Modification of PP by blending with PS and reactive polymers

In this paper a polypropylene (PP) resin with controlled rheology was selected as polymer matrix and modified by melt mixing with polystyrene (PS) which has certain processing compatibility with PP. The effect of the addition of polyperoxide (PPX), peroxide modified PS particles (PS‐PPX), and maleic anhydride (MAH) to the PP/PS blend during melt mixing on the rheological behavior and morphology of the PP/PS blends has been carefully studied.     

Thermal and spectroscopic characterization of polypropylene-carbon nanotube composites

Thermogravimetric (TG) and varied temperature Raman spectroscopic measurements of melt-blended polypropylene composites (PP) with double wall (DWNT) and multi-wall carbon nanotubes (MWNT) revealed that the incorporation of carbon nanotubes into polymer matrix increased the thermal stability comparing to the virgin polypropylene. The characterization of reference nanotubes was also done by Raman microscopy and TG measurements. Varied temperature rheological analysis provided further information about the thermal decomposition of the composites indicating the formation of high strength char in case of MWNT and limited applicability of DWNT at high temperature. The residue of the decomposition of PP-MWNT nanocomposites consists of nanotubes of spectroscopically higher purity comparing to the original one indicating the thermally induced chemical changes in the solid phase.     

The influence of nano‐PS particle on structure evolution and electrical properties of PP/PS

The polypropylene‐g‐polystyrene (PP‐g‐PS) copolymers with different grafting ratios are used as compatibilizers to control the size of polystyrene (PS) particles at nanometer scale in polypropylene (PP) matrix. Then the PP/PS insulating nanocomposites (containing 10 wt % PS calculated from PS and PP‐g‐PS) are manufactured. With the increase in grafting ratio of PP‐g‐PS, the size of PS particle is reduced and the interfacial adhesion is enhanced. Meanwhile, the dielectric properties, DC breakdown strength and volume resistivity are increased with the decreasing of PS particle size. The spherulite size of PP is decreased and the boundary between crystals and amorphous regions is blurred or even disappears due to the presence of PS nanoparticles. This evolution of PP structure is attributed to the serious entanglements of PP and PS molecular chains. Finally, the correlation between morphological structure and electrical properties is ultimately established based on the in‐depth understanding of the molecular chain movement, crystal structure, and phase morphology. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 706–717     

Positive Temperature Coefficient Characteristics of Multi-walled Carbon Nanotube Filled Polyvinylidene Fluoride Nanocomposites

Composites of polyvinylidene fluoride (PVDF) and multi-wall carbon nanotubes (MWNT) were prepared by a melt mixing process. Temperature dependence of electrical properties of the nanocomposites was investigated for composites containing different amounts of MWNT. An obvious positive temperature coefficient was observed. It was found that resistivity of the composites was decreased with increasing MWNT content and the electrical percolation threshold was formed at 3 wt% MWNT, which were caused by the formation of conductive chains in the composites. The mechanism of the positive temperature coefficient behavior of the nanocomposites is discussed. The rheological results showed that the materials experience a fluid–solid transition at the composition of 2 wt%, beyond which a continuous MWNT network forms throughout the matrix leading to a percolated network structure, which further indictes the nanotubes were dispersed uniformaly, in the PVDF matrix.     

聚丙烯/多壁碳纳米管复合材料的热性能和流变性能

用熔融共混法制备了聚丙烯多壁碳纳米管(PP MWNTs)复合材料,TGA研究表明在氮气气氛下碳纳米管显著增加了聚丙烯基体的热稳定性.3wt%MWNTs可使PP热分解起始温度提高44℃.非等温结晶研究表明MWNTs对PP基体的结晶行为没有明显的影响.流变测试结果表明PP MWNTs复合材料的储能模量G′和损耗模量G″随着MWNTs含量增加逐渐增大.1wt%MWNTs的PP聚合物的零剪切粘度最低,5wt%MWNTs的PP聚合物的零剪切粘度最高,PP和3wt%MWNTs的PP纳米聚合物的零剪切粘度居于二者之间,随着频率的增加,剪切稀化作用越来越明显,呈现出假塑性流体行为.含5wt%MWNTs的PP复合材料的体积和表面电阻率与纯PP相比分别下降了9个和4个数量级,表明少量的MWNTs可以显著改变PP的电学性能.     

