壳聚糖接枝共聚制备高吸水性树脂的研究

以壳聚糖(CTS),丙烯酸(AA),丙烯酰胺(AM)为原料,N,N-亚甲基双烯酰胺(MBAM)为交联剂,NaH-SO3/K2S2O8氧化还原体系为引发剂,通过接枝共聚合反应制备高吸水性树脂。较佳制备条件为:m(CTS)∶m(AA)∶m(AM)为1∶3∶1,丙烯酸的中和度为70%,引发剂用量4%,交联剂用量0.04%,反应温度45℃。研究表明,此条件下所得树脂吸水率为402g/g,吸盐水(浓度0.9%)率为102g/g,并最后采用红外光谱、扫描电镜表征分析了树脂的结构。     

Modification of properties of rayon fibre by graft copolymerization with acrylic monomers

The change in rayon fibre properties due the grafting polymerization of methyl metacrylate (MMA) and butyl acrylate (BA) was investigated. The formation of rayon-g-PMMA or PBA was confirmed by FTIR spectroscopy, X-ray analysis, and TGA. The adhesion to PMMA and epoxy resin matrixes was determined using the microdrop technique. The PBA or PMMA grafting on the fibre led to lower mechanical properties than the ungrafted rayon fibre. However, the grafted rayon had better thermal properties than the ungrafted rayon and a shift of the decomposition temperature of the rayon was observed. The PMMA grafted to rayon improved the interfacial adhesion when PMMA was used as matrix (microdrop technique). The grafted polymer (PBA or PMMA) restricted the “wetting” of the fibre when epoxy resin was used as matrix and lowering the adhesion in comparison with ungrafted rayon fibre.     

丙烯酸酯接枝改性聚氨酯乳液的结构与性能

采用原位接枝聚合方法制备丙烯酸酯接枝改性聚氨酯乳液 ,通过电镜、差示扫描量热 (DSC)、热重分析 (TG)、耐水、耐溶剂性测定等研究了接枝改性聚氨酯乳液的结构与性能 ,证实丙烯酸酯在聚氨酯分子链上接枝。接枝共聚物的热稳定性、耐水耐溶剂性优于商品聚氨酯     

乳化剂对明胶接枝共聚反应的影响

本文研究了乳化剂(E)(1283,SDS和1283 SDS)对明胶/丙烯酸丁酯(Gel/BA)、明胶/丙烯腈(Gel/AN)和明胶/(丙烯酸丁酯—丙烯腈)〔Gel/(BA-AN)〕接枝共聚反应的影响,揭示出了这三种乳化剂的使用对明胶接枝共聚反应的影响规律。对于Gel/BA三种乳化剂均合适;对于Gel/AN、Gel/(BA-AN),1283或不加乳化剂较为合适。本文还研究了在不用乳化剂的条件下,乳化时间(Et)对Gel/(BA-AN)三元接枝共聚反应的影响。     

聚乙烯醇-丙烯酰胺接枝共聚物的制备及其性能研究

研究了以硝酸铈铵作引发剂、N,N'-亚甲基双丙烯酰胺作交联剂制备聚乙烯醇-丙烯酰胺接枝共聚型吸水树脂的方法,运用正交设计法,找出了影响产品吸水量和吸湿量诸因素的排列次序和各自的最佳条件,红外光谱测试分析表明反应生成了接枝共聚物,所得产品吸蒸馏水能力为1200倍左右,95%RH下的吸湿量为1.6倍左右.     

Fracture toughness analysis of O-POSS/PLA composites assessed by essential work of fracture method

Essential work of fracture (EWF) method was employed to investigate the effect of the octavinylisobutyl based polyhedral oligomeric silsesquioxane (O-POSS) addition in poly(lactic acid) (PLA) matrix on the fracture behavior of O-POSS/PLA composites. The 2 mm thick rectangular shaped PLA-matrix composites containing various weight ratios of O-POSS were injection molded after processing in a twin-screw extruder. Constant deformation rate tensile tests at room temperature were performed on double edge notched tensile (DENT) specimens with various ligament lengths. It was found that the addition of O-POSS to PLA improved the toughness. It was observed that a greater energy consumed after the maximum load reached on load–displacement curves for the composites. Optimum additive value was obtained at 7 wt% O-POSS.     

Synthesis of zirconia nanoparticles on carbon nanotubes and their potential for enhancing the fracture toughness of alumina ceramics

Nanoparticles of zirconia (ZrO₂) were in situ synthesized on the surface of carbon nanotubes by means of liquid phase reactions and a proper heat treatment process. The size of the nanoparticles could be controlled by the amount of zirconium source materials in a solution and its reaction times. In this study, the size of the nanoparticles ranged from several nanometers to twenty nanometers. It was particularly noted that the synthesized zirconia possessed a cubic structure (c-phase) which generally existed as a stable form of zirconia crystals at high temperatures (above 2370 °C) as well as a form of zirconia that could be used for enhancing the fracture toughness of alumina ceramics. Experimental results showed that the mechanical properties of alumina ceramics mixed with in situ synthesized nanoparticles on the surface of carbon nanotubes were much better than that of pristine nanotubes or zirconia nanoparticles alone. The existence of the nanoparticles on the surface of nanotubes results in improving the dispersion and bonding properties of the nanotubes in alumina matrix environment. The fracture toughness of CNT/ZrO₂ alumina ceramics was also improved by the mechanism of bridging effect.     

