氨基改性碳纳米管的制备及对聚氨酯泡沫材料的影响

在碳纳米管表面引入大量氨基后,将其加入水为发泡剂的聚氨酯发泡体系,研究了碳纳米管对聚氨酯泡沫泡孔结构和力学性能的影响。实验结果表明,氨基表面改性碳纳米管的引入有助于提高聚氨酯泡沫孔壁结构的完整性,并且泡孔分布更加均匀。随着体系中碳纳米管含量的增加,泡沫孔径尺寸先减小后增大,当填充量为0.75%时,泡沫材料具有最小平均孔径(0.23mm)。扫描电子显微镜观察发现该条件下泡孔分布均匀,结构最为完整。同时,材料的力学性能也表现出相同的规律,当碳纳米管含量为0.75%时,材料具有最大压缩强度和压缩模量,分别为0.14 MPa和2.09 MPa,与纯聚氨酯的泡沫材料相比分别提高了100%和161%。     

泡沫混凝土的负泊松比设计与静载力学特性研究

拉胀材料因其特殊性能在材料领域备受重视.将负泊松比效应应用在泡沫混凝土中,可使其具备良好的力学性能与吸能效果.本试验利用化学发泡法制备了三种不同孔隙形态的泡沫混凝土,分别为闭孔泡沫混凝土、连通孔泡沫混凝土、内凹孔泡沫混凝土.利用图像法对泡沫混凝土的干密度和孔隙结构参数进行表征,通过万能试验机测试了泡沫混凝土的静态压缩强度、抗折强度,通过工业相机及数字散斑相关方法(DSCM)研究了泡沫混凝土的区域形变行为以及泊松比值.结果表明:泡沫混凝土的孔隙率、孔径及干密度与发泡剂的添加量有关,添加量越多,干密度越小,孔隙率和孔径增大;泡沫混凝土的抗压、抗折强度也与发泡剂的添加量有关,其强度随着添加量的增多而减小,但孔隙呈内凹状的泡沫混凝土具有较高的抗压强度和抗折强度,内凹孔泡沫混凝土的压缩断裂能为33.9×103 J/m3,相比闭孔泡沫混凝土提高44.9％.DSCM表明内凹孔泡沫混凝土在压缩过程中会出现明显的收缩效应,其收缩率为闭孔泡沫混凝土的37.5％,压缩期间负泊松比值最大可达-3.7.     

发泡剂含量对双马来酰亚胺泡沫泡孔结构和性能的影响

以偶氮二甲酰胺(AC)为发泡剂,采用预聚、发泡的两步法制备双马来酰亚胺泡沫,研究AC含量对泡沫泡孔结构、密度、尺寸稳定性温度和压缩性能的影响。结果表明:可通过发泡剂用量的改变实现泡沫密度在60~280kg/m3范围内调整,发泡剂用量对泡孔尺寸及其均匀性影响较小。随发泡剂用量降低,尺寸稳定性温度和压缩性能提高,当泡沫密度为280kg/m3时,尺寸稳定性温度可达220℃,压缩强度和模量分别为4.8MPa和200MPa,满足结构泡沫的耐温性能和力学性能要求。     

双氧水对镁系无机泡沫材料性能和孔结构的影响

以镁系胶凝材料为基体,双氧水为发泡剂,采用化学发泡工艺制备了内部含有大量密闭气孔的镁系无机泡沫材料。研究了双氧水添加量对泡沫材料发泡倍率、体积密度、压缩强度、弯曲强度、孔结构参数以及导热系数的影响。研究结果表明:双氧水添加量增加,导致胶凝体中的气泡核增加以及气泡生长的内动力增大,气孔孔径变大,体积密度和力学强度减小;随着双氧水添加量增加,材料的导热系数不断减小,在双氧水添加量大于16‰时增大。镁系无机泡沫材料的压缩强度和弯曲强度与体积密度的回归方程分别为y=-6.06+24.19x,y=-0.64+3.82x,均为密切线性相关关系。且在双氧水添加量为8‰时泡沫材料取得最大力学强度,此时气孔孔径最小,孔结构参数较优,导热系数为0.071 W/(m·K),体积密度仅为0.54g/cm3。     

