界面对聚丙烯/碳酸钙复合材料光氧老化的影响

以聚丙烯(PP)/碳酸钙为研究对象,以复合材料界面为着眼点,探讨了不同的填料粒径和表面组成对复合材料光氧老化的影响,并提出了相关机理.首先,文中认为聚合物/无机填料界面面积与界面化学组成是影响老化速率的关键因素.聚合物与碳酸钙的总界面面积的增大会加速PP的光氧老化,不同偶联剂处理会改变碳酸钙的表面化学特性进而对PP老化产生促进或抑制.在此基础上提出了基于界面的老化反应速率概念及相应模型.其次,在老化领域采用了"界面放大"的实验方案,验证了碳酸钙对PP的老化促进很大程度上来源于碳酸钙表面的化学组成.此外,研究发现采用表面处理剂钛酸酯改性的碳酸钙能大大促进PP的老化,且表现为钛酸酯与碳酸钙的协同效果.     

钛酸酯偶联剂的结构对PVC/木质素复合材料性能的影响

本文采用钛酸酯系列偶联剂对造纸工业废渣──木质素磺酸盐进行处理，然后填充聚氯乙烯（PVC）制成复合材料．结果发现用钛酸酯类偶联剂处理的木质素磺酸盐，填充PVC体系，其拉伸强度随使用钛酸酯偶联剂不同，拉伸强度下降幅度不同，而冲击强度和伸长率都不同程度上升，尤以冲击强度的提高最为明显．     

聚对苯二甲酸乙二醇酯/碳酸钙纳米复合材料的制备和表征

以聚乙二醇磷酸酯1000为表面处理剂, 采用碳化法合成了方解石型碳酸钙纳米粒子, 进一步制备了聚对苯二甲酸乙二醇酯/碳酸钙纳米复合材料. 采用透射电子显微镜(TEM)、 X射线衍射(XRD)、 傅里叶变换红外光谱(FTIR), 场发射扫描电子显微镜(FESEM)和热重分析(TGA)对样品进行了分析. 结果表明, 聚乙二醇磷酸酯1000成功地修饰到碳酸钙的表面, 并得到平均直径为60 nm, 形貌为立方体的纳米碳酸钙晶体. 与碳酸钙(空白)样品相比, 表面处理碳酸钙的复合材料表现出更好的分散性和热稳定性. 采用Friedman方法计算了复合材料热分解的活化能. 聚对苯二甲酸乙二醇酯、 聚对苯二甲酸乙二醇酯/空白碳酸钙和聚对苯二甲酸乙二醇酯/表面处理碳酸钙的活化能分别为200.58, 214.86和219.50 kJ/mol, 进一步说明了表面处理碳酸钙更好地改善了聚对苯二甲酸乙二醇酯的热稳定性.     

由乙烯高效催化聚合而得的超高分子量聚乙烯的研究

本工作系研究以高效催化聚合获得的超高分子量聚乙烯的结构和性能。用扫描电子显微镜观察了高效催化剂及初生聚乙烯的形态。透射电子显微镜观察了初生聚乙烯粉未,发现毛遂边缘的超分子原纤维状织态结构。用偏光显微镜观察了不同分子量聚乙烯粉末的熔融和冷却结晶过程,生成的球晶随分子量增大而增大。用X-射线衍射、差热分析、倒换气相色谱测定了初生聚乙烯的结晶度随分子量而增大;用X-射线衍射、差热分析及密度梯度法测定经退火或热压制的聚乙烯样品的结晶度均随分子量增大而下降。X-射线衍射测定其晶粒尺寸亦随分子量增大而减小。差热分析和倒换气相色谱测定超高分子量聚乙烯粉末的结晶熔点温度(T_m)要比普通分子量聚乙烯高8-12℃。不同分子量聚乙烯的热形变曲线表明,超高分子量聚乙烯在熔融温度后出现明显的橡胶态。此外,还用差热与热重分析研究了超高分子量聚乙烯的热老化行为。测定了超高分子量聚乙烯的优异抗冲强度和沙浆磨耗量。并用扫描电镜对比观察了常规分子量和超高分子量聚乙烯试样的冲击断面的织态结构。     

聚乙烯光引发交联过程中的表面光氧化和光稳定

通过测定凝胶含量并利用红外-光声光谱和光电子能谱对光交联聚乙烯表面氧化程度和氧化产物进行了研究.结果表明,聚乙烯光交联过程中随着光照时间的增加,表面光氧化加剧,氧化产物主要是氢过氧化物和含羰基的化合物.考察了预辐照和添加受阻胺型光稳定剂对聚乙烯光交联过程的影响,发现这两种方法都能有效地降低光交联聚乙烯(XLPE)的表面氧化,但有些光稳定剂会降低XLPE的交联度.     

