交联定形相变储能材料的研制

分别采用高密度聚乙烯( HDPE) 、高密度聚乙烯和低密度聚乙烯(LDPE) 1∶1的共混物作为基体材料,制备了不同凝胶率的交联定形相变材料, 讨论了材料的凝胶率与交联剂用量之间的关系, 并测定了材料的热性能。通过多次冷热循环实验, 研究了材料的稳定性。结果表明, 交联有利于改善定形相变材料的稳定性, 减少石蜡的渗出。高密度聚乙烯与低密度聚乙烯的共混体系更适合作封装材料。交联程度的不同对材料的相变温度和相变热均不产生影响。多孔填料如硅藻土的添加, 可以进一步减少石蜡的渗出, 提高材料的稳定性。      

交联剂存在下聚乙烯光敏化交联的动力学

从理论上推导了 LDPE-BP-TAIC 体系的光交联反应动力学方程,并与从抽提,溶胀,热延伸等实验所得的结果相比较而得到检验。通过分析,着重阐明了交联剂在光敏化交联过程中的促进机理;它既是能量捕捉剂,又是活性基团的载体和交联网络的纽带。高分子链以通过交联剂分子而相互连接成为交联的主要形式,从而使交联的速度和深度都得到显著的提高。     

LDPE固相接枝MAH及其产物在PA66/LDPE共混物中的应用

采用固相接枝法制备低密度聚乙烯(LDPE)接枝马来酸酐(MAH),并利用FT-IR表征了接枝产物的化学结构.研究了反应温度、引发剂用量、单体用量、界面剂用量以及反应时间对产物接枝率和交联度的影响.同时考察了接枝产物(LDPE-g-MAH)对聚酰胺66/低密度聚乙烯(PA66/LDPE)共混物的力学性能和形态的影响.结果...     

UHMWPE纤维的表面交联改性

选用三聚氰酸三丙烯酯(TAC)作为交联剂对超高分子量聚乙烯(UHMWPE)纤维进行紫外辐照交联改性,探讨了正庚烷浸泡时间、交联剂浓度、紫外线辐照时间等因素对UHMWPE纤维表面交联效果及纤维蠕变性能的影响。采用红外光谱、扫描电子显微镜及力学性能测试等多种手段对交联改性前后UHMWPE纤维的结构进行表征。结果表明,UHMWPE在正庚烷中的最佳浸泡时间为24h;紫外线辐照最佳时间为1.5 h;经交联改性后UHMWPE纤维的抗蠕变性能有较明显提高。     

聚4-乙烯基吡啶微凝胶的绿色合成

以4-乙烯基吡啶为单体,N,N’-亚甲基双丙烯酰胺为交联剂,在超临界二氧化碳(scCO2)中,通过沉淀聚合方法制备了交联聚(4-乙烯基吡啶)的干燥粉末。考察了反应体系的引发剂浓度、交联剂浓度、反应压力、反应时间等因素对聚合反应的影响。通过红外光谱(FT-IR)和扫描电镜(SEM)对聚合物组成及形貌进行了表征。实验表明,反应压力为14MPa,温度为70℃时,在适当交联剂用量下,可获得粒径约为0.5μm-1μm的干燥粉末,所得聚合物的产率大于90%。     

紫外光交联乙烯-醋酸乙烯共聚物/氢氧化镁无卤阻燃复合材料及其性能

研究了乙烯-醋酸乙烯共聚物(EVA)/氢氧化镁(MH)无卤阻燃复合材料在光引发剂下的紫外光交联及其相关性能。采用凝胶含量测定、热延伸试验、UL-94垂直燃烧试验、极限氧指数、扫描电镜、热重分析、拉伸测试等表征了复合材料的交联度、阻燃性能、热性能和力学性能。凝胶含量和热延伸测试结果证明紫外光可以对复合材料快速交联。光照交联后,材料的拉伸强度得到明显提高,断裂伸长率略有下降;极限氧指数、热重分析、扫描电镜测试表明光交联的复合材料试样比未交联的试样具有更好的阻燃性能和热稳定性。     

三元共聚高吸水性树脂的合成及研究

采用水溶性引发剂,以环氧氯丙烷为交联剂,用淀粉、部分中和的丙烯酸(钠)、丙烯酰胺为原料,用分步法进行交联接枝共聚,通过系统实验,选择最佳配比,制得吸无离子水3000(g/g),吸0.9％NaCl水溶液140(g/g)的高吸水性树脂。讨论了引发剂、交联剂、丙烯酰胺用量等合成条件与吸水性的关系。     

不饱和硅烷熔融挤出接枝聚乙烯的研究

采用熔融挤出法对低密度聚乙烯进行硅烷接枝,然后在催化剂二月桂酸二丁基锡存在进行水解交联,对接枝产物的熔体流动速率和交联样品的凝胶率的影响因素进行了系统的研究,接枝单体为乙烯基三乙氧基硅烷,主要引发剂为过氧化二异丙苯。     

