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Secondary organic aerosols (SOAs) can exist in liquid, semi-solid, or amorphous solid states. Chemical transport models (CTMs), however, usually assume that SOA particles are homogeneous and well-mixed liquids, with rapid establishment of gas–particle equilibrium for simulations of SOA formation and partitioning. Missing the information of SOA phase state and viscosity in CTMs impedes accurate representation of SOA formation and evolution, affecting the predictions of aerosol effects on air quality and climate. We have previously developed a parameterization to estimate the glass transition temperature (Tg) of an organic compound based on volatility and to predict viscosity of SOA. In this study, we apply this method to predict the phase state of SOA particles over China in summer of 2018 using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem). The simulated Tg of dry SOA (Tg,org) agrees well with the value estimated from ambient volatility measurements at an urban site in Beijing. For the spatial distributions of Tg,org , simulations show that at the surface the values of Tg,org range from ∼287 to 305 K, with higher values in northwestern China, where SOA particles have larger mass fractions of low-volatility compounds. Considering water uptake by SOA particles, the SOA viscosity shows a prominent geospatial gradient in which highly viscous or solid SOA particles are mainly predicted in northwestern China. The lowest and highest SOA viscosity values both occur over the Qinghai–Tibet Plateau, where the solid phase state is predicted over dry and high-altitude areas and the liquid phase state is predicted mainly in the south of the plateau with high relative humidity during the summer monsoon season. Sensitivity simulations show that, including the formation of extremely low-volatility organic compounds, the percent time that a SOA particle is in the liquid phase state decreases by up to 12 % in southeastern China during the simulated period. With an assumption that the organic and inorganic compounds are internally mixed in one phase, we show that the water absorbed by inorganic species can significantly lower the simulated viscosity over southeastern China. This indicates that constraining the uncertainties in simulated SOA volatility distributions and the mixing state of the organic and inorganic compounds would improve prediction of viscosity in multicomponent particles in southeastern China. We also calculate the characteristic mixing timescale of organic molecules in 200 m SOA particles to evaluate kinetic limitations in SOA partitioning. Calculations show that during the simulated period the percent time of the mixing timescale longer than 1 h is >70 % at the surface and at 500 hPa in most areas of northern China, indicating that kinetic partitioning considering the bulk diffusion in viscous particles may be required for more accurate prediction of SOA mass concentrations and size distributions over these areas. [ABSTRACT FROM AUTHOR]

Secondary organic aerosols (SOA) can exist in liquid, semi-solid or amorphous solid states, which are rarely accounted for in current chemical transport models (CTMs). Missing the information of SOA phase state and viscosity in impedes accurate representation of SOA formation and evolution, affecting the predictions of aerosol effects on air and climate. We have previously developed a method to estimate the glass transition temperature (Tg) of an organic compound based on volatility. In this study, we apply this method to predict the phase state and viscosity of SOA particles China in summer of 2018 using the Weather Research and Forecasting model coupled to Chemistry (WRF-Chem). This first time that spatial distributions of the SOA phase state over China are investigated by a regional CTM. Simulations that Tg values of dry SOA range from ~287 K to 305 K, with higher values in the northwestern China where SOA particles have larger mass fractions of low volatility compounds. Considering water uptake by SOA particles, the SOA viscosity also shows a prominent geospatial gradient that highly viscous or solid SOA particles are mainly found in the northwestern China. The lowest and highest SOA viscosity values both occur over the Qinghai-Tibet Plateau that the solid state is predicted over dry and high-altitude areas and the liquid phase state is predicted mainly in the south of the plateau with high relative humidity during the summer monsoon season. The characteristic mixing timescale of organic molecules in 200 nm SOA particles is calculated based on the simulated particle viscosity and the bulk diffusion coefficient organic molecules. Calculations show that during the simulated period the percent time of the mixing timescale longer h is > 70 % at the surface and at 500 hPa in most areas of the northern China, indicating that kinetic partitioning considering the bulk diffusion in viscous particles may be required for more accurate prediction of SOA mass concentrations size distributions over these areas. Sensitivity simulations show that including the formation of extremely low-volatile organic compounds, the percent time that a SOA particle is in the liquid phase state decreases by up to 12 % in the southeastern China during the simulated period. With an assumption that the organic and inorganic compounds are always internally mixed in one phase, we show that the water absorbed by inorganic species can significantly lower the simulated viscosity over the southeastern China. This indicates that constraining the uncertainties in simulated SOA volatility distributions and accurately predicting the occurrence of phase separation would improve prediction of viscosity in multicomponent particles in southeastern China. [ABSTRACT FROM AUTHOR]

Copyright of DYNA - Ingeniería e Industria is the property of Publicaciones Dyna SL and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

