The present report deals with some results on phase behavior, miscibility and phase separation for several polymer blends casting from solutions. These blends are grouped as the amorphous polymer blends, blends containing a crystalline polymer or two crystalline polymers. The blends of PMMA/PVAc were miscible and underwent phase separation at elevated temperature, exhibited LCST behavior. The benzoylated PPO has both UCST and LCST nature. For the systems composed of crystalline polymer poly(ethylene oxide) and amorphous polyurethane, of two crystalline polymers poly(-caprolactone) and poly[3,3,-bis-(chloromethyl) oxetane], appear a single Tg, indicating these blends are miscible. The interaction parameter B's were determined to be –14 J cm–3, –15 J cm–3 respectively. Phase separation of phenolphthalein poly(ether ether sulfone)/PEO blends were discussed in terms of thermal properties, such as their melting and crystallization behavior.
Authors:W. Ciesińska, J. Zieliński, and T. Brzozowska
Coal-tar pitch was modified by addition of polystyrene, poly(ethylene terephthalate), unsaturated polyester and coumarone-indene
resin. The optimum conditions for production of homogeneous binary pitch-polymer blends containing 10% w/w of the polymer were established. Softening points, contents of toluene and quinoline-insoluble matters and rheological properties
of the blends were determined. The yield of solid fraction in semi-coking the blends was also found. The effect of polymers
on the coal-tar pitch blend properties was evaluated. Some pitch-polymer blends were then carbonized to carbon sorbents used
for purification of water and wastewater.
The concept of crystallization dynamics method evaluating the miscibility of binary blend system including crystalline component
was proposed. Three characteristic rates, nucleation, crystal growth rates (N*, G*) and growth rate of conformation (Gc*) were used to evaluate the miscibility of PVDF/at-PMMA and PVDF/iso-PMMA by the simultaneous DSC-FTIR. N*, G* and Gc* depended remarkably on both temperature and blend fraction (ϕPMMA) for PVDF/at-PMMA system, which indicated the miscible system. PVDF/iso-PMMA showed small ϕPMMA dependency of N*, G* and Gc*, was estimated the immiscible system. The ΔT/Tm0 values, corresponding to Gibbs energy required to attend the constant G* and Gc*, evaluated from G* and Gc* showed the good linear relationships with different slope. The experimental results suggested that the concentration fluctuation
existed in PVDF/iso-PMMA system.
DSC analysis of wax/polymer blends is carried out between 270 and 420 K. Calibration for melting point and enthalpy is normally
carried out using indium (melting point 430 K), which is unsatisfactory for these materials. IUPAC organic standards covering
this range tend to sublime and their onset temperatures are variable. Pure alkanes have similar thermal characteristics to
wax/polymer blends and some have been well characterised by adiabatic calorimetry. They are being investigated as alternative
secondary calibration standards to give more accurate thermal characterisation of wax/polymer blends. Also,n-triacontane can be used to check DSC resolution.
Authors:H. Yoshida, G. Zhang, T. Kitamura, and T. Kawai
The mixing state of poly(vinylidene fluoride) (PVDF) and two amorphous polymers,poly(methyl methacrylate) (PMMA) and poly(isopropyl
methacrylate) (PiPMA) were investigated from the viewpoint of crystallization dynamics using simultaneous DSC-FTIR method.
The crystallization rate (R*) and the growth rate of trans-gauche-trans-gauche’ (TGTG’) conformation (Rc*) depended on both the blend content (ϕ) and the crystallization temperature for PVDF/PMMA. The temperature and ϕ dependency
of R* and Rc* were almost the same for PVDF/PMMA. However, R* and Rc* depended scarcely on f for PVDF/PiPMA, and the temperature dependency of R* differed from that of Rc* for PVDF/PiPMA. These results showed that PVDF and PMMA were miscible on molecular level, and that PVDF/PiPMA was immiscible
and the concentration fluctuation existed in the PVDF-rich phase.
