Toughening of polylactic acid using styrene ethylene butylene styrene: Mechanical, thermal, and morphological studies

Tailoring PLA/ABS Blends Compatibilized with SEBS-g-MA through Annealing Heat Treatment

In this work, blends based on poly (lactic acid) (PLA)/acrylonitrile-butadiene-styrene (ABS) compatibilized with maleic anhydride-grafted (SEBS-g-MA) were prepared in a co-rotational twin-screw extruder by varying the concentrations of the compatibilizing agent. The influence of the compatibilizing agent on the morphology, mechanical, thermal, thermomechanical, and rheological properties of the prepared materials was analyzed. The effect of annealing on the properties of the blends was also investigated using injection-molded samples. The X-ray diffraction (XRD) results proved that the increments in crystallinity were an effect of annealing in the PLA/ABS/SEBS-g-MA blends, resonating at higher heat deflection temperatures (HDTs). The impact strength of the PLA/ABS blends compatibilized with 10 wt% SEBS-g-MA was significantly increased when compared to the PLA/ABS blends. However, the hardness and elastic modulus of the blends decreased when compared to neat PLA. The refined morphology shown in the scanning electron microscopy (SEM) analyses corroborated the improved impact strength promoted by SEBS-g-MA. The torque rheometer degradation study also supported the increased compatibility between SEBS-g-MA, PLA, and ABS. The TGA results show that the PLA/ABS and PLA/ABS/SEBS-g-MA blends are more thermally stable than the neat PLA polymer at higher temperatures. The results showed that the ideal composition is the heat-treated PLA/ABS/SEBS-g-MA (60/30/10 wt%), given the high impact strength and HDT results. The results of this work in terms of mechanical improvement with the use of compatibilizers and annealing suggest that the PLA/ABS/SEBS-g-MA system can be used in the production of 3D-printing filaments.

The Cellular Structure and Toughness of Hydrogenated Styrene-Butadiene Block Copolymer Reinforced Polypropylene Foams

Polypropylene nanocomposites containing varying amounts of Styrene-ethylene-butadiene-styrene block copolymer (SEBS) were prepared through the supercritical nitrogen microcellular injection-molding process. Maleic anhydride (MAH)-grafted polypropylene (PP-g-MAH) copolymers were used as compatibilizers. The influence of SEBS content on the cell structure and toughness of the SEBS/PP composites was investigated. Upon the addition of SEBS, the differential scanning calorimeter tests revealed that the grain size of the composites decreased, and their toughness increased. The results of the rheological behavior tests showed that the melt viscosity of the composite increased, playing a role in enhancing the cell structure. With the addition of 20 wt% SEBS, the cell diameter decreased from 157 to 66.7 μm, leading to an improvement in the mechanical properties. Compared to pure PP material, the impact toughness of the composites rose by 410% with 20 wt% of SEBS. Microstructure images of the impact section displayed evident plastic deformation, effectively absorbing energy and improving the material’s toughness. Furthermore, the composites exhibited a significant increase in toughness in the tensile test, with the foamed material’s elongation at break being 960% higher than that of pure PP foamed material when the SEBS content was 20%.

Thermal and Mechanical Assessment of PLA-SEBS and PLA-SEBS-CNT Biopolymer Blends for 3D Printing

Polylactic acid (PLA) is one of the most promising biopolymers often used as a raw material in 3D printing in many industrial areas. It has good mechanical properties, is characterized by high strength and stiffness, but unfortunately, it has some disadvantages; one is brittleness, and the other is slow crystallization. Amounts of 1–5% SEBS (styrene-ethylene-butylene-styrene) thermoplastic elastomer were blended into the PLA and the thermal and mechanical properties were investigated. DSC (Differential Scanning Calorimetry) measurements on the filaments have shown that SEBS increases the initial temperature of crystallization, thereby acting as a nucleating agent. The cooling rate of 3D printing, on the other hand, is too fast for PLA, so printed specimens behave almost amorphously. The presence of SEBS increases the impact strength, neck formation appears during the tensile test, and in the bending test, the mixture either suffers partial fracture or only bends without fracture. Samples containing 1% SEBS were selected for further analysis, mixed with 0.06 and 0.1% carbon nanotubes (CNTs), and tested for thermal and mechanical properties. As a result of CNTs, another peak appeared on the DSC curve in addition to the original single-peak crystallization, and the specimens previously completely broken in the mechanical tests suffered partial fractures, and the partially fractured pieces almost completely regained their original shape at the end of the test.

Poly (lactic acid) blends: Processing, properties and applications

Poly (lactic acid) or polylactide (PLA) is a commercial biobased, biodegradable, biocompatible, compostable and non-toxic polymer that has competitive material and processing costs and desirable mechanical properties. Thereby, it can be considered favorably for biomedical applications and as the most promising substitute for petroleum-based polymers in a wide range of commodity and engineering applications. However, PLA has some significant shortcomings such as low melt strength, slow crystallization rate, poor processability, high brittleness, low toughness, and low service temperature, which limit its applications. To overcome these limitations, blending PLA with other polymers is an inexpensive approach that could also tailor the final properties of PLA-based products. During the last two decades, researchers investigated the synthesis, processing, properties, and development of various PLA-based blend systems including miscible blends of poly l-lactide (PLLA) and poly d-lactide (PDLA), which generate stereocomplex crystals, binary immiscible/miscible blends of PLA with other thermoplastics, multifunctional ternary blends using a third polymer or fillers such as nanoparticles, as well as PLA-based blend foam systems. This article reviews all these investigations and compares the syntheses/processing-morphology-properties interrelationships in PLA-based blends developed so far for various applications.