BACKGROUND: According to the characteristics of low glass transition temperature of poly-D, L-lactic acid, we developed a new ultrasonic welding device to treat limb fractures with restorable poly-D, L-lactic acid screws. But whether the physical properties of poly-D, L-lactic acid changed by ultrasound has impact on material safety is unknown. In addition, under high intensity ultrasound action, the effects of absorbable screws on tissues around the absorbable screws remain unclear. OBJECTIVE: To evaluate the biosafety and histocompatibility of ultrasound-assisted absorbable poly-D, L-lactic acid screws in rats. METHODS: Twenty-four adult SD rat models of 1.6 mm-sized bone defects were made in the anterior side of the right tibial shaft, and then randomly divided into two groups. Absorbable poly-D, L-lactic acid screws were implanted in the experimental group and nothing was implanted in the control group. At postoperative 1, 3, 7 and 14 days and 2, 4, 6, and 8 weeks, routine blood tests, blood biochemical and serum inflammatory indicators were detected. At postoperative 2 weeks and 1, 3 and 6 months, gross observation, X-ray imaging, and histological observation of the bone defects were performed. This study was approved by the Animal Ethics Committee, West China Hospital of Sichuan University, China. RESULTS AND CONCLUSION: (1) In both experimental and control groups, after surgery, wounds healed well without signs of infection and rejection, and there were no abnormal fluctuations in routine blood tests, biochemical and inflammatory indicators. (2) Gross observation revealed that by 1 month after surgery, absorbable poly-D, L-lactic acid screws began to degrade with a small amount of cartilage callus crawling towards the center; by 6 months after surgery, there were a large amount of new bone around the screws, and no abnormal reactive hyperplasia was observed in the surrounding tissues. (3) X-ray showed that the bone defect area in the experimental group was gradually reduced, and by 6 months after surgery, there were a large amount of new bone, and no abnormal reaction of the surrounding bone matrix was observed. (4) Histological observation revealed that at 2 weeks after surgery, the interface between the screws and the bone was clear, adjacent bone trabeculae did not grow in the screws, and fibrous tissue proliferated and covered the surface of the materials. The screws gradually degraded, new bone tissue gradually increased and matured. (5) These results suggest that ultrasound-assisted absorbable poly-D, L-lactic acid screws exhibit good biosafety and histocompatibility and can degrade gradually in vivo. [ABSTRACT FROM AUTHOR]

Moisture sorption isotherms of water caltrop pericarp (WCP) powders were determined at 20, 30, and 40°C over water activity (Aw) range of 0.11 and 0.97. The adsorption isotherms decreased with the increase of temperature and exhibited Type II BET adsorption characteristics. The monolayer moisture content values calculated by the Guggenheim–Anderson–de Bor equation were found to be 0.0561, 0.0509, and 0.0409 g/g solids at 20, 30, and 40°C, respectively. The values of net isosteric heat of adsorption and differential entropy decreased from 26.094 to 0.250 kJ/mol, 76.665 to 0.358 J mol−1 K−1 with water content varying from 0.30 to 0.07 g/g solids, respectively. The isokinetic theory showed that the water adsorption process of WCP powders was governed by enthalpy. The values of specific surface area available for adsorption at 20, 30, and 40°C were 198.95, 180.40, and 145.11 m2/g, respectively. The spreading pressure increased with the increase of Aw values at a fixed temperature and decreased when temperature rising at a given Aw level. The effective pore size for WCP powders increased with the increment of water content and temperature, ranging from 1.648 to 21.761 nm. The glass transition temperature (Tg) of WCP powders was examined by differential scanning calorimetry and its values decreased from 72.34 to 2.42°C as water content ranged from 0.0499 to 0.352 g/g solids. The result showed that WCP powders remained stable at 30°C when the moisture content was lower than 0.149 g/g solids. Practical applications: Water caltrop (Trapa bispinosa Roxb) has been widely cultivated in China and other Southeast Asia because of its medical functions and delicious taste. The micronized water caltrop pericarp (WCP) is an excellent source of dietary fiber and phenolics and has been applied in various food and nonfood sectors. The objectives of this work were to evaluate the thermodynamic properties of water adsorption isotherms of WCP powders. In addition, a state diagram was established based on the water activity concept and glass transition theory. The results documented in this study will help design the energy process for producing WCP powders and predicting storage stability. [ABSTRACT FROM AUTHOR]

