Nanocomposite Hydrogels with High Mechanical Strength and High Swelling Ratio by RAFT Polymerization

Nanocomposite hydrogels (NC gels) have been prepared based on poly(N-isopropylacrylamide) (PNIPAM) containing 0.25-15 wt% of the expandable synthetic hectorite Laponite XLS (Clay-S) by reversible addition fragmentation chain transfer (RAFT) polymerization. The swelling behaviors were investigated and the hydrogels by RAFT polymerization (RAFT gels) showed accelerated shrinking kinetics and higher swelling ratio comparing with conventional hydrogels (CGel). This could be attributed to the presence of dangling chains mainly caused by chain transfer reagent (CTA), which could retard the crosslinking reaction rate greatly. Furthermore, the NC gels have stronger mechanical strength than CGel. The presence of Clay-S does not affect the value of the lower critical solution temperature (LCST).     

通过RAFT聚合方法合成具有高强度和高溶胀率的纳米水凝胶

为了得到具有高强度和高溶胀率的纳米水凝胶(NCgels),N-异丙基丙烯酰胺通过可逆加成断裂链转移(RAFT)聚合的方法,插层在含有质量分数为0.25%～15%的可扩展的有机化的蒙脱土(Clay-S)层间并交联。结果表明,与传统水凝胶相比,该水凝胶的强度和溶胀性能得到了很大提高,并且对温度的变化具有较快的响应速率。以质量分数为5%的蒙脱土,链转移剂的质量分数为0.5%制备的纳米水凝胶为例,该水凝胶在20℃的溶胀率为450,而传统水凝胶在相同温度时的溶胀率仅为20;该水凝胶在1min内失去75%的水,在4min内失去约90%的水,而传统水凝胶在15min内仅失去66%左右的水。     

碳纳米管补强丁腈橡胶的性能研究

研究碳纳米管用量对丁腈橡胶(NBR)性能的影响。结果表明:随着碳纳米管用量的增大,胶料的最小和最大转矩增大,焦烧时间和正硫化时间缩短;硫化胶的100%和300%定伸应力增大,拉伸强度和撕裂强度先增大后减小,高温拉伸性能保持率总体增大,耐热和耐磨性能提高;加入6份碳纳米管,硫化胶的储能模量在温度较低时减小,损耗因子峰值减小。扫描电镜分析显示,碳纳米管在NBR中整体分散均匀,局部存在团聚现象。     

Study on Preparation and Properties of HVBR Reinforced with Si69-modified Carbon Nanotubes

Si69-modified CNTs/HVBR nanocomposites were prepared in dependence of different loadings of Si69-modified CNTs fabricated by mixing acid-treated CNTs with Si69 in toluene. FT-IR analysis illustrated the successful modification of CNTs. Experimental results showed that the Si69-modified CNTs could more significantly enhance the mechanical strength and thermal conductivity of the composites than the unmodified CNTs, indicating the Si69-modified CNTs could be more uniformly dispersed in the HVBR matrix, which was also verified form the SEM results. The DMA results indicated that the incorporation of Si69-modified CNTs could remarkably increase the glass transition temperature and decrease the height of the tanδ peak.     

Poly(vinyl alcohol)–Carbon Nanodots Fluorescent Hydrogel with Superior Mechanical Properties and Sensitive to Detection of Iron(III) Ions

A high‐strength fluorescent hydrogel is prepared by physical cross‐linking of carbon nanodots (CNDs) with poly(vinyl alcohol) (PVA). The stretching and compression of the PVA hydrogel are improved with CNDs by 176% and 64%, respectively. It still has excellent self‐healing behaviors without adding other healing agents. In addition, the search for rapid detection of heavy metals is still a huge challenge. The resulting hydrogel exhibits fluorescence quenching in the presence of Fe³⁺ by the fluorescence characteristics of CNDs, which has high selectivity and sensitivity. The PVA‐CNDs fluorescent hydrogel can be used as a solid detection platform for Fe³⁺, where the detection limit is found to be 10 µm for Fe³⁺ by fluorescence studies.     

