Compatibilization of PUR/PVAC polymer blend by addition of calcium carbonate filler

The influence of untreated and stearic acid surface pretreated calcium carbonate (CaCO₃) nanofiller (U1 – untreated CaCO₃ and U1S2 – stearic acid treated CaCO₃) on the properties of polyurethane/poly(vinyl acetate) (PUR/PVAC) polymer blends was investigated. Adhesion between fillers and polymers in the polymer blend composite, and filler position in regard to the polymer phases, are predicted on the basis of calculated adhesion parameters and wetting factor ωa of PUR, PVAC, U1, and U1S2. U1 is located in the PUR matrix phase and U1S2 is located at the interface between matrix PUR domain and dispersed PVAC domain. Polymer blend composites with predominant U1S2 showed lower tensile strength and elongation compared to these of polymer blend composites with predominant U1 mainly due to the fillers' different surface properties, which confirmed that the mechanical properties of polymer blend composites were dependent on overall system morphology rather than the filler location. POLYM. COMPOS. 37:1274–1281, 2016. © 2014 Society of Plastics Engineers     

Dispersion of fillers and the electrical conductivity of polymer blends filled with carbon black

Dispersion state of carbon black(CB) was studied in polymer blends which are incompatible with each other. It was found that CB distributes unevenly in each component of the polymer blend. There are two types of distribution. (1) One is almost predominantly distributed in one phase of the blend matrix, and in this phase fillers are relatively homogeneously distributed in the same manner as a single polymer composite. (2) In the second, the filler distribution concentrates at interface of two polymers. As long as the viscosities of two polymers are comparable, interfacial energy is the main factor determining uneven distribution of fillers in polymer blend matrices. This heterogeneous dispersion of conductive fillers has much effect on the electrical conductivity of CB filled polymer blends. The electrical conductivity of CB filled polymer blends is determined by two factors. One is concentration of CB in the filler rich phase and the other is phase continuity of this phase. These double percolations affect conductivity of conductive particle filled polymer blends.     

Morphology prediction of ternary polypropylene composites containing elastomer and calcium carbonate nanoparticles filler

In this work, the morphology was studied in ternary composites of polypropylene (PP) with nanosized calcium carbonate (nano‐CaCO₃) fillers and elastomer inclusions and the thermodynamic consideration was used to analyze the formation of phase structure of the composites. The wetting coefficient (ω_a), interfacial tension (γ_AB), and work of adhesion (W_AB) were calculated to predict dispersion state of nano‐CaCO₃ fillers. A comparison of the prediction and SEM analysis was given. The results show that three types of phase structures were formed: an encapsulation of the filler by elastomer, a separate dispersion of the filler and elastomer, and a particular structure of the filler at the PP/elastomer interface. The predictions by ω_a were all successfully supported‐up by SEM analysis and the predictions by W_AB were however trustless. Both γ_AB and W_AB can predict a separate dispersion or an encapsulation phase structure, but they were not available for the particular structure of the filler at the PP/elastomer interface. ω_a was competent and favored for the prediction of all three types of morphology among the three parameters. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1578–1584, 2007     

Use of Flory–Huggins parameters in the characterization of polymer–filler compositions

Any quantitative information on the strength of interactions between an inorganic filler and polymer is substantial for the future application of the composite. The magnitude of adhesion of two phases may be deduced from results collected by various experimental techniques. A Flory–Huggins interaction parameter (χ₂₃^′) was earlier successfully used in the characterization of polymer blends. We propose to express the magnitude of modified filler/polymer interactions by using χ₂₃^′. It was calculated from retention data of test solutes during an inverse gas chromatography (IGC) experiment. IGC is an extension of conventional gas chromatography in which a nonvolatile material to be investigated is immobilized on a column. Parameters determined during IGC experiments may be successfully used in the characterization of polymers and their blends, composites, fillers, and other materials and the quantification of the interactions between the components of polymer mixtures, including the interactions between polymeric components and filler surfaces. Here this method is applied to the characterization of a series of poly(ether urethane)/modified carbonate–silicate filler systems containing different amounts of a filler (5, 10, and 20 wt %). The possibilities and limitations of the IGC method are shown. The usefulness of some methods for minimizing the Δχ effect (the dependence of χ₂₃^′ on the type of test solute) is examined and discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Mechanical and morphological properties of lyocell blends: Comparison with lyocell nanocomposites (I)

