Higher Mixing Temperatures Research Articles

Lignin dispersion in polybutadiene rubber (BR) with different mixing parameters

There is a strong need to replace carbon black and silica as a reinforcing filler in rubber industry. Lignin is a promising option as a replacement, because of its wide availability, complex chemistry and sustainable source. Typically, the reinforcing effect of lignin is weak and one major cause is the poor dispersion of filler. In this study, typical dispersion parameters in mixing are tested in a systematic way to validate their effect on kraft lignin dispersion in polybutadiene rubber. Tested mixing variables are temperature, rotor speed, mixing time, fill ratio and shear forces. The effect of variables to dispersion are analyzed from electron microscopy images with an image analysis software. With this novel method exact number of particles and their properties could be calculated. Unlike for conventional fillers (carbon black and silica), the results show clearly that only the mixing temperature has an effect on lignin dispersion in rubber. With high mixing temperatures, dispersion and hence mechanical properties improved. The better dispersion is especially seen as decreasing number of large (>Ø 5 μm) particles. Other mixing variables did not have significant effect on dispersion and the number of large particles.

Effect of mixing temperature on the dispersion and degradation behaviors of HDPE/UHMWPE blends

Abstract There is currently considerable interest in high-density polyethylene (HDPE)/ultra-high-molecular-weight polyethylene (UHMWPE) blends as recyclable all-polyolefin materials with favorable mechanical properties that can be processed by continuous melt-mixing. Optimal mixing is required to improve the mechanical properties of polymer blends by ensuring their dispersibility and low degradation. In the present study, we investigated the effects of mixing temperature on the dispersion and degradation behaviors of HDPE/UHMWPE blends. Neat HDPE and a HDPE blend comprising 5 % UHMWPE were obtained by melt-mixing while changing the input energy in an internal batch mixer under a nitrogen atmosphere. The temperature of the mixer was set at 200 °C for neat HDPE, and at 180, 200, and 220 °C for the HDPE/UHMWPE blends. Optical microscopy and thermal analysis revealed that the dispersion of UHMWPE in HDPE was accelerated at higher mixing temperatures. However, in the high input energy range, mixing at 200 °C resulted in the most favorable dispersion. Gel permeation chromatography and rheological measurements suggested that chain scission and branching/crosslinking due to degradation were accelerated at higher mixing temperatures, even when mixing in a nitrogen atmosphere. Chemiluminescence measurements suggested that chain scission and branching/crosslinking were caused by an initial oxidation reaction. Furthermore, for the same input energy, the maximum shear stress increased as the mixing temperature decreased, but the mixing time and thermal history increased as the mixing temperature increased. The results suggest that in a blend comprising HDPE and UHMWPE, mixing at the molecular level due to high temperature and fine dispersion of UHMWPE due to shear stress proceed simultaneously. On the other hand, the results also confirmed that degradation was more influenced by the promotion of oxidation due to high temperatures and prolonged mixing than by shear stress.

Evaluation of warm mix effect in laboratory using a self-developed WMA additive Alube

In response to the problems of high mixing temperatures and energy consumption of polymer-modified asphalt mixtures in road construction, a surfactant-based warm mix additive ‘Alube’ was developed. The warm mix SBS-modified asphalt and its mixture were prepared. Their rheological performance and chemical structure were analysed by the rheological and microscopic tests. The active mixing power (P) of asphalt mixtures were examined by the variable speed mixing (VSM) test. The mixing flowability model was then established to evaluate the warm mix effect. The results indicated that the mixing flowability of asphalt mixtures obeyed the linear Bingham visco-plastic model, and the slope and intercept of the flow straight characterised the mixing viscosity and plastic limit. It is evaluated that 0.7% Alube1 and Evotherm reduced the mixing temperature of SBS-modified asphalt mixture by 14°C and 12°C, respectively. Moreover, Alube1 is suitable for a wide range of applications through warm mix asphalt technology.