Ultrastretchable,Super Tough,and Rapidly Recoverable Nanocomposite Double‐Network Hydrogels by Dual Physically Hydrogen Bond and Vinyl‐Functionalized Silica Nanoparticles Macro‐Crosslinking

It remains a challenge to develop tough hydrogels with recoverable or healable properties after damage. Herein, a new nanocomposite double‐network hydrogel (NC‐DN) consisting of first agar network and a homogeneous vinyl‐functionalized silica nanoparticles (VSNPs) macro‐crosslinked polyacrylamide (PAM) second network is reported. VSNPs are prepared via sol‐gel process using vinyltriethoxysilane as a silicon source. Then, Agar/PAM‐SiO₂ NC‐DN hydrogels are fabricated by dual physically hydrogen bonds and VSNPs macro‐crosslinking. Under deformation, the reversible hydrogen bonds in agar network and PAM nanocomposite network successively break to dissipate energy and then recombine to recover the network, while VSNPs in the second network could effectively transfer stress to the network chains grafted on their surfaces and maintain the gel network. As a result, the optimal NC‐DN hydrogels exhibit ultrastretchable (fracture strain 7822%), super tough (fracture toughness 18.22 MJ m^‐3, tensile strength 431 kPa), rapidly recoverable (≈92% toughness recovery after 5 min resting at room temperature), and self‐healable (can be stretched to 1331% after healing) properties. The newly designed Agar/PAM‐SiO₂ NC‐DN hydrogels with tunable network structure and mechanical properties by multi‐bond crosslinking provide a new avenue to better understand the fundamental structure‐property relationship of DN hydrogels and broaden the current hydrogel research and applications.     

盐度对N-异丙基丙烯酰胺与丙烯酰胺共聚物性能的影响

采用自由基共聚的方法,合成了温度敏感水凝胶。在不同环境温度测试了N-异丙基丙烯酰胺与丙烯酰胺共聚物的拉伸性能,并且在不同盐度下研究了共聚物的机械性能,试验中发现溶胀与未溶胀的水凝胶在力学性能上的差异。本文还研究了盐度对LCST(最低临界温度)的影响,试验结果表明,改变溶液盐度是一种有效控制水凝胶LCST的方法。     

Reinforced Cyanate Ester Resins with Carbon Nanotubes: Surface Modification,Reaction Activity and Mechanical Properties Analyses

The reinforcement and toughness of cyanate ester (CE) resins with multiwalls carbon nanotubes (MW-CNTs) were investigated in this paper. Based on the surface modification of MW-CNTs, the reaction activity of CE resins, desperation of MW-CNTs, mechanical properties and thermal properties of MW-CNTs/CE composites were addressed. TEM and XRD analyses demonstrate that the MW-CNTs with regular arrangement and perfect crystals structures can be achieved after the treatments with pyrolysis and dense HNO₃/H₂SO₄ acids oxidation. The reaction activity of CE systems with MW-CNTs is increased with the incorporation of carbon nanotubes. The mechanical analysis, dynamic mechanical analysis (DMA), and thermal gravimetric analysis (TGA) indicate that the addition of MW-CNTs can enhance both impact strength and flexural strength of cured CE resins without decreasing their thermal stability. The storage module for the MW-CNTs/CE composites is much higher than that of the pure CE sample in a wide temperature range. After aging in boiling distilled water, the water absorption of is less than that of CE resins.     

短切碳纤维混凝土的力学强度实验与分析

为探究短切碳纤维对混凝土力学强度的影响机制,以C40和C50矿渣水泥混凝土为研究对象,考察了短切碳纤维长度和掺量对混凝土的抗压强度、劈裂抗拉强度和抗折强度的影响规律,特别是与不掺纤维混凝土的强度对比.实验结果表明,碳纤维的加入可使混凝土的力学强度有不同程度的提高,其中以抗折强度的增长最为明显,劈拉强度次之,而抗压强度比的增幅相对最小,在高纤维掺量时抗压强度甚至低于不掺纤维混凝土;纤维长度的增大对混凝土的力学强度增长更为有利,在低强度等级(C40)混凝土中的表现更为明显.力学分析认为,随机分布的短切碳纤维可显著提高混凝土对劈裂或弯折式破坏的抵抗作用,但对受压时所发生的剪切式破坏却难以发挥明显效果.     

Thermoplastic Soy Protein Nanocomposites Reinforced by Carbon Nanotubes

MWNTs of various sizes were compounded into SPI matrix by solution mixing and then compression‐molded into nanocomposite sheets, which were characterized by XRD, SEM, TEM, and tensile and water uptake testing. The resultant nanocomposites showed improved mechanical performance and higher water resistance depending on MWNT size and content. This work details a strategy to achieve improved performance, especially in terms of mechanical properties, using MWNTs of various sizes to regulate the entanglement and penetration between SPI and MWNTs.

