Mechanical, Thermal and Rheological Properties of Polyethylene-Based Composites Filled with Micrometric Aluminum Powder.
ABSTRACT: Investigations related to polymer/metal composites are often limited to the analysis of the electrical and thermal conductivity of the materials. The presented study aims to analyze the impact of aluminum (Al) filler content (from 1 to 20 wt%) on the rarely investigated properties of composites based on the high-density polyethylene (HDPE) matrix. The crystalline structure, rheological (melt flow index and oscillatory rheometry), thermal (differential scanning calorimetry), as well as static (tensile tests, hardness, rebound resilience) and dynamic (dynamical mechanical analysis) mechanical properties of composites were investigated. The incorporation of 1 and 2 wt% of aluminum filler resulted in small enhancements of mechanical properties, while loadings of 5 and 10 wt% provided materials with a similar performance to neat HDPE. Such results were supported by the lack of disturbances in the rheological behavior of composites. The presented results indicate that a significant content of aluminum filler may be introduced into the HDPE matrix without additional pre-treatment and does not cause the deterioration of composites' performance, which should be considered beneficial when engineering PE/metal composites.
Project description:The effect of individual and combined talc and glass fibers (GFs) on mechanical and thermal expansion performance of the filled high density polyethylene (HDPE) composites was studied. Several published models were adapted to fit the measured tensile modulus and strength of various composite systems. It was shown that the use of silane-modified GFs had a much larger effect in improving mechanical properties and in reducing linear coefficient of thermal expansion (LCTE) values of filled composites, compared with the use of un-modified talc particles due to enhanced bonding to the matrix, larger aspect ratio, and fiber alignment for GFs. Mechanical properties and LCTE values of composites with combined talc and GF fillers varied with talc and GF ratio at a given total filler loading level. The use of a larger portion of GFs in the mix can lead to better composite performance, while the use of talc can help lower the composite costs and increase its recyclability. The use of 30 wt % combined filler seems necessary to control LCTE values of filled HDPE in the data value range generally reported for commercial wood plastic composites. Tensile modulus for talc-filled composite can be predicted with rule of mixture, while a PPA-based model can be used to predict the modulus and strength of GF-filled composites.
Project description:Hybrid basalt fiber (BF) and Talc filled high density polyethylene (HDPE) and co-extruded wood-plastic composites (WPCs) with different BF/Talc/HDPE composition levels in the shell were prepared and their mechanical, morphological and thermal properties were characterized. Incorporating BFs into the HDPE-Talc composite substantially enhanced the thermal expansion property, flexural, tensile and dynamic modulus without causing a significant decrease in the tensile and impact strength of the composites. Strain energy estimation suggested positive and better interfacial interactions of HDPE with BFs than that with talc. The co-extruded structure design improved the mechanical properties of WPC due to the protective shell layer. The composite flexural and impact strength properties increased, and the thermal expansion decreased as BF content increased in the hybrid BF/Talc filled shells. The cone calorimetry data demonstrated that flame resistance of co-extruded WPCs was improved with the use of combined fillers in the shell layer, especially with increased loading of BFs. The combined shell filler system with BFs and Talc could offer a balance between cost and performance for co-extruded WPCs.
Project description:An experimental study of high-density polyethylene (HDPE) composites filled with talc (0-15 wt.%) was carried out to investigate the rheological properties. The apparent melt viscosity, melt density, and die-swell ratio (B) of the composites were measured at constant shear stress and constant shear rate by using a melt flow indexer and capillary rheometer. The experimental conditions were set to a temperature range from 190 to 220 °C for both apparatuses whereas a load range from 5 to 12.16 kg was selected for melt flow indexer and shear rate range from 1 to 10000 s-1 for capillary rheometer. The initial study showed that the talc particulates did not influence the melt viscosity compared with the neat HDPE but decreased the elasticity of the polymer system. The HDPE/talc systems obeyed power-law model in shear stress-shear rate variations and were shear thinning, meanwhile, the die-swell increased with an increased wall shear rate and shear stress. The melt density of the composites increased linearly with an increase of the filler weight fraction and decreased with the increase of the testing temperature. The talc-HDPE composites showed compressible in the molten state.
