Haake Rheometer Research Articles

Morphology and thermal stability of BR/clay composites prepared by a new method

AbstractA new potential preparation method named in situ organic modification was used to prepare intercalated polybutadiene rubber (BR)/clay/dimethyl dihydrogenated tallow ammonium chloride (DDAC) composites. That is, BR, pristine clay, and intercalatant DDAC were directly mixed in a Haake rheometer without pretreating the pristine clay with the intercalatant. The morphology of the BR/clay composites was investigated by means of X‐ray diffraction and scanning electron microscopy. The thermal stability of the BR/clay composites was analyzed by thermogravimetric analysis (TGA). The dispersion of clay particles in the BR/clay/DDAC composites is much better than that in the BR/pristine clay and similar to that in the BR/organoclay DK4 (modified with DDAC) composites. BR/clay/DDAC composites have much higher thermal stability than the gum BR, BR/pristine clay, and BR/DK4 composites. The clay/intercalatant ratio has little influence on the thermal stability of the BR/clay/DDAC composites, while clay content has a significant effect on their thermal stability. The enhanced thermal stability of the BR/clay/DDAC composites is related to the dispersion state of clay particles in BR. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 905–913, 2006

Efeito da massa molar e do teor de poliuretano nas propriedades mecânicas de misturas poli(metacrilato de metila)/poliuretano

Foi estudado o efeito da massa molar e do teor de três poliuretanos termoplásticos comerciais sobre as propriedades mecânicas de misturas físicas de poli(metacrilato de metila)/poliuretano. As amostras foram preparadas em reômetro Haake a 180 °C/10 min e 60 rpm, e as composições das misturas foram 0/100, 10/90, 30/70, 50/50, 70/30, 90/10 e 100/0 de PMMA/TPU. Propriedades mecânicas como resistência à tração e alongamento na ruptura foram melhores para a amostra PU (85 A15), de menor massa molar mássica média (Mw = 138,000). Os resultados mostraram que o teor de TPU afeta fortemente as características do material cujas propriedades tornam-se progressivamente semelhantes às do componente em maior proporção. O estudo permitiu comparar os resultados de misturas obtidas por processamento em reômetro com dados relatados para IPNs simultâneos e sequenciais de PU/PMMA. O perfil do comportamento do módulo de elasticidade sugere a ocorrência de duas fases contínuas nas misturas TPU/PMMA de acordo com dados previstos por equações teóricas propostas para IPNs

Effects of organic acids on sol?gel transition of silicic acid?Arheological study

The sol–gel transition in the silica system is dependent upon the degree of hydrolysis and polymerization reaction in the system [1]. The polymerization reaction for the formation of the gel network occurs in different stages, i.e. polymerization of monomer to form particles, growth of particles and finally linking of particles into chains and the formation of the network which extends throughout the liquid medium. The structural evolution through the growth of silicate polymers from the genesis to the gel point has been well established by various in-situ methods such as NMR, vibrational spectroscopy and small-angle scattering. However, a rheological study can be an important tool to characterize sols and sol–gel transition and can give a qualitative information on the structure at the time of gelation. Many processing parameters, such as the presence of a catalyst, H2O:Si ratio, type of solvent, pH, temperature, steric and inductive factors, etc. effect the mechanisms of hydrolysis and condensation of silicon alkoxide [1, 2]. For the hydrolysis and condensation rate of silicon alkoxide, the effect of a catalyst was investigated by Pope and Mackenzie [3], and the dependence of gel time on H2O:Si ratio was observed by Klein [4]. Artaki et al. [5] showed the effect of different solvents on the condensation rate of silicon alkoxide. Colby et al. [6] reported the effects of temperatures on the gelation of silicon alkoxide and the pH dependence on the hydrolysis and condensation of the same system is also well known [1, 2]. Voronkov et al. [7] pointed out that steric and inductive factors influenced the condensation rate of silicon alkoxides. In the present work, a rheological study, i.e. the determination of gelling time tg, the dynamic flow behaviour, the viscoelastic property of the sols and gels and its relation to relaxation exponent n and fractal dimension df in a three-dimensional space during hydrolysis and condensation of tetraethyl orthosilicate (TEOS), in the presence of different organic acids, i.e. oxalic acid, citric acid and succinic acid was carried out at the same pH, temperature and H2O:Si ratio in the system. Silicic acid sols were prepared by using (initially) alcohol-free TEOS (Fluka Chemica, Purum grade), deionized water and different organic acids, i.e. oxalic acid, citric acid and succinic acid (AR grade, S. D. Fine Chem. Pvt. Ltd.) in the molar ratio of 14:1:0.2 respectively at 32 ± 1 ◦C. The system was stirred magnetically and the temperature was increased to 70–80 ◦C. After stirring for about 15 min, a clear sol was obtained [8]. The pH of each sol was adjusted to 3.5 by addition of dilute NH3 (25 wt%, G. R. grade, E. Merck, India). The rheological measurements of the sols were carried out by using a Haake rheometer (Rotovisco, model: RT20) at 30 ◦C. The instrument was connected to a computer, loaded with Haake software (Version V3). A cone and plate sensor (c60/1◦) was used for all measurements. Steady shear flow measurements of the samples in controlled rate (CR) mode were carried out by increasing the shear rate from 0 to 200 s−1 over 30 s followed by an immediate decrease in the shear rate from 200 s−1 back to zero in another 30 s. The dynamic flow behavior, i.e. loss modulus (G ′′) and storage modulus (G ′) of the sols and gels was determined using oscillatory flow with varying radial frequency (ω) i.e., 0.924, 1.985, 4.279 and 19.855 rad s−1. Loss tangent (tan δ) can be obtained as,

