聚丙烯/纳米CaCO3复合材料的结晶行为研究

用超重力法制备的纳米CaCO3和PP熔融共混制备了PP/CaCO3复合材料,并对PP/CaCO3复合材料的结晶行为进行了详细研究。差示扫描量热分析表明,纳米CaCO3粒子的加入加快了PP的结晶速率,缩短了半结晶时间,130℃时含15份纳米CaCO3的PP/CaCO3复合材料的半结晶时间比纯PP的减少了8.92 min;结晶度有轻微下降,结晶温度为126.5 ℃时纯PP的结晶度为44.33 %,含15份纳米CaCO3的PP/CaCO3复合材料的结晶度为35.9 %。动力学研究数据表明,等温结晶过程符合Avrami方程,PP/CaCO3的n和k值都大于纯PP的;利用偏光显微镜观察了PP/CaCO3复合材料的结晶形貌及结晶生长过程,纳米CaCO3粒子的加入使球晶数量明显增多,意味着CaCO3起到了结晶成核剂的作用。     

稀土β晶成核剂改性nano-CaCO_3/PP复合材料的结晶行为

讨论了稀土β晶成核剂(WBGⅡ)对nano-CaCO3/PP复合材料结晶性能的影响,并借助WAXD、DSC及PLM对PP、nano-CaCO3/PP和WBGⅡ/nano-CaCO3/PP复合材料的结晶行为及晶体形态进行了表征。结果表明:加入少量WBGⅡ后,聚丙烯基复合材料的晶型和球晶形态发生明显变化,提高了材料的起始结晶温度和结晶温度,降低了材料的过冷度,半结晶期延长。     

Effects of halloysite nanotubes on kinetics and activation energy of non-isothermal crystallization of polypropylene

Halloysite nanotubes (HNTs), a kind of naturally occurring silicates possessing typical fibular structure, were introduced to fabricate polypropylene (PP)/HNTs nanocomposites. The non-isothermal crystallization behaviors were investigated by differential scanning calorimetry (DSC) method according to different treatments. The results suggest, with the inclusion of HNTs in PP matrix, the nanocomposites crystallize at higher temperature regime, which are correlated with the heterogeneous nucleating effects of HNTs during the crystallization process of PP. The kinetics studies of crystallization show that PP nanocomposites possess faster crystallization process and higher activation energy due to the nucleating effect and hindrance effect of HNTs to the motion of PP chains. The polarized light microscopy (PLM) observations further show that HNTs serve as nucleation sites and accelerate the crystallization process.     

Ultrasonic oscillations induced morphology and property development of polypropylene/montmorillonite nanocomposites

Polypropylene/montmorillonite nanocomposites (PPCNs) with 3% organophilic montmorillonite (OMMT) content were prepared via ultrasonic extrusion. The objective of present study was to investigate the effects of ultrasonic oscillations in processing on the morphology and property development of PPCNs. XRD and TEM results confirmed the intercalated structure of OMMT in conventional nanocomposite (without ultrasonic treatment) and ultrasonicated nanocomposite, but ultrasonic oscillations could make silicate layers finely dispersed and a little exfoliated. According to SEM, the OMMT particles were evenly and finely dispersed in the ultrasonicated nanocomposite via ultrasonic oscillations, and the aggregation size of clay particles was about 100 nm, which is less than that in conventional nanocomposite. The crystalline dimension, crystalline morphology and the growth rate of crystallization in PPCNs were investigated by DSC and PLM, it was found that the OMMT particles and ultrasonic oscillations played an important role in the nucleation rate, crystallization temperature and spherulite size of PP matrix in nanocomposites. Compared with conventional nanocomposite, the mechanical properties of the ultrasonicated nanocomposite increased due to the improved dispersion of OMMT and diminished spherulite size. The thermal stability and the rheological behavior of PP and its nanocomposites were both studied by thermogravimetry and high pressure rheometer, respectively.     

