One-step twin-screw extrusion process of cellulose fibers and hydroxyethyl cellulose to produce fibrillated cellulose biocomposite

Hesam Taheri,Maiju Hietala,Kristiina Oksman

doi:10.1007/s10570-020-03287-3

Hesam Taheri, Maiju Hietala + Show 1 more

Open Access

https://doi.org/10.1007/s10570-020-03287-3

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Abstract

In this work, the defibrillation of cellulose fibers (CF) in the presence of hydroxyethyl cellulose (HEC) within the one-step twin-screw extrusion (TSE) process was examined. The effect of the TSE on cellulose fiber size reduction as well as CF-HEC biocomposites properties were investigated. The results showed that the TSE of cellulose fiber-hydroxyethyl cellulose (CF-HEC) with different cellulose fiber contents (50, 65, and 80 wt%) resulted in partial defibrillation of the cellulose fibers. The fractionation test of the cellulose fibers confirmed that their size was reduced and some fibrillation was observed in microscopy studies. The maximum width reduction of 46% occurred with 80 wt% cellulose content. However, the partial width reduction was also observed with 50% and 65 wt% of cellulose contents. Based on rheological measurements, the shear-viscosity trend of CF-HEC dispersion abruptly dropped when higher fiber content (80 wt%) was extruded, which was related to the fibrillation of the cellulose fibers as well as the reduction of the length. The extruded CF-HEC materials (powder form) were compression molded to prepare the biocomposites with different cellulose fiber contents (50, 65, and 80 wt%). The extruded CF-HEC powders were diluted with addition extra HEC to make biocomposites with lower fiber content (20%, 30%, and 40 wt%) and compression molded to study how the size reduction of the cellulose fibers affected the mechanical properties of biocomposites. The results showed that the E-modulus improved from 0.4 GPa of the neat HEC to 1.6 GPa for the composite with 40 wt% CF. Interestingly, the tensile strength of CF-HEC biocomposite with 40 wt% confirmed a clear improvement from 9.8 to 26.6 MPa, confirming good interaction between HEC and CF.Graphic abstract Preparation (mixing, TSE, and hot-pressing) and characterization (FE-SEM, rheometry, and tensile test) of CF-HEC biocomposite

Highlights

The annual biomass production of cellulosic materials is more than 1 trillion tons (Siroand Plackett 2010), with an unexhausted source that can be replaced by photosynthesis without affecting feedstock
Micrographs of 5 different fractions of the EX-50CF, EX65CF, and EX-80CF after the twin-screw extrusion (TSE) are compared with non-extruded cellulose fibers (CF); all the studied fiber dispersions had same cellulose concentration, 0.3 wt%
The one-step TSE process reduced the size of the CFs, and the higher CF content resulted in greater fibrillation probably due to the higher shear forces on the fibers during the TSE

Summary

Introduction

The annual biomass production of cellulosic materials is more than 1 trillion tons (Siroand Plackett 2010), with an unexhausted source that can be replaced by photosynthesis without affecting feedstock. Nowadays, fibrillated cellulose biocomposites are in the spotlight due to their extraordinary features, such as physical, chemical (Foster et al 2018), mechanical (Hietala et al 2011a), and optical properties (Simao et al 2015) and due to the availability of raw sources, such as wood, wood pulps and rejected or side-products of industry (Wu et al 2018). In this regard, there is a high propensity to increase the proportion of renewable resources in fiber-polymer matrix biocomposites. The overall scenario of cellulose-based biocomposites can be focused on the defibrillation of cellulose fibers and their suitable dispersion or distribution in a new (bio)polymer matrix (Osong et al 2016)

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