Rheological Characteristics of Short Nylon-6 Fiber Reinforced Styrene Butadiene Rubber Containing Epoxy Resin as Bonding Agent

ABSTRACT

The rheological characteristics of short Nylon-6 fiber–reinforced Styrene Butadiene rubber (SBR) in the presence of epoxy resin–based bonding agent were studied with respect to the effect of shear rate, fiber concentration, and temperature on shear viscosity and die swell using a capillary rheometer. All the composites containing bonding agent showed a pseudoplastic nature, which decreased with increasing temperature. Shear viscosity was increased in the presence of fibers. The temperature sensitivity of the SBR matrices was reduced on introduction of fibers. The temperature sensitivity of the melts was found to be lower at higher shear rates. Die swell was reduced in the presence of fibers. Relative viscosity of the composites increased with shear rate. In the presence of epoxy resin bonding agent the temperature sensitivity of the mixes increased. Die swell was larger in the presence of bonding agent.     

Rheology of Short Nylon-6 Fiber Reinforced Styrene-Butadiene Rubber

ABSTRACT

The rheological characteristics of short Nylon-6 fiber reinforced styrene butadiene rubber (SBR) were studied using a capillary rheometer. The study was done with respect to the effect of shear rate, fiber concentration, and temperature on shear viscosity and die swell. All the melts showed pseudoplastic nature, which decreased with increasing temperature. Shear viscosity increased in the presence of fibers. Introduction of fiber reduces the temperature sensitivity of the rubber matrix. A reduction in die swell was found in presence of fibers.     

Viscosity and die swell of acrylonitrile-butadiene-styrene filled with glass beads and glass fibers

Shear viscosity and die swell ratio of acrylonitrile-butadiene-styrene filled with glass beads and glass fibers were measured. The relative viscosity of the composites increased with filler content, but decreased with shear rate. At low shear rates, fiber filled systems had higher relative viscosities than bead filled systems. At high shear rates, the opposite was observed. The die swell ratio of the unfilled material increased linearly with the logarithm of the shear rate. Systems highly filled with glass beads or fibers showed a maximum in the die swell ratio at medium shear rates. The magnitude of the maximum in the die swell ratio increased with the filler content and the die length, up to a certain length, in a series of dies that had the same radius. The presence of a maximum in the die swell ratio of the filled melts is explained by an order-disorder phenomenon observed earlier by Wu.     

Observation of melt fracture of polypropylene resins in capillary flow

Melt fracture, shear viscosity, extensional viscosity, and die swell of two polypropylene resins were studied using a capillary rheometer. A modified Bagley plot with consideration of pressure effects on melt viscosity and end effect was used. From the true wall shear stress the shear viscosity was calculated. Extensional viscosity was calculated from the end effect. Both shear and extensional viscosities of different molecular weights and temperatures correlated well under the time-temperature Williams-Landel-Ferry (WLF) superposition. Die swell increased when shear stress increased, and was higher for shorter dies at a given shear rate. When shear rates increased the extrudate staged from smooth to gross melt fracture with regular patterns (spurt), and then turned into irregular shapes. In the regular stage the wavelength of extrudates was measured, and corresponding frequency was calculated. The frequency increased when molecular weight decreased and when melt temperature increased. The shift factor based on shear viscosity also brought frequency data of different molecular weights and temperatures into master curves. The frequency decreased slightly when die lengths increased from L/R=10 to 60. A small maximum was observed when shear rates increased.     

Melt fracture,melt viscosities,and die swell of polypropylene resin in capillary flow

The melt fracture, shear viscosity, extensional viscosity, and die swell of a polypropylene resin were studied using a capillary rheometer and dies with a 0.05‐cm diameter and length/radius ratios of 10, 40, and 60. A temperature of 190°C and shear rates between 1 and 5000 s^?1 were used. A modified Bagley plot was used with consideration of pressure effects on both the melt viscosity and end effect. The shear viscosity was calculated from the true wall shear stress. When the true wall shear stress increased, the end effect increased and showed critical stresses at around 0.1 and 0.17 MPa. The extensional viscosity was calculated from the end effect and it showed a decreasing trend when the strain rate increased. Both the shear and extensional viscosities correlated well with another polypropylene reported previously. The die swell was higher for shorter dies and increased when shear stress increased. When the shear rates increased, the extrudate changed from smooth to gross melt fracture with regular patterns (spurt) and then turned into an irregular shape. In the regular stage the wavelength of the extrudates increased when the shear rate increased. The frequency of melt fracture was almost independent of the shear rate, but it decreased slightly when the die length increased. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1587–1594, 2003     

