Deformation investigation on iPP/SiO2 composites: Influence of stretching temperature and particle size on morphology evolution and crystalline structure of thin films

 In the present work, structure changes during stretching of isotactic polypropylene (emPP) and emPP/silicon dioxide (SiO₂) composites have been investigated systematically. The α-form crystal structure of both iPP and emPP/SiO₂ composites is destroyed and transforms into the mesophase as the samples are stretched at a low temperature (35℃), while stretching at high temperatures (90℃ and 120℃) can restrain the appearance of defects and keep the perfection of crystal structure. FTIR results reveal that the stretching temperatures show no obvious difference of the effect on the orientation of pure iPP, however, the orientation of emPP/SiO₂ composites is greatly changed by the tensile temperature. In the case of micron-sized SiO₂ particles (average particle diameter d>1 μm), the orientation of the composites is lower than that of pure iPP at all stretching temperatures. The above results suggest that the stretching temperature and the SiO₂ particle size have great influence on the structure variation and orientation behavior of emPP/SiO₂ composites.     

Effect of unsaturated hydroxyl-fatty acid modified nano-CaCO3 on the morphological and rheological behavior of PP

A modified nano-calcium carbonate (R-CCR) was prepared by coating a layer of unsaturated hydroxylfatty acid on the surface of CCR powders using a solid state method; the latter were commercial nano-CaCO₃ modified with stearic acid. FTIR studies indicate that the modifier is combined on the surface of CaCO₃. PP/EPDM/nano-CaCO₃ ternary composites were prepared by a melt-mixing method. SEM and TEM were utilized to examine the morphology of the composites. The tensile fractured surface of PP/EPDM/R-CCR showed a fibroid morphology and large-scale yield deformation. The impact fractured surface showed that the amount of cavities in the PP/EPDM/R-CCR system was increased, however their size diminished obviously. R-CCR particles were dispersed uniformly in the PP matrix, and their compatibility was distinctly improved as compared to CCR when the amount of R-CCR was 15 h⁻¹. The tensile strength remained nearly constant (reduced from 27.6 MPa to 27.5 MPa), while the impact strength increased from 9.6 kJ/m² to 15.4 kJ/m² as CCR was replaced by R-CCR. Meanwhile, the bending strength and bending modulus also increased correspondingly. Furthermore, the impact strength of PP/EPDM/R-CCR was maintained at a high level (15.4 kJ/m²), which was more than the sum of that of PP/EPDM and PP/R-CCR (6.6 kJ/m² and 6.1 kJ/m² respectively). This indicates that the R-CCR and EPDM have a significant synergistic toughening effect on PP while maintaining the strength and modulus of virgin PP. Both the storage modulus G′ and loss modulus G″ of PP/EPDM and PP/EPDM/R-CCR composites increase with increasing frequency, but the values of G′ and G″ of the tertiary composite are relatively higher than those of the binary system. The loss factor and viscosity decrease with increasing frequency, but there is little difference between tertiary and binary composites. The apparent viscosity η of the tertiary system containing R-CCR is lower than that of the tertiary system containing CCR and virgin PP. The viscosity of the composites sig-nificantly decreases with increasing shear rate. The mea-sured mechanical properties of the composites indicate that replacing CCR with R-CCR for binary composites could simultaneously enhance the toughness and strength of PP. __________ Translated from Acta Polymerica Sinica, 2008, 4 (in Chinese)     

