Improving Performance Characteristics of Poly (Lactic Acid) (PLA) Based Nanocomposites by Enhanced Dispersion of Modified Cellulose Nanocrystals (CNCs)

Poly(lactic acid), (PLA) is a biodegradable and biocompatible polymer which has attracted significant attention as a promising substitute for petroleum-based polymers. To optimize the usage of PLA in a wide range of applications, different methods such as polymer blending and the incorporation of traditional and nanofillers have been extensively explored. Cellulose nanocrystals (CNCs), rod-like nanoparticles with a perfect crystalline structure, are considered as outstanding reinforcing agent owing to the excellent mechanical properties. The optimal characteristics of CNCs as a reinforcing agent in the polymer can be achieved through homogeneous dispersion within the polymeric matrix. However, the strong hydrophilic character of CNCs due to the presence of hydroxyl groups on the surface restricts the uniform dispersion of CNCs in the PLA matrix. In this work, three surface modification treatments along with two different mechanical preparation techniques were employed to improve the dispersion quality of CNCs in the PLA matrix. Polymer adsorption, green esterification, and time-efficient esterification were used as surface modification treatments. Solvent casting and spin-coating method were employed to prepare highly concentrated CNCs masterbatches. Nanocomposites were prepared using melt extrusion, followed by an injection molding process. The morphology of masterbatches indicated better CNCs dispersion through spin-coated thin films, suggesting a high evaporation rate and the effect of centrifugal force and surface tension in the spin-coating process decrease the possibility of CNCs aggregate through the film. Consequently, nanocomposites manufactured using spin-coated masterbatches exhibited higher mechanical strength in comparison with solvent cast ones. In the case of surface modification treatments, the most uniform CNCs dispersion was observed in the nanocomposites reinforced by valeric acid through esterification technique. Higher thermal stability was also achieved through the application of esterification technique. This observation was related to the presence of DMAP on the surface of CNCs which turns into inert materials, prohibiting the thermal degradation. The higher molecular weight and lower molecular number observed in spin-coated samples in comparison with film cast nanocomposites led to the higher damping behavior in spin-coated nanocomposites. This observation indicated the more viscoelastic properties in spin-coated samples owing to the presence of more polymer chain freedom in spin-coated nanocomposites.National Science Foundation (NSF)ND EPSCoR (Grant No.11A1355466

Recent advances in isolation, characterization, and potential applications of nanocellulose-based composites: A comprehensive review

Cellulose is the most abundant bio-inspired polymer derived from biomass with tremendous promises to expedite the sustainability and green transition. The interesting, fascinating, and applicable properties of nanocellulose-based structures including biocompatibility, low cost, high intrinsic strength, and extraordinary mechanical properties have opened new horizons for their advanced and emerging applications. This comprehensive review aimed to highlight different aspects of cellulose nanomaterials, ranging from preparation, classification, surface modification, nanocomposite fabrication, characterization, and their potential applications in various multifunctional, and high-performance products. This work also reviews the recent approaches applied to modify the surface chemistry of nanocellulose through functionalizing its surface hydroxyl groups to impart advanced desirable properties. Also, emerging applications of CNMs including biosensors, electromagnetic shielding, eco-friendly and sustainable packaging, and bio-medical fields are well demonstrated in this review

Cellulose nanocrystal based composites: A review

Cellulose nanocrystals (CNC) have received much attention as renewable, biodegradable, nontoxic, and low-cost nanomaterials with some remarkable properties. Desirable engineering properties of CNC include large surface to volume ratio, high tensile strength (~10 GPa), high stiffness (~110–130 GPa), and high flexibility. They can be chemically modified to tailor their properties for high-end engineering and biomedical applications. Despite their outstanding properties, the wide-scale application is lacking due to their surface characteristics and processing challenges. To achieve their full potential safer extraction methods, improved surface modification and functionalization methods and processing techniques are being researched. This review attempts to access methods for characterizing CNC, and CNC composites as well as their emerging new applications as smart materials. The review is a valuable resource for researchers and scientists working in industry or academia to provide an update on the use of CNC materials and their composites in packaging, biomedical, and high-efficiency energy systems

Investigation on the effect of build orientation and heat treatment on tensile strength and fracture mechanism of FDM 3D printed PLA

Three-dimensional (3D) printing is one of the many popular types additive manufacturing. Current FDM product has low tensile strength due to the printing orientation that affect to the low bonding layer by layer inside the material. Furthermore, experimental work of FDM using different printing orientation are still limited. The aim of this investigation is to characterize the effect of build orientation and heat treatment on the mechanical performance of PLA samples manufactured using fused deposition modelling (FDM) - 3D printer. Specimens were fabricated according to ASTM-D638 type IV. The next investigation was to analyse the effect of build orientation and heat treatment on the printed specimens. Tensile tests were carried out to determine the mechanical response of the printed specimens. The highest result for ultimate strength and yield strength achieved by heat-treated on-edge orientation, 47.84 MPa and 43.94 MPa respectively while the highest elastic modulus is untreated upright orientation, 8.96 GPa. The results showed that different orientations effect the behaviour of tensile strength and yield strength of the 3D printed PLA. Heat treatment process effected the layer bonding of the specimen as it strengthens the bonding between the layer. In addition, the results have highlighted different fracture behaviour for the upright orientation, on-edge and flat orientations

