Increase In Complex Viscosity Research Articles

Recycling of a commercial biodegradable polymer blend: Influence of reprocessing cycles on rheological and thermo-mechanical properties

Mechanical recycling is a viable option for reducing plastic waste, especially for post-consumer waste and scraps from production processes. Biodegradable polymers have gained attention as alternatives to conventional ones, and their potential for reprocessing using standard techniques before composting needs to be explored. This study focused on a commercial biodegradable polymer blend which underwent ten extrusion cycles to assess the effects of mechanical recycling on mechanical properties, rheological behavior, and thermal stability. The results indicated that the blend's mechanical properties were largely maintained across the extrusion cycles, with only a 53 % decrease in ductility. The thermal stability slightly declined by 2.3 % in T5% onset temperature. This can be attributed to a balance between molecular chain scission (resulting in an average molecular weight reduction of approximately 8.4 %) and crosslinking phenomenon (evidenced by an increase in complex viscosity throughout the extrusion cycles). Overall, the results suggest a suitable recycling attitude of this material.

Poly(butylene terephthalate)/poly(ethylene glycol) blends with compatibilizers

AbstractPolymer blend systems offer a versatile approach for tailoring the properties of polymer materials for specific applications. In this study, we investigated the compatibility of polybutylene terephthalate (PBT) and poly(ethylene glycol) (PEG) blends processed using a twin‐screw extruder, with the aim of enhancing their compatibility. Phthalic anhydride (PAn) and phthalic acid (PAc) were used as potential compatibilizers at different concentrations to improve interfacial interactions between PBT and PEG. Blend morphologies were characterized using scanning electron microscopy, which revealed improved interfacial compatibility and reduced phase separation with the incorporation of small amounts of PAn and PAc. Differential scanning calorimetry analysis indicated changes in the melting temperature (Tm) and glass transition temperature (Tg) of the blends owing to the compatibilizing effects of PAn and PAc. Dynamic mechanical analysis further corroborated the influence of the compatibilizers on the Tg and viscoelastic behavior. Thermogravimetric analysis demonstrated enhanced thermal stability with the addition of either PAn or PAc. Rheological measurements indicated an increase in complex viscosity with increasing compatibilizer content, indicating improved compatibility. The degradation point (Td) of PBT/PEG blend increased from 158 to 200 and 319°C with the incorporation of 5 phr PAn and 2 phr PAc, respectively. Mechanical properties, including tensile strength, Young's modulus, and Izod impact strength, were evaluated. For instance, the tensile strength of PBT/PEG blend was enhanced from 43.5 to 48.7 and 49.7 MPa by incorporating 5 phr PAn and 2 phr PAc, respectively. However, the impact strength of PBT/PEG blend increased from 3.0 to 4.3 and 4.2 kJ/m2 with the addition of 1 phr PAn and 1 phr PAc, respectively. The findings demonstrated that adding 5 phr PAn or 2 phr PAc to the PBT/PEG blends was advantageous, achieving a harmony of performance benefits and compromises. Rheological observations contributed significantly to the mechanical and thermal properties. Overall, the study highlights the significance of utilizing PAn and PAc as effective compatibilizers for enhancing the properties of PBT/PEG blends, making them potential candidates for various applications.

Open time studies of cold curing polyurethane adhesives using a standardized spatula test setup suitable for near-production conditions

The presented studies introduce a new set-up and method to analyse the maximum open time of cold curing adhesives in a production environment. By using this new set-up, a manual spatula test, Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR) and a rheological method, the curing reaction of two cold curing two component polyurethane adhesives, were investigated. Furthermore, the effect of different joining times on the bonding behaviour were investigated using single lap shear samples.The lap shear tests showed that the prior problem for industrial applications is the dimensional accuracy rather than the adhesion to the substrates as all samples showed cohesive or substrate near cohesive failure even when joined after the maximum open time. All used methods showed a coherent curing behaviour for both adhesives. However, the derived times as well as their accuracies vary depending on the used method. Using the easy manual spatula test, the open time is determined by the sensory feelings of the testing person while pressing a wooden spatula into the adhesive bead and is often used in industrial applications. However, the accuracy lies only within 10–20 s especially for slow curing adhesives. In comparison, the ATR-FTIR method, which is based on the decrease of the isocyanate group during the reaction, showed shorter times, whereas longer times were determined by observing the complex viscosity increase of the rheological measurements. Even though the ATR-FTIR and rheological measurements showed reproducible times due to the required laboratory environment and testing procedure, they are therefore not suitable for production conditions. As the introduced new method is based on the manual spatula test, it is suitable for the production environment with the advantage of a good reproducibility. Furthermore, with this method decreasing maximum open times were observed for increasing bead cross sections.

