PA6原位成纤改善PPR的挤出流变性能

采用原位成纤复合法制备了无规共聚聚丙烯(PPR)/尼龙6(PA6)复合样品,研究了PA6的原位微纤化对PPR熔体挤出流变性能的影响。结果表明,采用的"挤出-热拉伸-淬冷"工艺可实现PA6在PPR基体中的原位微纤化;少量PA6对PPR的挤出螺纹畸变有改善效果;添加相容剂PP-g-MAH(马来酸酐接枝聚丙烯)有利于改善PPR和PA6两相的界面相容性,并明显改善PPR的挤出螺纹畸变。当PA6质量分数为5%时,加入PP-g-MAH后挤出物外观质量较好,出现螺纹畸变的"临界"表观剪切速率从246s-1增大到719s-1。     

关于纳米蒙脱土影响聚己内酰胺结晶行为及流变行为的研究

通过双螺杆挤出机熔融挤出生产有机改性纳米蒙脱土(MMT)增强聚己内酰胺(PA6)。使用差示扫描量热仪开展自成核试验及非等温结晶行为研究,了解纳米MMT含量对PA6结晶行为的影响,结果表明:少量的纳米MMT可以明显提高成核效率和结晶速率,但继续增加纳米MMT会抑制PA6结晶生长,降低结晶速率和结晶度。使用广角X射线衍射仪研究PA6的结晶行为,结果表明:纯PA6同时存在α及γ晶型,添加纳米MMT的PA6发生α-γ晶型转变,证实纳米MMT与PA6的作用可以改变PA6的结晶行为。使用毛细管流变仪分析纳米MMT含量对PA6熔体受剪切时流变行为的影响,结果表明:纳米MMT含量影响PA6熔体的黏度及非牛顿流体特征,尤其是高纳米MMT含量的PA6在不同剪切速率下表现出明显的黏度变化。     

尼龙612及其共聚物流变性能的研究

采用毛细管流变仪对尼龙612/6(PA 612/6)共聚物的流变性能进行了研究,并与PA 612进行比较。结果表明:PA 612/6共聚物和PA 612熔体均为剪切变稀的假塑性非牛顿流体,在相同温度和剪切速率下,PA 612/6共聚物熔体的表观黏度均小于PA 612的;在温度为240℃时其非牛顿指数分别为0.749,0.748;随着温度的升高,两者熔体的表观黏度和稠度系数均逐渐下降,非牛顿指数逐渐增大;PA 612/6共聚物和PA 612熔体的黏流活化能随剪切速率的增大先增大后减小,在剪切速率为115 s~(-1)左右时,两者的黏流活化能达到最大,分别为61.49,61.27 kJ/mol,此时熔体的表观黏度对温度的敏感性最强。     

基于稳态流变测试的水泥浆体剪切模式研究

采用RHEORIAB QC型旋转黏度计测定不同剪切方式下水泥浆体稳态流变曲线,并用修正宾汉姆流变模型对其进行拟合,研究了剪切方式对水泥浆体稳态流变测试的影响.结果表明:预剪切对水泥浆体动态屈服应力和塑性黏度影响不大.恒定剪切变形速率小于、等于、大于、偏大于水泥浆体结构抗剪切破坏能力时,剪切应力随时间分别先线性增加接着保持同一值、直接保持恒定值、先减小接着保持同一值、轻微增加后达到平衡.随剪切速率增加,水泥浆体在0.1～100 s-1、100～400 s-1、400～600 s-1三个区段依次呈现出剪切变稀、宾汉姆流体、剪切增稠的流变行为.剪切速率变化范围向剪切变稀或剪切增稠段移动,水泥浆体动态屈服应力减小、塑性黏度增大;单个剪切速率的剪切时间越长,水泥浆体动态屈服应力、塑性黏度均越小.     

