Torque Rheology Research Articles

Mechanochemical preparation and performance evaluations of bitumen-used waste polypropylene modifiers

The value-added recycling of waste polypropylene (PP) as asphalt modifiers has been a popular research topic in recent years, but high blending temperatures and asphalt smoke emissions are difficult issues that have not been solved. Therefore, this study innovatively used phthalic anhydride (PA) and catalysts (NHPI or BPO) to mechanochemically turn waste PP into different reaction products as bitumen-use PP modifiers (PPM(N) & PPM(B)). To well understand the physicochemical characteristics of PPMs, thermogravimetric analysis, torque rheology, and scanning electron microscopy were adopted and analyzed. Furthermore, the penetration, softening point, viscosity, storage stability, and dynamic shear rheology (DSR) tests were also carried out to study the performance differences of their PP modified asphalt (PPMA(N) & PPMA(B)). The main results showed that the PPM(N) continues being degraded with PA, but BPO-degraded PP conversely gets chemical connections with PA. With the effects of NHPI and BPO, all PPMs can improve the deformation resistance of virgin bitumen, even at higher temperatures, but as the PA content increases, this performance will gradually deteriorate for PPMA(N) and shows a slight improvement for PPMA(B). The appropriate use of PA can decrease the mixing temperature of PPM(N) with virgin bitumen and improve the storage stability of PPMA binders, and will not significantly sacrifice the resistances of its PPMA(N) to deformation, while with the addition of PA, the mixing temperatures of PPM(B) and virgin bitumen will not be decreased as expected and the resistances of PPMA(B) to deformation remain unchanged. Overall, the proposed mechanochemical method can work out to well address the high-quality recycling and reuse issue of waste PP for its large-scale application in asphalt pavement.

Characterization of Posidonia oceanica Fibers High-Density Polyethylene Composites: Reinforcing Potential and Effect of Coupling Agent

This study investigated the influence of fiber loading and maleated polyethylene (MAPE) coupling agent on the structural, thermal, mechanical, morphological properties, and torque rheology of high-density polyethylene (HDPE) reinforced with Posidonia oceanica fiber (POF) composites. HDPE/POF composites, both with and without MAPE, were manufactured using a two-step process: composite pellets extrusion, followed by test samples injection molding with various POF loadings (0, 20, 30, and 40 wt%). HDPE/POF composites reinforced with higher loading of POF (40 wt%) exhibit superior stiffness, better crystallinity, and higher stabilized torque and mechanical energy (Em) compared to other composite formulations. Therefore, varying the POF loading leads to extrusion and injection processing variations. Furthermore, the coupling agent significantly enhances the tensile strength, ductility, impact strength, crystallinity, stabilized torque, and Em of the HDPE/POF composite. This improvement is due to the enhanced interfacial adhesion between the POF and the HDPE matrix with the addition of the MAPE, as supported by the Scanning Electron Microscopy (SEM) micrographs.

Composite excipients for preparing concentrated water pills of personalized traditional Chinese medicine prescriptions by extruding-rounding method

This study aims to optimize the composite excipients suitable for the preparation of concentrated water pills of personalized traditional Chinese medicine prescriptions by the extruding-rounding method and investigate the roles of each excipient in the preparation process. The fiber materials and powder materials were taken as the standard materials suitable as excipients in the preparation of personalized concentrated water pills without excipient. Water absorption properties and torque rheology were used as indicators for selecting the materials of composite excipients. The ratio of composite excipients was optimized by D-optimal mixture design. Moreover, to demonstrate the universal applicability of the optimal composite excipients, this study selected three traditional Chinese medicine prescriptions with low, medium, and high extraction rates to verify the optimal ratio. Finally, the effects of each selected excipient on the molding of personalized concentrated water pills were investigated with the four parameters of the pill molding quality as indicators. The optimized composite excipients were dextrin∶microcrystalline cellulose(MCC)∶low-substituted hydroxypropyl cellulose(L-HPC) at a ratio of 1∶2∶4. The composite excipients were used for the preparation of personalized concentrated water pills with stable process, good quality, and a wide range of application. Dextrin acted as a diluent and accelerated the speed of extruding. MCC mainly served as an adhesive, increasing the cohesion and viscosity of the pills. L-HPC as a water absorbent and disintegrating agent can absorb and hold the water of the concentrate and has a strong disintegration effect.

