No abstract

A systematic investigation on the volumetric expansion of four benzoxazine systems, which are benzoxazine, benzoxazine/tertiary amine, benzoxazine/organic acid, and benzoxazine/epoxy resin/tertiary amine, was done. By using gravitometric and dilatometric methods, etc., studies on volumetric shrinkage, isothermal cure shrinkage, and density versus cure time plots were done. The cure reactions of these benzoxazines were carried out at 140 and 160°C. The results show that all benzoxazine systems exhibit apparent volumetric expansion after polymerization, that is, the densities of monomers are larger than are those of polymers at room temperature. But, meanwhile, they exhibit volumetric shrinkage while curing isothermally. The results also show that the higher the cure temperature is, the larger the cure shrinkage of the benzoxazines will be and that the extent of the cure shrinkage of the benzoxazines with the aid of catalysts is larger than is that of thermal polymerization systems. The reason for this is that, accelerated by catalysts, the polymerization rate become faster and the extent of polymerizatiom becomes larger. It is obvious that catalysts can make a notable impact on the cure reaction of benzoxazines. Therefore, the dimension of the volumetric expansion of benzoxazine is associated with its polymerization mechanism, molecular structure, and extent of polymerization.

Graphene serves as the most disruptive material in the twenty-first century and plays an unsubstitutable role in solving the sustainable development problems of energy crises, water shortages, and environmental pollution. Recently, obtaining a sustainable competitive advantage (SCA) in the field of graphene has gained increasing attention from both researchers and practitioners. However, few attempts have been made to summarize the SCA of this field by applying patent information. Basing on a patent-based multi-level perspective (MLP), this study aims to develop an approach to identify SCA in the target technological area by conducting a patent review from the comprehensive perspectives of the macro landscape, meso socio-technical system, and micro niches, and then integrate patent analysis with technology life cycle (TLC) theory to examine patents involving global technological competition. The effectiveness of the approach is verified with a case study on graphene. The results show that the graphene field is an emerging and fast-growing technological field, with an increasing number of patents over the year. The TLC of graphene technology demonstrated an approximate S shape, with China, the U.S., Korea, and Japan filing the largest number of graphene patents. Evidenced by Derwent Manual Codes, we found an increase in consideration given to technological application and material preparation topics over time, and research hotspots and fronts that have SCA. In terms of a leading country or region with SCA, the U.S., with a high foreign patent filing rate, large number of high forward citation patents, strong assignees’ competitive position, and large number of high-strength patents, was still the most powerful leader, with a higher SCA in the graphene industry. Korea also obtained a relatively higher SCA and will be a promising competitor in this field. Although China was shown to be catching-up very rapidly in the total number of graphene patents, the apparent innovation gaps in the foreign patent filing rate, high value patents, and Industry-University-Research Collaboration will obviously hamper Chinese catch-up efforts for obtaining SCA. As for patentees, the most powerful leaders with a higher SCA represented by Samsung Electronics Co., Ltd, International Business Machines Corp, and Nanotek Instruments Inc were identified. In addition, most of the high strength patents were owned by the above patentees. Further, valuable contributions to the understanding of SCA in graphene technology were summarized. First, the proposed patent-based MLP provides a new and comprehensive analytical framework for review research, as well as SCA analysis, and extends its research perspectives. Second, it introduces patent indicators to the previous MLP model, and provides a new theoretical perspective for the study of technological innovation in the previous MLP model. Third, this paper employs the TLC theory to explore the dynamic SCA in the given technology field, which further develops the concept of the MLP model from the temporal dimension. Finally, future research directions were demonstrated. To the best of the authors’ knowledge, this is the first systematic review of this field using patent analysis, comprehensively acknowledging the current technological competition and development in the graphene field and that of the future, and can be applied to various other emerging technology fields.

A novel silica (SiO2)/n-tetradecane microencapsulated phase change material (MEPCM) was synthesized by in situ interfacial polycondensation. The influences of the amount of the composite emulsifier and the mass ratio of n-tetradecane and tetraethyl silicate on the MEPCM performance were systematically investigated. The morphology, chemical structure, and composition of the MEPCM were characterized by scanning electron microscopy and energy dispersive X-ray spectrometer, Fourier transform infrared spectroscopy, and X-ray diffraction, and its thermal performance and thermal stability were measured by differential scanning calorimetry and thermogravimetric analysis. The results showed that the n-tetradecane core material was successfully encapsulated by silica shell material with encapsulation ratio of 62.04%. The MEPCM had a melting enthalpy of 140.5 kJ kg–1 and thermal conductivity of 0.139 W m–1 K–1. Because of its excellent thermal performance and thermal stability, silica/n-tetradecane MEPCM displays a good potential for cold energy storage.