Mechanical, thermal and morphological properties of montmorillonite filled linear low density polyethylene-toughened polylactic acid nanocomposites

Linear low density polyethylene (LLDPE) toughened polylactic acid (PLA) nanocomposites containing organophilic modified montmorillonite (MMT) were prepared by melt extrusion using a counter-rotating twin-screw extruder followed by injection molding in order to examine the mechanical, morphological and thermal properties of the nanocomposites. The mechanical properties of PLA/LLDPE nanocomposites were studied through tensile, flexural and impact tests. Scanning electron microscopy (SEM) was used to investigate the phase morphology and LLDPE particle’s size in PLA/LLDPE blends and nanocomposites. X-ray diffraction (XRD) was employed to characterize the formation of nanocomposites while the thermal properties were determined using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The dynamic mechanical properties were examined via dynamic mechanical analysis (DMA) while moisture permeability properties of the PLA/LLDPE nanocomposites were assessed through water absorption and hygrothermal aging. Subsequently, for PLA/LLPDE blends, the loadings of LLPDE were varied from 5-15 wt% and PLA/LLDPE nanocomposites with 2 phr and 4 phr loadings of MMT were prepared only for the optimum formulation (10 wt% of LLDPE). The results showed that the blending of LLDPE significantly increased the toughness but at the expense of stiffness and strength. Conversely, the incorporation of the MMT increased the stiffness, while the toughness and strength decreased. The PLA/LLDPE nanocomposites containing 2 phr of MMT and 10 wt% of LLDPE had the best balance of stiffness, strength and toughness. The impact strength results also proved that PLA nanocomposites were successfully toughened with LLDPE. XRD established that MMT were well dispersed and preferentially embedded in the PLA phase. SEM revealed that blend ratio and the presence of MMT were found to influence the morphology (e.g. LLDPE particle size and distribution) of the system. Finer particles’ size and better distribution of LLDPE has been observed in higher MMT loadings in the system. The SEM micrographs also revealed that increasing content of LLDPE has increased the particle size of LLDPE in PLA. DMA analysis discovered that the storage modulus at 30ºC increased with the presence of MMT for PLA nanocomposites. The DSC results showed that the crystallization temperature (Tc) dropped gradually with increasing content of MMT for both PLA and PLA/LLDPE nanocomposites while the glass transition (Tg) and melting temperature (Tm) remained unchanged. TGA also exhibited an increase in T10% decomposition temperature for PLA and PLA/LLDPE nanocomposites. Water absorption curves obeyed the Fick’s law with rapid moisture absorption to maximum saturation level (Mm) and the value of Mm of PLA increased with addition of LLDPE and 2 phr of MMT. Hygrothermal aging revealed that the Mm increased significantly at elevated temperatures (60ºC and 90ºC) and addition of LLDPE and MMT improved the hygrothermal stability of PLA

On the use of magnesium hydroxide towards halogen-free flame-retarded polyamide-6/polypropylene blends

Metal hydroxides have long been considered as abundant and low cost fillers towards the development of halogen-free flame-retarded polymers. In this study, magnesium hydroxide (MH) flame-retarded polyamide 6/polypropylene (PA6/PP) composites with various MH contents (20-50 wt%) were prepared and flame retardancy, thermal degradation, morphological, mechanical, thermal and thermo-mechanical characteristics were discussed. Mass loss calorimeter analysis revealed that the addition of MH provided improvements in flame retardancy through reduced heat release and mass loss rates along with delayed ignition. Limiting oxygen index and UL-94 tests also suggested enhancement in flame retardancy with increasing MH content. Substantial flame retardancy was obtained with the addition of MH at a loading level greater than 30 wt% in the resin which was explained by the formation of intact, consolidated and thick residue structures on the surface of MH filled samples. The addition of MH lowered the thermal stability of PA6/PP blends and PP particles are densely covered by MH particles adversely affecting the compatibility of blend constituents. Degree of crystallinity of blend constituents was reduced with the incorporation of MH. While the stiffness of PA6/PP/MH composites was improved, impact strength was deteriorated with increasing MH content. Due to the stiffness effect of MH particles, damping behavior of PA6 in PA6/PP/MH composites was reduced at high temperatures

Recent developments in PA6/PP nanocomposites

An overview of the recent developments in PA6/PP blend nanocomposites is presented in this paper with an emphasis on their mechanical, thermal and morphological properties. The role of organoclay as a reinforcing agent and polyethylene octene (POE) as an elastomer are discussed in detail. The organoclay increases the strength and stiffness while the POE elastomer increases the impact toughness of the nanocomposites. The effects of various parameters such as PA6/PP blend ratio, organoclay loading and the concentration of elastomer on the nanocomposites properties are also examined. The exfoliated state of organoclay platelets along with the fine particle size and uniform dispersion of POE demonstrate the nanocomposite with improved properties. These materials are attracting considerable interest in polymer research community because they exhibit substantial improvement in properties at low filler contents

