Effect of tetralin on the degradation of polymer in solution Page: 2 of 6
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EFFECT OF TETRALIN ON THE DEGRADATION OF POLYMER IN SOLUTION
Giridhar Madras, J M. Smith, and Benjamin J McCoy
Department of Chemical Engineering and Materials Science
University of California at Davis
Davis, CA 95616
Keywords polymer, hydrogen donor, thermal degradation, continuous kinetics, solvent effect
ABSTRACT
The effect of a hydrogen-donor solvent tetralin on thermal degradation of poly(styrene-allyl
alcohol) in liquid solution was investigated in a steady-state tubular flow reactor at 1000 psig at
various tetralin concentrations, polymer concentrations, and temperatures. The experimental data
were interpreted with continuous-mixture kinetics, and rate coefficients determined for the
specific and random degradation processes.
Introduction
Thermolytic degradation of polymers is similar in some respects to other important
thermal decomposition processes like petroleum cracking and coal thermolysis All these
processes involve complex mixtures, both as reactants and as products. Polymer degradation
usually occurs in a polydisperse mixture, and observing the temporal change of the molecular
weight distribution (MWD) caused by degradation atTords a means to test kinetic models Due to
the advance of technology in analytical instrumentation, dynamic MWD data can be obtained by
gel permeation chromatography (GPC). A continuous-mixture approach is applicable for these
cases, since it is based on mass balance equations that govern the temporal change of a
distribution function (Aris and Gavalas, 1966, Cheng and Redner, 1990). This approach has been
used for a theoretical discussion of polymer degradation (Ziff and McGrady, 1985,1986), for the
kinetics of reactions in reversible oligomerization (McCoy, 1993), as a model for coal liquefaction
(Prasad et al., 1986), and for coal thermolysis (Wang et al., 1994). Recently, Wang et al. (1995)
measured the rates of specific and random scission for the degradation of poly(styrene-allyl
alcohol) in t-butanol using the continuous-mixture approach.
There is little information of the effect of hydrogen-donor solvents on the degradation of
polymer in solution. Sato et al. (1990) investigated the solvent effect on the thermal degradation
of polystyrene at 300-450 C and 2 MPa. They observed that solvents with higher hydrogen
donating capability produced less conversion of polystyrene. These experiments indicated that the
degradation behavior, and the conversion of the polymer are affected by the solvents. Murakata et
al. (1993) investigated the effect of hydrogen-donor solvents on the degradation of poly-a.-
methylstyrene and observed that there was no effect of the solvent on the degradation mechanism
and the conversion of the polymer The effect of hydrogen-donor solvents has been extensively
investigated for coal liquefaction. The literature on this subject, including generally accepted
pathways for hydrogen transfer from a donor solvent, was summarized by Chawla et al (1989).
The objective of this study was to investigate the effect of the hydrogen-donor solvent,
temperature, and residence time on the degradation of the poly(styrene-allyl alcohol). The
experimental data was obtained by passing the polymer solution through a steady-state flow
reactor, and analyzing the products using HPLC-GPC. Continuous kinetics ideas were employed
to interpret the experimental data and fundamental data.
Experiments
The polymer used in this study was poly(styrene-allyl alcohol) (Polysciences, Inc.) of
number-average molecular weight 1100 The polymer was pretreated to remove components in
the lower molecular weight range, which would interfere with the analysis of the product peaks. A
detailed explanation of the pre-treatment is given by Wang et al. (1995). The polymer was pre-
treated by dissolving 50 grams of the polymer in 500 ml of t-butanol. The polymer solution was
continously stirred using a magnetic stirrer and heated to 40 C on a heating plate. A volume of
1350 mi of distilled water was added drop by drop to this polymer solution. The high molecular-
weight polymer precipitated and settled at the bottom. The dried precipitate was blanketed under
nitrogen in a closed bottle to avoid oxidation. The MW of the treated polymer was 1640
The experiments were carried out at high pressure, 1000 psig (6 8 MPa), to prevent the
aponzauion of the solvent, 1-butanol, at high temperatures and to ensure that the reaction of the
polymer occurs in the liquid phase. The polymer solution was prepared by dissolving the polymer
in I-butanol at a known concentration in the range of 1.4 g/L. The polymer solution flows
through the reactor, a water cooled heat exchanger, two pressure reduction valves placed in
sees, and finally exits through a rotameter The flow rate (and hence the residence time of the628
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Madras, G.; Smith, J. M. & McCoy, B. J. Effect of tetralin on the degradation of polymer in solution, report, December 31, 1995; United States. (https://digital.library.unt.edu/ark:/67531/metadc664875/m1/2/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.