反式-1,4-聚异戊二烯的结晶性

采用差示扫描量热仪、傅里叶变换红外光谱、偏光显微镜和X射线衍射仪等研究了反式-1,4-聚异戊二烯(TPI)的结晶性。结果表明,在TPI的差示扫描量热分析中,随着升温速率提高,第1次升温曲线上的β晶型熔融温度移向高温;而第2次升温曲线上的α晶型结晶熔融峰逐渐消失,且与第1次升温时相比β晶型的熔融温度偏高;而随着降温速率的提高,TPI的结晶峰向低温方向位移。用不同方法制备的TPI薄膜可以得到球晶、碎晶和捆束状晶体。与浇铸薄膜相比,热压薄膜傅里叶变换红外光谱曲线上的843 cm-1和980 cm-1两侧各出现了2个肩峰,而890 cm-1处的结晶峰消失。拉伸后在TPI的X射线衍射谱线上,0.47 nm和0.39 nm晶面间距的所属峰形比拉伸前要尖锐得多,而0.33 nm晶面间距所属峰则弱化。     

红外光谱法研究反式1，4-聚异戊二烯结晶特性

采用傅里叶转换红外光谱(FTIR)法研究合成反式1,4-聚异戊二烯(TPI)的结晶特性.结果表明,TPI红外吸收频率和吸收峰形不受门尼粘度的影响,门尼粘度[ML(3+4) 100℃]为30的TPI结晶含量大于门尼粘度为65和84的试样;与浇注薄膜相比,热压薄膜FTIR曲线上843和980 cm-1两侧各出现了两个肩峰,而890 cm-1处结晶峰消失;热压薄膜试样在45℃冷却后,其FTIR曲线上出现863 cm-1处的弱α晶体吸收峰,而0℃冷却试样未出现;拉伸后的TPI试样FTIR曲线在863 cm-1处出现了结晶吸收峰.     

N,N′-二-(2-吡啶基)苝四羧酸二酰亚胺的合成及性能研究

合成了N,N′ 二 (2 吡啶基)四羧酸二酰亚胺,并纯化、调晶.对产物进行了元素分析和IR光谱研究(环状二酰亚胺的CO以双峰1708.8cm-1、1664 5cm-1).α晶型产物溶液的紫外可见光谱(最大吸收波长为526.00nm)和荧光光谱(最大发射波长为538.0nm)存在很好的镜像对称关系.薄膜紫外可见光谱图在450—570nm范围内,α晶型比β晶型有较强的吸收峰.X粉末衍射也反映出α晶型在2θ为25.5°、26.3°上的衍射峰强度分别为1954、2603.α、β晶型分别作为电荷产生材料制得的功能分离型有机光导体,在光源波长λ=532nm曝光下,测得含α的感光体达到饱和电位的时间45s、半衰曝光量5.7μJ/cm2、残余电位22V等数据.测得含β的感光体达到饱和电位的时间49s、半衰曝光量9.9μJ/cm2、残余电位22V等性能数值.     

溶胶-凝胶法制备W型钡铁氧体及结构分析

以硝酸钡、硝酸钴、硝酸铁、硝酸镧和柠檬酸为原料,采用溶胶-凝胶法合成了W型钡铁氧体BaCo2Fe16O27和Ba 1-xLaxCo2Fe16O27.通过热重/同步差热分析(TG/SDTA)、X射线衍射分析(XRD)和红外光谱分析(IR)对产物进行了表征,研究了焙烧温度和稀土元素镧的掺杂对晶体结构的影响.结果表明:在制备BaCo2Fe16O27时,当焙烧温度达到1 250 ℃时,产物中不再含有M型钡铁氧体BaFe12O19和CoFe2O4,产物为单一的六方晶系BaCo2Fe16O27铁氧体.在稀土元素镧掺杂实验中,由于镧的加入,产物的红外光谱图在500 cm-1和475 cm-1附近产生新的吸收峰,分析表明分别为Fe2+-O,La-O的吸收峰.另外,稀土元素镧的掺杂对晶胞参数也有一定影响.     