Morphology changes of polymer solid-solid phase change material in high-viscosity modified asphalt (HVMA) and its influence on the properties of HVMA

Asphalt pavement has excellent performance, but the asphalt binder is a temperature-sensitive material, which not only easily causes high-temperature distress, but also exacerbates the “urban heat island effect”. One possible method to solve this problem is to use phase change material (PCM) in the asphalt mixture, in which polymer solid-solid phase change material (PSSPCM) is one of widely used PCM. If the PSSPCM can be used in high-viscosity modified asphalt (HVMA), the high-performance modified asphalt with temperature regulation function can be obtained. However, the morphology of PSSPCM may change under the high mixing temperature of HVMA, which may also influence the properties of PSSPCM/HVMA composite. This paper selected one typical PSSPCM to investigate the morphology changes of solid-solid phase change material in HVMA and its influence on the properties of HVMA. The change of morphological and thermal property of PSSPCM in the high-temperature preparation were characterized by scanning calorimeter tests, thermogravimetric tests and heating tests, the physical, rheological and temperature regulation properties of PSSPCM/HVMA were also investigated. Test result shows that, the PSSPCM melted in HVMA at high mixing temperatures condition. However, when added in smaller contents of PSSPCM, the melted PSSPCM could uniformly distribute in the HVMA and the polymer network structure was formed. The melted and distributed PSSPCM in HVMA still had favorable temperature regulation function. The temperature regulation range of PSSPCM during the heating process and cooling process is maximum 3.8°C and 2.9°C respectively. Notably, the PSSPCM/HVMA has great high-temperature properties and favorable low-temperature properties. This study has reference value for developing the high-performance modified asphalt with temperature regulation function.

CO2-derived microalgae as a biomass filler to fabricate green composite

In this study, protein-rich microalgae (Chlorella sp. HS2) is investigated as a CO2-derived biomass particle to fabricate a sustainable green composite based on the physicochemical characterizations depending on the temperature and its dispersion and mechanical reinforcing effect in a polymer (poly(butylene adipate-co-terephthalate) (PBAT)) are investigated depending on temperature, incorporated with a small amount of reactive additives with peroxide or glycidyl functional groups. When HS2/PBAT is fabricated at a temperature higher than 130 °C, higher than that expected for thermal degradation of the protein in biomass, HS2 particles undergo cell disruption, changing the surface properties of the cells from hydrophilic to neutral and then reducing water absorption. This hydrophilic-neutral surface transition is attributed to the exposure of certain cell components, including proteins, lipids, and others such as amines, due to the disruption of the cells. It causes homogeneous dispersion of HS2 in PBAT during high mixing temperature. Despite the fact that HS2 is disrupted at high temperatures, the HS2 phase shows reactivity to reactive additives with peroxide or glycidyl functional groups, inducing interfacial bonding between PBAT and HS2 cells and enabling the composite to resist stretching deformation, resulting in increased tensile strength, particularly for composite films. This study demonstrates the potential of microalgae cells as a type of sustainability-reinforced biomass filler to fabricate a green composite. Different from natural biomass, microalgae HS2 cells, consisting of complex organic compounds, are disrupted at high mixing temperature and merged as a secondary phase in the polymer matrix. The addition of the CO2-derived microalgal biomass in synthetic polymer serves as the secondary phase and enhances sustainability, CO2 reduction, and cost-effectiveness without a significant sacrifice of mechanical performance.

Effect of Bitumen Production Process and Mix Heating Temperature on the Rheological Properties of Hot Recycled Mix Asphalt

Heavy traffic loads require the replacement of damaged pavements, so a huge amount of reclaimed asphalt pavement (RAP) material is now available and must be recycled in order to avoid landfill and to achieve both environmental and economic benefits. The most common and profitable solution to reuse RAP is associated with the hot recycling technique, as it allows recovering both solid and binding components of RAP. Several factors influence the performance of hot recycled mix asphalt (HRMA). Among those, this paper focuses on the role played by the origin of the virgin bitumen, i.e. the oil-distillation process, and by the mixing temperature adopted during HRMA production. The objective was to evaluate the rheological properties of mixtures produced using a high amount of RAP (50%), two different rejuvenators, two mixing temperatures (140 °C or 170 °C) and two neat bitumen types derived from different distillation processes (visbreaker and straight-run). The results showed that the addition of RAP led to an increase in the dynamic modulus and a decrease in the phase angle, while the use of rejuvenators partly tended to rebalance these characteristics. The visbreaker bitumen showed a higher sensitivity to short-term aging than the straight-run, determining higher mix stiffness and lower viscous features. The higher mixing temperature also determined an increase in the complex modulus and a reduction in the phase angle as a result of the higher mobilization of the aged bitumen from the RAP.