聚酰胺66/凹凸棒粘土纳米复合材料的制备及其性能研究

对商品凹凸棒粘土提纯、钠化、有机化后,与聚酰胺66(PA66)经双螺杆共混挤出得到PA66/凹凸棒粘土纳米复合材料。用透射电镜(TEM)和扫描电镜(SEM)研究了PA66/凹凸棒粘土纳米复合材料的微观结构,并测试了复合材料的力学性能和热性能。结果表明,凹凸棒粘土在PA66中达到纳米级分散,凹凸棒粘土的粒径小于100nm,并且在合适的添加量时复合材料的拉伸强度和热性能都有一定程度的提高。     

PB/nano-SiO2复合材料的流变性能

采用熔融共混法制备了聚丁烯(PB)/nano-SiO2复合材料,并用毛细管流变仪研究了PB及其复合材料在较宽剪切速率(1×102～6×103s-1)的流变行为.讨论了nano-SiO2含量、剪切应力、剪切速率及温度对熔体流变性、非牛顿指数和黏流活化能的影响.结果表明:PB及其复合材料的非牛顿指数均小于1,但PB/nano-SiO2的非牛顿指数大于PB的;随nano-SiO2含量增加,PB/nano-SiO2复合材料非牛顿指数上升;PB/nano-SiO2复合材料的熔融流动性随nano-SiO2用量的增加而下降;相同剪切速率时,PB/nano-SiO2的黏流活化能大于PB的.     

PA6/MMT/SGF复合材料的流变性能

利用毛细管流变仪和动态流变仪分别测试了纯尼龙(PA)6以及PA6/蒙脱土(MMT)和PA6/MMT/短玻璃纤维(SGF)复合材料的剪切粘度、复数粘度、储能模量和损耗模量,并用Han曲线分析了材料的粘弹特性.结果表明,在低剪切速率下,PA6/MMT和PA6/MMT/SGF复合材料的剪切粘度大于纯PA6的剪切粘度;在高剪切速率下,PA6/MMT和PA6/MMT/SGF复合材料剪切粘度低于纯PA6的剪切粘度.动态流变测试显示,PA6/MMT/SGF复合材料在低频区呈类固响应,其储能模量和复数粘度明显提高.Han曲线表明,PA6/MMT/SGF复合材料的粘性响应占主导地位.     

SEED改性PA 6切片的流变性能研究

采用RG20毛细管流变仪研究了N,N'-双(2,2,6,6-四甲基-4-哌啶基)-1,3-苯二甲酰胺(SEED)改性聚己内酰胺(PA 6)有光切片和半消光切片的流变性能。结果表明:在剪切速率(γ)为0~1 600 s-1条件下,SEED改性PA 6熔体为假塑性流体,表观黏度随着γ的增加而下降,SEED改性PA 6熔体的非牛顿指数均小于1;在相同γ下,有光切片的黏流活化能(Eη)较半消光切片的低,而对于同一PA 6试样,其Eη随γ的提高而降低;经SEED改性后PA 6的热稳定性得到提高,纺丝稳定性得到改善。     

制备HDPE/PA-6阻隔性共混合金工艺条件的研究

本文通过测试HDPE、PA 6的流变性能、共混合金的溶剂透过率和PCM,研究了制得阻隔性层状HDPE/PA 6共混合金工艺条件,如加工温度、剪切速率和混合时间等。结果表明:改变加工温度可以调节HDPE/PA 6共混组成粘度比,当PA 6与HDPE的粘度比较大时,能得到PA 6相呈层状分布结构的阻隔性共混合金;剪切作用有利于共混体系两相的分散,适当的剪切速率有利于使PA 6相形成层状结构。较高的剪切速率使PA 6相尺寸减,分散更均匀,但对提高共混物的阻隔性不利;较短的混合时间可以获得具有阻隔性的HDPE/PA 6共混合金体系     

