Acrylate Elastomer Toughened and UV Stabilized Polyoxymethylene

Acrylate elastomer (ACE) synthesized ourselves was mixed with antioxidative and UV stabilizer into polyoxymethylene (POM) matrices to investigate the effects of the ACE phase on the mechanical properties and UV stability of POM. For comparison, POM blended with same amount of TPU instead of ACE was used. Dispersion of the elastomer particles in POM matrices was investigated using SEM micrograph. Crystallinities of the specimen before and after UV ageing were also measured. The surface molecular weight and the mechanical properties of modified POM after UV ageing were determined. The result showed that excellent mechanical properties of the POM composites after UV‐irradiation could be obtained by blending with ACE.     

Photo-Oxidative Stabilization Effect of a Reactive Hindered Amine on Monomer Casting Nylon-6

Monomer casting (MC) nylon-6 was polymerically modified by grafting 4-amino-2,2,6,6-tetramethylniperidine (TEMP), as a reactive hindered amine, onto its chain so as to improve the compatibility and stability of the stabilizer in the polymer matrix. The long-term aging of MC nylon-6 under UV irradiation indicated that the grafted sample of MC nylon-6 had lower gel content than that of the pure sample, and only a slow change in the reduced viscosity was observed. The carboxyl concentration of the grafted sample was lower than that of the pure sample, and its terminal amine group concentration was relatively higher during the whole aging process, presenting a more stable chemical structure. The delayed oxidation exothermic peak and increase of oxidation induction time (OIT) suggested that the grafted TMEP was stable in the matrix of nylon-6 after long-term UV aging. Decreasing crystallization ability after aging was observed for the pure sample of MC nylon-6, while a relatively stable crystallization behavior was observed for the grafted samples, indicating that TEMP can inhibit the structural change of MC nylon-6 during UV irradiation.     

Comparison of the protection effectiveness of acrylic polyurethane coatings containing bark extracts on three heat-treated North American wood species: Surface degradation

High temperature heat-treatment of wood is a very valuable technique which improves many properties (biological durability, dimensional stability, thermal insulating characteristics) of natural wood. Also, it changes the natural color of wood to a very attractive dark brown color. Unfortunately, this color is not stable if left unprotected in external environment and turns to gray or white depending on the wood species. To overcome this problem, acrylic polyurethane coatings are applied on heat-treated wood to delay surface degradations (color change, loss of gloss, and chemical modifications) during aging. The acrylic polyurethane coatings which have high resistance against aging are further modified by adding bark extracts and/or lignin stabilizer to enhance their effectiveness in preventing the wood aging behavior. The aging characteristic of this coating is compared with acrylic polyurethane combined with commercially available organic UV stabilizers. In this study, their performance on three heat-treated North American wood species (jack pine, quaking aspen and white birch) are compared under accelerated aging conditions. Both the color change data and visual assessment indicate improvement in protective characteristic of acrylic polyurethane when bark extracts and lignin stabilizer are used in place of commercially available UV stabilizer. The results showed that although acrylic polyurethane with bark extracts and lignin stabilizer was more efficient compared to acrylic polyurethane with organic UV stabilizers in protecting heat-treated jack pine, it failed to protect heat-treated aspen and birch effectively after 672 h of accelerated aging. This degradation was not due to the coating adhesion loss or coating degradation during accelerated aging; rather, it was due to the significant degradation of heat-treated aspen and birch surface beneath this coating. The XPS results revealed formation of carbonyl photoproducts after aging on the coated surfaces and chain scission of CN of urethane linkages.     

