热可逆自修复聚氨酯弹性体的制备及表征

为探究本征型自修复聚氨酯材料结构与性能的关系,平衡其自修复效率与强度之间的矛盾,采用六亚乙基二异氰酸酯(HDI)三聚体作交联剂,4,4-二氨基二苯二硫醚(AFD)作扩链剂,将可逆双硫键引入聚酯型聚氨酯弹性体中。研究发现:制备的自修复聚氨酯弹性体拉伸强度可达7.7MPa,在60℃,修复时间为24h的条件下,基于拉伸强度的自修复效率高达97.4%;而普通不含有双硫键(只含氢键作用)的弹性体拉伸强度为9.3MPa,在同等条件下的自修复效率为58.0%,表明双硫键的存在使得弹性体自修复效率在原来的基础上提高了67.9%。制备的弹性体具有多次自修复能力,其二次自修复效率为62.3%。     

具有自修复性能的纤维素纳米晶/聚氨酯复合材料的制备EI北大核心CSCD

在两步法制备聚氨酯弹性体的基础上,利用溶液共混的方法将纤维素纳米晶添加到热塑性聚氨酯弹性体中制备得到纤维素纳米晶/聚氨酯复合材料,并对复合材料的组成与结构、热力学及力学性能和自修复性能进行了表征。结果表明,与单纯的聚氨酯弹性体相比,纤维素纳米晶/聚氨酯复合材料表现出良好的力学性能,在纤维素纳米晶的质量分数为1%时,拉伸断裂强度和伸长率能够同时提高140%以上。同时,纤维素纳米晶/聚氨酯复合材料中存在的大量动态氢键赋予了材料优异的自修复性能,在50℃修复36h的样品断裂强度和伸长率分别可以达到5.4 MPa和1113%。     

具有自修复性能的纤维素纳米晶/聚氨酯复合材料的制备

在两步法制备聚氨酯弹性体的基础上,利用溶液共混的方法将纤维素纳米晶添加到热塑性聚氨酯弹性体中制备得到纤维素纳米晶/聚氨酯复合材料,并对复合材料的组成与结构、热力学及力学性能和自修复性能进行了表征。结果表明,与单纯的聚氨酯弹性体相比,纤维素纳米晶/聚氨酯复合材料表现出良好的力学性能,在纤维素纳米晶的质量分数为1%时,拉伸断裂强度和伸长率能够同时提高140%以上。同时,纤维素纳米晶/聚氨酯复合材料中存在的大量动态氢键赋予了材料优异的自修复性能,在50℃修复36h的样品断裂强度和伸长率分别可以达到5.4 MPa和1113%。     

MDI-50型聚氨酯弹性体材料合成及性能研究

利用MDI-50、聚醚多元醇和3,3′-二氯-4,4′-二氨基-二苯基甲烷(MOCA)扩链剂制备了MDI-50型聚氨酯弹性体,研究了游离异氰酸酯基质量含量、聚醚多元醇相对分子质量对MDI-50聚氨酯弹性体力学性能的影响,采用示差扫描量热分析(DSC)、热重分析(TG)、红外光谱(FTIR)及力学性能等测试方法对MDI-50型聚氨酯弹性体的结构及性能进行了表征和分析,并与TDI-80型聚氨酯弹性体相比较。结果表明:MDI-50型聚氨酯弹性体的综合性能明显优于TDI-80型。MDI-50型弹性体的硬度、撕裂强度和抗拉强度都随预聚体游离-NCO质量含量的提高而增大,随聚醚多元醇软链段相对分子质量增大而减小,而断裂伸长率相反。     

微孔聚氨酯弹性体材料水解稳定性研究

采用相同分子量的聚醚、聚酯和聚醚酯二元醇为原料分别制备密度为0．55g／cm3左右的微孔聚氨酯弹性体（MPUE）材料。并通过一系列测试对这三种微孔聚氨酯弹性体材料进行分析对比。结果发现聚醚型微孔聚氨酯弹性体材料的耐水解性能非常优异,聚酯型微孔聚氨酯弹性体材料的力学性能最好,聚醚酯型微孔聚氨酯弹性体材料的力学性能与聚酯型的力学性能接近,耐水解性能远优于聚酯型,近似于聚醚型。     

