Morphology, morphology development and mechanical properties of polystyrene/polybutadiene blends

Polystyrene/polybutadiene (PS/PB) blends with different plastic/rubber ratios were prepared by melt mixing. A detailed investigation on phase morphology development of 30/70 wt.% PS/PB blends as a function of processing conditions was quantitatively analyzed. Morphology is developed at the initial stages of mixing. Suitable blending conditions resulting in optimum phase morphology were obtained at 180 °C, 60 rpm and at 8 min mixing time. Phase morphologies of the blends were also studied as a function of composition. Mechanical properties of the blends were measured. Attempts were made to correlate the morphologies with the properties. Parallel-Voids model has been applied to characterize phase morphology of these blends.     

Preparation of POE/PS blends with fine particle sizes by diffusion and subsequent polymerization of styrene in POE pellets

Ethylene-α-octene copolymer(POE)/polystyrene(PS) blend pellets with fine particle sizes were prepared by diffusion and subsequent polymerization of styrene in POE pellets through a one-pot procedure.The effects of the amounts of styrene and BPO on PS content,monomer efficiency and monomer conversion were investigated.The blend pellets were characterized by Micro-FTIR and FESEM,showing homogeneous diametrical distributions of PS and particle size.After melt-processing into rods,the average particle sizes are almost doubled,but still in submicron scale.Compared to neat POE rods,the blend rods with PS content higher than 15% exhibit improved tensile modulus and tensile strength without significantly losing ductility,being attributed to the small sizes,complex nature of particles and the existence of POE-g-PS copolymer that result in good interfacial adhesion.POE/PS pellets were compared with the previously reported PP/PS pellets,and the differences between the two systems are attributed to the different morphology of the two matrices: POE is completely amorphous at the diffusion and polymerization temperature,while i PP is semicrystalline.Without efficient impediment of the crystal lamellae in POE pellets,styrene diffuses easily in POE pellets.     

Ternary blends based on poly (ethylene-naphthalate)/glass fibers/nitrile rubber: Preparation,properties and effect of dynamic vulcanization

This work studied the possibility of utilizing nitrile rubber (NBR) to modify the impact properties of poly (ethylene-naphthalate) (PEN). The PEN/NBR ratio used changed from 100/0 to 60/40. At the same time, glass fibers (GF), 40% weight of the PEN component, were used to reinforce the blends to compensate for the loss of mechanical properties of PEN by incorporation of NBR. The results showed that the impact strength of the PEN/GF/NBR blend (PEN/NBR = 60/40) was increased up to 27.6J/m, nearly 5 times higher than that of the neat PEN. Meanwhile, the tensile strength and flexural strength were still maintained at as high as 66.1 MPa and 98.2 MPa, respectively. Dynamic vulcanization further improved the mechanical properties of the PEN/GF/NBR blends, which provided routes to the design of new PEN/elastomer blends. Other properties of the PEN/GF/NBR blends were also investigated in terms of morphology of fractured surface, dynamic mechanical behavior, thermal stability and crystallization, by scanning electron microscopy (SEM), dynamic mechanical analysis (DMA), thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively.     

Recycling of ABS and PC from electrical and electronic waste. Effect of miscibility and previous degradation on final performance of industrial blends

The aim of this work, within the framework of polymer recycling, is to upgrade waste from electrical and electronic equipment. Blends of the two major residues were prepared via a melt blending process. These are ABS consisting of a SAN thermoplastic matrix with a dispersed elastomeric (polybutadiene rubber) component and polycarbonate (PC). The effect of partial miscibility and previous degradation levels was investigated. Mechanical characterization of ABS/PC systems was carried out to determine the optimum composition range. Previous degradation levels of the two wastes were investigated by FTIR and little degradation was found on ABS due to the presence of a polybutadiene rubber which is more sensitive to thermo-oxidative processes but no significant degradation was found on PC. Differential scanning calorimetry (DSC) tests demonstrated certain miscibility between the two components by identifying two glass transition temperatures. This partial miscibility, together with the small degradation of the elastomeric component, contributes to a low interaction promoting a decrease on mechanical performance. Scanning electron micrographs (SEM) showed the system morphology and certain lack of adherence along SAN/polybutadiene interface related to degradation of polybutadiene spheres which act as stress concentrators. The use of the equivalent box model (EBM) allowed to quantify the interaction level by determining an interaction/adherence parameter “A”, which turned to be lower than 1 and corroborated the lack of interaction.     

