Applied Rheology and Interface Science |
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Industrial applied rheology relates fundamental properties to fitness-for-use of fluids of commerce. The success of a wide range of commercial products and industrial processes depends on meeting specific flow requirements. Architectural and industrial coatings, molded plastics, adhesives, personal care products and cosmetics, detergents, inks, cement, drilling muds, ceramic slips, solder pastes, foodstuffs and medicines are examples of rheologically complex fluids whose commercial viability depends on having the “right” rheology. For such materials, the necessary rheological properties must be defined with due regard to the prevailing conditions of stress and strain rate in processing and application. We have state-of-the-art instrumentation and nearly 30 years’ experience in characterizing the rheology and solving problems of complex fluids, including polymers, colloids, and solid dispersions of many kinds, which we want to place at your service. |
| We specialize in expert characterization of polymers, coatings, inks, adhesives, and a variety of other complex fluids. Our commitment is to provide not just data but guidance to problem solutions. |
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Besides our main instrument, the TA Instruments AR1000N stress rheometer, we have acquired a Thermo-Haake CaBER (Capillary
Breakup Extensional Rheometer) instrument. Extensional viscosity
is the resistance to flow in a “stretching” deformation. It is independent of shear viscosity for non-Newtonian fluids, and can be
hundreds of times larger. Extensional viscosity controls such
properties as paint roller spatter, industrial rollcoat “misting”, spray atomization, and roll ribbing and tracking. Previous commercial extensional instruments involved complex flows and difficult
operation, and were unsuitable for fluids in the viscosity range of
coatings, adhesives, foods, gels, and other concentrated disperse
systems. The CaBER achieves a true extensional deformation by
means of separating plates, measuring extensional viscosities
from 1 to 105 Pa.s, at temperatures from 0 to 100°C.
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BRIEF CASE HISTORIES: |
| 1. The following Figure is an example of calculation of the weight-average molecular weight of polycarbonate resin from complex viscosity data. A problem of premature fracture of an automotive part was solved for a customer by determining the molecular weight and tan d and comparing to the failure time of various specimens. |
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| 2. By innovative use of the principles of dispersion rheology, the viscosity was lowered and the tackiness reduced of a concentrated paste for a Fortune 50 company, all without reformulating. The resulting improvement in processability and reduction in waste allowed the company to realize multimillion-dollar savings annually. |
| 3. Formulation and experimental guidance, by means of extensional viscosity data, was provided to solve a rollcoat misting problem, enabling a major adhesive manufacturer to gain critical new business. |
| 4. The reason for the failure of a latex-based waterborne thickener was identified, for a Fortune 500 manufacturer of automotive paints. A science-based, predictive quality-control test for acceptance of production batches was also developed. |
| 5. A severe “ribbing” problem in a solvent borne rollcoat-applied sanitary coating was solved by demonstrating that the solution polymer was not the determining factor in the applied film rheology, but rather the stability of the pigment dispersion. Rheological data were used to optimize steric stabilization of the pigment system. |
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| 6. The unusually high instant wet-holding power of a competitive adhesive was explained and the holding power quantitatively predicted by measurement of the yield stress and the rigidity modulus in the linear viscoelastic regime. Guidance was provided to match the performance. |
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| 7. Brittle failure of an injection-molded part was explained as a high molecular weight component missing in the failed material. The low-frequency elastic modulus (G¢) value is extremely sensitive to a small high MW tail that may not be seen in viscosity data and which may be lost in the noise in most chromatography detectors but which has significant effects on processing and performance. |
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For further information, contact C. Michael Neag:
Voice: 440-826-5318
~ Fax: 440-826-5233
Strongsville Research Center (SRC)
16651 Sprague Road
Strongsville, Ohio 44136
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