动态硫化法PP／EPDM／纳米SiO2双重粒子协同增韧改性研究

以三元乙丙橡胶（EPDM）作弹性粒子,以纳米SiO2作刚性粒子,通过动态硫化方法制备了PP／EPDM／纳米SiO2三元改性材料,并采用力学性能测试,动态力学试验,DSC分析和偏光显微镜观察等方法,研究了该材料的结构与性能。结果表明,纳米SiO2与EPDM对PP具有协同增韧和增强效应,这种效应与2种粒子的浓度比相关,当纳米SiO2质量分数为3％,EPDM质量分数为10％时,协同作用最明显,2种粒子使PP出现较大的低温损耗模量峰（E″）和内耗峰（tanδ),并具有成核作用,使PP结晶温度提高,结晶速率加快,形成的球晶细小而均匀,并同时提高结晶度和熔点。     

Kinetics-controlled compatibilization of immiscible polypropylene/polystyrene blends using nano-SiO2 particles

Rigid inorganic filler has been long time used as a reinforcement agent for polymer materials. Recently, more work is focused on the possibility that using filler as a compatibilizer for immiscible polymer blends. In this article, we reported our efforts on the change of phase morphology and properties of immiscible polypropylene(PP)/polystyrene(PS) blends compatibilized with nano-SiO₂ particles. The effects of filler content and mixing time on the phase morphology, crystallization behavior, rheology, and mechanical properties were investigated by SEM, DSC, ARES and mechanical test. A drastic reduction of PS phase size and a very homogeneous size distribution were observed by introducing nano-SiO₂ particles in the blends at short mixing time. However, at longer mixing time an increase of PS size was seen again, indicating a kinetics-controlled compatibilization. This conclusion was further supported by the unchanged glass transition temperature of PS and by increased viscosity in the blends after adding nano-SiO₂ particles. The compatibilization mechanism of nano-SiO₂ particles in PP/PS blends was proposed based on kinetics consideration.     

The control of miscibility of PP/EPDM blends by adding lonomers and applying dynamic vulcanization

The control of miscibility for isotactic polypropylene (PP) and ethylene-propylene-diene terpolymer (EPDM) has been attempted by adding poly(ethylene-comethacrylic acid) (EMA) ionomers and by applying dynamic vulcanization. The rheological properties, crystallization behavior, and morphology of the dynamically vulcanized EPDM/PP/ionomer ternary blends were investigated with a Rheometrics dynamic spectrometer (RDS), a differential scanning calorimeter (DSC), and a scanning electron microscope (SEM). Two kinds of EMA ionomers neutralized with different metal ions (Na⁺ and ZN⁺⁺) were investigated. Blends were prepared on a laboratory internal mixer at 190°C. Blending and curing were performed simultaneously, i.e., EPDM was vulcanized with dicumyl peroxide (DCP) in the presence of PP/ionomer. The composition of PP and EPDM was fixed at 50/50 by wt% and the contents of EMA ionomer were vaired from 5 to 20 parts based on the total amount of PP and EPDM. It was found that the addition of ionomers and the application of the dynamic vulcanization were effective in enhancing the miscibility of PP and EPDM. The structure of the blends was controlled by the following three component phases, i.e., the phase of the dynamially valcanized EPDM, PP, and Zn-neutralized ionomer. The ternary blends showed more miscibility than the PP/EPDM binary blend. This is due to the thermoplastic interpenetrating polymer network (IPN) of the ternary blends. The structure and properties of the ternary blends differed, depending on the types and contents of ionomer, i.e., the ternary blend containing Na-neutralized ionomer did not show a thermoplastic IPN structure clearly, even though the blend was prepared by dynamic vulcanization. The ternary blend containing Zn-neutralized ionomer clearly showed the behavior of a thermoplastic IPN when the contents of ionomer and DCP were 15 parts and 1.0 part, respectively.     

