Authors:D. Filip, C. Simionescu, D. Macocinschi, and I. Paraschiv
Miscibility in blends of semicrystalline polymers (poly(ethylene) adipate and poly(tetrahydrofuran)) and liquid crystal cholesteryl
palmitate was investigated by means of differential scanning calorimetry and polarizing optical microscopy. Some(concentration-dependent)
miscibility was found. A more pronounced miscibility exhibits the polyester-based blends probably due to the similar chemical
structure of the two components and stronger interactions between the two components.
Nuclear magnetic resonance (NMR) spectroscopy has been used to study the morphology and dynamics in semicrystalline polymers.
Dynamics may be observed through NMR relaxation rates that are sensitive to motions in the 1–108 Hz range, or through modulation of anisotropic magnetic interactions, such as the chemical shift and dipole-dipole interactions.
Morphological structure may be inferred through NMR measurements of polymer dynamics or investigated directly through studies
of the magnetic interactions. Here, we discuss the study of morphological structure in semicrystalline polymers using NMR,
and review results on poly(ethylene terephthalate) that address the question of the number of phases in this semicrystalline
This is a study for criteria to judge the melting point of semi-crystalline polymers from the DSC endotherm for polymer melting. Beyond standard indium DSC melting results an evaluation has been made on a series of polyethylenes for which crystal sizes were measured and predicted from Raman LAM analysis. The results confirm the conclusion of Prof. Wunderlich that the DSC content of melting is the proper basis of reporting melting points.
The first experimental evidence of the existence of the rigid amorphous phase was reported by Menczel and Wunderlich :
when trying to clarify the glass transition characteristics of the first main chain liquid crystalline polymers [poly(ethylene
terephthalate-co-p-oxybenzoate) with 60 and 80 mol% ethylene terephthalate units] , the absence of the hysteresis peak at the lower temperature
glass transition became evident when the sample of this copolymer was heated much faster than it had previously been cooled.
Since this glass transition involved the ethylene terephthalate-rich segments of the copolymer, we searched for the source
of the absence of the hysteresis peak in PET. There, the gradual disappearance of the hysteresis peak with increasing crystallinity
was confirmed . At the same time it was noted that the higher crystallinity samples showed a much smaller ΔCp than could be expected on the basis of the crystallinity calculated from the heat of fusion (provided that the crystallinity
concept works). Later it was confirmed that the hysteresis peak is also missing at the glass transition of nematic glasses
When checking other semicrystalline polymers, the sum of the amorphous content calculated from the ΔCp at the glass transition, and the crystallinity calculated from the heat of fusion was far from 100% for a number of semicrystalline
polymers. For most of these polymers, the sum of the amorphous content and the crystalline fraction was 0.7, meaning that
ca. 30% rigid amorphous fraction was present in these samples after a cooling at 0.5 K min−1 rate. Thus, the presence of the rigid amorphous phase was confirmed in five semicrystalline polymers: PET, Nylon 6, PVF,
Nylon 66 and polycaprolactone . Somewhat later poly(butylene terephthalate) and bisphenol-A polycarbonate  were added
to this list.
In this paper we also report details on a special effect of the rigid amorphous phase (RAP) on the mobile amorphous phase
(MAP): the hysteresis peak at the glass transition of the MAF disappears under the influence of the RAP, and this raises the
question whether the glass transition of the MAF becomes time independent in semicrystalline polymers.
the influence of the RAF, and this raises the question whether the glass transition of the TAF becomes time independent in semicrystallinepolymers. It should be mentioned that here we talk about the hysteresis peak which is the consequence of slow
Confinement of the glass-forming regions in the nanometer range influences the α-relaxation which is associated with the glass transition. These effects were investigated for semicrystalline poly(ethylene terephthalate) by dielectric spectroscopy and differential scanning calorimetry. The results are discussed within the concept of cooperative length, i.e. the characteristic length of the cooperative process of glass transition. Both experiments showed a dependence of the glass transition on the mean thickness of the amorphous layers. For the dielectric relaxation, the loss maximum was found to shift to higher temperatures with decreasing thickness of the amorphous layers, but no differences were observed in the curve shape for the differently crystallized samples. For the calorimetric measurements, in contrast, there was no correlation for the glass transition temperature, whereas the curve shape did correlate with the layer thickness of the mobile amorphous fraction. From the structure parameters, a characteristic length of approximately (2.5±1) nm was estimated for the unconfined glass relaxation (transition).
A study is presented of the effect of empty space scattering in the estimation of the lattice thermal conductivity of four
samples of polyethylene with different degrees of crystallinity at temperatures between 0.4 and 20 K. This study was performed
by considering different values of the empty space fraction. It is found that empty space scattering plays a very important
role in the calculation of the lattice thermal conductivity of semicrystalline polymers.
Thermal properties such as melting and crystallization are important aspects in understanding the morphology and its contribution
to the physical properties of semicrystalline polymers, such as polypropylene. The inclusion of fillers, which are small particles
dispersed in the continuous polymer phase, often complicates the predictability of these properties by acting as nucleating
agents or defect origins.
This paper discusses the creation and use of empirical models based on experimental data for predicting and optimizing the
thermal properties of agricultural filler-polypropylene (AgFiller-PP) composites, including peak melting temperature (Tm), peak crystallization temperature (Tc) and percent of crystallinity (Xc). Experiments were performed using differential scanning calorimetry (DSC) to gather data necessary for building appropriate
prediction models. Finally, additional experiments were carried out to test the prediction results generated by the models.
Semicrystalline polymers are made of a crystalline phase and of an amorphous phase. Recently, NMR, Raman and FTIR experiments
have identified a third phase comprised of defects such as tie-molecules, in the organization of chains. Our investigation
of physical gels has led us to believe that by following the heat flow in a very slow temperature ramp (0.05 K min−1), phasechanges, unnoticed in the usual fast ramp, could be detected. These are associated to a physical network strained
in the temperature ramp. In order to obtain more information on the network phase, the polymer has been crosslinked The characteristics
obtained by slow calorimetry and turbidimetry of the original and modified materials are compared.