Morphology and Properties of Modified Polypropylene for Extruded Film Applications

Abstract

Change in crystallization morphology of polypropylene (PP) on blending with high density polyethylene (HDPE), and on incorporation of cross-linking agent, trimethyl propane triacrylate (TMPTA), and nucleating agent, aluminium dibenzoate (DBS), was studied using differential scanning calorimetry (DSC), polarizing light microscopy (PLM), and small angle light scattering (SALS). In all, three blend systems: PP-HDPE, PP-HDPE-TMPTA, and PP-HDPE-DBS were developed. Analysis of crystallization exotherm, PLM, and SALS studies indicate that DBS is an effective nucleating agent for PPHDPE system and results in appreciable reduction in spherulite size and increase in percent crystallinity, while on cross-linking there is reduction in both percentage crystallinity and spherulite size. Improvement in overall mechanical properties is observed in all the systems studied. As it is desirable to work with PP having a high degree of crystallinity, low spherulite size and low melt flow index (MFI) for oriented film applications, PP-HDPE-DBS system with a low MFI grade HDPE is found to be most suitable.     

Influence of poly(ethylene glycol)/montmorillonite hybrids on the rheological behaviors and mechanical properties of polypropylene

The effects of poly(ethylene glycol) (PEG)/montmorillonite (MMT) hybrids on the phase morphology, rheological behaviors and mechanical properties of polypropylene (PP) were investigated. The analysis of transmission electron microscopy (TEM) and wide-angle X-ray diffraction (WAXD) indicated that the PEG modified montmorillonite was intercalated and well dispersed into PP matrix. It was found that the addition of the PEG/MMT hybrids in PP matrix lead to a significant reduction of melt viscosity and enhancement in izod-notched impact strength and elongation at break, except that the tensile strength was without much obvious change. A quantitative analysis indicated that MMT was intercalated by PEG, which was responsible for the melt viscosity reduction of PP matrix. Differential scanning calorimetry (DSC) analysis indicated that the addition of PEG/MMT hybrids induced the formation of β-crystal of PP. Polarized light micrographs (PLM) analysis indicated that the dispersed MMT, which acted as a nucleating agent, lowered the spherulite dimension and increased the spherulite number, resulting in high izod-notched impact strength and elongation at break.     

Morphologies,crystallization, and mechanical properties of PLA-based nanocomposites: Synergistic effects of PEG/HNTs

In this study, the compounding modifier poly(ethylene glycol)/halloysite nanotubes (PEG/HNTs) was prepared by supersonic vibration and dynamic vacuuming. A series of poly(lactic acid) (PLA)/PEG and PLA/PEG/HNT composites were fabricated using a twin-screw extruder. Fourier transform infrared spectroscopy indicated that the hybrid between PEG and HNTs had no evident chemical interaction via supersonic vibration and dynamic vacuuming. The dispersed morphology of the compounding modifier in the PLA matrix was tested by high-resolution scanning electronic microscopy and transmission electron microscopy. The results showed that the low content of PEG/HNTs presented a good dispersion morphology. The binding energy of the PLA-based composites was studied through contact angle measurements. The results showed that PEG and PEG/HNTs can decrease the water contact angle of PLA, and that the binding energy between PEG and HNTs is higher than that of PLA/HNTs, which leads to more location of HNTs in the PEG phase. The crystallization behavior of PLA-based composites was examined by wide-angle X-ray diffraction and differential scanning calorimetry. The results suggested that the addition of PEG and PEG/HNTs effectively enhanced the crystallization of PLA and that the diffraction peak intensity of the PLA-based composites reached a maximum when the content of PEG/HNTs was 1.2 wt %. The spherulite morphology indicated that the addition of PEG resulted in perfect spherulites. The mechanical properties of PLA-based composites were analyzed with a universal testing machine and impact tester, which confirmed that the tensile strength and impact strength of the PLA-based composites increased slightly when the content of the PEG/HNT modifier was 1.2 wt %, while the tensile modulus of the PLA-based composites increased distinctly. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47385.     

