Blends of polyethylene (PE) and polypropylene (PP) have always been the subject of intense reasearch for encouraging polymer waste recycling while producing new materials for specific applications in a sustainable way. However, being thermodynamically immiscible, these polyolefins form a binary system usually exhibiting lower performances compared with those of the homopolymers. Many studies have been carried out to better understand the PE/PP blend compatibilization for developing a high-performance and costeffective product. Both nonreactive and reactive compatibilization promote the brittle to ductile transition for a PE/PP blend. However, the final product usually does not meet the requirements for high demanding commercial applications. Therefore, further PE/PP modification with a reinforcing filler, being either synthetic or natural, proved to be a good method for manufacturing high-performance reinforcend polymer blend composites, with superior and tailored properties. This review summarizes the recent progress in compatibilization techniques applied for enhancing the interfacial adhesion between PE and PP. Moreover, future perspectives on better understanding the influence of themodynamics on PE/PP synergy are discussed to introduce more effective compatibilization strategies, which will allow this blend to be used for innovative industrial applications.
Reinforcing polymers with particles and fibers has been a common strategy for decades, in order to make them suitable for high-demanding industrial applications. As composites often undergo dynamic loads, it is important to understand their behavior under such conditions. This review first classifies the types of polymer composites and then explains their failure behavior under tension and compression loading, followed by an overview of some of the experimental procedures used to characterize the polymer composites' dynamic mechanical performance. Afterward, the most significant findings in terms of the highstrain-rate compressive and tensile strength and modulus of polymer composites are thoroughly discussed. The results, available in the literature, on the mechanical properties of polymer composites under quasi-static conditions are also presented and compared with the high-strain-rate data. The differences are explained by discussing the changes in the structural configurations of polymer matrices under quasi-static and dynamic loads. Lastly, conclusions and future perspectives are given, with the intent of highlighting the most promising polymer composites that can be used for a wide variety of applications.
AbstractGraphene oxide (GO) was chemically modified in xylene with dodecyl amine and hydrazine monohydrate to obtain reduced functionalized graphene oxide (RFGO). Composites of high-density polyethylene (HDPE) and GO were made via solvent reaction, whereas both melt mixing and solvent reaction were used for HDPE-RFGO composites for comparison purposes. Elemental and thermal analysis showed the success of GO modification in grafting amine functionalities onto its structure and restoring most of the original graphene C=C bonds. A significant increase in mechanical properties, thermal stability, and crystallization behavior was observed for HDPE-RFGO (solvent) compared with HDPE and HDPE-GO, proving that homogeneous dispersion of RFGO in the polymer matrix and strong interactions between them resulted in facilitated stress transfer, delayed thermal degradation, and more efficient nucleating effect in inducing the crystal growth of HDPE. A comparison of HDPE-RFGO properties enhancement between the melt mixing method and the solvent reaction method showed that, apart from mechanical behavior, the RFGO contribution was the same, suggesting that the optimization of the ecofriendlier approach (melt) could eventually lead to its total use for the mass production of high-performance, cost-effective, and more environmentally friendly graphene-based thermoplastic polyolefin nanocomposites suitable for highly demanding industrial applications.
This research work is the first to report thermal stability, heat deformation resistance, and crystallization behavior of a Polyethylene (PE)-based biphasic polyolefin system reinforced with Reduced Graphene Oxide (RGO), which was obtained through Graphene Oxide (GO) chemical reduction. Polypropylene (PP) represented the polymeric dispersed phase. A strategic PE/PP/RGO manufacturing procedure was employed to thermodynamically localize RGO at the PE/PP interface, as confirmed by Transmission Electron Microscopy (TEM), bringing a uniform micro phase dispersion into the macro phase. In addition, studies of PE non-isothermal crystallization kinetics indicated that the morphology tunable micro phase and the nanolayered RGO promoted a nucleation-controlled PE crystallization, which was supported by Polarized Light Optical Microscopy (PLOM). This, together with fine morphology, justified the remarkable enhancement registered for the ternary system’s thermal stability and heat deformation resistance. Different filler loads were employed, with weight fractions of 2% and 4%. It was observed that the former, being better exfoliated and more homogeneously distributed at the PE/PP interface than the latter, led to a more improved PE crystallization, alongside a greater ternary system’s thermal properties. Moreover, the thermal stability of PE/PP reinforced with 2% of RGO was even higher than that of virgin PP, while their heat deformation resistance values were found to be similar. Therefore, this unique outcome provides industries, such as the energy and automotive sectors, with the opportunity to substitute PP-rich products with those mostly comprised of a cheaper, more abundant, yet performant PE.
This is the first study to showcase the use of maleic anhydride‐grafted polyethylene (MAPE) to compatibilize polyethylene (PE)‐rich blends, where polypropylene (PP) represents the minor phase. By first mixing PP with MAPE, and then adding PE, MAPE was assumed to be localized at the PE/PP interface. Microscopy analysis confirmed that MAPE led to a remarkably fine PE/PP/MAPE morphology, with PP being uniformly dispersed into PE and having an average diameter 267% smaller than that in the PE/PP blend. According to mechanical and rheological tests, this translated into a 14%, 20%, and 14% enhancement of tensile strength, tensile modulus, and tensile toughness, respectively, as well as a 10% and 20% drop in PE/PP viscosity mismatch and interfacial tension, respectively. Finally, PE/PP/MAPE tensile toughness and elongation at break were greater than those of virgin PP, while PE/PP/MAPE strength and stiffness were similar to the ones of neat PP. Therefore, this study provides industries with the possibility to utilize products rich in PE instead of those made of more expensive PP, while still keeping the level of performance high; hence, creating a paradigm shift in the development of advanced lightweight polyolefin materials with tuned functionalities.
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