显微红外光谱法研究聚丙烯纳米复合材料的光氧化降解

采用显微红外(AIM)光谱法,结合偏光显微镜(POM)和扫描电子显微镜(SEM),对聚丙烯/碳酸钙(PP/CaCO₃)和聚丙烯/二氧化硅(PP/SiO₂)纳米复合材料中光氧化降解沿深度的分布进行了研究。结果表明,无论是纯聚丙烯还是聚丙烯纳米复合材料,试样的光氧化降解都是氧扩散控制过程,由表面逐渐向内部发展。纳米碳酸钙和纳米二氧化硅的加入都显著地促进了PP基体的光氧化降解,二氧化硅的影响更为严重。纳米填料的含量越高,复合材料的氧化程度也越高,但氧化层的厚度却基本不变,都在200 μm左右,当样品表面严重老化至表面脱落后,氧化继续向内部进行。氧化层的厚度主要是由试样成型过程中形成的表面过渡区的厚度决定的。     

衰减全反射红外光谱技术(ATR-FTIR)在琥珀检测与研究中的应用

红外光谱分析是矿物材料研究中常用的一种表征手段,而衰减全反射红外光谱(ATR-FTIR) 由于其快速、无损且能够进行微区检测等优势在而被广泛使用。以不同产地琥珀、柯巴树脂和覆膜处理琥珀为研究对象,通过BRUKER LUMOS独立式红外显微镜对样品的ATR-FTIR光谱进行测试与分析。结果表明：ν(CC)伸缩振动在1 643 cm-1和δ(芳C—H)弯曲振动在889 cm-1两处的红外吸收谱带均出现在多米尼加和俄罗斯琥珀中;由ν(C—O)伸缩振动在1 300～925 cm-1范围内的红外吸收谱带对于琥珀的产地具有一定的指示意义;ν_as(CH₂)不对称伸缩振动在3 080,1 643和887 cm-1三处的红外吸收谱带为柯巴树脂所特有,具有重要的鉴定意义;覆膜琥珀显示琥珀和人工树脂混合红外光谱,除琥珀特有的红外光谱之外,760和702 cm-1红外吸收谱带为人工树脂中γ(芳C—H)面外弯曲振动所致。ATR-FTIR在琥珀的成因、产地及优化处理品种的检测具有重要的意义。     

利用X射线衍射技术与红外光谱分析真菌侵蚀的木材

为了弄清真菌侵蚀木材的微细结晶构造与主成分官能团的变化,利用X射线衍射技术和红外光谱研究了分别经过黄孢原毛平革菌(PC)和棉腐卧孔菌(PP)侵蚀不同时间后毛白杨木材的结晶度、晶胞内层间距、晶粒宽度和主成分官能团的变化情况。结果表明：(1)PC与PP的侵蚀对木材纤维素结晶区的晶格构造没有影响,纤维素结晶区衍射2θ角和层间距基本保持不变,但纤维素结晶度和晶粒宽度随侵蚀时间增加而呈减小的趋势,并且受PP侵蚀的要比受PC侵蚀的明显,表明PP侵蚀对纤维素的破坏程度要大于PC侵蚀;(2)半纤维素在侵蚀过程中其木聚糖被不同程度的降解,使得产物中羰基含量增加,PC与PP对半纤维素的降解效果与纤维素几近相同;(3)木质素受PC侵蚀后苯环被氧化裂解生成链烃,而受PP侵蚀的变化不明显。     

络合物形成对电子-声子耦合的影响

测量了室温(20℃)条件下极性溶剂1, 2-二氯乙烷-碘溶液中的β胡萝卜素 紫外-可见吸收光谱和拉曼光谱. 结果表明, 生成络合物的β胡萝卜素在460 nm处的紫外-可见吸收峰消失, 并在1000 nm处出现β胡萝卜素与碘形成络合物的吸收峰, 致使514.5 nm激光激发时察觉不到络合物中β胡萝卜素离子CC键的共振拉曼光谱.而溶液中没有形成络合物的β胡萝卜素CC键拉曼散射截面随络合物浓度增加而减小, 拉曼光谱线宽增加, π电子-声子耦合系数增加, 其机理是随络合物增加溶液混乱程度增加、β胡萝卜素分子结构有序性减小所致, 且可以用“相干弱阻尼电子-晶格振动”、“有效共轭长度”、“振幅模型”等理论给予解释. 关键词： 络合物 电子-声子耦合 共振拉曼光谱     