PP/EPDM/CaCO_3三元复合材料的相结构及力学性能研究

采用以化学键合方式在CaCO3表面包覆上聚丙烯蜡和将改性后的CaCO3先与EPDM复合、再与PP复合的工艺,制备PP/EPDM/CaCO3三元复合材料,以期在PP基体材料中得到EPDM包裹CaCO3的相结构.通过测量三元复合体系中各组分的表面张力,计算各可能组分对之间的界面张力和黏结功,分析三元复合体系中可能的相结构.热力学计算结果表明,三元复合体系中既存在以EPDM为壳、CaCO3为核的"核壳结构",又存在CaCO3与EPDM各自独立分散在PP基体中的结构.电镜照片进一步揭示,在PP/EPDM/改性CaCO3三元复合体系与PP/EPDM/未改性CaCO3三元复合体系中,这两种相结构的比例是不同的,在前者中以核壳结构为主.CaCO3表面性质的不同是产生这一差别的原因.由于这一结构差别的存在,PP/EPDM/改性CaCO3三元复合体系比PP/EPDM/未改性CaCO3三元复合体系具有更好的力学性能.当EPDM用量为8 phr、改性CaCO3用量为15 phr时,三元复合体系的冲击强度达14.25 kJ/m2,是纯PP的3.17倍.     

Design of PP/EPDM/NBR TPVs with tunable mechanical properties via regulating the core-shell structure

In this work, polypropylene (PP)/ethylene-propylene-diene monomer (EPDM)/butadiene acrylonitrile rubber (NBR) TPVs with different EPDM/NBR ratios were prepared by the core-shell dynamic vulcanization. The relationship between the core-shell structure and mechanical properties of the TPVs were thoroughly investigated. The formation of core-shell structure by adding NBR is conducive to the mechanical properties of the TPVs. The ratio of EPDM to NBR has an important effect on the structure and performances of the final products, and there is a critical ratio for this effect change. Transmission electron microscope (TEM), tensile test, reprocessing test, ageing test, rheological behavior test and stress relaxation were used to characterize the morphology and properties of the TPVs in detail. It was found that when the ratio of EPDM/NBR was 2:4, the tensile strength increased by ~14% compared with PP/EPDM TPV without NBR. Meanwhile, the reprocessing properties, rheological characteristics and instantaneous tensile deformation, etc. all exhibited sudden changes at this critical ratio.     

Interaction of two phases in PP/EPDM polymer blend probed by positron annihilation: CONTIN analysis

Positron annihilation lifetime measurements were performed on pure polypropylene (PP), ethylene-propylene-diene monomer (EPDM) rubber, and their blends PP/EPDM with a series of EPDM volume fraction ϕ (= 10–40%). A numerical Laplace inversion technique (i.e., CONTIN algorithm), was employed to obtain the probability distribution functions (PDF) of free-volume radius. We observed that, first, the average free-volume radius in PP/EPDM blends is generally same as that in PP and is much smaller than that in EPDM. Second, the standard deviation σ_R or the width of the free-volume radius PDF in the blend decreases with ϕ in the region of ϕ = 10ndash;30%, and it increases when ϕ increases from 30% to 40%. The difference in the σ_R of the blend and the calculated value σ^c _R according to the simple-mixing rule of PP and EPDM is interpreted by the existence of the two-phase interaction (i.e., the residual thermal pressure and shear stress between PP and EPDM phases in the PP/EPDM blends). The correlation between σ_R, which indicates the interaction of two phases, and the impact strength of PP/EPDM blends was found and discussed. © 1996 John Wiley & Sons, Inc.     

Synergistic effect of DOPO immobilized silica nanoparticles in the intumescent flame retarded polypropylene composites

The synergistic effect of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) immobilized silica (SiO₂‐DOPO) nanoparticles with an intumescent flame retardant (IFR) on the flame retardancy of polypropylene (PP) was investigated by UL 94 vertical tests and limiting oxygen index (LOI) measurements. It was found that the PP/IFR composites (25 wt%) achieved the UL94 V0 grade and LOI increased to 32.1 with an incorporation of 1.0 wt% SiO₂‐DOPO nanoparticles. Based on thermogravimetric analysis, scanning electronic microscopy and rheological analysis, it is speculated that three factors are mainly contributed to the improvement of the flame retardancy. First, the thermal stability of PP/IFR composites was improved by incorporating SiO₂‐DOPO nanoparticles. Second, the presence of SiO₂‐DOPO nanoparticles could induce the formation of a continuous char skin layer during combustion. The compact char layer could effectively impede the transport of bubbles and heat. Third, rheological analysis indicated that SiO₂‐DOPO nanoparticles could increase viscosity of the PP/IFR composites, which was also benefited to increase flame retardancy. Copyright © 2013 John Wiley & Sons, Ltd.     

