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Phase structure and viscoelastic properties

Polypropylene-polystyrene systems with various dispersion of PS component

Journal of Thermal Analysis and Calorimetry
Authors: M. Pluta, J. Morawiec, M. Kryszewski, and T. Kowalewski

The phase structure and dynamic mechanical properties of three polypropylene/polystyrene (PP/PS) systems of similar composition but various dispersion of the minor PS component have been examined. Two different PP/PS systems were prepared by polymerization of styrene (ST) molecularly dispersed in PP matrices (with the same initial structure) under the conditions leading to a linear or crosslinked PS component. The third PP/PS system has been prepared blending the homopolymers in the molten state. Studies of materials containingin situ polymerized PS revealed nanoscale phase separation of PS (atomic force microscopy) and pointed to the presence of physical entanglements between PS and non-crystalline phase of PP (DSC, dynamic mechanical analysis). The PS component in material prepared by melt mixing appeared to be completely phase-separated into micron-sized domains. Dynamic mechanical analysis revealed also the dependence of viscoelastic behavior of the PP/PS systems on dispersion of the PS inclusions and on the nature of the interface.

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A complex of methodical approaches for investigating structural changes under the influence of temperature are presented on the basis of modern concepts of the domain structure of block copolymers. Effects of formation of structure due to phase segregation, crystallization processes and those of thermal homogenization have been considered in connection with the deformational properties of polymers. One and the same polymer appears to have quite different phase structures and properties when obtained by altering its thermal conditions. Thermomechanical analysis is shown to be a most efficient technique for investigating the changes in the phase structure of a wide series of polyether(ester)urethanes and -urethaneureas.

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Relations are demonstrated between the conductivity, phase structure and thermal history of some solid polymeric electrolytes. The results obtained for systems based on commercially available polymers, e.g. (ethylene oxide), and for specially synthesized materials are presented. Special emphasis is placed on the correlation between the crystallinity, glass transition temperature, melting temperature and conduction properties of the polymeric electrolytes.

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Abstract  

Nanofibrous composite mats were prepared by electrospinning of poly(trimethylene terephthalate), PTT, with multi-walled carbon nanotubes (PTT/MWCNT). Trifluoroacetic acid (TFA) and methylene chloride (MC) with volume ratio of 50/50 is a good solvent for PTT and was used as the electrospining solution. Scanning electron microscopy was used to investigate the morphology of electrospun (ES) nanofibers with 0, 0.2, 1.0, or 2.0 wt% of MWCNTs. Crystal structure of the ES mats was determined from wide angle X-ray diffraction. Thermal properties were investigated using heat capacity measurements from differential scanning calorimetry (DSC) using the three-runs method for baseline correction, heat flow amplitude calibration, and sample heat capacity determination. A model comprising three phases, a mobile amorphous fraction (MAF), rigid amorphous fraction (RAF), and crystalline fraction (C), is appropriate for ES PTT/MWCNT fibers. The phase fractions, W i (for i = RAF, MAF or C) were determined by DSC. Crystallinity decreases very slightly with the amount of MWCNT. At the same time, a large increase in RAF was observed: W RAF of PTT fiber with 2% MWCNT is twice that of neat PTT fiber. The addition of MWCNTs enhanced the PTT chain alignment and increased RAF as a result. Changes of vibrational band absorbance at 1358 and 1385 cm−1, corresponding to characteristic groups, were obtained with infrared spectroscopy. The increased absorbance at 1358 cm−1 and decreased absorbance at 1385 cm−1, with the addition of MWCNTs, strongly supports the three-phase model for ES PTT/MWCNT nanocomposites.

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Abstract  

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 (T g) 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).

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Abstract  

Two series of multiblock copolymers, poly(ester-block-amide)s (PEA) and poly(amide-block-amide)s (PAA), with the same type of oligoamide soft block were obtained. Oligoamide soft block was prepared from dimerized fatty acid and 1,6-hexamethylenediamine. Oligo(butylene terephthalate) (PBT) was used as oligoester hard block in the first series and oligolaurolactam (PA12) was oligoamide hard block in the second one. The thermal and mechanical properties of these copolymers have been investigated as functions of temperature and the hard/soft block ratio. DSC and DMTA revealed that the copolymers behaved as thermoplastic elastomers.

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Abstract  

Multiblock terpolymers -(PBT-b-PTMO-b-PA12.10)n- comprising the polymer systems in which one of the three blocks (PBT) is not soluble in the hard phase of PA12.10 blocks but is slightly soluble in the soft phase of PTMO blocks have been obtained. The DSC and DMTA method was applied to investigate the thermal properties of these polymers and it was found that the PBT block acts as an element that produce stiffness of -(PBT-b-PTMO-b-PA12.10)n- structure. The terpolymers were compared with the previously described [5] -(PBT-b-PTMO-b-PA12)n- elastomers, in which the rigid PBT block (DP > 7) dissolves in the hard phase of PA12 blocks and partly dissolves in the soft phase. It was found that even a small change in the chemical structure of the amide block influences significantly on the structure, phase separation and the properties of terpolymers.

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fibers with highly regular diameters and smooth surfaces could be obtained. A series of studies has been carried out in our group to characterize the morphology, thermal transitions, and phase structures of electrospun nanocomposite fiber [ 9 , 14 , 15

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Abstract  

Thermal stability and phase structure of thermoplastic elastomers (TPEs) based on post-consumer materials such as recycled lowor high-density polyethylene and ground tyre rubber (GTR) were investigated by using TG, DSC and DMTA analysis. Preliminary reclamation of GTR leads to enhancement of compatibility between polyethylene matrix and dispersed GTR particles.

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Journal of Thermal Analysis and Calorimetry
Authors: A. Wolnik, J. Borek, W. Sułkowski, M. Żarska, W. Zielińska-Danch, and A. Danch

Abstract  

Thermogravimetry was applied in order to study the variety of the phase structure of poly(4-methyl-1-pentene) (PMP) membranes. The results gave indirect information about the morphology of the polymeric systems. DTG curves, recorded for the membranes including residual amount of solvent, exhibited three processes. The processes were interpreted as a removal of the solvent molecules occluded in different local structures: ‘real’ amorphous; ‘semi-ordered’ amorphous, crystalline. The location of the molecules in those structures was correlated with chain behaviours studied using dynamic mechanical analysis. The relaxation processes (αg, αc) were analysed with a special attention to the amount of occluded solvent molecules.

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