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Screw Extruder (screw + extruder)
Kinds of Screw Extruder Selected AbstractsMapping approach for 3D laminar mixing simulations: application to industrial flowsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 3-4 2002O. S. Galaktionov Abstract The computationally efficient mapping technique is applied to model laminar mixing in the transport section of the co-rotating twin screw extruder. The technique uses coarse grain values to describe the mixture and exploits temporal and spatial periodicity of the flow. The mapping approach yields adequate description of the concentration fields and residence time distributions. Copyright © 2002 John Wiley & Sons, Ltd. [source] Mixing immiscible blends in an intermeshing counter-rotating twin screw extruderADVANCES IN POLYMER TECHNOLOGY, Issue 2 2006Ramesh Potluri Abstract Domain size of 10% dispersed polystyrene in polyethylene was followed in a 34-mm intermeshing counter-rotating twin screw extruder. Variables studied included the effects of barrel temperature, screw speed, viscosity ratio of dispersed-to-continuous phase, and parallel melt versus preblended solids feeds. After steady state was achieved, die samples were quenched for later photomicrographing. The extruder was then stopped and quenched, with subsequent pulling of the screws. From 7 to 12 additional samples were taken along the 18/1 L/D extruder for determination of the mechanism of dispersion and dispersed phase domain size by optical microscopy. At low temperatures, the polystyrene tended to fracture with sharp edges. The fine particles formed in the initial breakup underwent no further size reduction. At higher temperatures, fractured segments had rounder edges, but the size of the small domains remained constant throughout the axial length. There was some evidence of flocculation and coalescence prior to exit through the die. © 2006 Wiley Periodicals, Inc. Adv Polym Techn 25: 81,89, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20065 [source] In-line analysis of the influence of monomeric and oligomeric hindered amine on the hydrolysis of polycarbonate in a PC/ABS blendJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Vipin V. Rajan Abstract The polycarbonate/polyacrylonitrile butadiene styrene (PC/ABS) blends lose mechanical properties when exposed to outdoor conditions. This is due to the ultraviolet (UV) induced photo-oxidation of the PC phase and the polybutadiene portion of the ABS. It is known that ABS can be stabilised against terrestrial light by the use of hindered amine in combination with a UV absorber. However, such hindered amine cannot be used when PC is present in a multi component polymer blend. The hydrolysis of PC is accelerated when a small amount of hindered amine light stabilisers (HALS) is incorporated in the resin and is exposed to elevated temperature. In this article the effect of monomeric and oligomeric hindered amine on the hydrolysis of PC during the compounding of PC/ABS blend in a twin screw extruder at 240°C is observed by means of in-line UV-vis spectroscopy. Tinuvin 765 was used as monomeric hindered amine and Tinuvin 622 as oligomeric hindered amine. The molecular weight of the compounded sample was determined by gel permeation chromatography (GPC) and the rheological properties were observed using an online viscometer. It was found that the extent of hydrolysis induced by the oligomeric hindered amine is less compared to monomeric amine. It was also observed that polymeric hindered amine imparts better dispersion of the ABS phase into the polymer blend. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Carboxylated multiwall carbon nanotube-reinforced thermotropic liquid crystalline polymer nanocompositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008Sang Ki Park Abstract Thermotropic liquid crystalline polymer (TLCP) nanocomposites reinforced with carboxylated multiwall carbon nanotube (c-MWCNT) were prepared through melt compounding in a twin screw extruder. The thermal stability of TLCP/c-MWCNT nanocomposites increased with even a small amount of c-MWCNT added. The rheological properties of the TLCP/c-MWCNT nanocomposites were depended on the c-MWCNT contents. The contents of c-MWCNT have a slight effect on the complex viscosity of TLCP/c-MWCNT nanocomposites due to the high-shear thinning of TLCP. The storage modulus of TLCP/c-MWCNT nanocomposites was increased with increasing c-MWCNT content. This result can be deduced that the nanotube,nanotube interactions were more dominant, and some interconnected or network-like structures were formed in the TLCP/c-MWCNT nanocomposites. Incorporation of very small amount of c-MWCNT improved the mechanical properties of TLCP/c-MWCNT nanocomposites, and this was attributed to the reinforcement effect of c-MWCNT with high aspect ratio and their uniform dispersion through acid treatment in the TLCP matrix. