Monsanto Processability Tester Research Articles

Rheological and mechanical properties of poly (ethylene acrylic acid) and low density polyethylene blends

AbstractRheological properties of poly (ethylene‐acrylic acid) (PEA) and low density poly ethylene (LDPE) blends having varied amounts of LDPE from 0 to 100% have been evaluated at different temperatures (115, 120, and 130°C) and shear rates (61.33–613.30 s−1) using a Monsanto processability tester. A reduction in the melt viscosity of the PEA/LDPE blends was noticed with increasing the shear rate. The observed positive deviation in the experimental melt viscosities of the blends is an indication of the synergy present in the blends during melt processing. The activation energy (Ea) of flow calculated using Arrhenius relation for PEA, LDPE, and their respective blends lies in the range 29.98–40.56 kJ mol−1. The experimental activation energy of flow of the blends was higher than that obtained from the additivity rule. Highest activation energy was noticed for the blends containing 60–80% by weight of LDPE in PEA/LDPE blends, which is an indication for the miscibility of the blends at these ratios. The physicomechanical properties such as density, tensile behavior, tear strength, and hardness (Shore A) of PEA, LDPE, and their blends have been evaluated as a function of varying amounts of LDPE. The obtained physicomechanical properties of the PEA/LDPE blends lie in between that of pure polymers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Rheological behavior of a microcellular, oil‐extended ethylene–propylene–diene rubber compound: Effects of the blowing agent curing agent, and conductive carbon black filler

AbstractThe rheological behavior of microcellular, oil‐extended ethylene–propylene–diene rubber (EPDM) compounds was studied in extrusions containing a blowing agent. The cell morphology development and rheological properties were studied for unfilled and conductive carbon black (Vulcan XC72, Cabot Corp., Ltd., Alpharetta, GA) filled compounds with variations of the blowing agent, extrusion temperature, and shear rate. The apparent shear stress, apparent viscosity, die swell (%), and total extrusion pressure of the Vulcan XC72 filled, oil‐extended EPDM compounds were determined with a Monsanto processability tester (St. Louis, MO). The effects of the curing agent and blowing agent on the rheological properties of the compounds were also studied. A significant reduction in the stress and viscosity with the blowing agent was observed in the compound in the presence of the curing agent in comparison with those without the curing agent. The viscosity reduction factor was found to be dependent on the blowing agent loading, shear rate, and temperature. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Effects of quasi‐nanogel particles on the rheological and mechanical properties of natural rubber: A new insight

AbstractThe influence of sulfur‐crosslinked, quasi‐nanosized gels on the rheological and mechanical properties of raw natural rubber (NR) was investigated. Latex gels with different crosslink densities were prepared through the variation of the sulfur‐to‐accelerator ratio. These gels were characterized by dynamic light scattering, solvent swelling, and mechanical properties. The gels were mixed with raw NR latex at concentrations of 2, 4, 8, and 16 phr, and their effect on the rheological properties of NR was studied by Monsanto processability tester. The presence of gel in raw NR reduced the apparent shear viscosity and die swell considerably. Initially, the viscosity decreased up to a 8 phr gel loading and then increased with an increase in the gel loading. However, the change in the viscosity was related to the crosslink density of the gels. A new empirical equation relating the viscosity, volume fraction of the gels, and crosslink density was proposed. The die swell of gel‐filled raw NR was at least 10% lower than that of unfilled raw NR and decreased with an increase in the gel loading. The effect of the gels on the die swell properties was explained through the calculation of the principal normal stress difference of gel‐filled NR systems. Scanning electron photomicrographs of the extrudates revealed much better surface smoothness for the gel‐filled virgin rubber systems than for the unfilled rubber. The addition of the gels to raw NR increased the modulus and tensile strength, whereas the elongation at break decreased. The effect of the gels on the dynamic mechanical properties of NR was also investigated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Rheological Behavior of Hybrid Rubber Nanocomposites