Structure and mechanical properties of blends of poly(ether imide) and an amorphous polyamide

Biphasic poly(ether imide)/poly(trimethyl hexamethylene terephthalamide) blends were obtained by injection moulding through the full composition range both with and without previous extrusion mixing. The extruded blends showed an improved performance, as the T_gs of the two amorphous phases changed and the changes were larger than those of directly injected blends. The T_g changes indicate the presence of the two components in the two phases of the extruded blends. The consequent low interfacial tension is proposed as the reason for the observed generally fine particle size (typically 0.3 μm). Both characteristics led to mostly ductile materials. The modulus of elasticity and the yield stress were slightly below those predicted by the rule of mixtures. As this was due to a lower orientation in the blends, both properties could improve through a change of the processing parameters. The increase in impact strength over that of pure PEI, and particularly, the sudden processability increase (35% torque decrease) upon a-PA addition, led to compatible blends that, as in the case of the 90/10 composition, could be a polymeric material alternative to unmodified PEI.     

Mechanical and fracture behavior of polypropylene/poly(ethylene-co-vinyl alcohol) blends compatibilized with ionomer Na

In this work the deformation and fracture behavior of PP/EVOH blends compatibilized with ionomer Na⁺ at room and low temperature was studied. Uniaxial tensile tests on dumb-bell samples and fracture tests on single-edge notched bending (SENB) specimens were performed for 10 wt.% and 20 wt.% EVOH blends with different ionomer content at 23 °C and −20 °C. The incorporation of EVOH to PP led to less ductile materials in tension as judged by the lower values of the ultimate tensile strain displayed by all PP/EVOH blends in comparison to neat PP. In contrast, the ionomer Na⁺ addition partially counteracted this effect. The compatibilizing effect of ionomer Na⁺ was also evident in fracture results since higher values of the fracture parameter were obtained for the ternary blends. SEM observations also confirmed this effect. On the other hand, PP/EVOH blends exhibited different fracture behavior with test temperature. All blends showed “pseudo stable” behavior at room temperature characterized by apparently stable crack growth that could not be externally controlled. On the contrary, blends behaved as semi-brittle at −20 °C with some amount of stable crack growth preceding unstable brittle fracture. Finally, irrespectively of the temperature or the ionomer content all PP/EVOH blends exhibited more ductile fracture behavior with a higher tendency to stable crack propagation than neat polypropylene.     

Mechanical and fire retardant properties of EVA/clay/ATH nanocomposites - Effect of particle size and surface treatment of ATH filler

Mechanical and flame retardant properties of ethylene vinyl acetate (EVA) copolymer/organoclay/alumina trihydrate (ATH) nanocomposites have been studied. ATH with different particle sizes, ATH1 (2.2-5.2 μm) and ATH2 (1.5-3.5 μm), and three different surface treatments, uncoated, fatty acid coated and silane coated, have been used. A synergistic effect was observed in EVA/organoclay/ATH nanocomposites with the total heat evolved (THE) and the heat release rate (HRR) lower than that of EVA/ATH composite. It was also found that mechanical and flame retardant properties are affected in different ways by the particle size and the surface treatment of ATH fillers. Improvements in tensile and flame retardant properties were observed in nanocomposites when uncoated ATH fillers and fatty acid coated ATH2 filler were used. On the other hand, silane coating on ATH1 and ATH2 improves limiting oxygen index (LOI) and leads to higher t_ignition and the best char stability after cone calorimeter test.     

