Thermoplastic polyurethane composites (TPCs) in kilogram scale reinforced with monodispersed functionalized graphene (FGr) are prepared by melt-blending on industrial extruder and their properties are studied in this work. It shows that the saturation content of monodispersed FGr in TPCs is ≈0.5 wt%, beyond which part of it will agglomerate. The multiple effects of monodispersed FGr-micro-crosslinking, isolation, and induced crystallization-have great impact on the properties of TPCs. With the content increase of FGr, the melt rheological properties, crystallization properties, mechanical properties, and shape memory properties of TPCs show regular changes. More importantly, the tensile fracture behaviors of TPCs are dramatically changed by FGr. Some microfibers with high strength are formed and lay astride the cracks to prevent crack propagation during the damage process. Therefore, the tensile strength of TPC with 0.5 wt% FGr is maximumly improved, showing an increase of 139% compared to neat thermoplastic polyurethane. Its shape fixed ratio and shape recovery ratio are respectively raised to 96% and 94%, showing a good shape memory performance.
Self-healing polyurethanes (PUs) with disulfide bonds and diphenyl silicon groups involved in the soft phases were prepared and studied in this work. The self-healing efficiencies of PUs are greatly improved by the synergistic effect of diphenyl silicon groups with low surface energy-increasing the distance between two polymer chains, enhancing the mobility of polymer chains, and promoting the migration of sulfur-containing groups to the damaged sites. The analysis of activation energy for the movement of polymer chains based on dynamic mechanical thermal analysis shows that, the higher contents of disulfide bonds and diphenyl silicon groups, the stronger mobility of polymer chains, and the higher self-healing performance of PUs. The study of temperature and time dependencies for the healing process at damaged sites indicates that it is composed of the recombination of disulfide bonds and the interpenetration and intertwining of polymer chains. The former can be completed in a shorter time, while the latter in a longer time. Sufficient time of heat treatment at relatively high temperature is necessary to get high self-healing efficiency. This strategy and the relative results are instructive to design and development of self-healing PUs.
In the renewal of old industrial areas, residents' life has been affected. In order to explore the relationship between residents' sense of place and their attitude towards the future development direction, this study takes Xiangfang old industrial area as an example and conducts a field questionnaire survey. The calculation of Structural Equation Model shows that residents' sense of place can be divided into place attachment, place dependence and place identity in Xiangfang old industrial area, and the intensities are high. Moreover, the logistic regression shows that sense of place significantly impacts History and Environment preference. Place dependence and place attachment significantly impact History preference. And place identity is the only dimension that is significant to all types of preferences. These conclusions show the importance of a sense of place, especially place identity, in public participation. This study can help the urban renewal of Xiangfang old industrial zone and proves that sense of place can provide a way for the public to participate in planning decision-making and policy-making in the future.
Human activities are the primary source of energy consumption and CO2 emissions. Adopting low-carbon behaviors (LCBs) can effectively reduce carbon emissions, which in turn helps alleviate environmental problems. Previous research shows that low-carbon policies can promote LCBs, while an extensive understanding of the effects of multi-types of low-carbon policies on various LCBs needs to be verified. Analyses on influencing factors regarding LCBs are dominated before, and place attachment and low-carbon behavioral intention as the influencing factors of LCBs, their relationship with low-carbon policy and LCBs needs to be clarified. By taking a questionnaire survey of residents of Hangzhou, China, this study presents a conceptual framework capable of analyzing the relationship between three types of low-carbon policies, including information policy, economic policy, and administrative regulations, and two types of LCBs, including low-carbon consumption (LCCB) and travel (LCTB) behavior, considering the mediation effect of place attachment and low-carbon behavioral intention in a single structural equation model. The results illustrate that administrative regulations and information policy have a direct positive impact on LCCB, and information policy has the most significant influence. Economic policy and administrative regulations directly impact LCTB, and administrative regulations have the most significant influence. The influence of administrative regulations on LCTB is more excellent than on LCCB. Information policy indirectly affects two types of LCBs through the chain mediation effect of place attachment and low-carbon behavioral intention. The results should be helpful to low-carbon policymakers seeking to promote LCBs to consider the importance of place attachment and various low-carbon policies. Moreover, they enrich our understanding of the influencing mechanism of LCBs.
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