FTIR研究聚氨酯包膜尿素的溶胀度与控释机理

采用傅里叶变换红外光谱(FTIR)分析了聚氨酯包膜控释尿素(PCU)养分溶出过程膜层的结构变化。对比发现,随着溶出时间的延长,膜层的结构产生明显的改变,当养分累积释放量达到50%,膜层的红外谱图在3 435,3 342,1 671,1 621,1 448,1 159cm-1出现了新的吸收峰,与尿素的特征吸收峰3 440,3 347,1 667,1 624,1 460,1 154cm-1吻合,当养分累积释放量达到70%,新出现吸收峰的强度继续增加,此时膜层的红外谱图新增的吸收峰与尿素的红外谱图有较高的相似度。结果表明,新吸收峰的出现及增强是由于尿素在膜层连续相中含量增加引起的,含量越高表明膜层溶胀度越大,此时膜层微孔尺寸发生变化,导致养分释放速率的改变,养分释放曲线呈"S"形状。     

红外光谱分析醋酸酯淀粉包膜尿素膜降解特征

采用傅里叶变换红外吸收光谱(FTIR)方法分析醋酸酯淀粉包膜尿素及与生化抑制剂结合的四种肥料在棕壤中膜降解特征,为包膜尿素肥料的应用提供科学依据。分析表明,膜化学成分,分子结构和膜组成没有因加入不同的抑制剂而改变。膜特征峰主要是H-O,—OH,CO2,C=O,—CH2,—CH3,C—O,C—O—H,C—O—C的不对称、对称伸缩振动吸收。在棕壤中,最高峰吸收强度总趋势0>15>30>60>90>120>150>310d,前15d降解相对缓慢。150d大部分膜物质已降解。经过310d,膜主要官能团或分子结构发生了实质性改变,不同抑制剂对膜降解速度没有显著影响。红外吸收光谱完全可以测定与描述醋酸酯淀粉膜降解特征,并可揭示膜降解速度差异。     

红外光谱分析丙烯酸树脂包膜尿素膜降解特征

采用傅里叶变换红外光谱吸收(FTIR)方法分析丙烯酸树脂包膜尿素及与生化抑制剂结合的四种肥料在棕壤中膜降解特征,尝试利用红外光谱技术分析丙烯酸树脂膜降解特征,为包膜尿素肥料的应用提供科学依据。分析表明,成膜的化学成分,分子结构和膜组成没有因不同种生化抑制剂的加入而受到影响。膜特征峰出现在3 479～3 195,2 993～2 873,1 741～1 564,1 461～925和850～650cm-1之间,主要是CH3,CH2的—C—H,—OH,C—O,C—C,C—O—C,CO,CC的不对称、对称伸缩振动吸收,峰面随时间变化由平到尖,由宽到窄,吸收强度因化学键量变强弱不一。60d前四种肥料膜红外吸收光谱没有明显区别,膜降解缓慢;而60d后降解速度加快,以120d降解速度最快,310d后四种肥料膜主要分子结构没有实质性改变,膜材料主要成分在棕壤中降解十分缓慢,降解速度并没有明显受到不同生化抑制剂的影响。降解特征可以用红外吸收光谱测定与描述,红外光谱能够描绘膜降解动态,物质化学基团变化,降解速度的差别。     

