Largely improved toughness of PP/EPDM blends by adding nano-SiO2 particles

As a part of long-term project aimed at super polyolefin blends, in this work, we report the toughness and phase morphology of polypropylene (PP)/EPDM/SiO₂ ternary composites. Two processing methods were employed to prepare PP/elastomer/filler ternary composites. One was called one-step processing method, in which the elastomer and the filler directly melt blended with PP matrix. Another one was called two-step processing method, in which the elastomer and the filler were mixed first, and then melt blended with pure PP. Two kinds of PP (grafted without or with maleic anhydride (PP-g-MA)) and SiO₂ (treated with or without coupling agent) were used to control the interfacial interaction among the components. The dependence of the phase morphology on interfacial interaction and processing method was investigated. It was found that the formation of filler-network structure could be a key for a simultaneous enhancement of toughness and modulus of PP and its formation seemed to be dependent on the work of adhesion (W_AB) and processing method. As the W_AB of PP/EPDM interface was much lower than that of PP/SiO₂ and EPDM/SiO₂, and the two-step processing method was used, the formation of filler-network structure was favorable. In this case, a super toughened PP ternary composite with the Izod impact strength 2-3 times higher than PP/EPDM binary blend and 15-20 times higher than pure PP could be achieved.     

Effects of nanosilica filler surface modification and compatibilization on the mechanical,thermal and microstructure of PP/EPR blends

Polypropylene/ethylene-propylene rubber/nanosilica (PP/EPR/nano-SiO₂) composites were prepared by a melt blending masterbatch process using a Brabender mixer. In order to improve the interfacial adhesion and achieve diverse desired properties of the composites, nanosilica surface silylation by means of two silane coupling agents: N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (AEAPTMS) and 3-methacryloxypropyltrimethoxysilane (MPTMS) was explored. The composites were also compatibilized using three compatibilizers: methyl methacrylate grafted PP (MMA-g-PP), glycidylmethacrylate grafted PP (GMA-g-PP) and maleic anhydride grafted PP (MAH-g-PP). The properties of the blends and the composites were examined using tensile and Izod impact tests, differential scanning calorimetry (DSC), thermogravimetric analysis (ATG) and scanning electron microscopy (SEM). According to the mechanical property evaluations, the incorporation of nano-SiO₂ particles into PP/EPR blend improved the tensile strength and Young’s modulus of the composites. The elongation and Izod impact strength were adversely affected. A significant improvement in the mechanical properties was obtained for the composites with AEAPTMS-SiO₂ and MAH-g-PP. The DSC results indicated that the incorporation of the modified silica and MAH-g-PP increased the crystallinity of the composites. However, no significant variation in the crystallinity was observed as a result of the addition of MMA-g-PP and GMA-g-PP. The TGA results revealed that the composites exhibit a higher thermal stability than that of the neat matrix. SEM micrographs of the fractured surfaces revealed a two-phase morphology with EPR nodules being dispersed in the PP matrix. SEM also indicated that the incorporation of MAH-g-PP into PP/EPR composites contributes to a better dispersion of the EPR phase and nano-SiO₂ particles in the polymer matrix.     

NONISOTHERMAL CRYSTALLIZATION KINETICS AND MECHANICAL PROPERTIES OF PP/NANO-SiO2 COMPOSITES

The nonisothermal crystallization kinetics of polypropylene (PP)/nano-SiO₂ composites was studied by means of differential scanning calorimetry (DSC). The modified Avrami theories by Jeziorny, Ozawa, and Mo were used to analyze the data of DSC. The results showed that both the Jeziorny and Mo methods could describe this system very well, but the Ozawa analysis failed. The activation energy was evaluated by the Kissinger method. It was found that the crystallization activation energy of PP was higher than that of PP/nano-SiO₂ composites. The determined results of mechanical properties showed that the addition of nano-SiO₂ increased the mechanical properties of the PP. Micrographs of Polarized optical micrograph (POM) further demonstrated that nano-SiO₂ could toughen the PP.     

