聚氨酯/KH560改性非离子型水性环氧固化剂的制备与性能

用异佛尔酮二异氰酸酯(IPDI)、聚乙二醇(PEG-6000)、环氧树脂E-51为原料合成聚氨酯型反应性乳化剂(PURE),将PURE与环氧树脂E-44混合后与γ-缩水甘油醚氧丙基三甲氧基硅烷(KH560)改性的单封端四乙烯五胺反应,制备了非离子型水性环氧固化剂。考察了PURE和KH560含量对固化物柔韧性及耐热性的影响。结果表明,当PURE质量分数为15%、KH560摩尔分数为6%时,固化剂稳定性良好,环氧树脂固化膜的综合性能最佳,冲击强度为19.35 k J/m2,拉伸强度为38.7 MPa,吸水率为2.85%,热失重5%和50%的温度分别为207℃和372℃。     

聚氨酯改性非离子型水性环氧固化剂的制备与性能

以异佛尔酮二异氰酸酯(IPDI)、环氧树脂(E-44)和聚乙二醇6 000(PEG 6 000)为原料,制备了聚氨酯(PU)型反应性大分子环氧乳化剂,将这种乳化剂与E-44混合均匀后再与正丁基缩水甘油醚单封端的四乙烯五胺(TEPA-660a)反应制备出非离子型水性环氧树脂固化剂。采用红外光谱(FT-IR)、扫描电镜(SEM)、热失重(TG)和粒径测试等方法表征和测试了聚合物的结构、性能及乳液粒径,并研究了乳化剂含量对固化膜断面形貌、力学性能和热性能的影响。结果表明,当乳化剂用量占乳化剂和E-44质量分数的15%时,所制备的非离子水性环2氧树脂固化剂稳定性良好,粒径为216.5 nm,环氧固化膜冲击强度为16.32 k J/m,拉伸强度为33.7 MPa,5%和50%的质量热损失温度分别为175℃和365℃,与未改性环氧固化膜相比,韧性得到明显提高。     

水性环氧树脂-聚丙烯酸酯-聚氨酯杂化乳液研究

以2,2-二羟甲基丙酸为亲水扩链剂,环氧树脂E-51为改性剂制得了以异氰酸酯基封端、含有羧基的聚氨酯预聚体。然后以季戊四醇三丙烯酸酯(PETA)对预聚体进行部分封端,将封端的预聚体与甲基丙烯酸甲酯(MMA)复合,并分散于水中,得到了含MMA的聚氨酯水分散体。最后,通过原位自由基聚合制得水性环氧树脂-聚丙烯酸酯-聚氨酯杂化乳液(WPUEA)。通过红外光谱、扫描电镜、透射电镜和热失重分析等对乳液及聚合物结构进行了表征并研究了E-51和MMA的用量对聚合物粒子性能的影响。结果表明,MMA和E-51用量分别为聚氨酯预聚体质量的25%~30%和7%~9%时,WPUEA乳液及聚合物的综合性能最佳。     

含氟硅聚氨酯预聚物改性环氧树脂的制备及性能研究

为提高环氧树脂的性能,采用含氟硅聚氨酯预聚体(FSPUP)为改性剂对环氧树脂进行了改性研究。对1,3,5-三甲基-1,3,5-三(3,3,3-三氟丙基)环三硅氧烷(D_3F)进行开环聚合,合成了羟基氟硅油;使用3-(2-氨乙基)-氨丙基三甲氧基硅烷(SCA-603)对其封端,制得氨基氟硅油;再使用异佛尔酮二异氰酸酯(IPDI)、聚醚二醇和氨基氟硅油进行反应,制得异氰酸基团封端的含氟硅聚氨酯预聚物。以制备的聚氨酯预聚物与环氧树脂(E-51)合成改性环氧树脂(FSPUP/EP),并用FT-IR表征,研究了FSPUF的加入量对改性环氧树脂体系力学性能的影响。通过动态热机械分析(DMA)研究了FSPUP/EP固化物的阻尼性能,用TG研究了FSPUP/EP的耐热性能。结果表明:随着FSPUP的加入,改性环氧树脂的力学性能、阻尼性能和耐热性能都获得了很大提高。     