PP／EPDM共混体系界面的研究

本文采用马来酸酐对三元乙丙橡胶（ＥＰＤＭ）进行熔融接枝改性,将性后的ＥＰＤＭ与聚丙烯（ＰＰ）共混,对ＰＰ／ＥＰＤＭ和ＰＰ／ＥＰＤＭ－ｇ－ＭＡＨ两种共混体系的界面状况进行了对比。运用Ｈｕｇｇｉｎｓ参数、界面张力参数对界面状况进行了表征;运用扫描电镜（ＳＥＭ）和偏光显微镜对共混物的冲击断口形貌以及结晶情况进行了观察与分析;探讨了界面状况与共混物力学性能以及流变性能间的关系。     

Morphology/behavior relationship and recyclability of composites based on PP/EPDM blends and short aramid fibers

The effect of short aramid fibers on the mechanical behavior of polypropylene (PP) and ethylene‐propylene‐diene (EPDM) and their blends has been investigated by means of an experimental design. The results have shown that aramid fibers are very effective reinforcing agents for composites when the continuous phase of the matrix is constituted by PP, so sensible increments in tensile modulus and strength are obtained as fiber content in the composites increases. An optimal matrix composition and fiber content has been observed that produced high abrasion resistance compounds. However, the abrasion resistance of very rich EPDM matrices is hardly affected by fibers content. The addition of fibers to EPDM rich (>50%) matrices gives rise to a sensible decrease of the impact strength of this polymer. However, at PP contents above 50% in the polymer matrix, an increase of impact strength is observed at fiber percentages in the composites above 10%. The different behavior of the fibers depending on matrix type can be attributed to a better affinity of these fibers for PP matrix. Morphological studies of the composites have been carried out by scanning electron microscopy. Finally, the price and recyclability of these materials have been analyzed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2474–2484, 2002     

Study on the phase structures and toughening mechanism in PP/EPDM/SiO2 ternary composites

In this paper, EPDM rubber and nano-SiO₂ particles were employed to modify PP simultaneously. Our goal was to control the distribution and dispersion of EPDM and nano-SiO₂ particles in PP matrix by using an appropriate processing method and adjusting the wettability of nano-SiO₂ particles toward PP and EPDM, so as to achieve a simultaneous enhancement of toughness and modulus of PP. With regard to this, two kinds of nano-SiO₂ particles (with hydrophilic or hydrophobic) as well as two processing methods (one-step or two-step) were employed to prepare PP/EPDM/SiO₂ ternary composites. A unique structure with the majority of EPDM particles surrounded by SiO₂ particles was first observed by using hydrophilic SiO₂ and two-step processing method, resulting in a dramatically increase of Izod impact strength as the rubber content in the range of brittle-ductile transition (15-20 wt%). The observation that poor adhesion and poor compatibility between particles and PP matrix could result in a significant increase in Izod impact strength was unusual and needed further investigation. This could be tentatively understood as a consequence of the overlap of the ‘stress volume’ between EPDM and SiO₂ particles due to the formation of the unique structure. Our work provided a deep understanding of the toughening mechanism and a new way for the preparation of high performance polymer composites.     

交联剂对动态硫化PP／EPDM中PP晶体及EPDM形态结构的影响

针对ＰＰ／ＥＰＤＭ动态硫化中有机过氧化物交联剂Ａ用量对试样拉伸,弯曲和冲击等性能所产生的较大的影响,采用偏光显微镜研究了不同交联剂Ａ用量下动态硫化ＰＰ／ＥＰＤＭ中连续相ＰＰ的晶体结构和分散相ＥＰＤＭ的形态结构特征。     

Morphology and properties of PP/EPDM binary blends and PP/EPDM/nano‐CaCO3 ternary blends