Thermal-and-mechanochemical recycling of waste polypropylene into maleated-epoxided degradation products as warm-mix asphalt modifier: Performance improvement and production mechanism analysis

Polypropylene (PP) wastes do not easily mix with asphalt binder to reach a uniformly dispersed phase at a regular blending temperature as a result of its very high melting temperature and molecular nonpolar properties. With considering their use in asphalt applications, the melting temperature needs be reduced, together with improved polymer-asphalt compatibility using effective treating approaches. Therefore, this study proposes an innovative thermal-and-mechanochemical method to efficiently convert waste PP into maleated-epoxided degradation products as warm-mix asphalt modifiers (PPMs) through hybrid use of dicumyl peroxide (DCP), maleic anhydride (MAH), and epoxidized soybean oil (ESO), for modification and property enhancement of virgin binder. The modified asphalt (PPMA) binders with different treated PPMs and untreated PPM were prepared at blending temperatures of 140∼170 °C and 170–180 °C, respectively. Further, the viscosity, softening point, ductility, storage stability, and micro-morphology tests were characterized for the prepared PPM modified asphalts (PPMAs), while torque rheology, melt flow rate (MFR), thermogravimetric analysis (TGA), and Fourier transform infrared (FTIR) spectra were measured for these PPMs, in order to analyze the performance improvement and cleaner production mechanisms. The results showed that the collective use of DCP, MAH, and ESO can cause a series of chemical reactions, including degradation and grafting, to PPM0 for the generation of maleated-epoxided degradation products with lower thermal stability and higher melt fluidity under thermal-and-mechanochemical treatment. Optimally, the maleated-epoxided PPM containing 5% ESO reduces the softening point difference of virgin binder by almost 70% due to the improved the modifier-asphalt compatibility, and its storage stability, softening point and viscosities are most improved. Overall, the designed processing method can promote waste PP to be upcycled into maleated-epoxided degradation products that can be used as warm-mix performance-enhancing modifiers.

Thermo-mechanochemical recycling of waste polypropylene into degradation products as modifiers for cleaner production and properties enhancement of bitumen

Recycled polypropylene (rPP) wastes have been used to improve the high-temperature performance of asphalt. However, the high melting temperature of rPP does not match the conventional mixing temperature of bitumen, resulting in more energy consumption and emissions. Therefore, this study adopted dicumyl peroxide (DCP) to chemically degrade the rPP through a melt-shear processing method to obtain the corresponding modifiers (rPPM) with better flowability at a lower temperature. Torque rheology, melt flow rate (MFR) and thermogravimetry analysis (TGA) characteristics of rPPM incorporated with different dosages (1‰, 3‰, and 5‰) of DCP were compared to that of rPP. Correspondingly, the rPPM modified asphalt (rPPMA) were characterized by penetration, softening point, viscosity, and the dynamic shear rheology (DSR) tests. The TGA test showed that the rPPMs have a lower thermal stability as compared to rPP, and the MFR of rPPM can be up to 1900% larger than that of the rPP. The rPPMs can contribute to increasing the softening point and reducing by almost 50% penetration of virgin binder, which are reflected that they can improve the high-temperature performance of virgin binder. The DSR results stated that rPPM can provide a slightly improved deformation resistance and a lower anti-fatigue characteristic, comparative capacities, as well as a relatively lower deformation resistance and higher fatigue failure to the virgin binder, respectively. Accordingly, 3‰ DCP is optimally recommended to degrade rPP to obtain the modifier for the cleaner production and enhancement of modified binders.