Role of Hybrid Nano-Zinc Oxide and Cellulose Nanocrystals on the Mechanical, Thermal, and Flammability Properties of Poly (Lactic Acid) Polymer

Biopolymers with universal accessibility and inherent biodegradability can offer an appealing sustainable platform to supersede petroleum-based polymers. In this research, a hybrid system derived from cellulose nanocrystals (CNCs) and zinc oxide (ZnO) nanoparticles was added into poly (lactic acid) (PLA) to improve its mechanical, thermal, and flame resistance properties. The ZnO-overlaid CNCs were prepared via the solvent casting method and added to PLA through the melt-blending extrusion process. The composite properties were evaluated using SEM, a dynamic mechanical analyzer (DMA), FTIR TGA, and horizontal burning tests. The results demonstrated that the incorporation of 1.5% nano-CNC-overlaid ZnO nanoparticles into PLA enhanced the mechanical and thermal characteristics and the flame resistance of the PLA matrix. Oxidative combustion of CNC-ZnO promoted char formation and flame reduction. The shielding effect from the ZnO-CNC blend served as an insulator and resulted in noncontinuous burning, which increased the fire retardancy of nanocomposites. By contrast, the addition of ZnO into PLA accelerated the polymer degradation at higher temperature and shifted the maximum degradation to lower temperature in comparison with pure PLA. For PLA composites reinforced by ZnO, the storage modulus decreased with ZnO content possibly due to the scissoring effect of ZnO in the PLA matrix, which resulted in lower molecular weight

Deterioration in the Physico-Mechanical and Thermal Properties of Biopolymers Due to Reprocessing

Biopolymers are an emerging class of materials being widely pursued due to their ability to degrade in short periods of time. Understanding and evaluating the recyclability of biopolymers is paramount for their sustainable and efficient use in a cost-effective manner. Recycling has proven to be an important solution, to control environmental and waste management issues. This paper presents the first recycling assessment of Solanyl, Bioflex, polylactic acid (PLA) and PHBV using a melt extrusion process. All biopolymers were subjected to five reprocessing cycles. The thermal and mechanical properties of the biopolymers were investigated by GPC, TGA, DSC, mechanical test, and DMA. The molecular weights of Bioflex and Solanyl showed no susceptible effect of the recycling process, however, a significant reduction was observed in the molecular weight of PLA and PHBV. The inherent thermo-mechanical degradation in PHBV and PLA resulted in 20% and 7% reduction in storage modulus, respectively while minimal reduction was observed in the storage modulus of Bioflex and Solanyl. As expected from the Florry-Fox equation, recycled PLA with a high reduction in molecular weight (78%) experienced 9% reduction in glass transition temperature. Bioflex and Solanyl showed 5% and 2% reduction in molecular weight and experienced only 2% reduction in glass transition temperature. These findings highlight the recyclability potential of Bioflex and Solanyl over PLA and PHBV

Recent advances in cellulose nanofibers preparation through energy-efficient approaches: A review

Cellulose nanofibers (CNFs) and their applications have recently gained significant attention due to the attractive and unique combination of their properties including excellent mechanical properties, surface chemistry, biocompatibility, and most importantly, their abundance from sustainable and renewable resources. Although there are some commercial production plants, mostly in developed countries, the optimum CNF production is still restricted due to the expensive initial investment, high mechanical energy demand, and high relevant production cost. This paper discusses the development of the current trend and most applied methods to introduce energy-efficient approaches for the preparation of CNFs. The production of cost-effective CNFs represents a critical step for introducing bio-based materials to industrial markets and provides a platform for the development of novel high value applications. The key factor remains within the process and feedstock optimization of the production conditions to achieve high yields and quality with consistent production aimed at cost effective CNFs from different feedstock.</jats:p

Recent Advances in Cellulose Nanofibers Preparation through Energy-Efficient Approaches: A Review

Cellulose nanofibers (CNFs) and their applications have recently gained significant attention due to the attractive and unique combination of their properties including excellent mechanical properties, surface chemistry, biocompatibility, and most importantly, their abundance from sustainable and renewable resources. Although there are some commercial production plants, mostly in developed countries, the optimum CNF production is still restricted due to the expensive initial investment, high mechanical energy demand, and high relevant production cost. This paper discusses the development of the current trend and most applied methods to introduce energy-efficient approaches for the preparation of CNFs. The production of cost-effective CNFs represents a critical step for introducing bio-based materials to industrial markets and provides a platform for the development of novel high value applications. The key factor remains within the process and feedstock optimization of the production conditions to achieve high yields and quality with consistent production aimed at cost effective CNFs from different feedstock