A round robin test was performed to determine the reliability of values for the glass transition temperatureTg as determined by DTA on polymers. Ten different instruments were involved. The test material was high molecular weight polystyrene. Values forTg (midpoint) were reported in the range 107°C±2 K. The respective heat flow curves differed considerably in shape. In the literature aTg of 100°C is often given for polystyrene. The discrepancy between this value and the value of 107°C found in the round robin test is due to three differences: the thermal history of the sample, the evaluation of the heat flow curves, and the effect of finite sample size.
The combustion kinetics of Göynük oil shale, polystyrene and several polystyrene-oil shale blends were investigated by thermogravimetric
analysis in the present study. Experiments were conducted at non-isothermal conditions with a heating rate of 5, 10 and 20
K min−1 in the 298–1173 K temperature interval under an air atmosphere. Differential thermogravimetric data were analyzed by two
different models. Effects of blending ratio of oil shale and polystyrene and heating rate on the combustion kinetics were
investigated. Kinetic parameters were determined and the results were discussed.
This work reports the thermal and structural changes promoted by Buriti (Mauritia flexuosa L.) oil incorporation into polystyrene (PS) and poly(methyl methacrylate) (PMMA) matrices. Buriti oil, which was used due
to its high β-carotene content has a good thermal stability and can provide some stability to PS and PMMA as it was shown by TG and TMA
data. DSC results showed that both PMMA and PS-based materials were plasticized by the oil and demonstrated that they are
immiscible materials. SEM images depict the materials’ morphology.
Serials of halloysite nanotubes/polystyrene (HNTs/PS) nanocomposites with different contents of organo-modified halloysite
nanotubes (organo-HNTs) were successfully prepared by the in situ bulk polymerization of styrene with the organo-HNTs as macromonomers.
The percentage of grafting (PG%) of more than 230% was achieved, calculated from the results of the thermogravimetric analysis
(TG). The TG results also showed that the thermal stabilities of the HNTs/PS nanocomposites prepared via the bulk polymerization
were better than the pure polystyrene. And the maximum thermal degradation temperature of the nanocomposites increased with
the increasing of the amount of the HNTs fillers added.
A computerized adiabatic calorimeter for heat capacity measurements in the temperature range 80–400 K has been constructed.
The sample cell of the calorimeter, which is about 50 cm3 in internal volume, is equipped with a platinum resistance thermometer and surrounded by an adiabatic shield and a guard
shield. Two sets of 6-junction chromel-copel thermocouples are mounted between the cell and the shields to indicate the temperature
differences between them. The adiabatic conditions of the cell are automatically controlled by two sets of temperature controller.
The reliability of the calorimeter was verified through heat capacity measurements on the standard reference material α-Al2O3. The results agreed well with those of the National Bureau of Standards (NBS): within 0.2% throughout the whole temperature
region. The heat capacities of high-purity graphite and polystyrene were precisely measured in the interval 260–370 K by using
the above-mentioned calorimeter. The results were tabulated and plotted and the thermal behavior of the two materials was
discussed in detail. Polynomial expressions for calculation of the heat capacities of the two substances are presented.
Thermal degradation of polystyrene and polyvinylchloride was studied by thermomanometric analysis. A design of experiments
was used to quantify the influence of 8 physico-chemical parameters on the responses of the analyser and on the different
types of degradation compounds.
heat capacity or the specific heat is for any crystalline, partially amorphous
or completely amorphous substance or material a significant thermodynamic
property. The glass transition may be regarded as the melting point of amorphous
substances and materials, a transition property of an outstanding technical
importance. A crucial point is the fact that the presence of a glass transition
is an unequivocal proof of an amorphous content of a material. Furthermore,
the change of the specific heat at the glass transition temperature enables
the quantitative determination of the amorphicity on a relative or absolute
level of any substance or material. The absolute determination of the amorphicity
affords a calibration with a reference corresponding to the material under
investigation. The crystallinity for this reference substance must be known
from the preparation and or by any independent analytical method.
literature data for the specific heat and the glass transition of polystyrene
were collected and evaluated. Data were found for the specific heat in literature
from 10 to 470 K. The data were unified for each of the reported temperature
in a mean value and the corresponding standard deviation was determined. An
excellent conformity was found in the glassy state of polystyrene with standard
deviations lower than 0.7%. The standard deviations above the glass transition
were considerably higher.
All these literature data were transferred
for each of the literature sets separately into linear specific heat functions
in the vicinity of the glass transition. One set of our measurements performed
with the DSC 204 and with polystyrene SRM 705a as sample material was additionally
integrated in the mean of these functions for the glassy state and the liquid
amorphous state respectively. The addition of our results gave practically
no change of the mean coefficients and only a decrease of the standard deviations.
In such a way, the data with the best statistical base for the specific heat
of polystyrene are listed in this paper ( ‘Conclusions’).
The glass transition as a transition in and out of a non-equilibrium
state, the glassy state, is sensitive to all kind of influences such as thermal
and mechanical treatments as well as to the selected experimental conditions.
Therefore, certain standardized conditions procedures must be fulfilled to
get reproducible data. The literature data for the glass transition temperature
were also used to get a mean value. However, two values were omitted for the
formation of the mean, because the authors reported values, which were too
low on the base of impurities present. The mean value of the glass transition
for polystyrene is according to the literature 3692 K. A mean value
of 3702 K was extrapolated for an infinite molecular mass.
The DSC and TMDSC measurements for the three thermodynamic properties
reported in this paper, namely the specific heat, the glass transition temperature
and the corresponding change of the specific heat gave results without significant
differences compared with the literature values.
is a rather ideal polymer together with sapphire as calibration substance
to elucidate and validate the DSC and TMDSC procedures for the determination
of the specific heat and the glass transition.
energy, and high thermal stability, PDMS is a desirable blend component [ 13 , 14 ]. One blend system containing PDMS that received much attention in literature is with polystyrene (PS), often in combination with PS-b-PDMS block copolymers as