Properties of Virgin Poly(Vinylchloride)/Acrylonitrile Butadiene Rubber (PVCv/NBR) and Waste Poly(Vinylchloride)/Acrylonitrile Butadiene Rubber (PVCw/NBR) Blends: The Effect of Blend Composition and Dynamic Vulcanization

The effect of blend composition and dynamic vulcanization on processability, mechanical properties, swelling behavior, and morphology of virgin poly(vinylchloride)/acrylonitrile butadiene rubber (PVCv/NBR) and waste poly(vinylchloride)/acrylonitrile butadiene rubber (PVCw/NBR) blends were investigated. Blends were prepared in a Haake Rheometer at 150°C and a rotor speed of 50 rpm. The Haake torque was used to investigate the mixing process. It was found that PVCw/NBR blends have lower mechanical properties and swelling resistance but higher stabilization torque and mechanical energy than PVCv/NBR blends. However, dynamically vulcanized PVCw/NBR blends exhibit mechanical properties that are superior to PVCv/NBR and unvulcanized PVCw/NBR blends. The introduction of a cross-link into the elastomer phase is responsible for the enhancement of the mechanical properties of dynamic vulcanized PVCw/NBR blends.

Graft copolymerization of oleic acid onto low‐density polyethylene in the molten state

AbstractA graft copolymer of oleic acid (OA) onto low‐density polyethylene (LDPE) was prepared using dicumyl peroxide (DCP) as an initiator in the molten state. The grafting was carried out in a Haake rheometer. The effects of the reaction time and the amount of DCP and the monomer on the percentage of grafting were studied. The rheological behavior and the melt‐flow rate of the graft copolymer (LDPE‐g‐OA) were also investigated. FTIR spectroscopy and a mass spectrum were used to characterize the structure of LDPE‐g‐OA. The experimental results showed that when the OA amount was 10 wt % and the DCP amount was 0.4 wt % based on the LDPE the percentage of grafting of LDPE‐g‐OA, prepared by maintaining the temperature at 170°C and the roller speed at 80 rpm, was about 6 wt %. It was found that both LDPE and LDPE‐g‐OA were pseudoplastic fluids. OA was grafted onto LDPE in the form of a monomer and a dimer. The grafted LDPE is expected to act as a compatibilizer between starch and polyethylene. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3299–3304, 2003