Effects of tannic acid on proteins and fat in cream

sThe addition of polyphenols to ice cream mix has been shown to cause a decrease in melting rate of that ice cream, although the mechanisms of this effect are not well understood. To better understand this phenomenon, the objective of this study was to understand the effects of a polyphenol, tannic acid (TA), on dairy cream. TA was added to cream at 0.75%, 1.5% and 3% (wt/wt) concentrations. An increase in complex viscosity was seen as TA% increased. The effect of pH on protein aggregation was minimal since the pH values of the resulting TA-cream samples were generally above the isoelectric point of milk proteins. Microscope images and particle size distributions confirmed the presence of fat globule clusters in these samples, creating a network at 3% TA. Using sodium dodecyl sulfate (SDS) and ethylenediaminetetraacetic acid (EDTA) to disperse both fat and protein, average particle size and microscope images suggested that milk protein-TA interactions helped create the clusters. No evidence of partial coalescence was observed. These findings can help optimize the complex effect of polyphenols in the dairy matrix to create higher quality products.Graphical

Functionalization of various coffee husk biofibers on the rheological and thermomechanical properties of poly(butylene succinate)-urethane blended composites

Many studies have reported that surface-functionalized biofibers originating from plant waste can be used to improve the compatibility and processability of polymer blend systems. This study investigated the effects of size distribution and surface treatment of coffee husk (CH) biofibers on the rheological and thermomechanical properties of poly(butylene succinate)/thermoplastic polyurethane polymer blend composite. CH is a coffee waste with interlinked complex macromolecular structure of lignocellulose materials like cellulose, hemicellulose, and lignin. It was found that the handling and processability of the composites improved after the CH was surface-functionalized with diisocyanate/methacrylate prior to composite fabrication. Smaller-sized surface-treated CHs showed superior processability owing to the entanglement of fibers through the matrices associated with the improvement of interfacial adhesion. Therefore, the frequency-dependent rheological test revealed an increase in complex viscosity and storage modulus with the surface treatment and size reduction of CHs. Regardless of the size distribution, the degree of crystallinity of poly(butylene succinate) in the composites filled with surface-treated CHs reduced by about 20%. The composites with treated CHs also demonstrated superior thermal stability than their corresponding composites with raw CHs.

Miscibility, thermal degradation and rheological analysis of epoxy/MABS blends.

The effect of the addition of the methyl methacrylate acrylonitrile butadiene styrene (MABS) copolymer on the miscibility, thermal degradation and rheological properties of epoxy systems is described. Epoxy resin/MABS blends containing 5, 10, 15 and 20 phr MABS were prepared using the solution mixing technique. Homogenous blends obtained using this technique have undergone a polymerization reaction induced phase separation process by the introduction of the curing agent 4,4'-diaminodiphenyl sulfone (DDS). The isothermal rheology at four different temperatures, 150, 160, 170 and 180 °C, was used to examine the effect of MABS on the gelation and vitrification time. The evolution of storage modulus, loss modulus and tan delta was found to be closely related to the evolution of complex phase separation. The increase in the complex viscosity during curing was determined by in situ rheometry and theoretically analysed by fitting with the Williams-Landell-Ferry equation. An exponential increase in complex viscosity was observed, which was induced by cross-linking. The variation of Tg before and after curing was studied using DSC analysis and dynamic kinetic modeling of the curing process was carried out by utilizing dynamic DSC scans. Thermal stability studies of completely cured epoxy/MABS blends using thermogravimetric analysis revealed that all the blends and neat epoxy exhibited single step degradation. Thermal degradation kinetics was calculated using the Coats Redfern equation.

