ABSTRACT:In the present article, a series of commercial-grade polypropylenes (PP) filled with different contents of short basalt fibers were studied. This composite material presented deterioration of both mechanical characteristics, for example, stress and strain at yield with increasing of the fiber content. On the other hand, the impact strength was fourfold higher than that of unfilled PP. A poor adhesion between the PP matrix and the basalt fibers was detected. This is why interfacial interactions were promoted by the adding of poly(propylene-g-maleic anhydride) (PP-g-MA). It was observed that the tensile properties of the obtained materials and their impact strengths increased significantly with increasing of the amount of PP-g-MA in the blend. The adhesion improvement was confirmed by scanning electron microscopy as well. Fourier transform infrared spectroscopy was applied to assess if any chemical interactions in the system PP/PP-g-MA/basalt fibers exist. Dynamic mechanical thermal analysis data showed an increase of the storage modulus with increasing fiber content. The conclusion was made that the modification of the PP matrix led to a higher stiffness but its value remained constant, irrespective of the PP-g-MA content. With increasing fiber content, damping in the ␤-region decreased, but increase of the coupling agent content restored its value back to that of PP. The loss modulus spectra presented a strong influence of fiber content on the ␣-relaxation process of PP. The position of the peaks of the above-mentioned relaxation processes are discussed as well.

ABSTRACT:The miscibility of different polymer blends was studied with dynamic mechanical thermal analysis (DMTA) in conjunction with differential scanning calorimetry (DSC). The blends were prepared by melt mixing polymers having similar glass transitions such as polyglutarimide (PGI), styrene-co-maleic anhydride random copolymers (SMA), and polystyrene (PS). In PGI/SMA blends, there is only one glass transition detected with DMTA. In the case of PGI/SMA14 blends, the single glass transition temperature is due to their full miscibility. However, PGI/SMA8 blends are immiscible throughout the whole composition range as was verified by optical observation (opaque appearance), DSC, and scanning electron microscopy. The observation of only one glass transition by DMTA was attributed to weak interactions that take place between the two polymers, leading to partial mutual solubility and bringing the slightly different T g temperatures of the pure polymers even closer. In SMA8/SMA14 blends, there are two glass transitions detected with DSC as well as with DMTA, indicating that the two copolymers are immiscible. However, in all compositions, shifts of the glass transitions were observed with DMTA, which is evidence of partial miscibility. The observation of immiscibility was easiest in PS/SMA blends by both techniques, because of the bigger difference in glass transition temperatures of the initial polymers.

In the present article a series of low-density polyethylene (LDPE) blends with different amounts of fatty esters of amylose and starch, were prepared in a Haake-Buchler Reomixer. The tensile as well as the dynamic thermomechanical (DMTA) properties of the blends were measured. It was found that as the amount of the esters increases in the blends, the tensile strength and especially the elongation at break decrease nonlinearly. Scanning electron microscopy (SEM) was used to assess the interfacial adhesion between LDPE and the corresponding esters. The incompatibility of the blends was also verified with DMTA and differential scanning calorimetry (DSC). From the biodegradation studies of the blends during exposure in activated sludge, it was found that all esters are biodegradable, although to a much lesser degree compared to pure strach. The biodegradation rate of the composites is relatively small due to the low biodegradation rate of the pure esters.

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