用傅里叶变换拉曼光谱定量分析HNIW的γ和ε晶型混合物

建立了以傅里叶变换拉曼光谱定量分析ε-HNIW中γ-晶体含量的新方法。通过分析(α,β,γ,ε)-HNIW的傅里叶变换拉曼光谱图,以300~270cm-1区域的吸收峰作为ε-HNIW晶型纯度检测的定量依据,配制一系列不同配比的γ-HNIW与ε-HNIW混合物,经拉曼光谱分析后绘制工作曲线。结果表明,在285.30cm-1处,γ-HNIW的浓度与γ-HNIW和ε-HNIW相对峰高成直线关系,相关系数R为0.9986,标准偏差SD为7.45×10-3,线性关系良好,可用于定量分析ε-HNIW中的γ-晶型的含量。该方法操作简单,快速准确。     

反式-1,4-聚异戊二烯的结晶性对丁苯橡胶/反式-1,4-聚异戊二烯共混硫化胶拉伸性能的影响

用X射线衍射仪分析了反式-1,4-聚异戊二烯(TPI)的拉伸结晶性能,研究了其对丁苯橡胶(SBR)/TPI共混硫化胶拉伸性能的影响。结果表明,TPI具有明显的拉伸诱导结晶特性。未填充炭黑的SBR/TPI共混硫化胶及TPI硫化胶的结晶衍射峰强度从大到小依次为预拉伸试样、拉断试样和原始试样,并且TPI用量越多相应试样的结晶衍射峰强度越大;炭黑填充SBR/TPI共混硫化胶的结晶度比相应的未填充试样低得多。炭黑填充SBR/TPI共混硫化胶的拉伸强度比未填充胶料明显提高,硬度随TPI用量增加而提高的幅度低于未填充者;未填充胶料的扯断伸长率先降低后升高,而填充胶料整体上呈现下降的趋势;未填充及填充胶料的100%定伸应力都随着TPI用量的增加而升高;炭黑填充胶料在50 mm/min拉伸速率下的拉伸强度比500 mm/min拉伸速率下测得结果的增长幅度以及预拉伸试样比原始试样拉伸强度的增长幅度都小于未填充胶料。     

XT-β晶型成核剂在PP中的应用

研究了XT-β晶型系列成核剂用于聚丙烯(PP)的改性,对试样的结晶性能、力学性能等进行了分析,评价了XT-β晶型成核剂的实际应用效果。结果表明：在PP中引入XT-β晶型成核剂后,试样的球晶尺寸明显减小,广角X射线衍射谱图出现了典型的口晶型特征衍射峰;试样的结晶速率、结晶温度明显提高,差示扫描量热法谱图出现a晶型、β晶型2个熔融峰,β晶型含量达到总结晶量的50％-80％;XT-β型成核剂可使体系保持较好的力学性能,PP负荷下热变形温度提高15～40℃。     

酸改性膨润土负载ZnCl2催化松节油直接异构-歧化反应研究

以自制酸改性膨润土负载ZnCl2为催化剂,采用傅里叶红外光谱( FT-IR) 和气相色谱-质谱联用(GC-MS)技术对松节油直接催化异构-歧化液相反应进行研究.FT-IR 分析表明,在反应产物谱图中蒎烯吸收峰3023 cm-1、1653 cm-1和3067 cm-1消失,苯环的骨架吸收峰1645 cm-1 和1456 ...     

投影光源反射器用LAS微晶玻璃的研制

以TiO2和ZrO2为晶核剂,采用两步法热处理制度,制备了适合电光源反射器用的LAS系微晶玻璃。运用X射线衍射分析、扫描电子显微镜以及激光拉曼散射,结合LAS微晶玻璃的热膨胀性能和力学性能,对不同热处理制度的试样进行结构和性能研究,结果表明:随着晶化温度的升高,微晶玻璃的主晶相未发生改变,都为β-锂辉石,但晶体含量不断升高,晶粒尺寸逐渐变大。随着晶化温度的升高,~493 cm-1的拉曼峰不断变窄,强度不断增大,~154 cm-1和~162cm-1的TiO2结构振动峰不断变宽,强度不断降低,表明β-锂辉石晶体含量不断增大,微晶玻璃析晶不断增强。     

聚α-烯烃航空润滑基础油热衰变产物结构分析

利用FTIR、HPLC技术分析了聚α-烯烃航空润滑基础油(PAO)及其高温实验产物。FTIR分析发现,966 cm-1和888 cm-1附近的不饱和烯烃吸收峰表现出增强的趋势;HPLC分析显示,反应产物在240 nm波长下检测出的峰基本集中在7~9 min范围内,170 oC温度下开始出现断链或脱氢反应,300 oC试验温度下检测到的峰强度增加,说明体系中某些特定组分的含量急剧增加。这些信息对考察在用润滑油中化合物的结构与性能变化具有重要意义。     