Simultaneous enhancement of electrical conductivity and impact strength via formation of carbon black‐filler network in PP/EPDM Blends

The electrical conductivity and impact strength of polypropylene(PP)/EPDM/carbon black ternary composites were investigated in this paper. Two processing methods were employed to prepare these 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. To get an optimal phase morphology that favors the electrical conductivity and impact strength, controlling the distribution of CB in PP/EPDM blend was a crucial factor. Thus the interfacial tension and the work of adhesion were first calculated based on the measurement of contact angle, and the results showed that CB tended to be accumulated around EPDM phases to form filler‐network structure. Expectably, the filler‐network structure was observed in PP/EPDM/CB(80/20/3) composite prepared by two‐step processing method. The formation of this filler‐network structure decreased the percolation threshold of CB particles in polymer matrix, and the electrical conductivity as well as Izod impact strength of the composite increased dramatically. This work provided a new way to prepare polymer composites with both improved conductivity and impact strength. Copyright © 2009 John Wiley & Sons, Ltd.     

iPP/HDPE/EPDM三元共混体系的组分分布、相容性和结晶行为

 用DSC、¹³C-NMR、SEM和WAXD等方法研究了IPP/HDPE/EPDM三元共混体系的组分分布、相容性和结晶行为。实验结果表明,EPDM与PE组分的相容性优于与PP组分的相容性,多数EPDM分子链段能够分布在PE组分中;EPDM含量为15％时,共混物相容性最好,SEM照片呈现晶体微区的互连或网络状结构;随EPDM含量增加,总结晶度X_c减小,其中PE组分结晶度X_cE有较大幅度地降低,PP组分结晶度X_cp基本没有变化,这可以根据EPDM和PE、PP之间相容性的差异以及PE、PP两组分在冷却过程中不同的结晶行为来解释。     

Preparation and characterization of CuO/SiO2 and NiO/SiO2 with bimodal pore structure by sol-gel method

CuO/SiO₂ and NiO/SiO₂ with bimodal pore structure were prepared by sol-gel reactions of Tetra-methoxysilane (TMOS) and the respective metal nitrate in the presence of poly (ethylene oxide) (PEO) with an average molecular weight of 10 000 and the catalyst of acetic acid. In this process, the interconnected macroporous morphology was formed when transitional structures of spinodal decomposition were frozen by the sol-gel transition of silica. The addition of copper and nickel into the silica-PEO system had a negligible effect on the morphology formation. In gel formation, it was found that NiO crystalline sizes in the samples increased with decreasing Si/Ni molar ratio. It was considered that PEO interacted with both silica and nickel cations. In the CuO/SiO₂ with the presence of PEO_, CuO crystalline sizes were larger than those of NiO/SiO_2. It was considered that there was no obvious interaction between the Cu cation and PEO, most of the copper ions in wet silica gel were present in the outer solution. They easily aggregated as copper salts in the drying process of wet gel and decomposed into CuO particles in heating. While in the CuO/SiO₂ with the absence of PEO, the Cu was selectively entrapped as small particles in the gel skeleton due to the interaction between Cu aqua complex and silica gel network.     

The distribution coefficient of oil and curing agent in PP/EPDM TPV

The distribution coefficients of oil and curing agent in PP/EPDM TPV were calculated by measuring the melting point of the PP phase using differential scanning calorimetry (DSC). The PP/EPDM TPV was prepared by using a twin screw extruder and a peroxide curing agent was used. The peroxide induces the degradation of PP, resulting in the decrease of T_m. The oil in PP phase also decreases the Tm. Based on the T_m difference among pure PP and PP/EPDM TPV before and after extraction by cylcohexane, the calculated oil distribution coefficient is 0.537. The addition sequence of PP, oil, and curing agent has a significant effect on the T_m and the calculated curing agent distribution coefficient is 0.52. Both of the coefficients are less than 1. Based on the calculation of the two coefficients, a rationale design of thermoplastic vulcanizate (TPV) can be made by proper control of raw materials, addition sequence, and processing parameters. Copyright © 2007 John Wiley & Sons, Ltd.     

