Interphase structure development in impact modified PP/Mg(OH)2 composites reactively processed with 1,3‐phenylene dimaleimide

Interphase modification of impact modified isotactic poly(propene) (IMPP)/magnesium hydroxide (Mg(OH)₂) composites, via use of the reactive modifier 1,3 phenylene dimaleimide (BMI) has led to the formation of composites that have strength and toughness more than twice that of the unmodified composite. These significant improvements in properties were found (via response surface analysis, DSC and matrix extraction‐DRIFTS studies) to be due to encapsulation of the filler particles with the elastomeric poly(ethene‐co‐propene) impact modifier phase of the IMPP. Acceptable processing characteristics can be realised together with excellent mechanical properties, via judicious addition of a lubricant (a fatty acid amide/ester blend) to the formulation.     

Investigation of photo‐oxidative effect on morphology and degradation of mechanical and physical properties of nano CaCO3 silicone rubber composites

Photo‐oxidative degradation of treated and untreated nano CaCO₃: silicone rubber composite was studied under accelerated UV irradiation (≥290 nm) at different time intervals. Prolonged exposure to UV leads to a progressive decrease in mechanical and physical properties along with the change in behavior of filler‐matrix interaction. This was due to decrease in cross‐linking density with increase in mobility of rubber chains. Meanwhile, synthesized nano CaCO₃ was modified with stearic acid for uniform dispersion in rubber matrix. The increase in carbonyl (>CO), hydroxyl (? OH), CO₂, and alkene functional groups on the UV exposed surface of treated and untreated nano CaCO₃: silicone rubber composites at different time intervals was studied using Fourier transform infrared (FTIR) spectroscopy. The change in morphological behavior of filler‐matrix interaction after UV exposure was studied using SEM. Overall, the study showed that the treated nano CaCO₃: silicone composites were affected more by UV exposure than untreated nano CaCO₃: silicone composites and pristine composite after UV exposure. This effect was due to peeling of stearic acid from the surface of CaCO₃, which makes the rubber chains slippery and thus separation of filler and rubber chains takes place with initiation of fast‐degradation. Copyright © 2011 John Wiley & Sons, Ltd.     

Effects of polystyrene-encapsulated magnesium hydroxide on rheological and flame-retarding properties of HIPS composites

In this study, polystyrene (PS)-encapsulated magnesium hydroxide (Mg(OH)₂) was successfully prepared by in situ polymerization of styrene on the surface of Mg(OH)₂ in a high-speed mixer. A large amount of PS chemically bonded on Mg(OH)₂ surface was confirmed by means of FT-IR, TGA and SEM. A series of composites of high impact polystyrene (HIPS) were prepared by melt blending in a co-rotating twin-screw extruder. The effects of PS-encapsulated filler on the properties of HIPS composites were studied by SEM, rheology and combustion tests (horizontal burning tests and cone calorimetry). The dispersion and adhesion patterns of PS-encapsulated Mg(OH)₂ in HIPS matrix were investigated through FT-IR and SEM. The experimental results demonstrated that comparing to the composites containing untreated filler, the rheological and flame retardant properties of those containing PS-encapsulated filler were found to be significantly improved. This improvement is mostly attributed to a better dispersion of the encapsulated filler and a strong adhesion between the filler and matrix.     

Structure and mechanical properties of talc‐filled blends of polypropylene and styrenic block copolymers

The structure–property relationships of isotactic polypropylene (iPP)/styrenic block copolymer blends filled with talc were examined by optical and scanning electron microscopy, wide‐angle X‐ray diffraction, and tensile‐ and impact strength measurements. The composites were analyzed as a function of the poly(styrene‐b‐ethylene‐co‐propylene) diblock copolymer (SEP) and the poly(styrene‐b‐butadiene‐b‐styrene) triblock copolymer (SBS) content in the range from 0 to 20 vol % as elastomeric components and with 12 vol % of aminosilane surface‐treated talc as a filler. Talc crystals incorporated in the iPP matrix accommodated mostly plane‐parallel to the surface of the samples and strongly affected the crystallization process of the iPP matrix. The SBS block copolymer disoriented plane‐parallel talc crystals more significantly than the SEP block copolymer. The mechanical properties depended on the final phase morphology of the investigated iPP blends and composites and supermolecular structure of the iPP matrix because of the interactivity between their components. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1255–1264, 2004     

The effect of surface coating of CNTs on the mechanical properties of CF‐filled HDPE composites

Mechanical properties of carbon fiber (CF) and carbon nanotube (CNT)‐filled thermoplastic high‐density polyethylene (HDPE) composites were studied with particular interest on the effects of filler content and fiber surface treatment by coupling agent. Surface‐treated CF‐filled HDPE composites increased their tensile strength and impact strength, which is further increased with the addition of CNT. SEM showed that CNT‐coating‐treated CF‐HDPE composites show better dispersion of the filler into the matrix, which results in better interfacial adhesion between the filler and the matrix. Copyright © 2014 John Wiley & Sons, Ltd.     

