Research on the Strengthening Advantages on Using Cellulose Nanofibers as Polyvinyl Alcohol Reinforcement.

Quim Tarrés,Pere Mutjé,Helena Oliver-Ortega,F Xavier Espinach,Manel Alcalà,Marc Delgado-Aguilar

doi:10.3390/polym12040974

Abstract

The present work aims to combine the unique properties of cellulose nanofibers (CNF) with polyvinyl alcohol (PVA) to obtain high-performance nanocomposites. CNF were obtained by means of TEMPO-mediated ((2,2,6,6-Tetramethylpiperidin-1-yl)oxyl) oxidation, incorporated into the PVA matrix by means of compounding in a single-screw co-rotating internal mixer and then processed by means of injection molding. It was found that CNF were able to improve the tensile strength of PVA in 85% when 4.50 wt % of CNF were added. In addition, the incorporation of a 2.25 wt % of CNF enhanced the tensile strength to the same level that when 40 wt % of microsized fibers (stone groundwood pulp, SGW) were incorporated, which indicated that CNF possessed significantly higher intrinsic mechanical properties than microsized fibers. SGW was selected as reference for microsized fibers due to their extended use in wood plastic composites. Finally, a micromechanical analysis was performed, obtaining coupling factors near to 0.2, indicating good interphase between CNF and PVA. Overall, it was found that the use of CNF is clearly advantageous to the use of common cellulosic fibers if superior mechanical properties are desired, but there are still some limitations that are related to processing that restrict the reinforcement content at low contents.

Highlights

The main objective of a composite, resulting from the combination between two or more materials, is to obtain a new material with unique properties, based on the combination and synergies that were provided by the original ones, as well as reducing production costs and environmental impacts [1,2,3].In this search, several thermoplastic and thermosetting polymers have been reinforced with a wide variety of fillers, both for technical and economic purposes
This specific surface area indicates that the presence of free hydroxyl groups at the surface of the cellulose nanofibers (CNF) is significantly high, glimpsing that the ability to bond polyvinyl alcohol (PVA) will be notable by means of hydrogen bonding due to its chemical structure
Biodegradable PVA nanocomposites reinforced with CNF have been prepared and tested

Summary

Introduction

The main objective of a composite, resulting from the combination between two or more materials, is to obtain a new material with unique properties, based on the combination and synergies that were provided by the original ones, as well as reducing production costs and environmental impacts [1,2,3].In this search, several thermoplastic and thermosetting polymers have been reinforced with a wide variety of fillers, both for technical and economic purposes. Glass, carbon, or aramid fibers are typical fillers for such thermoplastic materials [4,5] These composite materials, due to their greater characteristics when compared to the neat matrix, are currently being commercialized and accepted by the market, to the point that they are even considered as commodities (i.e., polypropylene reinforced with 30% of glass fibers). They exhibit excellent mechanical properties, they present important drawbacks and limitations related to their low recyclability, unhealthy manipulation of the reinforcement, and null sustainability [6].

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Results

Conclusion