Abstract
The amidine organocatalyst 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) is an effective nucleophilic catalyst. Biocomposites with tuneable properties were successfully synthesized by ring-opening graft polymerization (ROGP) of propylene carbonate (PC) onto xylan using DBU as a catalyst in the ionic liquid (IL) 1-allyl-3-methylimidazolium chloride ([Amim]Cl). The effects of reaction temperature, reaction time and the molar ratio of PC to anhydroxylose units (AXU) in xylan were investigated. The physico-chemical properties of xylan-graft-poly(propylene carbonate) (xylan-g-PPC) copolymers were characterised by FT-IR, NMR, TGA/DTG, AFM and tensile analysis. The FT-IR and NMR results indicated the successful attachment of PPC onto xylan. TGA/DTG suggested the increased thermal stability of xylan after the attachment of PPC side chains. AFM analysis revealed details about the molecular aggregation of xylan-g-PPC films. The results also showed that with the increased DS of xylan-g-PPC copolymers, the tensile strength and Young’s modulus of the films decreased, while the elongation at break increased.
Highlights
The depletion of non-renewable energy and increasing environmental changes have stimulated human beings to tailor environmentally benign polymer replacements___biocomposites [1,2].Biocomposites are the combination of a biodegradable polymer as the matrix material and biodegradable fillers [2,3,4]
The xylan-g-PPC copolymers were tailored by varying the reaction conditions, including reaction temperature, reaction time and the molar ratio of anhydroxylose units (AXU) in xylan to propylene carbonate (PC) (Table 1)
The results indicated that the xylan derivatives with degree of substitution (DS) 0.24–0.47 and degree of polymerization (DP) 1.31–1.73 were obtained under the selected conditions
Summary
Biocomposites are the combination of a biodegradable polymer as the matrix material and biodegradable fillers (e.g., lignocellulosic) [2,3,4]. Lignocellulose has been recognized as the most important source for a broad variety of advanced polymeric materials for its excellent biodegradability, renewability, availability, acceptable mechanical and thermal properties compared to traditional carbon or aramid fibers [1,2,5,6]. Unlike cellulose which has a unique structure, hemicelluloses are heterogeneous polymers and the term is used to describe a group of polysaccharides composed of a combination of 5- and 6-carbon ring sugars. Stimulated by the shortage of natural energy sources, the structural variety and diversity of hemicelluloses has become more attractive, as they can be utilized in native or modified forms in biocomposites [9]. The interactions between natural fibers and the polymeric matrix play a key role in biocomposites’
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