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。     

PTFE/SGM复合材料非等温结晶动力学

通过冷压烧结工艺制备了聚四氟乙烯/实心玻璃微珠(PTFE/SGM)复合材料。采用差示扫描量热法(DSC)研究了PTFE/SGM复合材料的非等温结晶行为,并利用Jeziorny模型对所得DSC数据进行处理。结果表明:Jeziorny模型处理PTFE/SGM复合材料的非等温结晶动力学过程是合理可行的;随着冷却速率的增加,结晶峰向低温方向移动,结晶温度范围增大,结晶度下降;SGM有一定的成核作用,提高了PTFE的结晶峰温和结晶速率,降低了结晶活化能,使PTFE更易结晶。     

聚羟基丁酸酯的等温与非等温结晶动力学

用差示扫描量热法(DSC)研究了聚羟基丁酸酯(PHB)的等温与非等温结晶动力学。采用Avrami方程分析了等温结晶动力学,Avrami指数n≈2,表明PHB以异相成核的二维平面晶体方式生长,等温结晶活化能为82.4 kJ/min。采用Jeziorny法和莫志深法分析了PHB的非等温结晶动力学,Avrami指数n≈3,表明PHB非等温结晶过程以异相成核的三维球晶方式生长。     

聚乙烯/有机蒙脱土纳米复合材料结晶动力学

采用熔融插层法制备了聚乙烯/有机蒙脱土纳米复合材料,利用示差扫描量热法(DSC)研究了复合材料的等温及非等温结晶行为,并与纯聚乙稀进行了比较.通过Avrami方程,修正Avrami方程的Jeziorny法及Ozawa法分别对等温及非等温结晶过程进行了处理.结果表明:蒙脱土片层在复合材料结晶过程中起到了异相成核作用,复合材料的成核机理与生长方式已不同于聚乙烯;在相同结晶条件下,复合材料的结晶速率明显比聚乙烯快;纯PE的表观活化能为142.14 kJ/mol,而复合材料为158.38 kJ/mol,复合材料的活化能有一定程度提高;对非等温结晶过程分析,Jeziorny方法适用,而Ozawa方法不适用.     

聚丙烯/硬石膏复合材料的非等温结晶动力学

采用DSC研究了聚丙烯(PP)及聚丙烯/硬石膏复合材料的非等温结晶动力学,对所得数据用修正Avrami方程的Jeziorny法和Mo法进行处理。结果表明:硬石膏的加入提高了PP的结晶温度Tp和结晶速率,降低了结晶活化能ΔE,使实际降温速率下PP更易结晶。同样的含量下,经铝酸酯偶联剂改性硬石膏使PP结晶速率加快,但ΔE有小幅上升。研究表明,硬石膏有异相成核作用,填加20%时异相成核多于填加10%时,铝酸酯偶联剂的改性对该作用无明显影响。     

新型无卤膨胀阻燃低密度聚乙烯复合材料的非等温结晶动力学

通过熔融混合将有机杂环磷酸酯1,3,5-三(5,5-二甲基-1,3-二氧杂环己内磷酸酯基)苯(FR)和聚磷酸铵(APP)组成的膨胀阻燃剂(IFR)与低密度聚乙烯(LDPE)作用,制备出新型膨胀阻燃低密度聚乙烯复合材料(IFR/LDPE)。用差示扫描量热法(DSC)研究IFR对LDPE非等温结晶行为的影响,用Jeziorny法、Ozawa法及莫志深法研究了低密度聚乙烯阻燃改性前后的非等温结晶动力学,并用Kissinger法、Takhor法研究了纯LDPE及IFR/LDPE共混体系结晶活化能的变化。结果表明:IFR的加入在提高LDPE阻燃性能的同时,对LDPE结晶起到异相成核作用,但是阻碍了PE分子链的规则排列,使LDPE晶体的生长减慢,最终使阻燃聚乙烯总的结晶速率降低。     

