尼龙6改性超高分子量聚乙烯

采用挤出成型工艺制备了尼龙6(PA6)改性超高分子量聚乙烯(PE–UHMW)共混材料。研究了PA6含量对PE–UHMW/PA6共混材料热性能及力学性能的影响。研究表明,PA6质量分数为30%时维卡软化温度达到145.9℃,较纯PE-UHMW提高了14℃,邵氏硬度达到69,较纯PE-UHMW提高了15%;共混材料的缺口冲击强度随PA6质量分数的增加而降低,在PA6含量不变的条件下,添加适量的增容剂能够改善共混材料的缺口冲击强度。同时结合DSC测试共混材料中PE–UHMW的结晶度与对共混材料的微观形貌扫描观察,进行了PE–UHMW与PA6的作用机理分析。     

模压成型工艺对PE–UHMW结晶度和耐磨性能的影响

在3.6 MPa的初始模压压力下,分别改变模压温度、模压时间和冷却方式对超高分子量聚乙烯(PE–UHMW)进行了模压成型,研究了PE–UHMW模压成型工艺对其结晶度和耐磨性能的影响。结果表明,在不同的模压温度或模压时间下,PE–UHMW结晶度与耐磨性能的变化没有理想的对应关系;但从整体结果可以得出,较高模压温度或较长的模压时间会导致PE–UHMW结晶度降低,耐磨性能变差。模压温度为230℃、模压时间为30 min时,PE–UHMW的耐磨性能最好。不同冷却方式对PE–UHMW结晶度的影响较小,对耐磨性能的影响较大。采用较低的冷却速率并在PE–UHMW结晶温度下保温30 min,可以得到耐磨性能优异的PE–UHMW。     

高抗冲高模量聚碳酸酯复合材料的制备

以α–磷酸锆(α–Zr P)为刚性研磨介质,超高分子量聚乙烯(PE–UHMW)为抗冲改性剂,聚碳酸酯(PC)作为基体材料,通过母粒法(两步熔融共混法)制备了高抗冲高模量复合材料。研究了PE–UHMW添加量及几种无机填料对复合材料力学性能及微观结构的影响。结果表明,当PE–UHMW含量为8份、α–Zr P含量为2份时,复合材料的冲击强度、弯曲弹性模量达到最大值。α–Zr P的加入还使复合材料的其它力学性能得到了一定程度改善。经扫描电子显微镜分析表明,α–Zr P的加入起到了助分散的作用,促进了PE–UHMW在基体树脂中的均匀分散,所以冲击性能得到进一步提高。     

超高分子量聚乙烯冲击能量吸收机理研究

在HDPE分子量8万～327万内,选择6种不同分子量试件,在室温到液氮温度范围内,系统测量各试件冲击强度(σ_i)随温度变化关系曲线。用SEM观察各试件的冲击断口形貌,用DSC和WAXD测量各试件的结晶度,并计算出HDPE分子量和缠结点密度之间关系曲线。通过结构—形态—性能之间关系研究表明,UHMW-PE分子量在150万处σ_i出现极大值,是结晶度和缠结点密度变化的共同结果,并对UHMW-PE冲击能量吸收机理进行初步探讨,得出分子链之间缠结是影响σ_i的关键因素。     

PE-UHMW分子量及其分布表征技术进展

针对常规分子量表征手段很难用于超高分子量聚乙烯(PE–UHMW)的分子量测试现状,综述了PE–UHMW分子量分布及其大小测试方法。PE–UHMW分子量分布可以通过以下方式实现:利用不同温度时溶解性不同实现分离,利用凝胶色谱柱实现分离,利用运动速度与分子量之间的关系实现分离。PE–UHMW分子量测试目前主要有黏度法、凝胶色谱连用技术、流变仪法等,其中黏度法在实际生产中得到了广泛应用,但这种方法重复性差,其可靠性和准确性还不稳定。     

PE–UHMW抗弹复合材料及其在防护领域中的应用

根据超高分子量聚乙烯(PE–UHMW)抗弹复合材料中PE–UHMW增强体宏观结构形式的不同,概述了以纤维织物、纤维UD材料、高度取向薄膜材料为主体结构的3种PE–UHMW抗弹复合材料研究与应用现状,展望了其国内外发展趋势。     