杉木光变色的FTIR光谱分析

暴露于室外环境的木材或木制品,由于受气候因子的作用其表面性状和品质发生劣化,主要表现为木材变色,大大降低其利用价值。以人工林杉木为研究对象,利用模拟太阳辐射的氙光衰减仪对木材表面进行光劣化处理,采用傅里叶变换红外(FTIR)光谱技术分析了木材光变色过程中化学成分的变化,建立了木材变色与化学成分变化之间的关系。试验结果表明:光照过程中,1 512,1 462,1 269和1 227 cm-1处与木质素有关的吸收峰强度明显降低,1 720～1 735 cm-1处非共轭羰基伸缩振动吸收明显增强,木材表面发生光氧化反应,木质素明显降解,同时不断有新的羰基化合物生成;光照80 h内,木质素的降解以及羰基化合物的生成速度较快,此后变化不显著;木材表面部分多糖物质(纤维素和半纤维素)被氧化降解。研究表明,木材光照过程中的颜色变化(ΔE*)与木质素的降解以及羰基官能团的生成密切相关。     

聚丙烯/有机改性蒙脱土纳米复合材料的光氧化降解研究

研究了聚丙烯/有机改性蒙脱土(OMMT)纳米复合材料在365 nm紫外光辐照下的光氧化降解过程中的结构变化。主要利用红外光谱方法进行表征。在辐照初期(紫外光辐照时间小于11 h),复合体系的光氧化降解速率大于纯聚丙烯体系;随着辐照时间的延长(大于11 h),复合体系的光氧化降解速率小于纯聚丙烯体系。主要原因是蒙脱土既有光屏蔽作用,又有加速光氧化降解的作用,这两种作用共存,但在辐照初期,催化光降解作用占主导地位,随着辐照时间延长,光屏蔽作用占主导。蒙脱土的含量对聚丙烯的光氧化降解速率也存在影响。另外,蒙脱土的加入对聚丙烯光氧化降解产物也产生影响,羧酸类及酸酐类产物增多,酯类产物减少。     

显微红外光谱法研究聚乙烯复合材料光氧化的深度分布

采用显微红外光谱法结合表面形貌分析研究了分别填充碳酸钙、绢英粉、云母、高岭土和硅藻土的高密度聚乙烯(HDPE)的自然光氧化随深度的分布。研究结果表明无机填料对HDPE光氧化的深度分布有很大的影响。填充碳酸钙的HDPE从表面到内部都没有明显氧化发生。而填充绢英粉、云母、高岭土和硅藻土的HDPE从表面到内部羰基指数逐渐减小,氧化深度都在150 μm以上。HDPE复合材料沿深度方向的氧化情况与其断面裂纹的产生情况吻合。结合无机填料的紫外吸收特性讨论了它们对HDPE光氧化的影响机理。     

使用圆二色性光谱和红外光谱研究冬小麦麸皮抗冻蛋白的二级结构

使用圆二色性光谱和红外光谱技术对冬小麦麸皮抗冻蛋白的二级结构进行了研究。由于冬小麦麸皮抗冻蛋白在酰胺Ⅰ带和Ⅲ带位置中,各个特征峰相互叠加,因此采用Gausse峰型对圆头峰进行拟合、解析,判断其α-helix,β-sheet,β-turn和Random coil的相对含量;同时对圆二色性光谱获得的结构信息,采用按照Chen-Yang原理和最小二乘法编写的程序计算了冬小麦麸皮抗冻蛋白的二级结构。最后,讨论了两种检测方法结果差异的原因,为冬小麦麸皮抗冻蛋白抗冻机理的研究奠定基础。     

