Compatibilisation of polypropylene–polystyrene blends: Part 1 – Effect of mixing intensity on morphology andrheological properties

Abstract

Propylene copolymer blends have been prepared using a proprietary, in reactor, grafting polymerisation technique, to give two phase materials composed of 70% polypropylene, 20% polystyrene, and 10%polypropylene- graft-polystyrene (PP-g-PS). The present study was carried out to determine the efficiency of PP-g-PS relative to block-copoly(styrene/ethylene–butylene/ styrene) (SEBS) as a compatibiliser for polypropylene–polystyrene blends by measuring rheological properties and examining the morphological structure. Mixing experiments were conducted on a twin screw mixing element evaluator and on a commercial ZSK-30 extruder. Dynamic mechanical analysis was used to characterise the viscoelastic properties of the extruded polymer pellets and transmission electron microscopy was used to examine the morphology of the polymer throughout its processing history, i.e. from carcasses at different stages of the mixing operations to injection moulded specimens. Both the graft copolymer, PP-g-PS, and the black terpolymer, SEBS, were found to enhance the compatibilisation of the blends, but the graft copolymer was found to be more effective. The results also show that the intensity of mixing affects the molecular and morphological structures of the graft and graft–rubber blends, as indicated by the intrinsic viscosity values of the extracted isotactic polypropylene fraction of the blends. This is supported by morphological examination of the graft blend, which showed a phase inversion from co-continuous to dispersed phase morphology during extrusion.     

C/C–SiC composite prepared by Si–10Zr alloyed melt infiltration

A high performance and low cost C/C–SiC composite was prepared by Si–10Zr alloyed melt infiltration. Carbon fiber felt was firstly densified by pyrolytic carbon using chemical vapor infiltration to obtain a porous C/C preform. The eutectic Si–Zr alloyed melt (Zr: 10 at.%, Si: 90 at.%) was then infiltrated into the porous preform at 1450 °C to prepare the C/C–SiC composite. Due to the in situ reaction between the pyrolytic carbon and the Si–Zr alloy, SiC, ZrSi₂ and ZrC phases were formed, the formation and distribution of which were investigated by thermodynamics. The as-received C/C–SiC composite, with the flexural strength of 353.6 MPa, displayed a pseudo-ductile fracture behavior. Compared with the C/C preform and C/C composite of high density, the C/C–SiC composite presented improved oxidation resistance, which lost 36.5% of its weight whereas the C/C preform lost all its weight and the high density C/C composite lost 84% of its weight after 20 min oxidation in air at 1400 °C. ZrO₂, ZrSiO₄ and SiO₂ were formed on the surface of the C/C–SiC composite, which effectively protected the composite from oxidation.     

Preparation of PBT/POE-g-GMA/PP ternary blends with good rigidity–toughness balance by core–shell particles

Compared with poly(butylene terephthalate)/glycidyl methacrylate grafted poly(ethylene–octene) (PBT/POE-g-GMA) binary blends, supertough PBT-based ternary blends with little rigidity loss were successfully obtained by adding rigid polypropylene (PP) into PBT/POE-g-GMA blends to construct core–shell particles during melt blending. The effects of PP content and type on the phase morphology and mechanical properties of the blends were systematically investigated. Theoretical predictions and scanning electron microscopy observation showed that a core–shell structure was formed in PBT matrix with PP as the core and POE-g-GMA as the shell. The mechanical property tests showed that POE-g-GMA and PP had significant synergistic toughening effect. When PP with high melt flow index (H-PP) was used, PBT/POE-g-GMA/H-PP (70/15/15) blends possessed the highest Izod notched impact strength, which was 1.9-fold compared with PBT/POE-g-GMA (70/30) binary blends, while the tensile performance loss was little. The essential work of fracture tests was performed to evaluate the fracture resistance of different samples. The results demonstrated that PBT/POE-g-GMA/PP ternary blends possessed much better resistance to crack propagation than PBT/POE-g-GMA binary blends. The decrease of interparticle distance and the fibrillation of core–shell particles activated intense matrix shear yielding, which was the reason for the high crack resistance of ternary blends. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48872.     

