Melt- vs. Non-Melt Blending of Complexly Processable Ultra-High Molecular Weight Polyethylene/Cellulose Nanofiber Bionanocomposite

Abstract

The major hurdle in melt-processing of ultra-high molecular weight polyethylene (UHMWPE) nanocomposite lies on the high melt viscosity of the UHMWPE, which may contribute to poor dispersion and distribution of the nanofiller. In this study, UHMWPE/cellulose nanofiber (UHMWPE/CNF) bionanocomposites were prepared by two different blending methods: (i) melt blending at 150 °C in a triple screw kneading extruder, and (ii) non-melt blending by ethanol mixing at room temperature. Results showed that melt-processing of UHMWPE without CNF (MB-UHMWPE/0) exhibited an increment in yield strength and Young’s modulus by 15% and 25%, respectively, compared to the Neat-UHMWPE. Tensile strength was however reduced by almost half. Ethanol mixed sample without CNF (EM-UHMWPE/0) on the other hand showed slight decrement in all mechanical properties tested. At 0.5% CNF inclusion, the mechanical properties of melt-blended bionanocomposites (MB-UHMWPE/0.5) were improved as compared to Neat-UHMWPE. It was also found that the yield strength, elongation at break, Young’s modulus, toughness and crystallinity of MB-UHMWPE/0.5 were higher by 28%, 61%, 47%, 45% and 11%, respectively, as compared to the ethanol mixing sample (EM-UHMWPE/0.5). Despite the reduction in tensile strength of MB-UHMWPE/0.5, the value i.e., 28.4 ± 1.0 MPa surpassed the minimum requirement of standard specification for fabricated UHMWPE in surgical implant application. Overall, melt-blending processing is more suitable for the preparation of UHMWPE/CNF bionanocomposites as exhibited by their characteristics presented herein. A better mechanical interlocking between UHMWPE and CNF at high temperature mixing with kneading was evident through FE-SEM observation, explains the higher mechanical properties of MB-UHMWPE/0.5 as compared to EM-UHMWPE/0.5.

Functionalized Fluoropolymer-Compatibilized Elastomeric Bilayer Composites for Osteochondral Repair: Unraveling the Role of Substrate Stiffness and Functionalities

“…In an effort to quantitatively analyze the role of the elastic modulus on cellular activity, the upregulation in the osteochondral functionalities is plotted against the elastic modulus (values in the log scale) in Figure . For benchmarking purposes, the elastic modulus for an identical grade of UHMWPE (267 ± 22.4 MPa) is taken from the literature . It is clear that the osteochondral induction and maturation can be modulated by tailoring the elastic modulus in the newly developed PVDF-TPU-BT-based hybrid composite, in a manner quantitatively better than commercial UHMWPE.…”

“…For benchmarking purposes, the elastic modulus for an identical grade of UHMWPE (267 ± 22.4 MPa) is taken from the literature. 35 It is clear that the osteochondral induction and maturation can be modulated by tailoring the elastic modulus in the newly developed PVDF-TPU-BT-based hybrid composite, in a manner quantitatively better than commercial UHMWPE. Any specific trend (linear) could not be established with the limited data points.…”

Performance evaluation of cellulose nanofiber reinforced polymer composites

“…This is because CNF materials are lighter in weight with a high surface area to volume ratio and higher strength and stiffness as compared to other micro-size fibers. It has been reported that CNF acts as a nucleating agent in a polymer matrix which improves the crystallinity and mechanical properties of the material [41][42][43]. Besides that, a small amount of CNF (1 wt.%-3 wt.%) is usually enough to significantly improve the mechanical performance of polymer composites.…”

“…However, this material has a relatively low Young's modulus which limits its applications. Sharip et al [42] had found that with the inclusion of 0.5% CNF in UHMWPE, the mechanical properties of the composite were improved as compared to neat UHMWPE. It was also found that the yield strength, elongation at break, Young's modulus and toughness of CNF/UHMWPE were higher by 28%, 61%, 47% and 45%, respectively, as compared to the neat UHMWPE.…”

Micromorphology and mechanical properties of UHMWPE/CNF composites under accelerated aging

“…[25] Compared with pure UHMWPE, the ratcheting strain rate of the composites is reduced by more than 24%, and a new viscoplastic constitutive model is proposed to describe the uniaxial ratcheting behavior. The properties of the composites mainly depend on their chemical composition and the morphological structure of the polymer on the microscale and heterogeneous system, [26][27][28][29] and the difference in the mechanical properties of UHMWPE and its composites before and after aging is also due to the difference in the microstructure caused by the thermal oxidation degradation of the polymer at low temperature. Many studies have been performed on the mechanical properties and creep properties of UHMWPE containing CNF.…”