新型水显影型感光树脂的性能

研究了一种新型水显影的感光树脂丙烯酸酯酚醛树脂季铵盐的溶解性、光交联性及交联膜的性能。结果表明，这种树脂季铵盐可溶于水和乙醇、二甲基亚砜、N，N—三甲基甲酰胺等极性有机溶剂；在与活性稀释性单体、光聚合引发剂及增效剂等配制成感光体系后，感光膜可用水显影，交联膜具有良好的硬度和附着性、耐酸碱及有机溶剂、耐热冲击。     

光交联聚乙烯的结晶形态及拉伸行为的研究

研究了 LDPE-BP-TAIC 体系光敏化交联聚乙烯的结构与性能及其相互关系。发现光交联对样品的结晶度影响很小,但能使结晶的规整性变差。这一形态上的变化引起了交联材料在室温下某些性能的细微改变,如模量降低、屈服消失。交联结构对材料性能的主要影响体现在高温时强度增加和高弹态的出现,大大提高了材料在力学上的稳定温度。     

Curing characteristics of shape memory polymers in 3D projection and laser stereolithography

The radical shift in 3D printing to fabricate soft active materials such as shape memory polymers (SMPs) has brought along other techniques in realising 4D printing. Stereolithography (SL) process has recently been one of the popular systems for printing SMPs. In this paper, the curing characteristics and behaviour of the SMPs fabricated via projection-type and laser-scanning-type SL process were analysed. Factors such as the UV exposure of the projection type and variation in resin compositions have significant differences in terms of energy density and curing depths when compared to the laser scanning type. Hence, theoretical calculations were made to determine the critical energy density and threshold penetration depth attainable, which enables newly developed SMP materials to be successfully printable using different types of UV-based 3D printing systems.     

Synthesis and properties of novel photosensitive poly(arylene ether sulfone) containing chalcone moiety in the main chain

A new series of photosensitive poly(arylene ether sulfone)s containing chalcone moiety in the main chain were synthesized from 4,4′-dihydroxychalcone (4DHC), 4,4′-difluorodiphenylsulfone (DFDPS) and bisphenol A (BPA). This series of polymers were characterized by ¹H NMR, FT-IR, UV spectroscopy, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The polymers were stable up to 400 °C, which indicates that the polymers possess good thermal properties. The polymers were found to be soluble in polar solvents and chlorinated solvents. However, the polymers were insoluble in hydrocarbons and in hydroxyl group-containing solvents. After the irradiation of UV light, the thin polymer film was crosslinked to give an insoluble film in the absence of a photoinitiator or sensitizers. The rate of photocrosslinking was also examined and discussed.     

多层绝热的间隔材料有效低温热导率测试研究

叙述了多层绝热的间隔材料玻璃纤维布、隔热纸的有效低温热导率测试方法,为薄层材料的有效低温热导率测试提供了一种方法,并对测试结果和影响因素,如叠层密度和层密度等进行了讨论分析。     

Water resistance of photocrosslinked polyvinyl alcohol based fibers

Electrospinning and photocrosslinking were combined in this study to prepare water-insoluble fibers of polyvinyl alcohol (PVA) with the styrylpyridinium (SbQ) pendent group. The PVA-SbQ exhibited high photosensitivity in a spectroscopic study. Electrospun PVA and PVA-SbQ fibers were soluble and totally dissolved after water immersion. UV irradiation of the electrospun mat led to a significant decrease in the mass loss of PVA-SbQ fibers in water. This water insolubility was confirmed by the stable morphology of PVA-SbQ fibers during water immersion.     

Microstructure and optical characterization of nanometric silicon films prepared by pulsed laser ablation

The effect of laser energy density, during pulsed laser ablation, on the microstructure and optical properties of silicon films has been investigated using techniques such as atomic force microscopy, scanning electron microscopy, X-ray diffraction, and UV–visible absorption/transmission spectroscopy. The thickness of prepared films increases with increase in laser energy density. The crystallite size and hence the crystallinity of prepared films have been estimated by X-ray diffraction and found to be dependent on laser energy density. The transmittance of films changes with laser energy density. The absorption coefficient of films has been found to be?>10⁴?cm^?1 in wavelength region 450–1100?nm. The band gap of silicon films has been determined as 2.27, 2.11, and 1.90?eV corresponding to laser energy density of 1.5, 2.5, and 3.5?J?cm^?2, respectively.     