Compatibilising effect of carbon black on morphology of NR–NBR blends

Abstract

It is proposed that a non-polar filler can reduce interfacial energies between polar and non-polar polymers. Experiments have been carried out to test this hypothesis using carbon black as the filler in blends of natural rubber (NR) and a nitrile rubber (NBR) with an acrylonitrile content of 45%. Blends of NR–NBR (70/30) were prepared in an internal mixer with varying amounts of carbon black. The dramatic decrease in domain size on addition of carbon black was nonetheless lower than that predicted. Further experiments showed that the amount of carbon black available at the interface for compatibilisation was influenced by preferential incorporation into the lower viscosity elastomer (NBR). Thus, elastomers of similar viscosity should be added to the mixer prior to the carbon black in order to maximise the amount of ‘free’ unwetted carbon black present when the elastomers are blended together. Blending experiments carried out under these conditions resulted in a morphology close to the prediction based on thermodynamic theory.     

Structure–rheology relationship in complex quaternized polysulfones/solvent/nonsolvent systems

Polymer chains consisting of water-soluble polysulfones with various amounts of ionic chlorine have been prepared via the quaternization reaction of chloromethylated polysulfones with N,N-dimethylethanolamine. Rheological investigations have reflected the importance of electrostatic interactions, hydrogen bonding, and association phenomena from the ternary systems consisting of a proton-acceptor polymer (polysulfones with different ionic chlorine content), a proton-donor solvent (N,N-dimethylformamide), and a proton-donor solvent (methanol). The specific interactions, the polyelectrolyte effect induced by enhanced dissociation of the ionizable groups and mixed solvents’ quality modify the rheological functions, i.e., dynamic viscosity, elastic shear modulus and viscous shear modulus, as well as the thermodynamic parameters obtained from the rheological properties, such as apparent energy of activation and flow activation entropy. These results were correlated with the surface properties of the polysulfonic films formed from solutions in solvent/nonsolvent mixtures.     

Microstructure and properties of ablative C/ZrC–SiC composites prepared by reactive melt infiltration of zirconium and vapour silicon infiltration

C/ZrC-SiC composites with a density of 3.09 g/cm³ and a porosity of 4.8% were prepared by reactive melt infiltration and vapour silicon infiltration. The flexural strength and modulus were 235 MPa and 18.3 GPa, respectively, and the fracture toughness was 7.0 MPa m^1/2. The formation of SiC and ZrSi₂ during vapour silicon infiltration, at the residual cracks and pores in the C/ZrC, enhanced the interface strength and its mechanical properties. The high flexural strength (223 MPa, c. 95% of the original value) after oxidation at 1600 °C for 10 min indicated the excellent oxidation resistance of the composites after vapour silicon infiltration. The mass loss and linear recession rate of the composites were 0.0071 g/s and 0.0047 mm/s, respectively and a fine ablation morphology was obtained.     

Properties of natural rubber/recycled ethylene–propylene–diene rubber blends prepared using various vulcanizing systems

The role of various vulcanizing systems on the curing characteristics, mechanical properties, morphology and dynamic mechanical analysis of natural rubber and recycled ethylene–propylene–diene rubber blends was investigated. Accelerated sulfur-vulcanizing systems (semi-EV and EV), peroxide, and mixed sulfur/peroxide-vulcanizing systems (semi-EV/peroxide and EV/peroxide) were observed and compared. The blends were processed on a two-roll mill, and a fixed amount of carbon black was also incorporated. Amongst the blends, accelerated sulfur-vulcanizing systems exhibited higher torques, state of cure, tensile strength and elongation-at-break, in comparison with the peroxide-vulcanizing system, whereas the tensile modulus, hardness and cross-link density showed lower trend. In the mixed sulfur/peroxide-vulcanizing systems, it showed intermediate behavior to the individual sulfur- or peroxide-vulcanizing systems. This was associated to the interference of peroxide during the cross-linking formation. SEM micrographs of semi-EV-vulcanizing system exhibited more roughness and cracking path indicating that higher energy was required towards the fractured surface. The high cross-link density observed from the swelling study could be verified from the storage modulus (E′) where peroxide vulcanized blends provided a predominant degree of cross-linking followed by semi-EV, semi-EV/peroxide, EV and EV/peroxide-vulcanizing systems, respectively. The glass transition temperature (T _g) depicted at maximum peak of mechanical loss factor (tanδ _max), indicating that semi-EV-vulcanizing system showed highest T _g value. The T _g values can be ordered as semi-EV > peroxide > semi-EV/peroxide > EV > EV/peroxide-vulcanizing systems. The T _g of rubber vulcanizates can be increased due to the restriction of molecular movement such as cross-link density.     

