the analysis of the experimental results obtained in this study.     

单辊筒口型挤出机

介绍了单辊筒口挤出机在国外的开发进展情况及国内的研制成果。论述了其工作原理、结构和性能,并与压延法和常规挤出法进行了对比。单辊筒口型挤出机通过变更挤出机螺杆和辊筒转速灵活的预型口型和终端口设计组合可以有效控制挤出物的形状、尺寸和生产率。     

Die swell from capillary die and slit die: A theoretical study

Assuming polymer fluids obey the CEF equation, equations concerning die swell from capillary die and slit die were derived. The die swell of polymer increased with increasing shear rate and recoverable shear. Our theoretical predictions conformed well with the experimental data of die swell for PP and PS.     

Über die Herstellung von Cellulasen und die enzymatische Spaltung von Cellulose

Production of cellulases and enzymatic cleavage of cellulose . Recent work on production of cellulolytic enzymes and on enzymatic degradation of cellulose is described. For optimum enzyme production by Trichoderma reesei under carefully balanced growth conditions, cellulose levels as high as 2% may be employed. Nitrogen deficit may be economically avoided by adding organic nitrogen in the form of distiller's spent grain and dried ground T. reesei cell mass. Semicontinuous production has been shown to offer further special advantages. Cellulase activity may be directly monitored automatically in a computer-controlled pilot fermentation system. Xylitol and furfural process wastes have been shown to be suitable substrates for cellulase, requiring little or no costly pretreatment. The rate of cellulose hydrolysis is considerably increased by combined use of T. reesei and cellobiase active microorganisms such as Aspergillus phoenicia.     

精密多工位级进模嵌件板的设计及模具材料选用

介绍了多工位模具的工序安排，设计要点及模具材料的选用。     

单辊简机头挤出型胶生产线

介绍单辊筒机头挤出型胶生产线.选用单辊简挤出机,配用国产温控、供胶和余胶返回装置.辅助部分由接取测宽、上坡、冷却、下坡、定长裁断、快速输送、海绵吸水、吹干和抬取装置组成.单辊筒机头挤出机有零压力挤出的优点,可大大提高型胶断面尺寸稳定性.