Transcrystalline formation and properties of polypropylene on the surface of ramie fiber as induced by shear or dopamine modification

The key for fiber reinforced polymer composites is the interfacial interaction between fiber and polymer matrix. The crystallization of polymer on the surface of fiber as a possible way to enhance the interfacial interaction has received increasingly attention. In this work, the transcrystalline (TC) formation and properties of isotactic polypropylene (iPP) on ramie fiber surface, as induced either by fiber pulling or by dopamine modification, were investigated and compared. It was found that the growth rate of shear induced TC is faster than that obtained via dopamine modification. There exists α–β crystal form transition in the TC formation process as induced by pulling while only α-crystal form is obtained via dopamine modification. By using both dopamine modification and fiber pulling, a formation of TC with two step growth was observed for the first time: the first step growth has much enhanced rate than that induced by fiber pulling, and second step growth has the same rate with that induced by dopamine modification. Thus a unique TC structure was obtained, with α-crystal form presented in the inner layer and the outer layer, and β-crystal form in between. The result from single fiber fragmentation test indicated that interfacial shear stress (IFSS) between iPP and ramie fiber for dopamine modification induced TC is much higher than that of shear induced TC. Our work provides guidance for the preparation of polymer/fiber composites with enhanced interfacial interaction via formation of TC layer by using shear or fiber surface modification.     

Effect of nano-CaCO3 on polymorphic behavior in syndiotactic polystyrene for non-isothermal crystallization

Syndiotactic polystyrene (sPS)/nano-CaCO₃ composites were prepared on a twin screw extruder for the first time. Differential scanning calorimeter and wide-angle X-ray diffraction were used to investigate the effect of maximum melting temperature (T_max) and the content of nano-CaCO₃ on the crystal forms and melting behavior of sPS for non-isothermal crystallization. The results indicated that the increasing T_max decreases the crystallization temperature of sPS and facilitates the formation of β-crystal. The addition of nano-CaCO₃ changes the melting behavior and crystal form of melt-crystallized sPS and facilitates the formation of β-crystal. The increase in the content of nano-CaCO₃ decreases crystallization temperature of sPS and increases the content of β-crystal, which was similar to the effect of increasing T_max. Pure β-crystal in sPS/nano-CaCO₃ composites can be obtained at lower melting temperature due to the effect of nano-CaCO₃.     

填料对PP结晶行为的影响

用差示扫描量热法(DSC)和偏光显微镜研究了聚丙烯(PP)/无机填料复合体系的非等温结晶过程以及填料含量、尺寸、形状、偶联处理对PP结晶行为的影响。结果表明:玻璃微珠的含量增加引起结晶度降低,但不会影响球晶尺寸;小尺寸的玻璃微珠能使球晶尺寸更均匀;对玻璃微珠进行偶联处理能提高材料的结晶度;同时发现,纳米碳酸钙引发了聚丙烯由α晶型向β晶型的转变。     

TPI及SBR/TPI并用胶结晶特性的研究

使用差示扫描量热仪(DSC)研究了纯TPI粉末与SBR/TPI并用胶的结晶特性。结果表明,TPI粉末的第1次升温曲线上,β晶体的熔融温度随升温速率的增大逐渐提高,α晶体熔融峰高于β晶体;消除热历史后,β晶体熔融峰高于α晶体,且α晶体随着升温速率的提高逐渐消失;与第1次测试结果相比,第2次升温测得的结晶度呈下降趋势。冷冻作用能够稍微增大未填充SBR/TPI并用胶的结晶度。升温速率对未填充SBR/TPI并用胶晶体熔融峰的峰形分辨率有较大影响。随着TPI用量的增大,未填充并用胶及其硫化胶的结晶熔融焓均增大。填充炭黑后,SBR/TPI并用胶及其硫化胶都比未填充时的峰形钝化变宽。     