Intrinsic flame retarding and non-dripping liquid crystal polyethylene terephthalate copolyesters for fire safety system

The notorious issue of high fire hazards, including the generation of considerable heat and melt dripping, is recognized as the bottleneck of extensive use of polyethylene terephthalate (PET). Although various techniques have been adopted for the fabrication of flame retardant PET, how to address the contradiction of flame retardancy and anti-dripping while maintaining its good processability in an environment-friendly method is still challenging. Hence, we design and prepare an intrinsic flame retardant copolyester based on PET and thermotropic liquid crystalline polymer (PET/TLCPx) via a simple and efficient one-step melt copolymerization to address the above challenges. On the one hand, the mesogen units not only allow copolyesters to show a typical liquid crystalline behavior with excellent processability but also constructs a highly rigid main chain to endow PET/TLCPx with outstanding thermal stability, fire resistance, and non-dripping. Furthermore, the resultant PET/TLCP3 exhibits a much lower (by 72 %) peak heat release rate than that of PET, which is attributed to the formation of a denser char layer (char yield ∼ 37 %) for excellent fire resistance. Meanwhile, the melt dripping of PET/TLCPx is suppressed with the increase of complex viscosity and the growth of molecular weight due to the post-condensation during combustion. The resultant high-performance copolyesters are highly valuable for high-end applications that have strict requirements for fire safety and thermal stability, such as fire alarm and rescue systems based on triboelectric effect and shape memory behaviors.

Tailoring Nylon 6/Acrylonitrile-Butadiene-Styrene Nanocomposites for Application against Electromagnetic Interference: Evaluation of the Mechanical, Thermal and Electrical Behavior, and the Electromagnetic Shielding Efficiency.

Nylon 6/acrylonitrile-butadiene-styrene nanocomposites were prepared by mixing in a molten state and injection molded for application in electromagnetic interference shielding and antistatic packaging. Multi-wall carbon nanotubes (MWCNT) and maleic anhydride-grafted ABS compatibilizer were incorporated to improve the electrical conductivity and mechanical performance. The nanocomposites were characterized by oscillatory rheology, Izod impact strength, tensile strength, thermogravimetry, current-voltage measurements, shielding against electromagnetic interference, and scanning electron microscopy. The rheological behavior evidenced a severe increase in complex viscosity and storage modulus, which suggests an electrical percolation phenomenon. Adding 1 to 5 phr MWCNT into the nanocomposites produced electrical conductivities between 1.22 × 10−6 S/cm and 6.61 × 10−5 S/cm. The results make them suitable for antistatic purposes. The nanocomposite with 5 phr MWCNT showed the highest electromagnetic shielding efficiency, with a peak of –10.5 dB at 9 GHz and a value around –8.2 dB between 11 and 12 GHz. This was possibly due to the higher electrical conductivity of the 5 phr MWCNT composition. In addition, the developed nanocomposites, regardless of MWCNT content, showed tenacious behavior at room temperature. The results reveal the possibility for tailoring the properties of insulating materials for application in electrical and electromagnetic shielding. Additionally, the good mechanical and thermal properties further widen the application range.

Thiolated 2-Methyl-β-Cyclodextrin as a Mucoadhesive Excipient for Poorly Soluble Drugs: Synthesis and Characterization.

Thiolated cyclodextrins are structurally simple mucoadhesive macromolecules, which are able to host drugs and increase their apparent water solubility, as well as interact with the mucus layer prolonging drug residence time on the site of absorption. The aim of this study was to synthesize through green microwave-assisted process a freely soluble thiolated 2-methyl-β-cyclodextrin (MβCD-SH). Its inclusion complex properties with dexamethasone (Dex), a poor water soluble drug, and mucoadhesive characteristics were also determined. The product was deeply characterized through NMR spectroscopy (2D COSY, 2D HSQC, 1D/2D TOCSY, and 1D ROESY), showing a thiolation degree of 67%, a selective thiolation on the C6 residues and a monomeric structure. The association constant of MβCD and MβCD-SH with Dex resulted in 2514.3 ± 32.3 M−1 and 2147.0 ± 69.3 M−1, respectively, indicating that both CDs were able to host the drug. Microrheological analysis of mucin in the presence of MBCD-SH showed an increase of complex viscosity, G′ and G″, due to disulphide bond formation. The cytotoxicity screening on fibroblast BALB/3T3 clone A31 cells indicated an IC50 of 27.7 mg/mL and 30.0 mg/mL, for MβCD and MβCD-SH, respectively. Finally, MβCD-SH was able to self-assemble in water into nanometric structures, both in the presence and absence of the complexed drug.