Abstract Melt rheological behavior of acrylic rubber (ACM)/ silica and epoxidized natural rubber (ENR)/ silica hybrid nanocomposites prepared by using sol-gel technique at room temperature was studied for the first time in a Monsanto Processability Tester (capillary rheometer) at nine different shear rates and three different temperatures (100 °C, 110 °C and 120 °C). Tetraethoxysilane (TEOS) was used as the precursor for silica, and water to TEOS mole ratio was maintained at 2:1 throughout the experiments. The loading of TEOS was 10, 30 and 50 wt% with respect to the rubber and the pH of the medium was maintained in the range of 1.0–2.0 by the addition of appropriate amount of concentrated HCl. The shear viscosity showed marginal increment even at higher nanosilica loading for the rubber/ silica nanocomposites. All the compositions displayed pseudoplastic behavior and obeyed Power Law model within the experimental conditions. The reinforcement factor (RF) calculated from the ratio of the viscosities of the filled and the unfilled systems was found to increase with nanosilica content at a particular shear rate. ENR/ silica nanocomposites displayed higher increment of RF compared to ACM/ silica system, which may be due to better polymer-filler interaction in the former. The RF remained almost constant for both the systems with the variation of temperature. The die swell of the nanocomposites was always lower than that of the gum rubber sample, though the nature of variation of die swell with shear rates was different for ACM and ENR nanocomposites. In both the cases, the die swell was found to decease with increase in temperature. The variation in activation energy with the experimental shear rates was also calculated, where the hybrids displayed a decreasing trend in activation energy with the increase in shear rate.

Studies on miscibility of blends of poly (ethylene acrylic acid) and ethylene‐co‐vinyl acetate by melt rheology

AbstractRheological behavior of blends of poly (ethylene‐acrylic acid) (EAA) and ethylene vinyl acetate (EVA) copolymer have been carried out at various temperatures, namely, 100, 110, and 120°C, and different shear rates from 61.33 to 613.30 s−1 using a Monsanto Processability Tester. The melt viscosity of the blends shows synergism during processing. The activation energy of the blends is in the range 20.7–44.6 kJ/mol. Highest activation energy was observed for the blends containing 40–60% of EVA by weight. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1947–1954, 2005

Rheological Behavior of Low-density Polyethylene (LDPE)- Polydimethylsiloxane Rubber (PDMS) Blends

The rheological behavior of different blends of low-density polyethylene (LDPE) and polydimethylsiloxane rubber (PDMS) has been investigated at different temperatures (160, 180, and 200 C) and shear rates (61.3-613.1 s 1) with varying proportions of ethylene methylacrylate copolymer (EMA) and silica filler loading by using a Monsanto Processability Tester (MPT). The EMA copolymer is used as a chemical compatibilizer for the blend systems. The melt viscosity increases with the increase in the PDMS proportion and the filler loading but decreases with the increasing proportion of the EMA. The melts of all the blends are pseudoplastic in nature. The flow behavior index (n)of the blends decreases with the increase in the PDMS proportion and the silica filler loading but increases with the increase in the EMA proportion and the temperature. The activation energy of flow for the blends decreases with an increase in the PDMS proportion and the silica filler loading. But it decreases initially with an increasing proportion of EMA, reaches a minimum value at 6 wt% and then increases. The die swell increases with an increase in the shear rate but decreases continuously with an increase in the PDMS proportion and the silica filler loading. But it becomes the maximum at 6 wt% of EMA for the compatibilized blends. The phase morphology studied by Scanning Electron Microscopy (SEM) shows an improved dispersion for a 50/50 blend of LDPE-PDMS and it further improves with the incorporation of 6 wt% of EMA as well as the blend containing 10 wt% of silica filler loading. The surface finish of the extrudate for the blend containing 10 wt% of silica filler is better compared to that with 20 wt% of silica filler.

Predication of critical distance of wall‐slip phenomenon during extrusion of carbon black‐filled natural rubber/cis‐polybutadiene rubber compound

AbstractThe wall‐slip phenomenon during extrusion of polymer fluids is an important characteristic of viscoelasticity. The wall‐slip behavior and the factors affecting it for natural rubber (NR)/cis‐polybutadiene rubber (BR) filled with carbon black compound were investigated by using a Monsanto processability tester in a temperature range of 90–130°C and at shear rates that varied from 50 to 103 s−1. Under simplified supposition conditions, a mathematical model for description of the relationship between pressure variation, polymeric properties, and extrusion operation parameters when wall‐slip phenomenon occurs was established by using a tensor analysis method. On the basis of this model, an equation for estimation of critical slip distance (or position) was derived. The results showed that the measured critical pressure drop, when wall‐slip begins to occur, was consistent with the theoretical predictions. The wall‐slip phenomenon of the sample happened near the exit of the die. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3239–3243, 2004