Novel toughened polylactic acid nanocomposite: Mechanical, thermal and morphological properties

The objective of the study is to develop a noveltoughenedpolylacticacid (PLA) nanocomposite. The effects of linear low density polyethylene (LLDPE) and organophilic modified montmorillonite (MMT) on mechanical, thermal and morphologicalproperties of PLA were investigated. LLDPE toughened PLA nanocomposites consisting of PLA/LLDPE blends, of composition 100/0 and 90/10 with MMT content of 2 phr and 4 phr were prepared. The Young’s and flexural modulus improved with increasing content of MMT indicating that MMT is effective in increasing stiffness of LLDPE toughened PLA nanocomposite even at low content. LLDPE improved the impact strength of PLA nanocomposites with a sacrifice of tensile and flexural strength. The tensile and flexural strength also decreased with increasing content of MMT in PLA/LLDPE nanocomposites. The impact strength and elongation at break of LLDPE toughened PLA nanocomposites also declined steadily with increasing loadings of MMT. The crystallization temperature and glass transition temperature dropped gradually while the thermal stability of PLA improved with addition of MMT in PLA/LLDPE nanocomposites. The storage modulus of PLA/LLDPE nanocomposites below glass transition temperature increased with increasing content of MMT. X-ray diffraction and transmission electron microscope studies revealed that an intercalated LLDPE toughened PLA nanocomposite was successfully prepared at 2 phr MMT content

Aging of toughened polylactic acid nanocomposites: water absorption, hygrothermal degradation and soil burial analysis

The environmental aging behaviour of montmorillonite (MMT) filled polylactic acid (PLA) nanocomposites (PLA/MMT) and linear low density polyethylene (LLDPE)-toughened PLA (PLA/LLDPE ratio = 90/10) nanocomposites (PLA/LLDPE/MMT) were investigated in this study. The nanocomposites were subjected to water absorption, hygrothermal degradation and soil burial analysis. Both PLA/MMT and PLA/LLDPE/MMT nanocomposites were immersed in distilled water at three different temperatures (room temperature, 60, and 90°C) and the weight difference before and after immersion was calculated. The kinetics of water absorption for both nanocomposites followed the Fick’s second law of diffusion, where a linear relationship exists between the initial moisture absorption at any time t and t 1/2 (the square root of time), followed by a horizontal plateau (saturation). The equilibrium moisture content (M m ) and diffusion coefficient (D) of PLA nanocomposites increased with the addition of MMT (2 phr) and LLDPE. However, the D values of both nanocomposites decreased by increasing MMT (4 phr). The Mm for PLA/MMT and PLA/LLDPE/MMT nanocomposites increased by increasing immersion temperature (60°C) and prolonged immersion resulted in hygrothermal degradation of both nanocomposites. The hygrothermal degradation studies showed that PLA degrades much faster at 90°C as compared to 60°C in both the nanocomposites. The addition of MMT and LLDPE improved the hygrothermal stability of PLA in both nanocomposites. Soil burial test revealed deterioration of impact strength in all samples while the rate of biodegradation was retarded in the presence of MMT and LLDPE

Epoxidized natural rubber toughened polylactic acid/talc composites: mechanical, thermal, and morphological properties

The aim of present study is to develop a toughened polylactic acid/talc composite. Talc and epoxidized natural rubber (ENR-50) were compounded with polylactic acid using counter-rotating twin-screw extruder followed by preparation of samples through injection molding. The effect of silane-treated talc and epoxidized natural rubber on mechanical, thermal, and morphological properties of polylactic acid was investigated. The Young′s and flexural modulus of polylactic acid improved while the impact strength values dropped with increasing talc content (20–30 wt%) indicating that talc increased the stiffness of polylactic acid with a sacrifice in toughness. Subsequently, the blending of epoxidized natural rubber (20 wt%) to polylactic acid/talc (30 wt%) revealed that the impact strength of polylactic acid/talc composites improved 448% with considerable drop in Young’s and flexural modulus. Polylactic acid/talc/epoxidized natural rubber composite contains 60% polylactic acid, 30 wt% talc, and 10 wt% ENR display optimum stiffness and impact strength. Scanning electron micrographs demonstrates that talc agglomerates at higher loadings. Thermogravimetric anlaysis indicated that thermal stability of polylactic acid/talc composite was reduced by the addition of epoxidized natural rubber due to increasing talc agglomeration