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Blending PP with PA6 industrial wastes: Effect of the composition and the compatibilizationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Mohamed Jaziri Abstract Blending polypropylene to recycled PA6 industrial wastes at different compositions, with and without compatibilizer PPgMA was produced in a corotating twin screw extruder where, polypropylene acts as the polymer matrix and polyamide as the dispersed phase. Several techniques were used to investigate the morphology, thermal, viscoelastic and tensile properties of these blend. Binary PP/PA6 blends showed the presence of PA6 particles dispersed in the PP continuous phase and exhibited a coarse morphology. Increasing PA6 contents in the blend increased their crystallinity and their size and improved the tensile properties at weak deformation. In addition to compatibilizer PPgMA, the morphology shows lower diameters and a decrease in size of the dispersed PA6 particles. The interfacial adhesion was also improved, as a result of the creation of an interphase that was formed by the interaction between the formed PPgPA6 copolymer in situ and both phases. This interphase induced an improvement in tensile properties. The PPgPA6 copolymer generated by the interphase was identified with DMA analysis thanks to an additional transition in loss modulus curves. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Reactive extrusion to synthesize intumescent flame retardant with a solid acid as catalyst and the flame retardancy of the products in polypropyleneJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008Yuan Liu Abstract Reactive extrusion and solid acid catalysis technologies were adopted in the pentaerythritol,melamine phosphate (PER-MP) reaction to synthesize intumescent flame retardant, melamine salt of pentaerythritol phosphate (MPP), which was applied in flame retardant polypropylene (PP). This environment-friendly synthesis method provided a solution to the problems of conventional methods. On one hand, reactive extrusion in a twin screw extruder can effectively mix and transfer viscous materials that usually results in a tough stir in a conventional reactor, and achieve a continuous synthesis process. On the other hand, the solid acid, silicotungstic acid (STA) serving as a catalyst, can maintain a satisfactory conversion even with a low extrusion temperature and a short residence time, thus effectively suppressing foaming in the process of the reaction. Furthermore, without removal like other catalysts in general chemical reactions, STA was kept in produced MPP to constitute a synergism flame retardant system, therefore further improved the flame retardancy. LOI and UL94 test showed that the STA-catalyzed MPP (by reactive extrusion) possessed much better flame retardancy in PP when compared with the noncatalyzed MPP (by reactive extrusion), as well as present commercial MPP (by POCl3 method). In our investigation, the catalytic and synergistic effects of STA, as well as the related factors of the reactive extrusion affecting the conversion of the PER-MP reaction, flame retardancy and mechanical performance of the corresponding flame retardant PP, were systematically investigated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Mechanical, flow, and morphological properties of talc- and kaolin-filled polypropylene hybrid compositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007M. B. Abu Bakar Abstract Polypropylene (PP) hybrid composites have been produced by compounding two types of mineral fillers, viz., talc and kaolin with PP copolymer using a twin screw extruder. The PP hybrid composite was injection-molded into dumbbell specimen for tensile, flexural, and impact properties characterizations. MFI and SEM studies were used to characterize the flow and morphological properties of the PP hybrid composites. The result shows that most of the hybrid composites showed a significant decrease in flow, tensile, flexural, and impact properties compared with the single filler-filled PP composites. However, a hybridization effect was seen for the PPT20K10 hybrid composites, through the synergistic coalescence of positive characteristics from 20 wt % of talc and 10 wt % of kaolin. This hybrid formulation have given an economically advantageous material with the mechanical properties (tensile, flexural, and impact) comparable to those of the talc-filled PP composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 434,441, 2007 [source] Mechanical and thermal properties of polypropylene/sugarcane Bagasse compositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007B. Ramaraj Abstract To determine the possibility of using sugarcane bagasse (SCB) waste as reinforcing filler in the thermoplastic polymer matrix, SCB-reinforced polypropylene (PP) composites were prepared. The PP and SCB composites were prepared by the extrusion of PP resin with 5, 10, 15, and 