Organic/inorganic composite membranes based on polybenzimidazole and nano-SiO2

Organic/inorganic composite membranes based on polybenzimidazole (PBI) and nano-SiO₂ were prepared in this work. However, the preparation of PBI/SiO₂ composite membrane is not easy since PBI is insoluble in water, while nano-SiO₂ is hydrophilic due to the hydrophilicity of nano-SiO₂ and water-insolubility of PBI. Thus, a solvent-exchange method was employed to prepare the composite membrane. The morphology of the composite membranes was studied by scanning electron microscopy (SEM). It was revealed that inorganic particles were dispersed homogenously in the PBI matrix. The thermal stability of the composite membrane is higher than that of pure PBI, both for doped and undoped membranes. PBI/SiO₂ composite membranes with up to 15 wt% SiO₂ exhibited improved mechanical properties compared with PBI membranes. The proton conductivity of the composite membranes containing phosphoric acid was studied. The nano-SiO₂ in the composite membranes enhanced the ability to trap phosphoric acid, which improved the proton conductivity of the composite membranes. The membrane with 15 wt% of inorganic material is oxidatively stable and has a proton conductivity of 3.9 × 10⁻³ S/cm at 180 °C.     

Effect of nano-SiO2 particle size on the formation of LLDPE/SiO2 nanocomposite synthesized via the in situ polymerization with metallocene catalyst

Here, we revealed the effect of particle size of the nanoscale SiO₂ on catalytic and characteristic properties of LLDPE/nano-SiO₂ composites synthesized via the in situ polymerization with a zirconocene/MAO catalyst. In the experiment, SiO₂ (10 and 15 nm) was first impregnated with MAO. Then, copolymerization of ethylene/1-hexene was performed in the presence of nano-SiO₂/MAO to produce LLDPE/nano-SiO₂ composites. It was found that the larger particle exhibited higher polymerization activity due to fewer interactions between SiO₂ and MAO. The larger particle also rendered higher insertion of 1-hexene leading to decreased melting temperature (T_m). There was no significant change in the LLDPE molecular structure by means of ¹³C NMR.     

Wear resistance and friction coefficient of nano-SiO<Subscript>2</Subscript> and ash-filled HDPE/lignocellulosic fiber composites

This work comparatively evaluates the effect of nano-SiO₂ (at 2 and 3 wt%), rice husk and bagasse ash (at 5 and 10 wt%) on the wear resistance and friction coefficient of HDPE (high-density polyethylene)/lignocellulosic fiber composites. Rice husk and bagasse fibers at 50% by weight contents were mixed with HDPE and 2% maleic anhydride-grafted polyethylene as compatibilizer. SEM images showed a fairly appropriate connection between the polymer matrix and fillers. We found that the fillers improve the wear resistance, and the effect of nano-SiO₂ is more pronounced. The rice husk ash showed a better performance compared to the bagasse ash, probably due to greater SiO₂ content measured by X-ray fluorescence spectrometry. In contrast to nano-SiO₂, both ashes had a reducing effect on other mechanical strengths (Izod impact resistance, modulus of elasticity and modulus of rupture). All fillers remarkably increased the water absorption and thickness swelling. The water uptake of composites increased after wear.     

Flame retardant,mechanical, and hot air aging properties of ethylene-propylene-diene monomer/ammonium polyphosphate/nano-silic composite rubber

In this work, effect of the ratio of nonhalogenated flame retardants (ammonium polyphosphate [APP] and nano-silica [nano-SiO₂]) on the mechanical, thermal, and flame retardant properties of ethylene-propylene-diene monomer (EPDM) composite rubber were investigated. Vulcanization characteristics, high temperature compression permanent deformation, thermal oxygen aging, dynamic thermodynamic analysis, thermal stability, cone calorimetry, limiting oxygen index (LOI), horizontal vertical combustion (UL-94), and scanning electron microscopy were carried out. The experimental results showed that the mechanical properties of the composite rubber decreased with the addition of APP. However, the addition of nano-SiO₂ was found to significantly improve the mechanical properties of the composite rubber when it was incorporated. In terms of flame retardant properties of EPDM composite rubber, the combination of APP and nano-SiO₂ has a synergistic flame retardant effect in comparison to the use of single APP flame retardant. The heat release rate of EPDM composite rubber decreased by 34%, the total heat release decreased by 19%, the LOI increased by 76%, and the flame retardant grade of EPDM composite rubber reached V-0. The EPDM composite rubber fabricated in the present study showed excellent fire resistance and desirable mechanical properties, which are of practical significance for further expanding the application ranges of EPDM rubbers.     