C/C–ZrC composite prepared by chemical vapor infiltration combined with alloyed reactive melt infiltration

A high performance and low cost C/C–ZrC composite was prepared by chemical vapor infiltration combined with zirconium–silicon (Zr: 91.2 at.%; Si: 8.8 at.%) alloyed reactive melt infiltration. The density of the as-received composite is 2.46 g/cm³ and the open porosity is 5%. Due to the reaction between the pyrolytic carbon and Zr–Si alloy in the composite, ZrC and Zr₂Si phases were formed, the formation and distribution of which were investigated by thermodynamics and phase diagram. The as-received C/C–ZrC composite, with the flexural strength of 239.5 MPa, displayed a pseudo-ductile fracture behavior. Ablation properties of the C/C–ZrC composite were tested by a pulse laser. The linear ablation rate was 0.028 mm/s. A ZrO₂ barrier layer was formed on the ablation surface and the composite presented excellent ablation resistance.     

Microstructure and properties of CaO–ZrO2–SiO2 glass–ceramics prepared by sintering

For the development of a new wear resistant and chemically stable glass-ceramic glaze, the CaO–ZrO₂–SiO₂ system was studied. Compositions consisting of CaO, ZrO₂, and SiO₂ were used for frit, which formed a glass-ceramic under a single stage heat treatment in electric furnace. In the sintered glass-ceramic, wollastonite (CaSiO₃) and calcium zirconium silicate (Ca₂ZrSi₄O₁₂) were crystalline phases composed of surface and internal crystals in the microstructure. The internal crystal formed with nuclei having a composition of Ca_1.2Si_4.3Zr_0.2O₈. The CaO–ZrO₂–SiO₂ system showed good properties in wear and chemical resistance because the Ca₂ZrSi₄O₁₂ crystals positively affected physical and mechanical properties.     

Investigation of polyethylene–wax blends by CRYSTAF and SEC–FTIR

Summary Oxidized wax blends with respectively HDPE, LDPE and LLDPE were investigated using CRYSTAF and SEC–FTIR in order to determine the possibility and extent of co–crystallization of the wax with each of these polyethylenes. CRYSTAF shows very little or no co–crystallization of wax with HDPE and LDPE, while there is a strong indication of co–crystallization in the case of LLDPE. SEC-FTIR analyses show co–elution of wax with LLDPE, indicating some chemical interaction between the oxidized wax and LLDPE.     

Effect of processing conditions on the structural morphology of PP–EP/EVA/organoclay ternary nanocomposites

The effect of processing conditions on the morphology of heterophasic PP–EP/EVA/organoclay ternary nanocomposites was examined. The nanocomposites were prepared in a co-rotating twin screw extruder with different screw configurations and incorporation methods. Three different sizes of EVA granules were used. The results obtained by X-ray scattering (WAXD) and electronic microscopy (TEM) showed an increase in d spacing value of the clay associated with the polar interactions between the vinyl acetate of EVA and the surface of the nanoclays. In addition, some chains of the non-polar copolymer PP–EP may have become intercalated into the clay galleries as a result of polymer diffusion induced by shear stress during melt mixing. An increase in surface area of EVA granules resulted in a more homogenous clay dispersion and intercalation. The morphologic changes resulted in an increase in heat distortion temperature (HDT) and flexural modulus of the ternary nanocomposites.     

