Summary: Recycled PET as well as ABS - organomodified montmorillonite nanocomposites were prepared via melt compounding in a counter-rotating twin screw extruder. The topological changes in polymer matrices as dependency on clay modification have been evaluated from dynamic experiments in the shear flow using low amplitude oscillatory measurements. Flow characteristics of all studied organoclay nanocomposites showed shear-thinning behavior at low frequencies. Filling of PET with some organoclays led to degradation reactions, which were reflected by lower magnitudes of viscosity and storage modulus in the range of higher frequencies as compared to unfilled polymer matrix. On the contrary, no degradation during the processing of different organoclays with recycled ABS has been observed. 相似文献
Rheology is an important tool for evaluating the potential application of a specific material in the production of blow molding films. In the present study, binary and ternary blends based on two different grades of polystyrene (PS) and high impact polystyrene (HIPS) were prepared by melt mixing in a twin screw extruder, using a simplex-centroid mixture design. Rheological analysis was performed based on elongational and dynamic rheology tests combined with scanning electron microscopy. Based on the rheology tests performed, the PS1/HIPS (50:50 wt.%) binary blend is a promising candidate for use in blow molding film applications. 相似文献
In this paper the effect of different organoclays on the structure and the rheological properties of poly(butyleneterephtalate)–clay nanocomposites produced by melt compounding was investigated. The study was carried out using as nanometric fillers four commercial montmorillonites, treated with different organic modifiers and having similar interlayer spacing and organo-modifier concentration. Each organoclay was melt compounded with PBT (at 3%, 6% and 9% by weight of clay) using a twin screw extruder. Using the same processing conditions, hybrid samples containing the unmodified silicate were also prepared for comparison purposes. All the obtained nanocomposite samples were submitted to physico-chemical (XRD, TEM and FT-IR), and rheological measurements in order to evidence the role of polymer-clay affinity on the morphology and on the viscoelastic response of the materials. The results have pointed out that, with the used processing conditions, all nanocomposites exhibit a mixed intercalated/exfoliated structure; nevertheless, the clay dispersion homogeneity and the exfoliation level reached in the samples are higher for Nanofil 919 and Dellite 43B fillers, the organic modifiers of which may favorably interact with PBT matrix. 相似文献
In our present study, the reprocessability of a self-reinforced PP composites (SRPPC) prepared by compression molding was
studied. The composite materials (handled separately, based on the related matrix material) were ground, then extruded five
times and injection molded after the first and fifth cycle in order to investigate the behaviour of the material during reprocessing.
As a reference, the matrices of the composites were also reprocessed and injection molded similarly to the composites. On
the manufactured specimens, static (tensile and flexural) and dynamic mechanical tests (Charpy) were performed. The melting
and crystalline characteristics were studied by Differential Scanning Calorimetry (DSC). The probable decomposition caused
by multiple extrusions was followed by the Melt Volume Rate (MVR). The results indicated that in case of commercial materials
there is no significant degradation even after multiple reprocessing cycles; therefore, the reprocessability of SRPPC products
has no hindrance. The presence of α-iPP reinforcement in the rPP-based composites after reprocessing results in increased
inclination for crystallization and consequently leads to improved mechanical stiffness compared to rPP neat matrices. 相似文献
The control of the molecular weight distribution of poly(propylene) resins by peroxide degradation is widely used in polymer industry. It allows to adjust the viscosity of these resins to the level required for processing applications. The purpose of this work was to characterise the influence of peroxide degradation on the rheological behaviour of an homopolymer PP and a block copolymer PP/PE, and to use these results to obtain a predictive model of the degradation in a twin‐screw extruder. By coupling a thermomechanical model of the twin‐screw extrusion process, a kinetic model of the considered reactions and the rheological behaviour, it was possible to calculate the changes in molecular weight along the extruder, during the peroxide‐controlled degradation. 相似文献
A new sodium carboxymethylcellulose (CMC) compatibilized glycerol-plasticized starch/polyamide PA11 blend having improved mechanical properties was realized in a one step extrusion process. Blends were prepared in internal mixer and twin screw extruder. Mechanical properties (stress and strain at break) are improved by adding 1 wt% of CMC. Rheological characterization and scanning electron microscopy show that a co-continuous morphology is observed on a wide range of TPS amount. 相似文献