Study of rheological property of nylon‐1212 with Haake Rheometer

AbstractRheological properties of nylon‐1212 have been studied by means of Haake Rheometer. The effect of shear rate and temperature on the apparent vicosity of nylon‐1212 was discussed. A correlation of non‐Newtonian index with the temperature was obtained. The results showed that the apparent viscosity decreases with the increase of the temperature. With increasing shear rate, shear thinning of nylon‐1212 was observed clearly. From the relation of the temperature dependence of the polymer, we obtained the viscous flow activation energy. We conclude that the apparent viscosity is sensitive to temperature at lower shear stress because of higher viscous flow activation energy, and the temperature affect on the apparent viscosity becomes weaker at higher shear stress because of lower viscous flow activation energy. We have investigated the creep and elastic recovery of nylon‐1212. A creep test was carried out to define the linear viscoelastic range as 1.0 and 5.0 Pa for 195 and 190°C nylon‐1212 melts, respectively. A time‐dependent response was found for the creep and recovery phases at a lower applied shear stress. However, at higher shear stress, the creep and recovery phases were time‐independent. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 379–385, 2003

Influence of Fe2O3-filler on the thermal properties of polystyrene

Nowadays, filled polymers are widely used in many fields of technology. Among them, polymers containing semiconductor particles play significant roles, especially for the manufacturing of electronic devices [1]. Therefore it is important to understand the effects of these fillers on the properties of filled polymers in order to design materials with desired properties. The properties of filled polymers mostly depend on the type of materials used, of size and shape of filler particles, their concentration as well as the type of interaction between filler particles and polymer matrix. In our previous studies [2, 3] significant improvement of the thermal stability of the polystyrene (PS) matrix filled up with the hematite (Fe2O3) nanoparticles (the mean particle diameter was 5 nm) was found. This effect is consequence of high surface to bulk ratio of the Fe2O3 nanofiller. However, the synthesis route for preparation of nanocomposites is quite complex involving transfer of nanoparticles from water to organic phase. In the present study simple synthesis route for preparation of the PS-Fe2O3 filled polymer was developed based on mixing the Fe2O3-filler in sub-micrometer size range with the polymer melt. The influence of particle size of the Fe2O3-filler on the thermal properties of the PS-Fe2O3 filled polymer was discussed. Also, our goal was to examine influence of the content of inorganic phase on the thermal stability of the PS-Fe2O3 filled polymer. We synthesized the Fe2O3-filler particles by using the method of Matijevic et al. [4]. Briefly, 100 ml of 0.02 M FeCl3 was mixed with 1000 ml of 0.01 M HCl at elevated temperature (353 K). The solution was kept at elevated temperature for 24 h, and then precipitate was washed out several times with water, filtered and finally dried. In order to determine morphology and size of Fe2O3-filler particles scanning electron microscopy (SEM; Jeol JSM-3T) was used. The micrographs were taken at 0◦ tilt angle, thus making the topography contrast and shape of the particles irrelevant. Spherical Fe2O3 particles in the size range from 0.2 to 0.5 μm were observed, Fig. 1. This observation is in agreement with the results obtained by Matijevic et al. [4]. The PS-Fe2O3 filled polymers were prepared by mixing, in appropriate ratio, the Glaskar PS (PS 143 E) and the Fe2O3-filler in Haake rheometer at 473 K. The contents of inorganic phase were chosen to be 5, 10 and 17 wt%. Mixing was carried out at 32 rpm rotor speed

Poly(ethylene terephthalate)/polyethylene composite based on in-situ microfiber formation

Poly(ethylene terephthalate) (PET) microfiber was in-situ formed by compounding PET with polyethylene (PE) through a single screw extruder of a Haake rheometer system, where a rod die with comparatively smaller diameter (2.1 mm) was used, and the extrudate was drawn in a certain drawing ratio (3.1:1) and quickly cooled in cold water. Subsequently, the in-situ PET/PE composite was injection molded into specimens at temperatures that were lower than the melting temperature of the PET to keep the original shape of the PET fibers. The result from morphology observations of the composite showed that when the die diameter of the extruder is 2.1 mm and the drawing ratio of the extrudate is 3.1:1, PET was more or less changed into microfibers. The PET almost changed into fibers when the concentration was 15 wt%; concentrations below and above which decreased the fiber content. For the PET/PE blend prepared by conventional mixing technology, the dispersed PET formed spheres and no microfibrilar structure were found. The reinforcing effect of the PET fibers on the corresponding composite was significant at 15 wt% PET concentration observed from the correlation between the PET content and the tensile properties of the PET/PE in-situ composite. Besides, in general, the tensile strength and modulus of the composite increased with the PET concentration, and was higher than the conventional PET/PE blend without microfibers.

