硬段含量对嵌段聚脲结构与性能的影响

以端氨基聚醚、异佛尔酮二异氰酸酯(IPD I)、二乙基甲苯二胺(DETDA)为主要原料,制备了一组硬段含量不同的IPD I基聚脲。通过FT-IR、DSC、SEM以及拉伸等测试手段,研究了硬段含量对聚脲羰基氢键化程度、微观结构及其力学性能的影响。结果表明:随着硬段含量的增加,脲羰基氢键化程度增加;软段相的微相分离率降低,硬段有序程度增大。硬段含量为35%时材料的力学性能较佳。     

Blast Resistance of 240 mm Building Wall Coated with Polyurea Elastomer

Enhancing the blast resistance of building walls is a research hotspot in the field of anti-terrorism and explosion protection. In this study, numerical simulation and experimental verification were combined to analyze the failure phenomenon of brick masonry wall and sprayed polyurea-reinforced brick wall under contact explosion and determine the failure response parameters of the wall. The failure limit, mode, and mechanism of a 240 mm wall without reinforcement and strengthened with polyurea elastomer under different strength loads were investigated. Under contact explosion, the increase in the size of the blasting pit of the 240 mm wall gradually slowed down after the dose was increased to higher than 0.5 kg. Thereafter, the energy of the explosive load was released by splashing wall fragments as well as by deflecting and movement of the wall. The results show that the 240 mm walls sprayed with polyurea elastomer had outstanding anti-explosion performance because it wraps the damaged area and fragments of masonry wall inside the polyurea layer. When the thickness of the polyurea layer increases to 8 mm, the damaged area of the masonry wall decreases by 55.6% compared with that without reinforcement. The numerical simulation results were in good agreement with the experimental results.     

Investigation of alternative compounds to poly(E-MA) as a polymeric surfactant for preparation of microcapsules by phase separation method

Various water-soluble polymers were used to examine an alternative emulsifier for poly(ethylene-alt-maleic anhydride), used in the preparation of crosslinked polyurea microcapsules. Microcapsules were successfully prepared by using the water-soluble polymers with large molecular weight alternating copolymers, namely poly(olefin-maleic anhydride), poly(olefin-maleic acid), and poly(acrylic acid). On the other hand, no microcapsule resulted from olefin-maleic acid with small molecular weight alternating copolymers. From these results, the following guidelines were obtained for the selection of polymeric surfactants suitable for crosslinked polyurea microcapsule. A polymeric surfactant must have maleic acid or a carboxyl group in order to form a crosslinked polyurea microcapsule membrane. Furthermore, to form a stronger capsule membrane it is desirable to have a maleic anhydride group. It is also important for membrane formation that the polymeric surfactant has a suitable molecular weight.     

Flame Retardancy Properties and Physicochemical Characteristics of Polyurea-Based Coatings Containing Flame Retardants Based on Aluminum Hydroxide,Resorcinol Bis(Diphenyl Phosphate), and Tris Chloropropyl Phosphate

Polyurea is a synthetic material made by the reaction of isocyanate and polymer blend-containing amines. Due to its outstanding mechanical properties and fast curing, polyurea-based coatings have found dozens of applications, including waterproofing and anti-corrosion coatings. Further development of this material can create a flame-retardant product, a good alternative for common products available on the market, such as intumescent coatings. To improve the flame retardancy of polyurea, several flame retardants were investigated. The influence of aluminum hydroxide, resorcinol bis(diphenyl phosphate) (RDP), and tris chloropropyl phosphate (TCPP) on flame retardancy and morphology was studied. The following methods were used: infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, limiting oxygen index, and tensile strength. The examinations mentioned above showed the improvement of flame-retardancy of polyurea for two products: chlorinated organophosphate and organophosphate. Nevertheless, using the chlorinated organophosphate additive caused a rapid deterioration of mechanical properties.     

可用于智能防腐涂层的聚脲微球的制备与应用

以甲苯二异氰酸酯(TDI)和二胺类单体为原料,通过油包水(W/O)反相细乳液的界面加成聚合反应,成功制备了包覆苯并三氮唑(BTA)的中空聚脲微球。通过透射电子显微镜(TEM)和差示扫描量热法(DSC)分别对聚脲微球的形貌和热敏性进行表征。结果表明,缓蚀剂BTA可被有效地包覆在中空微球中,当温度改变或紫外光照射时,含偶氮键纳米微球发生降解,BTA能及时释放出来。通过电化学阻抗谱和Tafel曲线分析法对复合涂层的电化学性能进行的研究表明,负载BTA的中空聚脲微球能提高涂层的防腐蚀性能。     

Preparation of Polyurea Microcapsules by Interfacial Polymerization of Isocyanate and Chitosan Oligosaccharide