Modulating sorbitol crystallization using impurities

Abstract Sorbitol crystallization in complex systems, such as those seen in sugar-free confectionery products, is not well understood. By leveraging torque rheology, crystallization onset time was measured using the inflection point at which torque increased during mixing as a result of crystallization. Select impurities (mannitol, maltitol, and glycerol) were used 5, 10, and 20% to determine their impact on sorbitol crystallization behavior from 10% moisture sorbitol syrups. Binary and ternary blends of the same impurities were also evaluated at a total impurity addition level of 20% to investigate any synergies. Overall, mannitol had the most pronounced inhibition of sorbitol crystallization onset time, with onset time being directly proportional to the amount of mannitol added. Interestingly, despite inhibited onset time, mannitol did not impact the final torque measurement and the impact on melting point was minimal; this differed from the other ingredients studied as well as ingredient blends.

Polyoxymethylene/graphene nanocomposites: thermal, crystallization, melting and rheological behavior

Polyoxymethylene (POM) and graphene nanoplatelets (GNP) nanocomposites were produced and their thermal properties investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Torque rheology was used to evaluate melted nanocomposites behavior. As nanofiller, two commercial GNP grades were used and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), DSC and TGA showing great morphological and structural differences. Nanocomposites thermal stability has increased for additions up to 0.25 wt.% of both nanoparticles. However, for concentrations above 0.50 wt.%, severe matrix degradation was observed. The extent of the effect on the thermal stability of the materials also varied with the grade of GNP used and seems to be related with GNP’s extent of oxidation and defect density. The extrusion process was optimized in order to minimize secondary thermal degradation mechanisms, showing that the nanofiller nature is the most relevant factor in POM/GNP based systems. DSC analyzes showed that the addition of GNP interferes with the polymer crystallization process, alters the degree of crystallinity and increases the crystallization temperature, indicating that GNP acts as a nucleating agent for POM. The torque rheology showed that slope and level of the torque curve seems to be related with the stabilization or degradation effect observed in the thermal analysis, allowing immediate qualitative evaluation of degradation effect during extrusion process.

Determination of optimum polymer dosage for dewatering of oil sands tailings using torque rheology

The slow settlement of fine clay particles in oil sands tailings, the by-product from the process of bitumen extraction from the oil sands ores takes many years, leading to the build-up of an enormous volume of fluid fine tailings in tailings ponds over time, which also gives rise to the biggest challenge in tailings management – poor dewatering rate and long consolidation time. Adding polymers can promote the flocculation of clay particles, and thus, can improve the dewaterability of tailings. However, choosing an ideal polymer dosage for a particular tailings composition or fine-tuning the polymer dosage based on the changes in tailings composition has always been a challenge for the oil sands industry. This study examined the potential of two rheological methods, which are based on torque rheology and measure the rheological parameters (i.e., peak torque and totalized torque) to determine the optimum polymer dosage. When the tailings sample was subjected to a shearing force in a torque rheometer and a polymer solution was injected into that sample simultaneously, the rheometer measured the torque on the impeller. The peak torque and the totalized torque were determined from the torque-time rheogram and their interpretations provided useful information on the strength of the elastic floc network, which was formed after adding the polymer, and also on the degree of flocculation. When the polymer dosage was increased in a stepwise manner and the resulting peak torques and totalized torques were plotted against the corresponding polymer dosages (six polymer dosages in total: 0.2, 0.4, 0.6, 0.8, 1.0, and 1.2 g/kg of dry solids), a local decrease was observed in both plots at the dosage of 0.8 g/kg of dry solids, which also corresponded to the shortest suction time determined from the capillary suction time tests and the highest solids settlement obtained from the settling tests at the same dosage. Hence, the results suggested that the measurement of peak torque and totalized torque could be used as a reliable control parameter for the optimization of polymer dosage for the dewatering of tailings.

High-performance lignocellulose/polycarbonate biocomposites fabricated by in situ reaction: Structure and properties

The use of lignocellulosic fiber in polycarbonate composites is limited due to its low thermal stability. In this study, the thermal stability of wood flour was improved by a boric acid treatment. Then, the wood flour/polycarbonate composites with an outstanding mechanical performance were obtained through melt extrusion and injection. Results showed that wood flour and polycarbonate underwent esterification reactions during the extrusion process. The effect of wood flour on torque rheology and thermal, mechanical, and creep properties of the resulting biocomposites was also characterized and analyzed. A maximum increase of 147.2% in flexural modulus was obtained while the flexural strength hardly changed. The addition of wood flour altered the thermal properties of polycarbonate. Adding wood flour improved the anti-creep and coating properties of the composites. The boric acid modification protected lignocellulose from thermal degradation, thereby promoting the manufacture at a high temperature of biocomposites based on engineering plastic.