Performance of temperature adaptive microcapsules in self-healing cementitious materials under different mixing temperatures

The ease to be ruptured during mixing due to the brittleness of microcapsule shell limits the self-healing performance of microcapsules in concrete. In this study, a novel type of microcapsule with temperature-adaptive property (TAM) under different mixing temperatures was proposed to tackle this issue. The effect of TAM content and mixing temperature in self-healing cementitious materials was investigated. Based upon the confirmation of temperature adaptivity of microcapsule shell by dynamic mechanical analysis, the early age properties, including minislump, setting time and hydration heat, and the hardened properties of compressive strength and shrinkage, were determined. Moreover, the self-healing performance, in terms of strength healing and recovery rate, as well as the pore structures, of TAM in cementitious material was investigated. The results showed that the addition of TAM decreased workability and slightly extended the setting and hydration of cement, while the elevation of mixing temperature reduced workability and accelerated the setting and hydration of cement. Moreover, the addition of TAM and low mixing temperature reduced the compressive strength and shrinkage of hardened paste. Compared to the low mixing temperature, the self-healing performance in terms of strength and chloride migration was improved at high mixing temperature. The results proved the design concept of temperature adaptive microcapsules.

Influence of Internal Mixing Condition on Properties of Conductive Biocomposites between Poly(Lactic Acid) and Hybrid Graphene

The objective of this research was to investigate the influence of mixing condition on mechanical, thermal, and electrical properties of the biocomposite between poly(lactic acid) (PLA) and hybrid graphene (HG). PLA/HG composites of a fixed weight ratio (95/5 wt%) was mixed using an internal mixer, which the mixing temperatures (170, 180 and 200°C) and the rotor speeds (40, 60 and 80 rpm) were varied. It was found that the increase of E' before glass transition was attributed to the reinforcing effect of the HG. The faster the rotor speed was the higher storage modulus (E') was achieved at the lowest mixing temperature. The E' did not linearly depend on the rotor speed when mixing at higher temperature. As expected, mixing HG into PLA reduced the surface electrical resistivity. The mixing at 170°C with any rotor speed and mixing at 180°C with rotor speed of 40 or 60 rpm produced the composites in the same surface electrical resistivity, however, there was no significant difference when mixing at 200°C. From DSC analysis, there was a trend that the degree of crystallinity of the PLA/HG composites prepared at the lowest mixing temperature was higher than those prepared at the relatively higher mixing temperatures.

Use of Reclaimed Asphalt Pavement (RAP) and oily residues as pavement at low temperatures for low traffic roads

Rheological techniques are used to investigate the rejuvenation of aged bitumen. The thermal transition associated with the collapse of the compact structure constituted by asphaltene is determined by Dynamic Mechanical Thermal Analysis. For aged bitumen, this transition shifts to a higher temperature but when rejuvenating agents are added, the transition returns to its original value. The “rutting factor,” G*/sin δ allows to define the maximum temperature the binder can reach without permanent deformation. The employed rejuvenating agents are suitable because permanent deformation is postponed. Viscosity results reveal that aged bitumen needs a high mixing temperature (>200°C) to behave like a fluid material able to wet, adhere, and envelop aggregates. The addition of rejuvenating agents considerably reduces mixing and compaction temperatures. The mixture of 80% aged bitumen—20% recycled motor oil, obtained exclusively from waste materials is an apt binder that can compete satisfactorily with new 60/70 bitumen.