Bionanocomposites of regenerated cellulose reinforced with halloysite nanoclay and Graphene nanoplatelets: characterizations and properties

In recent years, the development of environmentally friendly materials obtained from renewable resources has attracted immense interest due to the new sustainable development policies. Cellulose is a readily available, naturally occurring biodegradable, and biocompatible linear polysaccharide. Recently, room temperature ionic liquids have been used as solvents to produce regenerated cellulose (RC) due to their attractive properties such as good chemical and thermal stability, low flammability, low melting point, and ease of recycling. Polymer/ nanofiller nanocomposites are believed to have strong potential to widen polymer applications due to enhanced performance. It is also widely accepted that the incorporation of small amount of nanofiller (less than 5 wt%) into bio-based matrixes to produce nano-biocomposite materials with enhanced mechanical, permeability, and thermal properties. The tubular silica-based naturally occurring nanofiller, halloysite nanotubes (HNT), has been investigated due to its high surface area, unique geometry, and its potential to make the hydrogen bonding with polymers to disperse well in the matrix. Graphene nanoplatelets (GNP) have also attracted enormous attention among polymer engineers over the last few years due to its unique electrical, thermal, and mechanical properties. Single layer twodimensional GNP sheet is considered as the strongest material along with the high surface area and aspect ratio. The chapter aims to highlight the effect of the addition of two different types of nanofillers such as HNT and GNP to produce RC nanocomposites on selected properties

Preparation and characterization of organically modified montmorillonite-filled high density polyethylene/hydroxyapatite nanocomposites for biomedical applications

The study investigated the introduction of organically modified montmorillonite (MMT) in high density polyethylene/hydroxyapatite (HDPE/HA) composites for biomedical applications. The addition of HA and MMT increased the strength and stiffness of HDPE/HA composites with deterioration in impact strength and elongation at break values. XRD and TEM analysis provided evidence of exfoliated MMT layers in HDPE/HA composites and the MMT layers remained exfoliated even with further addition of HA. Simulated body fluid (SBF) analysis revealed that the size of apatite layer increased with increasing immersion time and the formation of apatite layers on the surface of composites indicates excellent biocompatibility properties

Mechanical, thermal, and morphological properties of polylactic acid/linear low density polyethylene blends

Melt blending of polylactic acid (PLA) and linear low density polyethylene (LLDPE) was performed to investigate the effects of LLDPE loadings on the morphology, mechanical and thermal properties of PLA/LLDPE blends. LLDPE was blended with PLA from 5—15 wt% and prepared by counterrotating twin-screw extruder followed by injection molding into test samples. The mechanical properties of the blends were assessed through tensile, flexural and impact testings while thermal properties were analyzed using differential scanning calorimetry (DSC) and thermogravimetric analysis. Scanning electron microscope was used to study the dispersion and particle size of LLDPE in PLA matrix. The impact strength of PLA improved by 53% with addition of 10 wt% LLDPE. However, the tensile modulus and strength, and elongation at break of PLA/LLDPE blends decreased with increasing weight ratio of LLDPE. Similarly, flexural modulus and strength also dropped with addition of LLDPE. DSC results showed that glass transition temperature (Tg) and crystallinity (X c) of PLA increased with blending of LLDPE. The LLDPE particles size was seen to increase with increasing loadings of LLDPE which explains the unexpected decrease of impact strength after 10 wt%

Enhanced flame retardancy, thermal and mechanical properties of hybrid magnesium hydroxide/montmorillonite reinforced polyamide 6/polypropylene nanocomposites

In this study, the effects of hybrid magnesium hydroxide/montmorillonite (MH/MMT) on the flame retardancy, thermal, mechanical, morphological and thermo-mechanical properties of polyamide 6/polypropylene (PA6/PP) nanocomposites prepared by melt blending technique were investigated. The partial replacement of MH with MMT (2 and 4 wt%) was done at total filler content of 30 wt% and maleated polypropylene was used as compatibilizer. Mass loss calorimeter analysis revealed that the peak heat release rate and total heat evolved values reduced in the presence of MMT due to the formation of the protective surface and insulation layer by MMT within the MgO layer formed on the surface upon combustion. The char residue also strengthened by migration of MMT layers to the surface of char. The thermal stability and flame retardancy of PA6/PP/MH/MMT nanocomposites improved with increasing MMT content. The MMT layers were well dispersed in the nanocomposites. The stiffness and toughness of PA6/PP/MH nanocomposites increased while the strength maintained with incorporation of MMT. The degree of crystallinity of both PA6 and PP increased with the addition of MMT while the melting point remained unaltered. The synergistic combination of MH and MMT has indeed maintained the mechanical properties of nanocomposites while further improving the flame retardancy