Design, fabrication of honeycomb-shaped 1–3 connectivity piezoelectric micropillar arrays for 2D ultrasound transducer application

As a core component of 2D ultrasound transducers, honeycomb-shaped 1–3 connectivity piezoelectric micropillar arrays have attracted enormous attention due to their unique performance and functionality. In this paper, honeycomb-shaped 1–3 connectivity piezoelectric micropillar arrays with a high aspect-ratio were designed and fabricated by means of deep X-ray lithography and powder injection molding in six steps: preparation of lost mold, powder-binder mixing, injection molding and demolding, removal of binders, and densification of powder. A polymer-based lost mold insert was generated by a synchrotron X-ray exposure and development process. The optimal volumetric ratio between the piezoelectric powder and binders was determined by torque rheology behavior, then they were homogeneously mixed with a twin extruder mixer. To fully fill in the micro-cavities of the lost mold, rheological properties of the mixture were analyzed with a capillary rheometer using different shear rates (50–5000 s−1) and temperatures (140 °C, 150 °C, and 160 °C). After the mixture was completely injected, the lost mold was chemically dissolved in acetone and rinsed in methanol without bending or clustering of the micropillar arrays during evaporation. The binders in the injection molded portion were thermally decomposed using a continuous heating schedule of 200 °C, 390 °C, and 600 °C in argon gas under atmospheric conditions. Finally, the particles in the sample were densified into a coherent, solid mass by eliminating pores at 1300 °C. Based on the proposed micro-manufacturing process, defect-free honeycomb-shaped 1–3 connectivity piezoelectric micropillar arrays with a pattern dimension of 42 μm and aspect-ratio of 5 were successfully produced.

A “one stop” thermal stabilizer, zinc arginine complex, with excellent comprehensive thermal stability effect on poly(vinyl chloride)

A “one stop” thermal stabilizer, zinc arginine complex (Zn(Arg)2), with excellent excellent initial whiteness, whiteness retention and long-term thermal stability time for PVC, was conveniently synthesized in water solution. The successful synthesis of Zn(Arg)2 was confirmed by FTIR, TGA and element analysis. Besides the longer Congo red and static thermal stability time than nitrogen-containing thermal stabilizer reported, Zn(Arg)2 also had better initial whiteness, whiteness retention and dynamic thermal stability time showed by Congo red test, discoloration test and torque rheology test. Especially, the static thermal stability time was more than 150 min, and the dynamic thermal stability time reached 78 min. The excellent thermal stability effect of Zn(Arg)2 on PVC was ascribed to the simultaneous possession of three mechanisms: absorbing HCl, replacing labile chlorine atoms and complexing ZnCl2. Moreover, PVC with Zn(Arg)2 also showed excellent transmittance tested by vis-uv-near infrared spectrophotometer. Therefore, Zn(Arg)2 is a “one stop” thermal stabilizer with good application prospects in transparent PVC.

Impact of shear on crystallization behavior of sorbitol

Shear has the ability to promote crystallization through increasing the rate of primary and secondary nucleation as well as accelerate the formation of more stable polymorphs. Understanding the impact of shear on crystallization in systems that contain sorbitol as the primary bulk sweetener is essential for efficient process design as well as controlling texture and stability. By manipulating relevant formulation (0–10% seed crystals, 4–10% moisture content) and processing variables (40–60 °C temperature), this study aims to quantify their effects on sorbitol crystal growth and structure in sorbitol syrups subjected to shear. It was determined that moisture content, temperature, and seed crystals all had a significant impact on crystallization onset time (α = 0.05), and that increased supersaturation resulted in decreased onset time. Additionally, shear was shown to promote the formation of more stable polymorphs and torque rheology was determined to be a suitable way to measure effects of formulation changes on crystallization kinetics in sorbitol syrups.