(2-((1-(4-chlorophenyl)-1H-pyrazol-3-yl)oxy)-N-(3,4-dichlorophenyl)-propanamide) is a new oil-soluble compound with good fungicidal activity against Rhizoctonia solani. Chitosan oligosaccharide (COS) is the depolymerization product of chitosan and can be developed into biological pesticides, growth regulators, and fertilizers due to its various bioactivities. COS is an oligomer of β- (1 → 4)-linked d –glucosamine and can be taken as a polyamine. In this study, microcapsules were prepared by interfacial polymerization of oil-soluble methylene diphenyl diisocyanate and water-soluble COS. The effects of several key preparation parameters, e.g., emulsifier dosage, agitation rate during emulsification, and core/shell ratio, on properties of the microcapsules such as the encapsulation efficiency, particle size, and size distribution were investigated. The microcapsules were characterized by infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy, etc., and the encapsulation efficiency and release behaviors were investigated. The results show that the microcapsules have a smooth surface and 93.3% of encapsulation efficiency. The microcapsules showed slow-release behavior following a first-order kinetic equation, and the accumulative release rates of the microcapsules with core/shell mass ratios of 8.0/4.0, 8.0/5.0, and 8.0/6.0, were 95.5%, 91.4%, and 90.1%, respectively, on day 30. Due to many high biological activities, biodegradability, and the pure nature of COS, microcapsules formed from COS are promising for applications in controlled release of pesticides, growth regulators, and fertilizer.     

Synthesis and Characterization of New Polyurea Elastomers by Sol/Gel Chemistry

A series of elastomers based on polyurea chemistry is synthesized by crosslinking amino‐terminated polyethers with a triisocyanate using an appropriate solvent, which slowed down the reactivity of the amino groups. Control of the reactivity allows the shaping of the material, and films of defined thickness can be achieved for mechanical testing. The strength of the final network can be tuned by the crosslinking density of the network chemical constitution. The resulting materials show a good thermal stability and promising mechanical enhancement.

     

Effect of the PSSMA Content on the Heat Transfer Performances of Polyurea Nano-Encapsulated Phase Change Materials

Polyurea nano-encapsulated phase change materials (PUA-NEPCMs) were prepared from an n-octadecane core and through the formation of amide bonds by the reaction of toluene 2,4-diisocyanate and poly(4-styrenesulfonic acid-co-maleic acid) sodium salt (PSSMA), followed by the subsequent formation of a PUA shell using a miniemulsion system. The effects of the synthetic conditions on the thermal properties and encapsulat ion effect of the NEPCMs were systematically investigated. Differential scanning calorimetry (DSC) revealed that the melting enthalpy and encapsulation efficiency of the PUA-NEPCMs prepared under optimal conditions reached 123.00 J/g and 54.27%, respectively. Although previous results suggested that the introduction of PSSMA results in a reduced heat transfer performance for NEPCMs, DSC analysis of the prepared PUA-NEPCMs showed that increasing PSSMA contents enhanced the heat transfer performance due to a decrease in the degree of supercooling. Our results could therefore lead to further enhancements in the heat transfer performance of PUA-NEPCMs, in addition to expanding their field of application.     

Influence of Polyurea Coatings on Low-Longitudinal-Reinforcement-Ratio Reinforced Concrete Beams Subjected to Bending

“Polyurea coatings as a possible structural reinforcement system” is a research investigation that aims to explore the possible applications of polyurea coatings for improving structural performance (including steel, concrete, timber and other structures used in the construction industry). As part of the research in this field, this paper focuses on evaluating the performance of bending polyurea-coated reinforced concrete (RC) beams with a low reinforcement ratio. The easy application and numerous advantages of polyurea can prove very useful when existing RC structural elements are repaired or retrofitted. Laboratory tests of RC beams were performed for the purpose of this paper. The failure mechanisms and cracking patterns of these specimens are described, and their bending strengths were compared. On this basis, the effect of the coating on bending strength and the performance of the reinforced beams at the serviceability limit state (SLS) was examined and analyzed. The results showed that the use of a polyurea coating has a positive impact on the cracking and deflection state of RC beams and makes it possible to safely use RC elements on a continuous basis under high levels of load.     

Ballistic Performance of Polyurea-Reinforced Ceramic/Metal Armor Subjected to Projectile Impact

Although polyurea has attracted extensive attention in impact mitigation due to its protective characteristics during intensive loading, the ballistic performance of polyurea-reinforced ceramic/metal armor remains unclear. In the present study, polyurea-reinforced ceramic/metal armor with different structures was designed, including three types of coating positions of the polyurea. The ballistic tests were conducted with a ballistic gun; the samples were subjected to a tungsten projectile formed into a cylinder 8 mm in diameter and 30 mm in length, and the deformation process of the tested targets was recorded with a high-speed camera. The ballistic performance of the polyurea-reinforced ceramic/metal armor was evaluated according to mass efficiency. The damaged targets were investigated in order to determine the failure patterns and the mechanisms of interaction between the projectile and the target. A scanning electron microscope (SEM) was used to observe the microstructure of polyurea and to understand its failure mechanisms. The results showed that the mass efficiency of the polyurea-coated armor was 89% higher than that of ceramic/metal armor, which implies that polyurea-coated ceramic armor achieved higher ballistic performance with lighter mass quality than that of ceramic/metal armor. The improvement of ballistic performance was due to the energy absorbed by polyurea during glass transition. These results are promising regarding further applications of polyurea-reinforced ceramic/metal armor.