Influence of interfacial adhesion and the nonequilibrium glassy structure of a polymer on the enthalpy of mixing of polystyrene-based filled composites

For composites based on polystyrene, the styrene-butadiene copolymer, and polybutadiene filled with various kinds of zinc oxide powder, the enthalpy of mixing is calculated in the entire range of filler contents on the basis of calorimetric measurements with the use of the thermochemical cycle. It is shown that, when the polymer is in excess in the composites based on polystyrene and its copolymer, the enthalpy of mixing is negative, whereas at a high content of the filler, this value is positive. The alternating-sign pattern of the concentration dependence of the enthalpy of mixing is interpreted in terms of the superposition of the negative contribution of the enthalpy of the interfacial-adhesion interaction of a polymer matrix with the filler and the positive contribution due to a gain in the level of nonequilibrium of the glassy matrix near the surface. A thermodynamic model that makes it possible to separate these contributions and to describe the experimental curves of the enthalpy of mixing for the composites is advanced.     

Surface‐modified hydroxyapatite linked by L‐lactic acid oligomer in the absence of catalyst

A new surface modification method of hydroxyapatite nanoparticles (n‐HA) by surface grafting reaction of L ‐lactic acid oligomer with carboxyl terminal (LAc oligomer) in the absence of any catalyst was developed. The LAc oligomer with a certain molecular weight was directly synthesized by condensation of L ‐lactic acid. Surface‐modified HA nanoparticles (p‐HA) were attested by Fourier transformation infrared spectroscopy, ³¹P MAS‐NMR, and thermal gravimetric analysis (TGA). The results showed that LAc oligomer could be grafted onto the n‐HA surface by forming a Ca carboxylate bond. The grafting amount of LAc oligomer was about 13.3 wt %. The p‐HA/PLLA composites showed good mechanical properties and uniform microstructure. The tensile strength and modulus of the p‐HA/PLLA composite containing 15 wt % of p‐HA were 68.7 MPa and 2.1 GPa, respectively, while those of the n‐HA/PLLA composites were 43 MPa and 1.6 GPa, respectively. The p‐HA/PLLA composites had better thermal stability than n‐HA/PLLA composites and neat PLLA had, as determined by isothermal TGA. The hydrolytic degradation behavior of the composites in phosphate buffered saline (PBS, pH 7.4) was investigated. The p‐HA/PLLA composites lost their mechanical properties more slowly than did n‐HA/PLLA composites in PBS because of their reinforced adhesion between the HA filler and PLLA matrix. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5177–5185, 2005     

The oxidation‐treated interface on tribological properties of carbon fibers‐reinforced PTFE composite under oil‐lubricated condition

The effect of air oxidation and ozone surface treatment of carbon fibers (CF) on tribological properties of CF reinforced polytetrafluoroethylene (PTFE) composites under oil‐lubricated condition was investigated. Experimental results revealed that ozone treated CF reinforced PTFE (CF–PTFE) composite had the lowest friction coefficient and wear under various applied loads and sliding speeds compared with untreated and air‐oxidated composites. X‐ray photoelectron spectroscopy (XPS) study of carbon fiber surface showed that, after ozone treatment, oxygen concentration was obviously increased, and the amount of oxygen‐containing groups on CF surfaces was largely increased. The increase in the amount of oxygen‐containing groups enhanced interfacial adhesion between CF and PTFE matrix. With strong interfacial adhesion of the composite, stress could be effectively transmitted to carbon fibers; carbon fibers were strongly bonded with PTFE matrix and large scale rubbing‐off of PTFE was prevented, therefore, the tribological properties of the composite were improved. Copyright © 2009 John Wiley & Sons, Ltd.     