Effect of sepiolite on the crystallization behavior of biodegradable poly(lactic acid) as an efficient nucleating agent

To enhance the crystallization kinetics of poly(lactic acid) (PLA), fibrous sepiolite was explored for nucleating the crystallization of PLA. PLA/sepiolite nanocomposites were prepared via the melt‐extrusion method. The effect of sepiolite on the crystallization behavior, spherulite growth and crystal structure of PLA were investigated by means of differential scanning calorimetry (DSC), polarized optical microscope (POM), wide angle X‐ray diffraction (WAXD), Fourier transform infrared (FTIR), and scanning election microscope (SEM). On the basis of DSC and POM results, the overall crystallization kinetics of PLA/sepiolite nanocomposites were significantly enhanced leading to higher crystallinity and nucleation density, faster spherulite growth rate (G) and lower crystallization half‐time (t_1/2) compared with the neat PLA. Under non‐isothermal conditions, the PLA blend comprising 1.0 wt% of sepiolite still revealed two crystallization peaks upon cooling at a rate of 35°C/min. Above phenomena strongly suggested that sepiolite was an effective nucleating agent for PLA. FTIR and WAXD analyses confirmed that the crystal structure of PLA matrix was the most common α‐form. SEM micrographics illustrated the fine three‐dimensional spherulite structures with the lath‐shape lamellae regularly arranged in radial directions. POLYM. ENG. SCI., 55:1104–1112, 2015. © 2014 Society of Plastics Engineers     

Crystallization behaviors and mechanical performance of polypropylene/tetrapod‐shaped zinc oxide whisker composites

Polypropylene (PP)/tetrapod‐shaped zinc oxide whisker (T‐ZnOw) composites are prepared via a melt‐mixing method in combination with a Haake rheometer. Differential scanning calorimetery (DSC) is used to investigate the nonisothermal and isothermal crystallization behaviors of the composites. Crystalline morphology is observed using hot‐stage optical microscopy, and the mechanical performance of the composites is investigated. Results indicate that T‐ZnOw has no heterogeneous nucleation effect on PP; in fact, it retards the growth of the crystal. Filled T‐ZnOw in PP matrix decreases the peak crystallization and melting temperatures of PP. T‐ZnOw shows either a reinforcing or toughening effect on the PP matrix at very lower weight ratios. These effects, however, decline with increasing T‐ZnOw contents because the size of the spherulitic crystals becomes bigger. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation and crystallization of poly(ethylene terephthalate)/SiO2 nanocomposites by in‐situ polymerization

Poly(ethylene terephthalate) (PET)/SiO₂ nanocomposites were prepared by in situ polymerization. The dispersion and crystallization behaviors of PET/SiO₂ nanocomposites were characterized by means of transmission electron microscope (TEM), differential scanning calorimeter (DSC), and polarizing light microscope (PLM). TEM measurements show that SiO₂ nanoparticles were well dispersed in the PET matrix at a size of 10–20 nm. The results of DSC and PLM, such as melt‐crystalline temperature, half‐time of crystallization and crystallization kinetic constant, suggest that SiO₂ nanoparticles exhibited strong nucleating effects. It was found that SiO₂ nanoparticles could effectively promote the nucleation and crystallization of PET, which may be due to reducing the specific surface free energy for nuclei formation during crystallization and consequently increase the crystallization rate. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 655–662, 2006     

埃洛石纳米管对聚酰胺66/热致液晶原位复合材料性能及微观形态的影响

采用熔融共混方法制备了埃洛石纳米管（HNTs）／聚酰胺66（PA66）／热致液晶聚合物（TLCP）原位混杂复合材料,研究了其结晶性能、动态力学性能及微观形态,并提出了相对结晶度的概念。差示扫描量热法分析（DSC）表明：HNTs能促进PA66的结晶并提高晶体的完善程度;随着HNTs含量的增加,体系的相对结晶度逐渐提高;动态力学性能分析（DMA）表明：复合材料的储能模量及损耗模量均随着HNTs含量的增加而显著升高当HNTs含量为40 ％（质量分数,下同）时,复合材料的储能模量及损耗模量分别提高了188％、190 ％;扫描电子显微镜（SEM）显示,TLCP及HNTs均能在基体中均匀分散,且TCLP能较好地沿纤维轴方向取向、成纤。     

Ethylene–propylene‐diene terpolymer/halloysite nanocomposites: Thermal,mechanical properties,and foam processing