固相剪切碾磨制备PA6/蒙脱土纳米复合材料

采用固相剪切碾磨方法制备尼龙6/蒙脱土(PA6/MMT)纳米复合材料。表征了复合材料的结构,研究了其力学性能、热稳定性能及结晶性能。结果表明,PA6/MMT纳米复合材料的力学性能较PA6有较大提高,含4%MMT的PA6/MMT纳米复合材料的拉伸弹性模量从2697 MPa提高到3299 MPa,拉伸强度从63.6 MPa提高到77.8MPa;起始分解温度和最大失重温度均高于纯PA6;PA6/MMT纳米复合材料中PA6的结晶温度和结晶速率提高。     

Shear flow effect on the crystalline forms in polyamide 6/montmorillonite nanocomposites

The influence of shear flow on the crystallization of polyamide 6/MMT nanocomposites prepared by melt intercalation process was investigated in detail by differential scanning calorimetry. The melted nanocomposites were controlled sheared in the steady and oscillatory shear flow, using a rotational rheometer, and cooled in an inert atmosphere. The effects of shear rate or frequency, clay concentration, and crystallization conditions on PA 6 crystalline phase development were studied. As expected, an opposite impact of shearing on γ‐phase formation in the nanocomposites and neat matrix was found. Surprisingly, a critical shear frequency for the onset of γ‐form crystallinity formation in the nanocomposites, increasing with the filler content as a consequence of polymer chains confinement within oriented clay platelets was found. At higher shear frequencies, the proportion of γ‐form in the nanocomposites increased dramatically with the clay concentration and reached 30–40%. The shear flow effects were influenced by cooling conditions, and more significant effect for rapidly cooled samples was observed. The isothermal crystallization at the solidification temperature 205°C reduced the γ‐form content. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Effects of swelling agents on the crystallization behavior and mechanical properties of polyamide 6/clay nanocomposites

Montomorillonite was organically modified with three different swelling agents: n‐dodecylamine, 12‐aminolauric acid, and 1,12‐diaminodecane. These organoclays and polyamide 6 (PA6) were blended in a formic acid solution. X‐ray diffraction analysis showed that the clay still retained its layer structure in the PA6/clay nanocomposite. Consequently, these materials were intercalated nanocomposites. The effects of the swelling agent and organoclay content on the crystallization behavior of the PA6/clay nanocomposites were studied with differential scanning calorimetry. The results showed that the position and width of the exothermic peak of the PA6/clay nanocomposites were changed during the nonisothermal crystallization process. The clay behaved as a nucleating agent and enhanced the crystallization rate of PA6.The crystallinity of PA6 decreased with an increasing clay content. Different swelling agents also affected the crystallization behavior of PA6. The effects of the type and content of the swelling agent on the tensile and flexural properties of PA6/clay nanocomposites were also investigated. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1686–1693, 2003     

Comparing the Continuous Chaotic and Shear Mixing-Induced Morphology Development of Polyblend and its Nanocomposites

Continuous chaotic and shear mixing-induced morphology development of 60/40 w/w polypropylene/polyamide 6 (PP/PA6) blend and its nanocomposite with 5 wt% clay was investigated. PP and PP nanocomposite were mixed with PA6 in a single-screw extruder, respectively. Two screw geometries were used to induce chaotic and shear mixing, respectively. It was demonstrated that for PP/PA6 blend, the PA6 domains were transformed from large particles to short striations and to small droplets finally in shear mixing, whereas morphology of PA6 phase developed from lamellar layers to a partial continuous structure finally in chaotic mixing. For (PP/clay)/PA6 blend nanocomposite, the PA6 domains were deformed gradually from droplets to irregular fibrils in shear mixing and from short layers to thin fibrils in chaotic mixing. The PA6 fibrils formed finally in the latter were much thinner and uniform than those in the former. The dynamic storage moduli of samples prepared in both shear and chaotic mixing with these PA6 fibrils presented a solid-like response at lower frequencies. Moreover, the clay platelets dispersed initially in the PP phase migrated into PA6 phase finally in both shear and chaotic mixing and the exfoliation of clay platelets in PA6 phase was obviously improved in the latter.     