聚丙烯/微晶纤维素复合材料的非等温结晶动力学研究

用熔融复合法制备聚丙烯/微晶纤维素复合材料,用DSC法研究其非等温结晶行为,分别用Jeziorny法、Ozawa法和Mo法对所得的数据进行处理.结果表明,Jeziorny法和Mo法处理非等温结晶过程比较理想,MCC的加入缩短了t1/2,起到了异相成核作用.     

r-PTFE对PBT非等温结晶动力学的影响

以回收聚四氟乙烯(r-PTFE)为成核剂,对聚对苯二甲酸丁二醇酯(BPT)进行成核结晶改性,采用差示扫描量热仪(DSC)研究了PBT/r-PTFE复合材料的非等温结晶行为,考察了不同降温速率对PBT/r-PTFE共混物结晶行为的影响,并对其DSC扫描数据采用Jeziorny法和Liu-Mo法进行处理,采用Kissiinger法计算体系结晶活化能。结果表明:r-PTFE对PBT具有异相成核作用,可明显提高PBT的结晶度及其结晶速率,且加入r-PTFE并不会改变PBT的成核和增长方式。由Kissinger法计算得出的结晶活化能结果表明,加入r-PTFE树脂能够明显降低PBT的结晶活化能,进一步验证r-PTFE对PBT具有成核促进作用。     

尼龙6/粘土聚合物纳米复合材料的性能表征--(Ⅱ)结晶行为研究

使用Haake-90型双螺杆挤出机制备一系列粘土含量不同的尼龙6/粘土纳米聚合物复合材料,通过X射线衍射和差示扫描量热仪(DSC)研究其结晶行为.X射线衍射结果表明纳米粘土的加入改变了尼龙6的晶型.用修正Avnmi方程的Jeziorny法研究材料的非等温结晶动力学,发现纳米复合材料的半结晶时间t1/2缩短,纳米粘土对尼龙6有明显的异相成核作用.     

PTFE/SiO2复合材料的DSC分析及其结晶行为研究

采用DSC技术,研究不同热压温度制备的PTFE/SiO2复合材料以及纳米SiO2部分取代微米SiO2的PTFE/SiO2复合材料的非等温结晶行为。DSC分析表明热压温度高于370℃时,PTFE分子聚合度下降,晶态PTFE微观形貌发生改变,其性能恶化。对复合材料非等温结晶DSC曲线应用Avrami方程分析发现,结晶过程包含了均相成核和异相成核两种成核机理。纳米SiO2取代部分微米SiO2量小于0.25%时,对PTFE成核作用有一定提升,当取代量大于0.25%时,由于偶联剂用量一定,造成SiO2颗粒团聚以及与PTFE界面相容性变差,成核效果不明显。     

稀土处理玻璃纤维填充PTFE复合材料的滑动磨损性能

研究了不同玻璃纤维表面处理对PTFE复合材料在干摩擦条件下滑动磨损性能的影响,并借助扫描电子显微镜(SEM)分析了磨损机理。结果表明:在干摩擦条件下,经表面处理玻璃纤维填充的PTFE复合材料的摩擦系数和摩擦表面温度比未经处理玻璃纤维填充的PTFE复合材料的低,且减磨性能优于未经处理的;而稀土处理玻璃纤维填充的PTFE复合材料的摩擦系数和摩擦表面温度最低,减磨性能最好;未经处理玻璃纤维填充的PTFE复合材料和偶联剂处理玻璃纤维填充的PTFE复合材料都发生了剧烈的粘着转移;偶联剂与稀土处理玻璃纤维填充的PTFE复合材料的磨损机理主要是明显的磨粒磨损;稀土处理玻璃纤维填充PTFE复合材料的磨损形式主要是粘着转移和轻微的磨粒磨损。     

