Low density polyethylene(LDPE)/lignin blends were prepared using melt blending.Two kinds of compatibilizers, ethylene-vinylacetate(EVA) which is softer than LDPE and polyethylene grafted with maleic anhydride(PE-g-MA) which is harder than LDPE were used to improve the interfacial adhesion.Scanning electron microscope(SEM) was used to investigate the dispersion of lignin in LDPE matrix.The results showed that both of the compatibilizers could improve the interaction between the low density polyethylene and l...
A relatively high predetermined crystallization temperature (135℃) was chosen to grow well developed iPP spherulites, then the partial melting was carried out at a temperature of 165℃, where the preformed spherulites were seen to only decrease their size but not completely melted. The crystallization behavior of partially melted isotactic polypropylene (iPP) has been carefully examined by different scanning calorimetry (DSC) and polarized light microscopy (PLM). The experimental results show that at a special annealing temperature (165℃) the melting behavior of iPP includes two parts with different mechanism, one part is the melting of iPP spherulite outside, another is the partial lamellae perfection during longer annealing time in the unmelted spherulite. The conformational orders of the iPP melt decrease with the increase of the annealing temperature.
Double melting behavior of poly(trimethylene terephthalate) (PTT) was studied in detail by means of differential scanning calorimetry (DSC) and optical microscopy. The results indicate that the low-temperature melting peak of PTT at ca. 218℃ for the samples crystallized isothermally at 203℃ is associated with the melting of crystals produced by secondary crystallization, while the high-temperature melting peak of it at about 227℃ is related to the melting of the crystals produced by primary crystallization. The results further demonstrate that the PTT crystals growing non-isothermally during cooling process are thermodynamically unstable and can undergo structure reorganization during the DSC heating scan. The reorganized crystals melt at temperature higher than the crystals produced by secondary crystallization at 203 ℃. Consequently, for the non-fully crystallized samples, the crystals grown during cooling also exhibit contribution to the high-temperature melting peak.
The crystalline structure and morphology of the PLA crystallized isothermally from the glassy state on highly oriented PE substrates at 130℃ were investigated by means of optical microscopy, AFM and X-ray diffraction. The results indicate that the PE substrate influences the crystallization behavior of PLA remarkably, which leads to the growth of PLA crystals on PE substrate always in edge-on form rather than the twisted lamellar crystals from edge-on to flat-on when crystallizing the PLA on glass surface under the same condition. The edge-on PLA lamellae on the PE substrate are preferentially arranged with their long axes in the chain direction of the PE substrate crystals. It is further demonstrated that except for the different crystal orientation, the PE does not influence the crystalline modification and crystallinity of the PLA.