Comparative analysis of nanocomposites based on polypropylene and different montmorillonites

Nanocomposites of polypropylene (PP) were prepared by melt mixing using maleic anhydride modified polypropylene (PPg) and different organophilic montmorillonites (OMMT). The selected organo-modified clays differ in their initial particle size, amount and type of surfactant and/or their cation-exchange capacity. All composites have 80, 15 and 5 wt% of PP, PPg and OMMT, respectively. The materials were characterized using TGA, XRD, SEM and rotational rheometry. Cloisite 15A, Cloisite 93A, Nanomer I44 and a bentonite modified with octadecylammonium (B18) display intercalation and exfoliation after mixing and annealing and produce nanocomposites with different degrees of ‘solid-like’ rheological behavior. The composites based in Cloisite 15A and Nanomer I44, which use the same intercalant, show very similar phase structure and rheological response, regardless of the origin and initial characteristics of the clays. These nanocomposites are the most affected by the thermal history during rheological characterization in the molten state. On the other hand, Cloisite 10A and Cloisite 30B display collapse of the silicate layers after compounding with no evidence of exfoliation.     

Rheological and Structure Investigation of Melt Mixed Multi-Walled Carbon Nanotube/PE Composites

In this study a series of melt mixed multi-walled carbon nanotube (MWNT)/Polyethylene composites with several carbon nanotube (CNTs) concentrations were investigated. A good dispersion of the nanotubes in the matrix was seen using scanning electron microscopy. Melt rheological measurements in dynamic mode were used to estimate the percolation state of the CNTs within the polymer and to provide information about the structure of the CNT/polymer composites. The effect of nanotubes on the non-isothermal crystallization behaviour of the nanocomposites was also studied by differential scanning calorimetry.     

Elongational Viscosity and Foaming Behavior of PP Modified by Electron Irradiation or Nanotube Addition

Summary : In this study, two different routes were chosen which are expected to influence the elongational viscosity and, thus, the foaming behavior of polypropylene (PP). Electron irradiation of a linear PP was performed at room temperature using different doses. Enhanced long-chain branching was observed with increased irradiation dose. In addition, a linear PP was filled with 5 wt% multiwalled carbon nanotubes (MWNT) by melt mixing at 200 °C. These modified PP materials were investigated with respect to their shear and elongational behavior. After foaming, irradiated PP led to an expansion factor which is about 60% higher than that of the non-irradiated product. In case of PP filled with 5 wt% MWNT the value of the expansion factor is about 70% higher than that of pure PP expanded under the same conditions. The cell structure is much finer in both cases as compared to unmodified PP.     

Influence of amine-grafted multi-walled carbon nanotubes on physical and rheological properties of PMMA-based nanocomposites

In this work, poly(methyl methacrylate) (PMMA) was grafted onto amine treated multi-walled carbon nanotubes (NH-MWNTs) and the physical and rheological properties of the NH-MWNTs–g-PMMA nanocomposites were investigated. The graft reaction of NH-MWNTs and the PMMA matrix was confirmed from the change of the N_1S peaks, including those of amine oxygen and amide oxygen, by X-ray photoelectron spectroscopy (XPS). The thermal and mechanical properties of the NH-MWNT–g-PMMA nanocomposites were enhanced by the graft reaction between NH-MWNTs and PMMA matrix. In addition, the viscosity of the nanocomposites was increased with the addition of NH-MWNTs. Storage (G′) and loss modulus (G″) were significantly increased by increase in the NH-MWNT content compared to acid-treated MWNTs/PMMA nanocomposites. This increase was attributed to the strong interaction by the grafting reaction between NH-MWNTs and the PMMA matrix.     

熔体自由基反应法制备聚丙烯/碳纳米管复合材料

以2,5-二甲基-2,5-双（叔丁基过氧基）己烷（DHBP）在聚丙烯体系中引发形成自由基,以二硫化四甲基秋兰姆（TMTD）调控自由基反应,通过熔融共混一步法制备了共价接枝的聚丙烯/碳纳米管（PP/CNTs）复合材料。 通过拉曼光谱和透射电子显微镜证明发生了共价接枝反应,并研究了PP/CNTs的结晶性能、热性能与力学性能。 结果表明,发生共价接枝的PP/CNTs与未接枝的PP/CNTs及PP相比,其结晶温度分别提高了2.6和12.0 ℃,热分解温度T5%分别提高了6.4和34.8 ℃,其拉伸强度和拉伸模量略有提高,冲击强度分别提高了56.7%和58.1%。     

Morphological and mechanical properties of carbon nanotube/polymer composites via melt compounding