Pressure oscillation phenomenon during capillary extrusion flow of carbon-black-filled NR/BR compounds

The pressure oscillation phenomenon can be observed at the onset of the wall-slip phenomenon during extrusion of a polymer fluid, which is an important characteristic of the viscoelasticity of the fluid. In this work, the extrusion properties of two natural rubber (NR)/cis-polybutadiene rubber (BR) blends filled with carbon black are measured by using a Monsanto Processability Tester (MPT) in the temperature range 90–130 oC and shear rates varying from 50 to 10 3 s −1, to identify the effects of the die geometry, temperature and shear rate on the pressure losses. It was found that the total pressure drop during extrusion of the samples decreased with increase of the die diameter and rise of temperature, whereas it increased with increasing shear rate. Furthermore, some pressure fluctuation phenomena were observed under these test conditions. This suggests that wall-slip phenomenon occurs during capillary extrusion flow of the samples under the experimental conditions. The results showed that critical shear rates for onset of the pressure oscillation phenomena increased with increasing die diameter and with a rise of temperature.

Rheological properties of styrene–butadiene rubber filled with electron beam modified surface treated dual phase fillers

The rheological properties of styrene–butadiene rubber (SBR) loaded with dual phase filler were measured using Monsanto Processability Tester (MPT) at three different temperatures (100°C, 110°C and 130°C) and four different shear rates (61.3, 306.3, 613, and 1004.5 s −1). The effect of electron beam modification of dual phase filler in absence and presence of trimethylol propane triacrylate (TMPTA) or triethoxysilylpropyltetrasulphide (Si-69) on melt flow properties of SBR was also studied. The viscosity of all the systems decreases with shear rate indicating their pseudoplastic or shear thinning nature. The higher shear viscosity for the SBR loaded with the electron beam modified filler is explained in terms of variation in structure of the filler upon electron beam irradiation. Die swell of the modified filler loaded SBR is slightly higher than that of the unmodified filler loaded rubber, which is explained by calculating normal stress difference for the systems. Activation energy of the modified filler loaded SBR systems is also slightly higher than that of the control filler loaded SBR system.

Chemorheological study of compatibilized blends of low‐density polyethylene and polydimethyl siloxane rubber

AbstractCompatibilization of the blends of polydimethyl siloxane (PDMS) rubber and low‐density polyethylene (LDPE) was achieved through reactive processing during extrusion in a Monsanto Processability Tester (MPT). The chemorheological characteristics of 50 : 50 LDPE : PDMS blends with varying proportions (0–8 wt %) of ethylene comethyl acrylate (EMA) were investigated at three different temperatures (170, 190, and 210°C) and four different shear rates (61.3, 122.6, 306.6, and 613.1 s−1). It was found that EMA reacts with vinyl groups of PDMS rubber at a temperature of 190°C during extrusion through the capillary of MPT, forming EMA‐grafted‐PDMS rubber (EMA‐g‐PDMS), which acts as the compatibilizer for the blend systems. The results are based on IR spectroscopy, melt rheology, and phase morphology of the blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 12: 2810–2817, 2003

Recycling of ethylene propylene diene monomer (EPDM) waste. III. Processability of EPDM rubber compound containing ground EPDM vulcanizates

AbstractThe rheological behavior of ethylene propylene diene monomer (EPDM) compounds containing ground EPDM waste (W‐EPDM) of known composition was studied by using a Monsanto processability tester in a temperature range of 90–110°C and a shear rate range of 306.7–1533.24 s−1. It is found that the shear viscosity decreases slightly with increasing W‐EPDM loading because of wall slip that results from the migration of lubricants from the W‐EPDM. The addition of W‐EPDM to raw EPDM results in a decreased die swell at all temperatures and shear rates. SEM photomicrographs of the EPDM extrudate surface show improved surface smoothness and reduced extrudate distortion when EPDM is blended with W‐EPDM. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2204–2215, 2003

