ABSTRACT:The presence of aggregates of CaCO 3 nanoparticles in an isotactic polypropylene matrix processed by extrusion promotes the apparition of residual stresses. These stresses are removed with a thermal treatment of the composite, but a higher molecular orientation is then produced. The chain orientation inside the sample is nonhomogeneous due to the presence of the aggregates of nanoparticles.

No abstract

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. ACCEPTED MANUSCRIPT

No abstract

Fourier transform (FT) Raman spectroscopy has been proved to be an adequate technique for the study of the quantitative structural changes which take place in poly(ethy1ene terephthalate) on annealing. The two-phase conformational model proposed previously in the infrared domain using photoacoustic FTIR has been extended to the Raman domain. Moreover, typical Raman spectral changes with the thermal process have been directly related to conformational rather than crystallinity changes. The correlation between the percentage of the trans isomer obtained by FT-Raman and skin layer crystallinity values obtained by differential scanning calorimetry allows the crystalline and amorphous trans isomer contents to be obtained and their evolution with the annealing process to be followed.

It has been well documented that the use of dry optics in depth profiling by confocal Raman microspectroscopy significantly distorts the laser focal volume, thus negatively affecting the spatial resolution of the measurements. In that case, the resulting in-depth confocal profile is an outcome of several contributions: the broadening of the laser spot due to instrumental factors and diffraction, the spreading of the illuminated region due to refraction of the laser beam at the sample surface, and the influence of the confocal aperture in the collection path of the laser beam. Everall and Batchelder et al. developed simple models that describe the effect of the last two factors, i.e., laser refraction and the diameter of the pinhole aperture, on the confocal profile. In this work, we compare these theoretical predictions with experimental data obtained on a series of well-defined planar interfaces, generated by contact between thin polyethylene (PE) films (35, 53, 75, and 105 microm thickness) and a much thicker poly(methyl methacrylate) (PMMA) piece. We included two refinements in the above-mentioned models: the broadening of the laser spot due to instrumental factors and diffraction and a correction for the overestimation in the decay rate of collection efficiency predicted by Batchelder et al. These refinements were included through a semiempirical approach, consisting of independently measuring the Raman step-response in the absence of refraction by using a silicon wafer and the actual intensity decay of a thick and transparent polymer film. With these improvements, the model reliably reproduces fine features of the confocal profiles for both PE films and PMMA substrates. The results of this work show that these simple models can not only be used to assist data interpretation, but can also be used to quantitatively predict in-depth confocal profiles in experiments carried out with dry optics.

The diffusion of a liquid polymer into a glassy polymer matrix has been studied in a range of temperatures below the glassy matrix glass transition temperature (T g) and for different diffusion times. The liquid polymer used is low-molecular-weight polystyrene (PS) with a narrow molecular weight distribution, and the glassy matrix is poly(phenylene oxide); the two are miscible at any concentration. A simple physical diffusion model is proposed to correlate and predict diffusion rates, assuming a relatively rapid dissolution of the high-Tg polymer at the liquid-solid interface and a relatively slow diffusion process that produces a thick interphase. The local chemical compositions, local glass transition temperatures, and local PS monomeric friction coefficients change markedly along the diffusion path across the interphase; these changes are well predicted by the diffusion model and have also been experimentally verified. The large changes in local T g values cause huge changes in the PS monomeric friction factor across the interphase, and this fact explains the asymmetrical local chemical composition profiles experimentally measured for the PS-rich interphase. The results obtained by other authors for the diffusion of liquid polymers and bulky plasticizers into glassy matrixes are analyzed and discussed on the basis of the diffusion model predictions, and it is found that all of them behave following the same pattern as was observed in our experiments. It is concluded that the Case II diffusion mechanism must not be expected for the diffusion of liquid polymers into glassy matrixes, because of the negligible osmotic pressure. Furthermore, all of the analyzed data for diffusion of liquid polymers and bulky plasticizers into glassy matrixes show evidence for relatively rapid dissolution of the glassy matrix at the interface, together with a relatively slow diffusion process across the interphase.

No abstract