Isothermal crystallization kinetics of polypropylene in melt‐mixed composites of polypropylene and multi‐walled carbon nanotubes

The isothermal crystallization behaviour of the polypropylene (PP) phase in PP/multi‐walled carbon nanotubes (MWCNTs) composites has been investigated via differential scanning calorimetric analysis, which showed the influence of the varying dispersion level of MWCNTs in the respective PP matrix. PP/MWCNTs composites were prepared via melt‐blending technique, wherein two different grades of MWCNTs of varying average “agglomerate” size and varying entanglements (N‐MWCNTs and D‐MWCNTs) were utilized. Furthermore, the influence of melt‐viscosity of the PP phase was investigated on the crystallization kinetics of the PP/MWCNTs composites. Heterogeneous nucleation ability of MWCNTs has resulted in a decrease in half time of crystallization (t _1/2) from ～14 min for pure PP to ～6 min for PP/N‐MWCNTs and ～11 min for PP/D‐MWCNTs composites at 1 wt% of MWCNTs at 132 °C. Overall rate of crystallization (k) has significantly increased to 4.9 × 10^?2 min^?1 for PP/N‐MWCNTs composite as compared with 6.2 × 10^?3 min^?1 for PP/D‐MWCNTs composite at 0.5 wt% of MWCNTs at 132 °C. Moreover, the effect of a novel organic modifier, Li‐salt of 6‐amino hexanoic acid along with a compatibilizer (PP‐g‐MA) has also been investigated on the crystallization kinetics of the PP phase in PP/MWCNTs composites. POLYM. ENG. SCI., 57:1136–1146, 2017. © 2017 Society of Plastics Engineers     

Effect of compatibilizer on morphology,thermal, and rheological properties of polypropylene/functionalized multi‐walled carbon nanotubes composite

Multi‐walled carbon nanotubes (MWCNTs) filled polypropylene (PP) composites were prepared by a corotating intermeshing twin screw extruder. To improve the dispersion of MWCNTs, the surface of MWCNT was modified with 1,10‐diaminodecane, and maleic anhydride grafted polypropylene (MA‐g‐PP) was used as a compatibilizer. Micrographs of well dispersed functionalized MWCNTs (diamine‐MWCNT) were observed due to the reaction between MA‐g‐PP and diamine‐MWCNT in PP/MA‐g‐PP/diamine‐MWCNTs composites. The different behaviors in crystallization and melting temperatures of PP/MA‐g‐PP/diamine‐MWCNTs composite were observed compared to PP and PP/neat‐MWCNT. Especially, the decomposition temperature of the composite was increased by 50°C compared to PP. PP/MA‐g‐PP/diamine‐MWCNTs composite showed the highest complex viscosity. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Ternary polymer blends of polyamide 6, polypropylene,and acrylonitrile‐butadiene‐styrene: Influence of multiwalled carbon nanotubes on phase morphology,electrical conductivity,and crystallization

Ternary polymer blends of 80/10/10 (wt/wt/wt) polyamide6 (PA6)/polypropylene (PP)/acrylonitrile‐butadiene‐styrene (ABS), PP/PA6/ABS, and ABS/PP/PA6 were prepared in the presence of multiwalled carbon nanotubes (MWCNTs) by melt‐mixing technique to investigate the influence of MWCNTs on the phase morphology, electrical conductivity, and the crystallization behavior of the PP and PA6 phases in the respective blends. Morphological analysis showed the “core–shell”‐type morphology in 80/10/10 PA6/PP/ABS and 80/10/10 PP/PA6/ABS blends, which was found to be unaltered in the presence of MWCNTs. However, MWCNTs exhibited “compatibilization‐like” action, which was manifested in a reduction of average droplet size of the dispersed phase/s. In contrast, a separately dispersed morphology has been found in the case of 80/10/10 ABS/PP/PA6 blends in which both the phases (PP and PA6) were dispersed separately in the ABS matrix. The electrical percolation threshold for 80/10/10 PA6/PP/ABS and 80/10/10 PP/PA6/ABS ternary polymer blends was found between 3–4 and 2–3 wt% of MWCNTs, respectively, whereas 80/10/10 ABS/PP/PA6 blends showed electrically insulating behavior even at 5 wt% of MWCNTs. Nonisothermal crystallization studies could detect the presence of MWCNTs in the PA6 and the PP phases. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Effects of hard and soft components on the structure formation,crystallization behavior and mechanical properties of electrospun poly(l-lactic acid) nanofibers