The mechanical properties and morphology of multiwall carbon nanotube (MWNT)/polypropylene (PP) nanocomposites were studied as a function of nanotube orientation and concentration. Through melt mixing followed by melt drawing, using a twin screw mini‐extruder with a specially designed winding apparatus, the dispersion and orientation of MWNTs was optimized in PP. Tensile tests showed a 32% increase in toughness for a 0.25 wt % MWNT in PP (over pure PP). Moreover, modulus increased by 138% with 0.25 wt % MWNTs. Transmission electron microscopy and scanning electron microscopy demonstrated qualitative nanotube dispersion and orientation. Wide angle X‐ray diffraction was used to study crystal morphology and orientation by calculating the Herman's orientation factor for the composites as function of nanotube loading and orientation. The addition of nanotubes to oriented samples causes the crystalline morphology to shift from α and mesophase to only α phase. Furthermore, the addition of nanotubes (without orientation) was found to cause isotropization of the PP crystal, and drawing was shown to improve crystal orientation through the orientation factor. In addition, differential scanning caloriometry qualitatively revealed little change in overall crystallinity. In conclusion, this work has shown that melt mixing coupled with melt drawing has yielded MWNT/PP composites with a unique combination of strength and toughness suitable for advanced fiber applications, such as smart fibers and high‐performance fabrics. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 864–878, 2006     

Nucleation, structure and lamellar morphology of isotactic polypropylene filled with polypropylene-grafted multiwalled carbon nanotubes

Polypropylene-based nanocomposites filled with polypropylene-grafted multiwalled carbon nanotubes (PP-g-MWNT) were compared to PP samples filled with pristine MWNT. The effect of such additives on the structure and morphology of the polymer matrix was studied by small angle X-ray scattering (SAXS), wide angle X-ray diffraction (WAXD), polarized light optical microscopy (PLOM) and differential scanning calorimetry (DSC). PP-g-MWNT allowed a more efficient and unhindered crystallization at a lamellar level, while MWNT disrupted the order of lamellar stacks, probably because of their tendency to aggregate. A common trend of tensile properties and lamellar morphology as a function of filler content was noted in the series filled with functionalized carbon nanotubes.     

Effect of carbon nanotubes on the photo-oxidative durability of syndiotactic polypropylene

Polymer nanocomposites with carbon nanotubes as fillers have attracted more attention than any other nanomaterials. A full development of these materials requires a deep understanding of the way they behave in the use conditions. In this work, the resistance to accelerated photooxidation of syndiotactic polypropylene/multi-walled carbon nanotube (sPP/MWCNTs) films was compared to the photooxidation behaviour of unfilled polypropylene films with the same structural organization. The chemical and structural modifications resulting from photooxidation have been followed using infrared spectroscopy and diffractometric analysis. It was found that a good dispersion degree of the nanofiller, evaluated by atomic force microscopy, contributes to reduction in the rate of photooxidation and an increase in the oxidative thermal stability of the polymeric matrix. Different concomitant effects are considered to explain these results, among which morphology and structure of the nanocomposites together with the MWCNT capacity to interact with oxygen molecules making them unavailable in the first stages of photooxidation.     

Preparation of polypropylene/sepiolite nanocomposites using supercritical CO2 assisted mixing

Well dispersed polypropylene (PP)/sepiolite clay nanocomposites were prepared successfully using supercritical carbon dioxide (scCO₂) assisted mixing with and without the presence of maleic anhydride grafted polypropylene (PP-g-MA) as compatibilizer. The resulting morphology and polymorphism of nanocomposites were established using X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) observations. The mechanical properties of the nanocomposites were investigated and compared with those obtained by a traditional melt compounding method. Our results showed that by using scCO₂ in the process, we were able to obtain better sepiolite dispersions and reduce breakage of sepiolite fibres. Consequently, a significant improvement in the yield stress was observed for the nanocomposites processed in scCO₂ compared to those processed by the traditional melt compounding. XRD data also indicated that the resulting nanocomposites had only α-phase crystallites of PP while the presence of sepiolite could also induce preferred orientation of these α-phase crystallites.     

HIPS／PP熔融反应共混及其动态力学性质

研究了高抗冲聚苯乙烯（HIPS）／聚丙烯（PP）共混物在过氧化二异丙苯（DCP）存在下的熔融反应过程及其动态力学性质．HIPS在DCP存在下以聚苯乙烯（PS）的降解为主，伴随着聚丁二烯（PB）的交联和接枝，PP在DCP存在下以降解为主，HIPS／PP在DCP存在下以PP同HIPS的反应接枝为主，这种原位生成的增容剂显著地改善了HIPS／PP两组份间的相容性，其分子运动特征较前两者发生明显变化，PS的Tg下降，PB和PP的Tg升高．     