Ethylene–propylene‐diene terpolymer (EPDM)/halloysite nanotube (HNT) nanocomposites were prepared by melt mixing in an internal mixer using a commercially available maleated semicrystalline EPDM and HNT. Transmission electron microscopy analysis of the EPDM/HNT composites revealed that the HNTs are uniformly dispersed at a nanometer scale in the matrix. Differential scanning calorimeter studies indicated that the HNT caused an increase in the nonisothermal crystallization temperature of the EPDM. Tensile and dynamic mechanical analysis exhibited that a small amount of the HNTs effectively enhanced the stiffness of the EPDM without adversely affecting its elongation‐at‐break. The EPDM/HNT nanocomposites were used to produce foams by using a batch process in an autoclave, with supercritical carbon dioxide as a foaming agent. The nanocomposite foams showed a smaller cell size and higher cell density as compared to the neat EPDM foam, and the nanocomposite with 10 phr HNT produced a microcellular foam with average cell size as small as 7.8 μm and cell density as high as 1.5 × 10¹⁰ cell/cm³. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40307.     

α成核剂对聚丙烯结晶、透光率与力学性能的影响

用偏光显微镜对聚丙(烯PP)结晶形态及球晶尺寸进行了表征,并通过差示扫描量热(法DSC)分析了PP熔融及结晶过程的结晶度、熔融峰值、结晶峰值、结晶峰宽度。结果表明:随α成核剂用量的增加,PP的透光率、拉伸强度及弹性模量增强,冲击强度和断裂伸长率下降。     

PP/PP-g-MAH/废PCB粉复合材料非等温结晶动力学研究

利用差示扫描量热法结合Avrami方程研究了聚丙烯（PP）、聚丙烯/聚丙烯接枝马来酸酐/废印刷电路板非金属粉复合材料（PP/PP-g-MAH/废PCB粉）的非等温结晶动力学行为,根据Avrami方程的Jeziorny法和莫志深法对数据进行处理。结果表明,废PCB粉在PP基体中起到异相成核作用,提高了PP的结晶温度,使其成核速率加快,晶粒分布变窄,结晶速率增大,但当废PCB粉含量过多时,复合材料体系黏度会增大,使PP链段扩散迁移并进行规整有序排列的速度受到影响,导致结晶速率下降。     

Structure and properties of polypropylene composites filled with magnesium hydroxide

Silane and silicone oil modified superfine magnesium hydroxide (MH) was filled into polypropylene (PP) as a flame retardant. The PP and flame‐retarded PP composites were studied for their mechanical properties and rheological behaviors by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), limiting oxygen index (LOI), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The results showed that the addition of MH improved flame retardancy of PP/MH composites, but seriously deteriorated mechanical properties of the composites. Surface treatment of MH could significantly improve tensile and impact strength of PP/MH composite because of its enhanced interfacial adhesion between MH and PP matrix. DSC results showed that MH had heterogeneous nucleation effect on PP. Surface treatment of MH weakened its heterogeneous nucleation effect. POM results showed that the dispersion of MH particles played an important role in the crystalline morphology and spherulite size of PP crystals. TGA indicated that MH greatly enhanced the thermal stability of PP. The introduction of treatment agent further improved the thermal oxidative stability of the composite. According to LOI, silane‐treated MH greatly enhanced flame retardancy of PP/MH composites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4943–4951, 2006     

PA12对聚甲醛成核作用的研究

用示差扫描量热分析法、偏光显微镜法研究尼龙 12对POM的成核作用 ,并对力学性能及线膨胀系数进行测定。结果表明 ,PA12的加入 ,使POM的结晶温度升高 ,球晶细化 ,线膨胀系数降低 ,缺口冲击强度随PA12用量的增加出现峰值 ,采用母料法分散工艺使PA12分散更为均匀 ,成核效果更为显著。     

PP/纳米TiO2复合材料的晶体形貌和非等温结晶行为

用熔融共混法制备了聚丙烯（PP）/纳米TiO2复合材料,用透射电子显微镜、偏光显微镜、差示扫描量热仪和广角X射线衍射仪对其纳米粒子分散性、晶体形貌和非等温结晶行为进行了研究。结果表明,纳米TiO2以纳米级尺寸均匀分散于PP基体中;130 ℃冷却和室温冷却时,PP/纳米TiO2复合材料的晶粒比纯PP的细,并且随着纳米TiO2含量的增加,PP/纳米TiO2复合材料的晶粒尺寸先减小后增大,纳米TiO2含量为2 %（质量分数,下同）时晶粒最细;纳米TiO2对PP结晶具有加速作用;复合材料的结晶活化能高于纯PP的,并且纳米TiO2含量多且均匀时复合材料结晶活化能高;纳米TiO2含量较少时可诱导较多的β晶生成,当纳米TiO2含量为1 %时,复合材料中β晶含量达到25.2 %。     

