Foam templated macroporous polymers and polymer composites
File(s)
Author(s)
Song, Wenzhe
Type
Thesis
Abstract
A blowing agent and stabiliser free method – foam templating method – has been introduced to manufacture bio-based epoxy foams. In order to widen the potential applications of the foam templated macroporous polymers, three major challenges have been successfully addressed in this thesis: (i) increase the porosity of the foam templated macroporous polymers above the state of the art; (ii) enhance the fracture resistance and impact toughness of the foam templated macroporous polymers; and (iii) improve the mechanical performance of the foam templated macroporous polymers.
The thesis starts from increasing the porosity of foam templated macroporous polymers. By using heat-induced bubble expansion, the porosity has been successfully increased from 71% to 85% without introducing any blowing agents or stabilisers. Correspondingly, the compressive modulus and strength decrease from 231 MPa and 5.9 MPa to 58 MPa and 1.9 MPa. The influence of the curing conditions on the mechanical properties and the deformation of the pores based on in-situ SEM micro-compression test are also discussed.
Hollow elastomeric microspheres are used to enhance the fracture resistance and impact toughness of the foam templated macroporous polymers. A 15% increase in critical stress intensity factor and 33% increase in Charpy impact strength are achieved, and the failure behaviour of the epoxy foams changes from catastrophic failure to progressive failure. More importantly, the compressive properties of the toughened epoxy foams are not compromised.
Short carbon fibres are used to improve the mechanical properties of the foam templated macroporous polymers. After short mixing time of 20 s, the carbon fibres are still mostly in tow form, and 58% and 10% increase in compressive modulus and strength along the fibre orientation direction are observed. By optimising the mixing process and prolonging the mixing time to 2 min, the single carbon fibres are successfully individualised from the original fibre tows, leading to more significant improvement – 165% and 53% increase in compressive modulus and strength. The highest compressive modulus and strength achieved are 845 MPa and 14.8 MPa.
The thesis starts from increasing the porosity of foam templated macroporous polymers. By using heat-induced bubble expansion, the porosity has been successfully increased from 71% to 85% without introducing any blowing agents or stabilisers. Correspondingly, the compressive modulus and strength decrease from 231 MPa and 5.9 MPa to 58 MPa and 1.9 MPa. The influence of the curing conditions on the mechanical properties and the deformation of the pores based on in-situ SEM micro-compression test are also discussed.
Hollow elastomeric microspheres are used to enhance the fracture resistance and impact toughness of the foam templated macroporous polymers. A 15% increase in critical stress intensity factor and 33% increase in Charpy impact strength are achieved, and the failure behaviour of the epoxy foams changes from catastrophic failure to progressive failure. More importantly, the compressive properties of the toughened epoxy foams are not compromised.
Short carbon fibres are used to improve the mechanical properties of the foam templated macroporous polymers. After short mixing time of 20 s, the carbon fibres are still mostly in tow form, and 58% and 10% increase in compressive modulus and strength along the fibre orientation direction are observed. By optimising the mixing process and prolonging the mixing time to 2 min, the single carbon fibres are successfully individualised from the original fibre tows, leading to more significant improvement – 165% and 53% increase in compressive modulus and strength. The highest compressive modulus and strength achieved are 845 MPa and 14.8 MPa.
Version
Open Access
Date Issued
2018-08
Date Awarded
2019-01
Copyright Statement
Creative commons attribution Non commercial licence No derivatives license
Advisor
Lee, Koon-Yang
Sponsor
Department of Aeronautics, Imperial College London
China Scholarship Council (CSC)
Publisher Department
Department of Aeronautics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)