The mechanical properties and morphologies of polyblends of lyocell with three different fillers are compared. Poly(vinyl alcohol) (PVA), poly(vinyl alcohol‐co‐ethylene) (EVOH), and poly(acrylic acid‐co‐maleic acid) (PAM) were used as fillers in blends with lyocell produced through solution blending. The variations of their properties with polymer matrix filler content are discussed. The ultimate tensile strength of the PVA/lyocell blend is highest for a blend lyocell content of 30 wt %, and decreases as the lyocell content is increased up to 40 wt %. The ultimate tensile strengths of the EVOH/lyocell and PAM/lyocell blends are highest for a lyocell loading of 20 wt %, and decrease with the increasing filler content. The variations in the initial moduli of the blends with filler content are similar. Of the three blend systems, the blends with PVA exhibit the best tensile properties. Lyocell/organoclay hybrid films were prepared by the solution intercalation method, using dodecyltriphenylphosphonium–Mica (C₁₂PPh‐ Mica) as the organoclay. The variation of the mechanical tensile properties of the hybrids with the matrix polymer organoclay content was examined. These properties were found to be optimal for an organoclay content of up to 5 wt %. Even polymers with low organoclay contents exhibited better mechanical properties than pure lyocell. The addition of organoclay to lyocell to produce nanocomposite films was found to be less effective in improving its ultimate tensile strength than blending lyocell with the polymers. However, the initial moduli of the nanocomposites were found to be higher than those of the polyblend films. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

The effect of interface characteristics on the static and dynamic mechanical properties of three‐component polymer alloys

The effect of interfacial characteristics on the structure‐property relationships of ternary polymer alloys and blends comprising polypropylene (PP), ethylene‐vinyl alcohol copolymer (EVOH) and glass beads (GB) or fibers (GF) was investigated. The systems studied were based on a binary PP/EVOH immiscible blend, representing a blend of a semi‐crystalline apolar polymer with a semi‐crystalline highly polar copolymer. The ternary systems studied consisted of filler particles encapsulated by EVOH, with some of the minor EVOH component separately dispersed within the PP matrix. Modification of the interfacial properties was done using silane coupling agents for the EVOH/glass interface and compatibilization using a maleic anhydride grafted PP (MA‐g‐PP) for the PP/EVOH interface. Both glass fillers increased the dynamic modulus and decreased the damping of the neat polymers and of their binary blends, especially in the rubbery region. GF has a more profound effect on both the modulus and the damping. Glass surface treatments and compatibilization have only a marginal effect on the dynamic mechanical behavior of the ternary blends. Yet, compatibilization shifted the polymers' T_gS to higher temperatures. Both glass fillers increased the elastic modulus of the binary blends, where GF performed better than GB as a reinforcing agent. GF slightly increased the strength of the binary blends while, GB reduced it. Both fillers reduced the ductility of the binary blends. The blends' mechanical properties were related to the morphology and their components' crystallinity. The compatibilizer increases both stiffness and strength and reduces deformability.     

Preparation and properties of composite mineral powders

Mineral powders such as ground calcium carbonate (GCC) and wollastonite are widely used as fillers in plastics, rubber, paper, paints and other fields. The interface compatibility between the polymer matrix and the mineral particles is relatively weak, both because of the smooth cleavage surface and the sharp particle edges formed during pulverizing. It is beneficial therefore to modify the surface properties of mineral powders before they are used in a polymer composite. In this paper, we report the successful preparation of composite mineral particles, coated by nanoparticles of calcium carbonate of 20-100 nm particle size, by chemical reaction using the Ca(OH)₂-H₂O-CO₂ system. The degree of nanoparticle coverage can reach 100% if the operating parameters are effectively controlled, and the specific surface area can be increased to three times the value before modification. Mechanical testing of polypropylene containing composite wollastonite powder as a filler shows an increase in the impact strength of 65% compared to similar samples prepared using conventional filler powder.     