毛竹材表面光化降解的FTIR和XPS分析

竹材光变色和光化降解过程比较复杂。该文以我国资源丰富的毛竹为研究对象,利用氙光衰减仪对竹材进行表面劣化处理,采用傅里叶变换红外光谱(FTIR)和X射线光电子能谱分析(XPS)对竹材表面化学组成和结构的变化进行表征。XPS测试结果表明,竹材表面光劣化处理后其O元素含量及氧碳比(O/C)明显增加;从C原子结合形式来看,C1(C—C)含量减少,C2(C—O)含量增加,C3(CO)和C4(OCO)含量增加明显,C的氧化态显著升高。FTIR分析表明,光劣化处理使得与木质素有关的吸收峰(如1 604,1 512及1 462 cm-1)强度明显降低,木质素发生降解,同时1 735 cm-1处非共轭羰基吸收峰强度明显增强,表明有新的羰基类物质生成,竹材表面发生光氧化反应。竹材表面的多糖物质(纤维素和半纤维素)受光劣化影响较小,其表面多糖相对含量在劣化处理后明显提高。     

297 K和0.13～1 GPa压力下菱镁矿的拉曼光谱实验研究

在T=297 K,130 MPa＜P＜967 MPa下用拉曼光谱对菱镁矿1 094 cm-1峰随压力变化关系进行了测量,结果表明随着压力增大,1 094 cm-1峰往高波数方向移动,其波峰位置与压力关系为：ν(cm-1)=0.007 44×P(MPa)+1 093.3。在T=297 K,130 MPa＜P＜967 MPa时,菱镁矿可用作地质压力计。压力与菱镁矿1 094 cm-1峰偏移量关系为：P(MPa)=125.8×(Δν_p)_{1 094}+124.7,(1 094 cm-1＜ν_p＜1 101 cm-1)。在实验的压力范围内未观察到菱镁矿的相变和有机物的生成。     

MWCNTs Supported N,N′-Dicyclohexyl-1,5-diamino-2,6-naphthalenedicarboxamide: A Novel β-Nucleating Agent for Polypropylene

N,N′-Dicyclohexyl-1,5-diamino-2,6-naphthalenedicarboxamide (NA), a highly efficient and selective β-nucleating agent for isotactic polypropylene (iPP), was synthesized and chemically supported on the surface of multiwall carbon nanotubes (MWCNTs) via an amidation reaction. The β-nucleation ability of NA, itself, is superior to the commonly used, highly efficient, and selective β-nucleating agents, e.g., commercial rare earth WBG-and aryl amide derivative TMB-5, as proved by the results of wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). The effect of MWCNTs supported NA (MWCNT-NA) on the crystallization and melting behavior of iPP was investigated by means of WAXD and DSC. The results show that the MWCNTs supported NA can effectively induce the formation of β-crystals in iPP/MWCNT-NA, although the grafting degree of NA onto the surface of MWCNTs could still to be improved.     

拟除虫菊酯光解产物的红外图谱研究

本文研究了胺菊酯、甲醚菊酯、丙烯菊酯和氯氰菊酯在液相中的光解作用，并用离心薄层层析方法对光解混合物进行了分离。对光解产物的ＦＴＩＲ红外光谱谱图和标样的ＦＴＩＲ红外光谱谱图的研究表明，光解产物的ＦＴＩＲ红外光谱图发生了较大变化，有羟基和环氧化结构产生，即有氧化产物生成；甲醚菊酯和丙烯酯光解产物的元素分析结果与表明产物中氧的含量有明显提高、证实氧参与了拟除虫菊酯的光解过程。     

Effects of electron-beam irradiation on surface oxidation of polymer composites

The aim of this article was to show the effects of an electron radiation dose and presence of a compatibilizer on the oxidation of composites made of blends of low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), polystyrene (PS), and poly(ethylene terephthalate) (PET) as well as of blends of LDPE, HDPE, and PP. As the compatibilizers, the styrene-ethylene/butylene-styrene elastomer grafted with maleic anhydride (SEBS-g-MA) and trimethylol propane trimethylacrylate (TMPTA) were used; they were added in the amounts of 5, 10, and 15 wt% and 1, 2, and 3 wt%, respectively. The oxidation of the surface layer (SL) was investigated by the X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). It was found that the extent of the composite oxidation increased with the increasing dose of the electron radiation. The addition of the compatibilizers enhanced the oxidation of the SL but hindered the oxidation of the bulk of the material.     