Dual role of nanoclay in the improvement of the in-situ nanofibrillar morphology in polypropylene/polybutylene terephthalate nanocomposites

The present study has addressed the effects of nanoclay on the properties of polypropylene (PP)/polybutylene terephthalate (PBT) blend fibers such as their dyeability and, rheological and resiliency behaviors which are produced by melt spinning. The results of the differential scanning calorimetry (DSC) analysis indicated that the presence of both nanoclay and PBT significantly influenced the crystallinity of PP which also confirmed their nucleating effects on the nanocomposite fibers. Compared to neat PP fibers, the incorporation of 0.5–1wt.% of nanoclay and 10 wt.% of PBT nanocomposite fibers caused approximately 23% and 52% enhancements in the resiliency and dye uptake respectively without using toxic carriers. The rheological analysis was carried out for investigating the viscoelastic behavior, and microstructural and dispersion of nanoclay in the nanocomposite fibers. The rheological behavior in the small amplitude oscillatory shear (SAOS) test demonstrated the percolation threshold network of the structure of PBT fibrils in the PP matrix. When the PBT domains are fibrillated, the storage modulus (G′) and complex viscosity increase compared to neat PP. Also, the nonterminal behavior at low frequencies indicates the uniform dispersion of nanoclay in fiber nanocomposites. These all cause the improvement of the melt strength of the PP matrix. Transmission electron microscopy (TEM) was used to study the dispersion and localization of nanoclay. Nanoclay has also played a compatibilizing role in the immisible PP/PBT blend and was localized mainly in the PBT disperse and interface, and therefore prevented coalescence. The role of the compatibility of nanoparticles is to decrease the mean diameter of the nano-fibrils to 75 nm, for the hot-drawn nanocomposite fibers, as measured by scanning electron microscopy (SEM). All of the above lead to increasing the melt strength and elasticity of the nanocomposites in the fiber spinning process.

PMMA-driven morphology modification and dramatic improvement in ductility for PVDF/PLA blends

Poly(methyl methacrylate) (PMMA) was incorporated as compatibilizer in immiscible poly(vinylidene fluoride) (PVDF)/poly(lactic acid) (PLA) blends at different ratios. Scanning electron microscopy results revealed that, after adding PMMA, the phase morphology of PVDF/PLA blends evidently changed and the boundary became diffused, indicating improved interaction between PVDF and PLA. The sea-island biphasic morphology of PVDF/PLA (1:1) blend transferred to pseudo co-continuous morphology with the incorporation of PMMA. Differential scanning calorimetry and polarized light microscopy results showed that the presence of pre-crystallized PVDF facilitated the crystallization of PLA on cooling from the melt, but the molten PLA slightly retarded the crystallization of PVDF. With the inclusion of PMMA in the blends, PVDF crystal growth was further inhibited due to its miscibility with PMMA, and its crystallinity was also decreased. The elongation at break (ductility) of PLA and PVDF/PLA blends increased drastically by up to 27.8 and 11.1 times respectively, after formation of ternary PVDF/PLA/PMMA blends. Dynamic mechanical analysis results showed that the individual glass transition temperatures of PVDF and PLA in the blends shifted to higher temperatures after adding PMMA. PMMA showed more affinity to PVDF than to PLA. Rheological property measurements confirmed the increase in complex viscosity and storage modulus of the blends with increasing PMMA loading.