发泡剂粒径对硅橡胶泡沫材料性能的影响研究

以硅橡胶为基体材料,采用发泡剂H制备硅泡沫材料.研究了不同发泡助剂对发泡剂H分解温度的影响,以及发泡剂粒径对硅泡沫材料密度、硬度、力学性能、压缩性能和泡孔大小及其分布状态的影响规律.结果表明:发泡剂H与发泡助剂尿素的比例为1:1时,两者之间具有良好的匹配性;在发泡剂粒径对硅泡沫材料性能的影响方面,随着发泡剂粒径的减小,硅泡沫材料的密度、硬度、拉伸强度和40％压缩应变下的压缩应力值逐渐变大,当发泡剂粒径达到300目时,上述性能参数达到最大值,之后又出现下降趋势;其中,原始目数和较大目数下制备的硅泡沫材料的性能变化情况相似.同时,采用SEM技术对不同发泡剂粒径时硅泡沫材料的泡孔大小和分布状态进行了分析.     

酚醛泡沫力学性能及其密度-力学性能模型研究

以多聚甲醛代替甲醛溶液制备高固含可发性酚醛树脂,在70℃发泡制备酚醛泡沫材料,研究了表面活性剂、固化剂和发泡剂对泡沫的密度、力学性能的影响。研究结果表明,在表面活性剂添加量为12%,固化剂添加量为30%,发泡剂添加量为5%时,制备的泡沫性能较优。通过Gibson-Ashby提出的泡沫塑料的力学性能与密度的关系模型,创建酚醛泡沫密度-力学性能模型,结果表明泡沫力学性能与密度呈现良好的指数关系,且间接拟合和直接拟合2种方法得出的模型指数基本相符。     

聚氨酯/环氧树脂互穿网络半硬泡沫的力学性能及吸能特性

采用同步法制备了聚氨酯/环氧树脂互穿聚合物网络(IPN)半硬泡沫。通过压缩和拉伸试验研究了泡沫材料密度对力学性能的影响。研究表明,在所研究的密度范围内,泡沫的压缩模量和屈服强度均与密度成指数关系。泡沫的拉伸模量和断裂强度与密度也存在类似的关系。利用这些方程可以很好地预测泡沫力学性能随密度的变化关系。IPN泡沫兼有较好的韧性和较高的拉伸强度。相同形变下,相同密度IPN半硬泡沫拉伸过程的单位体积吸能大于压缩过程的单位体积吸能。     

迷宫形开孔硬质聚氨酯泡沫制备和性能研究

以多亚甲基多苯基异氰酸酯(PM-200)、聚醚多元醇(5110)为主要原料,以硅油(L580)为稳泡剂,水(H2O)为发泡剂,采用一步发泡法制备一系列不同密度硬质聚氨酯泡沫材料,通过水压穿孔工艺实现硬质聚氨酯泡沫开孔,制备具有形如迷宫样的相互贯通的开孔硬质聚氨酯泡沫。研究了泡沫密度和开孔压力对泡沫开孔率和压缩强度的影响,以及开孔率对吸声系数的影响。结果表明:开孔压力越大,相应的开孔率越大;在开孔压力相同的情况下,泡沫的密度越小,开孔率越大;开孔率越大,材料吸声系数越大;开孔压力的变化对泡沫压缩强度影响不大。     

高岭土/聚磷酸铵阻燃硬质聚氨酯-酰亚胺泡沫塑料的制备与性能

采用聚酰亚胺(PI)预聚法,以高岭土(Kaolin,KL)和聚磷酸铵(APP)为阻燃剂,合成KL/APP阻燃硬质聚氨酯-酰亚胺(PUI)泡沫塑料。分析KL/APP的添加量和配比对氧指数、烟密度、炭层形貌、表观密度及力学性能的影响。结果表明:随着KL/APP复配阻燃剂添加量的增加,硬质PUI泡沫塑料的氧指数、表观密度、压缩强度、压缩模量以及表面粉化程度均增加,且密度指数分别为1.999和1.764;烟密度随着KL含量的增大而减小,KL/APP阻燃剂能改善泡沫炭层疏松多孔的缺点。     

苯酚胺类催化剂HP-30对PU硬泡结构与性能的影响

选用聚醚多元醇GR-835G、多亚甲基多苯基多异氰酸酯PM-200作为主要原料,苯酚胺类催化剂HP-30作为三聚催化剂,H2O作为发泡剂,成功制备出具有高压缩性能的且表观密度为60kg/m3的PU硬泡。结果表明,HP-30不仅能起到催化作用,还能些许程度地起到发泡剂的作用。随着HP-30用量的增加,发泡体系的乳白时间、上升时间及凝胶时间均不断缩短,泡沫体的表观密度则呈先增大后减小再增大的趋势;若此时需得到相同表观密度的泡沫体,可适当改变发泡剂H2O的用量,且6%(质量分数)以内H2O量的变化对发泡时间及体系粘度几乎无影响。HP-30用量的增加,有助于改善60g/m3泡沫体的压缩性能,且当HP-30的用量为13pphp时,泡沫体的压缩强度与压缩模量分别能达0.772和30.0MPa。此外,还探讨了HP-30的作用机理。     