     

碳纳米管水泥基复合材料的力学性能和抗冻性能研究

作为新型纳米材料,碳纳米管(MWCNTs)已经应用于水泥基材料中用以改善水泥基材料性能.本文采用十六烷基三甲基溴化铵作为分散剂将碳纳米管均匀分散于水泥材料中制备成碳纳米管水泥基复合材料,并细致研究了其力学性能和抗冻性能.结果表明碳纳米管的加入能够有效的增加水泥基材料的力学性能和抗冻性能.当碳纳米管的掺量为0.1％时,碳纳米管水泥基复合材料的力学性能达到最大,其抗折强度和抗压强度分别为17.5MPa和92.3 MPa.在300次冻融循环过程中,碳纳米管水泥基复合材料的质量损失率和动弹模量变化率偏低,表明碳纳米管水泥基复合材料的抗冻性得到了增强.SEM微观分析表明,碳纳米管在水泥基材料中起到了桥联和拔出效应,能够有效的延缓和阻止水泥基材料受到外界的破坏.     

粗糙度对碳纤维布增强聚丙烯力学性能影响

为了研究粗糙度对碳纤维布增强聚丙烯力学性能的影响。通过打磨的方式制作出有着不同表面粗糙度的聚丙烯试件并在其试件上粘贴相同几何尺寸、相同数量的碳纤维布,同时在制作试件的过程中注重对涂刷胶层厚度的控制,制作出15个试件,进行了A,B,C三组拉伸实验。实验结果表明:粗糙度对碳纤维布增强聚丙烯拉伸性能的提高有着显著的影响,B,C组实验结果表明在相同的试验力下,粗糙度数值在0.141~2.751的范围内递增时,试件抗变形能力逐渐增强,试件的变形量逐渐减小。同时随着粗糙度数值的递增,实验中的试验力位移曲线在试验力0.5~0.6 kN的范围内线形斜率数值由0.61增长到5.61,且提升幅度也随着粗糙度的增加逐渐增大。     

Structure Stability,Flame Retardancy,and Antimicrobial Properties of Polyurethane Composite Nanofibers Containing Tannic Acid and Boron-Doped Carbon Nanotubes

A polyurethane (PU) composite nanofiber with superior flame retardancy and antimicrobial property is developed through the simultaneous incorporation of boron-doped carbon nanotubes (CNTs) and tannic acid (TA), resulting in excellent thermal, mechanical, and eco-friendly flame-retardant properties. The tensile strength and peak heat-release rate of the composite nanofiber increase with increasing filler content, with the optimal performance (7.38 ± 1.04 MPa and 254 W g⁻¹) being achieved at 3 wt% filler. Using a series of analytical techniques, it is demonstrated that the nanostructure of the neat PU completely collapses upon heating, transforming into a film-like structure; in contrast, a higher loading of nanofiller leads to a higher heat-shielding capability, thereby facilitating preservation of the composite nanofiber structure. Finally, the antibacterial activity is shown to increase as a result of the synergic effect of the boron-doped CNTs and TA.     

PP/碳纤维复合材料力学性能的研究

综合考虑碳纤维材料的加工适应性以及对基体力学性能改善的能力,分别选取了短切碳纤维和碳纤维粉末作为增强相,比较了它们对于PP的增强效果以及加工的难易,通过测定拉伸性能和冲击韧性考察了短切碳纤维的含量以及碳纤维粉末的含量对各自复合材料力学性能的影响。结果表明,随着碳纤维含量的增加,两种复合材料的冲击韧性以及拉伸性能都呈先增加后减小的趋势,短切碳纤维作为增强相对于基体树脂的力学性能增强效果更为显著,碳纤维粉末作为增强相的复合材料加工适应性强,性能更加稳定,该研究对碳纤维制品的实际注塑生产具有十分重要的意义。     

Dual Cross-Linked Polymethacrylic Acid Hydrogels with Tunable Mechanical Properties and Shape Memory Behavior