超临界CO_2微孔发泡PE–LLD/PE–UHMW共混物

研究了线型低密度聚乙烯(PE–LLD)/超高分子量聚乙烯(PE–UHMW)共混物的超临界CO2微孔发泡行为,探讨了PE–UHMW含量、发泡温度和饱和压力对泡孔形貌的影响。采用差示扫描量热仪和旋转流变仪对PE–LLD及其共混物的热性质和流变性质进行了测试和表征,并通过扫描电子显微镜表征和分析了发泡样品的泡孔形貌。结果表明,少量PE–UHMW的加入可以显著降低PE–LLD发泡样品的孔径,增加孔密度。随着发泡温度的升高,PE–LLD样品的泡孔结构会发生塌陷现象,而加入少量PE–UHMW可以提高基体的黏度,起到支撑孔壁防止塌陷的作用,并最终得到均匀的开孔结构。另一方面,当温度一定时,饱和压力升高可以降低孔径并且得到开孔形貌的泡孔结构。     

超高分子量聚乙烯膜的制备及研究进展

介绍了超高分子量聚乙烯(PE–UHMW)膜材料的国内外发展现状,总结了PE–UHMW膜材料的制备方法及其研究进展,简述了其应用领域,并指出了今后的发展方向。     

UHMW PE/PP共混改性体系研究(Ⅱ)

制备了UHMW PE/PP合金材料,研究了UHMW PE/PP共混体系的流动性和力学性能及相容剂对共混体系的增容作用,研究表明:PP能有效地改善UHMW PE流动性,但与UHMW PE为不相容体系,相容剂D能够有效提高UHMW PE/PP体系的相容性,提高了材料的拉伸强度和冲击强度,达到一定的增强和增韧效果。     

多孔PE–UHMW材料的制备及其摩擦性能的研究

采用模板–滤取法制备多孔超高分子量聚乙烯(PE–UHMW)材料,探究其存储油液和输出油液的能力及摩擦学性能。结果表明,孔隙率越大,多孔PE–UHMW的储油能力和出油能力越强。在干摩擦条件下,孔隙率越大,多孔PE–UHMW的摩擦系数越大。在贫油润滑条件下,孔隙率较高的多孔试样U30,U40,U50的摩擦系数低于普通PE–UHMW。多孔试样U40在贫油润滑条件下的摩擦系数只有干摩擦时的30.3%。因此,孔隙的存在能够提高PE–UHMW存储油液和输出油液的能力,并且能够改善贫油润滑条件下的摩擦性能。     

Synthesis of dysprosium/Mn–Cu ferrite binary nanocomposite: Analysis of structural,morphological, dielectric,and optomagnetic properties

Manganese–copper ferrite (MCFO) and dysprosium (Dy)-doped manganese–copper ferrite nanocomposites (Mn_0.5Cu_0.5Dy_xFe_2−xO₄) (x = 0, 0.05, 0.10, and 0.15) were synthesized by sonochemical method. Crystal structure and the structural parameters of the MCFO were analyzed based on the doping concentration of Dy ion. It was observed that the average crystalline size of the synthesized nanocomposite decreases when the concentration of Dy increases. The existing spherical surface morphology of the MCFO and Dy-doped MCFO nanocomposites were obtained through scanning electron microscopy. In the UV spectrum, the pristine MCFO sample showed an absorbance peak at 743 nm whereas the absorbance values of Dy-doped ferrite nanocomposite considerably shifted (blue) toward a lower wavelength (231–222 nm). The dielectric parameters of all ferrite nanocomposites were studied in the frequency range of 100 Hz to 5 MHz. The dielectric spectrum revealed that dielectric constant and loss tangent decreased with increased doping concentration of Dy ion. The saturation magnetization also changed with Dy doping in MCFO. The impact of Dy on manganese–copper ferrite changed the optical, dielectric and magnetic properties of the prepared binary ferrite nanocomposite, which can be used for microwave-absorbing material applications.     

Mechanical Properties of Compression Molded Banana Pseudo-stem Filled Unplasticized Polyvinyl Chloride (UPVC) Composites

Mechanical strengths of a banana pseudo-stem (BPS) fiber and unplasticized polyvinyl chloride (UPVC) composite were evaluated to assess the possibility of using it as a new material in engineering applications. Samples were fabricated by the compression molding process with reference to the effect of filler loading. The samples were submitted to mechanical tests to measure tensile, flexural, and impact properties of the composites. The nature of adhesion between the matrix and the reinforcement and information relating the structure of mechanical properties can be obtained by scanning electron microscopy (SEM) assessment of the composite fracture surface. The mechanical properties show that the composites did not have good adhesion between filler and matrix; on the other hand, the filler insertion improved the flexural modulus and the material rigidity.     

核壳型纳米粒子合成方法及其性能的研究进展

核壳纳米粒子作为复合纳米粒子一个重要的分支,由于其光、磁和催化等方面的优异性能,近年来引起了人们广泛的关注.本文主要介绍了核壳纳米粒子的制备方法及诸多性能,并对核壳纳米粒子的发展进行了展望.     

