Correlation of miscibility and mechanical properties of polypropylene/olefin block copolymers: Effect of chain composition

Synthesis and Properties of Polybutylene (Succinate)-b-poly(dimethylsiloxane) with Unprecedented Combined Performance and Functions

The excellent combined properties of poly(butylene succinate) (PBS) make it a promising biodegradable plastic. However, the lack of functionality and low impact strength limit its application. Poly(dimethylsiloxane) (PDMS) was introduced to prepare new high-performance and functional poly(butylene succinate)-b-poly(dimethylsiloxane) (PBS-b-PDMS) in this work. The resulting PBS-b-PDMS was found to possess high molecular weight, narrow molecular weight distribution, and excellent combined performance. PBS-b-PDMS had good thermal properties. The decomposition temperature of 5% weight loss (T5%) increased from 324 to 344 °C, and the temperatures at the maximum weight loss rate (Tmax) values increased from 385.1 to 396.7 °C. The impact strength increased significantly from 7.8 kJ/m2 of PBS to 53.9 kJ/m2 of PBS-b-PDMS. As the PDMS block endows copolymers with low surface energy and good liquid resistance, PBS-b-PDMS has excellent antismudge, self-cleaning, and solvent resistance. Finally, to minimize the surface energy, PDMS blocks preferentially enrich the surface, which imparts the polymers with self-cleaning properties.

On the Mechanical, Thermal, and Rheological Properties of Polyethylene/Ultra-High Molecular Weight Polypropylene Blends

The novel ultra-high molecular weight polypropylene (UHMWPP) as a dispersed component was melt blended with conventional high-density polyethylene (PE) and maleic anhydride grafted-polyethylene (mPE) in different proportions through a kneader. Ultra-high molecular weight polypropylene is a high-performance polymer material that has excellent mechanical properties and toughness compared to other polymers. Mechanical, thermal, and rheological properties were presented for various UHMWPP loadings, and correlations between mechanical and rheological properties were examined. Optimal comprehensive mechanical properties are achieved when the UHMWPP content reaches approximately 50 wt%, although the elongation properties do not match those of pure PE or mPE. However, it is worth noting that the elongation properties of these blends did not match those of PE or mPE. Particularly, for the PE/UHMWPP blends, a significant drop in tensile strength was observed as the UHMWPP content decreased (from 30.24 MPa for P50U50 to 13.12 MPa for P90U10). In contrast, the mPE/UHMWPP blends demonstrated only minimal changes in tensile strength (ranging from 29 MPa for mP50U50 to 24.64 MPa for mP90U10) as UHMWPP content varied. The storage modulus of the PE/UHMWPP blends increased drastically with the UHMWPP content due to the UHMWPP chain entanglements and rigidity. Additionally, we noted a substantial reduction in the melt index of the blend system when the UHMWPP content exceeded 10% by weight.

Reactive Compatibilization of Polyamide 6/Olefin Block Copolymer Blends: Phase Morphology, Rheological Behavior, Thermal Behavior, and Mechanical Properties

In this study, the morphology, rheological behavior, thermal behavior, and mechanical properties of a polyamide 6 (PA6) and olefin block copolymer (OBC) blend compatibilized with maleic anhydride-grafted polyethylene-octene copolymer (POE-g-MAH) were investigated. The morphological observations showed that the addition of POE-g-MAH enhanced the OBC particle dispersion in the PA6 matrix, suggesting a better interfacial compatibility between the pure PA6 and OBC. The results of the Fourier transform infrared (FTIR) spectroscopy analysis and the Molau test confirmed the compatibilization reactions between POE-g-MAH and PA6. The rheological test revealed that the melt viscosity, storage modulus (G’), and loss modulus (G”) of the compatibilized PA6/OBC blends at low frequency were increased with the increasing POE-g-MAH content. The thermal analysis indicated that the addition of OBC had little effect on the crystallization behavior of PA6, while the incorporation of POE-g-MAH at high content (7 wt%) in the PA6/OBC blend restricted the crystallization of PA6. In addition, the compatibilized blends exhibited a significant enhancement in impact strength compared to the uncompatibilized PA6/OBC blend, in which the highest value of impact strength obtained at a POE-g-MAH content of 7 wt% was about 194% higher than that of pure PA6 under our experimental conditions.