改性纳米SiO2/聚氨酯-含氟丙烯酸酯无皂乳液合成及其胶膜性能表征

引言水性聚氨酯相对溶剂型聚氨酯具有不燃、气味小、不污染环境等优点[1-2],从而广泛用于涂料[3]、胶黏剂[4]、油墨[5]等领域。目前,常用于软包装领域的薄膜主要是表面能很低的非极性膜,而水性聚氨酯胶黏剂具有较高的表面自由能,对非极性膜的润湿性差,因此需要降低水性聚氨酯的表面张力,达到润湿非极性膜的目的。     

Investigation on the mechanical performances of ternary nylon 6/SEBS elastomer/nano‐SiO2 hybrid composites with controlled morphology

The distribution of maleated styrene‐hydrogenated butadiene‐styrene (mSEBS) elastomer and nano‐SiO₂ in nylon 6 matrix was controlled by varying the blending procedure. Nano‐SiO₂ particles with different surface properties (hydrophilic versus hydrophobic) were adopted to adjust their interactions with other components. Two different structures, separate dispersion of nano‐SiO₂ and elastomer particles as well as encapsulation of nano‐SiO₂ fillers by the elastomer, were obtained. The structures were confirmed through scanning electron microscope (SEM) investigation. The mechanical measurement results showed that the microstructure and the interactions among the components had dramatic influences on the final mechanical properties, especially Izod fracture toughness, for the ternary nanocomposites. The nanocomposites containing hydrophilic nano‐SiO₂ had better mechanical performances compared with the composites filled with hydrophobic SiO₂ when they were in the same microstructure. The nanocomposites with separate dispersion structure showed higher stiffness compared with those of encapsulation type. However, the separately dispersed nano‐SiO₂ particles restricted the cavitation of elastomer phases that led to low toughening effectiveness. The difference of cavitation intensity for elastomer phase was revealed by SEM investigation on the facture surfaces for the nanocomposites with the two different microstructures. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Improvement of the dispersity of micro-nano particles for PP/PVC composites using gas-assisted dispersion in a controlled foaming process

Polyvinyl chloride (PVC) and nanosilicon dioxide (nano-SiO₂) were blended with neat polypropylene (PP) to improve its flame retardancy and cellular foam structure, and the dispersal effects of PVC and nano-SiO₂ and the foaming effect of the PP/PVC composites were investigated. PP/PVC samples with different compositions and foaming degrees were first fabricated by conventional injection molding with and without a blowing agent. Tensile testing, differential scanning calorimetry, scanning electron microscopy, limiting oxygen index testing, and vertical burn testing were used to study the mechanical properties, thermal features, microstructures, and flame-retardant properties of the molded samples, and the samples with different degrees of foaming were compared. The results suggest that the foaming process facilitates the dispersion of PVC and nano-SiO₂, while the presence of PVC and nano-SiO₂ improves the foamability of PP. A method for a gas-assisted dispersion technology to control the foaming process was hence proposed. Considering that the mechanical properties of PP/PVC could be retained with satisfactory flame retardancy and weight loss, convenient processing, and low-cost materials; the technology presented can be directly applied for lightweight engineering and the manufacture of fire-resistant material and can act as a reference for other micro-nano processing involving the dispersion of particles. POLYM. ENG. SCI., 60:524–534, 2020. © 2019 Society of Plastics Engineers     

Effect of the mixing sequence on the morphology and properties of a polypropylene/polydimethylsiloxane/nano‐SiO2 ternary composite