硬段结构对含二硫键自修复聚氨酯性能的影响

硬段结构的研究对指导制备兼顾力学性能与自修复性能的聚氨酯弹性体具有重要的意义。文中分别以4,4’-二苯基甲烷二异氰酸酯（MDI）、4,4’-二环己基甲烷二异氰酸酯（HMDI）、甲苯二异氰酸酯（TDI）、异佛尔酮二异氰酸酯（IPDI）及双（2-羟基乙基）二硫醚（HEDS）为硬段部分，聚己内酯二元醇为软段部分，制备了一系列含脂肪族二硫键的自修复聚氨酯，探究了不同异氰酸酯、硬段含量和扩链剂对其力学性能与自修复性能的影响。结果表明，对于异氰酸酯结构来讲，脂环族异氰酸酯制备的自修复聚氨酯具备更好的力学性能与自修复性能；对于脂环族异氰酸酯体系聚氨酯的硬段含量而言，一定范围越高，二硫键与氢键的含量也越高，越有利于材料的力学性能与自修复性能；对于扩链剂结构来讲，脂肪族二硫键主要是促进较高温度条件下的自修复性能，对于室温自修复性能起到的作用有限。     

热可逆自修复聚氨酯及其复合材料的研究进展

随着现代工业发展对材料性能的要求不断地提高，聚氨酯也正朝着智能化、功能化等方向发展，其中赋予聚氨酯材料自修复功能是推进其智能化方向的一个重要课题之一。目前自修复聚氨酯材料研究已取得一系列卓有成效的研究成果，其中在聚氨酯材料分子链主链引入热可逆Diels-Alder(DA)共价键以及在传统聚氨酯材料中引入纳米碳材料(如碳纳米管、石墨烯)成为研究热点。然而，目前热可逆DA反应的自修复聚氨酯还存在力学性能稍差、修复效率不高且修复效率随修复次数的增加迅速下降等问题，以及纳米碳材料需经改性才能引入等复杂工艺过程。从光可逆共价键修复体系和热可逆共价键修复体系两个方面简述本征型自修复体系，再从热可逆DA自修复聚氨酯体系和热可逆DA自修复聚氨酯复合材料体系两个方面综述国内外研究进展。     

具有热可逆性的自修复石墨烯量子点/聚氨酯透明复合膜研究

采用一步法制备具有热可逆性的透明自修复聚氨酯薄膜(PU-DA)。通过物理结合方式加入氨基修饰的石墨烯量子点(NH₂-GQDs),最终制备出具有热可逆性的自修复石墨烯量子点/聚氨酯透明复合膜(NH₂-GQDs/PU-DA)。采用傅里叶红外光谱仪、偏光显微镜和万能拉力机等手段进行结构和性能的分析。结果表明:通过热可逆反应(Diels-Alder)键的引入,可使聚氨酯薄膜在一定温度下具有自修复性能的同时,仍保持较好的柔韧性,拉伸强度和断裂伸长率最优分别达到1.437MPa和117.4%。通过应力-应变测试发现,NH₂-GQDs的加入在一定程度上增强了聚氨酯薄膜的力学性能,并改善了聚氨酯薄膜的疏水性。     

HTPB型聚氨酯弹性体的改性研究

采用预聚体法制备了端羟基聚丁二烯(HTPB)型聚氨酯弹性体,并采用了化学改性的方法对HTPB型聚氨酯弹性体进行了改性研究.结果表明:以分子量为3100的HTPB作软段,2,4-甲苯二异氰酸酯(TDI)作硬段,预聚体中-NCO的含量控制在4.5%～5.0%之间,双酚A型环氧树脂(E-51)占25%时,弹性体材料的力学性能和耐水性能最好.     