Investigation of Mixing and Compaction Temperatures of Modified Hot Asphalt and Warm Mix Asphalt

The determination of mixing and compaction temperatures through the Equiviscous method has been defined as the standard method and it is designed for the base bitumen (unmodified bitumen) based on the viscosity measurements. The implementation of the Equiviscous method for the modified bitumen resulted in high mixing and compaction temperatures which may not be required during the construction of the asphalt mixtures. This study aims to investigate several alternative methods proposed in the literature named as high shear rate method, zero shear viscosity method, steady shear flow method, and phase angle method. Besides, the obtained mixing and compaction temperatures results are compared with the standard (equiviscous) method. For this purpose, 50/70 penetration grade bitumen modified with 5 % elastomeric type – Styrene Butadiene Styrene (SBS), and 1.5 % Reactive Elastomeric Terpolymer type – Elvaloy (RET) has been used. The study also aims to measure the applicability of the proposed alternative methods for the warm mix asphalt involving organic and chemical additives. The results have shown that for the polymer modified bitumen, the application of all proposed methods in the literature resulted in lower mixing and compaction temperatures compared to the Equiviscous method. While for the warm mix asphalt, the implementation of the steady shear flow method resulted in lesser temperatures compared to the Equiviscous method.

Performance evaluation of temperature effect on hot in-place recycling asphalt mixtures

Hot in-place recycling (HIR) is a novel technique to rehabilitate the surface layer of the pavements, in which recycling agents are commonly utilized to restore the binder rheological properties of reclaimed asphalt pavements (RAP). Considering the energy consumption and smoke issue, the heating temperatures for HIR containing 100% RAP mix are usually controlled around 110 °C, which is significantly lower than that for the traditional hot mix asphalt (HMA). . To evaluate the effect of temperature on the performance of 100% recycled asphalt mixtures after the HIR process, the materials obtained from an HIR project were remixed and compacted at different temperatures (110 °C, 120 °C, and 130 °C). The asphalt mixture performance tester, asphalt pavement analyzer test, Superpave indirect tension tests, and moisture susceptibility tests were conducted to evaluate the performances of the HIR mix. The staged extraction tests were used to identify the mobilized RAP binders under different temperatures. It was revealed that mixtures heated with a higher temperature exhibit better cracking and moisture resistance performances. It was also found that a larger proportion of the RAP binders can be activated to coat the aggregates at a higher mixing temperature, which may increase the rutting potential.

Palm oil mill fly ash as a low-cost adsorbent for Rhodamine-B removal from industrial wastewater

In this study, the adsorption properties of Rhodamine-B (RB) on fly ash were investigated. Two different fly ashes conditions, including raw fly ash and activated fly ash, were selected for the adsorption experiment. The adsorption process is conducted by mixing fly ash 0.5; 1; 1,5 and 2g/L with the temperature of 30°C; 35°C; 45°C. The results showed that the HCl activation will enhance the MB adsorption capacity of fly ash, the higher the mass of adsorbent, and the higher mixing temperature, the better the performance of adsorbent is. Then, the great conditions for reducing RB with adsorbent mass 2g/L at temperature of 45°C, with a removal efficiency 90,54%

Evaluation of viscosity-temperature characteristics and rheological properties of rejuvenated SBS modified bitumen with active warm additive

The regeneration and utilization of reclaimed SBS modified bitumen require a high mixing and paving temperature, which result in a large of energy consumption and serious environment pollution. To reduce the mixing and paving temperature, polyethylene wax and active wax were selected to modify rejuvenated SBS modified bitumen, and their influences on the viscosity-temperature characteristics, physical and rheological properties of rejuvenated binder were thoroughly investigated in this research. The results indicate that active wax with epoxy terminal group shows a better performance on reducing the mixing and paving temperature of rejuvenated binder as compared with polyethylene wax. Meanwhile active wax modified rejuvenated binder shows the lowest flow activation energy 79.78 kJ/mol, indicating active wax is more helpful to improve the temperature sensitivity of rejuvenated binder at high temperature. Differential scanning calorimetry analysis shows the melting enthalpy of active wax is larger than that of polyethylene wax and polyethylene wax is easier to crystallize and solidify. These two warm additives all can improve the rutting resistance of rejuvenated binder. However, the cracking resistance of rejuvenated binder seriously decreases with the addition of polyethylene wax. While active wax could react with the active groups in rejuvenated binder that can inhibit the transition from viscosity to elasticity of rejuvenated binder and retain its excellent low-temperature performance more effectively as compared with polyethylene wax.