聚丙烯/抗老化剂复合体系的γ-射线辐照降解研究

研究了聚丙烯(PP)及含有受阻酚类抗氧剂和受阻胺类光稳定剂复合体系的PP复合物经过γ-射线辐照后发生的结构变化及抗老化剂所起作用。实验利用红外光谱(FTIR)和示差扫描量热法(DSC)对PP的结构变化进行了系统表征。研究结果表明,当辐照剂量较小(50 kGy)时,纯PP及其复合物体系均未发生明显降解;当辐照剂量较大(≥50 kGy)时,PP及其复合物的羰基指数迅速提高,二者的结晶温度和熔融温度大幅度降低,说明PP发生了严重降解。在相同γ-射线辐照剂量条件下(≥50 kGy),PP复合物的羰基指数高于纯PP,而结晶温度以及熔融温度低于纯PP,表明高辐照剂量下抗老化剂复合物的存在不但没有阻止聚丙烯的降解,反而加快了降解的速率。     

龙岩高岭土的苯乙烯原位聚合插层的FTIR和XRD研究

以福建龙岩高岭土为主要原料,用沉降的方法得到平均粒径为1.75μm的沉降高岭土。用DMSO插层高岭土,后用苯乙烯单体取代前驱体中的DMSO分子,产物经四氯化碳洗涤后,在马弗炉中270℃本体聚合2h得到高岭土/聚苯乙烯复合物。红外在1 453,1 499和1 606cm-1的吸收振动峰证明了聚苯乙烯的存在。XRD结果显示高岭土层间距0.712nm,苯乙烯聚合后片状结构已经被剥离。热重显示聚苯乙烯占复合物质量的40%,还有约5%的未除去DMSO和4.8%的羟基,估算出高岭土∶聚苯乙烯=1.375∶1(质量比)。扫描电镜也验证了这种剥离。     

UV irradiations induce variations of ferromagnetism and resistivity in nitrogen doped ZnO films

The saturated room-temperature ferromagnetism observed from nitrogen-doped zinc oxide (ZnO:N) increases significantly after ultraviolet light (UV) irradiation. During the period of irradiation, the resistivity as a function of time decreases dramatically and reaches saturation eventually. The log scale of the resistivity as a function of irradiation time reveals two sequential linear lines with different slops. Both of linear lines correspond to different dominant transports which result from some electrons recombination captured by the impurity band induced from the N doping. Similarly, the reverse properties of resistivity change appear at the samples after turning off the UV irradiation. The experiments convince us of the magnetic mechanism arising from the Coulomb excitation.     

The effect of UV irradiation on nanocrysatlline zinc oxide thin films related to gas sensing characteristics

The effect of ultraviolet (UV) light irradiation on the nanocrystalline ZnO thin films was investigated. The degree of crystallinity, electrical conductivity, optical properties and surface properties of ZnO thin films were measured as a function of UV irradiation time. It was found that the degree of crystallinity and electrical properties of ZnO films were affected by UV irradiation, however, no noticeable change in the surface morphology was observed. The gas sensing properties of as-deposited and UV irradiated films were also measured. It was observed that the gas sensing properties were affected by the UV irradiation. The irradiation time less than 5 min has improved the sensor while the irradiation time more than 5 min degraded the sensor characteristics for a UV power density of 2.45 W cm⁻².     

侧链含查尔酮基团的聚(甲基)丙烯酸酯的光交联特性

采用红外光谱、热重分析、紫外光谱和荧光光谱对侧链含查尔酮基团的聚（4-甲基丙烯酰氧基-4'-二甲氨基查尔酮）（PMADMAC）和聚（4-丙烯酰氧基查尔酮）（PAC）的光交联特性进行了研究。随着光照时间的增加,PMADMAC和PAC聚合物光致环加成反应迅速进行,波长短的紫外线更易使得聚合物发生[2+2]环加成反应。与溶液状态相比,固体薄膜状态下的光交联反应速率较慢。PMADMAC聚合物更容易发生光致环加成反应,其光交联速率要比PAC聚合物快,环加成反应也更彻底。采用荧光光谱研究了聚合物的发光特性,发现PAC聚合物无荧光,而PMADMAC聚合物具有溶剂极性敏感的荧光特性。在PMADMAC聚合物的稀溶液中,随着365 nm紫外光照时间的增加,荧光强度迅速降低,其荧光特征波长在紫外光照射后发生蓝移。 PMADMAC和PAC聚合物的热稳定性较好,光交联后形成热不稳定的环丁烷结构,其热稳定性有所降低。     