红外吸收光谱快速评估脲甲醛肥效的可行性

目前国内外对脲甲醛肥料肥效的快速评价方法均采用基于脲甲醛水溶性的活度系数法,但不同国家和地区具体的操作规程和技术指标不尽相同,究其原因在于活度系数法的局限性。脲甲醛肥料的养分释放速率与脲甲醛结构有直接的关系,与其在不同温度水溶液中的溶解性没有直接关联,因此从脲甲醛结构入手研究其养分释放更为合理。通过考察傅里叶变换红外光谱评估不同水分、尿素量和甲醛存放时间三个因素下尿素与甲醛产物结构的可行性,以寻求一种新的脲甲醛肥效评价方法。研究了不同反应条件下产物红外吸收光谱图、产物生成量和酸性环境下不同尿素加入量反应产物养分释放间的关系。谱图能够反映出反应过程中不同的水分和尿素加入量及甲醛存放时间对特征基团吸收峰相对强弱产生的细微变化,通过这些变化可以判断脲甲醛组成变化。这些判断能够从产物的量得到印证,同时土培试验的结果也进一步证实通过红外谱图判断的正确性。以上研究结果表明用红外吸收光谱研究脲甲醛结构的细微变化是可行的,如果将脲甲醛红外光谱的细微变化与其在土壤中养分释放情况间建立起相应的数学模型,将为脲甲醛肥料肥效准确、快速评估提供一个新的手段。     

基于中红外光谱检测牛奶中掺杂的尿素

采用中红外光谱技术对牛奶中掺杂尿素目标物进行检测.配置含有尿素浓度范围为1～18 g·L-1之间18个牛奶样品,分别研究了纯牛奶和掺杂尿素牛奶的红外光谱特性,并进行了对比分析.利用尿素1 562 cm-1处酰胺Ⅲ带C=O伸缩振动吸收峰面积A1 562与1 464 cm-1处C-N伸缩振动吸收峰面积A1464的比值A1 ...     

1,1,3,3-四甲基脲—溶剂氢键复合物的理论研究

采用密度泛函理论在B3LYP/6-311++G(d,p)水平上对水、苯胺、氯仿与1,1,3,3-四甲基脲分子形成的1:1气相氢键复合物进行计算研究.结果表明,三种物质与1,1,3,3-四甲基脲形成的复合物存在氢键,表现为羰基氧原子的孤对电子与H—X(X=O,N,C)反键轨道的相互作用.氢键的形成使C=O和H—X的伸缩振动频率红移.在标准压力和298.15 K下,氢键复合物的形成是一个放热的非自发过程.     

柠檬酸和乙二胺改性前后麦秸秆的红外光谱分析比较

对天然麦秸秆(NWS)、柠檬酸改性麦秸秆(CWS)、乙二胺改性麦秸秆(EWS)的红外光谱进行了比较分析.NWS的红外吸收光谱主要由碳水化合物如木质素、纤维素等吸收带组成.NWS表面的羟基吸收峰出现在3405.16cm-1、2916.81cm-1处的吸收峰来自亚甲基中C—H的伸缩振动.1736.02cm-1和1602.21cm-1处的吸收峰是由C=O的伸缩振动引起的;苯环的骨架伸缩振动峰出现在1511.33cm-1;1425.47cm-1处的吸收峰是来自羧基的C—O伸缩振动,1376.19cm-1处为CH2的弯曲振动峰.与NWS的红外光谱图相比,CWS的主要变化为1738.13cm-1和1592.06cm-1处C=O吸收峰强度显著增加;EWS的主要变化为3405.16cm-1处的吸收峰蓝移至3417.43cm-1,且强度增加,1736.02cm-1处的吸收峰消失,CH2的C—H伸缩振动峰(2903.49cm-1)和弯曲振动峰(1382.91cm-1)强度显著增加,结果说明改性后分别引入了羧基和胺基.     

FTIR研究热处理对RIM PUU的形态及力学性能的影响

将PUU(聚氨酯脲)样品薄膜放入FTIR恒温池内进行原位扫描。FTIR红外谱图的结果表明,在一定温度下,随着热处理时间的延长,氢键化的脲键的吸收逐渐增加,达到一定时间后,吸收变化甚微。在热处理过程中,有序氢键化脲键基团吸收的变化率(反映微相分离动力学)随着温度的提高而增加。PUU材料在热处理之前,羰基振动区内游离的氨酯键、无序氢键化的氨酯键、有序氢键化氨酯键、无序的氢键化脲键和有序的氢键化脲键等多种羰基并存,热处理后仅存游离的氨酯键、氢键化的氨酯键及有序的脲键3种吸收谱带。在100℃下,热处理时间(超过8h)越长,力学性能越差。而在相同的热处理时间(8h)内,热处理温度在100℃,PUU弹性体具有较好的综合力学性能。     