Project description:Polymer composites with excellent thermal conductivity and superior mechanical strength are in high demand in the electrical engineering systems. However, achieving superior thermal conductivity and mechanical properties simultaneously at high loading of fillers will still be a challenging issue. In this work, a facile method was proposed to prepare the epoxy composite with carbon fibers (CFs) and alumina (Al2O3). This CF and Al2O3 hybrid structure can effectively reduce the interfacial thermal resistance between the matrix and the CFs. The thermal conductivity of epoxy composite with 6.4 wt % CFs and 74 wt % Al2O3 hybrid filler reaches 3.84 W/(m K), which is increasing by 2096% compared with that of pure epoxy. Meanwhile, the epoxy composite still retains outstanding thermal stability and mechanical performance at high filler loading. A cost-effective avenue to prepare highly thermally conductive and superior mechanical properties of polymer-based composites may enable some prospective application in advanced thermal management.
Project description:A series of composites was prepared from a diglycidyl ether of bisphenol A (DGEBA) with different graphene filler contents to improve their mechanical performance and thermal stability. Graphene oxide (GO) and GO modified with hexamethylene tetraamine (HMTA) were selected as reinforcing agents. As a latent cationic initiator and curing agent, N-benzylepyrizinium hexafluoroantimonate (N-BPH) was used. The effect of fillers and their contents on the mechanical properties and thermal stability of the composites were studied. Fracture toughness improved by 23% and 40%, and fracture energy was enhanced by 1.94- and 2.27-fold, for the composites containing 0.04 wt.% GO and HMTA-GO, respectively. The gradual increase in fracture toughness at higher filler contents was attributed to both crack deflection and pinning mechanisms. Maximum thermal stability in the composites was achieved by using up to 0.1 wt.% graphene fillers.
Project description:Leather waste (BF) and high-density polyethylene (HDPE) were compounded in a lab scale internal mixer and processed by means of injection molding. In this study, leather waste and HDPE composites were characterized by instrumental techniques such as differential scanning calorimetry (DSC), thermo-gravimetric Analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). Physical integrity of composites against chemical exposure and chromium-leaching properties of the composites were also investigated. This study shows that the incorporation of 30% leather waste fiber into HDPE composites decreases the thermal conductivity of the composite samples by 17% in comparison to that of neat HDPE samples. Composites showed no thermal degradation during processing cycle. Strong interfacial bonding between leather waste and polymer results in comparable low-leachate levels to maximum allowed concentration for nonhazardous waste, and good chemical resistance properties. The BF/HDPE composites could be a promising low-cost alternative in industrial application areas of HDPE, where high-mechanical strength and low-thermal conductivity is required.
Project description:This works focuses on the development of environmentally friendly composites with a partially biobased polyamide 610 (PA610), containing 63% biobased content, and a natural inorganic filler at the nanoscale, namely, halloysite nanotubes (HNTs). PA610 composites containing 10, 20, and 30 wt% HNTs were obtained by melt extrusion in a twin screw co-rotating extruder. The resulting composites were injection-molded for further characterization. The obtained materials were characterized to obtain reliable data about their mechanical, thermal, and morphological properties. The effect of the HNTs wt% on these properties was evaluated. From a mechanical standpoint, the addition of 30 wt% HNTs gave an increase in tensile modulus of twice the initial value, thus verifying how this type of natural load provides increased stiffness on injection molded parts. The materials prepared with HNTs slightly improved the thermal stability, while a noticeable improvement on thermomechanical resistance over a wide temperature range was observed with increasing HNTs content. The obtained results indicate that high biobased content composites can be obtained with an engineering thermoplastic, i.e., PA610, and a natural inorganic nanotube-shaped filler, i.e., HNTs, with balanced mechanical properties and attractive behavior against high temperature.