丙烯酸甲酯/二乙烯基苯接枝交联共聚合改性聚丙烯隔膜

研究了在聚丙烯(PP)隔膜表面接枝二乙烯基苯(DVB)/丙烯酸甲酯(MA)交联聚合物网络,提高隔膜高温条件下尺寸稳定性的改性方法。全反射傅立叶红外光谱(ATR-FT-IR)证明DVB和MA在PP隔膜表面发生了聚合反应。考察了接枝共聚合体系中反应时间、反应温度、引发剂浓度等对PP隔膜接枝率和耐热性能的影响。在隔膜表面成功接枝P(DVB-co-MA)的基础上,探索了通过聚合物中DVB结构单元上未反应的双键与KH570发生共聚合反应,在隔膜表面引入SiO2粒子的改性方法。用SEM观察膜表面形貌,结果表明SiO2粒子确实结合到了隔膜中,且该改性方法对隔膜表面孔结构影响不大。热收缩率测试结果表明,改性后膜的尺寸稳定性明显提高,130℃下4 h热收缩率从12%可降低到4%。     

玉米淀粉接枝丙烯腈制备高吸水性树脂

用硝酸铈铵作引发剂,通过水溶液聚合法制得了玉米淀粉接枝丙烯腈高吸水性树脂.研究了引发剂用量、碱用量、反应温度以及反应时间等对吸水率的影响.得到的最佳反应条件为:引发剂与丙烯腈的摩尔比为4.5×10-3,碱与丙烯腈的摩尔比为1.32,反应温度25℃,反应时间3h.制得的高吸水性树脂在室温下30min每克吸蒸馏水和自来水分别约为其自身质量的1000倍和200g倍.     

磷酰胆碱类似物在有机硅材料表面的常压等离子体引发接枝改性研究

采用He常压辉光放电等离子体(APGDP)处理有机硅薄膜材料表面并引发2-甲基丙烯酰氧乙基磷酰胆碱(MPC)在其表面接枝聚合.通过ATR-FTIR对接枝前后膜表面的结构进行表征分析,确定MPC共价接枝到材料表面.改性后膜表面的接触角由101°下降到54°,在室温下保存15天后仍维持在58°左右,表明接枝MPC后有机硅材料获得高亲水性的表面,并能使这一性质较好地保持.接枝前后膜的力学性质变化不大.体外血小板粘附实验表明,接枝MPC后的材料表面能够显著抑制血小板的粘附和聚集,具有优良的血液相容性,可以作为一种新型医用生物弹性体.     

室温下海藻酸钙水凝胶与丙烯腈的快速接枝共聚

探索了室温下、短时间内,海藻酸钙水凝胶与乙烯基单体丙烯腈接枝共聚的反应条件.在室温(20℃)下,5g平均直径为2.5 mm的海藻酸钙水凝胶小球用8.5×10-2mol/L K2S2O8及7.0×10-2mol/LNaHSO3引发10min后,与浓度为6.22mol/L的丙烯腈反应30min,接枝率可达1520%.FTIR证实海藻酸钙水凝胶与丙烯腈之间发生了接枝共聚反应;而接枝共聚对水凝胶结构的影响,则用荧光测定法作了分析.     

淀粉与乙酸乙烯酯-丙烯酸乙酯的合成与应用研究

以玉米淀粉为接枝骨架,过硫酸铵为引发剂,丙烯酸乙酯(EA)和乙酸乙烯酯(VAc)为接枝单体,进行接枝共聚,制备淀粉基木材胶粘剂.研究了反应时间、反应温度、引发剂用量以及两单体配比对淀粉与丙烯酸乙酯-乙酸乙烯酯接枝共聚反应的影响.结果表明,当引发荆浓度9.7×10-3mol/L、反应温度65℃、反应时间3h、VAc和EA体积比为6:4时,可得到较高的接枝效率和接枝率.     