Self-Assembly of Temperature Sensitive Additives in Polypropylene Melt and Its Influence on Viscoelasticity

The use of a temperature-sensitive nucleating agent (NA) for polypropylene (PP), besides its influence on the crystallization characteristic, provides a platform to affect the rheology of molten PP by controlling its self-assembly behavior. In this study, in order to clarify the dependence of the melt rheology properties on the self-assembly behavior of N,N′,N′′-tricyclohexyl-1,3,5-benzenetricarboxylamid, changes in the NA content and final process temperatures (Tf) were used to control the self-assembly behavior of the NA molecules. The morphological and rheological behavior of samples were studied at 180 °C and evaluated by using central composite design-response surface methodology (CCD-RSM). The polarized optical microscopy results showed a fibril shape structure with a length in the range of 26–94 μm and diameter of 3–11 μm. The regression analysis models revealed that the increase in NA wt % and Tf favored the formation of larger fibrils in length and diameter, and the impact of NA wt % was more significant than Tf. Shear rheometry results indicated that the fiber size and its distribution were both directly related to an increase in complex viscosity and storage modulus. The study of the zero shear viscosity, crossover frequency, Cole–Cole plot, and also ANOVA analysis indicated that the optimal value for Tf is 270 °C and for NA is 0.5 wt %.

Microcellular foaming and mechanical properties of iPPF reinforced PPR composites

Fibers are often used to improve the mechanical properties of the polymers. Herein, a facile self-reinforcement method of adding isotactic polypropylene fiber (iPPF) to polypropylene random copolymer (PPR) was developed to enhance its foamability and mechanical properties. Rheological, foaming, crystallization behaviors and mechanical properties of the blends were studied. Elastic modulus, viscous modulus and complex viscosity increase with increasing iPPF content. Due to enhanced viscoelasticity, comparatively uniform PPR-iPPF cells were fabricated. Cell density of PPR-30 iPPF was increased by two orders of magnitude, compared to that of pure PPR, because of the enhanced melt strength and heterogeneous nucleation effects. Compared to solid PPR, the impact strength of foamed PPR-10iPPF was increased by 170%. For both solid and foamed samples, the tensile strength was increased with increasing of iPPF content. However, the tensile strength of the foamed sample is lower than that of solid sample, regardless of the iPPF content.

Fabrication of Surfactant-Dispersed HiPco Single-Walled Carbon Nanotube-Based Alginate Hydrogel Composites as Cellular Products.

In this study, we designed, synthesized, and characterized ultrahigh purity single-walled carbon nanotube (SWCNT)-alginate hydrogel composites. Among the parameters of importance in the formation of an alginate-based hydrogel composite with single-walled carbon nanotubes, are their varying degrees of purity, their particulate agglomeration and their dose-dependent correlation to cell viability, all of which have an impact on the resultant composite’s efficiency and effectiveness towards cell-therapy. To promote their homogenous dispersion by preventing agglomeration of the SWCNT, three different surfactants-sodium dodecyl sulfate (SDS-anionic), cetyltrimethylammonium bromide (CTAB-cationic), and Pluronic F108 (nonionic)-were utilized. After mixing of the SWCNT-surfactant with alginate, the mixtures were cross-linked using divalent calcium ions and characterized using Raman spectroscopy. Rheometric analysis showed an increase in complex viscosity, loss, and storage moduli of the SWCNT composite gels in comparison with pure alginate gels. Scanning electron microscopy revealed the presence of a well-distributed porous structure, and all SWCNT-gel composites depicted enhanced electrical conductivity with respect to alginate gels. To characterize their biocompatibility, cardiomyocytes were cultured atop these SWCNT-gels. Results comprehensively implied that Pluronic F108 was most efficient in preventing agglomeration of the SWCNTs in the alginate matrix, leading to a stable scaffold formation without posing any toxicity to the cells.

Effect of Al2O3 nanoparticle on viscoelastic and filtration properties of a salt-polymer-based drilling fluid