20 wt % of SCB filler in a corotating twin screw extruder. The extruded strands were cut into pellets and injection molded to make test specimens. These specimens were tested for physicomechanical properties such as tensile, flexural, Izod, and Charpy impact strengths, density, water absorption, and thermal characteristics, namely, heat deflection temperature (HDT), melt flow index, and thermogravimetric analysis. It was found that the flexural strength increased from 23.66 to 26.84 MPa, Izod impact strength increased from 10.499 to 13.23 Kg cm/cm, Charpy impact strength increased from 10.096 to 13.98 Kg cm/cm, and HDT increased from 45.5 to 66.5°C, with increase in filler loading from 5 to 20% in the PP matrix. However, the tensile strength and elongation decreased from 32.22 to 27.21 MPa and 164.4 to 11.20% respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3827,3832, 2007 [source] EFFECT of EXTRUSION ON TRYPSIN INHIBITOR CONTENTS of SOY-SWEET POTATO MIXTURESJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 6 2000M.O. IWE Mixtures of soy and sweet potato (Ipomoea batatas) (L.) Lam), flours containing 18%, 25% and 30% moisture, respectively, were extruded in a single screw extruder. Results showed that inactivation of trypsin inhibitor was enhanced by both reductions in feed moisture and soy flour contents of sample mixtures. Hence subsequent extrusion was carried at 18% feed moisture with variable feed ratio, screw rotation speed and die diameter, using a central composite rotatable, near orthogonal experimental design. Results further showed that the effect of increasing the ratio of soy in the mixture was linearly significant (p > 0.05). Optimum Trypsin Inhibitor (TI) inactivation value of 3.40 mg/g was predicted at a feed composition of 80% sweet potato, 9 mm die diameter and 154 rpm, respectively. [source] Hydraulic Alumina Binder for Extrusion of Alumina CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2007Takaaki Nagaoka The present work describes the effect of hydraulic alumina (HA) as a new inorganic binder on extrusion of alumina ceramics. The addition of a small amount of HA imparted significant flowability and rigidity to the extruded alumina. Under optimum processing conditions such as amounts of HA and water, and curing period, alumina rods and tubes were successfully extruded using a single screw extruder. Sintered specimens have achieved a relative density of 97% after sintering at 1600°C for 2 h. Dense alumina samples prepared using organic and inorganic binders had similar mechanical properties, that is, Young's modulus >380 GPa and Hv>2000. These results suggest that HA is a new kind of inorganic binder applicable to the extrusion of ceramics. [source] Simulations of grafting monomers and associated degradation of polypropylene in a modular co-rotating twin screw extruderJOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 4 2005Jongmin Keum Kinetic models of grafting maleic anhydride (MAH) and methyl methacrylate (MMA) on polypropylene (PP) were developed for screw extrusion. However, the kinetic models were insufficient to explain the grafting reactions along the length of modular co-rotating twin screw extruders because the rheological properties and the residence time of PP changed owing to degradation of PP during the grafting reaction. In order to model this system for a modular co-rotating twin screw extruder, the kinetic model of grafting reaction and models for degradation of PP were combined with fluid mechanics and heat transfer. Given the geometrical configurations of the screw, the operating conditions, and the physical properties of the polypropylene, the simulations predicted variation of molecular weight and mean residence time due to degradation of PP. The weight percent of grafted MAH or MMA on PP profiles along the screw axis was also calculated in the simulation. These predictions were compared with experimental data for various operating conditions. J. VINYL. ADDIT. TECHNOL. 11:143,149, 2005. © 2005 Society of Plastics Engineers. [source] In Situ Polymerisation of Polyamide-6 Nanocompounds from Caprolactam and Layered SilicatesMACROMOLECULAR MATERIALS & ENGINEERING, Issue 1 2009Bernd Rothe Abstract An in situ process for the production of polyamide-6 nanocompounds is investigated as an alternative to melt compounding. During the in situ production, the layered silicates are dispersed in the monomer caprolactam before the polymerisation in a twin screw extruder, leading to an intercalation of the silicates. The production of a polyamide compound containing 0, 2 and 4 wt.-% nanoscale silicates was successful. An improvement of the elastic modulus of approximately 30,60% was reached. The figure shows the TEM micrograph of a nanocompound containing 2 wt.