In this work, silane-grafted high-density polyethylene was prepared by reactive extrusion. This product and neat high-density polyethylene were then melt-compounded with organically modified montmorillonite to form nanocomposites. A series of tests, including Fourier transform infrared spectroscopy, small-angle X-ray diffraction, and transmission electron microscopy, were done on the specimens to investigate the grafting efficiency and its compatibilizing effect and the microstructure of the samples. In addition, the thermal, rheological, and barrier properties were examined to study of the grafting effects and nanocomposite characteristics. The results indicate that an intercalated structure could be easily obtained in the nanocomposites with a grafted matrix. A significant reduction in the degree of crystallinity and an increased crystallization temperature with grafting and the incorporation of nanoclay were proven by thermal analysis (differential scanning calorimetry), whereas the melting temperature did not change noticeably. Dynamic rheological testing indicated the disappearance of the Newtonian plateau and solidlike behavior of the nanocomposites based on grafted polyethylene in lower frequencies. Furthermore, the oxygen transfer rate of the samples decreased significantly with the incorporation of nanoclay in the grafted matrix and the moisture crosslinking of the samples. V C 2012 Wiley Periodicals, Inc. J Appl Polym Sci 125: E305-E313, 2012
Silane-grafted high-density polyethylene (HDPE-g-Si) was prepared by reactive extrusion. The grafted polyethylene (PE) was then melt compounded with organically modified montmorillonite and polyamide-6 (PA6) to form ternary nanocomposite. Fourier Transfer Infrared was used for investigation of grafting efficiency of specimens. Dispersion of clay in the blends and individual polymers were examined by X-ray diffraction (SAXS) and transmission electron microscopy (TEM). Scanning electron microscopy and dynamic rheology were also used for further study of microstructure along with compatibilization effect of silane grafting and adding organoclay in the blends. SAXS and TEM study showed that nanoclay was delaminated by PA6 or HDPE-g-Si chains, whereas the intercalation of neat HDPE in clay layers was negligible especially in higher level of clay. The morphological studies indicated that silane-grafted HDPE had hydrophilic characteristics and, therefore, was more compatible with PA6 than neat PE. Furthermore, in the same way adding nanoclay to this blends resulted in more uniform and finer morphology. And finally, results of oxygen and hydrocarbon permeability measurement demonstrated synergetic effect of silane grafting and presence of clay on barrierity improvement of samples.
In this work, the influence of organoclay incorporation along with silane grafting of high‐density polyethylene (HDPE) on compatibilization and morphology of HDPE/(polyamide‐6) (PA6) blends was investigated. Analysis by Fourier‐transform infrared spectroscopy was done for the investigation of grafting efficiency of specimens. Scanning electron microscopy and thermal properties (diffraction scanning colorimetry) were examined to study the effect of silane grafting as well as adding organoclay in compatibilizing blends. Small‐angle X‐ray scattering, transmission electron microscopy, and dynamic rheology (Rheometric Mechanical Spectrometer) were also used to explain morphological changes. The results of scanning electron microscopy indicated that silane‐grafted HDPE had hydrophilic characteristics and therefore was more compatible with PA6 than neat polyethylene. Furthermore, in the same way, adding nanoclay to this blend resulted in more uniform and finer morphology. Results of diffraction scanning colorimetry confirmed the compatibilizing effect of both silane grafting of polyethylene and use of organoclay in blends by showing a strong deviation of separate melting peak of PA6 in the composites to reduced intensity and shift to lower temperatures. J. VINYL ADDIT. TECHNOL., 21:191–196, 2015. © 2014 Society of Plastics Engineers
Long-chain branches are incorporated into the molecular backbone of a polypropylene (PP) in a foaming process. The branching of PP occurs by radical reactions of dicumyl peroxide and a tri-functional monomer, trimethylol propane trimethacrylate. Use of peroxide without tri-functional monomer results in scission of PP molecular chains and significant reduction in melt viscosity. The increase in melt viscosity in conjunction with the flow ability of the modified PP indicates that the polymer has a branched structure. Melting temperature of PP remains unchanged with branching reactions implying that reactions occur mainly in amorphous regions of PP. The improvement in melt strength and strain-hardening of the modified PP is examined by a batch foaming process. The foaming process conditions are optimized for the level of blowing agent, time and temperature of process, and talc content as nucleating agent. The formation of closed and evenly distributed cells in the foam structure verifies improvement in the rheological behavior of modified PP resulting from the presence of long branches in the molecular structure.
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