56 research outputs found
A review on rheological approaches as a perfect tool to monitor thermal degradation of biodegradable polymers
Get PDFThis review provides an in-depth analysis of the thermal degradation of biodegradable polymers through rheological methods. Focusing on key techniques such as time sweep tests, frequency sweep tests, and nonlinear rheological analyses gained at higher shear tests, the review highlights how these approaches offer critical insights into polymer stability and degradation kinetics. It entails an understanding of how molecular weight reduction, a common degradation mechanism, significantly impacts the performance of biodegradable polymers, and how the use of appropriate fillers can enhance thermal stability by mitigating chain scission. The review also discusses the application of the Arrhenius equation in modelling thermal degradation, helping predict degradation rates and optimize processing conditions. Time sweep tests are particularly emphasized for their ability to monitor polymer stability under various environmental conditions, while frequency sweep tests provide insights into the effects of processing/thermal history on material degradation. Tests at higher shear rates, which simulate real-world processing conditions such as extrusion and injection moulding, are explored for their role in understanding how processing-induced shear forces accelerate polymer degradation. Various biodegradable polymers are considered in this review, with polylactic acid (PLA) being the dominant polymer studied across most research, providing a clear picture of its degradation behaviour and strategies for enhancing its thermal stability. Therefore, it is expected that this review will be a comprehensive guide for researchers and engineers looking to optimize the thermal stability and performance of biodegradable polymers in various industrial applications
Unveiling the Significance of Graphene Nanoplatelet (GNP) Localization in Tuning the Performance of PP/HDPE Blends
Get PDFHigh-density polyethylene (HDPE) and polypropylene (PP) blends are widely used in industries requiring mechanically durable materials, yet the impact of processing parameters on blend performance remains underexplored. This study investigates the influence of blending sequence and screw speed on the properties of blends of HDPE and PP filled with 1.25 wt.% graphene nanoplatelets (GNPs). Changes in crystallization behaviour, tensile strength, and viscoelastic responses with blending sequence are studied. The addition of GNP increases the crystallization temperature (Tc) of PP in the PE/PP blend by 4 °C when GNP is pre-mixed with PE to form (PE+GNP)/PP blends. In contrast, when GNP is pre-mixed with PP to create (PP+GNP)/PE blends, the Tc of PP rises by approximately 11 °C, from 124 °C for the neat PE/PP blend to 135 °C. On the other hand, the Tc of PE remains unchanged regardless of the blending sequence. XRD patterns reveal the impact of blending regime on crystallinity, with GNP alignment affecting peak intensities confirming the more efficient interaction of GNPs with PP when premixed before blending with PE, (PP+GNP)/PE. Tensile moduli are less sensitive to the changes in processing, e.g., screw speed and blending sequence. In contrast, elongation at break and tensile toughness show distinct variations. The elongation at the break of the (PP+GNP)/PE blend decreases by 30% on increasing screw speed from 50 to 200 rpm. Moreover, the elongation at the break of (PE+GNP)/PP prepared at 100 rpm is ~40% higher than that of the (PP+GNP)/PE. (PE+GNP)/PP displays a âquasi-co-continuousâ morphology linked to its higher elastic modulus GâČ compared to that of the (PP+GNP)/PE blend. This study highlights the importance and correlation between processing and blend properties, offering insights into fine-tuning polymer composite formulation for optimal performance
Effective and fast-screening route to evaluate dynamic elastomer-filler network reversibility for sustainable rubber composite design
Get PDF.The introduction of self-healing and reprocessability into conventional vulcanized rubbers has been recognized as a promising strategy to promote elastomer circularity. However, the reversibility and recovery of cross-linking polymer networks have often been assessed by static mechanical testing, which highly limits the understanding of the underlying microscale mechanisms. In this work, we investigated the network recovery of natural rubber (NR)/carbon black (CB) nanocomposites using Fourier transform (FT) rheology coupled with large amplitude oscillation shear (LAOS) technology across linear and nonlinear regimes (0.01â500%). The self-healing process of the rubber composite networks was monitored by using a programmed timeâtemperature oscillation shear measurement. The role of CB particle size in the filler network recovery was also discussed from the perspective of strain-induced crystallization of NR. Coupling FT-rheology and LAOS analysis, two distinct nonlinear enhancement behaviors beyond the linear viscoelastic regime were detected in the rubber nanocomposites, which were ascribed to the filler network disruption followed by the polymer network deformation. The relationship of the nonlinearity parameter I3/1 as a function of strain amplitude was selected to quantify the nonlinear rheological responses, where the role of the filler and polymer on the network recovery can therefore be differentiated. This work provides an efficient method to evaluate the self-healing and reprocessability of cross-linked rubbers and offers a fast-screen route for formulation development and sustainable rubber composite design