Rheological characterization of HDPE/sisal fiber composites

The present paper summarizes an experimental study on the molten viscoelastic behavior of HDPE/sisal composites under steady and dynamic mode. Variations of the melt viscosity and die swell of the composites with an increase in shear rate, fiber loading, and coupling agent concentration have been investigated using capillary rheometer. The shear rate γ at the wall was calculated using Rabinowitsch correction applied to the apparent shear rate values. It was observed that the melt viscosity of the composites increased with the addition of fibers and maleic anhydride-grafted PE (MAPE). Die swell of HDPE also decreased with the addition of sisal fibers and MAPE. Further, the dynamic viscoelastic behavior of the composites was measured employing parallel plate rheometer. Time–temperature superposition was applied to generate various viscoelastic master curves. Temperature sweeps were also carried out to study the flow activation energy determined from Arrhenius equation. The fiber–matrix morphology of the extrudates was also examined using scanning electron microscopy. POLYM. ENG. SCI., 47:1634–1642, 2007. © 2007 Society of Plastics Engineers     

Short fiber reinforced thermoplastics. I. Rheological properties of glass fiber reinforced Noryl

An experimental study on the flow behavior of glass fiber reinforced Noryl (a commercial poly(phenyleneoxide)/polystyrene blend) using a capillary rheometer is described. The effect of fiber concentration on shear viscosity and die swell was studied at various temperatures. Breakage of glass fibers during flow through the rheometer is discussed; it was found that the average fiber length (about 230 μm) was not significiantly altered, except at the highest shear rate (575 s⁻¹) studied. The incorporation of short fibers into thermoplastic polymer melts increases their viscosity without changing the basic rheological character-shear rate dependency. No discernible viscosity changes were measured by incorporating 10 weight percent fibers, and upon further increase of fiber concentration from 20 to 30 weight percent no appreciable increase in viscosity was noted. It is shown that short glass fibers cause a large reduction in extrudate swell. The presence of voids and fiber orientation contribute to the decrease of the die swell, an effect greater than expected from volumetric considerations alone.     

Rheology of short glass fiber-reinforced thermoplastics and its application to injection molding. II. The effect of material parameters

The effect of fiber concentration, fiber length, and temperature on the shear viscosity and die swell of several short glass fiber-filled thermoplastics has been determined. In addition, a study of the injection molding behavior of these materials has been performed. At low shear rates, viscosity increases appreciably with both fiber length and fiber concentration, but at high shear rates the effect is much less pronounced. A qualitative explanation is proposed for these effects in terms of the fiber orientation studies reported in Part I of this paper (1). The die swell is an important parameter in determining the method of mold filling of these materials, and depends strongly on fiber length.     

Rheological Behaviour of Short Silk Fiber Filled Rubber Compounds

Abstract

Rheological behaviour of rubbers (natural (NR), nitrile (NBR) and polychloroprene (CR)) and short silk fiber filled rubber compounds have been studied. The shear viscosity-shear rate relationship of both non-fiber filled and short fiber filled rubber compounds obey power law model for fluids and is similar to that of short fiber filled polymer melts. The effect of fiber concentration on the shear viscosity is more pronounced at lower shear rates. Both extrudate deformation and die swell become less on the addition of fibers to the mixes and the improvement is more significant at higher fiber concentrations. Extent of fiber breakage by the shear force during mixing is severe and is similar for all the rubbers.     

Shear viscosity,extensional viscosity,and die swell of polypropylene in capillary flow with pressure dependency

The shear and extensional viscosities of a polypropylene resin were studied using a capillary rheometer and capillary dies of 1‐mm diameter and length of 10, 20, and 30 mm. Melt temperatures at 190, 205, and 220°C and shear rates between 100 and 5000 s^?1 were used. At the highest shear rate a visible melt fracture was observed. An equation relating the pressure drop and die length was derived with consideration of pressure effects on melt viscosities and the end effect. After the correction for pressure effects the true wall shear stress and end effect at zero pressure were calculated. The end effect showed a critical stress of melt fracture around 10⁵ Pa, and increased rapidly when shear stress increased above the critical stress. From shear stress the shear viscosity was calculated, and a power law behavior was observed. Extensional viscosity was calculated from the end effect and showed a decreasing trend when strain rate increased. After time–temperature superposition shift shear viscosity data correlated well, but an upward trend was observed in extensional viscosity when melt fracture occurred. Die swell ratio at different temperatures can be plotted as a function of wall shear stress and was higher for shorter dies. © 2002 Wiley Perioodicals, Inc. J Appl Polym Sci 84: 1269–1276, 2002; DOI 10.1002/app.10466     