单向玻璃纤维-铝合金层板的几种力学性能研究

本文用实验方法研究了单向玻璃纤维-铝合金层板的拉伸性能、疲劳性能和冲击性能。利用金属体积分数理论验证了这类层板的拉伸性能。通过对其疲劳性能的实验研究，发现裂纹扩展速率的大小及刚度的下降与加载的最大循环应力密切相关的规律。实验发现该层板具有比铝合金好得多的冲击性能。     

TMPTMA在硅橡胶中的应用研究

研究了助交联剂三羟甲基丙烷三甲基丙烯酸酯(TMPTMA)对硅橡胶硫化性能、力学性能、低温性能和粘接性能的影响。结果表明,加入少量TMPTMA能改善硅橡胶的硫化特性和工艺性,提高硫化胶的硬度,降低硅橡胶的结晶温度,并有效提高硅橡胶与金属的粘接强度;但TMPTMA用量超过一定数值后,由于TMPTMA部分自聚合,在硅橡胶内形成一定的交联网络,造成两相界面粘接力变差,致使硅橡胶的拉伸强度降低。当TMPTMA用量为1份时,硅橡胶具有最佳的综合性能。     

聚氨酯种类对机械性能以及阻尼性能影响研究

分别以聚四氢呋喃醚二醇(PTMEG)、聚氧化丙烯二醇(PPG-1000)为软段,以二苯基甲烷二异氰酸酯(MDI-50、MDI-100LL),以及扩链剂1,4-丁二醇(BDO)、三羟甲基丙烷(TMP)为硬段,采用预聚体法制备了聚氨酯弹性体。并系统研究了聚氨酯体系中各组分的种类对材料机械性能和阻尼性能的影响。     

A new precursor to lightweight porous Si–Al–O–B ceramics with enhanced microwave transmissivity

Nowadays, complicated preparation processes and harsh sintering conditions wave transparent ceramics limit its further development. To solve this problem, we explore a promising precursor by adopting a polymerization-pyrolysis method to prepare porous Si–Al–O–B ceramics at a mild sintering condition (1000 °C). The porous Si–Al–O–B ceramics exhibits enhanced wave transparency at 10–16 GHz with a low dielectric constant (<3), a low loss angle tangent value (<0.01), and simultaneously, a relative high flexible strength of 82 MPa. According to the results of the XRD and FTIR analysis, porous Al₄B₂O₉ crystallization dispersed in the amorphous SiO₂ matrix constructs the main phases of the products. The changes of Al and B elements are confirmed to have an effect on the phase compositions and micro structure of the composite ceramics, which obviously affect the mechanical and dielectric properties of the derived ceramics. The as-prepared porous Si–Al–O–B ceramics could be a potential candidate for next generation electronic window materials due to its low dielectric constant and loss angle tangent value, as well as high flexible strength.     

Effects of support and additive on oxidation state and activity of Pt catalyst in propane combustion

The effects of support and additive on the oxidation state and catalytic activity of Pt catalyst in the low temperature propane combustion were systematically investigated on Pt/MgO, Pt/Al₂O₃ and Pt/SiO₂–Al₂O₃. The catalytic activity varied much with both support materials and additives. The catalyst on the more acidic support showed higher activity, and the catalytic activity on every support materials increased as the electronegativity of additives increased, while some additives decreased the activity. The oxidation state of platinum, estimated by white line intensity of Pt L_III-edge XANES spectrum, also varied with the support and additives, and additives with higher electronegativity greatly prevented the platinum from its oxidation under oxidising atmosphere. Among almost all the catalysts with various supports and various additives, a clear relationship was observed between the oxidation state of platinum and the catalytic activity; the more metallic platinum showed higher activity. Thus, it was concluded that the total electrophilic/electrophobic property derived from those of the support and additive controls the oxidation state of platinum, which intensively affects the catalytic activity; i.e. higher electrophilic property provides less oxidised platinum, resulting in high catalytic activity. The mechanism of this effect was also discussed on the basis of thermochemical data, and it was proposed that the electrophobic materials promote the noble metal oxidation since the noble metal oxo-anion such as PtO^δ− is more stabilised with electrophobic cation.     

阻隔性PET/PEN共聚酯的性能研究

对共聚型阻隔聚酯PETNx(x为共聚酯中NDA占羧酸总质量的百分比)的热性能、流变性能和阻隔性能进行了研究。结果表明,PETNx体系属于假塑性流体。PETNx的CO2气体阻隔性优于常规PET;随着PETNx中NDA含量的增加,共聚物的玻璃化温度呈线性增高。