Nanoscopic properties of silica filled polydimethylsiloxane by means of positron annihilation lifetime spectroscopy

Positron annihilation lifetime spectroscopy (PALS) was performed on a series of polydimethylsiloxane (PDMS)/fumed silicon dioxide (SiO₂) composites at temperatures between −185 and 100 °C to study the effect of filler content and filler particle size on the free volume properties and the positron annihilation characteristics. The glass transition behavior of the PDMS/SiO₂ composites was determined with differential scanning calorimetry. A clear influence on the o-Ps lifetime (τ₃) in the polymer upon addition of nano-sized fumed SiO₂ was observed at all temperatures. The observed o-Ps lifetime behavior was related to filler content and filler particle size. A transition in the temperature dependence of the o-Ps lifetime was observed close to −35 °C above which temperature PDMS exhibits long o-Ps lifetimes. A relationship between τ₃ and the surface tension, equivalent to the behavior of ordinary molecular liquids was observed in this temperature region. The o-Ps yield was strongly reduced in the crystallization region and by addition of SiO₂. The reduction due to filler addition did, however, in the case of nano-sized SiO₂ not follow a linear relationship with filler weight, which was observed for micron-sized fillers. The nonlinear relationship between filler weight and o-Ps yield could be due to out-diffusion of positrons and/or o-Ps from the filler particles to the matrix.     

Influence of filler size and concentration on the low and high temperature dielectric response of poly(vinylidene fluoride) /Pb(Zr0.53Ti0.47)O3 composites

Poly(vinylidene fluoride)/Pb(Zr0.53Ti0.47)O3([PVDF]1 ? x/[PZT]x ) composites of volume fractions x and (0?C3) type connectivity were prepared in the form of thin films. The films were prepared by solvent casting with PZT powder of 0.84, 1.86, and 2.35???m average size with filler contents up to 40?% volume. The crystalline phase of the polymer matrix was the nonpolar ??-phase and the polar ??-phase. Dielectric measurements were performed in order to evaluate the influence of the filler size and content as well as the effect of the polymer matrix in the overall response of the material. No nucleation effect of any of the phases was observed for the used fillers. The spherulitic structure of the pure ??-PVDF and the characteristic porosity of the ??-phase material are destroyed for high PZT volume fractions. The inclusion of ceramic particles in the PVDF polymer matrix increases the complex dielectric constant of the composites independently of the PVDF polymer matrix. The dielectric properties of the composites are mainly affected by the amount of the ceramic particles. With respect to the relaxation processes of the polymer, the activation energy of the ??_a-relaxation increases and the glass transition temperature decreases with increasing particle size and content. The high-temperature conductivity decreases with increasing filler content and there is an important contribution of the Maxwell-Wagner-Sillars effect to the overall dielectric response.     

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.     

Crack-free silicate bioceramics from preceramic polymers

As a case study, the present paper illustrates an innovative processing method employing a preceramic polymer containing different fillers, which can be used to manufacture various ceramic components for biomedical applications. Crack-free wollastonite (CaSiO₃) ceramics were successfully produced, with high phase purity, after heating at 900°C in air starting from a silicone resin containing CaCO₃ micro-sized particles as ‘active filler’. As ‘passive filler’, wollastonite preceramised powders as well as commercially available wollastonite fibres were added. Their presence reduces the gas evolution occurring due to the decomposition of the calcium carbonate active filler and the polymer-to-ceramic conversion, reducing the stresses that generate in the component during heating. The resulting samples exhibited improvements in terms of the morphology and the mechanical strength, with respect to samples not containing any passive fillers, without significant modification of the final phase assemblage.     

Enhanced fibrillation of LCP by CaCO3 whisker in polysulfone matrix through increasing elongational stress

Induced by different fillers, various hydrodynamic effects enhance the fibrillation of liquid crystalline polymer (LCP) in in situ hybrid composites. Through choosing CaCO₃ whisker as the filler and polysulfone (PSF) as the matrix, the effect of the filler size and the affinity between components on the morphological evolution of LCP droplets has been investigated. In contrast to the spherical or ellipsoidal droplets of LCP formed in binary PSF/LCP blends, the fibrillation of LCP was promoted by the introduction of whisker particles in all ternary blends at shear rates studied. The analysis of the flow field indicated that the predominant factors promoting the fibrillation of LCP were the vortex enhanced and elongational stress increased by the whisker in the converging flow area at the entrance of capillary, rather than the viscosity ratio and capillary number.     