Investigation of the fatigue characteristics of warm stone matrix asphalt (WSMA) containing electric arc furnace (EAF) steel slag as coarse aggregate and Sasobit as warm mix additive

On the one hand, several million tons of steel slag is produced annually as the by-product of the steel industry in Iran and other countries and are deposited in landfills without any use, occupy vast areas, and cause environmental hazards. On the other hand, the high mixing temperature of the hot mix asphalt (HMA) increases the emission of greenhouse gases, the cost of fuel, accelerated wear of asphalt plant equipment, and less safety of workers in the field. These kinds of problems challenge the use of HMA mixtures and encourage to investigate more the WMA technology. This research intends to investigate the fatigue characteristics of warm stone matrix asphalt (WSMA), as one of the significant structural distresses of the flexible pavements, containing EAF steel slag as part of the coarse aggregate and Sasobit as the warm mix additive. The Marshal test results indicated higher Marshall stability and Marshal quotient for mixtures containing EAF steel slag compared to their similar mixtures (SMA + S vs SMA + N and WSMA + S vs WSMA + N) and all the mixtures met the NAPA specification requirements for Marshall stability, air voids, and optimum binder content. The result of draindown test for all of the mixtures was lower than the maximum amount determined by the specifications and means that the rock wool fibers, as asphalt stabilizers, preserved the asphalt mortar in the mixture well. The fatigue test results indicated that the use of EAF slag leads to comparable results to standard SMA and using warm mix additive (Sasobit) results in lower but acceptable results.

Silanization Efficiency of Silica/Silane in Dependence of Amines in Natural Rubber-based Tire Compounds

Silica-silane technology for low rolling resistance tire compounds requires efficient bridging between the silica surface and rubber molecules through silanization and coupling reactions. The presence of diphenylguanidine (DPG) as secondary vulcanization accelerator is also needed to catalyze the silanization reaction between the alkoxy groups of silane coupling agents and the silanol groups on the silica surface. However, DPG can liberate toxic aniline under high mixing temperatures and therefore safer alternatives are required. This study investigates the influence of amines with different structures, i.e. hexylamine (HEX), octadecylamine (OCT), cyclohexylamine (CYC) and dicyclohexylamine (DIC) on the primary silanization reaction rate constant in a model system, and on interfacial compatibility of practical silica-reinforced NR compounds. Compared to the system without, the amines clearly increase the reaction rate constant for which linear aliphatic amines work better than cyclic ones. This is due to better accessibility of the amines towards the silica surface, in agreement with the values of Payne effect as observed in the rubber compounds, except for the OCT case. The lowest Payne effect of the OCT-containing rubber compound is attributed to the additional shielding effect obtained from the long alkyl-chain that leads to more hydrophobicity, resulting in good physical interaction between silica and rubber. The presence of all amines improves the cure properties in which the linear aliphatic amines give shorter cure times than the cyclic aliphatic ones. As a result of good interfacial compatibility, the OCT-containing compound which shows lowest filler-filler interaction gives good mechanical properties that are closest to the reference compound with DPG.

Surface functionalization of rubber particles to reduce phase separation in rubberized asphalt for sustainable construction

Application of crumb rubber in asphalt has demonstrated many performance advantages for the pavement industry while bringing a solution for the disposal of the scrap tire. However, the introduction of rubber to asphalt binder has challenges associated with rubber segregation and workability. To address the latter issues, continuous agitation and high mixing temperature is commonly used which increases energy consumption, disintegration of crumb rubber, and emission of greenhouse gases. This paper introduces a newly developed surface activated rubber (SAR) prepared via a hybrid method of microwave treatment and bio-modification to alleviate the associated problems. The properties and performance of SAR were compared with those of conventional crumb rubber modified (CRM) and microwave-activated crumb rubber modified (M-CRM) asphalt. Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) and computational analysis using density functional theory (DFT) indicated successful grafting of biomolecules on the rubber particles. SAR showed 86% reduction in segregation index compared to the other CRM scenarios. Such enhancement was also reflected in a significant improvement in workability of SAR modified binder compared to the other CRM scenarios. Mechanical tests showed high fracture energy (167 J/m2) for SAR modified asphalt, which was approximately three times higher than that of conventional CRM asphalt (57 J/m2).