纳米CeO2的表面改性及其在聚丙烯中的分散性研究

选用4种不同的偶联剂以无水乙醇为溶剂对纳米氧化铈进行表面处理,测定处理好的样品分别在环己烷中的分散性.选择经不同偶联剂处理过的样品在环己烷体系中分散效果最好的比例与聚丙烯切片共混,在扫描电镜上观察共混物断面纳米CeO2的分散情况.结果表明,表面处理有利于纳米氧化铈在聚丙烯中的分散,其中以钛酸酯3#比例为8%时处理的效果最好.钛酸酯3#处理后样品的红外光谱表明,纳米CeO2与偶联剂发生了化学键合作用,它们之间并不是简单的物理包覆.     

取向、结晶、γ辐照聚对苯二甲酸乙二醇酯(PET)驻极体的陷阱性质

用拉伸、热处理和γ射线辐照的方法制备了一系列具有不同平面取向度、不同结晶度和不同分子链长度的PET试样.随平面取向度、结晶度和辐照剂量的增大,平均陷阱深度加深.由拉伸取向形成的结构陷阱俘获载流子能力随取向度增大而提高;由γ辐照形成的结构陷阱对俘获载流子的限制能力随辐照剂量增大而降低;由热结晶形成的结构陷阱俘获载流子能力在结晶度为20％时达到极值.提出了相应的三种陷阱模型.     

取向、结晶、γ辐照聚对苯二甲酸乙二醇酯(PET)驻极体的陷阱性质

 用拉伸、热处理和γ射线辐照的方法制备了一系列具有不同平面取向度、不同结晶度和不同分子链长度的PET试样.随平面取向度、结晶度和辐照剂量的增大,平均陷阱深度加深.由拉伸取向形成的结构陷阱俘获载流子能力随取向度增大而提高;由γ辐照形成的结构陷阱对俘获载流子的限制能力随辐照剂量增大而降低;由热结晶形成的结构陷阱俘获载流子能力在结晶度为20％时达到极值.提出了相应的三种陷阱模型.     

MMA接枝改性PVC/CaCO3纳米复合材料的力学性能

采用熔融共混法制备PMMA接枝改性纳米CaCO3增韧PVC（PVC/CaCO3）复合材料,并研究了复合材料的力学性能.结果表明,通过表面PMMA的接枝改性,可以显著提高纳米CaCO3增韧聚氯乙烯复合材料的拉伸强度和拉伸模量,在纳米CaCO3颗粒表面PMMA包覆层厚度为2nm时,复合材料的拉伸强度和拉伸模量达到极大值.对比于未处理纳米CaCO3和钛酸酯偶联剂处理纳米CaCO3,PMMA接枝改性纳米CaCO3增韧PVC复合材料的拉伸强度得到较大幅度提高.SEM显示,经过PMMA接枝改性后的碳酸钙在PVC基体中分散均匀,与基体界面结合良好.     

Fe负载UiO-66协同非均相类Fenton氧化降解废气苯的研究

采用水热合成法制备了不同掺杂比例Fe负载UiO-66,并借助XRD、SEM、XPS等分析测试手段对催化剂物理化学特性进行分析,通过自制非均相类Fenton体系装置探究不同Fe负载量、H_2O_2浓度、空塔速率、反应温度等条件下对废气苯的氧化降解效率影响。结果表明,不同Fe负载量的UiO-66均具有较高的结晶度,呈不规则球状;在非均相类Fenton氧化降解苯实验中,30%的Fe负载UiO-66具有最高的苯脱除效率。EPR结果显示,Fe负载量的增大促进·OH的产生,在一定程度上促进苯的氧化降解。过高的反应温度导致H_2O_2不稳定,非均相类Fenton氧化降解苯的效率随温度的升高先增大后降低。     