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• Three types of asphalt with the largest usage in China were tested. • Rubber# has the best anti-aging performance, followed by SBS# and 70#. • The glass transition temperature and the area ratio of characteristic functional groups increased after aging. • The GPC curve shifts to the macromolecular direction after asphalt aging. To study the effect of thermo-oxidative aging on the physical properties and microstructure of base and modified asphalts, conventional index tests, dynamic shear rheology (DSR), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, and gel permeation chromatography (GPC) were performed. The macro-physical indexes and microstructural changes in the asphalt before and after aging were analyzed. The results show that with an increase in the thermal-oxidative aging degree, the penetration degree of asphalt decreases; the softening point increases, and the high-temperature performance improves. Simultaneously, the asphalt consistency and hardness increase. This results in a significant increase in the initial modulus and glass transition temperature, decrease in the shear resistance, and degradation of the low-temperature performance. Rubber-modified asphalt exhibited the highest anti-aging performance, followed by styrene–butadiene–styrene-modified and 70# asphalts. Thermal-oxidative aging did not change the original functional group species; however, the peak area ratio of the sulfoxide and carbonyl functional groups increased significantly. After aging, the overall molecular weight of the asphalt shifted in the macromolecular direction. Weight-average and number-average molecular weights and polydispersity increased. [ABSTRACT FROM AUTHOR]

High-performance formaldehyde-free bio-based wood adhesives are extremely attractive because of the friendliness and sustainability of their ingredients and resources. This work reports a phenol-amine synergistic tannin bio-based adhesive inspired and designed by insect exoskeleton hardening and starfish structure. The phenol-amine synergistic strategy is based on Schiff base reaction and Michael addition between the benzoquinone group of tannin acid (TA) and the nucleophilic amino group of polyamines (PA XN , X = 4, 5 and 6, X represent the number of amino-terminal groups), which is supplemented by oxidation-induced quinone cross-linking in TA and the combination of covalent and non-covalent bonds. The proposed TAPA wood adhesives with the three-dimensional dense cross-linking network may dissipate stress via hiding sacrificial bonds, which can form a compact glue film to prevent the infiltration of water molecules as well as increase thermal resistance. FT-IR, XPS, and solid 13C NMR demonstrated the tannin-based phenol-amine network was formed by cross-linking imine covalent bonds. DSC, TG, and DMA revealed reduced melting and glass transition temperatures, as well as improved thermal stability, which are conducive to the cross-linking and curing of adhesives. In detail, the dry lap shear strength of TAPA adhesive increased by 170% from 0.8 MPa to 2.16 MPa compared with pure TA adhesive by using poplar veneer as wood substrate; and the wet lap shear strength made a breakthrough from 0 to 1.06 MPa, exceeding the minimum requirement (0.7 MPa) defined by the China national standard (GB/T 17657–2013). Given this, a high-efficiency, green, and economic phenol-amine synergistic strategy are beneficial to the development of formaldehyde-free bio-based wood adhesives and multifunctional application of agricultural and forestry residues. [Display omitted] • Tannin-based wood adhesives were prepared by phenol-amine synergy strategy. • FT-IR, XPS, 13C NMR, SEM, DSC, TG, and DMA characterization were carried. • Phenol-amine cross-linking network connected by covalent bonds and non-covalent bonds. • TAPA adhesives showed enhanced bonding strength, waterproof and thermal properties. • The formation of cross-linking network help to improve the performance. [ABSTRACT FROM AUTHOR]

Abstract: Pyrolysis of cyanobacteria from Dianchi lake was investigated by TG-DSC-FTIR analysis at different heating rates (10, 20, 40°C/min). The results indicated that the pyrolysis of cyanobacteria can be divided into four stages: evaporation, depolymerization, devolatilization and carbonization. Meanwhile, the initial weight-loss temperature, weight-loss extreme position, endothermic and exothermic peaks were moved to higher temperature with the increaseing of the heating rate. The kinetic analysis was made with Popescu method. It indicated that the best kinetic model for the pyrolysis of cyanobacteria was the cylindrical symmetry of the phase boundary reaction model. The main pyrolysis gases checked with real-time online FTIR were HCN, NH3, CO, CO2, water vapor and hydrocarbons. [Copyright &y& Elsevier]

As an important engineering material, polycarbonate (PC) has been used widely. When exposed to the environment, PC will have aging process, which will reduce its performance and efficiency. This article studies the changing regularities of PCs structure and properties of ageing in western areas of China by measuring the change of intrinsic viscosity (IV), thermal decomposition temperature, glass transition temperature, and the groups within PC. The analysis of its IV, DSC, and thermo gravimetric analysis exhibited the same changing regularity, i.e., the aged PC (in Lasa, Yuli, and Jiangjin) experienced degradation and crosslinking, while degradation occurred earlier in the process of ageing, crosslinking predominated in later period. In addition, the results of UV absorption spectra and infrared absorption spectra showed the evidence of decomposition of the ester groups, resulting in the production of alcohol and phenol. And the results of mechanical tests indicated that the ductility disappeared mainly in the first year of outdoor aging. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