Studies on ground EPDM vulcanisate as filler in window seal formulation

The processability, curing characteristics, and mechanical properties of a window seal compound based on highly filled and oil extended EPDM rubber (R-EPDM) containing ground EPDM vulcanisate of known composition (W-EPDM) simulating the waste window seal product have been studied. A conventional mechanical grinder with a rotating abrasive wheel was used for grinding the aged vulcanisate. The Mooney viscosity of R-EPDM increased linearly with volume fraction of W-EPDM. Rheological behaviour, studied using a Monsanto processability tester in the shear rate range of 306 7 to 1533 s-1, showed that the surface smoothness of the R-EPDM extrudates was slightly impaired by the addition of W-EPDM, although the die swell remained almost constant. Mooney scorch time decreased with progressive addition of W-EPDM, presumably owing to the migration of accelerators from W-EPDM to R-EPDM. While the minimum rheometric torque ML increased, the maximum rheometric torque MH and Deltatorque (i.e. MH-ML) decreased with increasing loading of W-EPDM. The decrease in Δtorque may be due to the migration of sulphur from R-EPDM to W-EPDM. Although the tensile strength and elongation at break remained almost constant, the modulus, hardness, abrasion resistance, and tear strength of the vulcanisates progressively decreased with W-EPDM loading. While hysteresis loss of the vulcanisates decreased, resilience increased slightly and the tension set remained constant as the W-EPDM loading increased. The deterioration in some physical properties on incorporation of the ground vulcanisate up to a loading of 200 phr is marginal compared with previously reported results on utilisation of ground waste rubbers such as cryoground rubber tyres in virgin rubbers.

Rheological Behavior of Ethylene-Octene Copolymer Vulcanizates: Effect of Blowing Agent and Precipitated Aluminium Silicate Filler

An experimental study of the rheological behaviour of aluminium silicate filled ethylene-octene copolymer vulcanizates in extrusion containing blowing agent has been carried out. The cell morphology development has been studied through scanning electron microscope. Rheological properties of unfilled and aluminium silicate filled systems with variation of blowing agent, extrusion temperature and shear rate have been studied using Monsanto processability tester (MPT). The total extrusion pressure (ΔPT), apparent shear stress (x), apparent viscosity (ηa), and die swell (%) of the unfilled and aluminium silicate filled compounds have been determined by using MPT. It is found that there is a reduction in stress and viscosity with blowing agent loading. It is observed that incorporation of blowing agent led to decreased shear thinning behaviour resulting in an increase in power law index. The viscosity reduction factor (VRF) of unfilled vulcanizates is found to be dependent on concentration of blowing agent, shear rate and temperature, whereas VRF of aluminium silicate filled vulcanizates is found to be independent of shear rate and temperature but dependent on blowing agent concentration.

Influence of die angles on pressure drop during extrusion of rubber compound

AbstractThe factors affecting pressure losses during extrusion of polymer melts are discussed in the present article. The rheological properties of an unvulcanized rubber compound were examined by using a Monsanto processability tester (MPT) under experimental conditions of temperatures varied 90 to 120°C and shear rates from 102 to 103 s−1. Furthermore, a set of dies with different entry angle (2α) was selected to identify the effects of die angles on pressure losses in capillary extrusion of the sample fluid. It was found that the total pressure drop (ΔP) decreased when 2α < 75 degrees, and then increased with increasing 2α. The ΔP reached the minimum value when 2α is around 75°. It suggests that the natural converging angle of the sample fluid be about 75° under the experimental conditions, according to the research results presented in previous work. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1150–1154, 2001

The Rheology and Processability of Tire Compounds

Abstract The purpose of the work reported here was to define the parameters, which affect the rheology of tire compounds as well as their processability. Rheology was characterized over a wide range of shear rates. Processability was defined inversely as the roughness of the extrudate from the Monsanto Processability Tester (MPT) capillary rheometer. The roughness was measured by using image analysis of the extrudate surface contour. A good correlation was found between the extrudate roughness and the size of the Mooney peak (peak in apparent stress plotted against time for very small shear rates in a start-up flow experiment). The Mooney peak can be represented as a yield stress. The effects of storage time and temperature on the size of the Mooney peak (i.e., its increase as a function of storage time) was studied. The kinetics of degradation of processability was not found to follow an Arrhenius type of behavior. Finally, a physical descriptive model was proposed to represent filler—rubber structures.