-% nanoclay at a magnification of 30,000×. [source] Waste and Virgin LDPE/PET Blends Compatibilized with an Ethylene-Butyl Acrylate-Glycidyl Methacrylate (EBAGMA) Terpolymer, 1MACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2005Mustapha Kaci Abstract Summary: This work is aimed at studying the morphology and the mechanical properties of blends of low density polyethylene (LDPE) and poly(ethylene terephthalate) (PET) (10, 20, and 30 wt.-% of PET), obtained as both virgin polymers and urban plastic waste, and the effect of a terpolymer of ethylene-butyl acrylate-glycidyl methacrylate (EBAGMA) as a compatibilizer. LDPE and PET are blended in a single screw extruder twice; the first extrusion to homogenize the two components, and the second to improve the compatibilization degree when the EBAGMA terpolymer is applied. Scanning electron microscopy (SEM) analysis shows that the fractured surface of both the virgin polymer and the waste binary blends is characterized by a gross phase segregation morphology that leads to the formation of large PET aggregates (10,50 µm). Furthermore, a sharp decrease in the elongation at break and impact strength is observed, which denotes the brittleness of the binary blends. The addition of the EBAGMA terpolymer to the binary LDPE/PET blends reduces the size of the PET inclusions to 1,5 µm with a finer dispersion, as a result of an improvement of the interfacial adhesion strength between LDPE and PET. Consequently, increases of the tensile properties and impact strength are observed. SEM micrographs of the fracture surface of a waste 70/30 LDPE/PET blend (R30) and of its blend with 15 pph of EBAGMA (R30C). Magnification,×,1,000. [source] Morphology and mechanical properties of extruded ribbons of LDPE/PA6 blends compatibilized with an ethylene-acrylic acid copolymerMACROMOLECULAR SYMPOSIA, Issue 1 2003Francesco Paolo La Mantia Abstract Two grades of low density polyethylene (LDPE) were blended with polyamide-6 (PA) in the 75/25 and 25/75 wt/wt ratios and shaped into ribbons with a Brabender single screw extruder. An ethylene-acrylic acid copolymer (EAA) was used in the 2 phr concentration as a compatibilizer precursor (CP). The morphology of the ribbons and its evolution during high temperature annealing were investigated by scanning electron microscopy (SEM). The results confirmed that EAA does actually behave as a reactive compatibilizer for the LDPE/PA blends. In fact, in the presence of EAA, the interfacial adhesion is improved, the dispersion of the minor phase particles is enhanced and their tendency toward fibrillation is increased, especially for the blends with the higher molar mass LDPE grade. The mechanical properties of the latter blends were found to be considerably enhanced by the addition of EAA, whereas the improvement was relatively modest for the blends with the lower molar mass LDPE. The fracture properties of double end notched samples of the ribbons prepared with the blends containing the lower molar mass LDPE grade were also studied. It was shown that, despite of the increased interfacial adhesion caused by the presence of EAA, the latter plays a measurable positive effect on the fracture properties only for the blends with LDPE as the matrix. [source] Mechanical and thermal properties of polypropylene nanocomposites using organically modified Indian bentonitePOLYMER COMPOSITES, Issue 3 2010Hasmukh A. Patel We report preparation and characterization of nanoclay from Indian bentonite and imported nanoclays, and their compounding with polypropylene (PP) and maleic anhydride-grafted PP (MA-g-PP) in twin screw extruder. The compounded polymer/nanoclay nanocomposites (PNCs) are molded into a standard specimen for studying its tensile, flexural and impact strength. A wide angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM) study demonstrates intercalation of PP in nanoclays rather than exfoliation for both, indigenous and imported nanoclays. The tensile modulus increased by 41 and 39% for PNC1 (PNC with imported nanoclay) and PNC2 (PNC with indigenous nanoclay) with respect to PP. The flexural modulus for PNC1 and PNC2 also increases by 23 and 22% due to incorporation of 5% nanoclay in PP along with 5% MA-g-PP. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers [source] Preparation of poly(lactic acid)/poly(ethylene glycol)/organoclay nanocomposites by melt compoundingPOLYMER COMPOSITES, Issue 3 2006Shuichi Tanoue Poly(lactic acid) (PLA)/organoclay nanocomposites were prepared by melt compounding in a co-rotating twin screw extruder. Two types of commercialized organoclay (dimethyl benzyl stearyl ammonium ion and dimethyl distearyl ammonium ion intercalated between clay platelets named as Clay A and Clay B, respectively) and two grades of poly(ethylene glycol) (PEG) with different molecular weight (Mw = 2,000 and 300,000,500,000 named as PEG2k and PEG500k, respectively) were used in this study. The Young's modulus improved by the addition of organoclay to PLA matrix. The Young's modulus decreased with the addition of PEG to PLA/organoclay nanocomposites. The tensile strength and elongation of PLA/Clay B nanocomposites increased with the addition of PEG2k. The effect of the addition of PEG on d -spacing of PLA/organoclay nanocomposites is dependent upon the kind of organoclay. The sizes of clay agglomerations in PLA/PEG/organoclay nanocomposites are larger than those of PLA/organoclay ones in the same organoclay. Addition of PEG to PLA/organoclay nanocomposites during melt compounding will not be useful for the preparation of PLA/organoclay having fully exfoliated clay platelets. The shear thinning properties of the nanocomposites are independent of the addition of PEG. On the whole, PEG2k is good plasticizer for PLA/organoclay nanocomposites. POLYM. COMPOS. 