表面改性氢氧化镁阻燃聚丙烯的研究进展

聚丙烯是综合性能良好的五大通用塑料之一,但是其易燃的特点限制了其在很多领域的应用。氢氧化镁(MH)作为一种环境友好型的无机阻燃剂,常被用于阻燃聚丙烯,但是未经改性的MH极性强,易团聚,与基体的相容性差,难以在聚合物基体中均匀分散,在导致阻燃效率低的同时,对复合材料的力学性能也有很大的负面影响,为提高MH在聚合物基体中的界面相容性,往往需要对MH进行表面改性。本文总结了近几年来以表面化学改性、表面接枝改性、微胶囊化改性三种方法改性的MH阻燃聚丙烯的研究进展,并对其下一步的研究方向进行了展望。     

A Links‐Nodes‐Blobs Model for Conductive Polymer Composites

A Links‐Nodes‐Blobs (L‐N‐B) model, based on the fractal and percolation concepts, is used to study the electrically conductive mechanism of conductive filler loaded polymer composites. The change in the conductivity of polymer composites during the mixing process can be explained as the competition between the breakdown of filler aggregates and the diffusion of ingredients of matrix material and impurities onto the surface of the filler. The value of the fractal dimension μ, which is the exponent in the power‐law relationship of the electrical conductivity σ = σ₀·(ϕ – ϕ_c)^μ, is calculated as 1.88. This value is close to the values obtained directly from experiments or from other simulations. The positive temperature coefficient (PTC) behavior in the conductivity of composite material is also explained by this model as the breakdown of the conductive filler network. If the thermo‐expansion induced strain is greater than the apparent on‐set strain ε_onset = mQ + 2 G/2d G·ε_b of the L‐N‐B model, a strong PTC effect would happen.     

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.     

Corrosion resistant performances of alkanoic and phosphonic acids derived self-assembled monolayers on magnesium alloy AZ31 by vapor-phase method

Alkanoic and phosphonic acid derived self-assembled monolayers (SAMs) were formed on magnesium alloy by the vapor phase method. AFM and XPS studies showed that SAMs were formed on Mg alloy. The chemical and anticorrosive properties of the SAMs prepared on magnesium alloys were characterized using contact angle measurements, X-ray photoelectron spectroscopy (XPS), and electrochemical measurements. Water contact angle measurements revealed that, although SA and ISA have the same headgroup to anchor to the magnesium alloy surface, the packing density on the magnesium alloy surface could be considerably different. The contact angle hysteresis of SAMs with a carboxylate headgroup is much larger than that of SAMs with a phosphonic acid group. The XPS O 1s peaks indicated more likely a mix of mono-, bi-, or tridentate binding of phosphonic acid SAM to the oxide or hydroxide surface of the Mg alloy. The electrochemical measurements showed that the phosphonic acid derived SAM had better corrosion resistance compared to alkanoic acid derived SAM. The chemical stability of SAMs modified magnesium alloy was investigated using water contact angle and XPS measurements. The water contact angle and XPS measurements revealed that the molecular density of OP and PFEP on magnesium alloy would be higher than those of SA and ISA on magnesium alloy.     

Effect of GMA polymer compatibilizers on highly filled composites of low density polyethylene/magnesium hydroxide

Functional polymers such as polyethylene grafted glycidyl methacrylate （PE-g-GMA） and ethylene-methyl acrylate-glycidyl methacrylate terpolymer （E/MA/GMA） were used as compatibilizers in the preparation of highly filled composites of polyethylene/magnesium hydroxide（PE/MH）. Comparative studies were performed on the effect of magnesium hydroxide and stearic acid on the interface within polymer and magnesium hydroxide composites. The effect of polymeric compatibilizers on the properties of the composites was studied using tensile and impact tests, torque rheological analysis, differential scanning calorimetry and environmental scanning electron microscopy （ESEM）. The microstructure of highly filled PE/MH composites changed after the addition of functional polymers. The mechanical properties of the composite material increased after compatibilization. The compatibilization processes of PE-g-GMA and E/MA/GMA were different. The grafted polymer was more compatible with polyethylene, which led to a polar polymer phase. In contrast, the tercopolymer tended to adhere to the surface of MH particles.     

