Micro-mechanisms of deformation in polyethylene/clay micro- and nanocomposites

Express Polymer Letters, 2007

In this work we report on the microstructural and the mechanical characteristics of high density polyethylene (HDPE)-clay nanocomposites, with particular attention to the creep behaviour. The samples were prepared through melt compounding, using two high-density polyethylenes with different melt flow rate (MFR), two different organo-modified clays, and changing the relative amount of a polyethylene grafted with maleic anhydride (PEgMA) compatibilizer. The intercalation process is more effective as the matrix melt viscosity decreases (higher MFR), while the clay interlamellar spacing increases as the compatibilizer amount increases. The relative stiffness of the nanocomposites increases with the addition of clay, with a limited enhancement of the relative yield stress. The better intercalation obtained by the addition of the compatibilizer is not accompanied by a concurrent improvement of the tensile mechanical properties. The creep resistance is enhanced by the introduction of clay, with an appreciable dependence on both the polyethylene and the clay type.

Composites Science and Technology, 2004

A multi-scale model to predict the moduli of polymer-clay nanocomposites (PCNs) is presented. The model uses a locally orthotropic finite element model to develop constitutive equations to describe the stiffness properties of a group of aligned clay flakes with surrounding interphase suspended in a polymer matrix. The model then assembles a number of flake groups with varied orientations to predict the actual moduli seen in PCNs. The model is in good agreement with an experimentally obtained tensile modulus found in the literature. The model was also applied to estimate the relative influence of constituent properties and microstructural parameters on the anisotropic tensile modulus of the PCN.

Composites Science and Technology, 2009

Polymer nanocomposites offer the potential of enhanced properties such as increased modulus and barrier properties to the end user. Much work has been carried out on the effects of extrusion conditions on melt processed nanocomposites but very little research has been conducted on the use of polymer nanocomposites in semi-solid forming processes such as thermoforming and injection blow molding. These processes are used to make much of today's packaging, and any improvements in performance such as possible lightweighting due to increased modulus would bring significant benefits both economically and environmentally. The work described here looks at the biaxial deformation of polypropylene-clay nanocomposites under industrial forming conditions in order to determine if the presence of clay affects processability, structure and mechanical properties of the stretched material. Melt compounded polypropylene/clay composites in sheet form were biaxially stretched at a variety of processing conditions to examine the effect of high temperature, high strain and high strain rate processing on sheet structure and properties.

Proceedings of First Conference for Engineering Sciences and Technology: Vol. 2

This research work focuses on the effect of Libyan Kaolin clay particle size on the reheological, surface and mechanical properties of high density polyethylene (HDPE)/clay nanocomposites. Three polymer clay nanocomposites (PCNs) using 2 wt.% clay with different particle size (< 75, 75-150 and 150-300 μm) and 2 wt.% polyethylene grafted maleic anhydride (PE-g-MA) were prepared by melt processing method. The rheological (viscosity and melt flow rate), surface (wettability/hydrophilicity), and mechanical properties (tensile strength, elongation at break, Young's modulus, hardness and impact strength) were investigated. The obtained properties of PCNs were compared with HDPE. A better enhancement in the rheological properties properties was observed when clay particle size of < 75 µm was used. It was exhibited lower viscosity and higher MFR value, which provide better processing properties in comparison to HDPE and other PCNs. PCN with clay particle size of (75-150 µm) had more wettability and/or hydrophilicity than HDPE and other PCNs. Mechanical properties results showed significant improvement only in the impact properties as compared to HDPE. In short, PCN made with Libyan kaolin clay with particle size 75-150 μm appears to has comparatively better overall properties in comparison to other PCNs.

Polymer Testing, 2017

The effect of nanoclay fraction on the linear and non-linear tensile properties of a polyethylene/polyamide 12 blend with droplet morphology was investigated. All ternary blends were prepared at a fixed polyamide (PA) weight fraction of 20%, and at clay volume fractions varying from 0.5 to 2.5% relative to PA. Scanning electron microscopy and transmission electron microscopy were used to characterize the morphology of the blends and the clay interphase structure. The nanoclay content was shown to strongly influence both linear and non-linear tensile properties. Young's modulus, elongation at yield, yield strength, tensile strength and elongation at break as a function of clay fraction were studied and discussed in terms of morphological changes and strain-induced structural reorganization of the clay interphase.

