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Polyethylene Matrix (polyethylene + matrix)
Selected AbstractsEffects of two different maleic anhydride-modified adhesion promoters (PP-g-MA) on the structure and mechanical properties of nanofilled polyolefinsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2009P. Eteläaho Abstract The effects of adhesion promoter properties on the structure and mechanical behavior of nanoclay-filled polyolefin nanocomposites are presented. Two different maleic anhydride-modified polypropylenes having varying maleic anhydride content and molecular weight were used. The influence of these parameters on the performance and morphology of the prepared polypropylene and high density polyethylene-based nanocomposites was examined by mechanical testing, X-ray diffraction, and electron microscopy. The low molecular weight adhesion promoter seemed to be effective in both matrices in relation to mechanical property enhancements, whereas its high molecular weight counterpart performed well only in polyethylene matrix. X-ray diffraction results and examination of morphology revealed that the intercalation and the dispersion of the nanoclay were more even in both matrices when the low molecular weight adhesion promoter with a higher maleic anhydride content was used. On the other hand, the use of high molecular weight adhesion promoter led to a less uniform dispersion but also to a greater amount of exfoliated clay particles. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Reduction in tactoid size as a means for reinforcing high-density polyethylene/montmorillonite nanocompositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2009Carla Marega Abstract Nanocomposites were prepared by adding montmorillonite clay to a high-density polyethylene matrix. Their structure, morphology, thermal behavior, and physical, mechanical properties were studied. The filler did not alter much the structure and morphology of the matrix, with the exception of a disruptive effect on the lamellar stacks. The crystallization behavior, equilibrium melting temperature, and work of chain folding of the nanocomposites were also unaltered with respect to that of the PE base polymer. However, significant improvements in physical,mechanical properties were observed. The reason for this increase in performance was ascribed to the interaction between the filler and the matrix, especially because of a reduction in size of the original tactoids to stacks of just a few layers, albeit not intercalated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Core,shell structure and segregation effects in composite droplet polymer blendsAICHE JOURNAL, Issue 4 2003Joël Reignier Core,shell morphology formation within the dispersed phase was studied for composite droplet polymer-blend systems comprising a high-density polyethylene matrix, polystyrene shell and different molecular weights of poly(methyl methacrylate) core material. The blends were prepared in the melt using an internal mixer, and the morphology was analyzed by electron microscopy. Changing the viscoelastic properties of the core in the dispersed phase dramatically affects PS-PMMA segregation within the dispersed composite droplet itself. A high-molecular-weight-PMMA core contains a large quantity of occluded PS inclusions, while the low-molecular-weight PMMA results in a perfectly segregated PS shell and PMMA core. These phenomena were attributed to the viscosity of the PMMA. Using the latter system, a direct microscopic study of the shell formation process demonstrates unambiguously that under conditions of perfect segregation, the onset of complete shell formation corresponds to a shell thickness that is close to two times the radius of gyration of polystyrene. Thus, the thinnest possible shell in such a system possesses a molecular-scale thickness. The system with the high-molecular-weight-PMMA core demonstrates an onset of complete shell formation that is displaced to higher concentrations due to the poor segregation effect. By counterbalancing the effects of viscosity ratio and interfacial effects on the composite droplet size, it is possible to generate perfectly segregated core,shell dispersed-phase morphologies of almost identical size with a controlled shell thickness ranging from 40 to 300 nm. [source] Influence of Coupling Agents on Melt Flow Behavior of Natural Fiber CompositesMACROMOLECULAR MATERIALS & ENGINEERING, Issue 5 2007Velichko Hristov Abstract The influence of coupling agents on the melt rheological properties of natural fiber composites has been investigated in this work using capillary and rotational rheometers. Scanning electron microscopy was also employed to supplement the rheological data. It was found that molecular weight and molecular weight distribution of the polymer matrix and coupling agent characteristics influence the filler wetting and the melt flow properties of the filled composites. Generally, low molecular weight and narrow molecular weight distribution polyethylene matrix provides relatively larger increase of the viscosity of the composites. Coupling agents tend to increase the resistance to shearing, but wall slip effects may interfere with the measured values, especially at very high filler loadings. Entrance pressure loss in capillaries is also influenced by polymer matrix and coupling agent used. [source] In situ polymerization of polyethylene/clay nanocomposites using a novel clay-supported Ziegler-Natta catalystPOLYMER COMPOSITES, Issue 10 2009Ahmad Ramazani S.A. Polyethylene/clay nanocomposites (PECNC) were synthesized via in situ Ziegler-Natta catalyst polymerization. Activated catalyst for polymerization of ethylene monomer has been prepared at first by supporting of the cocatalyst on the montmorillonite (MMT) smectite type clay and then active complex for polymerization formed by reaction of TiCl4 and aluminum oxide compound on the clay. Acid wash treatment has been used for increasing hydroxyl group and porosity of the clay and subsequently activity of the catalyst. The nanostructure of composites was investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Obtained results show that silica layers of the mineral clay in these polyethylene/nanocomposites were exfoliated, intercalated, and uniformly dispersed in the polyethylene matrix even at very high concentration of the clay. Thermogravimetric analysis (TGA) shows good thermal stability of the PECNCs. Differential scanning calorimeter (DSC) results reveal considerable decrease in the crystalline phase of the PECNC samples. Results of permeability analysis show an increase in barrier properties of PECNC films. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers [source] Polyethylene-Palygorskite nanocomposite prepared via in situ coordinated polymerizationPOLYMER COMPOSITES, Issue 4 2002Junfeng Rong A polyethylene/palygorskite nano-composite (IPC composite) was prepared via an in-situ coordinated polymerization method, using TiCl4 supported on palygorskite fibers as catalyst and alkyl aluminum as co-catalyst. These composites were compared with those prepared by melt blending (MBC composites). It was found that in the IPC composites, nano-size fibers of palygorskite were uniformly dispersed in the polyethylene matrix. In contrast, in the MBC composites, the palygorskite was dispersed as large clusters of fibers. Regarding the mechanical properties of the IPCs, the tensile modulus increased and the elongation at break decreased with increasing fiber content, while the tensile strength passed through a maximum. The tensile strength and elongation at break were much smaller for the MBC composites. The final degree of crystallinity of the IPC composites decreased with increasing palygorskite content. Regarding the kinetics of crystallization, the ratio between the degree of crystallinity at a given time and the final one was a universal function of time. It was found that large amouns of gel were present in the IPC composites and much smaller amountes in the MBC composites. [source] Barrier properties of blends based on liquid crystalline polymers and polyethylenePOLYMER ENGINEERING & SCIENCE, Issue 9 2000G. Flodberg Blends of an extrusion-grade polyethylene and two different liquid crystalline polymers of Vectra type were prepared by melt mixing using poly(ethylene-comethacrylic acid) as compatibilizer. Oxygen and water vapor permeability, transparency and welding strength of compression molded and film blown specimens were studied. The compression molded blends showed gas permeabilities conforming to the Maxwell equation assuming low permeability liquid crystalline polymer spheres in a high permeability polyethylene matrix. One of the liquid crystalline polymers with suitable rheological properties formed a more continuous phase in the film blown blends and a substantial decrease in oxygen and water vapor permeability was observed in these blends. The compression molded blends with 50% liquid crystalline polymer and some of blow molded blends showed very high gas permeabilities. It is believed that voids forming continuous paths through the structure were present in these samples. The blends showed significantly higher opacity than pure polyethylene. [source] | ||||||||||