Mechanical properties and enzymic degradation of thermoplastic and granular sago starch filled poly(ε-caprolactone)

The mechanical, morphological and biodegradation properties of two types of poly(ε-caprolactone)/sago starch (PCL/sago) composites were investigated i.e. dried granulated sago starch and undried thermoplastic sago starch (TPSS). Thermoplastic starch was extruded with a twin screw extruder model Haake Rheomix (TW100 attached to a Haake Rheometer (Haake Rheodrive 5000). The composites were compounded with a Haake internal mixer (Haake Rheomix 3000) attached to the Haake Rheometer. Tensile properties were determined with the Monsanto Tensometer T10. A Shimadzu UV-160A visible UV spectrophotometer was used to monitor the liberation of carbohydrate as a consequence of starch hydrolysis by α-glucoamylase. Determining the weight loss of composites as well as the acid liberated from PCL also monitored biodegradation. The results indicate that dried granulated sago starch function better as fillers in terms of mechanical properties and the ease of biodegradation. However, TPSS imparted better yield strength to the composites. Poor wetting of starch accounts for the decreased mechanical properties at higher starch concentration as agglomeration occurs. While the rigid granular starch retained their shape in the composites, thermoplastic starch that is surrounded by microvoids is easily deformed due to plasticization.

An approach to the detection of synthetic milk in dairy milk: 4. Effect of the addition of synthetic milk on the flow behaviour of pure cow milk

The flow behaviour of cow milk, synthetic milk and their blends was evaluated with a Haake rheometer. Changes in flow behaviour are thought to be due to detergent, an important constituent of synthetic milk, which emulsifies the vegetable fat in the aqueous phase. The results are of value in detecting very low levels (1–10%) of synthetic milk in cow milk.

Synthesis and Characterization of Electrorheological Copolyaniline

Copolyaniline containing phenyl sulfonic acid sodium salt pendent, was chemically synthesized and used for its characterization as an electrorheological (ER) fluid. Its chemical structure and particle shape were analyzed using an FT-IR, 13C-NMR, and SEM. Copolyaniline particles have irregular and lamellar morphology. This ER fluid was prepared by dispersing polymer particles in silicone oil and was characterized by a rotational Haake rheometer with a high voltage generator. Typical ER behavior was found in the copolyaniline suspension.

Electrorheological characterization of polyaniline dispersions

Suspensions of polyaniline in silicone oil have been investigated as potential candidates for dry-base electrorheological (ER) fluid systems. Polyaniline was synthesized by a chemical oxidation of aniline in an acidic media. Its optimum conductivity (in the semiconductive range) for ER purposes was achieved by adjusting the pH of an aqueous solution containing polyaniline particles. ER experiments were conducted with a Haake rheometer for steady shear experiments to investigate the effects of imposed electric fields, the polymerization temperature (molecular weight), and the dispersing oil on ER performance. ER properties of polyaniline suspensions were found to be improved by increasing both the imposed electric field and the polymerization temperature of the used polymer. Suspensions using kerosene also show greater ER effect than that using silicone oil because of the smaller dielectric constant of kerosene than that of silicone oil. A scaling law is introduced to analyse the ER data.

Functionalisation of Polypropylene with Maleic Anhydride and Acrylic Acid for Compatibilising Blends of Polypropylene with Poly(ethylene terephthalate)

This paper reports an investigation of the functionalisation of polypropylene with polar monomers as an interfacial stabiliser for mixtures of poly-olefins with polyesters. Polypropylene was functionalised with maleic anhydride and acrylic acid in the presence of dicumyl peroxide. The reaction was carried out in the molten state using a preheated batch Haake Rheometer mixer under conditions which were expected from literature studies to be optimal. The effects of varying the concentrations of the monomers on the degree of functionalisation and properties of the products were investigated. An upper limit of only a few per cent of functionalisation was observed. Slow degradation was observed at melt processing temperatures. © of SCI.