高强度自修复聚氨酯弹性体的制备及性能

针对自修复材料力学性能和自修复性难以兼顾的问题,采用传统预聚体法,引入含双硫结构的交联剂,制备得到既具有一定力学强度、又具有良好自修复性的聚氨酯弹性体。采用红外光谱进行化学结构表征;采用邵氏硬度计进行硬度测定;采用万能力学试验机考察了不同条件下的自修复效率;通过三维视频显微镜和拍照记录弹性体自修复过程;采用热重分析仪对样品进行热性能表征。结果表明,双硫键被成功引入弹性体中,弹性体邵氏硬度大多可达50 HA以上。升高温度和延长时间都能提高弹性体的自修复效率:24 h时,自修复效率从25 ℃的31.3%升高到80 ℃的99.5%;在80 ℃下,自修复效率从2 h的48.4 %提高到24 h的99.5%。双硫交联剂质量分数的增加也有利于自修复,弹性体的自修复效率从PUSS 3的54.5%提高到PUSS 6的99.5%。热重分析显示,弹性体的热稳定性随双硫质量分数的增加而略有下降,但所有弹性体的5%热失重温度都高于265.0 ℃。     

Preparation of Robust,Room-Temperature Self-Healable and Recyclable Polysiloxanes Based on Hierarchical Hard Domains

The contradiction between high mechanical strength and mild healing conditions has long existed in self-healing materials, which limits the application of self-healing materials. The preparation of robust materials with excellent healing performance under mild conditions can effectively reduce resource waste and environmental pollution. Herein, self-healing polysiloxane elastomer materials, APDMS-MDI-IPDI-Bs, based on microphase separation strategy are reported. Through the synergistic effect of the designed urea hydrogen bond and the nitrogen-coordinated boroxine structure, the materials can maintain high mechanical properties (maximum tensile strength up to 3.35 MPa, elongation at break up to 316%), while maintaining excellent self-healing and recyclable ability (24 h healing efficiency at room temperature can reach 94.77 ± 3.23%), and the performance can be repeated many times without decay. APDMS-MDI-IPDI-Bs also exhibit unique hydrophobicity, expanding the application scenarios of materials containing boroxine structure.     

Colorless,Transparent, Robust,and Fast Scratch‐Self‐Healing Elastomers via a Phase‐Locked Dynamic Bonds Design

Robust self‐healing thermoplastic elastomers are expected to have repeated healing capability, remarkable mechanical properties, transparency, and superior toughness. The phase‐locked design in this work provides excellent tensile mechanical properties and efficient healability at a moderate temperature due to the dynamic disulfide bonds embedded in the hard segments and mainly being locked in the viscoelastic hard microphase region. The self‐healing elastomers exhibit a maximum tensile stress of 25 MPa and a fracture strain of over 1600%, which are quite prominent compared to previous reports. The nanoscale domains of the elastomer are smaller than the wavelength of visible light by microphase separation control resulting in colorless, nearly 100% transparency, and are as good as quartz glasses. The high dynamics of the phase‐locked disulfide bonds renders a high healing efficiency of scratches on the surface within 60 s at 70 °C. The rapid scratch healing and complete transparency recovery of the elastomers provide new avenues in the highly transparent surface or protective films which finds potential applications for precision optical lenses, flexible display screens, and automobile or aircraft lighting finishes.     

Surface Modification of Transition Metal Dichalcogenide Nanosheets for Intrinsically Self-Healing Hydrogels with Enhanced Mechanical Properties

Nanocomposites with enhanced mechanical properties and efficient self-healing characteristics can change how the artificially engineered materials’ life cycle is perceived. Improved adhesion of nanomaterials with the host matrix can drastically improve the structural properties and confer the material with repeatable bonding/debonding capabilities. In this work, exfoliated 2H-WS₂ nanosheets are modified using an organic thiol to impart hydrogen bonding sites on the otherwise inert nanosheets by surface functionalization. These modified nanosheets are incorporated within the PVA hydrogel matrix and analyzed for their contribution to the composite's intrinsic self-healing and mechanical strength. The resulting hydrogel forms a highly flexible macrostructure with an impressive enhancement in mechanical properties and a very high autonomous healing efficiency of 89.92%. Interesting changes in the surface properties after functionalization show that such modification is highly suitable for water-based polymeric systems. Probing into the healing mechanism using advanced spectroscopic techniques reveals the formation of a stable cyclic structure on the surface of nanosheets, mainly responsible for the improved healing response. This work opens an avenue toward the development of self-healing nanocomposites where chemically inert nanoparticles participate in the healing network rather than just mechanically reinforcing the matrix by slender adhesion.     