反式-1,4-聚异戊二烯的结晶性对丁苯橡胶/反式-1,4-聚异戊二烯共混硫化胶动态力学性能的影响

用动态力学分析仪和差示扫描量热仪研究了丁苯橡胶(SBR)/反式-1,4-聚异戊二烯(TPI)共混硫化胶的动态力学性能和结晶性能。结果表明,SBR与TPI的两相相容性良好。随着TPI用量的增加,SBR/TPI共混硫化胶的玻璃化转变温度向低温方向移动,且损耗因子峰值逐渐降低。用炭黑填充CV体系硫化SBR/TPI共混胶的损耗因子峰值低于相应的未填充胶料;而当TPI晶体熔融后,炭黑填充胶料的损耗因子要大于未填充者。不同硫化体系硫化SBR/TPI共混胶的损耗因子峰值和玻璃化转变温度从大到小的变化依次为CV体系、EV体系和DCP体系。     

长支链聚丙烯诱导β晶成核效应

利用乙烯基聚二甲基硅氧烷/苯乙烯接枝型长支链聚丙烯(PP-g-VS/St)在剪切和快速降温过程中可以诱导形成β晶聚丙烯这一优势,研究了PP-g-VS/St在注塑加工过程中作为高分子β晶成核剂对等规聚丙烯(iPP)结晶温度、晶体结构及力学性能的影响。结果表明改性聚丙烯的结晶温度、β晶相对含量和力学性能随着PP-g-VS/St添加量的增加而增加。当PP-g-VS/St的添加量为50%(质量分数)时,改性聚丙烯的结晶温度相对于纯iPP提高约10℃,β晶相对含量达32.8%,冲击强度、弯曲模量和拉伸强度分别相对于纯iPP提高了355.3%、53.8%和15.9%。这些结果为聚丙烯高分子β晶型成核剂的设计提供了新思路。     

β成核剂对聚丙烯管材性能影响的研究

研究了β晶型成核剂及其用量对聚丙烯管材力学性能的影响,并对其进行了正交偏光显微镜观察以及DSC分析。研究表明:加入β成核剂后,聚丙烯晶型由α转变为β,韧性大大增强,且用量在0.1%时达到最大值。     

Elevation of flow temperature of poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactic acid) gel by controlling its morphology and crystal form

Complex crystals (ε-crystals) of poly(l-lactic acid) (PLLA) with solvents such as N,N-dimethylformamide (DMF) induce gelation of PLLA by forming fibrous structure. Three procedures to elevate the flow temperature of the PLLA gel were described: formation of an additional network by immersion of a DMF solution of PLLA with lower molecular weight, changing the crystal form from ε-crystal to α-crystal by heating the gel at 46 °C, and increasing the concentration of the solution to form the gel followed by heating. Field emission electron microscopy and X-ray diffraction measurements were carried out to elucidate the structural change and driving force of the elevation of the flow temperature. Densification of the fibrous structure and change of the crystal form from ε-crystals to α-crystals with lower solubility at higher temperatures were observed in the gel after the formation of an additional network by immersion in a DMF solution of PLLA. The procedure to elevate the flow temperature, which has been developed in this study, can broaden the application of PLLA gels.     

Effect of β-nucleating agent and zeolite molecular sieves on supercritical CO2-assisted cell and crystal nucleation during the long-chain-branched polypropylene foaming

It is of great interest and importance to design and fabricate the double crystal melting peak (DCMP) structure for the expanded polypropylene (EPP) bead foams during sintering. Two kinds of methods with different mechanisms were proposed to prepare long-chain-branched polypropylene (LCBPP) samples with a DCMP structure: One was that the DCMP structure was prepared by generating crystals of different perfection degrees and the other one was that the DCMP structure was prepared by adding β-NA to produce various crystal forms. In addition, zeolite molecular sieve (ZMS) as the synergist was introduced into LCBPP/β-NA system to increase the efficiency of β-NA. The crystallization behaviors of various PP and their foams were tested by differential scanning calorimetry and wide-angle X-ray diffraction, as well as the cellular morphologies of various LCBPP foams were observed by scanning electron microscope. The results showed that a DCMP structure was formed in pure LCBPP in the presence of CO₂ at 168–172 °C. The content of β-crystal in LCBPP/β-NA system was the highest when the content of β-NA optimized as 1.5 phr. The percentage of β-crystal in LCBPP/β-NA system was further increased when a small content (0.045 phr) of ZMS was added. Compared with that in unfoamed LCBPP, the percentage of β-crystal in LCBPP foams was obviously enhanced, due to the coupling effect of crystal nucleation and cell nucleation. In the LCBPP foams, the cell size became smaller and the cell density became larger, owing to the addition of ZMS. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48183.