Role,effect, and influences of micro and nano‐fillers on various properties of polymer matrix composites for microelectronics: A review

Ever since the discovery of polymer composites, its potential has been anticipated for numerous applications in various fields such as microelectronics, automobiles, and industrial applications. In this paper, we review filler reinforced polymer composites for its enormous potential in microelectronic applications. The interface and compatibility between matrix and filler have a significant role in property alteration of a polymer nanocomposites. Ceramic reinforced polymeric nanocomposites are promising candidate dielectric materials for several micro‐ and nano‐electronic devices. Because of its synergistic effect like high thermal conductivity, low thermal expansion, and dielectric constant of ceramic fillers with the polymer matrix, the resultant nanocomposites have high dielectric breakdown strength. The thermal and dielectric properties are discussed in the view of filler alignment techniques and its effect on the composites. Furthermore, the effect of various surface modified filler materials in polymer matrix, concepts of network forming using filler, and benefits of filler alignment are also discussed in this work. As a whole, this review article addresses the overall view to novice researchers on various properties such as thermal and dielectric properties of polymer matrix composites and direction for future research to be carried out.     

Reinforcement effect of MAA on nano‐CaCo3‐filled EPDM vulcanizates and possible mechanism

Methacrylic acid (MAA) was used as in situ surface modifier to improve the interface interaction between nano‐CaCO₃ particle and ethylene–propylene–diene monomer (EPDM) matrix, and hence the mechanical properties of nano‐CaCO₃‐filled EPDM vulcanizates. The results showed that the incorporation of MAA improved the filler–matrix interaction, which was proved by Fourier transformation infrared spectrometer (FTIR), Kraus equation, crosslink density determination, and scanning electron microscope (SEM). The formation of carboxylate and the participation of MAA in the crosslinking of EPDM indicated the strong filler–matrix interaction from the aspect of chemical reaction. The results of Kraus equation showed that the presence of MAA enhanced the reinforcement extent of nano‐CaCO₃ on EPDM vulcanizates. Crosslink density determination proved the formation of the ionic crosslinks in EPDM vulcanizates with the existence of MAA. The filler particles on tensile fracture were embedded in the matrix and could not be observed obviously, indicating that a strong interfacial interaction between the filler and the matrix had been achieved with the incorporation of MAA. Meanwhile, the presence of MAA remarkably increased the modulus and tensile strength of the vulcanizates, without negative effect on the high elongation at break. Furthermore, the ionic bond was thought to be formed only on filler surface because of the absolute deficiency of MAA, which resulted in the possible structure where filler particles were considered as crosslink points. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1226–1236, 2006     

Enhanced dielectric performance and energy storage of PVDF‐HFP‐based composites induced by surface charged Al2O3

In order to enhance dielectric properties and energy storage density of poly(vinylidene fluoride‐hexafluoro propylene) (PVDF‐HFP), surface charged gas‐phase Al₂O₃ nanoparticles (GP‐Al₂O₃, with positive surface charges, ε’ ≈ 10) are selected as fillers to fabricate PVDF‐HFP‐based composites via simple physical blending and hot‐molding techniques. The results show that GP‐Al₂O₃ are dispersed homogeneously in the PVDF‐HFP matrix and the existence of nanoscale interface layer (matrix‐filler) is investigated by SAXS. The dielectric constant of the composites filled with 10 wt % GP‐Al₂O₃ is 100.5 at 1 Hz, which is 5.6 times higher than that of pure PVDF‐HFP. The maximum energy storage density of the composite is 4.06 J cm^?3 at an electrical field of 900 kV mm^?1 with GP‐Al₂O₃ content of 1 wt %. Experimental results show that GP‐Al₂O₃ could induce uniform fillers’ distribution and increase the concentration of electroactive β‐phase as well as enhance interfacial polarization in the matrix, which resulted in enhancements of dielectric constant and energy storage density of the PVDF‐HFP composites. This work demonstrates that surface charged inorganic‐oxide nanoparticles exhibit promising potential in fabricating ferroelectric polymer composites with relatively high dielectric constant and energy storage. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 574–583     

Preparation and properties of 1,2‐polybutadiene grafting with poly(1,3‐butadiene)‐block‐(dimethylsiloxane)

The development of silica‐filling elastomers with high mechanical performance and good processability is still a great challenge. In this study, we fabricated siloxane‐grafted atactic 1,2‐polybutadiene (1,2‐PB) rubber through grafting poly(1,3‐butadiene)‐block‐(dimethylsiloxane) (PB‐b‐PDMS) onto 1,2‐PB molecular chains by coordination polymerization using a molybdenum (Mo)‐based catalyst system. The PB‐b‐PDMS with active double bonds was synthesized by anionic polymerization. Fourier transform infrared analysis (FTIR), elementary analysis, and GPC‐MALLS‐viscometer analyses verified the incorporation of PB‐b‐PDMS and the grafting structure in the resulting polymer. Scanning electron microscope (SEM), bound rubber testing, and dynamic mechanical analysis demonstrated that the graft‐modification with PB‐b‐PDMS improved silica dispersity in the 1,2‐PB matrix because the incorporation of siloxane groups provided stronger interfacial interaction with silica. Meanwhile, the graft‐modified 1,2‐PB exhibited lower Mooney viscosity, higher tensile strength, and lower heat build‐up than unmodified 1,2‐PB. This concept provides novel inspiration for the preparation of advanced rubber with promoted silica compatibility and mechanical performance.     