The friction and wear properties of clay filled PA66

Polyamide 66(PA66)/clay nanocomposites were prepared by direct melt compounding. The mechanical and tribological properties were evaluated. It was found that addition of clay into PA66 increased the bending strength and microhardness of PA66. And also, the incorporation of clay can reduce the friction coefficient of PA66. The nanocomposites which have the mass fraction less than 5% show less wear rate compared with neat PA66. High fraction of clay can cause severe agglomerated abrasives. The differences in the friction and wear behaviors of PA66 and PA66/clay nanocomposites are attributed to the differences in their surface morphologies, transfer film characteristic. The agglomerated abrasives on the worn surface contribute to the increase of wear rate of nanocomposites of higher mass fraction clay. The friction and wear behaviors of PA66 and its nanocomposites under high temperature exhibit similar tendency with those under 25°C. POLYM. ENG. SCI., 48:203–209, 2008. © 2007 Society of Plastics Engineers     

Effect of clay addition on the morphology and thermal behavior of polyamide 6

The nanostructure, morphology, and thermal properties of polyamide 6 (PA6)/clay nanocomposites were studied with X‐ray scattering, differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). The wide‐angle X‐ray diffraction (WAXD) and TEM results indicate that the nanoclay platelets were exfoliated throughout the PA6 matrix. The crystallization behavior of PA6 was significantly influenced by the addition of clay to the polymer matrix. A clay‐induced crystal transformation from the α phase to the γ phase for PA6 was confirmed by WAXD and DSC; that is, the formation of γ‐form crystals was strongly enhanced by the presence of clay. With various clay concentrations, the degree of crystallinity and crystalline morphology (e.g., spherulite size, lamellar thickness, and long period) of PA6 and the nanocomposites changed dramatically, as evidenced by TEM and small‐angle X‐ray scattering results. The thermal behavior of the nanocomposites was investigated with DSC and compared with that of neat PA6. The possible origins of a new clay‐induced endothermic peak at high temperature are discussed, and a model is proposed to explain the complex melting behavior of the PA6/clay nanocomposites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1191–1199, 2007     

Crystal structures and their effects on the properties of polyamide 12/clay and polyamide 6–polyamide 66/clay nanocomposites

Both polyamide 12 (PA 12)/clay and polyamide 6–polyamide 66 copolymer (PA 6/6,6)/clay nanocomposites were prepared by melt intercalation. The incorporation of 4–5 wt % modified clay largely increased the strength, modulus, heat distortion temperature (HDT), and permeation resistance to methanol of the polyamides but decreased the notched impact strength. Incorporation of the clay decreased the melt viscosities of both the PA 12 and PA 6/6,6 nanocomposites. Incorporation of the clay increased the crystallinity of PA 6/6,6 but had little effect on that of PA 12, which explained why the clay obviously increased the glass‐transition temperature of PA 6/6,6 but hardly had any effect on that of PA 12. The dispersion and orientation of both the clay and the polyamide crystals were studied with transmission electron microscopy, scanning electronic microscopy, and X‐ray diffraction. The clay was exfoliated into single layers in the nanocomposites, and the exfoliated clay layers had a preferred orientation parallel to the melt flow direction. Lamellar crystals but not spherulites were initiated on the exfoliated clay surfaces, which were much more compact and orderly than spherulites, and had the same orientation with that of the clay layers. The increase in the mechanical properties, HDT, and permeation resistance was attributed to the orientated exfoliated clay layers and the lamellar crystals. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4782–4794, 2006     