The effects of multi-wall carbon nanotubes (MWCNTs) and poly(ethylene oxide) (PEO) on the structure formation, morphology, crystallization behavior and mechanical property of electrospun poly (l-lactic acid) (PLLA) nanofiber mats were investigated by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), differential scanning calorimeter (DSC) and mechanical test. If incorporate hard filler, MWCNTs into electrospun PLLA nanofiber, the crystallinity, chain orientation, and crystallization behaviors were almost not influenced by the MWCNTs content owing to the MWCNTs mainly acted as impeding the crystal growth and chain diffusion. If incorporate small content of soft and miscible component, PEO (10 wt%) into the electrospun PLLA and PLLA/MWCNTs nanofibers, the crystallinity and crystallization rate of PLLA in nanofibers were obviously enhanced. The synergistic effect of PEO and MWCNTs in PLLA nanofibers was observed during melt-crystallization behaviors of PLLA/MWCNTs fibers. Based on those results, we found that the chain mobility is an important factor to influence the structure formation and crystallization behaviors in the electrospun nanofibers. Our results indicated that the structure and properties of electrospun nanofibers could be optimized by compounding with hard inorganic filler and soft polymer components.     

聚苯硫醚/碳纳米管复合材料的非等温结晶性能

利用双螺杆挤出机制备了纤维用聚苯硫醚/多壁碳纳米管(PPS/MWCNTs)复合材料。通过差示扫描量热法(DSC)研究了不同降温速率下纯PPS以及PPS/MWCNTs复合材料的非等温结晶过程,并运用Ozawa模型进行了非等温结晶动力学分析。结果表明:降温速率对PPS/MWCNTs复合材料的结晶性能有很大的影响,当降温速率为20℃/min时,PPS/MWCNTs复合材料的结晶能力及相对结晶度最大;MWCNTs在PPS结晶过程中起异相成核剂的作用,使PPS/MWCNTs复合材料的结晶温度较纯PPS升高。     

Multiwalled carbon nanotubes‐based polypropylene composites: Influence of interfacial interaction on the crystallization behavior of polypropylene

Composites of polypropylene (PP) and multi‐walled carbon nanotubes (MWCNTs) were prepared via melt‐mixing utilizing Li‐salt of 6‐amino heaxanoic acid (Li‐AHA) modified MWCNTs in the presence of a compatibilizer (polypropylene‐g‐maleic anhydride; PP‐g‐MA). Improved interaction between the anhydride group of PP‐g‐MA and the amine functionality of Li‐AHA was confirmed via FTIR and Raman spectroscopic analysis. A higher glass transition temperature (T_g) of the PP phase has been observed in these composites as compared to pristine MWCNTs‐based composites. The crystallization temperature (T_c) of the PP phase was increased as a function of pristine MWCNTs concentration in PP/MWCNTs composites indicating hetero‐nucleating action of MWCNTs. However, T_c value was decreased in the presence of Li‐AHA modified MWCNTs indicating the adsorbed Li‐AHA on the MWCNTs surface. Moreover, T_c value was higher in the presence of Li‐AHA modified MWCNTs with PP‐g‐MA as compared to that of without PP‐g‐MA, suggesting the desorbed Li‐AHA from the MWCNTs surface due to melt‐interfacial reaction. Further, MWCNTs were extracted by hot vacuum filtration technique from PP/MWCNTs composites containing Li‐AHA and PP‐g‐MA. The isothermal crystallization kinetics showed a variation in crystallization behavior of the PP phase in the corresponding composites as compared to the “extracted MWCNTs.” POLYM. ENG. SCI., 57:183–196, 2017. © 2016 Society of Plastics Engineers     

Improved dielectric performance of polypropylene/multiwalled carbon nanotube nanocomposites by solid‐phase orientation

By means of a die‐drawing technique in the rubbery state, the effect of the orientation of the microstructure on the dielectric properties of polypropylene (PP)/multiwalled carbon nanotube (MWCNT) nanocomposites was examined in this study. The viscoelastic behavior of the PP/MWCNT nanocomposites with MWCNT weight loadings ranging from 0.25 to 5 wt % and the dielectric performance of the stretched PP/MWCNT nanocomposites at different drawing speeds and drawing ratios were studied to obtain insight into the influences of the dispersion and orientation state of the MWCNTs and matrix molecular chains. A viscosity decrease (ca. 30%) of the PP/MWCNT‐0.25 wt % (weight loading) melt was obviously due to the free volume effect. Differential scanning calorimetry (DSC) and wide‐angle X‐ray diffraction were adopted to detect the orientation structure and the variation of crystal morphology of the PP/MWCNTs. Melting plateau regions, which indicated the mixed crystallization morphology for the stretched samples, were found in the DSC patterns instead of a single‐peak for the unstretched samples. We found that the uniaxial stretching process broke the conductive MWCNT networks and consequently increased the orientation of MWCNTs and molecular chains along the tensile force direction; this led to an improvement in the dielectric performance. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42893.     