Knowledge of the heat of mixing is very important in order to evaluate the interaction parameter, according to the Patterson theory. In this work we illustrate the results regarding some polymer blends, based on poly(vinyl acetate) and some polyacrylates with different substituent groups. In this way it is possible to understand the effect of the lateral group hindrance, as it will be illustrated in the paper.
The thermally induced phase separation behavior of hydrogen bonded polymer blends, poly(n-hexyl methacrylate) (PHMA) blended with poly(styrene-co-vinyl phenol) (STVPh) random copolymers having various vinyl phenol contents, was studied by temperature modulated differential scanning calorimetry (TMDSC).The enthalpy of phase separation was determined to be about 0.5 cal g–1 for one of the blends. A phase diagram was constructed from the TMDSC data for one of the blends. The kinetics of phase separation was studied by determining the phase compositions from the glass transition temperatures of quenched samples after phase separation. Subsequently, the phase separated samples were annealed at temperatures below the phase boundary to observe the return to the homogeneous state.
Authors:O. Slisenko, E. Lebedev, P. Pissis, A. Spanoudaki, E. Kontou, and O. Grigoryeva
The structure-property relationships of thermoplastic
polymer blends based on poly(ether-urethane) ionomer (PEUI) and ion-containing
styrene-acrylic acid copolymer (S-co-AA(K))
have been investigated by using DMTA, DSC and TGA, as well as tensile tests.
Convergence of the glass transition temperature (Tg)
values of the PEUI and the S-co-AA(K) components
in the blends studied, as compared to the individual polymers, was found and
explained by improving compatibility of the components due to increasing effective
density of physical networks formed by ion-dipole and ion-ion interactions
of ionic groups of the components. Character of E'=f(T) and E''=f(T) dependencies confirms the increase of the effective
density of physical networks in the compositions studied compared to individual
PEUI and S-co-AA(K). Improvement of end-use
properties, i.e. thermal stability and tensile properties has been found for
the PEUI/S-co-AA(K) compositions with lower
content of S-co-AA(K) (i.e. <10 mass%)
and explained by formation of additional network of intermolecular ionic bonds
between the functional groups of PEUI and S-co-AA(K).
The effects which an iron(III) based smoke suppressing compound have on the thermal stability of some acrylonitrile–butadiene–styrene/chlorinated
poly(vinyl chloride) (ABS/CPVC) polymer blends have been investigated. Thermogravimetric analysis (TG) experiments have shown that there are three distinctive
stages occurring during the thermal breakdown of these blends both when the iron compound is absent and present in the polymer
formulations. The most important effect which the iron compound has when it is present in these blends is to modify the decomposition
chemistry which takes place and the effect becomes more pronounced as the concentration of CPVC present in the blends increases. Other important effects are that the iron compound stabilises the blends so that mass loss
is significantly reduced (by up to 50% in some cases) and the onset temperature of decomposition is raised. Flammability data
generated during earlier work is supported by the TG results obtained in this work especially in the important area of smoke
formation and suppression.
Authors:E. Karavas, E. Georgarakis, and D. Bikiaris
In the present
study PVP/HPMC and PVP/Chitosan polymer blends were prepared by using the
solvent evaporation technique. From DSC studies were revealed that both blends
are completed miscible in the entire composition range since only one glass
transition temperature was detected. Miscibility can be attributed to the
strong interactions evolved between the carbonyl group of PVP, which acts
as strong proton acceptor, with hydroxyl and amino-groups of HPMC and Chitosan,
which are proton donors. Thus hydrogen bonds are easily formed, as was verified
by FTIR, producing miscible blends. However, the extent of interactions depends
from polymer composition and mainly from the ratio and the kind of reactive
groups. In PVP/HPMC blends a negative variation of Tg
is recorded while in PVP/Chitosan the variation has a sigma form. The miscibility
of these systems creates matrixes with completely different physical properties
in order to use as effective drug carriers. PVP/HPMC blends can be used as
pulsatile chronotherapeutics systems adjusting exactly the time of the drug
release while PVP/Chitosan blends can be used to control the release profile
of a poorly water soluble drug. In these blends HPMC and Chitosan respectively
are the control factors for the corresponding applications.