Synthesis of thermoplastic cellulose grafted polyurethane from regenerated cellulose
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ORIGINAL RESEARCH
Synthesis of thermoplastic cellulose grafted polyurethane from regenerated cellulose De-Fa Hou . Huang Tan . Meng-Lei Li . Yue Tang . Zheng-Ying Liu . Wei Yang . Ming-Bo Yang
Received: 10 February 2020 / Accepted: 8 August 2020 Ó Springer Nature B.V. 2020
Abstract Due to the fact that natural cellulose cannot be melted, it is still challenging to process this biopolymer via thermoplastic processing methods. Herein, polycaprolactone diol was grafted onto regenerated cellulose (RC) via hydroxyl/isocyanate chemistry in dimethyl sulfoxide to endow cellulose with thermoplasticity. By adjusting the reaction parameters including the feeding ratios of reactants and reaction time, several homogeneous cellulose grafted polyurethanes (RC-g-PU) with the degree of substitution (DS) ranging from 0.49 to 1.48 and degree of polymerization ranging from 1.84 to 3.3 were synthesized. The thermoplasticity of the obtained RC-g-PU was well characterized by differential scanning calorimetry and optical microscope. The results revealed that the prepared RC-g-PU with DS values ranging from 1.01 to 1.48 can be melted at above 168.4 °C because PU side chains can serve as internal plasticizers and prevent the restacking of cellulose chains. Eventually, the synthesized thermoplastic RC-
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10570-020-03389-y) contains supplementary material, which is available to authorized users. D.-F. Hou H. Tan M.-L. Li Y. Tang Z.-Y. Liu W. Yang M.-B. Yang (&) College of Polymer Science and Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu 610065, People’s Republic of China e-mail: [email protected]
g-PU can be processed into transparent films by hotpressing at 170 °C. Therefore, this research constructs a melt-processable cellulose derivative by a simple and engineering method. Keywords Regenerated cellulose Isocyanate Polycaprolactone diol Grafting reaction Meltingprocessing
Introduction In recent years, environmentally friendly materials have drawn increasing attention due to the depletion of non-renewable resources and the pollution caused by petroleum-based polymers, among which cellulose is the most attractive biopolymer due to its abundance, renewability, biodegradability, and no-toxicity (Klemm et al. 2005; Kontturi et al. 2018; Rol et al. 2019). However, cellulose is insoluble in conventional solvents and also not melt-processable because of the close packing of cellulose chains through numerous hydrogen bonds (Onwukamike et al. 2017; Petridis and Smith 2018). To date, the industrial processing and practical applications of cellulose materials (membranes, textiles, coatings, and nano-particles) are generally achieved with the assistance of hazardous solvents such as carbon disulfide, cuprammonium, and mineral acid aqueous solution, which cause
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substantial environmental issues (Medronho and Lindman 2015; Wan
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