微米和纳米SiO2改性聚四氟乙烯的摩擦磨损性能

使用超细及纳米SiO₂颗粒填充改性聚四氟乙烯塑料。测量其摩擦系数、磨损系数、结晶度,得到了填加量与复合材料摩擦系数、磨损系数和结晶度的关系曲线,并使用扫描电镜(SEM)对其表面形貌进行了分析。结果表明,无论微米或纳米SiO₂、表面处理后的纳米SiO₂,均使PTFE的摩擦系数有所提高,而耐磨损性能也有大幅度的提高。填充量小于6%时,填加未经偶联剂处理的纳米SiO₂的SiO₂/PTFE复合材料的磨损率降低98.5%;填充量大于6%以后,磨损率趋于稳定;填充量为6%时,摩擦系数仅从未加填料时的0.1提高为0.12。而偶联剂表面处理的纳米SiO₂复合材料的摩擦系数提高幅度最小。      

Preparation,damping and thermal properties of potassium titanate whiskers filled castor oil-based polyurethane/epoxy interpenetrating polymer network composites

A series of potassium titanate whiskers (PTW) filled castor oil-based polyurethane (PU)/epoxy resin (EP) interpenetrating polymer network (IPN) composites were prepared. The damping properties, thermal stability as well as tensile strength of the IPN composites were studied systematically in terms of composition. Results revealed that the addition of PTW can significantly improve the damping properties of pure PU/EP IPN and can improve the thermal decomposition temperature. Tensile tests showed that the tensile strength of the IPN composites was improved after the incorporation of PTW. It is expected that the PTW filled IPN composites may be used as structural damping materials.     

Tribological properties of PTFE composites filled with surface-treated carbon fiber

Carbon fibers (CF) were surface treated with concentrated HNO₃, silane coupling agent, rare earth solution and rare earth sol, respectively. The friction and wear behavior of polytetrafluoroethylene (PTFE) filled with differently surface treated CF were studied. The worn surfaces of CF/PTFE composites were then examined with scanning electron microscope (SEM). It is found that the wear volume loss of the rare earth sol treated CF filled PTFE composites reaches the lowest value when the modifier concentration is 10 wt%. It is only about 65% of the wear volume loss of the PTFE filled with untreated CF. Among all the treatments to CF, rare earth sol treatment is the most effective and the lowest friction and wear volume loss of CF/PTFE composite is exhibited.     

钛酸钾晶须改性MC尼龙的吸湿行为及摩擦学特性

机车心盘衬垫的性能易受湿度的影响而很不稳定,为了改善吸湿性对机车心盘衬垫性能的影响,在提高制品的韧性和强度的同时,获取高且稳定的摩擦系数,通过碱催化阴离子聚合反应制备了钛酸钾晶须/MC尼龙复合材料,并经过水浴处理。利用MM2000型摩擦磨损实验机测试了在干摩擦条件下吸湿性对钛酸钾晶须/MC尼龙复合材料摩擦学性能的影响。实验发现,未水浴处理试样的摩擦系数易受吸湿性的影响而不稳定,水浴处理试样的摩擦系数则能较快地稳定。纯尼龙以粘着磨损为主,钛酸钾晶须的加入大大降低了粘着磨损程度。晶须填充试样的总质量磨损率小于纯尼龙试样,但吸湿性对材料磨损特性的影响并不明显。晶须填充MC尼龙在水浴处理的条件下能明显改善吸湿性对MC尼龙摩擦学性能的影响。      

纤维/Ekonol/PTFE复合材料的力学与摩擦学性能研究

对比考察了碳纤维(CF)、六钛酸钾晶须(PTW)分别与聚苯酯(Ekonol)混合填充对聚四氟乙烯(PTFE)复合材料的力学与摩擦学性能的影响,并探讨了内部机理.结果表明:PTW相比于传统纤维CF,尺寸细微,具有微区增强特性,PTW的填充提高了Ekonol/PTFE复合材料的致密程度,协助形成更为均匀、致密的转移膜,相比于CF/Ekonol/PTFE复合材料,有着较好的力学性能、摩擦稳定性、耐磨性,进一步改善了Ekonol/PTFE复合材料的综合性能.纤维、Ekonol混合填充PTFE,二者表现出协同润滑与减磨效应.纤维协助均匀、致密的转移膜的形成;而硬质Ekonol颗粒在纤维和对偶之间可能起到了一种第三体滚动效应,避免了纤维受到较为严重的磨损,从而提高复合材料的摩擦磨损性能.     