Preparation of Cu/SiO2 Catalyst by Solution Exchange of Wet Silica Gel

Structural formation process of Ni/SiO₂ and Cu/SiO₂ catalysts prepared by solution exchange of wet silica gel was investigated. Microstructures of Cu/SiO₂ and Ni/SiO₂ were quite different from each other. In the case of Cu/SiO₂, Cu particles with diameter of ca. 3–5 nm dispersed homogeneously at less Cu content, and the particle size of Cu as well as pore size of silica gel support increased with increasing Cu content. In the Ni/SiO₂, the Ni particles with diameter of ca. 6–10 nm gathered densely to form aggregates in silica matrix resulting in sea-island structure, whereas the size of Ni particle slightly increased with increasing Ni content. The difference in the structure of the metal-silica composites is probably caused by the difference in interaction between silica gel network and metal ions during drying and heating processes.     

Photophysical Properties of a Novel Organic–Inorganic Hybrid Material: Eu(III)-β-Diketone Complex Covalently Bonded to SiO2/ZnO Composite Matrix

In this article, dibenzoylmethane (DBM) was first grafted with the coupling reagent 3-(triethoxysilyl)-propyl isocyanate (TESPIC) to form precursor DBM–Si, and ZnO quantum dot was modified with 3-mercaptopropyltrimethoxysilane (MPS) to form SiO₂/ZnO nanocomposite particle. Then the precursor DBM–Si and the terminal ligand 1,10-phenthroline (phen) were coordinated to Eu³⁺ion to obtain ternary hybrid material phen–Eu–DBM–SiO₂/ZnO after hydrolysis and copolycondensation between the tetraethoxysilane (TEOS), water molecules and the SiO₂/ZnO network via the sol–gel process. In addition, for comparison, the binary hybrid material with SiO₂/ZnO network and ternary hybrid material with pure Si–O network were also synthesized, denoted as Eu–DBM–SiO₂/ZnO and phen–Eu–DBM–Si, respectively. The results reveal that hybrid material with SiO₂/ZnO network phen–Eu–DBM–SiO₂/ZnO exhibits the stronger red light, the longer lifetimes and higher quantum efficiency than hybrid material with pure Si–O network phen–Eu–DBM–Si, suggesting that SiO₂/ZnO is a favorable host matrix for the luminescence of rare earth complexes.     

BRITTLE-DUCTILE TRANSITION OF PP/EPDM/ELASTOMERIC NANO-PARTICLE TERNARY BLENDS

The brittle-ductile transition is a very important phenomenon for polymer toughening. Polypropylene （PP） is often toughened by using rubbers, e.g., ethylene-propylene diene monomer （EPDM） has often been used as a modifier. In this article, the toughening of PP by using a new kind of rubber, known as elastomeric nano-particle （ENP）, and the brittleductile transition of PP/EPDM/ENP was studied. Compared to PP/EPDM binary blends, the brittle-ductile transition of PP/EPDM/ENP ternary blends occurred at lower EPDM contents. SEM experiment was carried out to investigate the etched and impact-fractured surfaces. ENP alone had no effect on the impact strength of PP, however, with the same EPDM content, PP/EPDM/ENP ternary blends had smaller particle size, better dispersion and smaller interparticle distance in contrary to PP/EPDM binary blends, which promoted the brittle-ductile transition to occur earlier.     