Rheology,crystallization behavior,and dielectric study on molecular dynamics of polypropylene composites with multiwalled carbon nanotubes and clay

The study is focused on joint effects of two nanofillers in polypropylene (PP) reinforced with 3 wt% organo‐clay (ОC) and 0.1–5 wt% multi‐wall carbon nanotubes (MWCNTs). The composites were produced by extrusion and characterized by rheology, differential scanning calorimeter (DSC), thermally stimulated depolarization currents (TSDC), and dielectric relaxation spectroscopy (DRS). Rheological data indicates а formation of a network structure related to percolation above 1 wt% nanotubes. The flow activation energy (Ea) decreases above the percolation threshold, thus, the presence of clay improves the debundling of MWCNTs and releases the segmental motion of polymer chains. The clay does not affect the crystallization behavior of PP, but the nucleation is enhanced strongly by the MWCNTs. Dielectric measurements reveal that the presence of clay affects the molecular mobility of PP at the amorphous phase. The DSC results imply that around 80°C a cold crystallization process occur in the PP phase which has a significant impact on the dielectric segmental relaxation process and gives rise to the appearance of an additional process, the so called “interfacial” relaxation process. This new relaxation process in the three‐phase composites was attributed to an interfacial polarization process due to blocking of charge carriers at polymer/clay interfaces. POLYM. COMPOS., 37:2756–2769, 2016. © 2015 Society of Plastics Engineers     

几种用于3D打印的高分子材料的性能对比

以2种商用3D打印材料(2种PLA)为主要研究对象,同时选取了2种性能相近的高分子材料(PP、POM),分别对其热性能、结晶性能和流变性能进行了表征。实验结果表明,PLA、PP、POM的分解温度均大于300℃,因此,在3D打印的温度下,均不会发生降解;PLA、PP、POM均属于非牛顿流体,POM的非牛顿指数n值相对较大,更接近牛顿流体;PLA的Eη最大,流动相对困难。在DSC降温测试过程中,当降温速率较低时,PLA才会结晶,但PP和POM结晶相对容易。结晶动力学结果表明,Ozawa理论适用于2#PLA和PP,而并不适用于POM。将1#PLA与3#PP进行3D打印测试,结果表明,3#PP翘曲现象严重,可在PP中添加粉体,满足3D打印需要。     

新型改性烟用聚丙烯性能

本研究采用多组分共混方法,制成A、C、D三种改性母粒,用改性母粒与聚丙烯共混,得到改性烟用聚丙烯.通过X衍射、差热分析、结晶速度、流动性和可纺性的检测分析,说明改性烟用聚丙烯具有很好的流动性和可纺性,其结晶性能和热性能比纯聚丙烯均有明显提高,母粒添加量对改性聚丙烯性能有所影响,最佳添加量为5%.     

Property investigation of polypropylene/multiwall carbon nanotube nanocomposites prepared via in situ polymerization

In this study, polypropylene/carbon nanotube nanocomposites were prepared via in situ polymerization using a bi‐supported Ziegler ? Natta catalytic system. In this system, magnesium ethoxide and multiwall carbon nanotubes (MWCNTs) are jointly used as catalyst supports. SEM images reveal the distribution and quite good dispersion of MWCNTs throughout the polypropylene (PP) matrix. The thermal properties of the samples were examined using DSC and TGA tests. The results show that the crystallization temperature of the nanocomposites significantly increases while the melting point is not markedly affected. In addition, the thermal stability is improved. The melt rheological properties of PP/MWCNT nanocomposites in the linear and nonlinear viscoelastic response regions were studied. An increment of the complex viscosity (η^*), storage modulus (G′) and loss modulus (G′′) and a decrement of the loss factor (tan δ) compared with neat PP are observed. Steady shear flow experiments show an increase in shear viscosity with increasing the MWCNT content. © 2013 Society of Chemical Industry     

添加铝酸盐类长余辉发光粉的夜光塑料性能研究

采用SBS作为载体加工了高含量的发光粉母粒;并将发光母粒添加到聚丙烯中制备了夜光塑料。通过对夜光塑料的熔体质量流动速率、力学性能、发光性能以及夜光粉在塑料中的分散性能进行研究。结果表明用SBS母粒法加工夜光PP的方法是方便可行的;夜光粉在塑料中的分散较好,基本不会影响夜光PP的力学性能;发光粉的含量为 10％的夜光PP发光效果较好;与PS和ABS两种塑料相比,半透明PP的发光效果最好。此外夜光PP的放射性测试结果表明,添加了铝酸盐系列夜光粉的PP不属于放射性材料。     

