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An improved method for increasing pseudoplasticity in vinyl plastisols
Author(s) -
Cohen Michael A.
Publication year - 1980
Publication title -
journal of vinyl technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.295
H-Index - 35
eISSN - 1548-0585
pISSN - 0193-7197
DOI - 10.1002/vnl.730020407
Subject(s) - shear thinning , plasticizer , materials science , composite material , dispersion (optics) , rheology , viscosity , fumed silica , dilatant , shear (geology) , physics , optics
It has been established that the addition of very fine particles in a vinyl plastisol will increase viscosity. These particles may range from 100 to 5,000 angstroms. High viscosity would also be the result of lowering plasticizer levels but with the consequence of increasing product hardness and plastisol dilatancy. Another effect of fine particle addition is an increase in pseudoplastic behavior. This pseudoplasticity is vital for knife coating open weave fabrics or other processes in which the plastisol must be thick enough so as not to run or strike through. But at high shear (under the knife), it must spread easily. A common fine substance currently used for these purposes is fumed silica (70–140Å). There have also been some specialty dispersion resins for add‐in pseudoplasticity. A new method utilizes the high efficiency and low cost of vinyl latex. Such small amounts are generally required that the water and surfactant content do not impair surface quality of the product. Preplasticized latex is particularly effective. As little as three parts (dry basis) per hundred dispersion resin increases Brookfield viscosity by 25 to 40 thousand centipoises. Pseudoplastic behavior is increased by over 100 percent. Its usefulness has been demonstrated at higher and lower plasticizer levels.