Study of the phase morphology and toughness in poly (vinyl chloride)/acrylonitrile–styrene-acrylic/styrene–butadiene–styrene ternary blends influenced by interfacial/surface tension

The effect of interfacial interaction on the phase morphology and toughness of poly (vinyl chloride) (PVC)/acrylonitrile–styrene-acrylic (ASA) terpolymer/styrene–butadiene–styrene (SBS) block copolymer ternary blends has been investigated. Water and diiodomethane liquids were used for static contact angle measurements to get surface tension and calculate interfacial tension. A dispersed phase morphology of ASA and SBS in the PVC matrix was predicted by the spreading coefficient theory, which was calculated through interfacial tensions between different polymer pairs. Extraction experiment and scanning electron microscopy were combined to verify this morphology. When the volume fraction of SBS was small, SBS was dispersed in the matrix as droplets and the strong PVC/styrene–acrylonitrile interfacial interaction made up for the poor interfacial adhesion between SBS and PVC. Herein, SBS showed an effective toughening effect on PVC/ASA blends. With the addition of 2.5- and 5-phr SBS, the blends had the highest impact strength of 88.75 kJ/m² at 23 °C and 9.98 kJ/m² at 0 °C, respectively. With the further increase of the SBS content, the diameter of the SBS drops increased largely and the poor interfacial adhesion between SBS and PVC played a leading role, resulting in a sharp decrease in toughness and a sharp ductile–brittle transition. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47721.     

Reactive processing of polyethylene and polyethylene–ethylene/propylene/dicyclopentadiene blends under static and dynamic conditions

Abstract

Dicumyl peroxide induced reactive melt processing of polyethylene (PE) in a shear mix at 170°C in the absence or presence of selected acrylic monomers (acrylic acid, ethyl acrylate, and butyl acrylate) has been studied. The acrylic graft copolymers of PE showed development of higher shear stress compared with the control PE when studied rheologically in a plate and cone viscometer at 160–190°C. All the modified PE products retained the pseudoplastic flow behaviour of PE. Measure of rupture shear parameters and of thixotropic and relaxation behaviour of the different modified PEs and of the control PE were also evaluated and compared. The observed effects and unexpected trends were analysed and interpreted.

The comparative effects of sulphur vulcanisation of polyethylene–ethylene/propylene/dicyclopentadiene terpolymer (PE–EPDM) blends by static and dynamic techniques were also studied using both a conventional curative system and a silane curative system. Rheometric studies indicated development of a co-continuous phase morphology for the 30/70 PE–EPDM blend. For a given blend, cured under given conditions, tensile strength and elongation at break at 25°C were higher for vulcanisates obtained statically than for those obtained dynamically, while the corresponding modulus values followed the opposite trend. The conventional curative usually cured at a higher rate. The property differences from static and dynamic vulcanisation are explained in the light of the differences in the developed morphology.     

Wear resistance of αSiC–TiB2 composites prepared by reactive sintering

The relative wear resistance of αSiC–TiB₂ composites prepared by reactive sintering was investigated on a pin on flat tribometer, in air and in presence of water. Experimental results show that the composite materials are less worn than monolithic SiC. The wear mechanisms in air and water are identified.In air, a protective oxidised debris layer is formed on the composites, whereas roller formation was observed with SiC. In water, the surface of the composites is polished, whereas SiC is worn by fragile ruptures (cleavages).     

Fabrication of Cf/ZrC–SiC composites using Zr–8.8Si alloy by melt infiltration

Cf/ZrC–SiC composites were fabricated by melt infiltration at 1800 °C using Zr–8.8Si alloy and carbon felt preforms. Microstructural analysis showed the formation of both ZrC and SiC phases in the matrix, in which ZrC acted as a main composition of the resulting composites. The results showed that carbon matrix reacted preferentially with Si of Zr–8.8Si alloy, which caused the formation of SiC first and then ZrC. The designed carbon coating by pyrolysis prevented the severe reaction between fibers and the melt. The composites could be more dense and uniform with the bending strength of 53.3 MPa, when preforms had a high open porosity (47.2%) with small size pores (10–40 μm).     

JHH-2E_1型EPDM/PP热塑性弹性体

这种热塑性期性体在高温能塑化成型，常温下又能显示出橡胶的弹性，可以实现塑料化生产．即可注射、挤出、吹塑、压延，用来生产外形复杂、尺寸严格的制品；其级品及边角余料可回收再用并且何以见除硫化工艺及硫化脓庞大的脱硫生产纳税，即减少污染又保证产品质报。它可广泛用于汽车零件、一般工业用零件、软管、电线电览等各个方面．吉化公司研究院研制的川N—2民型热线性狲性体，东采用先进的动态硫化工艺加工而成．具有优良的耐激性。耐候性、耐紫外线及良好的高温性能、电性能、冲击性能、且比重小。有聚烯径树脂良好的热塑掀动性和化…     