Melting and crystallization behaviors,morphology, and mechanical properties of β‐polypropylene/polypropylene‐graft‐maleic anhydride/calcium sulfate whisker composites

The melting and crystallization behaviors, morphology, and mechanical properties of polypropylene (PP)/surface‐treated calcium sulfate (CaSO₄) whisker (T‐CSW), β‐PP/T‐CSW, and β‐PP/polypropylene‐graft‐maleic anhydride (PP‐g‐MAH)/T‐CSW composites had been investigated via differential scanning calorimetry (DSC), wide angle X‐ray diffraction (WAXD), polarized light microscopy (PLM), scanning electron microscopy (SEM), and mechanical tests. We found that T‐CSW was an α‐nucleating agent and increased the crystallization temperatures of PP, but PP‐g‐MAH and high loadings of T‐CSW had weakly negative effects on the crystallization rates of PP. The T‐CSW restrained the formation of β‐spherulites, and the spherulitic size decreased in the composites. PP‐g‐MAH improved the compatibility and adhesion between T‐CSW and the matrix. The notched impact strength was improved, and the tensile strength was enhanced at low levels of T‐CSW, while the flexural modulus was weakened for β‐PP/T‐CSW and β‐PP/PP‐g‐MAH/T‐CSW composites versus PP/T‐CSW composites. POLYM. COMPOS., 37:2121–2132, 2016. © 2015 Society of Plastics Engineers     

IPP/Nano-CaCO_3复合材料的制备及其结晶行为的研究

通过熔融共混,制备了等规聚丙烯(iPP)/纳米碳酸钙(nano-CaCO3)复合材料,研究了不同剪切环境下nano-CaCO3粒子在聚丙烯(PP)基体中的分散性能及其对基体熔融过程的影响,并利用广角X射线散射仪(WAXS)、差示扫描量热仪(DSC)、偏光显微镜(PLM)、扫描电镜(SEM)考察了该复合材料的结晶行为。结果表明:在剪切环境中,nano-CaCO3粒子与基体的摩擦、碰撞几率增加;随着nano-CaCO3用量的增加,体系剪切热升高,加快了基体熔融的速度,并改善了nano-CaCO3的分散效果。当nano-CaCO3用量低于3%时,其在PP基体中起到成核剂的作用,提高了PP的结晶度,并诱导β型晶体的生成;当其用量超过3%时,nano-CaCO3在基体中的分散效果降低,导致粒子团聚,对基体的成核作用降低,进而降低了复合材料的结晶度,并且削弱了粒子对基体的诱导形成β型晶体的能力。     

Micro- and nano-structure in polypropylene/clay nanocomposites

Polypropylene (PP)/clay nanocomposites prepared by melt blending using different clays and coupling agents based on maleic anhydride-grafted PP (MA-PP) were studied. Clay dispersion using field emission gun scanning electron microscope (FEG-SEM) and transmission electron microscopy (TEM), and PP matrix morphology were characterized. Clay dispersion was improved in the presence of MA-PP, as shown by the higher particles surface density (number of particles/mm²) at all micro-, sub-micro- and nano-levels. The PP spherulite diameter was affected by both the presence of MA-PP and clay dispersion. Clay intercalation, characterized by both complementary X-ray diffraction (XRD) and TEM, was greatly influenced by the characteristics of MA-PP. The use of low molecular weight (M_w) MA-PP led to a good and uniform intercalation but with no further possibility to exfoliation. The use of higher M_w MA-PP led to a heterogeneous intercalation with signs of exfoliation. The crystallization behavior of nanocomposites was studied by differential scanning calorimetry (DSC). When fine clay dispersion was achieved with MA-PP, clay-nucleating effect was limited and lower crystallization temperature and rates were observed. It was also shown by wide angle X-ray diffraction (WAXD) that clay induced some orientation of α-phase PP crystallites.