Ternary composites of polypropylene (PP), polydimethylsiloxane (PDMS) elastomer, and nano‐SiO₂, prepared with three different mixing sequences, were studied for dispersion morphology and its effect on the crystallization of PP and the mechanical properties. The mixing sequence produced a significant effect on the dispersion morphology and, thereby, on the mechanical properties of the composites. A two‐step mixing sequence, in which nano‐SiO₂ was added in the second step to the PP/PDMS binary system, produced a significant encapsulation of nano‐SiO₂ by PDMS, and this, in turn, resulted in the poor modulus and impact strength of the composite. A one‐step mixing sequence of all three components produced a separated dispersion of PDMS and nano‐SiO₂ phases in the PP matrix with the occurrence of a fine band of nano‐SiO₂ particles at the boundaries of the PDMS domains and the presence of some nano‐SiO₂ filler particles inside the PDMS domains. This one‐step mixing sequence produced an improvement in the tensile modulus but a decrease in the impact strength with increasing nano‐SiO₂ content. In the third sequence of mixing, which involved a two‐step mixing sequence through the addition of PDMS in the second step to the previously prepared PP/nano‐SiO₂ binary system, the morphology of the dispersion showed separately dispersed PDMS and nano‐SiO₂ phases with a loose network of nano‐SiO₂ particles surrounding the PDMS domains. This latter series of ternary composites had the highest impact strength and exhibited high shear deformation under tensile and impact conditions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The morphology and mechanical properties of PP/EPDM/nano-CaCO3 composites: effect of initial mixing state

Polypropylene (PP) was blended with ethylene–propylene–diene terpolymer (EPDM) and calcium carbonate nanoparticles (nano-CaCO₃), where all the components were in different initial mixing states, i.e., all in solid (solid blending composite), nano-CaCO₃ and EPDM first forming solid master batch, then being mixed with solid PP (master batch blend composite) and all in melt (melt blending composite). The phase morphology, especially the distribution of nano-CaCO₃, and mechanical properties of the resultant composites and their dependence on the initial mixing states of the components were studied systematically. Morphological observation revealed that essentially different from the respectively dispersed morphology of nano-CaCO₃ particles and EPDM phase in the PP matrix in the solid blending composite, abundant well-dispersed nano-CaCO₃ particles concentrating around EPDM phase in the melt blending composite. Due to the cavitation initiated by the debonding and the fibrillation present at interface as a result of well-dispersed nano-CaCO₃ particles, its impact strength was pronouncedly enhanced, increasing 280 % compared to PP/EPDM composite. Our work paves the way to obtain high-performance PP composites.     

Influence of incorporation sequence of silica nanoparticles on morphology,crystallization behavior,mechanical properties,and thermal resistance of melt blended thermoplastic natural rubber

Thermoplastic natural rubber nanocomposites based on epoxidized natural rubber (ENR) and polypropylene blends at a fixed blend ratio of 50/50 wt% reinforced with small amount (2.5 wt%) of nanosilica (SiO₂) were prepared by melt‐mixing through three different incorporation sequences in an internal mixer. The effects of incorporation techniques on morphology, crystallization behavior, mechanical properties, dynamic, rheological characteristics, and thermal resistance of thermoplastic natural rubber (TPNR) nanocomposites were investigated. It was found that the dispersion of nanosilica in TPNRs was significantly dependent on the incorporation sequence. In the case where SiO₂ was premixed in ENR before blending with polypropylene (PP), the final morphology showed the good dispersion of SiO₂ in ENR phase, while the SiO₂ particles were localized near the PP interface when SiO₂ was premixed the in PP first. Whereas, when the three components were simultaneously mixed, the SiO₂ particles were mainly dispersed in the PP phase. It was also found that the improvements of Young's modulus, tensile strength, damping behavior, and thermal stability of TPNR nanocomposites were more pronounced when the SiO₂ particles localized in ENR phase. By contrast, the presence of SiO₂ particles in PP domain either near the interface or inside the PP phase affected the reduction in crystallinity of PP phase and showed a negative effect on mechanical properties due to the poor interface interaction between PP and SiO₂ particles. POLYM. COMPOS., 33:1911–1920, 2012. © 2012 Society of Plastics Engineers     