非离子型水性环氧树脂固化剂的合成与性能研究

采用低相对分子质量的环氧树脂E-51与聚醚-4000反应制备环氧改性聚醚加成物,再与多乙烯多胺进行反应制备胺封端的聚醚-环氧-胺加成物,最后采用单环氧化合物进行封端,合成非离子型水性环氧固化剂,实验表明工艺可行。对环氧E-51改性聚醚-4000合成过程中的各影响因素进行了研究,并对非离子型水性环氧固化剂的固化性能进行了评价。最佳配方与工艺为:n(环氧树脂E-51)∶n(聚醚-4000)2∶1,催化剂选用含三氟化硼(BF3)质量分数2%的乙醚溶液(60℃时加入,加入量为2%)。与现有的市售水性环氧固化剂固化性能相比,非离子型水性环氧固化剂固化的环氧体系的柔韧性和耐冲击性有大幅提高。     

无溶剂无色透明快速固化环氧胶粘剂的研制

以季戊四醇和3-巯基丙酸为原料合成了多巯基化合物,选用HDI、H12MDI、IPDI 3种二异氰酸酯和E-51环氧树脂作扩链剂,得到4种无色透明的多巯基固化剂,再将其与环氧树脂混合制得胶粘剂。通过对试样的透光率、剪切强度、介电性能、表面能和吸水率测定研究了不同扩链剂制得的固化剂对胶粘剂性能的影响。结果表明,HDI扩链固化效果最优。     

含氟硅水性聚氨酯的合成及其疏水和阻燃性能

以聚酯二醇、甲苯二异氰酸酯、八氟戊醇、γ-氨丙基三乙氧基硅烷等为原料制得一系列氟、硅化合物封端的水性聚氨酯乳液。利用红外光谱仪、接触角测量仪、锥形量热仪等对水性聚氨酯进行结构表征和性能测试。结果表明,氟、硅被成功引入到聚氨酯分子链中,改性后乳液仍能表现出良好的离心稳定性;胶膜与水的接触角可达到106.1°,吸水率由20.8%降至1.7%,材料的疏水性能得到提高;最大热释放速率和总热释量分别由334.5 k W/m2和9.19 MJ/m2下降至245.6 k W/m2和6.66MJ/m2,聚氨酯胶膜的阻燃性能得到有效改善;同时,胶膜的热稳定性能和残炭率也得到提高。     

聚氨酯改性中温快速固化环氧粘合剂的制备与应用

以聚四氢呋喃醚、异佛尔酮二异氰酸酯、2-乙基咪唑为原料,合成了以2-乙基咪唑封端的聚氨酯,并用于改性环氧树脂E-44.利用傅立叶红外分析仪、示差扫描量热仪、拉伸试验机等手段对其与环氧树脂混合物的凝胶时间、固化温度、解封情况、拉伸剪切强度等性能进行了研究.结果表明,咪唑封端的聚氨酯可以在130℃下较好地解封,每10份E-...     

UV固化水性环氧衣康酸树脂氟改性研究

以环氧树脂(E-51)、衣康酸(IA)、甲基丙烯酸六氟丁酯(HFMA)为主要原料,合成了一系列有机氟改性UV固化水性环氧衣康酸树脂。研究了反应温度对合成树脂的影响,考察了HFMA用量对涂膜耐水性、水接触角和力学性能的影响,并利用红外光谱和热重分析对改性树脂进行了表征。结果表明:当反应温度为105℃,含氟单体与环氧树脂质量比为1∶4时,制得的树脂及其涂膜的综合性能优良,涂膜的吸水率由改性前的9.14%下降到改性后的4.01%,水接触角由改性前的63.26°增加到改性后的90.05°,耐水性、疏水性和热稳定性明显提高。     