Free volume sizes in intercalated polyamide 6/clay nanocomposites

The effect of incorporating modified clay into a polyamide 6 (PA6) matrix, on the free volume cavity sizes and the thermal and viscoelastic properties of the resulting nanocomposite, was studied with positron annihilation lifetime spectroscopy, differential scanning calorimetry and dynamic mechanical analysis. At low concentrations of clay the fraction of PA6 crystals melting close to 212 °C was increased, while the fraction of the α-form PA6 crystals, melting close to 222 °C, was reduced. At higher concentrations of clay, a crystal phase with increased thermal stability emerged. Addition of more than 19 wt% clay caused a reduction of the heat of fusion of PA6. An unexpected reduction of the ΔC_p at the glass transition, contradicting the measured reduction of the heat of fusion, was detected, indicating an altered mobility in the non-crystalline regions. The viscoelastic response of PA6/clay nanocomposites, as compared to unfilled PA6, pointed towards a changed mobility in the non-crystalline regions. At high concentrations of clay (>19 wt%) an increase of the free volume cavity diameter was observed, indicating a lower chain packing efficiency in the PA6/clay nanocomposites. The increased free volume sizes were present both above and below the glass transition temperature of PA6.     

Free‐volume hole properties of two kinds thermoplastic nanocomposites based on polymer blends probed by positron annihilation lifetime spectroscopy

Two type of nanocomposites—an immiscible blend, high density polyethylene/polyamide 6 (HDPE/PA‐6) with organomodified clay, and a compatibilized blend, high density polyethylene grafted with acrylic acid/PA‐6 (PEAA/PA‐6) with organomodified clay—were prepared via melt compounding. X‐ray diffraction and transmission electron microscopy results revealed that the clay was intercalated and partially exfoliated. Positron annihilation lifetime spectroscopy has been utilized to investigate the free‐volume hole properties of two type of nanocomposites. The results show a negative deviation of free‐volume size in PEAA/PA‐6 blend, and a positive deviation in HDPE/PA‐6 blend, and I₃ has a greater negative deviation in compatibilized blend than in immiscible blend due to interaction between dissimilar chains. For nanocomposites based on polymer blends, in immiscible HDPE/PA‐6/organomodified clay system, the variation of free‐volume size with clay content is not obvious and the free‐volume concentration and fraction decreased. While in the case of compatibilized PEAA/PA‐6/organomodified clay nanocomposites, complicated variation of free‐volume properties due to interactions between two phases and organomodified clay was observed. And the interaction parameter β shows the interactions between polymers and organomodified clay. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2463–2469, 2006     

On the structure‐properties relationship in montmorillonite‐filled polyamide 6 nanocomposites

Polyamide 6/montmorillonite (MMT) nanocomposites were prepared by melt compounding method comprising 1–7.5 wt % of Nanomer I.24 TL or 5 and 10 wt % of Cloisite 15A organically modified nanoclays. The composite samples were characterized by synchrotron X‐ray, thermal and FT‐IR spectroscopy methods looking for changes in the micro‐ and nanostructure of both PA6 matrix and MMT reinforcement as a function of the clay content and type. These data were discussed in conjunction with the mechanical properties of the respective nanocomposites. Generally, the Young's modulus was found to increase proportionally to the clay content being the highest in samples with strong aggregation of MMT at micron length scale. The tensile strength passed through a maximum at 2.5 wt % clay load presenting a homogeneous microstructure with almost no agglomeration. Increasing the amount of MMT produced less crystalline PA6 matrices, richer in γ‐PA6 polymorph and resulted in larger long spacings of PA6 due to expansion of both crystalline and amorphous domains. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Preparation and Combustion Properties of Flame Retardant Nylon 6/Montmorillonite Nanocomposite

Flame retardant Nylon 6 (PA6)/montmorillonite (MMT) nanocomposites have been prepared using direct melt intercalation technique by blending PA6, organophilic clay and conventional fire retardants, such as the melamine cyanurate (MCA) and the combination of decabromodiphenyl oxide (DB) and antimony oxide (AO). Their morphology and combustion properties are characterized by XRD, transmission electron microscopy (TEM), UL‐94 test and Cone Calorimeter experiments. The flame retardant nanocomposites with MCA or DB and AO show lower heat release rate (HRR) peak compared to that of conventional flame retardant PA6. Meanwhile, the synergetic effect was studied between clay and DB‐AO.

TEM of PA‐n nanocomposite.