Effect of Octene Block Copolymer (OBC) and High-Density Polyethylene (HDPE) on Crystalline Morphology, Structure and Mechanical Properties of Octene Random Copolymer

Blending octene random copolymer (ORC) with other polymers is a promising approach to improving ORC mechanical properties, such as tensile strength and elongation. In this study, octene block copolymer (OBC) with lower density than ORC and high-density polyethylene (HDPE) were used to blend with ORC. The effect of both OBC and HDPE on ORC was analyzed using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and small-angle X-ray scattering (SAXS). For ORC/OBC blends, a small amount of OBC can improve the crystallization ability of ORC. Meanwhile, for ORC/HDPE blends, the crystallization ability of ORC was significantly suppressed, attributed to good compatibility between ORC and HDPE as indicated by the homogeneous morphology and the disappearance of the α transition peak of ORC in ORC/HDPE blends. Therefore, the tensile strength and elongation of ORC/HDPE blends are significantly higher than those of ORC/OBC blends. For ORC/OBC/HDPE ternary blends, we found that when ORC:OBC:HDPE are at a ratio of 70:15:15, cocrystallization is achieved. Although HDPE improves the compatibility of ORC and OBC, the three-phase structure of the ternary blends can be observed through SAXS when HDPE and OBC exceed 30 wt%. Blending HDPE and OBC (≤30 wt%) could improve the mechanical property of ORC.

Foams with Enhanced Ductility and Impact Behavior Based on Polypropylene Composites

In this work, formulations based on composites of a linear polypropylene (L-PP), a long-chain branched polypropylene (LCB-PP), a polypropylene-graft-maleic anhydride (PP-MA), a styrene-ethylene-butylene-styrene copolymer (SEBS), glass fibers (GF), and halloysite nanotubes (HNT-QM) have been foamed by using the improved compression molding route (ICM), obtaining relative densities of about 0.62. The combination of the inclusion of elastomer and rigid phases with the use of the LCB-PP led to foams with a better cellular structure, an improved ductility, and considerable values of the elastic modulus. Consequently, the produced foams presented simultaneously an excellent impact performance and a high stiffness with respect to their corresponding solid counterparts.

Melt Rheological Behavior and Morphology of Poly(ethylene oxide)/Natural Rubber-graft-Poly(methyl methacrylate) Blends

The influence of morphology on the rheological properties of poly(ethylene oxide) (PEO) and natural rubber-graft-poly(methyl methacrylate) (NR-g-PMMA) blends in the melt was investigated. The blends were prepared at different blend compositions by a solution-casting method. Linear viscoelastic shear oscillations measurements were performed in order to determine the elastic and viscous properties of the blends in the melt. The rheological results suggested that the blending of the two constituents reduced the elasticity and viscosity of the blends. The addition of an even small amount of NR-g-PMMA to PEO changed the liquid-like behavior of PEO to more solid-like behavior. Morphological investigations were carried out by optical microscopy to establish the relationship between morphology and melt viscosity. Depending on the blend compositions and viscosities, either droplet-matrix or co-continuous morphologies was observed. PEO/NR-g-PMMA blends exhibited a broad co-continuity range, and phase inversion was suggested to occur at the PEO/NR-g-PMMA blend with a mass ratio of 60/40 (m/m), when NR-g-PMMA was added to PEO as a matrix.

Increasing the Impact Toughness of Cellulose Fiber Reinforced Polypropylene Composites—Influence of Different Impact Modifiers and Production Scales

While cellulose fiber reinforced polypropylene (PP) composites typically offer good stiffness and strength in combination with ecological benefits and a high potential for lightweight construction, they often require measures taken to improve their impact performance. In this work, the influence of different types of impact modifier on the mechanical performance of a PP–cellulose composite was systematically investigated, with a particular focus on the improvement of the notched impact strength and the accompanying loss of stiffness. Among the tested impact modifiers, ethylene-octene copolymers appeared to be the most suitable class to achieve a good overall performance. A high modifier viscosity increased its potential to improve the notched impact strength of the composite. Additionally, composite production on a larger scale improved the impact performance without significantly affecting the tensile properties. Several composites from this study surpassed the overall mechanical performance of a benchmark commercial PP–cellulose composite. While the impact strength of commercial high-impact PP–talc composites could not be reached, the considerably lower density of the PP–cellulose composites is worth mentioning.

Synergetic Toughening Effect of Carbon Nanotubes and β-Nucleating Agents on the Polypropylene Random Copolymer/Styrene-Ethylene-Butylene- Styrene Block Copolymer Blends

Polypropylene random co-polymer (PPR)/styrene-ethylene-butylene-styrene (SBS) block copolymer blends with high toughness and favorable tensile properties were successfully obtained by blending with traces of multi-wall carbon nanotubes (MWCNTs) and β-nucleating agents (β-NAs). β-NAs can effectively induce the ductile β-form crystal in the PPR matrix. Although the addition of MWCNTs was reported to be only benefit for the tensile strength of PPR and relatively disadvantageous for the toughness, the obviously synergistic toughening effect in PPR/SBS blends was found when MWCNTs and β-NAs coexisted. The notched izod impact strength of PPR/30 wt % SBS blend with MWCNTs and β-NAs increased from 11.3 to 58.9 kJ/m²; more than 5-fold increment compared with pure PPR. Meanwhile, the tensile strength retention of this PPR blend is still above 72.2%. The micro-morphology indicated that the MWCNTs can act as bridges between SBS particle and PPR matrix, effectively transferring the stress and absorbing impact energy among SBS particles.

Isothermal and Non-Isothermal Crystallization Studies of Long Chain Branched Polypropylene Containing Poly(ethylene-co-octene) under Quiescent and Shear Conditions

Isothermal and non-isothermal crystallization behaviours of the blends of long chain branched polypropylene (LCB PP) and poly(ethylene-co-octene) (PEOc) with different weight ratios were studied under quiescent and shear flow using polarized optical microscopy (POM), differential scanning calorimetry (DSC), and rheological measurements. Experimental results showed that the crystallization of the LCB PP/PEOc blends were significantly accelerated due to the existence of the long chain branches (LCBs), the blends being able to rapidly crystallize even at 146 °C. The addition of PEOc that acts as a nucleating agent, could also increase the crystallization rate of LCB PP. However, the crystallization rate of LCB PP was reduced when the PEOc concentration was more than 60 wt %, showing a retarded crystallization growth mechanism. The morphology of the binary blend was changed from a sea-island structure to a co-continuous phase structure when the PEOc concentration was increased from 40 to 60 wt %. In comparison with linear isotactic iPP/PEOc, the interfacial tension between LCB PP and PEOc was increased. In addition, flow-induced crystallization of LCB PP/PEOc blends was observed. Possible crystallization mechanisms for both LCB PP/PEOc and iPP/PEOc blends were proposed.