The kinetics of L-lactide ring-opening polymerization initiated by stannous octoate and triphenylphosphine was investigated in a batch apparatus (Haake Rheocord Mixer). Based on the experimental data, a kinetic model is developed, considering a coordination-insertion mechanism. Reactive extrusion experiments were further conducted for the same polymerization process, on a co-rotating twin screw extruder. The melted material flow and mixing was described by using the Ludovic® commercial simulator. Based on the developed kinetic model and simulated flow of L-lactide polymerization mixture, a mathematical model of reactive extrusion process is formulated, describing the evolutions of monomer conversion and average molecular weight along the extruder. The model is predicting with a reasonable good accuracy the experimental data. 相似文献
PA1012/calcium silicate whisker nanocomposites with contents of whisker ranging from 10 wt% to 40 wt%, are prepared by twin screw extruder without any additions of coupling agent. The effect of whisker on the matrix is analyzed by the studies of morphology, the mechanical properties, water absorption and thermal stabilities. SEM micrographs obviously demonstrate, even under the high filler content of 40 wt% and without surface treatment, calcium silicate whisker can be homogeneously dispersed in polyamide, directly leading to the enhanced mechanical properties. The mechanism of higher efficiency of reinforcement is needle-like shape whisker, having access to be intercalated, and mutual affinity caused by hydrogen bonding interaction between carbonyl group in polyamide chain and hydroxyl group in whisker surface. Both aspects attach matrix with excellent stress-transfer properties. In addition, with the assistance of whisker, the nanocomposite favors an improved water absorption as well as thermal stability, which is intimately associated with physical performance. 相似文献
An extruder can be operated as a torque rheometer by setting an external control of the processing variables and adding an in-line optical detector and an on-off mechanical valve at the extruder die exit. Various operational modes can be used including constant, ramp and sinusoidal changes of the die-head pressure. With the valve closed, a fixed amount of polymer is added and the extruder put into operation, controlling the screw rotation speed via software, having a proportional/integral/derivative controller. Polymer degradation can be followed recording changes in barrel pressure and torque. After processing, the valve is opened and the molten polymer discharged under a controlled die-head pressure, manipulating again the screw rotation speed. The polymer mixture morphology can be scanned during the discharge of the melt flow by the in-line turbidimeter, showing the deformation/recovery of the second phase droplets. 相似文献
This work focuses on the study of uniaxial elongational flow and its effects on morphology and stiffness of polyamide-6 based nanocomposites prepared by melt compounding. The elongational flow characterization was realized by converging flow method and fiber spinning technique. During the haul-off tests, fibers of the neat polyamide-6 and the hybrids (at 3 and 6 wt% of silicate) were collected at different draw ratios. Mechanical properties of the produced fibers were investigated and correlated to their nanostructure through analytical techniques sensitive to different aspects of morphology, such as DSC and TEM analysis. Rheological results, obtained with a capillary rheometer, indicate that the shear viscosity decreases with the silicate loading, while the extentional viscosity increases. Moreover, the presence of the silicate in polymer matrix leads to enhancements of draw-down force and reduction of the breaking draw ratio. In hybrid fibers an enhanced degree of exfoliation of the filler was observed upon drawing. Moreover, DSC analyses suggest that the crystalline structure of the fibers is the result of two opposite effects: the presence of the silicate which stabilizes the γ form and the drawing which promotes the α crystal phase. The degree of silicate exfoliation and the amount of the different crystal phases strongly affect the tensile properties of the fibers. 相似文献
Summary: The degradation undergone by the polymers during their use and because of the thermo‐mechanical degradation undergone during the reprocessing operations provokes, among other effects, the decrease of the molecular weight. The change of the molecular architecture is responsible for the deterioration of all the properties. In order to restore the properties of post‐consumer recycled plastics, some rebuilding of the molecular structure is necessary. In this work, photo‐oxidized films for greenhouses were reprocessed in presence of additives able to react with the polyethylene in order to form branching and cross‐linking, improving the properties of these post‐consumer plastic.
Pressure as a function of time in the mini twin‐screw extruder, processing speed 70 rpm. 相似文献
Intercalated and ordered exfoliated layered silicate nanocomposites based on three different epoxy resins of different structures and functionalities were synthesized using an octadecyl ammonium modified smectite clay. Water uptake properties of series of each nanocomposite system with different organoclay concentrations were determined by gravimetric measurements over a period of time. The diffusion coefficients were determined and the effect of the absorbed water on the thermal relaxations investigated. The equilibrium water uptake of all nanocomposites was reduced compared to the neat epoxy system but the rate of water diffusion remained unaffected. Further, the thermal stability of the different nanocomposites was determined using thermogravimetric analysis. The nanocomposites showed slightly reduced thermal stability, as indicated by a slight decrease in onset of degradation, whilst the final char concentration increased for greater organoclay concentrations. 相似文献