Nonisothermal crystallization studies of PBT/ZnO compounds

Compounds of poly(butylene terephthalate) (PBT) and zinc oxide (ZnO) with filler content between 1 and 10% were prepared in a laboratory internal mixer. The processing parameters did not damage PBT thermal stability or its molecular weight as evidenced by torque rheology. The melt crystallization of PBT/ZnO compounds was investigated by differential scanning calorimetry and their morphology by scanning electron microscopy and optical microscopy. From morphological analyses, ZnO particles are well dispersed in PBT matrix, which crystallizes in typical spherulites. The melt crystallization temperatures and maximum melt crystallization rates are almost unaffected by the filler. Equally the overall crystallinity did not show any dependence on the filler content or the cooling rate. Mo’s model was found to be suitable for a description of the melt crystallization kinetics, while Ozawa model turned out to be inadequate.

The properties of flax fiber reinforced wood flour/high density polyethylene composites

Flax fiber (FF) was used to reinforce wood flour/high density polyethylene composites (WF/PE). WF/PE particles were uniformly mixed with FF via high-speed mixing and then extruded with a single screw extruder to prepare FF reinforced WF/PE composites (FF/WF/PE). Mechanical testing, dynamic mechanical analysis, scanning electron microscopy (SEM), creep measurement and Torque rheology were used to characterize the resulting composites. The results indicate that the mechanical performance of the composites could be remarkably improved by adding a limited amount of FF. The flexural strength and modulus increased by 14.6 and 51.4%, respectively (FF content of 9 wt%), while the unnotched impact strength could be increased by 26.5% (FF content of 12 wt%). The creep resistance and toughness of the composite was markedly improved without changing the plastic content of the composite material.

Toughening effect of liquid natural rubber on the morphology and thermo-mechanical properties of the poly(lactic acid) ternary blend

In this work, poly(lactic acid) (PLA) was melt blended with liquid natural rubber (LNR) and linear low-density polyethylene (LLDPE) to fabricate a PLA–LNR–LLDPE ternary blend. The torque rheology demonstrates the melt mixing behavior of PLA–LLDPE binary and PLA–LNR–LLDPE ternary blends. Mechanical properties of ternary blend illustrate the highest toughness as compared to neat PLA and PLA–LLDPE binary blend. Fracture morphology reveals the plastic deformation behavior in the ternary blend which is illustrated in TEM micrograph. The cold crystallization temperature of the ternary blend appears at a lower temperature as compared to the binary blend. The thermal stability of PLA is improved due to blending with LLDPE and LNR. The ternary blend exhibits greater storage modulus in the glassy state as well as in the rubbery state as compared to neat PLA and binary blend. Finally, LNR performed as an effective compatibilizer between PLA and LLDPE.

Polyvinylidene Fluoride/Acrylonitrile Butadiene Rubber Blends Prepared Via Dynamic Vulcanization

Dynamically vulcanized blends based on polyvinylidene fluoride (PVDF)/acrylonitrile butadiene rubber (NBR) were prepared and characterized. The mixing torque and dynamic rheology analyses showed that the NBR phase increased the viscosity of the blends. Scanning electron microscopy (SEM) results showed that the NBR phase was in the form of spherical particles dispersed in the PVDF phase during dynamic vulcanization. Comparing PVDF-rich and NBR-rich blends, the size of the rubber particles in the NBR-rich blends were larger than those in PVDF-rich blends. Differential scanning calorimetry (DSC) results showed that the addition of the NBR phase reduced the PVDF crystallinity and Tm. Thermal gravimetric analysis (TGA) results showed that the dynamically vulcanized PVDF/NBR blends had a higher residual char mass than the neat PVDF and NBR. For PVDF-rich blends, the PVDF can be highly toughened by NBR; the Izod impact strength of the PVDF/NBR (70/30) blend was 77.5 kJ/m2, which was about six times higher than that of pure PVDF. For rubber-rich blends, the PVDF component was beneficial to the mechanical properties of the blends, which can be used as thermoplastic elastomers.