Yield stress measurements with the vane

Yield stress measurements were performed on a TiO 2 pigment suspension with the vane in both a rate controlled and a stress controlled mode. In the rate controlled mode, a constant rotational speed is applied to the vane immersed in the suspension, and the resulting stress is measured as a function of time. In the stress controlled mode, a constant stress or a constant stress-rate is applied to the vane immersed in the suspension, and the resulting creep angle is measured as a function of time. In both modes the yield stress is determined as the minimum stress required for continuous rotation of the vane. A Haake Rheometer and a modified Weissenberg Rheogoniometer facilitated the controlled rate measurements. The significant difference between these instruments is that the Weissenberg torsion bar is 550 times stiffer than the Haake spring. To ensure a comparable time frame of measurement with the Haake, it was necessary to use lower rotational speeds in the operation of the Weissenberg. Although agreement in the measured yield stress within 5% was established between the Haake at a rotational speed of 0.021 rad s −1 and the Weissenberg at a rotational speed of 0.0063 rad s −1, the shapes of the respective stress-time profiles were strikingly different. The Haake exhibited a largely elastic response, whereas the Weissenberg exhibited a largely viscoelastic response. The yield stress measured by both the Haake and the Weissenberg corresponds to the transition stress between viscoelastic and fully viscous flow. A Bohlin Rheometer facilitated the stress controlled measurements. The yield stress measured by the Bohlin was up to 13% lower than that measured by the Haake and the Weissenberg, and seemed to correspond more closely to the transition stress between fully elastic and viscoelastic flow.

Investigation on the simulation of the reactive extrusion of nylon 6

AbstractIn this article, a novel simulation of the processing conditions of the anionic ring‐opening polymerization of nylon 6 in a counterrotating twin‐screw extruder by use of a modified Haake Rheometer run at elevated temperatures is described. Experimental results for several combinations of processing parameters are presented. General relations between processing parameters, conversion ratio, and molecular weight of the product are observed. These observations can be used in the eventual scaling up of investigation to an actual twinscrew extruder. © 1995 John Wiley & Sons, Inc.

Curing of unsaturated polyester resins—effects of pressure

AbstractThe effects of pressure ranging from 0.1 to 6.21 MPa (0–900 psig) on the curing of unsaturated polyester resins at 110°c were investigated by an approach of integrated reaction kinetics‐rheology‐morphology measurements using a pressure differential scanning calorimeter (DSC), an infrared spectrophotometer (IR), a Haake rheometer, and by using scanning electron microscopy (SEM). Increasing pressure was found to delay the gel effect, and a previously unknown plateau of kinetic‐controlled region in the initial portion of the DSC rate profile was observed. The plateau region was mainly attributed to the crosslinking of C  C double bonds inside the microgel particles, as revealed by the conversions of styrene and polyester C  C bonds measured by IR, gel conversion data and SEM micrographs. The mechanisms of reaction kinetics both at atmospheric pressure and under pressures have also been elucidated by the progress of buildup of microgel structures.

Microstructure and Flow Behaviior of Fresh Cement Paste

AbstractCharacteristics of aqueous cement suspensions and the packing nature during setting were investigated as keys controlling the microstructure and density of a cement paste. The theological properties of the paste were studied as functions of hydration and setting; these properties are influenced by a variety of external factors, which are discussed. The objective of this paper is to sketch a new atomistic approach to a group of rheological phenomena which are as interesting from a scientific viewpoint as they are important for technology. The experiments were carried out by a HAAKE rheometer and an acoustic ultrasonic system. At different flow state, the acoustic emission signal generated from micro-structure is transformed due to wave propagation and due to the transducer response. The scientific information obtained through this study is expected to contribute the establishment of concept of setting processing. The measurements of flow properties relating to flocculation and coagulation were evaluated with respect to the effects of processing conditions on structure development in cement paste.

Reaction injection molding of polyureas. II: Rheo‐kinetic changes and model simulation

AbstractAn experimental and theoretical study of reaction injection molding (RIM) of polyurea was conducted in this work. A lab‐scale RIM machine was used to carry out the polyurea bulk polymerizations. A “free‐table” viscometer was designed to measure the fast rheological changes and liquid‐solid transition. A mathematical model was proposed to simulate the fast reaction and rheological changes in the polyurea RIM process. The parameters of this model were determined based on the solution polymerization data from FTIR and Haake rheometer measurements. Combined with an appropriate heat transfer equation, this model predicts fairly well the adiabatic temperature and viscosity rises of bulk polyurea reactions in RIM.