膜分散微反应器制备高悬浮性纳米硫酸钡

以氢氧化钡和硫酸为原料,采用搅拌法和膜分散微反应器分别制备纳米硫酸钡颗粒和硫酸钡溶液,并采用XRD、TEM等手段进行测试和表征,研究常温老化和低温老化时纳米硫酸钡的生成机理,探讨氯离子和钠离子对硫酸钡性能的影响。结果表明:当氢氧化钡和硫酸的溶液浓度分别为0.5 mol/L、溶液体积流量为60 mL/min、低温老化温度为5℃时,可制备出粒径为32 nm、统计平均粒径为(24.4±5.3) nm的硫酸钡颗粒,静置24 h后的硫酸钡溶液的悬浮比高达98.1%,其性能优于常温老化法和传统搅拌法制备的;在低温老化条件下,硫酸钡颗粒生长缓慢,晶粒发育程度较低,XRD衍射峰峰强较弱,硫酸钡颗粒的粒径较小;纳米硫酸钡溶液的悬浮性与其zeta电位正相关,高悬浮性硫酸钡的zeta电位分布集中且均为正值,悬浊液稳定,分散性好;氯离子对硫酸钡颗粒粒径分布的影响较小;钠离子会显著降低硫酸钡溶液悬浮性,应避免钠离子的干扰。     

BaSO4填充改性聚四氟乙烯复合材料的制备

采用冷压成型和烧结固化相结合的方法制备了BaSO4/PTFE复合材料,对不同用量和粒径的硫酸钡填充聚四氟乙烯复合材料性能的影响进行了研究。结果表明,BaSO4填料用量和粒径大小对复合材料的性能影响很大,当BaSO4填料粒径为44μm、质量分数为40%时,复合材料的抗磨损性能最佳,比未改性的PTFE提高了2个数量级。复合材料磨损表面的SEM分析表明,随BaSO4用量的增加,复合材料的磨损机理由粘着磨损占主导逐渐转变为磨粒磨损占主导并伴随疲劳磨损。     

PEEK与纳米TiO_2填充PTFE复合材料的摩擦磨损性能研究

采用高速机械搅拌的方式充分混合原料,然后用模具将混合好的材料冷压成型,再通过一定的烧结程序制备不同体积含量的聚醚醚酮(PEEK)和纳米TiO2协同填充改性的聚四氟乙烯(PTFE)复合材料试样。利用MRH-3摩擦磨损实验机在不同实验条件下对试样进行摩擦学性能的测试。磨损后用QuantaFEG450扫描电镜对钢环表面的摩擦形貌进行观察与分析。实验结果表明,填充PEEK可大幅降低PTFE复合材料的体积磨损率,但复合材料的摩擦系数却随PEEK含量的增加而表现出逐渐上升的趋势。用不同含量的纳米TiO2填充10%PEEK/PTFE,摩擦系数和体积磨损率都表现出随纳米TiO2含量的增加而逐步上升的趋势,其中2%Nana-TiO2/10%PEEK/PTFE复合材料的摩擦系数和体积磨损率最小。当滑动速度和载荷分别超过2m/s和200N后对复合材料的磨损率有显著地影响,而环境温度在25~120℃范围内变化对磨损率和摩擦系数的影响均不明显。     

PEEK与纳米SiO_2填充PTFE复合材料的摩擦磨损性能研究

通过机械共混、冷压成型、烧结的方法制备聚醚醚酮(PEEK)与纳米Si O2颗粒共同填充改性聚四氟乙烯(PTFE)复合材料试样。利用MRH-3型环-块摩擦磨损实验机对不同配方比例的复合材料在不同实验条件下进行摩擦学性能实验。利用扫描电镜对试样磨损后的摩擦表面形貌和钢环表面的转移膜进行观察和分析。结果表明,填充5%PEEK的PTFE复合材料的摩擦系数达到最低值;10%PEEK/PTFE复合材料中添加不同体积比的纳米Si O2填料可以显著地降低材料的体积磨损率,其中5%Nano-Si O2/10%PEEK/PTFE复合材料的体积磨损率最小;载荷和速度的变化对Nano-Si O2/PEEK/PTFE复合材料的摩擦磨损性能的影响显著,而环境温度的变化对该复合材料的摩擦系数与磨损率的影响不明显。     