Surface and interfacial properties of PVDF/acrylic copolymer blends before and after UV exposure

Morphological and chemical properties of both the surface and interface of poly(vinylidene fluoride)/poly(methyl methacrylate)-co-poly(ethyl acrylate) (PVDF/PMMA-co-PEA) blend films have been investigated before and after the samples were exposed to ultraviolet (UV) irradiation using a xenon arc lamp at 50 °C and 9% relative humidity (RH) for 7 months. Surface and interfacial morphologies were studied by atomic force microscopy (AFM). Chemical composition information was obtained by confocal Raman microscopy, attenuated total reflection-FTIR spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and contact angle measurements. Results show an enrichment of the PVDF material at the air surface, while the acrylic copolymer enriches the interface. Blends having greater than 50% mass fraction of PVDF show little change in the surface morphology after UV exposure for 7 months. However, for a lower PVDF content, blends exhibit significant degradation of PMMA-co-PEA copolymer and a much rougher surface after UV exposure. Microstructural changes in the PVDF spherulites are also observed after UV degradation. It is found that the surface and interfacial morphologies are correlated with the chemical properties.     

SU-8去胶工艺对电铸Ni材料力学性能的影响（英文）北大核心CSCD

SU-8负胶具有优异的力学性能、抗化学腐蚀性、热稳定性和生物兼容性,在MEMS工艺和器件中得到广泛应用。镍金属具有良好的力学性能和抗腐蚀性,因此常用来制作MEMS器件。在MEMS执行器中,弹性元件常采用电铸镍制作。SU-8经过经曝光显影后形成致密的交联网络结构是一种高分子聚合物,这种聚合物非常稳定,不溶于强酸强碱及常见的有机溶剂,尤其是在电铸金属结构后的SU-8胶的去除更为困难。目前的SU-8去胶技术,按去胶原理可分:机械物理去胶技术和氧化去胶技术。氧化去胶技术可以有效去除SU-8胶,但氧化去胶方法不同程度地损坏电铸金属,使其力学性能与去胶前相比发生显著的变化。因此需要研究去胶对Ni金属弹性模量的影响,从而为执行机构设计提供准确的基本数据。针对目前运用比较普遍的两种去除SU-8胶方式:微波等离子下游化学刻蚀和强碱熔盐浴,分别进行了去胶实验,对去胶前后的电铸Ni金属进行了弹性模量和硬度测试。实验结果表明,电铸镍的杨氏模量在经过微波等离子下游化学刻蚀后下降18%,而经过强碱熔盐浴后下降36%,但硬度下降不明显。     

Study on the Long-Term Acid Rain Aging Behaviour of Polyamide 6

The long-term acid rain aging behavior of polyamide 6 (PA6) was studied in aqueous solution with pH = 1 at 40°C in comparison with a stabilized sample (Stabilizer: 0.2wt% Irganox 1010, 0.2wt% Irgafos 168, 0.3wt% Tinuvin 770 and 0.3wt% Tinuvin 234). The aging can be described as a succession of three stages. The first one corresponded to the physical absorption of water until equilibrium while the chemical degradation can be neglected resulting in a drop of the mechanical strength and an increase of the toughness of the sample of PA6. The hydrolysis reaction of the amido link of PA6 predominated during the middle and last stage of aging, resulting in a decrease of all the mechanical properties. The reduced viscosity of PA6 decreased monotonically during the whole aging process. The end amine group concentration could not be detected due to its reaction with acid. The carboxylic acid came not only from the carboxylic acid end group produced by the degradation of the sample, but also from the acid rain. The stabilizers didn't have any effect of the anti-acid rain degradation of PA6.     