碳酸钙填充高密度聚乙烯复合材料冲击断口形貌的研究

用扫描电镜观察了碳酸钙（ＣａＣＯ３）／高密度聚乙烯（ＨＤＰＥ）复合材料的冲击断口形貌．发现以１２５０目轻质ＣａＣＯ３填充的ＨＤＰＥ,其断口形貌一般呈带状结构;以１２５０目重质ＣａＣＯ３或３２５目轻质ＣａＣＯ３填充的ＨＤＰＥ,其断口形貌一般呈絮状结构．带状的成因是包覆的ＣａＣＯ３粒子具有几乎各向同性地向四周传递应力的能力,满意地解释了带状的平行方向可以与宏观受力方向平行、垂直或成某种夹角,但总是与微观的某一基体屈服、变形的方向垂直．带状与絮状结构是断口形貌的两种形式,不表征冲击强度的高低     

Impact of titanate coupling agent on properties of high density polyethylene composite filled with coal gangue

In this study, surface modification of coal gangue (CG) was performed with titanate coupling agent 201 (isopropyl tri(dioctylpyrophosphate) titanate), and the effects of surface modifier on mechanical properties and thermal stability of high-density polyethylene filled with CG (HDPE/CG) and high-density polyethylene filled with modified CG (HDPE/mCG) composites were investigated. The coupling agent was successfully grafted on CG surface through chemical reaction according to the analyses of Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS), and the coupling agent can effectively enhance the hydrophobicity of surface that was verified by water contact angle beyond 90° of modified CG sample. With the introduction of coupling agent, some enhancements of tensile strength, flexural strength, and impact strength were observed in HDPE/mCG compared with HDPE/CG, due to the improved compatibility between mCG fillers and matrix. The increased storage modulus and decreased loss factor of HDPE/mCG composite further confirm the stronger interface adhesion after modification. Moreover, it is found that titanate coupling agent 201 can improve the thermal stability of HDPE/mCG composite to some extent.     

Thermal oxidation products and kinetics of polyethylene composites

The thermal oxidation behavior of high-density polyethylene (HDPE) composites was investigated at 60 °C, 90 °C and 110 °C, using Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). The inorganic fillers do not modify the thermal oxidation mechanisms of HDPE. However, they have great effects on the thermal oxidation kinetics—both the activation energy and the pre-exponential factor increase. That means that although the addition of inorganic fillers retards the onset of thermal oxidation of HDPE, once the oxidation begins, it proceeds much faster than that of HDPE. Stability evaluation of HDPE composites by TGA was not consistent with the result by FTIR. The inorganic fillers influence the oxidation products and their distribution greatly. HDPE/STC and HDPE/mica oxidations were delineated by large amount of carbonyl formation, especially esters and ketones, while HDPE/wollastonite and HDPE/diatomite showed minimum carbonyl formation. In HDPE composites, there is a good relation between the carboxylic formation and the carbonyl index.     

CaCO3/PEEK复合体系的力学行为和热行为研究

以聚醚醚酮和碳酸钙复合体系为研究对象,考察了偶联剂和填料添加量对复合材料力学行为和热行为的影响.发现磺化聚醚醚酮作为偶联剂能有效地改善材料的力学性能,提高基体树脂的玻璃化转变温度,降低基体树脂的熔点,有助于改善聚醚醚酮的加工条件     

Thermal analysis of aged hdpe based composites

HDPE based composites were produced with 10-20-30 and 40% composite mass of wood fiber. The coupling agents were epolene and silane. The thermal behavior of composite samples was analyzed as a function of the coupling agent content, the exposure time and the wood fibers content by means of differential scanning calorimetry. Calorimetric curves of all samples of first and second heating shows a similar behavior. Some significant relation has been observed between the exposure time and the degree of crystallinity for the same percentage of fiber samples. A linear relation between the melting enthalpy average vs. content in cellulosic fibers is detected. Nevertheless, the fibers non-pretreated with coupling agent show a lower loss of crystallinity of the HDPE matrix at low wood fiber content (10%). A slight diminution of the melting peak temperature is detected as increasing the exposure time. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of coupling agents on mechanical and morphological behavior of the PP/HDPE blend with two different CaCO3