Tribological behavior of poly (phenyl p-hydroxybenzoate)/polytetrafluoroethylene composites filled with hexagonal boron nitride under dry sliding condition

The sliding friction and wear behavior of polytetrafluoroethylene (PTFE) composites filled with poly (phenyl p-hydroxybenzoate) (PHBA) and hexagonal boron nitride (h-BN) was investigated with a pin-on-disc tester. The tensile properties, ball indentation hardness, impact strength and thermal diffusivity were measured. The test results in this paper indicate that the tensile strength, elongation at break, and impact strength decreased, however, the ball indentation hardness and thermal diffusivity were increased when the content of h-BN was increased. PTFE composites filled with 20 wt% PHBA and 20 wt% h-BN exhibited a comparative friction coefficient to pure PTFE. Meantime, the wear rate of the composite decreased about 15 times compared to pure PTFE. The synergistic effect of h-BN with low friction and PHBA with high bearing ability promoted the low friction coefficient and wear rate of h-BN/PHBA/PTFE composites.     

纳米蒙脱石填充PTFE和UHMWPE的摩擦磨损性能

用纳米蒙脱石(nano-MMT)对聚四氟乙烯(PTFE)和超高分子量聚乙烯(UHWMPE)进行填充改性,在往复式滑动摩擦试验机上进行摩擦磨损实验,用扫描电镜观察了材料摩擦表面形貌.结果表明:nano-MMT可以提高PTFE和UHWMPE材料的耐磨性,而PTFE基和UHWMPE基复合材料的摩擦系数无明显增大.与UHMWPE相比,nano-MMT更能提高PTFE基材料的耐磨性;nano-MMT/PTFE复合材料比nano-MMT/UHMWPE复合材料具有更低的摩擦系数和更好的导热性;纯PTFE、纯UHWMPE和10%nano-MMT/PTFE复合材料磨损机理主要为粘着和犁沟效应,而10%nano-MMT/UHWMPE复合材料表现为犁沟和疲劳机制.     

埃洛石-玻纤/聚四氟乙烯复合材料的摩擦磨损热膨胀及力学性能

采用冷压成型烧结工艺制备出玻璃纤维（GF）和埃洛石（HNTs）填充的聚四氟乙烯（PTFE）复合材料。研究了填料类型及不同配比的填料对PTFE复合材料的界面、摩擦学性能、线膨胀系数及力学性能的影响。结果表明:适量填充HNTs可以提升GF/PTFE复合材料的摩擦磨损、热膨胀及力学性能。填充2.0%HNTs时的HNTs-GF/PTFE复合材料比GF/PTFE复合材料的磨损率降低32.7%,高温时HNTs-GF/PTFE复合材料的线膨胀系数（CTE）比纯PTFE降低近2个数量级,断裂伸长率、拉伸强度和弯曲强度分别提高40.0%、2.3%和7.1%。      

Friction and wear behavior of the polyurethane composites reinforced with potassium titanate whiskers under dry sliding and water lubrication

A series of polyurethane (PU)/potassium titanate whiskers (PTW) composites modified by a high molecular weight hydroxyl-terminated polydimethylsiloxane (HTPDMS) were prepared. The PTW is modified by 2,4-diisocyanatotoluene (2,4-TDI). The effect of the PTW content on the mechanical and tribological properties of the PU composites was studied. Tensile strength of the PU composites increased with the addition of PTW. The friction and wear experiments were tested on a MRH-3 model ring-on-block test rig at different sliding speeds and loads under dry sliding and water lubrication. Experimental results revealed that the small content of PTW contributed to largely improve the tribological properties of the PU composites. The coefficient of friction (COF) of the composites increased and the wear rate value decreased with increasing PTW. Scanning electron microscopic (SEM) investigations showed that the worn surfaces of the PTW-reinforced PU composites was smoother than pure polyurethane under given load and sliding speed.