Light scattering and transmission studies of nanofiller particulate size,matrix cavitation,and high strain interfacial dewetting behavior in silica‐elastomer composites

The effect of silica nanofiller surface chemistry on compounded particle size and high strain particle dewetting in a semitransparent nanosilica‐filled elastomer composite was determined using backscattered visible light and transmitted light, respectively. The integrated intensities of backscattered light from the samples were collected at various visible wavelengths for thin‐film composites using ultraviolet–visible spectrometer with an integrating sphere. The data revealed strong Rayleigh‐type scattering from compounded filler particles. Size information was extracted and found to broadly correlate with scanning electron microscopy image analysis of fracture surface. Incorporation of a siloxane surface treatment chemical during compounding resulted in a reduced average filler particle size in the cured composite. On extension of the samples, an optical transition was observed only in the filled composites. At high strains, the semi transparent samples displayed an abrupt drop in transparency becoming opaque. This was quantified using a simple light transmission‐sample extension technique. Strain‐induced crystallization was discounted as the cause for the transition by X‐ray diffraction analysis. The onset yield stress for the optical transition was found to be filler surface‐chemistry‐dependent with the siloxane‐treated filler exhibiting a greatly increased onset stress value. These observations were discussed and rationalized in terms of filler particle–matrix dewetting and cavitation at high strains. Matrix–filler dewetting was distinguished from matrix cavitation by comparison with Beer–Lambert behavior derived from unstrained samples. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011.     

The addition of functionalized graphene oxide to polyetherimide to improve its thermal conductivity and mechanical properties

The thermal and electrical conductivity and mechanical properties of polyetherimide (PEI) containing either alkyl‐aminated (enGO) or phenyl‐aminated graphene (pnGO) oxides were studied. A solution casting method was used to prepare functionalized graphene oxide/PEI composites with different filler contents. The introduction of functionalized graphene oxide to the PEI matrix improved the thermal conductivity, electrical conductivity, and mechanical properties. The thermal conductivities of the enGO 3 wt%/PEI and pnGO 3 wt%/PEI composites were 0.324 W/mK and 0.329 W/mK, respectively, due to the high thermal conductivity of the graphene‐based materials and the strong interface adhesion due to the filler surface treatment between the fillers and the matrix. The electrical conductivities of the functionalized graphene oxide/PEI composites were larger than that of PEI, but the electrical conductivity values were generally low, which is consistent with the magnitude of the insulator. The strong interfacial adhesion between the fillers and the matrix led to improved mechanical properties. Copyright © 2014 John Wiley & Sons, Ltd.     

Improving Thermal and Flame Retardant Properties of Epoxy Resin with Organic NiFe‐Layered Double Hydroxide‐Carbon Nanotubes Hybrids

To improve the dispersion of carbon nanotubes (CNTs) and flame retardancy of layered double hydroxide (LDH) in epoxy resin (EP), organic nickel‐iron layered double hydroxide (ONiFe‐LDH‐CNTs) hybrids were assembled through co‐precipitation. These hybrids were further used as reinforcing filler in EP. EP/ONiFe‐LDH‐CNTs nanocomposites containing 4 wt% of ONiFe‐LDH‐CNTs with different ratios of ONiFe‐LDH and CNTs were prepared by ultrasonic dispersion and program temperature curing. The structure and morphology of the obtained hybrids were characterized by different techniques. The dispersion of nanofillers in the EP matrix was observed by transmission electron microscopy (TEM). The results revealed a coexistence of exfoliated and intercalated ONiFe‐LDH‐ CNTs in polymer matrix. Strong combination of the above nanofillers with the EP matrix provided an efficient thermal and flame retardant improvement for the nanocomposites. It showed that EP/ONiFe‐LDH‐CNTs nanocomposites exhibited superior flame retardant and thermal properties compared with EP. Such improved thermal properties could be attributed to the better homogeneous dispersion, stronger interfacial interaction, excellent charring performance of ONiFe‐LDH and synergistic effect between ONiFe‐LDH and CNTs.