Enhancement in insulation and mechanical properties of PMMA nanocomposite foams infused with multi-walled carbon nanotubes

In this study, PMMA/CNTs composite materials with carboxyl-multi walled carbon nanotubes (c-MWNTs) or untreated MWNTs were prepared via in-situ bulk polymerization. The as-prepared PMMA/CNTs composite materials were then characterized by Fourier-Transformation infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM). The molecular weights of PMMA extracted from PMMA/CNTs composite materials and bulk PMMA were determined by gel permeation chromatography (GPC) with THF used as the eluant. The PMMA/CNTs composite materials were used to produce foams by a batch process in an autoclave using nitrogen as foaming agent. The cellular microstructure, insulation and compressive mechanical properties of PMMA/CNTs composite foams were also investigated in detail. Compared to neat PMMA foam, the presence of CNTs increases in cell density and reduces cell size. The insulation and compressive mechanical properties of PMMA/CNTs composite foams were found to improve substantially those of neat PMMA foam. In particular, 22.6% decrease in thermal conductivity, 19.7% decrease in dielectric constant and 160% increase in compressive modulus were observed with the addition of 0.3 wt% carboxyl-multi walled carbon nanotubes (c-MWNTs).     

具有负温度系数效应的导电硬质聚氨酯泡沫

采用高能球磨分散方法制备了稳定的聚合物多元醇/碳纳米管分散液,并通过原位聚合制备了导电聚氨酯（PU）/碳纳米管（CNTs）硬质泡沫复合材料。采用扫描电镜（SEM）表征了泡沫复合材料的结构,研究了CNTs含量对泡沫材料导电性的影响以及泡沫材料的负温度系数（NTC）效应,通过压缩测试考察了泡沫材料的力学性能。结果表明,CN...     

Enhanced acoustic damping in flexible polyurethane foams filled with carbon nanotubes

Flexible polyurethane (PU) foams, with loading fractions of up to 0.2 wt% carbon nanotubes (CNTs), were made by free-rising foaming using water as blowing agent. Electron microscopy revealed an open cellular structure and a homogeneous dispersion of CNTs, although the incorporation of nanofiller affected the foaming process and thus the final foam density and cellular structure. The compressive response of the foams did not show an unambiguous improvement with CNT content due to the variable foam structure. However, dense films generated by hot pressing the foams indicated a significant intrinsic reinforcement of the polymer, even at low loadings of CNTs. Most significantly, CNTs were found to increase the acoustic activity monotonically at concentrations up to 0.1 wt%.     

Quantitative image analysis of polyurethane/carbon nanotube composite micostructures

Polyurethane/carbon nanotube (PUR/CNTs) composites are much more functional than pure polyurethanes. High intensity ultrasonic agitation was applied while preparing a mixture of multiwall carbon nanotubes and a monomer. The monomer/MWNT complexes were used to prepare PUR/CNTs nanocomposites. This paper describes the application of quantitative image analysis to characterise the microstructure of the monomer and segmented polyurethane with carbon nanotubes (CNTs). Stereological parameters chosen for analysis were used to evaluate the CNTs' dispersion in the monomer complex and the degree of matrix phase separation in the nanocomposites examined. The nanoparticles induced changes in the structure of the hard and soft domains in the polyurethane matrix and influenced thermal and mechanical properties of the material. Due to the introduction of the nanotubes in the polyurethane matrix, the physical size and glass transition temperature of hard domains increased while the tensile strength and storage modulus decreased.     

Si元素对碳纳米管增强铝基复合泡沫组织与性能的影响

针对金属基复合材料,添加合金元素是提升其综合性能的有效途径.本文通过高能球磨和填加造孔剂法,制备了添加Si元素的碳纳米管(CNTs)增强铝基(CNTs/Al-Si)复合泡沫,通过准静态压缩实验测试其压缩性能和吸能性能,进一步研究烧结温度和不同Si元素含量对CNTs/Al-Si复合泡沫微观组织、压缩性能和吸能性能的影响,...     