Toughened High-Flow Polypropylene with Polyolefin-based Elastomers

Polyolefin is the most widely used and versatile commodity polymer. In this work, three types of polyolefin-based elastomers (PBEs) were adopted to toughen a high-flow polypropylene to improve its overall performance. The chain microstructures of these PBEs, including ethylene/1-octene (E/O) random copolymer from Dow Chemical′s polyolefin elastomer (POE), olefin block copolymers (OBCs) of E/O from Dow, and ethylene/propylene random copolymer from ExxonMobil’s propylene-based elastomer, were elucidated by GPC, ¹³C NMR, TREF, and DSC techniques. The mechanical, thermal and optical properties, and morphology analysis of the PP/PBE blends were also studied to investigate the toughening mechanism of these PBEs. The results showed that all three types of PBEs can effectively improve the Izod impact strength of the PP/PBE blends by the addition of the rubber compositions, at the cost of the stiffness. PBE-1 and PBE-2 were found to have a great stiffness–toughness balance with about 1700 MPa of flexural modulus, about 110 °C of HDT and 3.6 kJ/m² of impact strength on the prepared PP/PBE blends by forming separated rubber phase and refined spherulite crystals. As a result, the OBC with alternating hard and soft segments could achieve a similar toughening effect as the E/P random copolymer. Surprisingly, no obvious rubber phase separation was observed in the PP/PBE-4 blend, which might be due to the good compatibility of the E/P random chains with the isotactic PP; therefore, the PP/PBE blend obtains great toughness performance and optical transparency with the highest Izod impact strength of 4.2 kJ/m² and excellent transparency.

Synergistic toughening of polypropylene with ultra-high molecular weight polyethylene and elastomer-olefin block copolymers

Blends of polypropylene (PP) and ultra-high molecular weight polyethylene (UHMWPE) with elastomer-olefin block copolymers (OBC) were prepared using an ultrasonic twin-screw extruder, and the mechanical, thermal, and rheological properties of the blends were investigated. The interfacial interactions among PP, OBC, and UHMWPE showed that the PP/OBC/UHMWPE blends formed a core–shell structure with UHMWPE as the core and OBC as the shell. The crystallization temperature and the crystallinity of the blends were improved for the heterogeneous nucleation between PP- and OBC-covered UHMWPE particles. Moreover, the mechanical and thermal properties of PP/UHMWPE blends have also been greatly improved by adding OBC. Furthermore, it was evident that the OBC-covered HHMWPE particles became smaller under the application of ultrasonic irradiation, so the interfacial interactions between the particles and the PP matrix were enhanced and the impact strength of the blends was improved.

Blends of polypropylene (PP) and ultra-high molecular weight polyethylene (UHMWPE) with elastomer-olefin block copolymers (OBC) were prepared using an ultrasonic twin-screw extruder, and their mechanical and rheological properties were investigated.

Tuning the crystalline and mesophase structure of olefin block copolymer through self-nucleation and annealing treatments

As a type of novel semi-crystalline block copolymers, the final properties of olefin block copolymers (OBCs) greatly depend on the crystalline and phase-separated structures. In the present work, we systematically investigated the influence of self-nucleation and annealing on the lamellar and mesophase-separated structure of OBCs. According to the crystalline and melting behavior after self-nucleation and annealing treatments, four different regimes can be recognized with the self-seeding temperature Ts varying from 125 to 109 °C. In regime A, only self-nucleation occurs, while it coexists with lamellar thickening in regime B. In regime C, there is only lamellar thickening behavior. The lamellar thickening induced inconsecutive lamellar crystals observed revealed that the rearrangement of the hard blocks, which are next to the soft blocks and trapped in the intermediate regime between crystalline and amorphous phases, into neighboring lamellar crystals should be the mechanism for the lamellar thickening of the OBCs. Surprisingly, no lamellar thickening occurs and a new small melting peak appears at lower temperatures in regime D. Considering the block dispersity of OBCs, the emergence of a small melting peak at lower temperatures can be attributed to the crystallization of the ethylene sequence with relatively weaker crystallization abilities, which are not able to crystallize in a standard crystalline state. Based on these findings, we gained some new understandings on lamellar thickening behavior of OBCs and established the self-nucleation and annealing process as a powerful tool for tuning the crystalline and phase-separated structures of OBCs.

The effect of hard block content on the orientation and mechanical properties of olefin block copolymer films as obtained via melt stretching

In this study, the orientation, structure and mechanical performance of a series of uniaxially oriented films based on olefin block copolymers (OBC) have been investigated in terms of the differences in hard block content and draw ratio (DR).

Effect of melting temperature on interfacial interaction and mechanical properties of polypropylene (PP) fiber reinforced olefin block copolymers (OBCs)

Transcrystalline structures for the first time were observed at the interface of OBC/PP fiber, proving that the partially melted (170 °C) and totally melted (190 °C) PP fibers have stronger interactions with OBC than unmelted PP fibers does.