PPC地膜不同覆盖方式下降解特征的红外光谱分析

为解决可降解地膜因降解而发生过早的破裂，研究不同覆盖方式下PPC地膜的稳定性及降解情况。设置了6种田间覆盖方式：单层黑色PPC地膜(SB);单层白色PPC地膜(SW);双层黑色PPC地膜(DB);双层白色PPC地膜(DW);上黑色下白色双层PPC地膜(DBW);上白色下黑色双层PPC地膜(DWB),测定了不同时间段地膜的红外光谱特征、力学性能和分子量，对不同处理下地膜的降解情况做出判断。结果表明，地膜长时间暴露在自然条件下，地膜的韧性变差，分子结构中的主链发生断裂，进而C—H键和C—O键的吸收峰相对强度随时间延长发生下降；由于地膜在水分子和微生物的作用下发生降解进而导致■伸缩振动峰和C—O—C反对称吸收峰相对强度出现不同程度的上升。双层地膜因经阳光照射下分子链活跃出现粘连的现象，稳定性明显高于单层地膜，因此双层地膜DWB和DBW处理的官能团吸收峰强度较单层地膜稳定，降解程度相对更缓慢。各处理的分子量和力学性能都呈现下降的趋势，双层地膜处理的分子量、伸拉力强度和断裂伸长率显著高于单层地膜，其中黑白双层地膜DWB处理和DBW处理在30～150 d内的稳定性强于单层地膜，到150 d时，DW...     

三种膜材喷涂尿素前后红外吸收的研究

包膜肥料是目前肥料研究领域中的热点。相关的研究主要集中在包膜材料对包膜肥养分释放的作用机制上,而膜材在包膜前后结构变化的可用信息则较少,此信息是能否直接用膜材研究包膜肥养分控释机理的关键所在。文章分别用以聚乳酸(PLA)、聚丁二酸丁二醇酯(PBS)和聚碳酸酯(PC)为主要材料配制的膜材为对象,研究他们在对尿素包膜前后红外吸收光谱的变化,目的是为利用纯膜材深入研究包膜肥养分控释机理提供理论依据。结果显示PLA和PC在对尿素包膜前后的红外吸收光谱变化较小,而PBS较大。这说明前两种包膜材料能够直接用于研究包膜肥养分释放情况,但PBS不能。     

Structure Development and Interfacial Interactions in Flexible Polyurethane Foam-Layered Silicate Nanocomposites

Unmodified Na-montmorillonite (MMT) was swollen in a polyol/water mixture using an ultrasound technique. Polyurethane (PU) foam nanocomposites were formed via reaction of these polyol/water/Na-MMT mixtures with toluene diisocyanate (TDI). Forced-adiabatic attenuated total reflectance FTIR spectroscopy was used to determine the kinetics of both the PU copolymerisation and of the microphase separation between poly(ether-urethane) soft segments and polyurea hard segments. Consumption of TDI during the initial stages of the copolymerisation was accelerated significantly by the addition of ≤10 wt% Na-MMT. The initial rate of formation of urea groups also increased significantly upon addition of Na-MMT, but at reaction times >100 s a significant retardation occurred in the development of hydrogen bonding within the urea groups of the hard-segment phase that was recovered only after 1000 s. The reasons for this extensive disruption in structure development were investigated using flow microcalorimetry (FMC), diffuse reflectance Fourier-transform infrared spectroscopy (DRIFTS), and wide angle X-ray scattering (WAXS) to monitor the adsorption process and any chemical reaction between hydrated Na-MMT and a model monoisocyanate; 4-ethylphenyl isocyanate (4-EPI). DRIFTS spectra of 4-EPI adsorbed on Na-MMT revealed urea groups, indicating formation of N,N′-bis(4-ethylphenyl) urea. FMC indicated that a significant quantity of this urea formed at the surface and then desorbed. In addition, DRIFTS spectra indicated that the 4-EPI reacted with hydroxyl groups present at the edges of the silicate platelets to form urethane linkages. Thus, in a PU-foam reaction mixture, the water will tend to associate with the Na-MMT, either within the galleries or on the surfaces of silicate lamellae. Upon reaction with isocyanate, the presence of the Na-MMT both promotes the formation of urea and generates urethane linkages between silicate lamellae and the polyurethane.     