填充纳米氧化铝对氢化丁腈橡胶摩擦磨损行为的影响

以采油单螺杆泵定子常用材料氢化丁腈橡胶(HNBR)为研究对象,改性纳米氧化铝(Al_2O_3)为填充剂,实验研究了填充不同粒径氧化铝对橡胶材料的交联密度、耐原油溶胀性能和摩擦磨损性能的影响,并分析了Al_2O_3对HNBR材料的补强机理。结果表明,填充纳米氧化铝的HNBR材料的交联密度、耐原油溶胀性能均有所提高,且交联密度和耐原油溶胀性能随Al_2O_3粒径的减小而提高;摩擦磨损试验结果表明,填充纳米氧化铝后,HNBR材料的摩擦系数和体积磨损率降低,且摩擦系数和体积磨损率随着填充Al_2O_3粒径的减小而减小,即填充10 nm Al_2O_3的HNBR材料耐磨性较好。纳米氧化铝补强HNBR机理是填充Al_2O_3后形成了以Al_2O_3为交联点的交联网络以及Al_2O_3表面的不饱和基团自聚后形成的大分子链与HNBR分子链互穿缠绕形成类似互穿聚合物的网络结构。     

新型高导热绝缘包覆母排材料的制备及性能

以甲基乙烯基硅橡胶为基体,氧化铝为导热填料制备了一种高导热绝缘包覆母排材料,并对其力学性能、热导率、形貌和介电性能进行了测定。研究表明,随着氧化铝含量的增加,导热性能和力学性能相应提高,介电损耗升高,介电强度下降;小粒径填充的导热材料性能比大粒径填充的导热材料性能好;硅烷偶联剂及表面处理方式对导热材料性能有一定的影响;混杂粒径填充能适当提高导热材料的导热性能。     

OTS自组装改性PTW增强PTFE复合材料的非等温结晶动力学

采用冷压烧结的方法制备了纯聚四氟乙烯(PTFE)、未处理钛酸钾晶须(PTW)及十八烷基三氯硅烷(OTS)自组装改性PTW填充的PTFE复合材料。研究了PTFE及改性前后PTW的静态接触角,用差示扫描量热(DSC)法并结合Jeziorny方程研究了PTFE及其填充改性前后PTW复合材料的非等温结晶动力学。结果表明,Jeziorny方程能够较好地描述复合材料的非等温结晶动力学,PTW在PTFE基体中起异相成核作用,加快了PTFE的结晶速率。OTS能够明显提高PTW的憎水性能,这使PTW的异相成核能力得到增强。     

OTS自组装改性PTW增强PTFE复合材料的非等温结晶动力学EI北大核心

采用冷压烧结的方法制备了纯聚四氟乙烯(PTFE)、未处理钛酸钾晶须(PTW)及十八烷基三氯硅烷(OTS)自组装改性PTW填充的PTFE复合材料。研究了PTFE及改性前后PTW的静态接触角,用差示扫描量热(DSC)法并结合Jeziorny方程研究了PTFE及其填充改性前后PTW复合材料的非等温结晶动力学。结果表明,Jeziorny方程能够较好地描述复合材料的非等温结晶动力学,PTW在PTFE基体中起异相成核作用,加快了PTFE的结晶速率。OTS能够明显提高PTW的憎水性能,这使PTW的异相成核能力得到增强。     

车用内饰填充改性聚丙烯材料耐刮擦性研究

主要考察了基体树脂、增韧剂、填充剂和相容剂对聚丙烯复合材料耐刮擦性的影响,结果表明:(1)就基体树脂而言,均聚聚丙烯耐刮性优于共聚聚丙烯。(2)与其他矿物填料相比,滑石粉填充改性聚丙烯材料的耐刮性最好;另外,滑石粉粒径越小,填充改性聚丙烯材料的耐刮性越好;但当填料粒径小于1μm时,需加强其在聚合物基体中的分散或者进行预分散。(3)随着增韧剂含量增加,流动性提高,填充改性聚丙烯材料的耐刮擦性越好;但超过含量12%(wt,质量分数,下同)以后,聚丙烯材料刮擦值变化不大。(4)相容剂可以有效改善填充改性聚丙烯材料的耐刮擦性,但含量不宜超过5%。     