Isothermal crystallization of polypropylene/surface modified silica nanocomposites

In the present work, 3-methacryloxypropyltrimethoxy-silane silanized silica(SiO_2-WD70) and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide immobilized silica(SiO_2-WD70-DOPO) nanoparticles were prepared. Silica, SiO_2-WD70 and SiO_2-WD70-DOPO were incorporated into polypropylene(PP) by melt compounding. Differential scanning calorimetry(DSC), X-ray diffraction(XRD) and polarized optical microscopy(POM) were employed to investigate the isothermal crystallization behavior of PP and PP/silica composites. The kinetic constant(kn), and half crystallization time(t1/2) were calculated by Avrami equation,while the surface free energy of folding was calculated by Lauritzen-Hoffman theory. The increased kn, decreased t1/2 and the surface free energy(σe) in the order of PP, PP/SiO_2, PP/SiO_2-WD70 and PP/SiO_2-WD70-DOPO nanocomposites were attributed to the surface modification of silica. XRD indicated that SiO_2-WD70-DOPO addition had no effect on PP crystal structure but accelerated the crystallization rate. POM determined that SiO_2-WD70-DOPO addition promoted the nucleation of PP by inducing a higher nucleation density during isothermal conditions. The surface modified nanoparticle SiO_2-WD70-DOPO might find possible application as a new type of inorganic nano-sized nucleation agent for PP.     

Co或Ni促进的Cu/SiO2-Al2O3催化剂上丙三醇和苯胺气相合成3-甲基吲哚

对丙三醇和苯胺在Co或Ni促进的Cu/SiO2-Al2O3催化剂上气相合成3-甲基吲哚进行了研究.采用N2吸附、氢气程序升温还原(H2-TPR)、电感耦合等离子体(ICP)发射光谱、X射线衍射(XRD)、透射电子显微镜(TEM)、氨程序升温脱附(NH3-TPD)及热重(TG)分析等技术对催化剂进行了表征.结果表明,向Cu/SiO2-Al2O3催化剂加入钴或镍助剂改善了催化剂的催化性能,钴比镍更加有效.在催化剂Cu-Co/SiO2-Al2O3和Cu-Ni/SiO2-Al2O3上,反应第3 h,3-甲基吲哚收率分别达到47%和45%,而且催化剂经过6次再生收率仍能达到44%和42%.各种表征表明,向Cu/SiO2-Al2O3催化剂加入钴或镍助剂能增强铜和载体之间的相互作用,其结果不仅促进了铜粒子在载体表面的分散度,而且有效减少了反应过程中铜组分的流失.另外,加入钴或镍助剂还能减少催化剂的中强酸中心数,从而提高3-甲基吲哚的选择性,并且抑制积炭的形成.此外,钴助剂还能增加催化剂的弱酸中心数,促进3-甲基吲哚的生成.提出了金属铜与弱酸中心共同促进3-甲基吲哚合成的催化反应机理.     

Study on mechanical properties and phase morphology of polypropylene/polyolefin elastomer/magnesium hydroxide ternary composites

In this work, elastomer‐toughened polypropylene (PP)/magnesium hydroxide (MH) composites with ethylene–octene copolymer (POE) were prepared in a twin‐screw extruder and then injection‐molded. The structure, mechanical properties, phase morphology, and rheological behaviors of PP/POE/MH ternary composites were studied. The mechanical properties and fracture behaviors of PP/POE/MH ternary composites are strongly influenced by the incorporation of POE copolymer. The addition of POE causes a significant improvement in the impact strength of the composites, from 3.6 kJ/m² in untoughened composites to 47.4 kJ/m² in PP composites containing 30 phr POE. This indicates that POE is very effective in converting brittle PP composites into tough composites. Conversely, the tensile strength and the Young's modulus of the composites decrease with respect to the PP composites, as the weight fraction of POE is increased to 40 phr. Scanning electron microscopy (SEM) study shows a two‐phase morphology where POE, as droplets, is dispersed finely and uniformly in the PP matrix. The rheological behaviors show that the interfacial interaction in the composites is enhanced with increase in POE content. Interparticle interactions give rise to the formation of interparticle network. Copyright © 2009 John Wiley & Sons, Ltd.     