Foaming behaviour of microcellular foam short carbon fibres/polypropylene/nano-CaCO3 composites

In this paper, nano-CaCO3 was added into short carbon fibre/polypropylene composites in order to improve foamability. According to differential scanning calorimetry results, there were slight influences on the melting point and crystallinity with the addition of nano-CaCO3. The increase in melt strength with nano-CaCO3 content could be qualitatively certified by torque rheology curves. The dispersion of nano-CaCO3 was determined by scanning electron micrograph. Depressurisation foaming method was used to foam the composites using supercritical CO2. Characterisation of the cell morphology was conducted to investigate the effects of the nano-CaCO3 content and processing conditions. Concerning the effect of nano-CaCO3 content, it is found that the mean cell diameter first decreased and then increased, whereas the cell density showed the opposite trend. Moreover, increasing saturation pressure or decreasing foaming temperature made the cell size smaller and the cell density larger.

Effects of Metal Ion Type on Ionomer-Assisted Reactive Toughening of Poly(lactic acid)

In this study, toughening of poly(lactic acid) (PLA) through reactive blending with epoxy-containing elastomer and ionomer was investigated. Four commercial ionomers based on the poly(ethylene-co-methacrylic acid) (EMAA) precursor were evaluated in this study, which contained zinc, magnesium, sodium, an lithium ions, respectively. Effects of metal ion type, elastomer/ionomer weight ratio and blending temperature on impact toughness of PLA ternary blends were studied. The toughening effects of metal ions of the ionomers is in the order of Zn > Mg > Li ≈ Na. High blending temperature and high elastomer/ionomer ratio both promoted the effective toughening of the PLA ternary blends. The reactive compatibilization and cross-linking of the epoxy-containing elastomer were analyzed using FT-IR, SEM, dynamic mechanical analysis, and torque rheology. In addition, the effect of metal ion type on thermal degradation of PLA was also examined.

Torque rheology of zircon feedstocks for powder injection moulding

Abstract In this work, a cellulose acetate butyrate (CAB) and polyethylene glycol (PEG) blend is used as the binder system in a zirconium silicate mineral powder feedstock for powder injection moulding. These irregular zircon powders make the mixing process and the selection of an optimal solid loading level a difficult task. Torque rheology methodologies combined with other techniques are used for evaluation of the parameters affecting the mixing process and determination of the critical powder volume concentration (CPVC). Temperature variations during the mixing process are monitored and used as an indicator of the friction energy of the system and thus for the optimal solid loading selection. There have thus far been limited amounts of work conducted on torque rheology of highly loaded feedstocks that incorporate a study of the system's temperature evolution. A detailed study could be a key factor for understanding the mixing behaviour of highly loaded feedstocks.

Interaction of Microstructure and Interfacial Adhesion on Impact Performance of Polylactide (PLA) Ternary Blends

Polyactide (PLA) was blended with an ethylene/n-butyl acrylate/glycidyl methacrylate (EBA-GMA) terpolymer and a zinc ionomer of ethylene/methacrylic acid (EMAA-Zn) copolymer. The phase morphology of the resulting ternary blends and its relationship with impact behaviors were studied systematically. Dynamic vulcanization of EBA-GMA in the presence of EMAA-Zn was investigated by torque rheology, and its cross-link level was evaluated by dynamic mechanical analysis. Reactive compatibilization between PLA and EBA-GMA was studied using Fourier transform infrared spectroscopy. The dispersed domains in the ternary blends displayed a “salami”-like phase structure, in which the EMAA-Zn phase evolved from occluded subinclusions into continuous phase with decrease in the EBA-GMA/EMAA-Zn ratio. An optimum range of particle sizes of the dispersed domains for high impact toughness was identified. Also, the micromechanical deformation process of these ternary blends was also investigated by observation of the impact-fractured surfaces using the electron microscope. It was suggested that the low cavitation resistance of dispersed particles in conjunction with suitable interfacial adhesion was responsible for the optimum impact toughness observed.