SiO2/聚四氟乙烯复合薄膜的制备及力学性能

采用空气辅助干法共混、冷压烧结并车削成膜的方法制备了SiO₂填充量为35wt%、厚度为50 μm的聚四氟乙烯（PTFE）基复合薄膜。系统研究了SiO₂颗粒粒径对SiO₂/PTFE薄膜复合材料的孔洞缺陷和力学性能等的影响,并研究了SiO₂在PTFE中的分散情况及分子间相互作用对其性能变化的影响机制。结果表明,随SiO₂粒径的逐渐增大,其在PTFE中的分散趋于均匀,同时PTFE能更好地包覆粒子,因此SiO₂/PTFE薄膜孔洞缺陷逐渐减少,力学性能逐渐增强;当SiO₂的粒径D₅₀为12 μm时,其在PTFE中的分散均匀性最佳,SiO₂/PTFE复合薄膜孔洞缺陷最少,具有较好的力学性能,断裂伸长率达19.5%,拉伸强度达9.2 MPa。      

PTFE基复合材料摩擦磨损特性研究

用机械共混、冷压成型自由烧结的方法制备了PTFE基复合材料;用M-2000型磨损试验机测试了在干摩擦定载荷条件下各试样的磨损性能;用扫描电子显微镜(SEM)对磨损试样的表面形貌进行了观察和分析.结果表明:在实验条件下,复合材料的抗磨性能,随青铜粉用量的增大逐渐增强,当青铜粉的用量大于20vol.%后,抗磨损性能增强的趋势明显减缓,在干摩擦条件下复合材料主要发生粘着磨损和磨粒磨损,且随青铜粉用量的增加,磨粒磨损也越明显.研究发现,当青铜粉:氧化镉:二硫化钼为20:6:4(体积比)时,复合材料的摩擦磨损性能最佳.     

钡铁氧体磁粉在液相中的分散性能

为了提高分散作用效果,选用聚乙二醇-20000(PEG-20000)、十二烷基硫酸钠(SDS)及二者组成的复配分散剂,利用机械球磨与添加分散剂相结合的分散方法制备了钡铁氧体浆料,通过考察分散剂的用量、浆料的pH值、zeta电位对分散性的影响,根据红外光谱分析,研究了分散剂的分散效果及作用机理,并测定了分散前后磁场成型各向异性钡铁氧体材料的磁性能。结果表明:加入分散剂可以改善钡铁氧体的分散效果,且SDS和PEG-20000的用量为钡铁氧体质量的1%和2%时,分散效果最好。SDS和PEG-20000均为静电和空间位阻稳定作用。分散后磁场成型各向异性钡铁氧体材料的磁性能得到提高。     

Preparation and properties of hollow glass bead filled silicone rubber foams with low thermal conductivity

Silicone rubber foams filled with various content and different particle size of hollow glass bead (HGB) were prepared by compression molding. It was revealed that compared with silica filled silicone rubber foams, HGB filled materials achieved higher foaming extent, lower thermal conductivity, and lower hardness, which can be significant for thermal insulation materials. For HGB filled materials, the morphology indicated the average cell size decreased with higher HGB content and larger particle size of HGB. The density, thermal conductivity, hardness and tensile strength increased with higher HGB content and larger particle size of HGB.     

硅线石填充双马来酰亚胺摩擦学性能的研究

用Ｍ－２００型试验机在干摩擦条件下考察了硅线石单独填充双马来酰亚胺（ＢＭＩ）和硅线石与聚四氟乙烯（ＰＴＦＥ）共同填充ＢＭＩ两类复合材料的摩擦学特性。结果表明，适量的Ｓａ能降低ＢＭＩ的摩擦系数和磨损量，但会在对偶件上造成划伤，ＰＴＦＥ与Ｓａ共同填充ＢＭＩ，不仅能进一步降低复合材料的μ和磨损量，而且能有效地抑制对偶件上的划伤，经过分析，Ｓａ填充ＢＭＩ的复合材料，对磨时其表面较高的粗糙度和Ｓａ硬粒子友承     

