The interfacial activity of a hydrogenated polybutadiene-polystyrene tapered diblock copolymer, (HPB-b-PS) is investigated in blends of a low density polyethylene (LDPE) with a high impact polystyrene (HIPS) prepared in the melt state on a two-roll mill. Optical and scanning electron microscopy examinations of smoothed or fracture surfaces and also surfaces obtained after THF-extraction of PS phases demonstrate that the copolymer promotes the dispersion and interfacial adhesion of the components, whatever the composition and is able to create and stabilize particular dispersions of the rubber particles in these blends. Tensile and Charpy impact properties are also very significantly improved. All these features demonstrate that the ductility and toughness of PS and LDPE/PS blends can be closely controlled by adequate combinations of rubber particles and a HPB-b-PS copolymer. 相似文献
Effects of polystyrene block content on adhesion property and phase structure of polystyrene block copolymers were investigated. Polystyrene-block-polyisoprene-block-polystyrene triblock and polystyrene-block-polyisoprene diblock copolymers with different polystyrene block contents in the range from 13 to 35 wt% were used. In the case of the low polystyrene block content (below 16 wt%), a sea-island structure was observed: near-spherical polystyrene domains having a mean diameter of about 20 nm were dispersed in polyisoprene matrix. The phase structure changed from a sea-island structure to a cylindrical structure with an increase of polystyrene block content (over 18 wt%). Peel strength decreased with an increase of polystyrene block content and the pure triblock copolymers had lower peel strength than their blends with the diblock copolymers. Pulse nuclear magnetic resonance studies indicated that molecular mobility of polyisoprene phase decreased with an increase of polystyrene block content, and the molecular mobility was lower in the pure triblock than in the blend. Thus, the peel strength was found to be related to molecular mobility. The adhesion strength of the block copolymer depended on the molecular mobility: high molecular mobility can promote interfacial adhesion. 相似文献
Three triblock copolymers of poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) of different molecular weights and one diblock copolymer of poly[styrene-b-(ethylene-co-butylene)] (SEB) were used to compatibilize high density polyethylene/syndiotactic polystyrene (HDPE/sPS, 80/20) blend. Morphology observation showed that phase size of the dispersed sPS particles was significantly reduced on addition of all the four copolymers and the interfacial adhesion between the two phases was dramatically enhanced. Tensile strength of the blends increased at lower copolymer content but decreased with increasing copolymer content. The elongation at break of the blends improved and sharply increased with increments of the copolymers. Drop in modulus of the blend was observed on addition of the rubbery copolymers. The mechanical performance of the modified blends is strikingly dependent not only on the interfacial activity of the copolymers but also on the mechanical properties of the copolymers, particularly at the high copolymer concentration. Addition of compatibilizers to HDPE/sPS blend resulted in a significant reduction in crystallinity of both HDPE and sPS. Measurements of Vicat softening temperature of the HDPE/sPS blends show that heat resistance of HDPE is greatly improved upon incorporation of 20 wt% sPS. 相似文献
Addition of styrene (S)/4-hydroxystyrene (HS) block, blocky gradient, or blocky random copolymer to 80/20 wt% polystyrene (PS)/polycaprolactone (PCL) blends is examined as a compatibilization strategy. Four copolymers are synthesized by controlled radical polymerization, each with an S block and the other block being a HS block or S/HS random or gradient copolymer. Compatibilization depends on copolymer level and HS sequence distribution and content. Using a two-step solution-mixing/melt-mixing process, addition of 2 wt% and 5 wt% nearly symmetric S/HS diblock copolymer leads to compatibilization with average PCL domain diameters of 390-490 nm and 90-110 nm, respectively. In contrast, adding 0.25-0.75 wt% copolymer leads to microscale dispersed-phase domains and only reduced melt-state coarsening. Results with 2-5 wt% added copolymer indicate that a major reduction in interfacial tension is facilitated by hydrogen bonding of HS units and PCL carbonyl groups. Nanoscale confinement of normally semi-crystalline PCL within blends with 100 nm dispersed phases impedes PCL crystallizability, yielding liquid-state PCL domains at room temperature and demonstrating that properties of nanostructured blends and microstructured blends can differ greatly. Polystyrene/PCL blends are also made by one-step melt mixing with low mol% HS copolymers. Adding 5 wt% blocky gradient S/HS copolymer (86/14 mol% S/HS) leads to compatibilization with an average dispersed-phase diameter of 360-420 nm. In contrast, adding 5 wt% blocky random (87/13 mol% S/HS) or 5 wt% diblock (81/19 mol% S/HS) copolymer yields microscale dispersed-phase domains and only reduced coarsening. Crystallization in these blends is less hindered than in blends containing 2-5 wt% nearly symmetric S/HS diblock copolymer, indicating that both hydrogen bonding and confinement suppress PCL crystallization. 相似文献