Electrically conductive polymer composites and blends

Increasing utilization of the electrical properties of polymeric blends and composites has prompted our renewed interest in developing a general working relationship which can explain the electrical properties of polymer composites and blends in terms of processing characteristics, morphology, and compositions. Here, we restrict our attention to the following two-component systems: (1) two component systems with conductive particulate inclusions (e.g. carbon black) embedded in a continuous polymeric matrix, and (2) two component polymer blend systems with one conductive polymer (e.g., polyether copolymer) dispersed in another continuous polymeric matrix. The following processing aspects related to the electrical property of particulate filled composites are discussed: (1) critical concentration of rigid conductive fillers, ?_c, and (2) redistribution of conductive fillers upon processing. An equation based on the crowding factor of concentrated suspension rheology and Janzen's particle contacts percolation is proposed to describe the relationship between ?_c, and the maximum packing fraction of conductive fillers. The relationship is used to explain the influence of particle morphology on conductivity, and the conductivity difference in the high shear and the low shear region of a processed polymer composite part. Furthermore, some qualitative guidelines for blending a low conductivity polyether copolymer to achieve an overall balance of antistatic and mechanical properties of polymer blends are also discussed.     

Uneven distribution of nanoparticles in immiscible fluids: Morphology development in polymer blends

The present review aims at summarizing the current knowledge on how solid nanoparticles organize in polymer blends. First, the behavior of low viscosity fluid emulsions containing solid colloidal particles is briefly presented. By contrast with polymer blends, they have been the subject of intensive studies for a long time, with both applicative and comprehensive objectives. High viscosity fluid emulsions like polymer blends loaded with nanofillers have received less attention until the recent enthusiasm about nanotechnology and more specifically polymer nanocomposites. Some similarities and differences between both types of emulsions are highlighted. The solid particles are well known to distribute unevenly in those types of complex fluids and the factors that determine their distribution in polymer blends are discussed. A particular emphasis is given on the competition between thermodynamic wetting of the solid by the polymeric phases and kinetic control of the filler localization directly linked to the rate of the mixing process. This aspect is believed to be a specificity of filled polymer blends and is known to have a drastic and sometimes predominant effect on particle localization. It explains that finely tuned morphologies can be obtained where the particles do not occupy their equilibrium position.     

The influence of filler treatment on the properties of TPU/PP blends: I. Thermal properties and stability

Commercially available organosilane (3‐glycidoxypropyltrimethoxysilane (GPTMS)) coupling agent was used to treat talc in order to improve the affinity relative between the filler and the polymer in composites as well as filler and polymer in the thermoplastic polyurethane/polypropylene (TPU/PP) blends (talc content was 5 wt%). The talc particles were first modified with GPTMS and then introduced into TPU, PP as well as TPU/PP blends with different weight ratios of polymers using blending method and subsequently injection molded in a hydraulic press. The aim was to report the effect of silane coupling agent on the thermal and morphological properties of talc filled composites and blends. The results showed that the thermal properties of the TPU, PP composites and TPU/PP blends were improved with the addition of silane treated talc (higher melting (T_m), crystallization (T_c) temperatures and degree of crystallinity (χ_c)). The glass transition temperature (T_g) obtained by dynamic mechanical analysis (DMA) of the TPU soft segments in TPU/PP blends increased with the addition of untreated and silane treated talc due to lower mobility of the soft segments in TPU and better miscibility of TPU and PP. TPU/PP blends with the silane treated talc show better thermal stability than the TPU/PP blends with untreated talc. POLYM. ENG. SCI., 55:1920–1930, 2015. © 2014 Society of Plastics Engineers     

The influence of the dispersed phase on the morphology,mechanical and thermal properties of PLA/PE‐LD and PLA/PE‐HD polymer blends and their nanocomposites with TiO2 and CaCO3