Compatibilized PP/EPDM/PA6 ternary blends: extended morphological studies

Polypropylene (PP)/polyamide6 (PA6)/ethylene propylene diene monomer (EPDM) (70/15/15) ternary polymer blends compatibilized with maleic‐anhydride‐grafted EPDM (EPDM‐g‐MA) were prepared by melt blending using a twin‐screw extruder (TSE) in different processing conditions (barrel temperature profile, screw speed, and mixing sequence). The microstructures of prepared ternary blends were studied and compared to the predictions of spreading coefficient, minimum relative interfacial energy (RIE), and dynamic interfacial energy phenomenological models. The observed morphologies were somehow different from the model predictions. Copyright © 2011 John Wiley & Sons, Ltd.     

EU-1分子筛的合成及其在正己烷异构化反应中的催化性能

在不同硅铝比(nSiO₂/nAl₂O₃)的合成凝胶(含纯硅凝胶)中引入晶种,合成了纯相的EU-1分子筛。研究了铝源、模板剂和晶种添加量对EU-1分子筛的结晶度、形貌尺寸等的影响;重点研究了不同硅铝比对样品结晶度、晶粒尺寸、酸性、比表面积和孔容等的影响。将合成结果绘制成了纯相EU-1分子筛的合成条件三元图,从三元图可看出,晶种法可显著扩大纯相EU-1分子筛的合成区域。将Pt/H-EU-1用于正己烷异构化反应,结果表明,该催化剂具有优异的正己烷异构化活性及稳定性,对异构烷烃有较高的选择性。     

Solid mechanochemical preparation of core‐shell SiO2 particles and their improvement on the mechanical properties of PVC composites

In this article, a solid mechanochemical route to prepare core‐shell structured particles was introduced. X‐ray photoelectron spectrum, transmission electron microscope and dissolving experimental results indicated the formation of [(inorganic particle)/(elastomer)] core‐shell structured particles. The thermal stable experiments showed that untreated SiO₂ can cause dehydrochlorination of poly(vinyl chloride) (PVC) and discoloration of PVC/SiO₂ composites and the formation of core‐shell structured SiO₂ particles will improve the thermal stability of PVC/SiO₂ composites. The mechanical properties and rheological results showed that the formation of core‐shell structured SiO₂ particles can both improve the mechanical and processing properties of PVC/SiO₂ composite. ACR in PVC/(SiO₂‐PMMA‐ACR) composites acted not only as toughener for PVC matrix but also as cushion breaker if the content of ACR is enough. Meanwhile compared with other SiO₂ particles the formation of core‐shell structured SiO₂ particles can decrease the apparent viscosity, increase the critical shear rate and improve the appearance of extrudes of PVC/SiO₂ composites. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 938–948, 2008     

Brittle–ductile transition of polypropylene/ethylene–propylene–diene monomer blends induced by size,temperature, and time

To study the brittle–ductile transition (BDT) of polypropylene (PP)/ethylene–propylene–diene monomer (EPDM) blends induced by size, temperature, and time, the toughness of the PP/EPDM blends was investigated over wide ranges of EPDM content, temperature, and strain rate. The toughness of the blends was determined from the tensile fracture energy of the side‐edge notched samples. The concept of interparticle distance (ID) was introduced into this study to probe the size effect on the BDT of PP/EPDM blends, whereas the effect of time corresponded to that of strain rate. The BDT induced by size, temperature, and time was observed in the fracture energy versus ID, temperature, and strain rate. The critical BDT temperatures for various EPDM contents at different initial strain rates were obtained from these transitions. The critical interparticle distance (ID_c) increased nonlinearly with increasing temperature, and when the initial strain rate was lower, the ID_c was larger. Moreover, the variation of the reciprocal of the initial strain rate with the reciprocal of temperature followed different straight lines for various EPDM contents. These straight lines were with the same slope. Furthermore, a diagram at critical BDT points in three dimensions (ID, T, and initial strain rate) was given for the PP/EPDM blends. The brittle and ductile zones are clearly shown in this diagram. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1433–1440, 2004