Chemical and Physical Properties Of Coconut Fiber In Asphalt Mixture: A Review

This paper is a review of the chemical and physical properties of coconut fiber in asphalt mixtures. Coconut fibers (CF) are natural fibers and also an agricultural waste, which is abundant after the extraction of juice and coconut fruit. Nowadays, CF has been studied for its potential use in the construction field to increase the strength of materials with its high tensile strength. Additionally, CF can also be one the materials in highway construction as it can improve the skid resistance of asphalt pavements. It was shown that CF treated with NaOH lowered the penetration value and increased the softening point of modified bitumen. Flow of bitumen also can be avoided at high mixing and compaction temperatures by adding 0.7% of CF.

Silica-Reinforced Natural Rubber: Synergistic Effects by Addition of Small Amounts of Secondary Fillers to Silica-Reinforced Natural Rubber Tire Tread Compounds

Modern fuel-saving tire treads are commonly reinforced by silica due to the fact that this leads to lower rolling resistance and higher wet grip compared to carbon black-filled alternatives. The introduction of secondary fillers into the silica-reinforced tread compounds, often named hybrid fillers, may have the potential to improve tire performance further. In the present work, two secondary fillers organoclay nanofiller and N134 carbon black were added to silica-based natural rubber compounds at a proportion of silica/secondary filler of 45/10 phr. The compounds were prepared with variable mixing temperatures based on the mixing procedure commonly in use for silica-filled NR systems. The results of Mooney viscosity, Payne effect, cure behavior, and mechanical properties imply that the silica hydrophobation and coupling reaction of the silane coupling agent with silica and elastomer are significantly influenced by organoclay due to an effect of its modifier: an organic ammonium derivative. This has an effect on scorch safety and cure rate. The compounds where carbon black was added as a secondary filler do not show this behavior. They give inferior filler dispersion compared to the pure silica-filled compound, attributed to an inappropriate high mixing temperature and the high specific surface area of the carbon black used. The dynamic properties indicate that there is a potential to improve wet traction and rolling resistance of a tire tread when using organoclay as secondary filler, while the combination of carbon black in silica-filled NR does not change these properties.

Effects of Wax-Based, Chemical-Based, and Water-Based Warm-Mix Additives on Mechanical Performance of Asphalt Binders

AbstractProduction of hot-mix asphalt (HMA) involves high mixing and compaction temperatures, which leads to the emission of greenhouse gases and high fuel consumption. Recently, various warm-mix a...

Effect of mixing temperature on the carbon nanofiller distribution in immiscible blends of polycarbonate and polyolefin

We studied the selective localization of carbon nanofillers, such as multi-walled carbon nanotube (MWCNT) and graphene nanoplatelet (GNP), in immiscible polymer blends composed of polycarbonate (PC) and polyethylene (PE) or ethylene-propylene copolymer (EPR). It was found that the distribution state of the carbon nanofillers in the composites is greatly affected by the mixing temperature and the species of nanofillers. MWCNTs resided in the PE or EPR phase in the composites, which cannot be explained by the difference in the interfacial tension. A similar morphology was detected in the PC/GNP/PE composite prepared at 300°C. In contrast, the PC/GNP/PE composite prepared at the low temperature (250°C) and the PC/GNP/EPR composites have the carbon nanofillers mostly in the PC phase. The selective localization in the PE or EPR phase is attributed to the surface adsorption of PE or EPR chains on the carbon nanofillers, which is more obvious for PE and at the high mixing temperature. These results demonstrate that both the species of carbon nanofillers and the mixing temperature affect the carbon nanofiller distribution in the immiscible blends.