In situ atomic force microscopy studies of reversible light-induced switching of surface roughness and adhesion in azobenzene-containing PMMA films

Thin films in the range 40-80 nm of a blend of PMMA with an azobenzene derivative have been studied directly during UV and blue light irradiation by atomic force microscopy (AFM), revealing highly reversible changes in the surface roughness and the film adhesion. UV light induces an ≈80% increase in surface roughness, whereas illumination by blue light completely reverses these changes. Based on the observed surface topography and transition kinetics a reversible mass flow mechanisms is suggested, where the polarity changes upon switching trigger a wetting-dewetting transition in a surface segregation layer of the chromophore. Similar AFM measurements of the pull-off force indicate a decrease upon UV and an increase after blue light illumination with a complex kinetic behavior: a rapid initial change, attributed to the change in the cis isomer fraction of the azobenzene derivative, and a more gradual change, indicative of slow structural reorganization.     

Long-Term Hydrothermal Aging Behavior and Life-Time Prediction of Polyamide 6

The long-term hydrothermal aging behavior of polyamide 6 (PA6), with and without stabilizers at 100% relative humidity/90ºC was studied. It was found that the first stage of aging was the Fickian process and corresponded to the physical absorption of water until equilibrium, resulting in slight change of reduced viscosity and chemical structure of the sample of PA6. The second stage of aging was the initiation process of hydrolytic degradation of PA6, which resulted in a decrease of reduced viscosity and increase of end group content. In the final stage of aging, the relative weight gain (W_r) dropped, the reduced viscosity decreased monotonically, and end groups increased continuously, resulting from the hydrolysis of amido links and molecular degradation of PA6. The presence of four types of stabilizers effectively weakened the oxidation reaction and resulting molecular degradation of PA6 during aging. The lifetime of PA6 in a hydrothermal environment was predicted through a method based on the Arrhenius model by considering both temperature and humidity as environmental factors, and, furthermore, was predicted through the time–temperature superposition method.     

低能N+ 离子预处理对水稻UV-B辐射的当代损伤效应的影响

采用3种不同注量的N离子对供试材料进行了离子注入预处理, 再用10.08 kJ/(m2d1)增强UV-B辐射对其幼苗进行辐照试验, 测定了过氧化物酶（POD）活性、 过氧化物歧化酶（SOD）活性、 过氧化氢酶（CAT）活性、 丙二醛（MDA）含量、 还原型谷胱甘肽（GSH）含量和可溶性糖含量的变化。 研究结果表明: 经N离子注入预处理的水稻材料受到UV-B辐射时其POD和SOD活性明显升高, 并在注量为2.0×1017 ions/cm2时活性达到最强; CAT活性和MDA含量明显降低, GSH含量显著增加, 而可溶性糖的含量则变化程度很小。 从这些研究结果可以看出, 经过一定注量离子注入预处理的水稻材料当受到UV B辐射时能产生较强的抗氧化能力和防御能力,而且抗氧化系统优于碳水化合物系统而先于表达。 由此可见, 离子注入预处理对水稻UV-B辐射的生物学效应的影响相当明显。 The seedlings of rice (xindao18) were exposed to UV B (10.08 kJ/(m2d1 )) irradiation follo wing the pretreatment with three different implantation dosages of low energy N+ ions. Changes in the levels of the superoxide (POD),superoxide dismutase (SOD),catalase (CAT), malondialdehyde (MDA),glutathione (GSH) and soluble sugar were measured. The result showed that the UV-B irradiation on the seedlings of rice pretreated with low energy ions implantation could lead to increase activities in POD and SOD,and the maximum appeared on the dose of 2.0×1017 ions/cm2. Meanwhile,it made the content of GSH increased, and caused the activity of CAT and the content of MDA to be decreased. But there was no obvious change in soluble sugar. It was suggested that the rice pretreated by low energy ion implantation could enhance the antioxidation capacity and defensive ability when irradiated by UV-B, and the antioxidation system could be induced earlier than carbohydrate system. Therefore, the biological effects of UV-B irradiation on rice pretreated by low energy ion implantation were quite obvious.     