催化剂对异佛尔酮二异氰酸酯制备的脂肪族聚氨酯弹性体结构和性能的影响

采用一步法通过异佛尔酮二异氰酸酯与聚丙二醇和1,4-丁二醇反应合成了脂肪族聚氨酯（PU）弹性体。考察了催化剂的种类和含量对PU弹性体结构和性能的影响。结果表明,以辛酸亚锡为催化剂时,PU弹性体的软段相和硬段相间的相分离程度最明显且分子量最低,导致其力学性能最差;以辛酸铋为催化剂时,PU弹性体软段相和硬段相的相容性较好且...     

Characterization of solvent-filled polyurethane/urea–formaldehyde core–shell composites

Encapsulation of liquid phases is a crucial step in many self-healing material systems where a healing agent has to be protected during processing and then released during a damage event. In this work, the mechanical properties of polyurethane (PU) reinforced urea–formaldehyde (UF) shells are characterized. It was found that shell thickness is both a function of PU content in the core phase and of the microcapsule diameter. Furthermore, a saturation thickness was found for high PU contents or high capsule diameters and this phenomenon had direct implications on the bursting force under compression of single microcapsules. With help of an analytical model, the Young's modulus of the hybrid PU/UF was determined and in general, PU-reinforced shells had a lower modulus but higher ductility in terms of elongation at break, leading to more resistant microcapsules overall.     

Mechanical properties of a self-healing fibre reinforced epoxy composites

Inspired by biological systems in which damage triggers an autonomic healing response, a polymer composite material that can heal itself when cracked has been developed. In this work, compression and tensile properties of a self-healed fibre reinforced epoxy composites were investigated. Microencapsulated epoxy and mercaptan healing agents were incorporated into a glass fibre reinforced epoxy matrix to produce a polymer composite capable of self-healing. The self-repair microcapsules in the epoxy resin would break as a result of microcrack expansion in the matrix, and letting out the strong repair agent to recover the mechanical strength with a relative healing efficiency of up to 140% which is a ratio of healed property value to initial property value or healing efficiency up to 119% if using the healed strength with the damaged strength.     

基于动态化学键构建自愈合高分子水凝胶

高分子水凝胶是一种具有三维网络结构的软材料,能够吸收并保持大量的水分。高分子水凝胶具有良好的生物相容性和力学性能,在生物医学和生物工程领域具有重要的应用价值。自愈合水凝胶是一种能够响应外界刺激并修复自身损伤的智能凝胶。相比传统水凝胶,自愈合水凝胶具有修复损伤的特性,近年来受到科学界的广泛关注。基于动态化学的自愈合水凝胶是一种能够通过动态的共价键或非共价键交联而重新形成三维网络结构从而修复损伤的新型自愈合水凝胶,该水凝胶能够快速多次地修复自身损伤,有良好的环境适应性,为开发多功能智能新材料奠定了基础。本文综述了近年来基于动态化学键构建自愈合水凝胶的研究进展,重点阐述了基于氢键相互作用、金属配位相互作用、主-客体相互作用、离子相互作用、亲疏水相互作用、亚胺键/酰腙键、硼酸酯键和二硫键的自愈合水凝胶的最新研究情况,同时提出了自愈合水凝胶的一些问题,并分析了未来的发展方向。     

Novel system with damage initiated autonomous healing property based on heterogeneous blends of ethylene-methacrylic acid ionomer

Self-healing behavior of ionomer blends containing both rapidly crystallizing phase and with higher amount of amorphous phase has not yet been studied. This work gives a new insight to understand the development of materials with intrinsic self-healing property. In particular, binary blends based on poly(ethylene-co-methacrylic acid sodium salt) (EMNa)/Poly(vinyl alcohol-co-ethylene) (EVA) and epoxidized natural rubber (ENR), were studied by ballistic puncture tests. In the composition range explored (15-50 wt.% of EVA and ENR), the self-healing characteristics decrease with the increasing amount of EVA but are maintained in all ranges for ENR/EMNa blends. The ballistic damage initiated autonomous healing was observed by optical microscopy and the healing was further analyzed by thermal and mechanical behaviors of the blend materials.