Piezoresistive and compression resistance relaxation behavior of water blown carbon nanotube/polyurethane composite foam

The in-situ bulk polycondensation process in combination with a ball milling dispersion process was used to prepare the water blown multiwall carbon nanotubes (CNT)/polyurethane (PU) composite foam. The mechanical properties, piezoresistive properties, strain sensitivity, stress and resistance relaxation behaviors of the composite foams were investigated. The results show that the CNT/PU composite foam has a better compression strength than the unfilled polyurethane foams and a negative pressure coefficient behavior under uniaxial compression. The resistance response of CNT/PU nanocomposites foam under cyclic compressive loading was quite stable. The nanocomposite foam containing a weight fraction of carbon nanotubes close to the percolation threshold presents the largest strain sensitivity for the resistance. The characteristic of resistance relaxation of CNT/PU composite foam is different from the stress relaxation due to the different relaxation mechanism. During compressive stress relaxation, the CNT/PU foam composites have excellent resistance recoverability while poor stress recoverability.     

Properties of carbon nano-tubes–Cf/SiC composite by precursor infiltration and pyrolysis process

Carbon nanotubes (CNTs) were introduced into the precursor infiltration and pyrolysis (PIP) carbon fiber reinforced silicon carbide matrix (C_f/SiC) composite via the infiltration slurry. The weight fraction of CNTs in the composite was 0.765‰. The fiber–matrix interface coating was prepared through chemical vapor deposition (CVD) process using methyltrichlorosilane (MTS). Effects of the CNTs on mechanical and thermal properties of the composite were evaluated by three-point bending test, single-edge notched beam (SENB) test, and laser flash method. Attributed to the introduction of the small quantity of CNTs, flexural strength and fracture toughness of the C_f/SiC composite both increased by 25%, and thermal conductivity at room temperature increased by 30%.     

AlN-CNTs/聚酰亚胺复合材料的制备与性能

为了研究氮化铝(AlN)和碳纳米管(CNTs)对聚酰亚胺(PI)的导热、热学、力学性能的协同效应,采用湿法球磨和热压成型法制备了AlN/PI和CNTs-AlN/PI复合材料。利用X射线衍射仪、扫描电子显微镜对复合材料进行了物相分析和断面形貌表征,分别考察了AlN及其与CNTs协同对PI复合材料的导热、热学、力学性能的影响。结果表明,AlN和CNTs在PI基体中分散均匀且接触界面良好,AlN的加入可以显著地提高复合材料的导热性能,且对复合材料的热稳定性和力学性能有一定的提高;固定AlN的含量为10%,加入少量的CNTs可以提高复合材料的导热性能,但对复合材料的力学性能有一定的负面影响。     

碳纳米管类型对CNTs/Lyocell复合纤维结构与性能的影响

分别采用单壁碳纳米管（SWNTs）和多壁碳纳米管（MWNTs）这两种碳纳米管（CNTs）制备不同的CNTs/Lyocell复合纤维,探讨了碳纳米管类型对复合纤维的结构与性能的影响。结果表明,碳纳米管类型并未影响CNTs/Lyocell纤维的结晶结构,质量分数为1%的SWNTs或MWNTs在Lyocell基体中分布都比较...     

Preparation and Application of Flexible Ethylene Vinyl Acetate Adhesive Composites by Ultrasonic-Assisted Forced Infiltration

Herein, carbon nanotubes (CNTs)–cellulose nanocrystals (CNCs)/ethylene-vinyl acetate (EVA) composite are prepared with excellent bonding properties, electrical conductivity, and thermal conductivity using an ultrasonic-assisted forced infiltration (UAFI) method. The CNTs–CNCs (10:1)/EVA composite had the highest shear (82.9 N) and strip (12.2 N) forces at the interface when bonding leather to fabric as an interface bonding material (IBM). Different mass ratios of CNTs to CNCs in the composites lead to different electrical and thermal conductivity properties. When the mass ratio of CNTs to CNCs is 10:1, the CNTs–CNCs(10:1)/EVA composites reach an electrical and thermal conductivity of 158.37 S m⁻¹ and 6.351 W (m·K)⁻¹, respectively. In addition, the CNTs–CNCs(10:1)/EVA composite shows excellent thermal stability, mechanical properties, thermal performance, and electromagnetic shielding. The prepared EVA composite has a broad application prospect in IBM.