新型硅烷改性聚醚弹性胶粘剂的研制

在硅烷改性聚醚(MS)聚合物中添加不同比例(10%、25%、40%、50%、60%、75%和100%)的环氧树脂(E-51)及固化剂,制备出一系列E-51改性MS双组分弹性胶粘剂,并利用万能材料试验机对固化产物进行性能测试。结果表明,当E-51添加量为50g(100 g硅烷改性聚醚中的加入量)时,E-51/MS弹性胶粘剂固化后的力学强度达到相对最大值,硬度为50A、拉伸强度为5.5 MPa、断裂伸长率为410%、剪切强度为6.0 MPa和剥离强度为7.4 N/mm。且选用分子质量更大的E-44(环氧树脂)制得的E-44/MS胶粘剂的力学性能和粘接性能更优异。     

Full characterization for material constants of a promising KNN-based lead-free piezoelectric ceramic

Potassium-sodium niobate (K_1-xNa_xNbO₃, referred to as KNN) solid solutions, which are an important type of lead-free piezoelectric materials possessing environmentally friendly features, good piezoelectric response and high Curie temperature, have attracted considerable attention in replacing lead-based ceramics. In order to promote the application of KNN-based ceramics in piezoelectric devices, we characterized a complete set of material constants of a high performance KNN-based ceramic, that is 0.965(K_0.48Na_0.52) (Nb_0.96Sb_0.04)O₃-0.035Bi_0.5Na_0.5Zr_0.15Hf_0.75O₃ (KNNS-BNZH), whose Curie temperature is 235 °C, piezoelectric coefficient d₃₃ is 380 pC/N and electromechanical coupling factor k₃₃ is 70%. These results will benefit the design of piezoelectric transducers and actuators using lead-free piezoelectric ceramics.     

Mechanical,dielectric, and thermal properties of fluorosilicone rubber composites filled with silica/multiwall carbon nanotube hybrid fillers

In this work, hybrid fillers consist of modified silica (SiO₂) and multiwalled carbon nanotube (MWCNT) were used to improve the mechanical, dielectric, and thermal properties of fluorosilicone (FSR) composites via a direct mechanical mixing method. With the increase of CNT loading in SiO₂/CNT hybrid loading ratio, the tensile properties, dielectric constant, electrical conductivity, and thermal properties all increase without a sharp sacrifice of flexibility. The dielectric constant of FSR-S15/C5 achieved 7,370 @1 kHz, which is about four orders of the FSR-S20, and the dielectric loss remains as low as 0.676 @1 kHz. Therefore, the linkage of SiO₂ and FSR chains not only enhances the interfacial interaction between the fillers and FSR matrix but also decreases the agglomeration of the fillers in matrix. What is more, modified SiO₂ and CNT were designed as the effective hybrid filler to improve the performance of the polymeric matrix through synergic effect.     

Investigation of dielectric and piezoelectric properties in aliovalent Eu3+-modified Pb(Mg1/3Nb2/3)O3-PbTiO3 ceramics

Rare earth (Eu³⁺)-modified Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PMN-PT) polycrystalline ferroelectric ceramics were fabricated by high-temperature solid-state sintering, the phase structure, dielectric and piezoelectric properties were investigated. Eu³⁺ addition was found to significantly improve dielectric and piezoelectric properties of PMN-PT, where the optimized properties were achieved for the composition of 2.5 mol%Eu: 0.72PMN-0.28PT, with the piezoelectric d₃₃ = 1420 pC/N, dielectric ε_r = 12 200 and electromechanical k₃₃ = 0.78, respectively. All these results indicate that the Eu³⁺-doped PMN-PT ceramics are promising candidates for high-performance room-temperature piezoelectric devices.     