Project description:Polypropylene composites with different filler contents were prepared by creating a masterbatch containing 3 wt%. filler. A variety of silanol groups were used to synthetized three compounds in different media trough a sol-gel process with acetic acid, formic acid and ammonium hydroxide as catalysts. Besides, four different nanotubular fillers were also used to analyze their behavior and compare it with the effect caused by the silanol groups. These tubular structures comprise: unmodified halloysite, carbon nanotubes and functionalized halloysite and carbon nanotubes. Morphological characterization in SEM and STEM/TEM showed dispersion in the polypropylene matrix. According to TGA and DSC measurements thermal behavior remain similar for all the composites. Mechanical test in tension demonstrate that modulus of the composites increases for all samples with a major impact for materials containing silanol groups synthetized in formic acid. Rheological measurements show a significantly increment in viscosity for samples containing unmodified and modified carbon nanotubes. No difference was found for samples containing silanol groups and halloysite when compared to neat polypropylene. Finally, the oxygen transmission rate increased for all samples showing high barrier properties only for samples containing natural and functionalized halloysite nanotubes.
Project description:This paper presents the effects of accelerated weathering on the properties of polylactide (PLA) composites filled with linseed cake. The particle-shaped waste filler with different linseed oil content (0.9-39.8 wt %) was incorporated with constant amount of 10 wt % to a polymeric matrix and subjected to accelerated weathering tests with different exposition times. The structure of the composites, their mechanical, thermal, and thermo-mechanical properties were evaluated by means of scanning electron microscopy, tensile test, dynamic mechanical thermal analysis, and differential scanning calorimetry prior to and after weathering. The results of the measurements were analyzed in reference to the amount of crude oil contained in the filler. The behavior of the multiphase composite during weathering was described. It was found that the oil-rich samples during the first stage of the process showed increased resistance to hydrolytic degradation due to their relatively high crystallinity. The presence of water and elevated temperatures caused swelling of the filler and cracking of the polymeric matrix. Those discontinuities enabled the plasticizing oil to be rinsed out of the composite and thus water penetrated into the samples. As a result, the PLA-based composites containing oil-rich linseed cake were found to be more vulnerable to hydrolytic degradation in a longer time.
Project description:Thermoplastic polymer-filler composites are excellent materials for bone tissue engineering (TE) scaffolds, combining the functionality of fillers with suitable load-bearing ability, biodegradability, and additive manufacturing (AM) compatibility of the polymer. Two key determinants of their utility are their rheological behavior in the molten state, determining AM processability and their mechanical load-bearing properties. We report here the characterization of both these physical properties for four bone TE relevant composite formulations with poly(ethylene oxide terephthalate)/poly(butylene terephthalate (PEOT/PBT) as a base polymer, which is often used to fabricate TE scaffolds. The fillers used were reduced graphene oxide (rGO), hydroxyapatite (HA), gentamicin intercalated in zirconium phosphate (ZrP-GTM) and ciprofloxacin intercalated in MgAl layered double hydroxide (MgAl-CFX). The rheological assessment showed that generally the viscous behavior dominated the elastic behavior (<i>G</i>″ > <i>G</i>') for the studied composites, at empirically determined extrusion temperatures. Coupled rheological-thermal characterization of ZrP-GTM and HA composites showed that the fillers increased the solidification temperatures of the polymer melts during cooling. Both these findings have implications for the required extrusion temperatures and bonding between layers. Mechanical tests showed that the fillers generally not only made the polymer stiffer but more brittle in proportion to the filler fractions. Furthermore, the elastic moduli of scaffolds did not directly correlate with the corresponding bulk material properties, implying composite-specific AM processing effects on the mechanical properties. Finally, we show computational models to predict multimaterial scaffold elastic moduli using measured single material scaffold and bulk moduli. The reported characterizations are essential for assessing the AM processability and ultimately the suitability of the manufactured scaffolds for the envisioned bone regeneration application.