In this study, the performance degradation law and mechanism of glass fiber reinforced polymer (GFRP) bars were investigated by being immersed in natural seawater (denoted as SW), saline-alkali solution (SA), or wrapped with concrete, and then submerged in natural seawater (SWC). A series of short-beam shear tests were conducted to investigate the effects of aging temperature and time on the interlaminar shear strength (ILSS) of GFRP bars. Microstructure changes, glass transition temperature (Tg) difference, and hydrolysis degree of GFRP bars after aging in three environments for 183 days were analyzed using scanning electron microscopy (SEM), differential scanning calorimeter (DSC), and Fourier transform infrared spectroscopy (FTIR). Test results demonstrated that the temperature could accelerate the strength degradation of GFRP bars significantly. After 183-day aging treatment at 60 °C, the ILSS retention rates of GFRP bars in the three environments of SW, SWC, and SA were 66.41%, 53.10%, and 45.36%, respectively; and Tg was 1.7%, 7.0%, 7.8% lower than that of unconditioned sample, respectively. Meanwhile different degrees of damage, such as separation between fiber and resin and few holes in the resin, were observed on the GFRP bars in the SWC and SA environments. It was also found that irreversible hydrolysis took place in some resins. The durability prediction model of GFRP bars serving in the Yellow Sea of China was established by using Arrhenius equation, and the correlation coefficient with the test data was not less than 0.94. [ABSTRACT FROM AUTHOR]

The article discusses a study of the synthesis, characterization and thermal properties of polyamides (PA) and polyimides (PI) with two silicon atoms in the main chain. Aldrich of Wisconsin and Riedel de Häen has provided the reagents and solvents, respectively. The silyl aromatic acid dichlorides were the sources of PA used in the study. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were utilized to assess the thermal stability of the materials.

Studies the diffusion of polymer chains at a temperature below its bulk glass transition temperature. Key issues of interest; Analysis of pertinent topics and relevant issues; Implications on Chinese studies of polymer science.

[Display omitted] • Oligomeric proanthocyanidin nanospheres were formed by molecular self-assembly. • Hydrogen bonding improves a variety of properties of the films. • Improve the difficulty of nanometer composite film melting processing. • Excellent UV resistance is applied to agricultural film. Almost 90,000 tons of larch bark, which contains 10–16 % anthocyanins by weight, is produced as waste in China each year. Here, proanthocyanidins from the bark of Larix gmelinii were used to prepare oligomeric proanthocyanidin nanospheres (OPCM). The OPCMs were then blended with poly(vinyl alcohol) (PVA) to produce OPCM/PVA nanocomposite films. Incorporation of OPCM not only improves the performance of the film but also expands the applications of proanthocyanidins and provides a way to reduce the environmental impact of waste bark. Scanning electron microscopy images showed that the OPCM were uniformly dispersed in the PVA, without macroscopic phase separation. OPCM/PVA nanocomposite film had improved mechanical and thermal properties compared with pure PVA film because of intermolecular hydrogen bonding between the OPCM and PVA. The tensile strength of nanocomposite film containing 3 wt% OPCMs was 95 % higher than that of PVA film and its toughness and elongation at break were also enhanced to some extent. Compared with PVA film, the glass transition temperature (T g) and peak decomposition temperature (T max) of nanocomposite film containing 10 wt% OPCM were increased by 10.4 °C and 20.2 °C, respectively. The addition of OPCMs also overcomes a major disadvantage of PVA film, which is that the melting temperature is close to T max , and thus facilitates melt processing of PVA composite materials. The composite film also had increased resistance to oxidation and better surface wettability than PVA film. Although the composite film had enhanced UV-blocking properties compared with PVA film, even films with the highest proportion of OPCM still showed good transmittance of visible light. Because both OPCs and PVA are biodegradable, the resulting nanocomposites are also biodegradable and can be regarded as suitable candidates for agricultural film and packaging materials. [ABSTRACT FROM AUTHOR]

Polyacrylate latex materials have become a hot area recently in China due to its environmental friendliness. However, the water whitening resistance of the polyacrylate latex products in the market is largely unsatisfactory, which seriously affects the appearance and performance of the latex products. In this work, the effect of glass‐transition temperature (Tg) of a polyacrylate latex film on its water whitening resistance was investigated. The light transmittance measurement showed that the higher the Tg of the latex film, the better the water whitening resistance. Atomic force microscope, surface element analysis, static water contact angle measurement, and attenuated total reflection–Fourier transform infrared were used to characterize the accumulation of the emulsifier on the surface of the latex film. It was found that the amount of emulsifier migrated to the surface of the latex film increased with the increase of the Tg of the latex film, that is, the amount of emulsifier remained inside the latex film decreased, thereby reducing its affinity to water. In addition, the higher the Tg of the latex film, the lower the water absorption, also reducing the affinity of the latex film to water. Both work together to improve the water whitening resistance of polyacrylate latex film with higher Tg. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48361. [ABSTRACT FROM AUTHOR]