High magnetic and ferroelectric properties of BZT-LSM multiferroic composites at room temperature

In this research, the effects of La_0.7Sr_0.3MnO₃ additive on the phase evolution, microstructure, dielectric, ferroelectric and magnetic properties of BaZr_0.07Ti_0.93O₃ ceramics were systematically investigated. The (BaZr_0.07Ti_0.93O₃)/x(La_0.7Sr_0.3MnO₃) or BZT/xLSM (where x?=?0, 5, 10 and 20?mol%) ceramics were prepared via a solid state reaction method. A pure perovskite phase is observed for the samples of x?≤?10?mol%. The M-H hysteresis loops also show an improvement in the magnetic behavior for higher LSM content samples as well as the modified ferroelectric properties. However, the 5?mol% sample exhibited the optimum ferroelectric and ferromagnetic properties with remnant magnetization (M_r) and remanent polarization (P_r) of 2.38?emu/g and 10.5?µC/cm², respectively. The dielectric-temperature curves show that the two phase-transition temperatures as observed for the unmodified BZT ceramic merges into a single phase-transition temperature for the 5?mol% sample and then become flat curves for the 10?mol% sample. In addition, the mechanical properties i.e. Knoop hardness and Young's modulus values increase with increasing LSM content, where Knoop hardness and Young's modulus values for the 20?mol% sample are increased by ~ 45% and ~ 104%, respectively, as compared to the unmodified sample.     

PVDF piezoelectric voltage coefficient in situ measurements as a function of applied stress

Direct piezoelectric g₃₁ voltage coefficient was measured in situ as a function of applied tensile stress for films of polyvinylidene fluoride (PVDF). Measurements were performed under quasi‐static conditions with applied strain rates of 0.5–1.5 mm/min for strains up to 12%. Open‐circuit voltage was measured with a contact‐less electrostatic voltmeter. Obtained results show a strong dependence of the g₃₁ coefficient of mono‐oriented PVDF films on the applied stress, with a maximum value of the coefficient in the transition region between elastic and plastic deformation zones. The effect of sample geometry on the apparent g₃₁ coefficient is shown and discussed. The anisotropy of the piezoelectric effect is studied by means of g₃₁ and g₃₂ measurements. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43248.     

A methacrylate monomer bearing nitro,aryl, and hydroxyl side groups: Homopolymerization,characterization, dielectric,and thermal degradation behaviors

2‐Hydroxy‐3‐(4‐nitrophenoxy)propyl methacrylate (HNPPMA) monomer was synthesized. The poly(HNPPMA) was prepared by free radical polymerization (FRP) method. The characterization of poly(HNPPMA) was carried out using FT‐IR, NMR, differential scanning calorimetry, and GPC techniques. The thermal stability and degradation behavior of this polymer have been studied by using thermogravimetry (TG), GC‐MS, NMR, and FT‐IR. The results were in comparison to poly[2‐hydroxy‐3‐(1‐naphtyloxy)propyl methacrylate] sample with α‐naphtyloxy side group prepared by the same method in the our previous study. The effect of thermal activation on non‐isothermal decomposition kinetics of poly(HNPPMA) was investigated using thermogravimetric analysis according to Flynn‐Wall‐Ozawa method. The dielectric measurements of poly(HNPPMA) and doped with europium(III)chloride (EuCI₃) were investigated by impedance analyzer technique in range of 10–4000 Hz frequency by depending on the alternating current conductivities. The mode of thermal degradation including formation of the main products of poly(HNPPMA) degraded from ambient temperature to 500 °C was identified. S°, the cold ring fraction (CRF) was collected from room temperature to 500 °C. The structure of the degradation products has also been studied depending on the GC‐MS analysis. The thermal degradation mechanism for poly(HNPPMA) with radical degradation processes thought to dominate at high temperature was proposed based on GC/MS, NMR, FT‐IR, and taking into account the new products and differences in stability. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43925.     

