Rheological properties of poly(vinyl chloride)/plasticizer systems—relation between sol–gel transition and elongational viscosity |
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Authors: | Masataka Sugimoto Hirokazu Hida Takashi Taniguchi Kiyohito Koyama Yuji Aoki |
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Institution: | (1) Department of Polymer Science and Engineering, Yamagata University, 4-3-16, Jonan, Yonezawa Yamagata, 992-8510, Japan;(2) Polymer Solution Center, Mitsubishi Chemical Corporation, 1, Toho-cho, Yokkaichi Mie, 510-8530, Japan;(3) Present address: R&D Computer Co., 1-5-3, Oohashi, Meguro, Tokyo, Japan |
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Abstract: | Poly(vinyl chloride) (PVC)/di-isononyl phthalate systems with PVC content of 45.5 (PVC8) and 70.4 wt% (PVC6) were prepared
by a hot roller at 150 °C and press molded at 180 °C. The dynamic viscoelasticity and elongational viscosity of PVC8 and PVC6
were measured in the temperature range from 150 to 220 °C. We have found that the storage and loss shear moduli, G′ and G″, of PVC8 and PVC6 exhibited the power-law dependence on the angular frequency ω at 190 and 210 °C, respectively. Correspondingly, the tan δ values did not depend on ω. These temperatures indicate the critical gel temperature T
gel of each system. The critical relaxation exponent n obtained from these data was 0.75 irrespective of PVC content, which was in agreement with the n values reported previously for the low PVC concentration samples. These results suggest that the PVC gels of different plasticizer
content have a similar fractal structure. Below T
gel, the gradual melting of the PVC crystallites takes place with elevating temperature, and above T
gel, a densely connected network throughout the whole system disappears. Correspondingly, the elongational viscosity behavior
of PVC8 and PVC6 exhibited strong strain hardening below T
gel, although it did not show any strain hardening above T
gel. These changes in rheological behavior are attributed to the gradual melting of the PVC crystallites worked as the cross-linking
domains in this physical gel, thereby inapplicability of the of time–temperature superposition for PVC/plasticizer systems. |
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Keywords: | Plasticizer Poly(vinyl chloride) Gel point Elongational viscosity |
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