27:256,263, 2006. © 2006 Society of Plastics Engineers [source] Effects of addition of functionalized SEBS on rheological, mechanical, and tribological properties of polyamide 6 nanocompositesPOLYMER ENGINEERING & SCIENCE, Issue 1 2010Yosuke Nishitani The effects of the addition of styrene-ethylene/butylene-styrene copolymer (SEBS) with various functionalized groups on the rheological, mechanical, and tribological properties on polyamide 6 nanocomposite filled with layered silicate (PA6/Clay) were investigated. Four types of SEBS: unmodified SEBS (SEBS), maleic anhydride grafted SEBS (SEBS- g -MA), amine group grafted SEBS (SEBS- g -NH2), and carboxyl group grafted SEBS (SEBS- g -COOH) were added with PA6/Clay nanocomposite to prepare various polymer blends. These polymer blends were extruded by a twin screw extruder and injection molded. Dynamic viscoelastic properties of these blends in the molten state and their tensile, impact, and tribological properties were evaluated. The viscoelastic properties were found to increase with the addition of SEBS and were highly influenced by the types of functionalized groups contained. Influence of the addition of SEBS on the mechanical properties of these systems differed for each mechanical property. Although the tensile properties decreased with SEBS, Izod impact properties improved with the addition of various functionalized SEBS. These mechanical properties and viscoelastic properties correlated closely with the size of dispersed SEBS particles and interparticle distance. The tribological properties also improved with the addition of SEBS, and the influence of the amount added was higher than the type of SEBS used. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers [source] Nylon 66/clay nanocomposite structure development in a twin screw extruder,POLYMER ENGINEERING & SCIENCE, Issue 4 2009Bin Lin Nylon 66/clay nanocomposites were prepared in a Berstorff ZE25A UTX Ultra-glide corotating twin screw extruder at 270°C. Two types of extruder configurations with different mixing sections were used. One comprised two kneading block sections in the screws (KB only) and the other had a combination of a multi-process-element (MPE) section and a kneading block section. Samples at eight different locations along the extruder screw were obtained and analyzed using scanning electron microscope and transmission electron microscope to examine the morphology development of clay inside nylon down the length of the extruder. It is found that the clay aggregates are quickly broken into smaller tactoids (micron size) and then even much smaller clay bundles (nanometer size) and single clay platelets in the first mixing section. The structure changes in the second mixing section are much less significant. X-ray diffraction (XRD) analysis of the nanocomposite products showed small, or disappearance of, characteristic XRD (001) peaks, which indicates partial exfoliation, or complete exfoliation, respectively, of clay inside nylon matrix. Differential scanning calorimetry nonisothermal study shows that the crystallization temperature of the nanocomposites has increased around 17°C when compared with neat nylon 66. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source] A comparative study of dispersing a polyamide 6 into a polypropylene melt in a Buss Kneader, continuous mixer, and modular intermeshing corotating and counter-rotating twin screw extrudersPOLYMER ENGINEERING & SCIENCE, Issue 4 2008Keungjin Shon We have made a study of the development of phase morphology of an immiscible blend(75/25)(polypropylene,polyamide-6) for different types of continuous mixers including (i) Buss Kneader, (ii and iii) modular intermeshing corotating and counter-rotating twin screw extruders, and (iv) NEX-T Kobelco Continuous Mixer. Comparisons are made using different screw configurations for each machine. Generally, in comparison of the different machines, the intermeshing counter-rotating twin screw extruder produced the finest dispersed morphology. Using a droplet breakup kinetic model, we interpreted the blend dispersed phase droplet breakdown rate and coalescence rate. In comparison with our earlier study of the continuous mixing of agglomerates of CaCO3 particles the polymer droplet breakup rate was smaller than that of the particle agglomerates and the coalescence rates of droplets were many times greater than the particle reagglomerates rates. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] Local residence time, residence revolution, and residence volume distributions in twin-screw extrudersPOLYMER ENGINEERING & SCIENCE, Issue 1 2008Xian-Ming Zhang This work was aimed at studying the overall, partial, and local residence time distributions (RTD); overall, partial and local residence revolution distributions (RRD) and overall, partial and local residence volume distributions (RVD) in a co-rotating twin screw extruder, on the one hand; and establishing the relationships among them, on the other hand. Emphasis was placed on the effects of the type and geometry of mixing elements (a gear block and various types of kneading elements differing in staggering angle) and process parameters on the RTD, RRD and RVD. The overall and partial RTD were directly measured in-line during the extrusion process and the local ones were calculated by deconvolution based on a statistical theory. The local RTD allowed comparing the mixing performance of mixing elements. Also it was confirmed both experimentally and theoretically that specific throughput, defined as a ratio of throughput (Q) over screw speed (N), controlled all the above three types of residence distributions, be they local, partial or overall. The RRD and RVD do not provide more information on an extrusion process than the corresponding RTD. Rather they are different ways of representing the same phenomena. POLYM. ENG. SCI., 48:19,28, 2008. © 2007 Society of Plastics Engineers [source] Influence of screw profile and extrusion conditions on the microstructure of polypropylene/organoclay nanocompositesPOLYMER ENGINEERING & SCIENCE, Issue 12 2007W. Lertwimolnun Direct melt mixing in a twin screw extruder is a simple and classical technique for preparing nanocomposites by dispersing organoclay in a thermoplastic matrix. In this paper, we focus on organoclay/polypropylene nanocomposites, using maleated polypropylene as compatibilizer. The objective of the work is to characterize the influence of screw profile and processing conditions on the microstructure of the nanocomposite (intercalation and exfoliation). Different screw profiles, more or less severe in terms of mixing elements, have been investigated. For each profile, different processing conditions (feed rate, screw speed) have been tested. Samples were collected both at die exit and all along the screw profiles and analyzed (X-ray diffraction and rheometry). Numerical simulations have been performed to quantify the thermomechanical treatment experienced by the material inside the extruder. For all profiles and operating conditions, a mixed intercalated/exfoliated structure has been observed. Exfoliation increases linearly with the ratio of screw speed to feed rate, but is more important for the less severe profile. Except at low feed rate, intercalation and exfoliation do not change a lot along the screw profile. In many cases, the final microstructure is already obtained after the melting zone of the extruder. POLYM. ENG. SCI., 47:2100,2109, 2007. © 2007 Society of Plastics Engineers [source] In-line near infrared monitoring of esterification of a molten ethylene,vinyl alcohol copolymer in a twin screw extruderPOLYMER ENGINEERING & SCIENCE, Issue 11 2006Claire Barrès Near infrared spectroscopy has developed in the polymer industry as a tool for in-line monitoring of processes, particularly extrusion. However, little work is dedicated to the monitoring of chemical reactions involving polymer melts. In this paper, we examine the suitability of NIR spectroscopy for monitoring the chemical modification (catalyzed esterification) of a molten ethylene,vinyl alcohol copolymer by octanoic acid in a twin screw extruder. Extrusion samples are characterized off-line, for calibration purposes, for the three species of interest (i.e. unreacted acid, OH groups, and ester functions formed on the polymer backbone) by means of two techniques: 1H NMR, allowing all three species to be quantified, and residual (free) acid titration. However, the mass balance of free acid is not straightforward, due to loss of mass by volatilization at the vent. Therefore, 1H NMR analysis and acid titration have to be combined to allow for determination of all concentrations. Multivariate calibration is implemented here to quantify and subsequently predict the analyte concentrations by using the NIR spectroscopic data. Our calibration, based on a partial least squares regression software, provides satisfactory results in terms of correlation between actual and predicted concentrations. This work demonstrates the potential of in-line NIR spectroscopy for monitoring chemical reactions with polymer melts in extrusion. POLYM. ENG. SCI. 46:1613,1624, 2006. © 