Investigating the interfacial interaction of different aminosilane treated nano silicas with a polyurethane coating

In this work different nano silica particles varying in aminosilane functionalities were dispersed into a polyurethane clear coating (PU). The optical clarity of the resulting films as well as the mechanical integrities were studied utilizing haze transmission and dynamic mechanical analysis respectively. In addition, the curing behavior of films was investigated using differential scanning calorimetry. It was found that particle dispersibility directly depended on the amount of grafted silane at the surface of nano silicas. Also the presence of amine functional groups on silica particles resulted in a systematic improvement of Tg and therefore in enhanced mechanical performance. These were attributed to an increased interfacial interaction and formation of some urea linkages in the hard segment of the polyurethane matrix. The DSC analyses also showed that the heat of reaction of particle loaded samples were all lower than that of the blank PU due to the facilitated interaction of amino groups at the silica surface with isocyanate cross-linker.     

Fabrication and Morphological Characterization of Polyurethane Foam Reinforced with TiO2 Nanoparticles

Polyurethane foams with various isocyanate/polyol ratios, reinforced with various amounts of nanosized TiO₂, were prepared and their morphological properties were investigated. The nanoparticles were dispersed into the polyol component by stirring and then heating during ultrasonication to avoid particle agglomeration. Both scanning electron and transmission optical microscopes were used to evaluate the role of the nanosized TiO₂ on the porous structure of the polyurethane foams. Cell size distributions were obtained by measuring the average cell diameters of the cells in the micrographs. To have a better assessment of nanoparticle effects on the foam morphology sample densities were measured using Archimedes law. For better understanding of microstructure evolution the heat release rate during the foaming process was characterized. The results showed that the values of cell size, cell density, apparent density and heat release rate depended on the ratio of isocyanate/polyol as well as TiO₂ content.     

Influence of thermal annealing on bonding structure and dielectric properties of fluorinated amorphous carbon film

The bond structure and dielectric properties of fluorinated carbon films after thermal annealing in N₂ ambience were studied. The results show that dielectric constant and dielectric loss increased, and optical gap decreased with increasing annealing temperature. The composition and bonding structure of the films were obtained by FTIR and XPS analysis. The data indicate that fluorine-to carbon ratio decreased and CC group increased in the films after the films were annealed. It suggests that the structural and dielectric property changes correlate with the release of fluorine and increase of cross-linking during the annealing.     

Preparation and Properties of 2, 4-2-Isocyanic Acid Methyl Ester/Poly(ϵ-caprolactone)/Diethylene Glycol Hydrogels

The hydrophilic polyurethane (PU) hydrogels have become attractive in the biomedical field for drug delivery. In this work 2, 4-2-isocyanic acid methyl ester (TDI), poly(?-caprolactone) (PCL), and poly(ethylene glycol) (PEG) were used to prepare a prepolymer and then diethylene glycol (DEG) was used as a chain extender to prepare a novel hydrophilic polyurethane, TDI/PCL-PEG/DEG. The obtained PU hydrogels were characterized by Fourier transform infrared (FT-IR) spectroscopy and scanning electronic microscopy (SEM). By varying the ratio of PCL to PEG in the copolymer, modulations of hydrophilicity and drug release behavior were observed. FT-IR analysis confirmed the successful synthesis of the TDI/PCL-PEG/DEG hydrogels. The introduction of PEG into the PU hydrogels led to a porous structure. The water contact angle and swelling ratio results confirmed that the hydrophilicity increased with increasing amounts of the PEG segments. The introduction of PEG also increased the release rate of chloramphenicol, used as model drug, from the PU hydrogels.     

