Search results for "Viscosity."
showing 10 items of 537 documents
A simple interpretation of the effect of the polymer type on the properties of PMBs for road paving applications
2018
Abstract The paper presents the results of the rheological characterisation of polymer-modified bitumen for paving applications. In order to find a simple interpretation of the influence of polymer type on the blends produced, in this study high density and low density polyethylene (PE) with different chemical properties were used, as well as ethylene-vinyl acetate. The chemical characteristics of the base bitumen and the polymers used were determined by means of SARA analysis and Fourier Transform Infrared Spectroscopy, FTIR, respectively. The morphology of the produced blends was investigated by means of fluorescent light optic microscopy, while the mechanical properties were investigated…
Rheology-morphology relationships in nylon 6/liquid-crystalline polymer blends
1990
Extrusion measurements have been carried out on blends of nylon 6 and a liquid-crystalline copolyesteramide (LCP). The flow curves at low temperature show a behavior similar to that of pure LCP with a rapid rise of the viscosity at low shear rates. At high shear rates the viscosity is lower than that for each of the two components. This minimum has been attributed to the lack of interactions between the two phases and to the formation of fibrils of the LCP phase. The SEM analysis shows, indeed, that fibrils of the LCP phase are produced in the convergent flow at the inlet of the capillary at high shear rates. These fibrils are lost during the flow in the long capillary.
Reprocessing of PLA/graphene nanoplatelets nanocomposites
2017
This work reports a study on the effect of multiple reprocessing on the properties of poly(lactic acid) (PLA) filled with graphene nanoplatelets (GnP) compared to the melt reprocessed neat polymeric matrix. In particular, morphological, X-Ray Diffraction and Micro-Raman analyses, intrinsic viscosity measurements, thermal, rheological and mechanical tests were carried out on materials reprocessed up five times by means of a single screw extruder. The results indicated that the presence of GnP decreased the degradation rate as a function of the reprocessing cycles in comparison with the neat PLA that, on the contrary, showed a more drastic reduction of the molecular weight. Moreover, the repr…
Modelling polycarbonate synthesis rates on the example of bulk heteropolyaddition of diphenyl carbonate and bisphenol A diglycidyl ether
2016
This paper investigates the effects of increased reaction mixture viscosity on the kinetics of linear polymer creation in a bulk polyaddition process of diphenyl carbonate and bisphenol A diglycidyl ether. The paper presents a method for solving a system of bulk polyaddition of diphenyl carbonate and bisphenol A diglycidyl ether process balance equations, allowing the determinatiof the process kinetic parameters. Determination of polymerisation reaction kinetic parameters was also made possible by the use of the so-called partial reaction rate constant. Such an approach enabled a significant simplification of the mathematical expressions describing the heteropolyaddition process and provide…
Physical properties of virgin-recycled ABS blends: Effect of post-consumer content and of reprocessing cycles
2012
Abstract Virgin/post-consumer ABS (pc-ABS) blends were re-processed and re-formed up to three times. The effect of pc-ABS content and of reprocessing cycles on the physical properties of the prepared blends was evaluated by mechanical tests (tensile, flexural and impact tests) and by rheological and thermo-mechanical measurements. The processability of pc-ABS blends was not substantially different by that of virgin ABS up to two recycling steps even if the third one induced a slightly decrease of viscosity, more remarkable on increasing the pc-ABS content. The mechanical and thermo-mechanical properties of the samples worsened on increasing the level of pc-ABS and after each reprocessing op…
Rheology of a Lower Critical Solution Temperature Binary Polymer Blend in the Homogeneous, Phase-Separated, and Transitional Regimes
1996
Small amplitude oscillatory shear rheology is employed in order to investigate the linear viscoelastic behavior of the lower critical solution temperature blend polystyrene/poly(vinyl methyl ether), PS/PVME, as a function of temperature and composition. At low temperatures, where the mixture is homogeneous, the dependence of the zero shear viscosity (η0) on concentration is measured and is well-described by means of a new mixing rule, based on surface fractions instead of volume fractions. Shift factors from time-temperature superposition (TTS) exhibit a Williams−Landel−Ferry (WLF) behavior. As the macrophase separation temperature is approached (the phase diagram being established by turbi…
Creep response of a LDPE-based nanocomposite
2016
Polymer nanocomposites and their behavior have been widely investigated by several paths, including mechanical, rheological, and permeability tests, finding that several parameters (such as the polymer matrix, the nanofiller, their amounts, the presence of compatibilizers, processing parameters, etc.) can influence the main properties. However, less information is available regarding the creep response of polymer nanocomposites; in particular, few or no data are reported about the combined effect of different loads and different temperatures. In this article, the creep behavior of a low density polyethylene/organomodified clay nanocomposite has been investigated. The characterization of vis…
Photooxidation Behavior of a LDPE/Clay Nanocomposite Monitored through Creep Measurements
2017
Creep behavior of polymer nanocomposites has not been extensively investigated so far, especially when its effects are combined with those due to photooxidation, which are usually studied in completely independent ways. In this work, the photooxidation behavior of a low density polyethylene/organomodified clay nanocomposite system was monitored by measuring the creep curves obtained while subjecting the sample to the combined action of temperature, tensile stress, and UV radiation. The creep curves of the irradiated samples were found to be lower than those of the non-irradiated ones and progressively diverging, because of the formation of branching and cross-linking due to photooxidation. …
Analysis of stability of food emulsions by Eyring's Theory: Influence of different biopolymers
2004
Eyring's kinetic theory of liquids was applied to the study of flow behavior of low oil content mayonnaises at different temperatures. These food emulsions were formulated with different biopolymers as stabilizers (polysaccharides such as modified starch, gellan gum, and pectin). The analysis of the values obtained for the parameters of the Eyring equation for viscosity determined the emulsion containing only starch as a stabilizer is the most unstable to stirring. Replacement of part of the starch with gellan gum or pectin enhances the stability of the emulsion. The results for activation energy are quite similar for high shear rates, which can be explained by the evolution of the average …
Redesign of the Geometry of Parts Produced from PBT Composite to Improve Their Operational Behavior
2021
Parts produced from PBT-GF30 (70% polybutylene terephthalate +30% fiberglass) are very often used in car construction, due to the properties of this material. The current trend is to make parts with a shape designed to be as complex as possible, to take over many functions in operation. During the research, a part that is a component of the structure of car safety systems, and that must be completely reliable in operation, was analyzed. This piece has a complex shape that involves the intersection of several walls. Thus, the research aimed at establishing the optimal radius of connection between the walls (R), the ratio between the thickness of the intersecting walls (K) and the angle of in…