高强度微孔化三元乙丙橡胶泡沫材料的研制

采用辐射化学法制备了纳米SiO₂填充的三元乙丙橡胶泡沫材料,并对材料进行了后辐射交联处理。扫描电镜结果表明,纳米SiO₂用量是影响三元乙丙橡胶泡沫微孔化的关键因素,加入纳米SiO₂后,泡孔的分布均匀性提高,胞体直径减小,在SiO₂用量为30 phr时胞体直径降至13 μm;力学测试结果表明,随着纳米SiO₂用量的增加,材料的拉伸强度逐渐提高;断裂伸长率则先增加后减小,并在用量为30 phr时出现最大值。后辐射交联处理后,与未作后辐射交联试样对比,材料的拉伸强度与断裂伸长率均得到大幅提高。     

Physical properties and crystallization behavior of poly(lactide)/poly(methyl methacrylate)/silica composites

Poly(lactide)/poly(methyl methacrylate)/silica (PLA/PMMA/SiO₂) composites were fabricated using a twin‐screw extruder. Nanosilica particles were incorporated to improve the toughness of the brittle PLA, and a chain extender reagent (Joncryl ADR 4368S) was used to reduce the hydrolysis of the PLA during fabrication. Highly transparent PLA and PMMA were designated to blend to obtain the miscible and transparent blends. To estimate the performance of the PLA/PMMA/SiO₂ composites, a series of measurements was conducted, including tensile and Izod impact tests, light transmission and haze measurements, thermomechanical analysis, and isothermal crystallization behavior determination. A chain extender increases the ultimate tensile strength of the PLA/PMMA/SiO₂ composites by ～43%, and both a chain extender and nanosilica particles increase Young's modulus and Izod impact strength of the composites. Including 0.5 wt % nanosilica particles increase the elongation at break and Izod impact strength by ～287 and 163%, respectively, compared with those of the neat PLA. On account of the mechanical performances, the optimal blending ratio may be between PLA/PMMA/SiO₂ (90/10) and PLA/PMMA/SiO₂ (80/20). The total light transmittance of the PLA/PMMA/SiO₂ composites reaches as high as 91%, indicating a high miscible PLA/PMMA blend. The haze value of the PLA/PMMA/SiO₂ composites is less than 35%. Incorporating nanosilica particles can increase the crystallization sites and crystallinities of the PLA/PMMA/SiO₂ composites with a simultaneous decrease of the spherulite dimension. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42378.     

Mechanical properties of wood-fiber/toughened isotactic polypropylene composites

This study investigates the mechanical properties of wood-fiber/toughened PP composite modified by physical blending with an EPDM rubber to improve impact toughness. Wood-fiber thermoplastic composites were prepared with a modified PP matrix resin, employing high shear thermokinetic compounding aided with maleated PP for the fiber dispersion. The addition of EPDM improved the impact toughness, while it reduced stiffness and strength properties. To compensate the non-plane strain fracture toughness, the specimen strength ratio (R_sb) was adopted as a comparative measure of fracture toughness. The strength ratio increased with the addition of EPDM, while it decreased with increasing wood-fiber concentration. The work of fracture increased with EPDM level except at large wood-fiber concentration. The effectiveness of the impact modification was assessed with the balance between tensile modulus and unnotched impact energy as a function of wood-fiber concentration. EPDM rubber modification was moderately effective for wood-fiber PP composites. The examination of fracture surfaces showed twisted fibers, fiber breakage, and fiber pull-out from the matrix resin.     