In this article, the morphology, crystallization, and rheological behaviors of polypropylene (PP)/ethylene‐propylene‐diene terpolymer (EPDM) binary blend and PP/EPDM/calcium carbonate nanoparticles (nano‐CaCO₃) ternary blend were investigated. Two processing methods, i.e., direct extrusion and two‐step extrusion, were employed to prepare the PP/EPDM/CaCO₃ blend. The influence of EPDM and nano‐CaCO₃ respectively on phase morphology and properties of PP/EPDM blend and PP/EPDM/CaCO₃ blend were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and dynamic rheometer. The crystallinity and crystallization temperature of PP/EPDM blend were improved in comparison to pure PP due to addition of EPDM, but kept invariable with the increased EPDM loading. As the EPDM content was increased, the mobility of PP molecular chains was weakened. Compared with direct extruded blend, less and finer nano‐CaCO₃ was dispersed in matrix of two‐step extruded blend. Accordingly, the increased nano‐CaCO₃ in matrix gave rise to a weaker increment in crystallinity and crystallization temperature of two‐step extruded blend, and a later platform of tanδ curve. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Microstructural Characterization of Sintered MoSi2/SiCP Composites

A MoSi₂/SiC_P composite was synthesized by in situ reactive sintering of a mixture of molybdenum, silicon, and carbon powders. Its microstructural features were studied by X-ray energy dispersive spectroscopy (EDS), conventional transmission electron microscopy (CTEM), and high-resolution transmission electron microscopy (HREM). It was determined that the composite was composed of α-MoSi₂ and β-SiC. There were no specific orientation relationships between the MoSi₂ matrix and SiC_P, because the MoSi₂ and SiC were formed at 1450°C by the reaction of solid Mo and C and liquid Si. The abrupt change occurring in the microstructure of the composite is explained by the presence of an interface between MoSi₂ and SiC_P, where no observable SiO₂ amorphous layer or particles were found. Microtwins and stacking faults were frequently observed in {111} planes of SiC_P.     

Effects of crosslinked elastomer particles on heterogeneous nucleation of isotactic PP in dynamically vulcanized EPDM/PP and EOC/PP blends

The isothermal and non-isothermal crystallizations of PP in neat form and in the TPVs EPDM/PP and EOC/PP were investigated using differential scanning calorimetry (DSC). The crystallization of PP was systematically studied by fitting mathematical models, and was later confirmed by X-ray diffraction (XRD) and by scanning electron microscopy (SEM). The experiments revealed that crosslinked elastomer particles first accelerated the primary nucleation of the PP matrix, acting effectively as a nucleating agent that reduces the induction time while increasing the nucleation efficiency. In the secondary nucleation regime (growth of spherulites), the crosslinked elastomer particles enhanced crystal growth rate, reducing the nucleation energy contribution from PP chain folding. Moreover, the crosslinked elastomer particles increased the final thickness of PP lamellae from that of neat PP, and this was corroborated by the XRD results. On comparing the two types of elastomer, it was found that the EOC particles were more effective in heterogeneous cell nucleation than the EPDM particles. The morphological study by SEM revealed completely altered PP spherulite size and shape, as well as their altered distribution, affected by heterogeneous nucleation effects of the crosslinked elastomer particles.     

反应性聚丙烯/三元乙丙橡胶共混物的流变性能研究

采用高压毛细管流变仪 ,研究了EPDM含量、交联剂、交联助剂等因素对反应性PP/EPDM共混物性能的影响。结果表明 ,EPDM分散相浓度为 2 0～ 2 5phr,反应共混工艺对体系的消缠降粘效果显著 ;交联剂A的含量越高 ,体系表观粘度越小 ,但粘度对剪切的响应不敏感 ;交联剂B和并用交联剂S可抑制PP降解 ,进一步优化材料力学性能 ,并仍保持体系加工流动性高于简单共混PP/EPDM。     

Carbon-13 assignments of EPDM/PP atactic blends by DEPT and HETCOR

The structure of the elastomeric ethylene–propylene–diene terpolymer/atactic polypropylene (EPDM/PPA) blends were assigned by NMR using DEPT (distortionless enhancement by polarization transfer) and HETCOR (heteronuclear correlation) sequences. These methods were carried out to elucidate solid-state ¹³C-NMR assignments of polymeric blends. © 1996 John Wiley & Sons, Inc.     

