Bio-Based Resins and Green Composites from Renewable Resources

Arunjunai-Raj Mahendran

Research output: ThesisDoctoral Thesis

Abstract

The present work is focused on preparing bio-based thermoset resins from renewable resources like vegetable oils, lignins and also utilizing sustainable, renewable natural fibers as reinforcement for preparing green composites. The epoxy resin from the linseed oil was synthesized by converting the double bonds of the linseed oil into oxirane ring in the presence of “Lipase B” enzyme catalyst. The synthesized epoxidized linseed oil was cured with anhydride and polyamide hardener from renewable resources. The maleic anhydride grafted linseed oil was synthesized and utilized as anhydride hardener. Tall oil dimer fatty acid derived commerical resin was used as polyamide hardener. The cured network obtained using maleinated linseed oil was soft and flexible hence to improve the crosslink density and heat distortion temperature, the epoxidized linseed oil was cured with cyclic anhydride in the presence of imidazole initiator. The cure kinetics was studied using different model free kinetic methods. The vitrification was observed at the lower heating rate and a quick fall in complex heat capacity in the alternating differential scanning calorimetry showed the evidence of vitrification at the lower heating rate. The bio-based acrylate resin using vegetable oil was synthesized by reacting epoxidized linseed oil with acrylic acid. The synthesized resin was photocured in the presence of three different photoinitiator and the cure characteristics under UV lamp were monitored using real-time FTIR. To test the coating properties, synthesized acrylated linseed oil was coated on a wood substrate and the coatings showed glossy finish with very good adhesion. The bio-based acrylate resin is free of VOC hence they can be utilized as a green coating resin for the heat sensitive substrates. The isocyanate free urethane resin using vegetable oil was synthesized by converting the epoxidized linseed oil into five membered cyclic carbonate through carbon dioxide insertion. The cyclic carbonate was reacted with phenalkamine from renewable resource and the real-time FTIR analysis showed the aminolyis reaction between cyclic carbonate and phenalkamine with the occurrence of urethane linkage. The synthesized non-toxic isocyanate free urethanes can be used for environmental friendly flexible coating application. A bio-based thermosetting resin using lignin was synthesized by substituting some percentage of phenol with lignin in the phenol formaldehyde composition. The cure kinetics of kraft lignin modified phenol-formaldehyde was studied in the presence of cure accelerator using model free kinetic method. The results showed that, potassium carbonate has accelerated the rate of cure and an increase in additive concentration (4 %) has reduced the curing time to almost 50 %. Another novel lignin-phenol formaldehyde binder having a lignin content of 30 % was synthesized using methylolated lignosulfonate. The lignin binder was used as matrix resin for the natural fiber reinforced composites. The binder resins had a very good fiber/matrix interaction with kenaf and wood fibers but less interaction with the flax fiber. The increase in binder composition has increased both the flexural strength and modulus of the composites. Eco-friendly green composites were made using VOC free acrylic binder and natural fiber reinforcement. The thermal decomposition kinetic of the composites was studied using model free kinetic method. The result showed that decomposition of hemicellulose occurs first and it is being followed by cellulose and ester decomposition of acrylic binder. The results indicated that the vegetable oil is a potential renewable material which can yield bio-based resins and lignin can reduce the amount of toxic phenol usage in the phenol formaldehyde resin. Finally eco-friendly green composites having good mechanical properties and thermal stabilities were also obtained through natural fib
Translated title of the contributionBio-basierende Harze und umweltfreundliche Verbundwerkstoffe aus nachwachsenden Rohstoffen
Original languageEnglish
QualificationDr.mont.
Supervisors/Advisors
  • Aust, Nicolai, Supervisor (internal)
  • Pinter, Gerald Gerhard, Assessor A (internal)
Publication statusPublished - 2013

Bibliographical note

embargoed until null

Keywords

  • renewable resources
  • vegetable oils
  • lignin
  • thermoset
  • coatings
  • curing kinetics
  • natural fiber reinforced composite

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