Correlation between the Interfacial Tension and Dispersed Phase Morphology in Interfacially Modified Blends of LLDPE and PVC

Phase behavior and interfacial tension of ternary polymer mixtures with block copolymers

The phase behavior and interfacial tension of ternary polymeric mixtures (polystyrene/polystyrene-b-poly(methyl methacrylate)/poly(methyl methacrylate), PS/PS-b-PMMA/PMMA) are investigated by dissipative particle dynamics (DPD) simulations. Our simulation results show that, as the PS-b-PMMA diblock copolymer concentration increases, the interfacial tension decreases due to the decayed correlations between homopolymers PS and PMMA. When the chain lengths of copolymers are fixed, with the increase of the chain lengths of PS and PMMA homopolymers the interfacial width becomes wider and the interfacial tension becomes smaller, due to the copolymers presenting more stretched and swollen structures in the mixtures with the short length of homopolymers. However, with simultaneously increasing chain lengths of both diblock copolymer and homopolymers with a fixed ratio, the interfacial tension increases because the copolymer chains with longer chain length penetrate more deeply into the homopolymer phase and the interactions between diblock copolymers become weaker. These results will provide a way to mix incompatible homopolymers to improve material performances.

Relaxation Behavior of Core-Shell Particles in PP/PMMA/PS Ternary Blends: The Effects of Composition, Viscosity Ratio and Temperature

The relaxation behavior of PMMA-PS core-shell particles in PP matrix was studied. The effects of composition and viscosity ratio of core and shell forming components on relaxation processes of PP/(PMMA+PS) 80/20 ternary blends were evaluated at three different temperatures (200, 225 and 250°C) and discussed. For the ternary blends containing low-viscosity PMMA (PP/L-PMMA/PS), the shape relaxation time, λ, sharply reduced at first with PS content and then increased after passing through a minimum with further increase in the PS content. The corresponding relaxation strength, λ.H(λ), increased suddenly at first and then monotonically decreased upon further incorporation of PS. The changes of λ and λ.H(λ) with PS content were attributed to a change in the interfacial energy (shell formation) and average viscosity of the dispersed composite droplets upon progressive addition of PS into PP/L-PMMA blend so that the minimum λ corresponding to the maximum λ.H(λ) was observed at shell completion composition with finest core-shell- particles (12 wt% of PS phase). The core-shell particles of all the ternary blends containing L-PMMA exhibited a shape relaxation at 200°C, while at the same temperature for the blends containing high-viscosity PMMA (H-PMMA) no shape relaxation peak was detected when the PS shell content was lower than 62 wt%. This was attributed to restriction effect of non-deformable H-PMMA core droplets, which led to no droplet relaxation. At higher PS contents, appearance of the shape relaxation peak was related to the relaxation of PS shell, suggesting that there is a critical shell thickness above which the relaxation behavior of core-shell droplets is dominated by the low-viscous PS shell. Increase in temperature from 200 to 250°C reduced the PS shell content corresponding to onset of deformation and accelerated the relaxation of composite droplets.

Fracture Toughness of PP/EPDM/Nano-Ternary Composites: The Role of Distribution of Inorganic Particles

The influence of the distribution of the inorganic particles on the toughness of the PP/EPDM/nano-ternary composites was investigated. Four morphologies for PP/EPDM/nano-ternary composites were obtained by means of adjusting the surface tension of inorganic particles (nano-CaCO3, hydrophobic nano-SiO2 and hydrophilic nano-SiO2) and the compounding sequence (one-step extrusion and two-step extrusion). Morphological observation revealed that the segregated dispersion morphology was formed in the PP/EPDM/CaCO3 composite. For the PP/EPDM/R974 (hydrophobic nano-SiO2) composite, R974 particles were dispersed at the interface between the PP matrix and EPDM dispersed phase. A200 particles (hydrophilic nano-SiO2) continuously dispersed between PP and EPDM phase for PP/EPDM/A200 composites prepared by one-step, while were present in EPDM dispersed phase for the two-step PP/EPDM/A200 composites. The dependence of the toughness on the phase morphology of the components, especially the distribution of nanoparticles, was studied systematically. The impact strength of one-step PP/EPDM/A200 composites was pronouncedly enhanced, increasing 552 % compared to pure PP. Compared with the other three composites, the one-step PP/EPDM/A200 composites exhibits better effect of preventing crack propagation and far higher fracture energies. It is attributed to the A200 particles continuously dispersed between EPDM phase and matrix, which makes EPDM particles have better compatibility with the PP matrix and the overlapping of the stress field with A200 particles.

