Authors:F. Cser, M. Jollands, P. White, and S. Bhattacharya
Cross-linked polymers have particular rheological responses during reprocessing, e. g. if the material is recycled, special
processing conditions are required. Other virgin polymers can be used as a blending component to enhance rheological properties.
Bi-layer film of EVA/LLDPE was produced on a blown film line and cross-linked by high-energy radiation. This film was ‘agglomerated’
then reprocessed in a twin-screw extruder with virgin LLDPE and blown into film. The miscibility of the blend components was
then studied using a TA Instruments temperature modulated differential scanning calorimeter (TMDSC).
It was found that the cross-linked EVA/LLDPE scrap and the LLDPE have a slight miscibility in the liquid state. A bigger portion
of LLDPE was miscible (dissolved) in EVA in low LLDPE blends. A positive deviation in the heat capacity of the LLDPE component
compared to the additivity rule indicated melting to be more reversible in the first heating cycle. This initial miscibility
was attributed to being induced by high shear during processing. A smaller positive deviation also occurred in the second
heating cycle. This was attributed to intrinsic miscibility.
Authors:B. Nandan, K. Pandey, G. Pandey, A. Singh, L. Kandpal, and G. Mathur
Binary blends of poly (ether sulphone) (PES) and Nylon-6 were prepared in a whole range of composition by melt extrusion.
Miscibility behaviour of the blends were studied using thermal analytical techniques like differential scanning calorimetry
(DSC) and dynamic mechanical analysis (DMA). Due to the rapid crystallization of Nylon-6 as it is cooled from the melt state,
its glass transition behaviour could not be detected even in the quenched samples by DSC. Furthermore, the crystallization
and melting behaviour of the blends have been studied by DSC. DMA results show that the dynamic storage modulus of the blends
were in-between those of the constituent polymers. Also the glass transition of Nylon-6 phase as determined by the peak in
loss tangent remains constant which shows that the two polymers are immiscible. Thermal expansion coefficient of the blends
as determined by TMA is greater than that of Nylon-6 signifying the increased dimensional stability of the blends at higher
temperatures. Morphological studies done by scanning electron microscopy (SEM) show the biphasic nature of the blends, with
clear cut boundaries between the phases because of poor interfacial adhesion. Dispersed particle size is small when Nylon-6
is the dispersed phase because of its lower melt viscosity as compared to PES. Thermal stability of the blends was measured
using thermogravimetric analysis (TG). Two-step decomposition behaviour was observed because of macro-phase separated morphology.
Authors:T. Watanabe, G. Zhang, H. Yoshida, and T. Kawai
The miscibility of crystalline syndiotactic polystyrene (SPS)/non-crystalline atactic polystyrene (APS) blend was estimated
by the crystallization dynamics method, which evaluated the nucleation rate, the crystal growth rate and the surface free
energy parameter. The melting temperature depression suggested that SPS/APS blends were the miscible system but not in molecular
level. The relationship between the blend content and the chemical potential difference evaluated at a constant crystal growth
rate showed a good linear relationship. These facts suggested that SPS/APS blends contained the concentration fluctuation
with the size between few nm to less than 80 nm.
The crystallization dynamics of Nylon 66/Nylon 6
blends, the crystalline/crystalline polymer blends, was analyzed by DSC under
isothermal conditions. The crystal growth rate (G)
and the nucleation rate (N) depended on
both the degree of supercooling (ΔT)
and the blend mass fraction (ϕ). The ΔT
values obtained at the fixed G, which corresponded
to the chemical potential difference of molecules between liquid and crystal
states, and the surface free energy parameters evaluated from G
and N depended on ϕ for blends. The
results suggested that Nylon 66/Nylon 6 blends with ϕN66≥0.80
or ϕN66≤0.15 are miscible.
Miscibility and dehydration of poly(2-hydroxyethyl methacrylate) and poly(methacrylic acid) (PHEMA/PMAA) blends were investigated
by temperature modulated DSC (TMDSC), TG and solid-state 13C NMR methods. TMDSC spectra and 1H spin-relaxation times showed that the blends are homogeneous on a scale of 5-10 nm for all compositions. From TG and 13C NMR, we elucidated that the mass loss of the blends at 300C is ascribed to the dehydration between the hydroxyl group of
PHEMA and the carboxyl group of PMAA.
Authors:Niko Van den Brande, Cor Koning, Paul Geerlings, Gregory Van Lier, Guy Van Assche, and Bruno Van Mele
decreased when the relative amount of compatibilizer increased, although only low percentages of compatibilizer showed this effect. Despite promising results, the especially low miscibility with PS coupled with its high mobility makes PDMS a challenging
Thermal stability and degradation processes in PVC/EVA systems were evaluated for a series of EVAs with different vinyl acetate
contents. The experimental data revealed a relationship between the thermogravimetric curves and the degree of interaction
in the mixtures as compared to the pure polymers, which is consistent with the results of microscopic analysis. Kinetic parameters
and lifetime data on the mixtures were also calculated.
Poly(vinyl chloride) was blended with ethylene-vinyl acetate copolymer containing 70 wt% of vinyl acetate. The system shows
a single glass transition temperature for all compositions, indicating their miscibility. TheTgvs. composition curves display an inflection, which changes with the chemical environment of the initial solution. The best fit
to the shape of the curve was well reproduced by the Kovacs-Braun equation. The δTg values reveal local heterogeneity, which means no total miscibility at a molecular level. Negative values of the Flory-Huggins
interaction parameter were obtained from the calorimetric data.
In order to provide additional information on the miscibility of the PVC/EVA system, calorimetric parameters such as ΔCpi,Tgi and ΔTgi were obtained with a different approach. A qualitative and quantitative measure of the blend composition at the interface
was obtained. This indicated that the domains are rich in each component and the presence of the second component in the phase
has little effect on the main chain relaxation. The PVC fraction in the EVA-rich phase is always larger than the EVA fraction
in the PVC-rich phase. Positive and small values of the Flory-Huggins interaction parameter were obtained from calorimetric