Crystallization behavior of carbon black‐filled polypropylene and polypropylene/epoxy composites

The crystallization behavior of polypropylene (PP)/carbon black (CB) and PP/epoxy/CB composites was studied with differential scanning calorimetry (DSC). The effects of compatibilizer MAH‐g‐PP and dynamic cure on the crystallization behavior are investigated. The nonisothermal crystallization parameters analysis showed that CB particles in the PP/CB composites and the dispersed epoxy particles in the PP/epoxy composites could act as nucleating agents, accelerating the crystallization of the composites. Morphological studies indicated that the incorporation of CB into PP/epoxy resulted in its preferential localization in the epoxy resin phase, changing the spherical epoxy particles into elongated structure, and thus reduced the nucleation effect of epoxy particles. Addition of MAH‐g‐PP significantly decreased the average diameter of epoxy particles in the PP/epoxy and PP/epoxy/CB composites, promoting the crystallization of PP more effectively. The isothermal crystallization kinetics and thermodynamics of the PP/CB and PP/epoxy/CB composites were studied with the Avrami equation and Hoffman theory, respectively. The Avrami exponent and the crystallization rate of the PP/CB composites were higher than those of PP, and the free energy of chain folding for PP crystallization decreased with increasing CB content. Addition of MAH‐g‐PP into the PP/epoxy and PP/epoxy/CB composites increased the crystallization rate of the composites and decreased the chain folding energy significantly. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 104–118, 2006     

Electrical conductivity and thermal stability of polypropylene containing well-dispersed multi-walled carbon nanotubes disentangled with exfoliated nanoplatelets

The morphology, crystallization behavior, electrical conductivity, and thermal stability of polypropylene (PP) modified with disentangled multi-walled carbon nanotubes (MWCNTs) is reported. Slightly oxidized MWCNT clusters were disentangled in solution by mild sonication in the presence of exfoliated α-zirconium phosphate nanoplatelets. The disentangled MWCNTs were isolated using acid-induced coagulation to precipitate the nanoplatelets, and were subsequently reacted with octadecylamine. The recovered functionalized MWCNTs (F-MWCNTs) are disentangled and easily dispersed in a commercial PP matrix, and serve as more efficient nucleating agents than the untreated MWCNTs. The PP/F-MWCNT composites exhibit an extremely low percolation-like transition in electrical conductivity, which is attributed to the preservation of a random dispersion of disentangled F-MWCNTs upon cooling from the melt. The thermal stability of PP in air is also substantially enhanced at loadings below the percolation threshold due to the tremendous interfacial area between the polymer chains and the free radical scavenging F-MWCNTs. The present approach provides an efficient and potentially scalable route for commercial production of conductive semi-crystalline thermoplastics. The method may be adapted to uniformly disperse MWCNTs in other polymer matrices by appropriate selection of surface functionality.     

不同方法制备的庚二酸钙对改性聚丙烯结晶和熔融行为的影响

分别采用复分解反应法（D-CaPi）、中和反应法（N-CaPi）以及硬脂酸钙与庚二酸共混法（S-CaPi）3种不同方法制备了庚二酸钙,研究了3种庚二酸钙对聚丙烯结晶和熔融行为的影响。利用傅里叶变换红外光谱仪和差示扫描量热仪测试了庚二酸钙的结构及庚二酸钙改性聚丙烯的结晶和熔融行为。结果表明,3种制备方法都可以使庚二酸完全反应得到庚二酸钙;3种庚二酸钙对聚丙烯均有成核能力,其中D-CaPi和N-CaPi使聚丙烯结晶峰温度提高了约4.9 ℃,S-CaPi使聚丙烯结晶峰温度提高了6.5 ℃,同时,S-CaPi对于聚丙烯β晶型得诱导能力明显优于D-CaPi和N-CaPi,可使改性聚丙烯中的β晶型相对含量达到84.5 %。     

Fabrication and characterization of homogeneous composites of polypropylene and multiwalled carbon nanotubes