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Effective and Fast-Screening Route to Evaluate Dynamic Elastomer-Filler Network Reversibility for Sustainable Rubber Composite Design
Get PDFThe introduction of self-healing and reprocessability into conventional vulcanized rubbers has been recognized as a promising strategy to promote elastomer circularity. However, the reversibility and recovery of cross-linking polymer networks have often been assessed by static mechanical testing, which highly limits the understanding of the underlying microscale mechanisms. In this work, we investigated the network recovery of natural rubber (NR)/carbon black (CB) nanocomposites using Fourier transform (FT) rheology coupled with large amplitude oscillation shear (LAOS) technology across linear and nonlinear regimes (0.01â500%). The self-healing process of the rubber composite networks was monitored by using a programmed timeâtemperature oscillation shear measurement. The role of CB particle size in the filler network recovery was also discussed from the perspective of strain-induced crystallization of NR. Coupling FT-rheology and LAOS analysis, two distinct nonlinear enhancement behaviors beyond the linear viscoelastic regime were detected in the rubber nanocomposites, which were ascribed to the filler network disruption followed by the polymer network deformation. The relationship of the nonlinearity parameter I3/1 as a function of strain amplitude was selected to quantify the nonlinear rheological responses, where the role of the filler and polymer on the network recovery can therefore be differentiated. This work provides an efficient method to evaluate the self-healing and reprocessability of cross-linked rubbers and offers a fast-screen route for formulation development and sustainable rubber composite design
Properties of polylactic aicd/polycaprolactone/montmorillonite (PLA/PCL/MMT) nanocomposites
No full textPolylactid acid/Polycaprolactone (PLA/PCL) nanocomosites consisting of organically modified montmorillonite (organoclay) toughened with Metallocene catalysed Linear Low Density Polyethylene (mLLDPE) was prepared PLA/PLC of composition 70/30 with fixed mLLDPE content of 10 phr while MMT in 1, 2, 4 phr was produced. Correspond toughened nanocomposites were prepared by using a twin screw extruder then injected into typical speciments using an injection molding machine. The effects of mLLDPE and MMT on mechanical, thermal and thermomechanical properties of the PLA/PCL blend were investigated. The mechanical properties of the nanocomposites were studied through tensile, flexural and impact test. The thermal properties were characterized by using differential scanning calorimeter (DSC) and thermogravimetry analysis (TGA). The dynamic mechanical analysis (DMA) was used to investigate the effects of dynamic forces at various temperatures. mLLDPE toughened nanocomposites showed relatively lower tensile strength and flexural modulus compared to PLA/PCL nanocomposites and it was concluded from mechanical test that MMT increased tensile strength and flexural modulus of all nanocomposites at lower contents. On the other hand, impact strength and elongation at break of the mLLDPE toughened nanocomposites was higher than that of PLA/PCL nanocomposites and MMT loadings exhibited a reductive effect on impact strength of nanocomposites. The crystallization temperature and melting temperature of the nanocomposites did not change siginificantly while the thermal stability of the nanocomposites improved with incorporation of MMT. Storage modulus of nanocomposites below glass transition temperature increased with increasing MMT content
Effect of organoclay on non-linear rheological properties of poly(lactic acid)/poly(caprolactone) blends
No full textThe nonlinear viscoelastic properties of PLA/PCL blends with and without clay (montmorillonite, MMT) under large amplitude oscillatory shear (LAOS) flow were investigated. The GâČ and Gâł as a function of strain amplitude, Lissajous plots and FT-rheology methods were used to interpret nonlinear behavior of PLA/PCL blends with and without MMT. Additionally, scanning electron microscopy (SEM) images of PLA/PCL with MMT blends were taken to investigate the effects of clay on the internal structure of the PLA/PCL blends. A relationship between morphological changes and linear and nonlinear rheological properties was observed. SEM image analysis revealed that clay acted as a compatibilizer and then reduced the size of droplets in the PCL domain of the PLA matrix. As a result, nonlinear properties sensitively reflect morphological changes with increasing MMT amount. The nonlinear rheological properties of PLA/PCL/MMT/metallocene-LLDPE (mLLDPE) were also investigated when mLLDPE was used as an impact modifier to improve mechanical properties, and the nonlinear rheological properties of PLA/PCL/MMT and PLA/PCL/MMT/mLLDPE were also compared
Tuning the Conductivity of Nanocomposites through Nanoparticle Migration and Interface Crossing in Immiscible Polymer Blends: A Review on Fundamental Understanding
