期刊
CELLULOSE
卷 28, 期 17, 页码 10875-10889出版社
SPRINGER
DOI: 10.1007/s10570-021-04219-5
关键词
Cellulose nanocrystal; Acrylic monomers; Isocyanate; Surface modification; Reaction conditions; Polymer nanocomposite
资金
- P3Nano program in the US Endowment for Forestry and Communities [16-JV-11111106-052]
Cellulose nanocrystals (CNCs) were modified with isocyanoethyl methacrylate (IEM) to optimize their surface properties, achieving high surface hydroxyl conversion and crystallinity through controlled reaction conditions. The copolymerization of modified CNCs with acrylic monomers enhanced the dispersion and mechanical properties in an acrylic polymer matrix, showing significant improvements in tensile strength and hardness compared to unmodified CNCs.
Cellulose nanocrystals (CNCs) are crystalline nano-rods that have high specific strength with hydroxyl surface chemistry. A wide range of chemical modifications have been performed on the surface of CNCs to increase their potential to be used in applications where compatibilization with other materials is required. Understanding the surface chemistry of CNCs and critically examining the functionalization technique are crucial to enable control over the extent of modification and the properties of CNCs. This work aims to optimize the surface modification of wood-derived CNCs with isocy anatoethyl methacrylate (IEM), a bifunctional molecule carrying both isocyanate and vinyl functional groups. We studied the effect of modification reaction time and temperature on the degree of substitution, crystallinity, and morphology of the CNCs. We found that the degree of modification is a strong and increasing function of reaction temperature over the range studied. However, the highest temperature (65 degrees C) and the longest time of reaction (6 h) resulted in shorter, thinner, and less crystalline CNCs. We obtained surface hydroxyl conversion of 60.1 +/- 6% and percent crystallinity of 84% by keeping the reaction shorter (30 min) at 65 degrees C. Also, the copolymerization ability of modified CNCs was verified by polymerizing attached IEM groups with acrylic monomers via solution polymerization. The polymer-grafted CNCs (6% w/w) dispersed better in an acrylic polymer matrix compared to unmodified CNCs (umCNCs), resulting in approximately 100% improvement in the tensile strength and about 53% enhancement in the hardness of the acrylic, whereas addition of 6% w/w umCNCs did not influence the strength and hardness. [GRAPHICS] .
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