This research investigated the impact of different processing temperature (extrusion at 160°C and 180°C) and the influence of the TiO₂ and CaCO₃ fillers on morphology, mechanical, and thermal properties of polylactide (PLA) blended with low‐density polyethylene (PE‐LD) and high‐density polyethylene (PE‐HD) in 90/10 weight ratio. The impact of the particle size of the filler was also examined with the three types of TiO₂ filler. It has been shown that the different processing temperature has no significant impact on the morphology, mechanical, and thermal properties of PLA/PE‐LD 90/10 and PLA/PE‐HD 90/10 polymer blends. It has also been shown that better phase interaction is not the crucial factor for the improvement of the mechanical properties but the domain size distribution of the dispersed phase within the matrix and the dispersion of the filler are. Samples with a narrow size distribution of the dispersed phase domain (5 to 10 μm) with the higher portion of larger domains that are uniformly distributed within the polymer matrix showed best mechanical properties. POLYM. ENG. SCI., 59:1395–1408 2019. © 2019 Society of Plastics Engineers     

Influence of organic fillers on rheological behavior in phenol-formaldehyde adhesives

Phenol-formaldehyde resoles (PF) formulated with wheat flour and organic fillers have long been established for the manufacture of veneer-based wood-composites, and yet much remains unknown about these complex fluids. The rheology of PF/filler formulations was studied as a function of filler type and particle size. Corn cob (Zea mays) residue fillers behaved differently from those made from alder bark (Alnus rubra) and walnut shell (Juglans regia). It was shown that viscoelastic network structures formed within the liquid formulations as a function of shear history, filler type, and filler particle size. The precise nature and origin of these effects is unknown but could involve disintegration of filler particle aggregates on a non-colloidal scale, and/or colloidal effects within the liquid PF medium. In the latter case colloidal structures could form among associated PF chains and also from proteins, polysaccharides, and lignins that leach from wheat flour and filler particles. Relative to alder bark and walnut shell, the unique behavior of corn cob residue was discussed with respect to chemical composition. Many implications for impact on industrial practice are feasible and should be the subject of future research.     

Effect of loading-rate on fracture micromechanism of methylmethacrylate-butadiene-styrene polymer blend

Methylmethacrylate-butadiene-styrene (MBS) polymer blends having two different types of rubber particle distribution, monomodal and bimodal, were prepared, and their fracture properties and fracture mechanisms were investigated under quasi-static and impact loading. A fracture property, maximum J-integral J_max, was evaluated at both loading-rates, and it was shown that J_max values of the bimodal MBSs are much greater than that of the monomodal with small particles, and slightly better than that of the monomodal with large particles. Thick damage zones were observed in the crack-tip regions in the bimodal and monomodal with large particles, indicating larger energy dissipation during fracture initiation than in the monomodal with small particles in which damage zone is much thinner. TEM micrographs exhibit that extensive plastic deformation under quasi-static rate and multiple craze formation under impact loading rate are the primary toughening mechanisms in the bimodal MBS blends. By assessing both fracture properties and transparency, the bimodal blend with blend ratio: 2.5/7.5 (=140 nm/2.35 μm; total rubber particle content is 10 wt%) was proved to show the best performance as MBS polymer blend with satisfiable transparency and high fracture resistance.     

Controlled CaCO3 stearate pre-treatment effects on the interphase adhesion in filled SAN/EPDM blend

Calcium carbonate (CaCO₃) fillers pre-treated with the increased amount of stearate were used in order to tune the surface energy for a selective filler migration to the interface in immiscible styrene-acrylonitrile/ethylene–propylene–diene (SAN/EPDM) polymer blends. Various models were used in order to predict the filler accommodation at the blend interface when the interfacial tension becomes low and the wettability is good. The results showed that under optimal thermodynamic conditions, the filler might act as a compatibilizer and significantly improve the blend morphology. The coarse morphology of the initially immiscible SAN/EPDM changed into a fine blend morphology with the addition of the selected CaCO₃ fillers with optimal surface energy. Due to the problem with filler agglomeration of initially nanosized CaCO₃ fillers, we used masterbatch (MB) compositions for the blend preparation in order to get the better filler distribution. In this paper, the comparison between two types of MB compositions based on SAN and/or EPDM as a surplus phase with the selected filler was made considering the model predictions and its effects on the blend morphology and properties. In the case of using MB(EPDM) in blend preparation, the fine blend morphology resulted in improved mechanical and thermal properties, while with MB(SAN) the coarse blend morphology and worsened properties illustrated the opposite effect.