Dynamic-mechanical thermoanalysis test as a high-performance alternative for accelerated freeze-thaw stability testing: a case study of O/W emulsions.

Objective: The main objective of this work was to evaluate the performance of recently developed dynamic-mechanical thermoanalysis (DMTA) test as a rapid rheological alternative to conventional freeze-thaw cycling for accelerated stability testing of oil-in-water (O/W) emulsions.Significance: The rational for this approach was reducing the time needed for product and process development and optimization, potentially through shortening the time needed for stability evaluation, in order to keep the pace with high formulating turnover imposed by increasing demands for placing products on the market, that is, to facilitate decision making in R&D and QC settings.Methods: Six model O/W emulsions were designed, rheologically characterized (continuous rotational and oscillatory tests), and subjected to stability evaluation through freeze-thaw test in stability chamber and DMTA tests using an air-bearing rheometer.Results: Investigated samples were characterized by favorized shear-thinning flow behavior with yield point. The elastic behavior dominated the viscous one in the LVE region of amplitude sweeps, as well as in the frequency sweeps of used frequency range. Statistical method comparison studies demonstrated that the results obtained by freeze-thaw test, routinely used for accelerated stability testing of emulsions, were in good accordance with those obtained with DMTA tests, whereas the time needed for stability assessment was significantly reduced (2-6 h versus 12 days).Conclusions: In summary, DMTA test proved to be an expeditious alternative for accelerated freeze-thaw stability testing of O/W emulsions, with great promise in new product development and optimization (R&D), as well as in determination of borderline product batches status (QC).

Dynamic-mechanical thermoanalysis test: a rapid alternative for accelerated freeze-thaw stability evaluation of W/O emulsions.

Objective: The aim of this study was to develop a new dynamic-mechanical thermoanalysis (DMTA) test and evaluate its performance as rapid rheological alternative to routinely used freeze-thaw test for accelerated stability testing of water-in-oil (W/O) emulsions.Significance: Due to inherent emulsion instability and versatilities of storage and use conditions, stability assessment of emulsion products still remains complex and challenging task. Recommended stability evaluation protocols are time-consuming, imposing need for alternate test procedures, especially in the early stage of product development, as well as in the quality assurance setting, including quality control.Methods: Five model W/O emulsions were prepared, comprehensively rheologically characterized (continual and oscillatory tests), and subjected to stability evaluation through freeze-thaw test in stability chamber and DMTA tests using an air-bearing rheometer.Results: Analyzed emulsions displayed desired shear-thinning flow behavior with yield point. The storage modulus dominated over the loss modulus in the linear viscoelastic regions of amplitude sweeps, as was the case in frequency sweeps over entire frequency range. Statistical comparison showed good agreement between freeze-thaw test, as a method available and used in daily routine work for accelerated evaluation of the physical stability, and DMTA test, as a rheological simulation of the said routine method. Duration of DMTA test was significantly shorter compared to routine but lengthy freeze-thaw test (3.5 h versus 12 days).Conclusions: According to our results, DMTA test could be a rapid alternative for accelerated freeze-thaw stability evaluation of W/O emulsions, thus enabling high formulating turnover and decision making in R&D and QC departments.

Complex influence of structural characteristics of low-methoxyl pectins on rheological properties of semi-solid Ca-gels.

The semi-solid Ca-gels were prepared from low-methoxyl pectins (methoxylation degree DM 4-36 %) of Oberna behen, Potamogeton natans, Tanacetum vulgare, Comarum palustre, Bergenia crassifolia, and Heracleum sosnowskyi. Pectins are characterized by Mw of 77-556 kDa and different content of HG and RG-I. The gels were prepared by addition of Ca2+ ions at varying stoichiometric ratios, R = 2 × [Ca2+]/[COO-], of 0.2-0.6, and a fixed pectin concentration of 10 g/L. It was shown that the presence of certain sets of structural characteristics in low-methoxyl pectins from different sources leads to the formation of gels with similar rheological properties. Pectins with Mw 77-98 kDa, DM 6-14 % form stiffer Ca-gels than pectins with Mw 218-253 kDa, DM 24-36 % at the same R. Pectins with Mw 346-556 kDa form the strongest Ca-gels. Their high Mw compensates for the influence of DM on the properties of Ca-gels. The stability of gels in PBS (pH 7.4) is determined mainly by proportion of 1,4-linked non-methoxylated GalA in pectins. Pectins with DM 4-14 % form more stable Ca-gels in PBS than pectins with DM 21-36 %.