ABSTRACT Conventional bentonite-based drilling fluids have associated problems while drilling troublesome or high-temperature zone due to degradation of rheological properties and excessive fluid loss. Clay particles present in the drilling fluid tend to block the pore throats and cause blockage to hydrocarbon flow. Similarly, polymers along with the filtrate loss, in the invaded zone, alter the wettability due to which there is a reduction in relative permeability to oil. All of these factors collectively cause a fall in production rates and demand stimulation jobs. The use of nondamaging drilling fluids, a particle-free salt-polymer-based drilling fluid, has addressed these problems by yielding a substantially less filtrate loss. However, at moderately high depths with high temperatures, this drilling fluid fails to maintain rheological properties and hence sagging, carrying, and fluid loss problems remerge. Sagging increases the equivalent circulation density which eventually decreases rate of penetration and induces formation damages. Hence, a need to further improve its properties is much required. This study has investigated the effect of aluminum oxide nanoparticles (Al2O3 NP) on these salt-polymer-based drilling fluids. A significant change was observed in rheological and fluid loss properties of drilling fluid (DF) when doped with different concentrations (0.5%, 0.8%, and 1%) of Al2O3 NP compared to the Base DF. Steady shear (rotational) tests were conducted to study the degree of shear thinning behavior of all the drilling fluids. It was observed that shear thinning behavior of the DF was increased with the addition of Al2O3 NP. Rotational measurements at 30°C showed a decrease in viscosity and shear stress of Al2O3 NP DF with an increase in concentration. However, at elevated temperatures of 60°C and 80°C, the reduction in viscosity of Al2O3 NP DF was substantially less than Base DF. One percent Al2O3 NP DF showed higher viscosity as compared to 0.5%, 0.8% Al2O3 NP, and Base DF at these conditions. To investigate the viscoelastic properties, oscillation tests were performed. Amplitude sweep tests showed an increase in storage modulus (G’) with an increase in Al2O3 NP concentration. While Base and 0.5% Al2O3 NP DF showed viscoelastic liquid in nature, 0.8% and 1% Al2O3 NP DF showed dominant storage properties indicating its viscoelastic solid nature at 30°C, 60°C, and 80°C. From the frequency sweep tests at higher temperatures, 0.8% and 1% Al2O3 NP DF, unlike Base and 0.5% Al2O3 NP DF, showed increase in complex viscosity at lower frequencies indicating structural build-up. Both rotational and thixotropic tests showed less structural regain time for 1% Al2O3 NP DF compared to other drilling fluid. Lastly, fluid loss control property of all the drilling fluids was investigated by measuring the filtrate loss volume in an API filter press apparatus. One percent Al2O3 NP DF showed a greater reduction in filtrate volume with Base DF showing the highest.

Viscoelastic characteristics of heavy crude-oil-water two-phase dispersed mixtures

The viscoelastic characteristics of unstable heavy crude-oil-water dispersed mixtures are investigated to improve pipeline transportation. The effects of temperature, dispersed phase volume fraction, and droplet size distribution are considered on experiments. And, the unstable characteristics of heavy crude-oil-water dispersed mixtures, which display the similar droplet size distribution as the two-phase pipeline flow, is emphasized in this study. As a result, the mixing of water into heavy crude oil does not considerably affect the storage modulus that maintains a constant value even with the changing oil volume fractions. The loss modulus increases with the increased oil volume fractions of the oil-in-water dispersed mixtures. It increases to its maximum value when the oil volume fraction increases to the phase inversion point of oil-water mixtures. After the phase inversion point, the loss modulus decreases as the oil volume fraction increases which can be described by the modified Mooney model accurately. The viscoelastic parameters decrease with increasing temperature because the mechanical strength of the interfacial film and the ability to resist droplet deformation due to shear force decrease when the temperature increases. The storage modulus, loss modulus, and complex viscosity increase as the median diameter decreasing with the approximate exponent behaviors. This is because the link force between two droplets is increased by a smaller distance through a longer stirring time which will decrease the median diameter. Also, the smaller droplet, which is more difficult to deform by shear stress, can increase the values of the viscoelastic parameters. Furthermore, the critical elastic dominant and viscous dominant are investigated through the critical frequency. In conclusion, the unstable heavy crude-oil-water dispersed mixture displays the great different viscoelastic characteristics compared to the normal crude-oil-water emulsions. The unstable characteristics must be considered in the design of the heavy crude oil and water two-phase dispersed flow system. It is important for understanding the pipeline transportation system of heavy crude-oil-water mixtures.

Non-Isothermal Crystallization Behavior of PEEK/Graphene Nanoplatelets Composites from Melt and Glass States.