Blends of propylene-ran-ethylene and propylene-ran-(1-butene) copolymers: Crystal superstructure and mechanical properties

Blends of isotactic propylene-ran-ethylene (EP) and propylene-ran-(1-butene) (BP) copolymers with various comonomer content (2-3.1 wt.% ethylene, 9.9 wt.% 1-butene), were prepared in Brabender internal mixer at various compositions (25/75, 50/50, 75/25). Static, impact and dynamic mechanical behavior of copolymers and their blends was investigated. The crystalline structure was studied by DSC and SAXS analysis. For all copolymers the lamellar thickness, crystallinity degree and glass transition temperature are lower than those of iPP homopolymer, depending on the comonomer content. It was found that the copolymers exhibit improved impact strength as compared to plain iPP, due to lower crystallinity and higher mobility of chains within amorphous component. Moreover, the elastic modulus as well as the yield behavior of the examined samples resulted to depend primarily on the amount of the crystalline phase and the thickness of the lamellar crystals, respectively. A linear dependence of yield stress on the logarithm of reciprocal lamellar thickness was observed for blends and copolymers, supporting the concept of thermal nucleation of dislocations which control the crystallographic slip processes initiated at the yield point. The blends of BPS with either EPS or EP2 display complete miscibility in the entire range of composition and their mechanical properties are intermediate between those of plain components, changing gradually with the composition.     

PMMA/MMT nanocomposites prepared by one-step in situ intercalative solution polymerization

Poly(methylmetacrylate)/montmorillonite (PMMA)/(MMT) nanocomposites were prepared by one-step in situ intercalative solution polymerization involving simultaneous modification of MMT with quaternary ammonium salts (QAS), polymerization and polymer intercalation. Polymerization proceeded at 70 °C in a mixture of ethanol and water, whereas the nanocomposite was precipitated with only water. Four QAS’s with different alkyl chain lengths, as well as a QAS with an additional acrylic group, were used to study the influence of the type of quaternary ammonium salt on intercalation. The largest extent of intercalation was achieved in nanocomposites with the QAS having one long alkyl (C16) chain. The obtained PMMA/MMT intercalated nanocomposites exhibited a higher glass transition temperature, better thermal stability, and improved solvent resistance than the pure PMMA.     

Transparent polymer blends composed of cellulose acetate propionate and poly(epichlorohydrin)

Structure and properties for binary blends composed of biomass-based cellulose acetate propionate (CAP) and poly(epichlorohydrin) (PECH) have been studied. It is found from the dynamic mechanical measurements that mutual dissolution takes place to some degree with remaining CAP-rich and PECH-rich regions in the blends. As a result of the interdiffusion, leading to fine morphology, the blends exhibit high level of optical transparency although the individual pure components have different refractive index. Furthermore, the mechanical toughness of CAP, which is one of the most serious problems for CAP, is considerably improved by blending PECH. This will have a great impact on industries because the blend technique widens the application of CAP.     

Polymer gel electrolytes based on oligomeric polyether/cross-linked PMMA blends prepared via in situ polymerization

Very-low-vapor-pressure oligomeric polyether electrolytes blended with and dimensionally stabilized by cross-linked poly(methyl methacrylate) (PMMA) are prepared via in situ polymerization. The synthesized polymer gel electrolytes (PGEs) are freestanding films with excellent dimensional stability, mechanical integrity and strength. They exhibit high ionic conductivity at room temperature reaching 4.3 × 10⁻⁴ S/cm for the highest conducting sample and exceptional thermal stability. The oligomeric polyether and PMMA appear to have molecular level interaction in the blends and the PGEs remain a single phase from at least −50 to 200 °C, potentially enabling their application in advanced batteries in wide temperature ranges. The novel in situ polymerization process allows precise control of the composition of the PGEs and can enable in situ fabrication of advanced cells.     

Mechanical and thermal properties of syndiotactic polystyrene blends with poly(p-phenylene sulfide)

Melt blends of syndiotactic polystyrene (sPS) and poly(p-phenylene sulfide) (PPS) have been prepared by using an internal mixer at 300 °C. The thermal, mechanical and morphological properties of binary blends of sPS with PPS have been investigated in this paper. The thermal and morphological properties show the immiscible binary blend evidences, which have a clear phase separation between the components at all compositions and a lack of adhesion at the interface. According to the X-ray diffraction patterns of blends, the crystalline structure of sPS in the blend is not altered from α form to β form. Indeed, the results for tensile test reveal that there is no synergism of the modulus of elasticity for sPS/PPS blend system.     