Properties of high-volume fly ash concrete incorporating nano-SiO2

This paper presents a laboratory study on the properties of high-volume fly ash high-strength concrete incorporating nano-SiO₂ (SHFAC). The results were compared with those of control Portland cement concrete (PCC) and of high-volume fly ash high-strength concrete (HFAC). Assessments of these concrete mixes were based on short- and long-term performance. These included compressive strength and pore size distribution. Significant strength increases of SHFAC compared to the high-volume fly ash high-strength were observed as early as after 3 days curing, and improvements in the pore size distribution of SHFAC were also observed. In this work, the hydration heat of nano-SiO₂ fly ash cement systems was also studied in comparison to the fly ash-cement systems and to the pure cement systems. In addition, the weight change of fly ash incorporating nano-SiO₂, fly ash, and nano-SiO₂ alone after immersed in saturated lime solution was also studied.     

Compatibilization of PP/EPDM blends by grafting acrylic acid to polypropylene and epoxidizing the diene in EPDM

In this article, ethylene–propylene–diene‐rubber (EPDM) was epoxidized with an in situ formed performic acid to prepare epoxided EPDM (eEPDM). The eEPDM together with the introduction of PP‐g‐AA was used to compatibilize PP/EPDM blends in a Haake mixer. FTIR results showed that the EPDM had been epoxidized. The reaction between epoxy groups in the eEPDM and carboxylic acid groups in PP‐g‐AA had taken place, and PP‐g‐EPDM copolymers were formed in situ. Torque test results showed that the actual temperature and torque values for the compatibilized blends were higher than that of the uncompatibilized blends. Scanning electron microscopy (SEM) observation showed that the dispersed phase domain size of compatibilized blends and the uncompatibilized blends were 0.5 and 1.5 μm, respectively. The eEPDM together with the introduction of PP‐g‐AA could compatibilize PP/EPDM blends effectively. Notched Izod impact tests showed that the formation of PP‐g‐EPDM copolymer improved the impact strength and yielded a tougher PP blend. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3949–3954, 2006     

Selective crosslinking reaction in polymer blends. III. The effects of the crosslinking of dispersed EPDM particles on the impact behavior of PP/EPDM blends

The selective dynamic crosslinking reaction by means of the N,N'-m-phenylene–bismaleimide/poly-(2,2,4-trimethyl-1,2-dihydroquinoline) system was carried out on PP/EPDM blends and its effect on the Izod impact strength (IIS) was investigated. Three series of PP/EPDM combinations were adopted to establish different morphologies. In each series, the EPDM wt % varied from 5 to 30 at 5 wt % intervals. The system crosslinked the EPDM particles selectively without PP degradation and change of morphology. Following the crosslinking, the IIS at 23, ?10, and ?30°C increased in all blends, and the critical EPDM wt % at 23°C necessary to cause the dramatic IIS increase was lowered. The increase in interfacial adhesion is considered to be the most important factor necessary for the improvement. The nucleation effect of the crosslinked particles and the decrease of crystallinity of the EPDM were also considered to contribute to the improvement in the IIS. Impact fracture energy absorption can thus be changed by adjusting the magnitude of the interfacial adhesion by the dynamic crosslinking even at essentially the same morphology. © 1995 John Wiley & Sons, Inc.     

Enhanced methanation stability of nano-sized MoS2 catalysts by adding Al2O3

A series of unsupported MoS₂ catalysts with or without Al₂O₃ modification was prepared using a modified thermal decomposition approach. The catalysts were tested for the methanation of carbon monoxide and the optimum one has 25.6 wt-% Al₂O₃ content. The catalysts were characterized by nitrogen adsorption measurement, X-ray diffraction and transmission electron microscopy. The results show that adding appropriate amount of Al₂O₃ increases the dispersion of MoS₂, and the increased interaction force between MoS₂ and Al₂O₃ can inhibit the sintering of active MoS₂ to some extent.     