Rheological properties of poly(trimethylene terephthalate) in capillary flow

The shear viscosity, extensional viscosity, and die swell of the PTT melt were investigated using a capillary rheometer. The results showed that the PTT melt was a typical pseudoplastic fluid exhibiting shear thinning and extensional thinning phenomena in capillary flow. There existed no melt fracture phenomenon in the PTT melt through a capillary die even though the shear rate was 20,000 s^?1. Increasing the shear rate would decrease the flow activation energy and decline the sensitivity of the shear viscosity to the melt temperature. The molecular weight had a significant influence on the flow curve. The flow behavior of the PTT melt approached that of Newtonian fluid even though the weight‐molecular weight was below 43,000 s^?1 at 260°C. The extensional viscosity decreased with the increase of the extensional stress, which became more obvious with increasing the molecular weight. The sensitiveness of the extensional viscosity to the melt temperature decreased promptly along with increasing the extensional strain rate. The die swell ratio and end effect would increase along with increasing the shear rate and with decreasing the temperature, which represented that the increase of the shear rate and the decrease of temperature would increase the extruding elasticity of the PTT melt in the capillary die. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 705–709, 2005     

Rheological characterization of PP/jute composite melts

The present article summarizes an experimental study on the molten viscoelastic behavior of PP/jute composites under steady and dynamic mode. Variations in melt viscosity and die swell of the composites with an increase in shear rate, fiber loading, and coupling agent concentration have been investigated using capillary rheometer. It was observed that with the addition of fibers and MAPP, the melt viscosity of the composites increased due to improved fiber‐matrix interfacial adhesion. Further, the dynamic viscoelastic behavior, measured using parallel plate rheometer, revealed an increase in the storage modulus (G′), indicating higher stiffness in case of fiber‐filled composites as compared with the virgin matrix. Time–temperature superposition was applied to generate various viscoelastic master curves. The fiber‐matrix morphology of the extrudates was also examined using scanning electron microscopy, which corroborated the findings of rheological properties. The treated composites displayed uniform distribution of fibers within the PP matrix with lesser surface irregularities. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1476–1484, 2006     

Effect of filler treatments on rheological behavior of calcium carbonate and talc‐filled polypropylene hybrid composites

Commercial stearic acid treated calcium carbonate (CaCO₃) was used to make a comparative study on rheological behavior of the CaCO₃ and talc‐filled polypropylene (PP) hybrid composites with nontreated filler. Apparent shear viscosity and extrudate swell were investigated with variation of filler ratio and temperature with 30% by weight total of filler was used in PP composite. The Shimadzu capillary rheometer was used to evaluate shear viscosity and shear rate of the composite. It was found that the shear viscosities decrease with increasing shear rate. The apparent shear viscosity of the composite containing the stearic acid treated is slightly lower than untreated filler. Shear thickening behavior at higher shear rate has also shown by 15/15 treated composites at higher temperature about 220°C and investigation by SEM has proved that filler being densely packed at that condition. Treated composites also exhibit lower swelling ratio value than untreated composite, and swelling ratio also decreases linearly with increasing temperature and the die length–diameter ratio. It is believed that dispersion of filler play an important role not only on shear viscosity but also on swelling ratio of PP composite. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5421–5426, 2006     

Effect of wood fibers on the rheological properties of i‐PP/wood fiber composites

The effects of wood fibers on the melt rheological behavior of isotactic poly(propylene) (i‐PP)/wood fiber (WF) composites have been studied at WF concentrations of 0–32.2 vol % at 493 K. Shear stress–shear rate variations obeyed a power law equation, and the composites exhibited shear thinning, which increased with filler content. At a low shear rate, the apparent melt viscosity increased, while melt elasticity, after an initial decrease, also increased with WF concentration. At a higher shear rate, after an initial decrease, the melt viscosity showed an increase, as did melt elasticity, with increase in filler content. A titanate coupling agent, LICA 38, used to modify the wood fiber surface, modified these rheological parameters by functioning as a plasticizer/lubricant. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 644–650, 2004     

Melt rheological behavior of intimately mixed short sisal–glass hybrid fiber‐reinforced low‐density polyethylene composites. I. Untreated fibers

