Search results for "Plastics"
showing 10 items of 2724 documents
Morphology and transport parameters of cold-rolled low-density polyethylene
1986
Abstract Sheets of low-density polyethylene were rolled at room temperature. Samples with two different degrees of rolling were obtained. The structural changes induced by the rolling treatments were investigated using scanning electron microscopy and by analyzing the transport properties. Results suggest that in the analyzed range of deformation, the rolling induces a domain structure as a consequence of a nonhomogeneous distribution of the deformation. At lower local deformation the initial morphology is still present, while at higher deformation clumps of folded chains oriented along the rolling directions are observable. The transport properties indicate that the rolling treatment reduc…
Physical behavior and morphology of biaxially rolled low-density polyethyleneX
1989
Abstract Biaxial rolling was carried out on low-density polyethylene, and the rolled samples were studied using various techniques. Scanning electron microscopy and analysis of transport properties were used to obtain structural information, which was correlated to thermomechanical and dynamic-mechanical behavior. Results indicate that the initial morphology is destroyed by rolling and that clumps of molecules, like fibrils, are generated parallel to the rolling plane. The molecular orientation in the plane is mainly radial, with some reinforcement, particularly at high rolling degree, along axes diagonal with respect to the rolling directions. The rolling drastically reduces the molecular …
Structural Characterization of the “Knitting Pattern” in Polystyrene-block-poly(ethylene-co-butylene)-block-poly(methyl methacrylate) Triblock Copoly…
1998
In a polystyrene-block-polybutadiene-block-poly(methyl methacrylate) triblock copolymer (SBM) a morphological transition from a lamellar (ll) morphology (with sequence ABCB) to the knitting pattern (kp) morphology occurs upon hydrogenation of the center PB block. Structural information of the nonhydrogenated and the hydrogenated material is provided from small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). For the nonhydrogenated SBM sample the SAXS profile correlates well with a simple periodic lamellar structure. The hydrogenated sample forming the kp morphology displays a more complex SAXS pattern. From the TEM images of the knitting pattern the two-dimensional…
Effect of a Compatibilizer on the Morphology and Properties of Polypropylene/Polyethylentherephthalate Spun Fibers
2017
Fibers spun by melt spinning of binary and ternary polypropylene/ polyethylenetherephthalate blends have been produced and characterized in order to investigate the effect of a compatibilizer on their morphology and mechanical properties. The compatibilizer was a maleic anhydride-functionalized rubber copolymer. The effect of the compatibilizer was well evident in the isotropic state, as the morphology became very fine, the size of the dispersed particles was very small, and the adhesion was better. The effect of the compatibilizer on the mechanical properties is very relevant, especially in the elongation at break. On the contrary, no relevant effect was observed in the anisotropic oriente…
Morphology Modification of Polyethylene/Clay Nanocomposite Samples under Convergent Flow
2009
The morphology of PE/CL nanocomposite samples subjected to convergent flows is studied. Elongational flow – the typical flow involved in spinning and film-blowing processing operations – significantly increases with the reduction of the capillary diameter. The values of the convergent extensional stress (calculated by Cogswell's formula) for the PE/CL systems, for all the adopted capillary geometries, are greater than the calculated values for pure polyethylene. The applied convergent flow, at the entrance of the capillary, is able to change the clay morphology and consequently the final material properties on the PE/CL system with limited affinity between the matrix and organo-modified cla…
Compatibilized Polyamide 6/Polyethylene Blends Clay Nanocomposites: Effect of the Degradation and Stabilization of the Clay Modifier
2008
Abstract Blends of polyamide 6 (PA6) and high-density polyethylene (HDPE) were compatibilized using an already investigated method and a sample of Cloisite 15A, a montmorillonite modified with ammonium quaternary salts was added. The blends were prepared in a twin screw extruder and characterized from a morphological, rheological and mechanical point of view. The results indicated that, despite a good morphology achieved in the filled blends and a moderate intercalation of the clay, the mechanical properties are far from being good, especially the ultimate properties. In order to investigate the possible influence of the inhibition of the crystallization and of the degradation of the organi…
Photo-oxidation behaviour of polyethylene/multi-wall carbon nanotube composite films
2009
Abstract The resistance to accelerated photo-oxidation of polyethylene/multi-walled carbon nanotubes (MW-CNTs) composite films was compared with the photo-oxidation behaviour of pristine polyethylene film. The polyethylene/MW-CNTs films containing different CNTs loading were subjected to accelerated UV-B exposure. At short exposure time, i.e. under 200 h, the rates of carbonyl formation are very similar to that observed for pristine polyethylene film but at longer irradiation times the carbonyl formation increases for lower MW-CNTs contents (0.1, 0.2 and 0.5% wt./wt.), and decreases for higher MW-CNTs contents (1 and 2% wt./wt.). By adding a UV-stabilizer to the films their photo-oxidation …
The role of organoclay and matrix type in photo-oxidation of polyolefin/clay nanocomposite films
2009
Abstract In this paper the photo-oxidation behaviour of polyolefin/clay nanocomposite films was studied; in particular, the effect of the amount of organo-modifier and the matrix polarity on the photo-oxidation was investigated. Two different organo-modified clays and compositions of LDPE/EVA blend films were used and the photo-oxidation was followed by mechanical and spectroscopic analyses. The organoclay and matrix type strongly influence the photo-oxidative behaviour of nanocomposite films. The films filled with CL15A show a faster loss of mechanical performance and higher carbonyl formation with respect to the films filled with the CL20A. Additionally, the LDPE based nanocomposite under…
Morphology and Properties of Polyethylene/Clay Nanocomposite Drawn Fibers
2008
The influence of an elongational flow on the morphology of PE/clay nanocomposite drawn fibers was studied. An increase of the elastic modulus and the tensile strength as well as a decrease of the elongation at break are observed with increasing draw ratio. The applied elongational gradient orients the polymer chains and the clay particles along the spinning direction. When the applied flow results in the formation and the orientation of exfoliated nanoparticles, a pronounced increase of the mechanical properties is observed. The dispersed clay particles can be broken and oriented by the extensional flow, which might indicate a flow induced intercalated/exfoliated morphology transition.
The Effect of Calcium Carbonate on the Photo-Oxidative Behavior of Poly(butylene adipate-co-terephthalate)
2020
The aim of this work is to evaluate the influence of nanosized CaCO3 on the photo-oxidation of poly(butylene adipate-co-terephthalate) (PBAT)-based nanocomposites. The PBAT/CaCO3 nanocomposites are prepared by using a corotating twin-screw extruder with 0, 2, and 5 wt% of CaCO3. The films are obtained by film blowing process. Specimens of the nanocomposites and that of the pure polymer are subjected to accelerated aging with a cycle of 8 h of light at a temperature of 55 °C followed by 4 h condensation at 45 °C to evaluate the effects of the CaCO3 addition on the photo-oxidation of PBAT. The results indicate that the modulus and tensile strength of the nanocomposites are increased significa…