Journal of Solid Mechanics, 2018

This paper presents the preparation and mechanical properties of compatibilized compositionally graded Polyethylene/ low density polyethylene (LDPE)/ modified montmorillonite (MMT) nanocomposites prepared by solution and melt mixing techniques. Use of polyethylene glycol as compatibilizer improves compatibility of modified montmorillonite and low density polyethylene. Comparisons between two techniques show that the melt mixing technique is the preferred method for preparation the Polyethylene/Clay nanocomposites for uniform and compositionally graded distributions. It is observed, the addition of Nano clay improves the mechanical properties like tensile strength. Also, it is noticed the mechanical properties of compositionally graded Polyethylene/Clay nanocomposites are improved rather than the uniform distribution of Polyethylene/Clay nanocomposites. The morphology of nanocomposites cross section samples is studied by Scanning Electron Microscopy (SEM) and finally the comparison are made between two techniques and then between compositionally graded polyethylene/clay nanocomposites with uniform ones. Its show that when the compatibilizer was added for melt mixing technique, the density and the size of the aggregates decreased, which indicates that the dispersion of nano clays within the polymer matrix is much better.

Jurnal Sains dan Teknologi Reaksi, 2016

This study investigates the effect of filler content on mechanical properties for polypropylene. There are synthesis clay and un-synthesis clay used as filler content. Different ratio of clay was d in polypropylene to study which ratio have a better mechanical properties. The tensile test was carried out using INSTRON5565 and the maximum stress, strain, and modulus of elasticity observed. Results of the study showed that polypropylene/clay nanocomposite has a higher maximum stress compare to pure polypropylene and un-synthesis clay have a lowest. Besides that modulus of elasticity of specimen calculated and finds that it increased with increment filler content and strain did not affect by filler. The conclusion is synthesis clay filled into polypropylene will having a better material.Keywords: Nanocomposite, polypropylene, synthesis clay.

Journal of Applied Polymer Science, 2009

Copolypropylene/organoclay nanocomposites are prepared by melt intercalation method in this research. Two different routes for addition of compatibilizer are examined, i.e. addition in the twin-screw extruder along with the polymer and the clay powder simultaneously and premixing the compatibilizer with the reinforcement in a batch mixer before addition to the polypropylene (PP) matrix. Morphology, tensile and impact properties and deformation mechanisms of the samples made via two procedures are studied and compared with those of the noncompatibilized system. To study the structure of nanocomposites, x-ray diffraction and transmission electron microscopy techniques are utilized. The deformation mechanisms of different samples are examined via reflected and transmitted optical microscopy. The results reveal that introduction of compatibilizer and also the procedure in which the compatibilizer is added to the compound, affect structure and mechanical properties of nanocomposite. The elastic modulus of PP-clay nanocomposite has increased 11.5% with incorporation of compatibilizer. Also, introduction of organoclay without compatibilizer facilitates crazing at the notch tip of PP in 3PB testing. Incorporation of compatibilizer, however, makes difficulties in initiation and growth of crazes at the notch tip. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

IOP Conference Series: Materials Science and Engineering, 2018

A comparative study on effect of internal mixer on high density Polyethylene (HDPE)/clay nanocomposites preparation was done. Effect of temperature, rotor rotation (rpm), and mixing time, as well as rotor type (Roller and Banbury) on mechanical properties and morphology of HDPE/clay nanocomposites were studied using Box-Behnken experimental design. The model was developed according to secant modulus and confirmed to morphology analysis using Transmission Electron Microscopy (TEM). The finding suggests that there is different mechanisms occurred in each rotor to improve the mechanical properties. The mechanism in Roller is medium shear and medium diffusion, while Banbury is high shear and low diffusion. The difference in mechanism to disperse the clay particles attribute to the different optimum processing conditions in each rotor. The settings for roller samples are predicted around mid temperature, mid speed, and mid mixing time. There is no optimum setting for Banbury within the processing boundaries. The best settings for Banbury are at low, high, low settings. The morphology results showed a hybrid composite structure, with some exfoliations and some intercalations. There was a correlation between better mechanical properties and morphology with more exfoliation and thinner intercalated particles.

Polymer, 2007

High density polyethylene (HDPE)/organoclay nanocomposites of varying concentrations of clay were prepared by a single screw compounding extruder with the attached ultrasound die operating at various amplitudes. The die pressure and power consumption due to ultrasound were measured at different feed rates of nanocomposites of various clay concentrations. The structure and morphology of nanocomposites were studied by X-ray diffraction (XRD), transmission electron microscopy (TEM) and infrared spectroscopy. It was found that ultrasonic treatment enhanced the intercalation of HDPE into lattice layers of clay by increasing d-spacing up to 50%. Mechanical and rheological properties of these nanocomposites were investigated as a function of clay concentration and ultrasonic amplitude. Complex viscosity, storage and loss moduli of nanocomposites were increased after ultrasonic treatment. Mechanical properties such as the elongation at break, yield stress, toughness and impact strength of ultrasonically treated nanocomposites increased in comparison with the untreated nanocomposites. A reduction in oxygen permeability of nanocomposites was observed after ultrasonic treatment at an amplitude of 10 mm with the highest reduction by 20% at 2.5% clay concentration and a residence time of 21 s. This reduction in permeability was achieved even though results indicate that the crystallinity of ultrasonically treated nanocomposites was reduced.