Comprehensive rheological and mechanistic evaluation of an asphalt binder and mixture modified with warm mix additives.

Though warm mix asphalt (WMA) technology has been introduced for a long time, there is still reluctance in the industry to utilize it in practice. In regions like India, where WMA incorporation into road construction has been limited over the past two decades, building confidence in local binders is imperative for widespread adoption. Thus, the present study appraises the effect of three commonly used WMA additives in India, namely Sasobit®, Evotherm®, and Zycotherm®, with base binder VG-30 on the rheological and mixture performance parameters. Three dosages of each WMA additive were blended with the control binder to give ten binder combinations. Different binder evaluations such as Superpave grading and parameters, frequency sweep testing, multiple stress creep recovery test, and linear amplitude sweep test were conducted for comparative dynamic mechanical analysis. Based on the binder testing results, suitable dosages of WMA additives were established, and mixture testing was carried out using these specific additive dosages. Binder evaluations showed improvement in high-temperature characteristics with Sasobit® and better fatigue performance with Evotherm®, while Zycotherm® did not alter binder properties significantly. The asphalt mixture testing results indicated satisfactory performance with the three additives based on Marshall stability and flow testing. The WMA additives also showed enhancement in moisture susceptibility based on the modified Lottman test with Zycotherm® demonstrating the best performance. Overall, the study underscores promising effects of the three WMA additives across different parameters, signaling their potential for widespread application in real-world scenarios.

Evaluating Self-Healing Behaviour of Asphalt Binders Modified with Phase-Change Materials, Polymers and Recycled Glass Powder.

The objective of this paper is to evaluate the fatigue resistance and self-healing properties of asphalt binders modified with different types of additives (Styrene-Butadiene-Styrene (SBS), Glass Powder (GP) and Phase-Change Materials blended with Glass Powder (GPCM)). Two base binders were used in this study: a PG 58-28 straight-run asphalt binder and a PG 70-28 Polymer modified with 3%SBS. Moreover, the GP was added to the two base binders at two different percentages of 3.5% and 5% by binder weight. However, the GPCM was added with two different percentages of 5% and 7% by binder weight. In this paper, the fatigue resistance and self-healing properties were evaluated using Linear Amplitude Sweep (LAS) test. Two different procedures were adopted. In the first procedure, the load was applied continuously until failure (without a rest period), whereas, in the second procedure, rest periods of 5 and 30 min were introduced. The obtained results of the experimental campaign were ranked based on three different categories: Linear Amplitude Sweep (LAS), Pure Linear Amplitude Sweep (PLAS) and modified Pure Linear Amplitude Sweep (PLASH). The addition of GPCM appears to positively impact the fatigue performance of both straight-run and polymer-modified asphalt binders. Furthermore, when a short rest period of 5 min was introduced, the use of GPCM did not appear to improve the healing potential. However, a better healing capacity was observed when the 30 min rest period was applied. Moreover, the addition of GP alone to the base binder was not beneficial in improving fatigue performance based on LAS and PLAS methods. However, there was a slight reduction in the fatigue performance based on the PLAS method. Finally, unlike the PG 58-28, the healing capacity of the GP 70-28 was negatively affected by the addition of the GP.

Deformation characteristics of hydrogel products based on cross-linked hyaluronic acid.

BACKGROUND: The cross-linked hyaluronic acid (HA) fillers are the viscoelastic hydrogel with a dominant elasticity rather than a viscosity as a useful medical device in the soft tissue augmentation. These HA fillers undergo deformation to begin the biodegradation by the biochemical and physical environment of the body, and result of deformations are closely related to clinical performance. AIMS: The specific equation of molding index is newly generated and proved with Collin's equation, which is used for strong elastomers, for selecting optimal product in facial treatment. METHODS: In this study, the results of amplitude sweep test from five marketed HA fillers were mathematically demonstrated for the proper clinical application. RESULTS: The increment of loss modulus by deformation was evaluated as a useful factor for the maintenance of optimal shape molding performance and resistance to external deformation of the cross-linked HA gel. From this study, the equation of molding index for weak viscoelastic hydrogels like HA products can be applied for choosing which products even in aesthetic plastic field. This molding index equation is compared to Collins' equation that index of deformation as elastomer like rubber and then found the positive correlation between two equations. CONCLUSION: This study could provide a basic theory that achieve useful clinical performance according to characteristics among many types of medical devices based on the molding index.