A family of emulsification curves has been systematically prepared in order to determine the extent of interfacial modifier migration to the high density polyethylene (HDPE)/polystyrene (PS) interface. Through an examination of the evolution of the equilibrium dispersed phase size after interfacial saturation, as well as a comparison of the apparent interfacial area occupied per modifier molecule (Aapp) at the different dispersed phase concentrations, it is possible to detect the onset of micelle formation and to estimate the extent of interfacial coverage. This approach has been applied to HDPE/PS blends, using a variety of triblock and diblock copolymer interfacial modifiers for that system. It is shown quantitatively that it is the affinity of the block copolymer for the matrix material that dominates migration efficacy to the interface. Asymmetrical block copolymers (30PS/70EB) show a strong tendency to form micelles when HDPE is the matrix. This effect is virtually eliminated when PS is the matrix material or when symmetrical block copolymers (50PS/50EB) are used. In these latter cases all the interfacial modifier finds its way to the interface. 相似文献
Summary: In the previous study, we observed compatibilizing effects of low density polyethylene (LDPE)/polystyrene (PS) with polystyrene‐block‐poly(ethylene‐co‐butylene)‐block‐polystyrene (SEBS), a triblock copolymer. Blends consisting of 70 wt.‐% LDPE and 30 wt.‐% PS were prepared with a SEBS concentration of up to 10 wt.‐%. This study examined the electrical properties such as the electrical breakdown, water tree length, permittivity and tan δ in the blends. The possibility of using these blends as insulating material substitutes for LDPE was investigated. The electrical breakdown strength reached a maximum of 66.67 kV/mm, which is superior to 50.27 kV/mm of the LDPE used as electrical insulators for cables. In addition, the water tree length decreased with increasing SEBS concentration. The water tree lengths of the blends containing SEBS were shorter than that of the LDPE. The permittivity of the blends was 2.28–2.48 F/m, and decreased with increasing SEBS concentration with the exception of S‐0. Tan δ of the blends increased smoothly with increasing SEBS content.
Breakdown strength , water tree length, permittivity and tan δ of the LDPE/PS/SEBS blends and raw materials. 相似文献
A continuous, industrially scalable process called solid-state shear pulverization (SSSP) leads to compatibilization of polystyrene (PS)/high-density polyethylene (HDPE) blends by addition of a commercially available styrene/ethylene-butylene/styrene (SEBS) triblock copolymer. Partial or full compatibilization is characterized by a reduction or elimination of coarsening of the dispersed-phase domains during high-temperature (190 °C), static annealing. In the case of a 90/10 wt% PS/HDPE blend, processing with 3.5 wt% SEBS block copolymer by SSSP yields a coarsening rate that is reduced by a factor of 10 (six) relative to a melt-mixed blend without copolymer (with 3.5 wt% SEBS block copolymer). Addition of 5.0 wt% SEBS block copolymer to the 90/10 wt% PS/HDPE blend during SSSP yields a reduction in coarsening rate by a factor of thirty relative to a melt-mixed blend without copolymer. With an 80/20 wt% PS/HDPE blend, pulverization with 10 wt% SEBS block copolymer yields cessation of coarsening when the average dispersed-phase domain diameter reaches 1.6-1.7 μm. The implications of these results for developing a new, technologically attractive method for achieving compatibilization of immiscible polymer blends are discussed. 相似文献
The interfacial tension of the uncompatibilized and compatibilized blends of low density polyethylene (LDPE) and polyamide 6 (PA6) has been measured by the breaking thread method. Different types of compatibilizer precursors have been used: poly(ethylene-co-acrylic acid) (Escor 5001, by Exxon) having 6 wt% concentration of acrylic acid; an ethylene-acrylic acid zinc ionomer (Iotek 4200); a triblock copolymer with polystyrene end blocks and a rubbery poly(ethylene–butylene mid block (SEBS) (Kraton G 1652); and SEBS-g-MA (Kraton FG 1901X) with 2 wt% maleic anhydride. The compatibilizing efficiency of the different types of the compatibilizer precursors towards the blends has been evaluated quantitatively by the values of the interfacial tension obtained. It has been shown that Iotek and SEBS-g-MA posses the highest compatibilizing efficiency, demonstrated by the strongest decrease of the interfacial tension and the dimension of the droplets of the dispersed phase. Contrary, SEBS almost does not influence the interfacial tension and the size of the particles. Hence, it possesses the lowest compatibilizing activity towards the blends. The compatibilizer Escor displays an activity lower than that of Iotek and SEBS-g-MA, but it is higher than that of SEBS. 相似文献