Mechanical properties of thermoplastic polyester elastomer controlled by blending with poly(butylene terephthalate)

Thermoplastic polyester elastomer (TPEE) blends with poly(butylene terephthalate) (PBT) were prepared by melt compounding for the phase morphology and mechanical property studies. Although PBT is immiscible with the continuous soft poly(tetramethylene glycol) (PTMEG) phase of TPEE, it is miscible with the discrete hard PBT one of TPEE. Therefore, PBT and TPEE are compatible and their blends reveal very low level of interfacial tension and very small size of discrete domains, as well as good interfacial adhesion between two phases, which provide high possibility to prepare TPEE alloys with controllable properties. Mechanical test results reveal that both the modulus and yield and tensile strengths increase with increasing weight ratios of PBT. The increased system rigidity and decreased system plasticity are further confirmed by the cyclic tensile tests. The main objective of this work is to provide useful information on the structure and property control of TPEE by simple mixing with aromatic polyesters.     

Effect of dispersed phase composition on morphological and mechanical properties of PET/EVA/PP ternary blends

Immiscible ternary blends of PET/EVA/PP (PET as the matrix and (PP/EVA) composition ratio = 1/1) were prepared by melt mixing. Scanning electron microscope results showed core‐shell type morphology for this ternary blend. Binary blends of PET/PP and PET/EVA were also prepared as control samples. Two grades of EVA with various viscosities, one higher and the other one lower than that of PP, were used to investigate the effect of components' viscosity on the droplet size of disperse phase. The effect of interfacial tension, elasticity, and viscosity on the disperse phase size of both binary and ternary blends was investigated. Variation of tensile modulus of both binary and ternary blends with dispersed phase content was also studied. Experimental results obtained for modulus of PET/EVA binary blends, showed no significant deviations from Takayanagi model, where considerable deviations were observed for PET/PP binary blends. Here, this model that has been originally proposed for binary blends was improved to become applicable for the prediction of the tensile modulus of ternary blends. The new modified model showed good agreement with the experimental data obtained in this study. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 251–259, 2010     

Study on damping properties of HVBR/EVM blends prepared by in situ polymerization

In comparison with normal damping rubbers such as natural rubber (NR), styrene butadiene rubber (SBR), isobutylene isoprene rubber (IIR) etc., Mo-based high vinyl polybutadiene rubber (HVBR) with high loss factor, excellent aging resistance and glass transition temperature closer to room temperature, is a promising damping material. The effective damping temperature range of HVBR could be further broadened by blending with ethylene-vinyl acetate (EVM) and the effects of blending methods (in situ polymerization blending or mechanical blending) and blending ratios on the damping properties and physical properties of HVBR/EVM blended rubber were studied. HVBR/EVM in situ polymerization blends was prepared by butadiene coordination polymerization by Mo-base catalyst in a toluene solution of EVM. The results of dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM) of the blended vulcanizates via in situ polymerization blending revealed that the compatibility between HVBR and EVM was improved compared with that of the blended vulcanizates via the traditional mechanical blending method. The two phases of HVBR/EVM in situ polymerization blends had good dispersion and uniformity, the damping temperature range was significantly expanded, and the peak and valley of the damping temperature range were greatly improved. A blending ratio of HVBR/EVM900 = 100/40 showed the best damping properties and the effective damping temperature range (tanδ>0.3) was extended from −6.6 °C to 39.4 °C.     

Optical properties of core/shell typed PMMA/CdS nanoparticles prepared by in situ and ex situ surfactant-free emulsion polymerization

Core/shell poly(methyl methacrylate)/cadmium sulfide (PMMA/CdS) nanoparticles were prepared by surfactant-free emulsion copolymerization with 2-(dimethylamino)ethyl methacrylate (DMAEMA) auxiliary monomer. According to the addition time of Cd²⁺ ions, the synthesis of the hybrid nanoparticles was conducted in in situ and ex situ techniques. The core/shell PMMA/CdS nanoparticles synthesized by the post-addition (ex situ) of Cd²⁺ ions showed a wide size distribution and interference fringes in the photoluminescence (PL) spectrum. However, these results were improved when the PMMA/CdS nanoparticles were synthesized in the presence of Cd²⁺ ions (in situ method). The in situ method made it possible to obtain monodisperse hybrid nanoparticles and fairly narrow band-gap emission.     