聚丙烯孔洞驻极体膜的化学表面处理及电荷稳定性

利用热刺激放电(Thermally Stimulated Discharge, TSD)电流谱、在线电荷TSD、电荷等温衰减测量和衰减全反射(Attenuated Total Reflection, ATR)红外光谱分析，本文系统地研究了经化学表面处理(萃取、氧化及氢氟酸)的聚丙烯(PP)孔洞驻极体膜的电荷储存稳定性及电荷稳定性提高的原因.结果表明：经适当地氧化和氢氟酸室温处理试样的TSD电流谱中在温位约为184℃处出现原膜所没有的非常强的新峰，电荷热稳定性得到显著的提高，这一电荷热稳定性通过高温充电工艺得到进一步地改善；适当延长室温下氢氟酸处理的时间或延长氧化时间，都会使处理膜的电荷稳定性得到提高.理论分析表明在线电荷TSD测量法可给出线性升温过程中电荷重心及驻极体电荷量变化的综合信息，结合TSD电流谱和初始电荷重心位置的测量，可精确地考察线性升温过程中电荷重心的在线变化. 关键词： 聚丙烯孔洞膜 表面氧化 氢氟酸处理 电荷稳定性 在线电荷TSD     

Infrared ellipsometry study of the oxidation mechanisms of hydrogenated amorphous silicon

A detailed study of the oxidation of plasma deposited amorphous silicon (a-Si : H) using infrared phase modulated ellipsometry (IRPME) is presented. a-Si : H is found to be resistant against air oxidation confirming previous measurements. A 5–6 Å thick oxide layer at the surface of a-Si : H is observed after a few months of exposure to air. The extreme sensitivity of IRPME is emphasized. In particular Si-O-Si and (O_n)Si-H stretching vibrations are identified at the film surface at the submonolayer level. The oxidation mechanisms are discussed. The weak reactivity of a-Si : H with atmosphere is correlated with the presence of a hydrogen rich thin layer at the top surface.     

IR study on the effect of chloride ion on porous silicon

Infrared (IR) studies have been carried out on porous silicon samples to infer on the changes in the surface bonding in the porous silicon (PS) layer due to chloride (Cl⁻) and subsequent fluoride (F⁻) ion exposures with respect to time. It is observed that silicon hydride linkages decreases and silicon oxide linkages increases with time of exposure to HCl, suggesting a possible oxidation of the porous layer. IR study revealed the formation of SiO (silanones) bonds. A possible mechanism for the formation of silanones from SiOH species has been proposed to explain the observation. We also observed a saturation of silicon oxide groups with complete disappearance of silicon hydride peaks indicating the complete conversion of silicon hydride to oxides. Furthermore on exposure to F⁻, the IR spectrum showed a rapid destruction of silicon oxygen linkages.     

Thermo-oxidative degradation kinetics of grafted polypropylene films

The thermo-oxidative stability and degradation behavior of polypropylene (PP) and grafted PP have been investigated using thermogravimetric analysis. Three multiple heating rate methods, namely Kissinger, Kim–Park and Flynn–Wall have been used to calculate the activation energy as a function of the extent of degradation. The four different heating rates (5, 10, 15 and 20°C/min) were maintained in the temperature range of 30–550°C during the analysis. Fourier transform infrared spectroscopy has confirmed the presence of carboxylic group on the surface of grafted PP films. Differential scanning calorimetry has shown that the crystallinity decreased with the increase in grafting. In the air atmosphere, the thermo-oxidative degradation occurs via a pathway that involves decomposition of polymer peroxide. Thermo-oxidative stability of grafted PP films is found to increase with an increase in the degree of grafting (DG). The degradation kinetic parameters were used to predict the lifetime of PP and grafted PP films. The activation energy and lifetime of grafted PP films increased with an increase in the DG. The lifetime of PP and grafted PP decreased with an increase in degradation temperature.