Effects of Beta Irradiation,Copolymers, and Blends on the Transformation Rate of Polybutene-1

The beta irradiation of polybutene-1 (PB-1) and its random copolymers with ethylene results in sample degradation without chain cross-linking. The crystal structures of both homopolymer and ethylene copolymers were phase I (I), except that for samples of short time irradiation, after melting, where phase II (II) was also present. The sample crystallinity decreased from 64% to a low of 45% in the irradiated samples for the condition used. The crystal size/perfection of the transformed I was slightly lower than that of parent II. The beta irradiation increased the transformation rate of II → I but to a lower extent than did the amount of ethylene in the copolymers. IR analysis confirmed that electron irradiation resulted in chain scission and a decrease of ?CH₂? and ?CH₃ groups. The mechanical properties decreased with increasing ethylene content and irradiation dose.     

准备层温度对黄光LED光电特性和老化性能的影响

研究了InGaN/GaN超晶格准备层的生长温度对Si衬底GaN基黄光LED光电特性和老化性能的影响。研究发现准备层生长温度较高的样品外量子效率高于准备层生长温度较低的样品。500 mA电流下老化1000 h后,准备层生长温度较高的样品的光衰相对更大。老化前后100 K的电致发光光谱显示高温生长的样品老化后的空穴注入途径发生变化;老化后光衰大的样品非辐射复合中心增加的程度更大。荧光显微镜观察到两个样品老化前均出现大量暗斑,高温样品的颜色更深更黑,低温样品颜色则相对较浅且呈红色。老化后高温样品的暗斑数量有所增加,而低温样品数量变化不大,这可能也是导致超晶格温度高的样品光衰更大的原因之一。     

Metal adsorption of gamma-irradiated carboxymethyl cellulose/polyethylene oxide blend films

Blend films of different ratios of carboxymethyl cellulose (CMC)/polyethylene oxide (PEO) were prepared by the solution casting method. To investigate the effect of irradiation on all properties of prepared blend, it was exposed to different gamma irradiation doses (10, 20, and 30?kGy). Physical properties such as gel fraction (GF) (%) and swelling (SW) (%) were investigated. It was found that the GF (%) increases with increasing irradiation dose up to 20?kGy, while SW (%) decreases with an increase in the irradiation doses for all blend compositions. Moreover, the structural and mechanical properties of the prepared films were studied. The results of the mechanical properties obtained showed that there is an improvement in these properties with an increase in both CMC and irradiation dose up to 20?kGy. The efficiency of metal ions uptake was measured using a UV spectrophotometer. The prepared films showed good tendency to absorb and release metal ions from aqueous media. Thus, the CMC/PEO film can be used in agricultural domain.     

紫外线激发后KCl:Cu+的光激励发光

用固相反应法制备了KCl：Cu^＋多晶样品。经紫外光辐照后，用560nm的光照射能产生近紫外蓝光的光激励发光。研究表明，Cu^＋作为发光中心，经紫外光辐照后并没有产生Cu^＋到Cu^＋的变价，即Cu^＋不是空穴俘获中心，而阴离子空位充当电子陷阱。当激发后的样品受到光激励时，电子与空穴中心或Vk心复合后将能量传递给Cu^＋离子，产生d-s跃迁的特征发射。     

Surface modification of Makrofol-DE induced by α-particles

In the present work, Makrofol DE samples were irradiated with different doses of alpha particles. The optical and mechanical modifications in the alpha-irradiated Makrofol samples as a function of alpha irradiation time have been investigated. Different characterization techniques, UV–vis spectroscopy, photoluminescence spectroscopy and Vickers micro hardness tester have been used. UV–vis spectra of bombarded samples reveal that the optical absorption increases with increasing the irradiation time. The direct and indirect optical band gap was found to decrease from 3.4 and 2.81?eV for pristine sample to 3.1 and 2.35?eV for that bombarded with alpha particles at the highest irradiation time (15?h), respectively. The number of carbon atoms per conjugated length (N) and the number of carbon atoms per cluster (M) have been estimated. An increase in both N and M with increasing the irradiation time was noticed. A remarkable decrease in PL intensity with increasing the alpha irradiation time was observed. This decrease is attributed to ion beam-induced change in molecular structure and/or defects in the modified layer. The surface hardness for unmodified and modified polymeric material has been studied.