The main purpose of incorporating fillers, such as calcium carbonate, into blends of polyolefins is to decrease costs and change tensile and impact properties. Structural differences between both components give rise to the formation of large filler agglomerates in the polymer matrix, which influence the mechanical response of the material. Therefore, the coupling agents of the Lica 12 type at various concentrations was used to facilitate the link between filler and matrix (the latter consisting of PP/HDPE 80/20 wt). Filler was added to the PP/HDPE blend at a 30 wt.% concentration. Two types of calcium carbonate (CaCO₃) were used. These have different average sizes (3.0 and 1.8 μm) which were determined by means of laser diffraction techniques. In addition other coupling agents of the titanate type, such as Lica 09, Lica 01, zirconates ZN 12, and a 1:1 mixture of Lica 12 and Lica 01, were used. This study clearly demonstrated that the addition of the coupling agent to CaCO₃ modifies the mechanical properties of the PP/HDPE/CaCO₃ composites. Values of the mechanical properties indicate that due to its characteristics, each coupling agent gives rise to increases in a particular mechanical property. In the case of Lica 01 an increase was verified in Young’s modulus at 0.7 wt.% and in elongation at break at both concentrations (0.3 and 0.7 wt.%), whereas ZN 12 brought about an increase in elongation at break. The 1:1 mixture of Lica 12 and Lica 01 caused impact resistance of the blend of PP/HDPE with CaCO₃ to increase considerably.     

Determination of degree of conversion as a function of depth of a photo-initiated dental restoration composite—III application to commercial Prodigy Condensable™

In this third work, we evaluated the degree of conversion (DC) versus depth of dental filling composite named Prodigy Condensable™ using infrared spectroscopy. Confirming previous results, there was a gradual reduction of DC with increasing depth but the composite exhibited extreme values of DC, an upper value (45.9%) on the surface and a lower one (6.1%) at a depth of 5 mm. The composite presented the worst performance among materials studied. The composite formulation was 80% of inorganic fillers and BisfenolA/dimethacrylate (BisGMA) (18%)/triethyleneglycoldimethacrylate (TEGDMA) (2.0%) as monomers. As stated before, type/ratio/viscosity of monomers and type, amount, size and size distribution of fillers all together had an important role in the cure reaction contributing to the final performance of the composite.     

Surface modification of highly dispersed rubber fillers and pigments by titanate proadhesive and hydrophobic compounds

A method of modifying silicate and carbonate fillers with titanate coupling agents and proadhesive agents was worked out. The modification aimed at hydrophobization of filler surface by introduction to the surface of functional groups with chemical affinity to polymers. Optimum amounts of modifying substances and appropriate conditions for performing the modification process were established. The obtained fillers showed a high degree of hydrophobicity.The modified fillers were applied in rubber mixtures based on butadienestyrene or natural rubber, in polyurethanes, in PVC, and as pigments in oil dyes of high corossive resistance.     

Infectious Behavior in Photo-oxidation of Polymers

When a polymer is used together with others,its aging process will be affected by the adjacent polymers.This infectious behavior between polymers makes the aging process more complex than that of an individual material.In this study,infectious behavior in photooxidation of polymers was investigated.Polypropylenes(PPs),an unstabilized PP and a commercial PP,were chosen as the infection sources.Six typical polymers,high density polyethylene(HDPE),low density polyethylene(LDPE),polystyrene(PS),polycarbonate(PC),poly(ethylene terephthalate)(PET),and polyamide 6(PA6),were used as the targets.The degree of oxidation of the targets was evaluated by attenuated total reflection-Fourier transform infrared spectroscopy(ATR-FTIR).An accelerating effect of two infection sources on the photo-oxidation of the target polymers was observed.Potential infectious agents from the infection sources were detected by pyrolysis-gas chromatography-mass spectrometry(Py-GC-MS)and gas chromatography(GC).The acceleration effect of two main infectious agents,i.e.acetone and acetic acid,on the photo-oxidation of the commercial PP was verified.The infectious effect of the infection source on the target polymer was considered to be a comprehensive result of the effects of a variety of infectious agents.     

石墨填充高密度聚乙烯基复合材料导热性能的研究

选用导热系数较高的无机填料石墨对高密度聚乙烯(HDPE)进行填充改性;采用偶联剂和磨盘型力化学反应器对石墨进行表面处理,提高石墨与聚合物基体的界面相互作用;用自行研制的升温速率测定装置测试材料的导热性能,并研究材料的导热机理;用SEM观察复合材料的微观形态.实验结果表明:经偶联剂处理后,石墨在HDPE中均匀分布;测试试样的上表面温度随时间的变化可用三次多项式T=A₀+A₁t+A₂t²+A₃t³拟会;HDPE/石墨复合材料升温速率随石墨含量增加而增大;石墨含量为35％的复合材料最大升温速率为HDPE的1.75倍.