Microwave Heating as an Innovative Road Maintenance Technology: Aging Effect on Binder and Feasibility Evaluation.

The microwave heating/healing technique is regarded as a green maintenance approach for asphalt pavements thanks to its promising environmental and economic benefits. However, the main concern about this technology is represented by the possible aging effect generated on bituminous binders. Currently, there is a significant lack of studies dealing with this topic. Based on these premises, the main purpose of this study is to appraise the feasibility of implementing microwave-based maintenance operations considering the associated aging effect. The assessment of fatigue life after cyclic microwave heating (MH) based on a linear amplitude sweep (LAS) test and the changes in the chemical groups detected through Fourier transform infrared (FTIR) spectroscopy document the aging phenomenon. The results indicate that the microwave aging degree on bituminous binder is nonlinear with MH cycles. The microwave radiation causes a distinct aging impact on binders during the first 10 cycles, then the values become constant. Furthermore, a feasibility analysis of MH technology is developed, encompassing four main multidisciplinary aspects: evaluation of microwave aging degree, working mechanism of MH equipment, safety assessment, and economic and ecological considerations. Despite the associated aging issue, the MH method is an efficient technology, considering its various advantages (i.e., rapidity of execution, uniform and non-pollutant treatment, and deep penetration). Meanwhile, the use of steel slag as a microwave absorber bolsters the sustainability of MH technology. This study provides a new perspective to evaluate the microwave heating technique in road engineering comprising the generated aging effect. Practice-oriented recommendations are also formulated regarding the safe implementation of MH technical operations.

Rheological Evaluation of Softened Binders Blended with Aged Asphalt Selected with a High-Temperature Mixing Chart.

Reclaimed asphalt pavements (RAP) provide economic and environmental benefits. In recent decades, their use has increased, but rheological properties are affected by RAP aging, increasing stiffness, cracking, and susceptibility to water. To counteract these effects, rejuvenating agents are used, but they must be properly dosed to design quality mixtures. Therefore, different binders were analyzed, including virgin binder (VBB), binder modified by SBS polymer (MB), AC-RAP, binder softened using a rejuvenating agent, and binders softened with doses (15%, 30%, and 45%) of AC-RAP. The rheological properties were evaluated by dynamic shear rheometry (DSR) and beam-bending rheometry (BBR) tests, while the linear amplitude sweep (LAS) test was used to measure fatigue cracking and the multiple stress creep recovery (MSCR) test was used to measure rutting. A mixing chart was constructed based on a high temperature AC-RAP to satisfy the performance grade (PG 76-22). The results showed that softened binders become flexible, but when AC-RAP is added, they turn stiff and behave better than MB. Moreover, combining a rejuvenating agent and AC-RAP reduces the aging stiffness of RAP, improving its rheological properties without compromising the rutting or cracking resistance.

Evaluating the Effects of High RAP Content and Rejuvenating Agents on Fatigue Performance of Fine Aggregate Matrix through DMA Flexural Bending Test.

High percentage reclaimed asphalt pavement (RAP) is prevailing in pavement engineering for its advantages in sustainability and environmental friendliness, however, its fatigue resistance remains a major concern. Fine aggregate matrix (FAM) is a crucial part in the fatigue resistance of asphalt mixtures with high RAP content. Hence, the linear amplitude sweep (LAS) test of FAM has been developed to study the fatigue resistance of asphalt mixtures. However, the torsional loading mode of the LAS test with a dynamic shear rheometer (DSR) is a limitation to simulate traffic load. In this paper, an alternative LAS test for FAM with high RAP content was proposed. Beam FAM specimens were tested using a dual-cantilever flexural loading fixture in a dynamic mechanical analyzer (DMA). To investigate the influence of RAP content and the rejuvenating agent (RA), four kinds of FAM mixes were tested with this method to study their fatigue resistance. The test results suggested that the repeatability of this alternative approach was reliable. A fatigue failure criterion based on maximum C × N was defined. Then, fatigue life prediction models based on viscoelastic continuum damage (VECD) analysis were established according to the LAS test results and validated by a strain-controlled time sweep (TS) test. It turned out that as RAP content increased, the modulus of FAM would be significantly raised, accompanied with a drop in the phase angle. The fatigue life of FAM would be greatly shortened when the RAP binder replacement rate reached 50%. Adding RA could considerably improve the dynamic properties of FAM mixes with high RAP content, resulting in a decrease in modulus, increase in phase angle and elongating fatigue life, but could not recover to the level of virgin binder.