2006 Society of Plastics Engineers [source] Amphiphilic block copolymers of PtBA- b -PMMA as compatibilizers for blends of PET and PMMAPOLYMER ENGINEERING & SCIENCE, Issue 9 2006B. Dewangan PET and PMMA were blended at various weight fractions. These blends were compatibilized by employing amphiphilic block copolymers of PtBA- b -PMMA, having three compositions (1:3, 1:1, 3:1) and three weight fractions (3, 5, and 7 wt%) using a co-rotating twin screw extruder. The blends were evaluated for their mechanical, rheological, and morphological properties. Overall, the compatiblized blends showed improvement in properties compared with the properties of noncompatiblized blends. Mechanical properties of the compatibilized blends improved with an increase in the PMMA and compatibilizer weight fractions. It was observed that the compatibilizer with lower molecular weight and lower glass transition temperature, typically at 5 wt%, provided the overall best properties. POLYM. ENG. SCI. 46:1147,1152, 2006. © 2006 Society of Plastics Engineers. [source] Anisotropy in the electrical behavior of immiscible polypropylene/nylon/carbon black blends processed slightly below the melting temperature of the nylonPOLYMER ENGINEERING & SCIENCE, Issue 9 2006J. Zoldan Carbon black (CB) containing polypropylene/nylon (PP/Ny) blends, processed slightly below the melting temperature (Tm) of the dispersed Ny phase, leads to formation of fibrillar Ny phase and electrically anisotropic systems. CB containing PP/Ny blends were compounded (twin screw extruder) and processed (injection molding) slightly below the Tm of dispersed Ny phase at different blending sequences. To establish structure,property relationships scanning electron microscopy, high resolution scanning electron microscopy, differential scanning calorimeter were used and electrical properties were also studied. Addition of CB to binary PP/Ny blends, processed below the Ny Tm, altered the Ny fibrillation process forming an irregular continuous phase, containing the CB particles, rather than the fibrils formed in the PP/Ny blends. Yet, upon changing the processing sequence, i.e., compounding PP and CB and then adding Ny in the injection molding stage, Ny fibrils were attained, maintaining phase continuity, oriented in the flow direction and CB particles preferentially located on their surfaces. Blends exhibiting a fibrillar Ny network covered by CB particles exhibited electrical anisotropy. The Ny fibrils exhibited an additional higher crystalline melting peak and molecular orientation. The composites are conductive in the Ny fibril direction, while insulating in the perpendicular direction. Once the CB is located within both, the Ny and the PP matrix the electrical behavior is isotropic. POLYM. ENG. SCI., 46:1250,1262, 2006. © 2006 Society of Plastics Engineers [source] Effect of rotational speed of twin screw extruder on the microstructure and rheological and mechanical properties of nanoclay-reinforced polypropylene nanocompositesPOLYMER ENGINEERING & SCIENCE, Issue 8 2006Piia Peltola The morphology and rheological and mechanical properties of nanoclay-reinforced polypropylene nanocomposites were investigated with aid of transmission electron microscopy (TEM), thermo gravimetric analysis, rheometry, and mechanical tests. The organically modified silicate (montmorillonite) was used as a reinforcing material and maleic anhydride-grafted polypropylene oligomer as a compatibilizer to improve the clay dispersion and adhesion. The object of the study was to examine the effect of screw speed of the co-rotating twin-screw extruder on the clay exfoliation and nanocomposite properties. Also, the effect of compatibilizing agent was taken into account. The main result of the study was that nanocomposites showed both intercalated and exfoliated structures depending on the screw speeds of extruder. TEM images revealed that the dispersion of silicate layers was greatly influenced by the screw speed. However, even when the silicate layers were highly exfoliated, there was no remarkable effect on mechanical properties of the nanocomposite. POLYM. ENG. SCI. 46:995,1000, 2006. © 2006 Society of Plastics Engineers. [source] Local mixing effects of screw elements during extrusionPOLYMER ENGINEERING & SCIENCE, Issue 3 2005R.M. van den Einde An in-line method was applied to determine local residence time distribution (RTD) at two places in a completely filled corotating twin screw extruder. Axial mixing effects of different types of elements were evaluated. Paddles +90° induced flow patterns that appear to be circular, both upstream and downstream, whereas paddles ,30° induced flow patterns that appear to be circular and mainly upstream. Transport and single-lead elements induced backflow. The results could be explained from pressure differences and direction of drag flow in the elements. All elements were characterized using an equivalent additional mixing