The mechanical properties and morphology of melt mixed polystyrene (PS)/polyethylene (PE) blends that were modified by the addition of up to 16% of a semicrystalline PS-b-hPB (hydrogenated polybutadiene) diblock copolymer with varying molecular weight are reported. As a result of the blocks of the copolymer penetrating the corresponding homopolymers, these diblock copolymers are capable of reinforcing the PS/PE interface significantly. This increase in interfacial strength between the immiscible blend components does not necessarily result in an improvement in the mechanical properties of the blends as measured by Izod or tensile tests. This may be because the effect of the copolymers on the rheological properties of the blends during processing outweighs their emulsifying/reinforcing effects. If found to be universally true for polymer blends, these results suggest that the relationship between the effects of copolymers on interfacial strength, their emulsifying effects, and the mechanical properties of copolymer modified blends are not as simple as suggested by many statements found in the literature. 相似文献
Phthalic anhydride terminated polystyrene (PS-An) and styrene-maleic anhydride copolymer (SMA) were compared as a compatibilizer at low loadings (<10 wt%) in 70/30 polyamide 66 (PA66)/polystyrene (PS) blends. Compatibilization efficiency was judged by morphology of the blends and the extent of interfacial coupling to copolymer. Fluorescent labels of functional PS's (anthracene and pyrene for PS-An and SMA, respectively) allowed the detection of small amounts of reactively formed block (PA66-b-PS) or graft copolymer (SMA-g-PA66) in the blends via gel permeation chromatography with a fluorescence detector. Extremely fast reactions giving >60% conversion in 0.5 min mixing were observed regardless of the molecular weight, the structure, and the amount of the functional PS's. Interfacial stability of the reactively formed copolymers was estimated by micelle formation in the bulk phases and the interfacial coverage, Σ. PS-An with higher molecular weight (37 kg/mol) was most effective as a compatibilizer at the interface, showing less tendency to form microemulsions by suppressing interfacial roughening. However, a large portion of PA66-b-PS from low molecular weight PS-An (10 kg/mol) and SMA-g-PA66 from random functional SMA (16 kg/mol) migrated to the bulk phase to form micelles even at <2 wt% loadings. Blends of PA66 with syndiotactic PS compatibilized with PS-An gave very similar morphology to the PA66/PS blends indicating that these conclusions apply also to PA66/sPS blends. 相似文献
Linear styrene-block-butadiene-block-styrene (SBS) triblock copolymers having different interfacial structures were investigated. In spite of the nearly equivalent chemical composition (about 70 vol% of styrene), these copolymers show significantly different morphologies. It was shown that the origin of the modified morphology in asymmetric block copolymers is the intermixing of short polystyrene (PS) chains or chain segments into the polybutadiene (PB) phase. It has a consequence of an increase in the glass transition temperature of the soft phase (PB phase here) and a significant decrease of the whole relaxation time of the materials. The larger the interfacial volume, the more PS molecules can mix into the PB phase. Moreover, it seems that the extent of the stress transfer in heterogeneous polymeric systems is crucially influenced by the interface. The tapered interface in an SBS block copolymer, for example, permits a more effective stress transfer compared to the sharp interface resulting in a higher degree of orientation in the individual phases of the materials. 相似文献
Monte Carlo simulations were used to investigate the compatibilizing effects of diblock copolymers in A/B/A-B diblock copolymer ternary blends and triblock copolymers in A/B/triblock copolymer ternary blends, respectively. The volume fraction of homopolymer A was 19% and was the dispersed phase. The simulation results show that diblock copolymers with longer A-blocks are more efficient as compatibilizers, and symmetric triblock copolymers with a shorter middle block length are easily able to bridge each other through the association of the end blocks. This kind of triblock copolymers have relatively high ability to retard phase separation as compatibilizers. 相似文献