微波辐射海带接枝AA/AM合成高吸水树脂

以N,N-亚甲基双丙烯酰胺为交联剂,通过微波辐射法制备了海带接枝丙烯酸(AA)和丙稀酰胺(AM)高吸水树脂。讨论了单体配比、丙烯酸中和度、交联剂用量及引发剂用量、辐射时间等因素对吸水性能的影响,采用响应面分析法优化合成条件,并用红外光谱对产物进行了表征。研究结果表明:当海带用量35%,AM∶AA比例为20%,引发剂用量8.1%,交联剂用量0.052%,NaOH的中和度为79.3%,辐射时间45s时,制备的高吸水树脂的吸自来水倍率达176.62g/g。     

Peroxosalts initiated graft copolymerization of aniline onto wool fibre—a comparative kinetic study

Chemical grafting of aniline (ANI) onto wool fibre was carried out in aqueous acidic medium by using peroxosalts such as peroxodisulphate (PDS) and peroxomonosulphate (PMS) as an initiator for various [Monomer], [Initiator] and (fibre weight). It was observed that both R_h and R_g increased with increase in the concentration of each component. The chemical grafting was confirmed using FTIR spectroscopy, cyclic voltammetry (CV) and conductivity measurements.     

淀粉接枝丙烯酸高吸水树脂的性能研究

采用间歇法制备淀粉接枝丙烯酸的高吸水树脂,用红外光谱及XRD对共聚物结构进行了表征。在氧化淀粉的基础上探讨了引发剂用量、交联剂用量等反应条件的不同对吸水率、吸盐水率的影响并考察了交联剂用量对淀粉接枝率、接枝效率的影响。结果表明,引发剂用量占单体用量0.6%,交联剂用量占单体用量的0.8%,此时,树脂的吸水率最大,可达到每克树脂重量的562倍,吸盐水率可达到每克树脂重量的136倍,并且此时接枝效率可达98.28%。     

Bio-inspired tapered fibers for composites with superior toughness

The toughness of fiber-reinforced composites largely relies on crack bridging. More specifically, intact fibers left behind the tip of a propagating crack are progressively pulled out of the matrix, dissipating energy which translates into toughness. While short fibers are traditionally straight, recent work has showed that they can be shaped to increase the pullout strength, but not necessarily the energy to pullout. In this work we have modeled, fabricated and tested short fibers with tapered ends inspired from a high-performance natural material: nacre from mollusc shells. The main idea was to duplicate a key mechanism where a slight waviness of the inclusion can generate strain hardening and energy dissipation when the inclusion is pulled out. We have incorporated a similar feature to short fibers, in the form of tapered ends with well defined opening angles. We performed pullout tests on tapered steel fibers in epoxy matrices, which showed that the pullout of tapered fiber dissipates up to 27 times more energy than straight fibers. The experimental results also indicated the existence of an optimum taper angle to maximize work of pullout while preventing the brittle fracture of the matrix. An analytical model was developed to capture the pullout mechanism and the interaction between fiber and matrix. The analytical model can guide the design of tapered fibers by providing predictions on the influence of different parameters.     

Facile synthesis and characterization of flame retardant viscose fiber via graft copolymerization and chemical modification

A new strategy for synthesizing flame retardant viscose fiber (FR-VF) has been achieved by graft copolymerization of acrylonitrile (AN) onto viscose fiber and the subsequent chemical modification with hydrazine hydrate and zinc acetate. The structure of FR-VF was confirmed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectrometry (FTIR). The surface morphology of FR-VF was analyzed using scanning electron microscope (SEM). The results show that the graft copolymerization of AN onto viscose fiber and the reaction of VF-g-PAN with hydrazine hydrate and zinc acetate have been successfully carried out. The thermal properties tested by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques show that the thermal degradation rate of FRVF is slower than that of untreated FR-VF after 300°C. As a result, the char residue increases from 5.2% to 50.4% at 800°C. Furthermore, the burned FR-VF keeps original form as evidenced by SEM analysis, indicating that the obtained FR-VF possesses excellent thermal stability and char forming capability.     

氧化木薯淀粉与丙烯酸丁酯/醋酸乙烯酯的接枝共聚反应研究

以过硫酸铵为引发剂,以氧化后的木薯淀粉为接枝骨架,制备了氧化淀粉-丙烯酸丁酯-醋酸乙烯酯接枝共聚物.考察了氧化剂浓度对黏度及引发剂浓度、单体浓度、反应温度和反应时间对接枝率、接枝效率的影响.实验结果表明,在氧化剂浓度为0.04mol/L,引发剂浓度为9×10-3mol/L,单体浓度为1.0mol/L,反应温度为65℃,反应3h时,反应体系的接枝率和接枝效率较高.通过红外光谱对接枝共聚物进行了结构表征.     

CAN引发淀粉与MMA接枝共聚反应的研究

在研究玉米淀粉(corn starch,CS)与甲基丙烯酸甲酯(MMA)接枝共聚反应时发现,硝酸浓度为0.1mol/L、硝酸铈铵(CAN)/CS质量比为1/6、MMA/CS质量比为3/2是兼顾单体转化率(C)、接枝率(G)和接枝效率(GE)的最佳反应条件;同时发现,该反应中均聚物的生成不仅可由CAN直接引发,还可能因淀粉自由基或淀粉接枝物自由基的链转移而引发.