length ,, dependent on the type of element and its position in the extruder, which may be practically useful for extrusion design. POLYM. ENG. SCI. 45:271,278, 2005. © 2005 Society of Plastics Engineers. [source] The effect of long chain branching on the processability of polypropylene in thermoformingPOLYMER ENGINEERING & SCIENCE, Issue 5 2004A. D. Gotsis Linear polypropylene was modified by reaction with peroxydicarbonates in a twin screw extruder to obtain varied degrees of long chain branching. The melt strength and the elasticity of the modified polymers were found to increase with the modification. The processability in foaming and thermoforming processes improved with branching and showed an optimum, beyond which higher degrees of long chain branching appeared not to help any further. The branched PP samples showed distinct strain hardening in the elongational viscosity, which was absent from the original linear melts. Melt strength, elasticity and strain hardening increased with the increase of the number of long chain branches on the main chain. The effect of molecular weight and molecular weight distribution of the precursor on the improvement of the processability of the polymer was examined. Polym. Eng. Sci. 44:973,982, 2004. © 2004 Society of Plastics Engineers. [source] Effects of process parameters on the micro molding processPOLYMER ENGINEERING & SCIENCE, Issue 9 2003J. Zhao The trend towards miniaturization has brought about strong demand for increasingly smaller precision-molded plastic components. In order to control metering accuracy and homogeneity of the very small quantities of melt in the micro molding process, new micro molding machines that use an injection system comprising a screw extruder and a plunger injection unit have been developed. By use of such injection systems, standard plastic granules can be handled by the screw extruder and melt accuracy can be achieved by the electrically driven injection plunger. The objective of this work is to investigate the effects of the process parameters on the micro molding process and part quality. A series of micro gears were molded using a polyoxymethylene resin in a set of statistically designed experiments. Micro component inspection, characterization, and data analysis work was carried out to study the molded gears. It was found that metering size and holding pressure time are the process parameters that have the most significant effects on part quality, and that the process is also significantly affected by the interaction of these two parameters. There is an optimum metering size range in which the hold pressure can act together with the metering size to properly fill micro mold cavities. [source] Maleic anhydride modification of polyolefin in an internal mixer and a twin-screw extruder: Experiment and kinetic modelPOLYMER ENGINEERING & SCIENCE, Issue 7 2001Jaehyug Cha There has been little effort. to quantitatively understand graft copolymerization in batch and continuous mixers. Little information exists on the evolution of grafting reactions with respect to residence time in an internal mixer or along the screw axis in a twin-screw extruder. In this study, maleic anhydride was grafted onto polypropylene in both an internal mixer and a twin screw extruder. The influence of residence time on degree of grafting in an internal mixer and a twin screw extruder was studied through measuring reaction yields with respect to reaction time in the internal mixer as well as along the screw axis in the extruder. The dependence of the degree of grafting with monomer and peroxide concentration was determined. A free radical kinetic model of the process was developed and compared to experiment. Kinetic parameters were determined. [source] 3-D non-isothermal flow field analysis and mixing performance evaluation of kneading blocks in a co-rotating twin srew extruderPOLYMER ENGINEERING & SCIENCE, Issue 5 2001Takeshi Ishikawa We have developed a three-dimensional non-Newtonian and non-isothermal flow analysis of the twin screw extruder (TSE) using the finite element method. This code can simulate the fully filled parts of several kinds of screw elements, such as full flight screws, kneading blocks, rotors and their combinations. A marker particle tracking analysis has also been developed to evaluate the mixing performance of the screw elements. In this paper, simulations for the kneading blocks in a co-rotating TSE were carried out. The screw configurations are combinations of 2-lobe kneading blocks with several stagger angles and disk widths. The effects of screw configurations on pressure and temperature distributions are examined. We also evaluate the dispersive and distributive mixing via stress magnitude and area stretch obtained by marker particle tracking analysis. Additionally, we discuss the desirable stagger, disk width and their combinations that promote the mixing performance. [source] | |||||||||||||