Morphologies of polyethylene–ethylene/propylene/diene monomer particles in polypropylene‐rich polyolefin blends: Flake structure

Morphologies of polyethylene–ethylene/propylene/diene monomer (PE/EPDM) particles in 93/7 polypropylene (PP)/PE blends were investigated. SEM micrographs of KMnO₄‐etched cut surfaces and fracture surfaces of the blends revealed the existence of the “flake” structure. In the particles, crystalline PE formations with flake shape, which remain after etching, are called flakes. In addition to the PE‐crystalline flakes, amorphous PE, located between PE crystalline lamellae and EPDM rubber, complement the flake structure. The flakes are usually linked with the PP matrix, as seen in the heptane‐treated cut surfaces. These links, although observed with compatibilized samples, originate from the crystalline nature of PE particles, if no compatibilizer is added. Separately, the morphology of Royalene (consisting of high‐density PE and EPDM rubber, used as a PP/PE compatibilizer) was investigated by low‐voltage scanning TEM. The interaction of the components in the PE/EPDM blends can explain the formation of the flakes and toughening of the PP/PE blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3087–3092, 2003     

Evaluation of PP/EPDM nanocomposites filled with SiO2, TiO2 and ZnO nanofillers as thermoplastic elastomeric insulators

Abstract

Thermoplastic elastomer, which has important characteristics for cable insulation, was developed by melt blending of polypropylene (PP) with ethylene propylene diene monomer (EPDM) at various blend ratios together with SiO₂, TiO₂ and ZnO nanofillers at fixed loading of 2 vol.-%. The influence of EPDM content and the presence of nanofillers in the blend on burning rate, hydrophobicity and dielectric breakdown strength were investigated. Burning rate of PP/EPDM/ZnO was significantly reduced, implying that there was an improvement in fire retardancy with the addition of ZnO nanofillers in the polymer blend. Both SiO₂ and ZnO filled system showed an improvement in hydrophobicity. Furthermore, dielectric breakdown strength showed higher value in EPDM rich blends. In addition, the presence of nanofillers deteriorated the dielectric breakdown strength of PP/EPDM nanocomposites.     

Facile construction of silica-based surface coating onto polypropylene microporous film through dopamine-assisted hydrolysis of tetraethoxysilane

Surface modification with silica-based coating is widely used to attain high performance and construct special functions for thin films. In this paper, dopamine (DA) and tetraethoxysilane (TEOS) were used as initial building blocks to construct a biomimetic hydrophilic and mechanical robust silica-based coating onto polypropylene (PP) microporous film. It was found that the final DA/TEOS coating can be steadily immobilized onto PP film and greatly improve the hydrophilic property of PP film as evidenced by the decreased contact angle. Furthermore, the coating structures were comparatively investigated through one-step synthesis and two-step synthesis of DA and TEOS with a fixed ratio. Interestingly, the one-step synthesized coating possesses a loosely-packed layer with dispersed SiO₂ nanoparticles within polydopamine matrix while the two-step synthesized coating shows a high loading of SiO₂ nanoparticles. As a result, the two-step approach leads to a continuous SiO₂ layer with abundant hydroxyl groups, indicating a better lyophilic property and depressed thermal shrinkage. In addition, the concentric SiO₂ layer results in a significant increase of the tensile strength of PP films.     

PP/PP-g-NH2/纳米SiO2复合材料的非等温结晶

采用示差扫描量热法（DSC）研究了聚丙烯/氨基化聚丙烯/纳米二氧化硅（PP/PP-g-NH₂/SiO₂）复合材料的非等温结晶行为。利用Caze法对结晶动力学进行了分析,Avrami指数n表明纳米SiO₂和PP-g-NH₂的加入改变了PP的结晶成核和生长机理;运用Dobreva法研究了纳米粒子的成核活性,结果表明纳米SiO₂成核活性差,增容剂PP-g-NH₂明显增强其成核活性;采用Friedman法分析了复合材料的结晶有效能垒,研究表明加入纳米SiO₂使PP的结晶有效能垒降低,添加PP-g-NH₂则进一步降低复合体系的结晶有效能垒;当纳米粒子含量为3%时,添加5% PP-g-NH₂能有效提高纳米粒子成核活性,降低复合材料结晶有效能垒。