多壁碳纳米管表面对硝基苯酚印迹复合材料的制备与吸附性能

以多壁碳纳米管表面接枝的L-苯丙氨酸为结合位点, 甲基丙烯酸为功能单体, 乙二醇二甲基丙烯酸酯为交联剂, 采用沉淀聚合技术, 在碳纳米管表面制备了对硝基苯酚印迹复合材料. 采用红外光谱和扫描电镜研究了该印迹复合材料的结构和形貌, 结果表明, 在碳纳米管表面接枝了一层稳定的印迹材料. 采用高效液相色谱研究了该印迹材料的等温吸附性能, 结果表明, 该印迹材料对模板分子具有较大的吸附容量(Qmax=80.5 μmol/g)和良好的选择吸附性能(选择因子达2.5). 以该印迹材料作为固相萃取吸附剂, 研究了它对对硝基苯酚和其它结构类似物混合溶液的动态吸附性能, 结果表明, 印迹复合材料对对硝基苯酚的吸附容量不受结构类似物浓度的影响, 能较好地应用于对硝基苯酚的分离富集检测.     

多官能团单体对马来酸酐接枝聚丙烯流变行为的影响

研究了多官能团辅助单体偏苯三酸三丙烯酯(TATM)对马来酸酐接枝聚丙烯的熔体流动速率(MFR)和流变行为的影响.当以不含抗氧剂的聚丙烯粉料为原料时,TATM的加入对稳定接枝产物MFR的效果并不理想.但将聚丙烯粉料添加抗氧剂并造粒后,TATM的加入则可有效稳定体系的MFR,各种流变曲线显示出接枝产物的熔体弹性明显提高,说明有枝化或交联结构出现.针对PP粉料和粒料间接枝产物流变行为存在的重大差异,结合熔体自由基接枝反应的机理进行了解释.TATM能够起到稳定MFR的效果是由于其提高了接枝物的熔体弹性,从而抵消了聚丙烯熔体接枝反应中所不可避免的β断链所造成的剪切黏度下降.聚丙烯粉料和粒料中抗氧剂的差异对聚丙烯的加工降解有严重影响,造成了TATM在不同聚丙烯体系中效果的差异.     

聚丙烯接枝改性及其挤出发泡研究

以有机过氧化物为引发剂,以双螺杆挤出机为反应器,将线型不饱和聚酯(ULP)接枝到聚丙烯(PP)分子链上。通过FTIR、DSC及凝胶含量测试,对MPP的结构和性能进行了研究,表明PP发生了接枝反应;泷变性能和熔体流动速率(MFR)测定表明,接枝反应有效地改善了PP流变性能,用双螺杆挤出机对未接枝和接枝的PP进行了发泡研究,SEM分析表明接枝PP具有更好的发泡效果。     

金属卟啉有机共价和非共价修饰多壁碳纳米管

合成了5-(4-羟基苯基)-10,15,20-三苯基卟啉锌配合物, 与活化的多壁碳纳米管(MWNT)发生酯化反应, 从而得到金属卟啉有机共价化学修饰的多壁碳纳米管复合物; 利用金属卟啉环上的π电子与多壁碳纳米管管壁上的π电子通过π-π堆积效应, 得到金属卟啉有机非共价修饰的多壁碳纳米管复合物. 通过透射电镜(TEM)考察了金属卟啉-多壁碳纳米管复合物的形貌特征; 通过红外光谱对产物的化学结构进行了表征; 通过紫外光谱、荧光光谱和热失重分析(TGA)对比分析了两类复合物, 发现非共价修饰的金属卟啉-碳纳米管复合物的荧光淬灭率更高, 非共价修饰的金属卟啉-碳纳米管复合物中卟啉的含量比较高.     

Polypropylene nanocomposites with various functionalized‐multiwalled nanotubes: thermomechanical properties,morphology, gas permeation,and optical transparency

Polypropylene (PP) nanocomposites with three different functionalized‐multiwalled nanotubes (F‐MWNTs) are compared in terms of their thermomechanical properties, morphology, oxygen permeability, and optical transparency. The F‐MWNTs dodecanol‐MWNT, dodecylamine‐MWNT, and 1,1,1,3,3,3‐hexafluoro‐2‐phenyl‐2‐propanol‐MWNT were combined with PP to produce hybrid films. The variations of their properties with the matrix polymer F‐MWNT content are discussed. Transmission electron microscopy photographs show that most of the F‐MWNTs are dispersed homogeneously in the matrix polymer on the nanoscale, although some agglomerated F‐MWNT particles are formed. Even composites with low F‐MWNT contents (≤3 wt %) exhibit much better thermomechanical values than pure PP. The gas permeability of the hybrids was found to decrease linearly with increases in the F‐MWNT content of the PP matrix. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010