腐植酸增值尿素的多谱学分子结构表征

尿素生产过程中加入腐植酸生产腐植酸增值尿素,可以有效延缓尿素水解,提高作物产量与氮肥利用效率,然而在此过程中腐植酸(HA)与尿素(U)主要发生什么反应还未见报道。利用风化煤源HA生产含腐植酸5%, 10%及20%的腐植酸增值尿素(HAU5, HAU10及HAU20),采集并分析了HAU5, HAU10, HAU20及U的红外谱图及其二阶导数谱图,用XPS与O(1s)NEXAFS分别对HAU20, HA及U进行表征;通过无水乙醇溶解HAU20的方式去除了HAU20中的尿素,并利用FTIR与XPS对醇不溶物(UHA)进行表征。结果表明：(1)FTIR原谱图及二阶导数谱图表明,腐植酸增值尿素伯胺C—N振动强度低于普通尿素,且振动强度随着HA添加量的提高而降低,XPS N(1s)与O(1s)NEXAFS检测到HAU20中分别存在较多仲胺氮与非羰基氧,且FTIR发现UHA酰胺特征明显,表明腐植酸增值尿素制备过程中HA与U发生了反应。(2)XPS C(1s)表明,HAU20与UHA羧基碳比例少于HA, FTIR结果表明,UHA中不存在HA中检测到的羧酸C—O—H面内弯曲振动,羧基CO伸缩振动位置发...     

硅氧烷改性水性聚氨酯的制备及性能

用聚氧化丙烯二醇、聚醚接枝聚硅氧烷、甲苯二异氰酸酯、二羟甲基丙酸和1,4丁二醇进行聚合,并通过三乙胺直接水乳化法合成了一种新型硅氧烷改性的透明且稳定性好的水性聚氨酯乳液.用Fourier变换红外光谱、化学分析电子能谱、接触角仪、电子拉力试验机以及乳液稳定性测试对其进行研究,测试表明乳液稳定性好,聚硅氧烷链段已被化学键入聚氨酯分子链中,硅氧烷在乳胶膜表明富集,对聚氨酯材料有明显的表面改性作用.研究结果还表明,经少量硅氧烷改性的聚氨酯材料本体的力学性质变化不大,仍然是一种很好的弹性体.随着硅氧烷含量的增加,抗张强度提高,但断裂伸长率有所减小.     

快重离子辐照C60薄膜的强电子激发效应研究

利用能量为2.0GeV的¹³⁶Xe和2.7GeV的²³⁸U离子对C₆₀薄膜进行了辐照,并用傅立叶变换红外光谱、X射线衍射谱和拉曼散射技术分析了辐照过的C₆₀样品,在傅立叶变换红外光谱上,首次观察到一个位于670cm^－1处的,表征未知结构的新峰,研究了其强度随电子能损和辐照剂量的变化规律.分析结果表明,电子能量转移主导了C₆₀薄膜的损伤过程;而损伤的部分恢复是由强电子激发的退火效应引起的;另外,离子的速度在损伤的建立过程中也起了一定的作用     

梯度固化聚氨酯脲中氢键的红外光谱分析

聚氨酯脲弹性体中的氢键可以反映其内部的微相分离状态,并对材料的宏观性能有着比较重要的影响。 通过梯度固化的方法制得了微相分离程度沿厚度方向梯度渐变的聚氨酯脲弹性体。 利用傅里叶变换红外光谱(FTIR)研究了梯度聚氨酯脲弹性体中的氢键,分析了羰基、亚氨基以及醚氧键的氢键,对弹性体的微相分离程度进行了表征。 结果表明,羰基区的氢键化程度随固化温度的升高而升高,表明微相分离程度的逐渐升高。 醚氧键氢键化程度随固化温度改变有差异,亚氨基的氢键化程度在交联较低的试样中随固化温度的升高而升高,在交联程度较高的试样中则相反。 脲羰基形成的三维氢键的强度比醚氧键形成的氢键强。 氢键化醚氧键的振动吸收大约位于1 076 cm-1。