Rheology, morphology and tensile properties of reactive compatibilized polyethylene/polystyrene blends via Friedel–Crafts alkylation reaction

Attempts were made to study the effect of reactive compatibilization via Friedel?CCrafts alkylation reaction, using AlCl₃ as a catalyst, on rheology, morphology, and mechanical properties of polyethylene/polystyrene (PE/PS) blends. The results of linear viscoelastic measurements in conjunction with the results of the mixing torque variation indicated that PS showed much more degradation than that of PE in the presence of AlCl₃. It was also found that while for PE-rich blends, the viscosity, and storage modulus increased by reactive compatibilization, they decreased for PS-rich blends. The variation of viscosity and storage modulus for 50/50 blend was found to be dependent on frequency ranges showing the competitive effects of PE?Cg?CPS copolymer formation and PS degradation. The results of morphological studies showed that reactive compatibilization decreased the particle size and particle-size distribution broadness because of in situ graft copolymer formation. Reactive compatibilization enhanced the tensile strength and elongation at break for PE-rich blends. It was demonstrated that there is a close interrelationship between rheology, morphology, and mechanical properties of reactive compatiblized PE/PS blends. It was also demonstrated that rheological behaviors have a reliable sensitivity to follow the structural and morphological changes during compatibilization process, so that, those information can be used to predict the morphology as well as mechanical properties of the blends.     

Optical properties of Nb-doped TiO2 thin films prepared by sol–gel method

In this work, we studied optical properties of pure and Nb-doped TiO₂ synthesized using a sol–gel method and deposited as thin films by spin-coating followed by annealing in air at 500 °C for 1 h. The surface elemental composition was derived from X-ray photoelectron spectra, while structure and surface morphology were investigated using X-ray diffraction and atomic force/scanning electron microscopy. Finally, the optical properties were investigated by means of UV–vis spectrophotometry and spectroscopic ellipsometry.The Nb content was determined from XPS measurements to vary between 1.8 and 4.3 at%. The XRD patterns of the deposited thin films, with a maximum thickness of about 56 nm, showed no diffraction peaks. As proven both by microscopy and spectroscopic ellipsometry studies doping TiO₂ with Nb modified the surface morphology of the samples; the grain size is increasing while the surface roughness decreases with the increase in Nb content. This is accompanied by a decrease in the refractive index and an increase of the extinction coefficient.     

Catalytic oxidation of gas-phase mercury over Co/TiO2 catalysts prepared by sol–gel method

Co/TiO₂ catalysts prepared by sol–gel method were studied for gas-phase mercury oxidation in this paper. Experimental results revealed that the optimal loading of Co was 7.5%, which yielded more than 90% oxidation efficiency within the temperature range of 120–330 °C. The high activity was mainly attributed to the enrichment of well dispersed Co₃O₄. We also found that oxygen performed a key role in mercury oxidation process, while HCl could corrode the oxidized mercury and release it to gas phase. Thereafter, a modified Mars–Maessen mechanism was proposed and the possible simultaneous oxidization of NO and mercury was studied.     

Physical characterization and rheological behavior of polyurethane/poly(ϵ-caprolactone) blends,prepared by solution blending using dimethylacetamide

Blending effects of thermoplastic polyurethane based on polycaprolactone diol, PU (PCL diol), and poly (ϵ-caprolactone) (PCL) on the rheological properties and morphological behavior of the solvent-cast blends were investigated by parallel plate rheometer. The amount of PCL was varied from 20 to 50% by weight. Fourier transform infrared (FTIR) results showed existence of hydrogen bonding in PU/PCL blends. From FTIR, we also found the increase of PCL composition tends to reduction of intermolecular hydrogen bonding and enhancing of microphase separation in blends. Differential scanning calorimetry (DSC) indicated that these blend systems are partially miscible. Based on rheological characterization, decrease can be seen in the moduli, zero shear viscosity and plateau modulus of blends, as compared with net PU. Using Cole-Cole plots and composition dependencies of η₀ and the other viscoelastic functions expressed variation of morphology of blends due to increase of PCL content. Frequency sweep tests on PU/PCL (80/20) at five temperatures showed validity of time-temperature superposition in this blend. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012