Rheological behavior of highly filled ethylene propylene diene rubber compounds

The rheological behavior of highly filled ethylene propylene diene rubber (EPDM) compounds was studied with respect to the effect of curative system, grafted rubber, shear rate, temperature and die swell using a Monsanto Processability Tester (MPT) to gain an understanding of the molecular parameters that control the surface finish. All systems show pseudoplastic behavior. At a particular shear rate, shear viscosity increases with blend ratio. The dependence of flow behavior on extrusion velocity indicates a surface effect. The extrudate die swell and maximum recoverable deformation are related by a linear relationship, which is independent of sulfur/accelerator ratio, extrusion temperature and shear rates and blend ratio. The principal normal stress difference increases nonlinearly with shear stress. Activation energy decreases with shear rate in most cases. The faster relaxing system produces extrudate of better surface quality.

Ionomeric polyblends of zinc salts of maleated EPDM rubber and poly(ethylene-co-acrylic acid). II. Effect of zinc stearate on processability

Rheological properties of the ionomeric polyblends of zinc salts of maleated ethylene propylene diene monomer (EPDM) rubber and poly(ethylene-co-acrylic acid) were studied using a Monsanto Processability Tester. The ionomeric polyblend exhibits higher melt viscosity than the corresponding nonionomeric polyblend. Besides reduction in the melt viscosity of the ionomeric polyblend, zinc stearate increases the tensile strength and elongation at break of the ionomeric polyblend. Reprocessability studies reveal the thermoplastic elastomeric nature of the blend. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1257–1265, 1999

Melt rheology of segmented polyamides: Effect of block molecular weight

Segmented polyamides, also known as polyether-ester-amides, are composed of polyether and polyamide structural units. The rheological behavior of segmented polyamides with respect to the variations in the molecular weight of hard and soft blocks has been studied using a Monsanto Processability Tester. These systems exhibit pseudoplastic flow behavior. The shear viscosity of the segmented polyamides decreases with a decrease in hard block molecular weight up to 1500. However, at low shear rates, the shear viscosity shows marginal change with an increase in soft segment molecular weight. The equilibrium die swell increases with an increase in shear rate, but decreases with increasing temperature. The stress relaxation study of the segmented polyamides reveals that the stress developed during extrusion relaxes exponentially for all the systems. The equilibrium die swell at a fixed temperature and shear rate, the time required to relax a fixed amount of stress and the stress developed after a certain time interval decrease with a decrease in hard block molecular weight up to 1500, but increase with an increase in soft segment molecular weight. The activation energy of the melt flow process increases with the rate of shear in most of the cases. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1739–1747, 1999

Effect of surface oxidation of filler and silane coupling agent on the chemorheological behavior of epoxidized natural rubber filled with ISAF carbon black

On the basis of results of measurements of physical properties and solvent swelling of the extrudates, it has been observed that epoxidized natural rubber (ENR) interacts chemically with intermediate super abrasion furnace (ISAF) carbon black when the mix of the two was extruded at 130–160°C in a Monsanto Processability Tester (MPT). The extent of interaction between the rubber and filler depends on the following factors: extrusion time, carbon black loading, shear rate, and the extent of oxidation on the carbon black surface. Addition of the silane coupling agent, namely, N-3-(-N-vinyl benzyl amino) ethyl-γ-amino propyl trimethoxy silane monohydrochloride, enhances the rate of the interaction. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 557–563, 1999

Effect of silane coupling agent on the chemorheological behaviour of epoxidised natural rubber filled with precipitated silica

Results of measurements of physical properties and solvent swelling of the extrudates indicate that epoxidised natural rubber (ENR) interacts chemically with precipitated silica when the mix of the two was extruded at 150–170°C in a Monsanto Processability Tester (MPT). The extent of interaction between the rubber and the filler depends on the extrusion time, the volume fraction of the filler, the shear rate and the addition of the silane coupling agent, namely N-3-( N-vinyl benzyl amino) ethyl-γ-amino propyl trimethoxy silane monohydrochloride. The activation energy of the chemical interaction between ENR and silica decreases on the addition of the silane coupling agent.