Metallopolymers based on a polyazomethine ligand containing rigid oxadiazole and flexible tetramethyldisiloxane units

Soluble, easily processable polymer–metal complexes with improved optical and dielectric properties for optoelectronic functional materials were obtained. For this, a new polyazomethine (PAZ2) was prepared by the reaction of a siloxane dialdehyde and bis(formyl‐p‐phenoxymethyl) tetramethyldisiloxane with 2,5‐bis(p‐aminophenyl)‐1,3,4‐oxadiazole, and it was used as a ligand for Cu(II), Co(II), and Zn(II) ions on the basis of the presence of the electron‐donor nitrogen atoms from the azomethine group and oxadiazole ring. The structure of the PAZ2 was determined by spectral [Fourier transform infrared (FTIR) and ¹H‐NMR spectroscopy] techniques. The metal complexation was proven by FTIR spectroscopy, and the silicon‐to‐metal ratios in the complexes were established by energy‐dispersive X‐ray fluorescence. The new materials were characterized by gel permeation chromatography, thermogravimetric analysis, and differential scanning calorimetry. The optical properties of PAZ2 and the derived metal complexes were studied by ultraviolet–visible and fluorescence spectroscopies. PAZ2 shows fluorescence emission, and it was significantly enhanced by metal complexation. The emission was enhanced by protonation; this behavior is useful, especially for sensors. The electrical properties were investigated by dielectric spectroscopy at various frequencies and temperatures, and this emphasized the existence of dipolar relaxations. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41631.     

Photoluminescence and unique magnetoluminescence of transparent (Tb1-xYx)3Al5O12 ceramics

Luminescent transparent ceramics (Tb_1-xY_x)₃Al₅O₁₂ (x = 0, 0.2, 0.5, 0.8) are successfully prepared by a solid-state method with additional hot isostatic pressing (HIP) treatment, and the structure and properties are investigated by XRD, SEM, PL, UV–Vis spectrophotometry and ellipsometry. The Y-containing samples are shown to be solid solution phases between TAG and YAG. The PL intensity is 14 times stronger with the incorporation of 80 mol.% Y, and the ⁵D₄→⁷F₅ emission lifetime of Tb³⁺ is prolonged from 0.357 to 3.035 ms at room temperature. A unique magnetoluminescence emerges upon the incorporation of Y, showing an interesting emission decrease to 55% as the Y content reaches 80 mol.%. Remarkably, this magnetoluminesence can occur at room temperature without an intense magnetic field. Based on our work, transparent (Tb_1-xY_x)₃Al₅O₁₂ ceramics exhibit the potential for applications in green emitters, optical instruments and photoelectric devices. In particular, the magnetoluminescence provides a simple, noncontact and nondestructive route for probing magnetic fields.     

The effect of the Zn/Sn ratio on the formation of single phase kesterite Cu2ZnSnS4 solar cell material

The effect of the Zn/Sn ratio in the solution on the properties of Cu₂ZnSnS₄ films prepared by sol-gel method has been investigated. As the Zn/Sn ratio in the solution increases to a certain value, a pure single phase kesterite CZTS is obtained and confirmed by XRD, XPS and Raman. Through controlling the Zn/Sn ratio in the solution, secondary phases such as SnO₂ can be avoided and an optimal condition for single phase kesterite CZTS can be achieved. Surface SEM images of the CZTS films are investigated and the optical band gap of the optimized CZTS film is found to be 1.23 eV.     

Poly[6‐(2,6‐bis(1′‐methylbenzimidazolyl)pyridin‐4‐yloxy)hexyl acrylate] (PBIP) and its terbium (III) complex (PBIP‐Tb3+): Homopolymerization,optical, and magnetic performance

Poly[6‐(2,6‐bis(1′‐methylbenzimidazolyl)pyridin‐4‐yloxy)hexyl acrylate] (PBIP) and its terbium complex (PBIP‐Tb³⁺) were prepared and characterized by ¹H NMR and FT‐IR. The optical properties of PBIP‐Tb³⁺ complex were characterized by UV–vis spectroscopy and fluorescence spectroscopy. Both polymer PBIP and PBIP‐Tb³⁺ complex show good thermal stability. The magnetic property of PBIP‐Tb³⁺ complex was measured as a function of temperature (5–300 K) at 30 kOe and as a function of an external field (?50 to 50 kOe) at 5 K. Magnetic hysteresis loop of PBIP‐Tb³⁺ complex at 5 K shows typical “S” shape and PBIP‐Tb³⁺ complex is soft ferromagnetic. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44249.