No full textThis article critically reviews the detailed fundamental understanding of the influence of conductive nanoparticle migration on the localization, and hence, electrical conductivity of immiscible polymer blend nanocomposites. Three types of conductive nanoparticles, namely, spherical, tubular, and platelet, are discussed with respect to their migration and electrical conductivity of obtained nanocomposites. A complete migration process consists of bulk migration within one component, contact with the interface, and penetration to the other component. During processing, the wetting coefficient parameter is the main thermodynamically controlling factor for nanoparticle localization. However, kinetic effects, such as mixing sequence and intensity, viscosity ratio, size and shape of the nanoparticles, and mixing time, can play a substantial role in determining the final locations of nanoparticles. Moreover, the rate of migration varies with the surface chemistry of the nanoparticles. It has been reported that nanoparticles in a more viscous phase move slower compared with a low viscous phase. Furthermore, nanoparticles having high aspect ratios and surface polarities compatible with the other component migrating faster. It is established that immiscible polymer blend nanocomposites with a ?double percolation? structure having higher conductivity with nanoparticles are localized at the interface of the co-continuous blends
Nanostructured Immiscible Polymer Blends: Migration and Interface
No full textNanostructured Immiscible Polymer Blends: Migration and Interface covers a wide range of nanoparticle types, emphasizing the mechanisms and parameters involved in the migration of nanofillers inside immiscible polymer blends. This book explores the influence of nanoparticle migration on the localization, and hence, morphology development, electrical conductivity, and met-rheological properties of blended composite materials. As the influence of solid particles, ranging in size from several hundred nanometers to a few microns in immiscible polymer blends has been extensively studied for use as compatibilizers, morphology stabilizers, and reinforcement agents, this book is a timely resource
Influence of Nanoclay Localization on StructureâProperty Relationships of Polylactide-Based Biodegradable Blend Nanocomposites
No full textThis article highlights the recent research achievements regarding the development of nanoclay-containing biodegradable composites of polylactide (PLA)-based immiscible blends. The structure?property relationships of particular blends, namely, PLA/poly(Δ-caprolactone), PLA/poly(butylene succinate), and PLA/poly[(butylene succinate)-adipate], are studied with respect to the nanoclay incorporations. For different nanoclay types and concentrations, the morphologies of these nanocomposites are probed and correlated to their viscoelastic, mechanical, and thermal properties, along with their crystallization behavior and kinetics and gas permeability. The nanoclay dispersion and distribution characteristics are found to be key parameters influencing the final properties. In particular, nanocomposites with a higher degree of nanoclay dispersion exhibit significant enhancement in their mechanical, thermal, and barrier properties, and some agglomerations are effective as regards favorable crystallization behavior. In terms of the clay localization, the positioning of nanoclays at the interface reduces the minor phase size remarkably, because of the droplet encapsulation that counteracts coalescence. However, for improved understanding of the influence of nanoclay localization on the structure?property relationships of these blends, further systematic study is required. That is, nanocomposites with different localizations but the same nanoclay loads should be compared. This can be achieved by tuning the processing protocols and the nanoclay inclusion orders in the blends
Tuning the StructureâProperty Relationships in Binary and Ternary Blends of PLA/PBAT/PHBH
No full textWhile the brittle polylactide (PLA) has a high durability among bioplastics, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) with certain ductility exhibits facile compostability. The addition of polybutylene adipate terephthalate (PBAT) may also be used to improve the ductility and toughness of brittle bioplastics. Binary and ternary blends of PLA/PBAT/PHBH based on either PLA or PHBH as the matrix have been manufactured using a twin-screw extruder. The melt rheological, mechanical, and morphological properties of the processed samples were examined. Binary blends of PLA/PHBH show superior strength, with the PLA75/PHBH25 blend exhibiting a tensile strength of 35.2 +/- 3.0 MPa, which may be attributed to miscible-like morphology. In contrast, blends of PLA with PBAT demonstrate low strength, with the PLA50/PBAT50 blend exhibits a tensile strength of 9.5 +/- 2.0 MPa due to the presence of large droplets in the matrix. PBAT-containing blends exhibit lower impact strengths compared to PHBH-containing blends. For instance, a PLA75/PBAT25 blend displays an impact strength of 1.76 +/- 0.1 kJ/m2, whereas the PHBH75/PBAT25 blend displays an impact strength of 2.61 +/- 0.3 kJ/m2, which may be attributed to uniformly dispersed PBAT droplets
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