Electrochemical performance of nano-SiO2 modified LiCoO2 thin films fabricated by electrostatic spray deposition (ESD)

With a mixture of a SiO₂ sol and a solution of lithium and cobalt acetates as the precursor, nano-SiO₂ modified LiCoO₂ films were fabricated by the electrostatic spray deposition (ESD) technique. The SiO₂ content of these films was 0, 5, 10, 15 and 20 wt%, respectively. Their structure and electrochemical properties were characterized by means of X-ray diffraction, scanning electron microscopy, galvanostatic cell cycling, AC impedance spectroscopy and cyclic voltammetry. Li₂CoSiO₄ was found formed in the SiO₂-containing films. The film with 15 wt% SiO₂ shows the best cycling stability with the capacity of 130 mAh/g in the voltage range between 2.7 and 4.3 V at the current density of 0.1 mA/cm². Due to its resulted small cell impedance, it has excellent rate capability. A LiCoO₂ (shell)/SiO₂ (core) structure model is proposed to explain the improved properties of these films.     

动态硫化EPDM/PP共混物力学性能的研究

考察了硫黄用量和聚合物共混比对动态硫化ＥＰＤＭ／ＰＰ热塑性弹性体性能的影响。结果表明,随着硫黄用量增大,ＥＰＤＭ／Ｐ共混物的拉伸强度、１００％定伸应力和扯断伸长率先增大后减小、硬度有所增大,随着ＰＰ用量的增大,ＥＰＤＭ／ＰＰ共混物的拉伸强度、１００％定伸应力和硬度均有所增大,扯断伸长率也先大后减小。ＰＰ用量的变化对这些性能的影响更显。     

Brittle-ductile transition in PP/EPDM blends: effect of notch radius

The toughness of polypropylene (PP)/ethylene-propylene-diene monomer (EPDM) blends was studied over wide ranges of EPDM content and temperature. In order to study the effect of notch radius (R), the toughness of the samples with different notch radii was determined from Izod impact test. The results showed that both toughness and brittle-ductile transition (BDT) of the blends were a function of R, respectively. At test temperatures, the toughness tended to decrease with increasing 1/R for various PP/EPDM blends. Moreover, the brittle-ductile transition temperature (T_BT) increased with increasing 1/R, whereas the critical interparticle distance (ID_c) reduced with increasing 1/R. Finally, it was found that the different curves of ID_c versus test temperature (T) for different notches reduced down to a master curve if plotting ID_c versus T_BT^m-T, where T_BT^m was the T_BT of PP itself for a given notch, indicating that T_BT^m-T was a more universal parameter that determined the BDT of polymers. This conclusion was well in agreement with the theoretical prediction.     

Inhibited transesterification and enhanced fibrillation of TLCP by nano-SiO2 in polycarbonate matrix

Hybrid composites composed of a thermotropic liquid crystalline polymer (TLCP), nano-SiO₂ and polycarbonate (PC) were prepared by melt blending in a twin-screw extruder. Infrared spectroscopy analysis indicated that the transesterification between PC and TLCP molecules during melt blending was significantly reduced in TLCP/PC blends filled with nano-SiO₂, compared to the unfilled TLCP/PC one. Scanning electron microscopy (SEM) observation showed that better compatibility and finer TLCP dispersion were reached in the unfilled blend, which made the fibrillation of TLCP difficult in capillary flow even at high shear rate. In contrast to this, well-developed TLCP fibrils were formed by capillary flow in nano-SiO₂ filled TLCP/PC blends. By increasing the nano-SiO₂ concentration and shear rate, the fibrillation of TLCP was significantly enhanced. Thermodynamically the interfacial tension between these components and dynamically the viscosity ratio of TLCP to PC were used to investigate the mechanism of nano-SiO₂ in inhibiting the transesterification and enhancing the fibrillation of TLCP droplets in these hybrid composites.