Thermal furnace and Ultraviolet assisted curing impact on SiOCH spin-on ultra low dielectric constant materials

In recent years, the continuous progression of ultra-large scale integration has driven the emergence of technological solutions. In particular, major challenges have been faced for the fabrication of interconnect structures, where ultra low dielectric constants are required to decrease the parasitic capacitances between metal lines. Porous material, obtained using the porogen approach, is the main candidate investigated. The curing process is critical for achieving a good control of final film structure. The integration of such material requires a good chemical and mechanical stability, particularly to maintain the structure integrity during the stressing steps: chemical mechanical polishing and packaging. In this work, Ultraviolet assisted thermal cure (or UV curing) is investigated as an alternative solution to the conventional thermal curing. Chemical and physical analyses reveal that the best porogen removal efficiency and the enhancement of matrix crosslinking are achieved when the material is UV cured. This crosslinking improvement (as indicated by higher Si-O-Si bond density in the fourier transformed infra-red spectra) can be correlated to better mechanical properties. Significantly better electrical properties (dielectric constant, leakage current and breakdown voltage) are obtained with better integrity (no moisture uptake after 1 week storage in humid atmosphere 85 °C/85% relative humidity) when the dielectric is optimally cured. Porosity evaluation reveals similar results between both curing processes with slightly larger pore size in the case of the UV cured film. Finally, a basic model is described to illustrate how the UV assisted thermal cure may improve the crosslinking in comparison to the thermal curing. Selective UV action is proposed to explain the curing process kinetics.     

水溶性光敏聚丙烯酸酯类光交联的研究

本工作合成了一系列不同丙烯酸酯和丙烯酸组成的共聚物,其中丙烯酸单元含量在13～20％之间,然后使之与四基丙烯酸缩水甘油酯反应,形成带有甲基丙烯酸酯侧链的预聚体。用红外光谱法检测1640cm~(-1)处双键峰的变化,测定了体系的光交联速度。结果表明,光交联过程及固化膜中剩余双键含量与预聚体的性质及交联剂官能团的性能有关。预聚体与交联剂官能团量的比例,对固化速度有明显影响。以等摩尔比反应时,速度最快。不同光敏剂的引发效率为苯乙酮衍生物>安息香醚类>芳香酮/胺。     

Encapsulation of organic UV ray absorbents into layered double hydroxide for photochemical properties

Organic–inorganic nanohybrids, 3,4-dihydroxycinnamic acid/layered double hydroxide (CA/LDH), 4-hydroxy-3,5-dimethoxycinnamic acid/layered double hydroxide (SA/LDH), and 3-amino-5-triflouromethylbenzoic acid/layered double hydroxide (FBA/LDH) have been synthesized by co-precipitation reaction of organic ultraviolet (UV) ray absorbents such as 3,4-dihydroxycinnamic acid, 4-hydroxy-3,5-dimethoxycinnamic acid, 3-amino-5-triflouromethylbenzoic and Zn₂Al layered double hydroxide (LDH). Detailed structural and absorption properties of the nanohybrids were studied by using X-ray diffraction (XRD), FT-IR and UV-Vis transmittance spectra which revealed that organic UV absorbents have been intercalated into the interlayer spaces of LDH and all nanohybrids showed excellent UV ray absorption. All the nanohybrids showed a lower catalytic activity as compared to the net organic UV ray absorbents by applying air oxidation to castor oil.     

Growth, photoluminescence, and field emission of hierarchical ZnO nanostructures

Hierarchical ZnO nanostructures with the morphology of sleeve-fishes have been fabricated on Si substrate through vapor phase transport at 850 degrees C. Studies find that each nansleeve-fish is composed of a screw-shaped microrod and some tapering nanowires grown on the microrod, all of which grow along the [0001] direction. Photoluminescence spectra exhibits strong UV emission around 385 nm without any green emissions detected, indicating that the high-quality ZnO nanostructures with low level of oxygen vacancies are obtained in our experiment. Field-emission measurements on the nanosleeve-fishes show a turn-on field as low as 2.2 V/microm at a current density of 0.1 microA/cm(2) with a anode-sample separation of 600 microm, and the emission current density reached 1 mA/cm(2) at an applied field of about 5.8 V/microm. The excellent field emission properties from such kind of nanostructures make them promising candidates for further applications in FE microelectronic devices.     

Synthesis and characterization of partially biodegradable and thermosensitive hydrogel

A partially biodegradable and thermosensitive hybrid hydrogel network (DAN series) based on dextran-allylisocyanate (Dex-AI) and poly(N-isopropylacrylamide) (PNIPAAm) was synthesized via UV photocrosslinking. These hybrid hydrogels were characterized in terms of their chemical structure, thermal, mechanical, morphological and temperature-induced swelling properties. The effect of the composition ratio of Dex-AI to PNIPAAm on such properties were examined. The differential scanning calorimetry data show that this Dex-AI/PNIPAAm hybrid network has an increased lower critical solution temperature (LCST) and glass transition temperature (Tg) with an increase in the Dex-AI content. The interior morphology of these hybrid hydrogels revealed a decreased porous microstructure with an increase in the Dex-AI content in the hybrid network. Furthermore, if the Dex-AI composition became too high, a distinctive network structure with two different microporous structures appeared. The mechanical properties of these hybrid hydrogels also increased with an increase in the Dex-AI content. The temperature dependence of the swelling ratio, the deswelling kinetics as well as the reswelling kinetics was also characterized by gravimetric method. When comparing with a normal PNIPAAm hydrogel, these Dex-AI/PNIPAAm hybrid networks, due to the presence of Dex-AI moiety, also show improved temperature-induced intelligent properties, such as the faster and controllable response dynamics, which may find promising applications in a wide variety of fields, such as biomedical and bioengineering fields.