The melt rheological behavior of intimately mixed short sisal–glass hybrid fiber‐reinforced low‐density polyethylene composites was studied with an Instron capillary rheometer. The variation of melt viscosity with shear rate and shear stress at different temperatures was studied. The effect of relative composition of component fibers on the overall rheological behavior also was examined. A temperature range of 130 to 150°C and shear rate of 16.4 to 5470 s^?1 were chosen for the analysis. The melt viscosity of the hybrid composite increased with increase in the volume fraction of glass fibers and reached a maximum for the composite containing glass fiber alone. Also, experimental viscosity values of hybrid composites were in good agreement with the theoretical values calculated using the additive rule of hybrid mixtures, except at low volume fractions of glass fibers. Master curves were plotted by superpositioning shear stress and temperature results. The breakage of fibers during the extrusion process, estimated by optical microscopy, was higher for glass fiber than sisal fiber. The surface morphology of the extrudates was analyzed by optical and scanning electron microscopy. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 432–442, 2003     

熔纺氨纶的流变性能

研究了聚氨酯(TPU)切片、氨纶无油丝和不同混合比例的TPU与交联剂的混合物的流变性能,发现4种样品在熔融状态下均为切力变稀流体,熔体的剪切黏度随剪切速率的增大而减小;交联剂加入越多,熔体剪切黏度越大,在同样剪切速率下其熔融温度越高;随着熔融温度提高,熔体的剪切黏度减小。目前纺丝生产的经验值是TPU切片的熔融温度约为210℃,熔体管路及纺丝箱的温度约在200℃左右。     

Rheological and extrusion characteristics of glass fiber-reinforced polycarbonate

An experimental investigation of the rheological properties of glass fiber-reinforced polycarbonate melts and the extrusion of such compounds through capillary and slit dies is presented. The viscosity–shear rate function seems independent of instrument for cone-plate and capillary investigations. The presence of fibers increases the level of the viscosity. Normal stresses at fixed shear stress are also increased by the presence of fibers. The extrudate swell is decreased by the presence of fibers and surface roughness is increased. Fiber orientation increases and surface roughness decreases with increasing extrusion rate.     

Basic study of extrusion of polyethylene and polystyrene foams

A fundamental study of bubble morphology development and apparent rheological properties in foam extrusion is reported. The influence of melt temperature, die length/diameter ratio, and blowing agent level on the morphology are considered. Measurements of the influence of blowing agent on viscosity, extrudate swell, and end-pressure losses are described. The viscosity is reduced, but extrudate swell is increased. End-pressure losses were found to become very large relative to the die wall shear stress at low extrusion rates. These results were interpreted in terms of bubble development. The filling of molds by foaming melts was observed and is described.     

Effects of plasticizer on shear modification of polystyrene

The elastic and viscous properties of polymer melts may be affected by the shear history of the polymer. The extrudate swell of a polymer melt is primarily a manifestation of the elasticity of the polymer melt. In this study, a single screw extruder was used to impose different shear histories on a polystyrene polymer which was processed with and without added plasticizer. The extrudate swell and apparent viscosity of these melts were measured with a capillary rheometer. These characteristics of unplasticized polystyrene are almost not affected by the various preshearing processes. However, the extrudate swell and viscosity of polystyrene containing plasticizer are affected by plasticizer level, shear history and thermal history. After most of the plasticizer in the presheared plasticized polystyrene was extracted, the extrudate swell was still lower than that of the parent sheared polystyrene with the same shear history and the same plasticizer content. These results were obtained without significant changes in molecular weight. Shear modification by conventional process equipment may become impractical if the shear field intensity or dwell time of the material in the apparatus is limited. In such cases, shear refinability by standard process equipment may be observed if the coupling density in the polymer is reduced by some additional means, such as blending with a plasticizer.     

MELT RHEOLOGICAL PROPERTIES OF TALC-FILLED ISOTACTIC POLYPROPYLENE COMPOSITES

The melt rheological properties of talc-filled isotactic polypropylene have been studied at talc concentrations of 0–33.3 vol% and at 493 K. The composites followed a power law model in the shear stress–shear rate dependence and were shear thinning. The apparent melt viscosity increased whereas the melt elasticity parameter “first normal stress difference” decreased as the talc concentration increased. Surface modification of the talc by a coupling agent LICA 38 modified the rheological properties through bonding and/or a plasticizing/lubricating effect.