Effects of coupling agents on mechanical and morphological behavior of the PP/HDPE blend with two different CaCO3

The main purpose of incorporating fillers, such as calcium carbonate, into blends of polyolefins is to decrease costs and change tensile and impact properties. Structural differences between both components give rise to the formation of large filler agglomerates in the polymer matrix, which influence the mechanical response of the material. Therefore, the coupling agents of the Lica 12 type at various concentrations was used to facilitate the link between filler and matrix (the latter consisting of PP/HDPE 80/20 wt). Filler was added to the PP/HDPE blend at a 30 wt.% concentration. Two types of calcium carbonate (CaCO₃) were used. These have different average sizes (3.0 and 1.8 μm) which were determined by means of laser diffraction techniques. In addition other coupling agents of the titanate type, such as Lica 09, Lica 01, zirconates ZN 12, and a 1:1 mixture of Lica 12 and Lica 01, were used. This study clearly demonstrated that the addition of the coupling agent to CaCO₃ modifies the mechanical properties of the PP/HDPE/CaCO₃ composites. Values of the mechanical properties indicate that due to its characteristics, each coupling agent gives rise to increases in a particular mechanical property. In the case of Lica 01 an increase was verified in Young’s modulus at 0.7 wt.% and in elongation at break at both concentrations (0.3 and 0.7 wt.%), whereas ZN 12 brought about an increase in elongation at break. The 1:1 mixture of Lica 12 and Lica 01 caused impact resistance of the blend of PP/HDPE with CaCO₃ to increase considerably.     

Preparation and characterization of flame retardant and low smoke releasing oil-resistant EVA/NBR blends

Nano-Si O2 and/or Mo O3 were introduced to ethylene-vinyl acetate/nitrile butadiene rubber(EVA/NBR) blends containing magnesium hydroxide(MH) and red phosphorus(RP) to further improve the mechanical properties, oil resistance, smoke suppression and flame retardancy. The results indicated that the tensile strength and oil resistance were significantly improved by incorporating nano-Si O2. Smoke suppression tests for EVA/NBR blend samples showed that both nano-Si O2 and Mo O3 can significantly reduce smoke release amount. The flammability characterization indicated that the blended sample with an LOI value of 33.0 could achieve V-0 level in the UL-94 test. Cone calorimetry test data showed the peak heat release rate was 67% lower than that for pure EVA/NBR. Thermal analysis showed that the presence of both nano-Si O2 and Mo O3 was beneficial to promoting char formation of the EVA/NBR blends. Char residual analysis suggested that Mo O3 aggregated in solid phase during combustion.     

Thermal properties of EPDM/NR blends

The thermal behaviour of EPDM/NR blends was studied by differential scanning calorimetry over the temperature range 335–435 K. O'Neill's method (O'Neill MG. Anal Chem 1964;36:1238) was used for calculating the specific heat capacity with aluminia as standard. The presence of natural rubber induces a marked thermal instability because of the high content of double bonds. The contribution of each component to the C_p of the tested polymer systems is discussed. The law of reciprocal affinity, the linear contribution of components to the specific heat capacity is followed by EPDM/NR blends. The influence of natural rubber on the thermal behaviour of tested mixtures was assessed by oxygen uptake method and the first derivative procedure reveals the sequence in thermal stability of ethylene-propylene-diene/natural rubber compounds.     

Photochemical aging of in situ polymerized blends of polystyrene and poly[acrylonitrile-g-(ethylene-co-propylene-co-diene)-g-styrene] (AES)

The influence of photochemical aging of in situ polymerized PS/AES blends on their mechanical properties has been studied. The PS/AES blends were subjected to photochemical aging for 168 h and 720 h. Tensile properties and Izod impact resistance of aged and non-aged samples were evaluated. The mechanical properties of the PS/AES blends are influenced by the polymerization temperature and blend composition and represent a balance between the toughness of EPDM and the stiffness of SAN in the PS matrix. Even though the impact resistance and strain at break of HIPS are higher than those of the PS/AES blends, after the aging period all PS/AES blends showed higher strain at break than HIPS. PS/AES blends present higher photochemical stability than HIPS.