Herein, a series of poly(methacrylic acid) hydrogels are prepared via bulk polymerization of methacrylic acid (MAAc) and grafting of Triton X-100 (TX-100). One-pot and extremely simple chemistry consist of only mixing and subsequently heating of commercially available monomer and surfactant. The polymer chains are interconnected through dual physical cross-link points formed by the hydrophobic associations in the center of TX-100 micelles and hydrogen bonds stabilized by hydrophobic α-methyl groups of MAAc. The hydrogels exhibit tunable mechanical properties ranging between softness and stiffness by adjusting the surfactant/monomer molar ratio, such as Young modulus of 0.6−22 MPa, elongation at break of 750−1700%, tensile strength of 0.21−3.6 MPa, and compressive strength of 41−93 MPa. The synergistic effect of high-density hydrogen bonds with hydrophobic associations endows a plastic-like hydrogel with high strength and shape memory (SM) behavior, while a high concentration of micelles with low-density hydrogen bonds endows a stretchable elastic hydrogel. The combination of temperature-induced SM property and wide-ranging mechanical performance will make such hydrogels useful in diverse applications.     

碳纳米管固井水泥复合材料抗腐蚀及力学性能研究

为解决油田地层水在固井水泥中的渗透腐蚀造成套管损坏及环空带压问题,同时优化其力学性能,以纳米材料作为水泥基材料的增强组份,掺加碳纳米管(CNTs)制备了一种碳纳米管固井水泥复合材料.通过非共价键修饰法筛选多种碳纳米管分散剂,从其分散能力和悬浮液的稳定性确定了最优分散剂;研究了碳纳米管固井水泥复合材料的抗压、抗拉力学性能,通过测试强度及孔渗特征变化来对复合材料的抗腐蚀性进行了评价.结果 表明,当碳纳米管的掺量为0.03％时,碳纳米管固井水泥复合材料可将水泥石的抗压、抗拉强度分别提高50％、30％以上,其腐蚀60 d的强度衰退和孔隙度增大率均小于5％、渗透率增大率小于1％、有效抑制了有害孔(大于0.1 μm)的产生,具有较好的抗腐蚀渗透性能.该水泥复合材料优良的抗腐蚀性、高抗压、高抗拉特性(韧性),对多级缝网压裂水平井开发具有重要的应用价值.     

Nanoclay Reinforced Self‐Cross‐Linking Poly(N‐Hydroxyethyl Acrylamide) Hydrogels with Integrated High Performances

Despite recent significant progress in fabricating tough hydrogels, it is still a challenge to realize high strength, large stretchability, high toughness, rapid recoverability, and good self‐healing simultaneously in a single hydrogel. Herein, Laponite reinforced self‐cross‐linking poly(N‐hydroxyethyl acrylamide) (PHEAA) hydrogels (i.e., PHEAA/Laponite nanocomposite [NC] gels) with dual physically cross‐linked network structures, where PHEAA chains can be self‐cross‐linked by themselves and also cross‐linked by Laponite nanoplatelets, demonstrate integrated high performances. At optimal conditions, PHEAA/Laponite NC gels exhibit high tensile strength of 1.31 MPa, ultrahigh tensile strain of 52.23 mm mm^?1, high toughness of 2238 J m^?2, rapid self‐recoverability (toughness recovery of 79% and stiffness recovery of 74% at room temperature for 2 min recovery without any external stimuli), and good self‐healing properties (strain healing efficiency of 42%). The work provides a promising and simple strategy for the fabrication of dual physically cross‐linked NC gels with integrated high performances, and helps to expand the fundamentals and applications of NC gels.     

Mechanical Properties of Woodceramics: A Porous Carbon Material

The mechanical properties of woodceramics, which are new porous carbon materials utilizing the natural structure of wood, were investigated. The effects of burning temperature and amount of impregnated phenol resin on Young's modulus, compressive strength and fracture toughness were measured. The fracture morphology was then observed, and simplified mechanical models of the woodceramics were discussed to explain the mechanical properties. The fracture was initiated at the cell walls that were located in vertical direction against the applied stress. The effect of impregnated phenol resin on the Young's modulus and the compressive strength was reasonably explained by a wall-bending model.     

聚合物/CNTs复合材料制备及其力学性能影响因素

综述了近年CNTs增强聚合物复合材料的制备方法,重点分析了制备过程中影响复合材料力学性能的主要因素,总结了聚合物/CNTs复合材料制备过程中存在的技术难题并对其未来的发展应用进行了展望。