Cyclic carbonates as green reactants for improving thermoplastic properties of lignocellulosic materials
Typ
Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Program
Innovative and sustainable chemical engineering (MPISC), MSc
Publicerad
2023
Författare
Tansatien, Rattanapon
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Lignocellulosic materials are attractive raw materials for producing thermoplastics with more sustainable
manufacturing. They come from a renewable source that can reduce the dependency on
conventional fossil-based feedstock and has good tensile properties. However, their polymeric chains
have poor mobility because of the multiple hydrogen bonds of their hydroxyl groups, which is an essential
obstacle for thermoplastic processing. To improve their thermoplasticity, their hydroxyl groups can
be converted by chemical modifications that introduce the side groups that can increase the flowability
of their chains. In this study, unbleached softwood kraft pulp was oxyalkylated with cyclic carbonates
(propylene carbonate and ethylene carbonate), acting as a reactant and medium. These two reactants
create low environmental impacts because of their biodegradability and low toxicity. In addition, they
are also safer compounds from their high boiling point, flash point, and vapor pressure. The influence
of temperature, catalysts, and reaction time were investigated. The molecular structures, purity, and
thermal properties of the modified products were also evaluated. The chemical modification with ethylene
carbonate provides the highest yields and appears to be the most effective pathway to substitute
hydroxyl groups with the alkyl side chains. In addition, the products from the chemical modifications
with ethylene carbonate have a higher purity and are easier to separate than the products from the
chemical modifications with propylene carbonate. Increasing the temperature and amount of catalyst
promotes the substitutions on the hydroxyl group. Finally, the modified pulp from chemical modification
with ethylene carbonate at a higher temperature and amount of catalyst has better thermal
properties than the unmodified pulp. The glass-transition temperature (Tg) of the modified pulp can
be detected at approximately 180 °C while the Tg of its raw material is above 220 °C, so the polymeric
chains of modified pulp become more flowable.
Beskrivning
Ämne/nyckelord
Lignocellulosic materials , thermoplasticity , oxyalkylation , propylene carbonate , ethylene carbonate , yields