Summary: The reaction between octaaminophenyl polyhedral oligomeric silsesquioxane (OAPS) and 2,2′‐(1,3‐phenylene)‐bis(4,5‐dihydro‐oxazoles) (PBO) over different temperature ranges was confirmed by FT‐IR spectroscopy. The OAPS was used to modify benzoxazine (BZ) in the presence of PBO. The novel polybenzoxazine (PBZ)‐PBO/OAPS hybrid nanocomposite was prepared by solvent methods. Dynamic mechanical analyses indicated that the nanocomposites exhibited much higher Tg values than the pristine PBZ and PBZ‐PBO resin, and the storage modulus of the nanocomposites was maintained at higher temperatures, although only a small amount of OAPS was incorporated into the systems. Dynamic thermogravimetric analysis showed that the thermal stability of the hybrid was also improved by the inclusion of OAPS.DMA of PBZ (a), PBZ‐PBO (b), and PBZ‐PBO/OAPS nanocomposites (c–e).magnified imageDMA of PBZ (a), PBZ‐PBO (b), and PBZ‐PBO/OAPS nanocomposites (c–e).

In this contribution, castor oil polyols with functionality of f = 2.7 and f = 2 are used as soft segments (SS) for synthesizing polyurethane elastomers (PUEs) without addition of petroleum‐based polyol. The effect of molar ratio of castor oil polyols on structure and properties of PUEs has been investigated by Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis, X‐ray diffraction, tensile, swelling, and water absorption tests. The results reveal that hydrogen bonding mainly exists in hard segments (HSs) and weakens with decreasing the molar percentage of castor oil polyol (f = 2.7) in SS. T g of SS decreases while T g of HS remains constant as molar percentage of castor oil polyol (f = 2.7) decreased. The initial degradation temperatures (T5%) are above 300 °C and independent of the molar ratio of castor oil polyols. However, the temperature at 50% weight loss (T50%) decreases significantly as molar percentage of castor oil polyol (f = 2.7) decreased. Moreover, PUEs exhibit very low water absorption rate, <1%, after immersing in water for 140 h at room temperature. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47309.

Hydrolytic stability is an essential requirement for polyurethanes (PUs) that are used in highly humid and aqueous environments. In this study, hydrolysis‐resistant PU elastomers (PUEs) are synthesized based on hydrophobic bio‐based polyfarnesene diol (PFD), which contains unique “bottle brushes” structure (with long branched hydrocarbon side chains). The effect of hard segment (HS) content, ranging from 30 to 50%, on the morphology and properties of PUEs is investigated by Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, X‐ray diffraction, scanning electron microscopy, tensile, water absorption, and contact angle measurements. The results show that there are prominent phase separations in the synthesized PUEs. The PUEs show a three‐stage degradation process and two Tg, one is at about −66 °C and the other 61 °C, which are related to the soft segment and HS, respectively. Water contact angles of PUEs increase from 98.6 to 105.2° with the increasing of PFD structural unit fraction. After being immersed in deionized water for 30 days, PUEs show no significant degradation of both tensile strength and elongation at break, and mass changes of all samples are less than 0.5%. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47673.

Biodegradable body temperature‐responsive shape memory polyurethanes, with self‐healing function, were synthesized here from PCDL, MDI and different chain extenders, in which the chain extenders are designed to adjust their transition temperatures and shape memory properties. Once deformed at proper temperature, they show more than 96% shape fixation until heated near body temperature, where they recover their original shape (100%) within 20 s. Moreover, these polyurethanes could be self‐healing at proper temperature, which makes them available in many medical fields. POLYM. ENG. SCI., 59:E310–E316, 2019. © 2019 Society of Plastics Engineers

No abstract

No abstract

In this study, we aim to propose a collision-free model on the interaction between pedestrians and cyclists on a shared road. First, we design an experiment to investigate the behaviors of pedestrians and cyclists in the interaction process. Three principles are presented for modeling based on the experimental observations, including the perception difference in the bidirectional and unidirectional scenarios, the difference in sensitivity on safety distance of pedestrians and cyclists, and the effect of distance and moving direction on the deceleration and steering behaviors. The model is proposed under the concept of subjective perception and behavioral decision-making. The heuristic of the path decision is that if a pedestrian (cyclist) decides to detour, he/she prefers the shortest route on the premise that a minimum safety distance is kept from the cyclist (pedestrian). The speed adjustment of both pedestrians and cyclists includes two parts: the expected speed determined by the available headway distance, and the deceleration coefficient determined by the distance between the cyclist and the pedestrian for the safety concern. The direction-related parameters are calibrated directly through the trajectories, while the speed-related parameters are calibrated with the cross-entropy method. The microscopic validation implies that the proposed collision-free model can potentially be used to simulate the microscopic interaction between pedestrians and the cyclist. It is also worth noting that the perception uncertainty of pedestrians could generate a big challenge to physical models on simulating the microscopic behaviors of pedestrians when the potential collision comes from the behind. The simulation of the mixed traffic reveals the difference in lane formation phenomena and the consequential conflict intensity between a cyclist and the crowd in bidirectional and unidirectional situations.

No abstract