The polypropylene‐grafted multiwalled carbon nanotubes (PP‐MWCNTs) were produced from the reaction of PP containing the hydroxyl groups and MWCNTs having 2‐bromoisobutyryl groups. The PP‐MWCNTs had a significantly rougher surface than the original MWCNTs. PP‐MWCNTs had PP layers of thickness 10–15 nm on the outer walls of the MWCNTs. PP/PP‐MWCNT composites and PP/MWCNT composites were prepared by solution mixing in o‐xylene. Unlike PP/MWCNT composites, PP‐MWCNTs were homogeneously dispersed in the PP matrix. As a consequence, the thermal stability and conductivity of PP/PP‐MWCNT composites were dramatically improved even if only 1 wt % of PP‐MWNTs was added to the PP matrix. The good miscibility of PP and PP‐MWCNTs plays a critical role in the formation of the homogeneous composites and leads the high thermal stability and conductivity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

一维多壁碳纳米管增强丁基橡胶/聚丙烯热塑性弹性体复合材料的相态结构及热电性能研究

制备一维多壁碳纳米管(MWCNTs)增强丁基橡胶(IIR)/聚丙烯(PP)动态硫化热塑性弹性体(TPV)复合材料,研究IIR/PP用量比(简称橡塑比)对复合材料相态结构、介电性能、导热性能和物理性能的影响。结果表明:复合材料呈现“海-岛”相结构,IIR相以微米级交联颗粒分散在PP相中;MWCNTs主要分散在PP中,随着橡塑比的增大,MWCNTs有少量团聚现象;随着橡塑比的增大,复合材料的交流电导率、介电常数和热导率增大,且橡塑比大于6/4时增速减小;随着橡塑比的减小,复合材料的拉伸强度先增大后减小;当橡塑比为5.5/4.5时,复合材料的物理性能较好。     

动态硫化对三元乙丙橡胶/聚丙烯共混体系等温结晶行为和形态结构的影响

研究了三元乙丙橡胶/聚丙烯(EPDM/PP)共混物和动态硫化EPDM/PP热塑性弹性体(TPV)的等温结晶行为及形态结构,并用Avrami方程对其进行等温结晶动力学分析。结果表明,EPDM/PP共混物和EPDM/PP TPV的等温结晶行为符合Avrami方程,在相同的结晶温度下,TPV比共混物的Avrami指数小,半结晶时间短,结晶速率常数大;EPDM/PP共混物为双连续相结构,而EPDM/PP TPV是以硫化的细小橡胶颗粒为分散相、PP为连续相的"海-岛"结构,橡胶颗粒尺寸约为0.5μm。     

强剪切流动下聚丙烯基复合材料介电性能和结构演变的研究

研究了多壁碳纳米管(MWCNT)、线型低密度聚乙烯(LLDPE)和强剪切流动场对聚丙烯(PP)/MWCNT/LLDPE复合材料的导电性能、结晶性能、力学性能和介电性能的研究。结果表明,PP/MWCNT复合材料随着MWCNT含量的提高,导电性能逐步改善,导电逾渗值约为1.8%,而第二分散相LLDPE的引入使复合材料的导电性能表现出了先降低后升高的现象,并且随着LLDPE含量的增加,MWCNT逐步向LLDPE内部迁移,构成了双连续结构。复合材料经过固态口模拉伸的强剪切流动场之后,随着拉伸速率从10 mm/min增加到300 mm/min的过程中,复合材料的融化温度逐渐向高温方向偏移,表现出了片层厚度增加的现象。复合材料内部分子链取向和纤维结构的形成,能够显著提高复合材料的拉伸强度和介电性能,拉伸强度提高从约50 MPa提高到了约240 MPa,提高了约380%。MWCNT和强剪切流动场的引入也使复合材料的介电常数大幅提升。     

Effect of radical grafting of tetramethylpentadecane and polypropylene on carbon nanotubes' dispersibility in various solvents and polypropylene matrix

Multiwalled carbon nanotubes (MWCNTs) have been functionalized by tetramethylpentadecane (TMP), 1-dodecanethiol (DT) and polypropylene (PP) through radical addition onto MWCNTs' surface using dicumyl peroxide as hydrogen abstractor. Surface functionalized MWCNTs were characterized by Raman, IR spectroscopy, elementary analysis (EA) and thermogravimetric analysis (TGA). We studied the effect of temperature, peroxide concentration and solvent on TMP grafting densities and it was found that this surface treatment lead to a fair solubility in various solvents. TMP-functionalized MWCNTs were also imaged by transmission electronic microscopy showing single long functionalized MWCNTs distinct from the starting pristine bundles. For the first time, PP was then grafted onto MWCNTs through a radical grafting reaction. However, scanning electronic microscopy images of PP-functionalized MWCNTs/PP composites did not show a significant improvement in MWCNTs dispersion within the PP matrix.