Morphology evolution and the tri-continuous morphology formation of a PVDF/PS/HDPE ternary blend in melt mixing

Manipulate the perfect tri-continuous structure of the PVDF/PS/HDPE system successfully and it can allow preparation for the functionalization of tri-continuous morphology!

Structure–property relationships in super-toughened polypropylene-based ternary blends of core–shell morphology

A specific “percolated/interconnected” morphology of PA6/EPDM-g-MA core–shell modifier particles in PP matrix resulted in a tremendous enhancement of impact strength. Fracture behavior and toughening mechanisms were studied and proposed.

Synthesis and characterization of amphiphilic triblock Copolymers with Identical compositions but different block sequences

The amphiphilic triblock copolymers PAA-b-PS-b-PAA and PS-b-PAA-b-PS were synthesized by a combination of an atom transfer radical polymerization mechanism and a nitroxide radical coupling reaction or copper-catalyzed azide/alkyne click chemistry.

High performance polyethylene/thermoplastic starch blends through controlled emulsification phenomena

The emulsification efficacies of a range of compatibilizers for polyethylene/thermoplastic starch blends have been studied and a detailed morphological and mechanical analysis has been conducted. It is shown that polyethylene-maleic anhydride terpolymers containing elastomeric segments provided excellent emulsification of PE/TPS blends with a fine morphology (volume diameter of 1.4 μm; number average diameter of 600 nm). The blends compatibilized with these copolymers exhibit a very high elongation at break of about 800%, the highest value ever reported for PE/TPS systems. Also, significant improvement in notched impact strength performance at interfacial saturation was found for these systems leading to specimens with an equivalent performance to pure polyethylene. An excellent correlation was found between the critical concentration for interfacial saturation and the mechanical properties, indicating the key role of morphology.

Macroporous poly(l-lactide) of controlled pore size derived from the annealing of co-continuous polystyrene/poly(l-lactide) blends

A detailed study on the static annealing of co-continuous polystyrene/poly(L-lactide) (PLLA) blends is presented. The effects of temperature, time at temperature, viscosity of the phases and interfacial modification on the coarsening of the blend are discussed. In this paper, polystyrene and PLLA are blended at compositions of 50/50 and 60/40 to form co-continuous morphologies. These co-continuous morphologies are coarsened under quiescent annealing conditions, and the subsequent removal of the polystyrene phase leaves a macroporous PLLA structure. The microstructure is analyzed using three different techniques: the BET nitrogen adsorption technique, mercury intrusion porosimetry and SEM combined with image analysis. It is shown that static annealing can be used to generate a series of co-continuous networks with controlled pore sizes ranging from 1 to hundreds of microns. A non-linear pore size growth rate is observed for these systems due to the degradation of PLLA and this study indicates that controlled degradation can be used as an additional tool for morphology control. Compatibilized polystyrene/PLLA blends demonstrate significantly reduced coarsening effects due to the reduction of interfacial tension. The coarsening rate of the co-continuous structure was examined in terms of the pore size, R and this growth rate is discussed in terms of a previously proposed coarsening mechanism. This approach is a route towards the preparation of a macroporous PLLA structure with pore sizes in the range required for scaffolds for tissue regeneration.