Tribological behaviour of proposed polymeric bearing materials

The aim of the present work is to introduce new polymeric bearing materials. The proposed polymeric composites are consisting of polyethylene (PE), polypropylene (PP) and polystyrene (PS) and filled by fibres of polytetrafluoroethylene (PTFE) in concentration up to 25 wt.% as well as different types of natural oils such as (corn oil, olive oil, paraffin oil, glycerin oil, castor oil and sunflower oil) in concentration up to 10 wt.%. The frictional behavior of the proposed composites and wear resistance are investigated at different values of applied load. Based on the experimental observations, it was found that for composites free of oil, friction of PS and PE specimens decreased, while friction of PP specimens slightly increased with increasing PTFE content. PP composites filled by corn oil showed slight friction increase. Besides, friction coefficient displayed by PS and PE specimens filled by glycerin oil decreased with increasing oil content, while friction coefficient displayed by PP specimens showed consistent trend. It was noted that, PE filled with 7.5% glycerin oil and 20 wt.% PTFE displayed the minimum value of friction coefficient (0.07). This friction coefficient values recommend those composites to be used as bearing materials. PE filled by glycerin oil displayed relatively lower friction values due its common known good lubricating property. Friction of PE composites filled by paraffin oil drastically decreased with the increasing oil content. PP composites showed the lowest wear values. In addition to that, it was shown that wear displayed by composites filled by glycerin oil was higher than that containing corn oil, while wear of the tested composites filled with olive oil showed lower values than that displayed by corn oil filled composites. Composites containing 5.0–7.5% paraffin oil content showed good wear resistance which recommends them to be used as bearing material. Wear of PP, PS and PE composites filled with sunflower oil and 15 wt.% PTFE drastically decreased with increasing oil content. The minimum wear was displayed by PP and PE composites filled with 10% oil content.     

SiO2-TiO2/聚四氟乙烯复合材料的制备及热膨胀性能

为了使微波基板材料与Cu金属衬底的热膨胀性能匹配,对陶瓷/聚四氟乙烯（PTFE）微波复合基板材料的热膨胀性能进行了研究。采用湿法工艺制备了以SiO₂和TiO₂为填料的SiO₂-TiO₂/PTFE复合材料,研究了复合材料密度、填料粒度和填料体积分数对SiO₂-TiO₂/PTFE复合材料热膨胀性能的影响。结果表明,当SiO₂的体积分数由0增至40%（TiO₂ ：34%~26%）时,SiO₂-TiO₂/PTFE复合材料的线膨胀系数（CTE）由50.13×10^-6 K^-1减小至10.03×10^-6K^-1。陶瓷粉体粒径和复合材料密度减小会导致CTE减小。通过ROM、Turner和Kerner模型计算CTE发现,ROM和Kerner模型与实验数据较相符,而实验值与Turner模型预测值之间的差异随PTFE含量的升高而逐渐增大。     

Optimising durability of PTFE seals — mix and geometry — a good match

The use of PTFE and PTFE compounds as materials for seals provides additional security in terms of durability, friction, robustness and product design. Success is achieved by optimally matching the sealing material with the counter-rotational surface.     

丙二酸处理硫酸钡填充等规聚丙烯复合材料的结晶性能

采用差示扫描量热仪、广角X射线衍射仪、偏光显微镜研究了等规聚丙烯/沉淀法硫酸钡复合材料在120℃等温结晶后的熔融和结晶行为.结果表明,与未处理填料体系相比,丙二酸处理硫酸钡有利于聚丙烯中β晶的形成,β晶晶粒明显细化.在7.5%填料含量时,丙二酸处理硫酸钡复合材料的β晶型相对含量(KWAXD)达到最大值0.853,而未处...     

纳米TiO2与炭纤维协同填充PTFE复合材料的摩擦磨损性能

考察了不同含量的纳米二氧化钛对炭纤维/聚四氟乙烯复合材料摩擦磨损性能的影响,采用扫描电子显微镜、光学显微镜分析了磨损面、磨屑及对偶面转移膜形貌,并探讨了其磨损机理。结果表明,纳米TiO2与炭纤维能够很好地协同增强聚四氟乙烯,改变磨屑形成机理,有利于形成均匀致密的转移膜,明显提高CF/PTFE复合材料的耐磨性。当纳米TiO2含量为5%时,10?/PTFE复合材料表现出最佳的耐磨性,耐磨性又提高了2.77倍,而磨屑尺寸只有未加时的1/20。     

Effect of volume fraction and wall thickness on the elastic properties of hollow particle filled composites

Hollow particle filled composites, called syntactic foams, are widely used in applications requiring high damage tolerance and low density. The understanding of the mechanics of these materials is largely based on experimental studies. Predictive models that are capable of estimating the elastic properties of these materials over wide variation of particle wall thickness, size, and volume fraction are not yet fully developed. The present study is focused on developing a modeling scheme to estimate the elastic constants for such materials. The elastic properties of an infinitely dilute dispersion of microballoons in a matrix material are first computed by solving a dilatation and a shear problem. A differential scheme is then used to extrapolate the elastic properties of composites with high volume fractions of microballoons. The results show that the model is successful in predicting the Young’s modulus for syntactic foams containing microballoons of a wide range of wall thickness and volume fraction.