The effect of the graphene nanoplateletets (GNP), at concentration of 1, 5 and 10 wt %, in Poly ether ether ketone (PEEK) composite crystallization from melt and during cold crystallization were investigated by differential scanning calorimetry (DSC) and real time X-ray diffraction experiments. DSC results revealed a double effect of GNP: (a) nucleating effect crystallization from melt started at higher temperatures and (b) longer global crystallization time due to the restriction in the polymer chain mobility. This hindered mobility were proved by rheological behavior of nanocomposites, because to the increase of complex viscosity, G′, G″ with the GNP content, as well as the non-Newtonian behavior found in composites with high GNP content. Finally, real time wide and small angle synchrotron X-ray radiation (WAXS/SAXS) X-ray measurements showed that GNP has not affected the orthorhombic phase of PEEK nor the evolution of the crystal phase during the crystallization processes. However, the correlation length of the crystal obtained by WAXS and the long period (L) by SAXS varied depending on the GNP content.

Polypropylene/polystyrene/clay blends prepared by an innovative eccentric rotor extruder based on continuous elongational flow: Analysis of morphology, rheology property, and crystallization behavior

The polypropylene (PP)/polystyrene (PS)/montmorillonite (MMT) blends were prepared by an innovative eccentric rotor extruder based on continuous elongational flow. Addition of MMT nanoparticles was found to reduce the PS droplet size and improve the compatibility of PP/PS. The MMT nanoparticles had clear intercalation and/or exfoliation structures and were located mostly at the interface of PP/PS. It was found that the intercalation and exfoliation of MMT was finished under the synergy of interfacial interaction and tensile deformation so that we called the mechanism as “MMT exfoliation mechanism induced by synergy of interface and tensile deformation”. The rheological analysis showed that incorporation of MMT led to an increase in complex viscosity to an optimum level (5 wt%), after which any further increase in MMT concentration decreased the complex viscosity. Moreover, the degree of crystallinity of blends was controlled by the heterogeneous nucleation effect of MMT and the inhibition effect of PS.

Influence of Carbon Nanoparticles on Thermal, Mechanical and Rheological Properties of Polypropylene Nanocomposites Modified with Vinyl Trimethoxysilane

SummaryIn the present study, masterbatch of polypropylene and graphene nanocomposite was obtained by in situ polymerization. Afterwards, this masterbatch was diluted in commercial PP matrix previously treated with dicumyl peroxide (DCP) and vinyl trimethoxysilane (VTMS), originating grafted and reinforced filaments. Then, this material was crosslinked in water at 90 °C through condensation of hydroxyl groups derived from grafted PP chains. These materials were evaluated according to their thermal, mechanical and rheological properties. The results showed that it was possible to graft and crosslink PP, however, crosslinking was hindered by the presence of graphene sheets in the polymer matrix. In non‐reinforced crosslinked polymer, an increase in complex viscosity was observed, showing that actually occurred crosslinking. Furthermore, the grafted sample has lower molecular weight compared to the commercial PP. The crosslinked sample reduced its Newtonian plateau.

Thermoplastic Vulcanizate Based on Poly(lactic acid) and Acrylic Rubber Blended with Ethylene Ionomer

ABSTRACTA new thermoplastic vulcanizate (TPV) was developed by meltblending of poly(lactic acid) (PLA), acrylic rubber (ACM), and ethylene-methacrylic acid with sodium ions (EMAA-Na). The PLA/ACM/EMAA-Na blend showed low-yield strength, low modulus, and excellent strain recovery. It also demonstrated an increase in complex viscosity and decrease in melting temperature due to the interfacial reaction between the PLA and the ACM phases. The Fourier transform infrared spectroscopy results indicate that EMAA-Na can interact with both PLA and ACM, and that the Na+ ions act as a catalyst for the interfacial reaction between PLA and ACM, while PLA does not react with ACM without EMAA-Na. Moreover, the tensile strength at break of the PLA/ACM/EMAA-Na blend was observed to be extremely improved by the addition of hexamethylenediaminecarbamate (HMDC) due to the increasing of the cross-link density inside the rubber phase. The morphology of the PLA/ACM/EMAA-Na blend with HMDC was finer than that of PLA/ACM/EMAA-Na without HMDC. From the results, it is suggested that the interfacial reaction between the PLA and the ACM phases, the cross-linking in the ACM phase, and the finer morphology improved the mechanical properties of the blend.