Tan, Yi Wei
(2025)
Synthesis of starch nanocrystals with natural rubber derivatives in smart rubber for energy storage.
PhD thesis, University of Nottingham.
Abstract
The ever-increasing human population has raised concerns about the need for environmentally friendly, sustainable and reliable energy storage system. Natural rubber (NR) is an elastomer which exhibits unique properties such as reversible deformation, excellent mechanical strength and large strain storage capacity rendering it as a promising prospect to be developed as a smart material with energy storage potential. However, a few drawbacks of NR for instance poor oil resistivity had raised the use of synthetic rubbers produced from petrochemicals that caused environmental and health issues. To counter this circumstance, the development of novel specialty natural rubber (SPNR) have been garnering tremendous interest due to the importance of green concept of rubber. However, the physical and mechanical characteristics of epoxidized natural rubber (ENR) and deproteinized natural rubber (DPNR) both belong to the class of SPNR fabricated in the form of rubber latex (RL) films are rarely investigated. This research work aims to analyse temperature-triggered biobased smart rubber with enhanced mechanical strength for energy storage application. More precisely, the emphasis of this research is to discover the compatibility of starch nanocrystals (SNC) as reinforcement nanofiller in NR and its derivatives such as ENR and DPNR for wide range of working temperatures. Moreover, the shape memory effect (SME) of SNC reinforced RL films is yet to be explored. Majority of the current research works related to smart materials are shape memory alloys and other electro-responsive material which are seldom 100% biodegradable and possessed less flexibility. From the engineering perspective, it is also crucial to analyse and demonstrate the feasibility of a novel material before any specific application. Therefore, the physical and mechanical characteristics, shape memory behaviour as well as evaluating the energy storage capability of the fabricated smart rubbers are presented in this research.
To this end, the research was divided into three objectives: (i) experimental investigations which included characterization of SNC, physical and mechanical characteristics of sulphur-cured rubber films and SNC reinforced rubber composite films (ii) evaluation of the shape memory behaviour of sulphur-cured rubber films and SNC reinforced rubber composite films (iii) quantifying and demonstrating the energy storage potential of rubber nanocomposite films. The optimized acid hydrolysis technique was adopted to synthesize SNC from native waxy maize starch while latex casting is used to fabricate the temperature triggered smart rubber films. A series of characterization works were done to the synthesized SNC, sulphur-cured rubber films and SNC reinforced rubber composite films. For the second objective, shape memory testing was performed with a special elongation device to quantify the shape fixity (Sf) and shape recovery (Sr) of the smart rubber films. The energy stored within the smart rubber was quantified by cyclic loading-unloading test and manual experiment was performed to demonstrate the energy storage capability of the rubber nanocomposite films by lifting a load which then concludes the third objective.
In characterization of SNC, the synthesized SNC was found to be well dispersed and possessed a spherical shape with nano-dimension determined through morphological study and particle size analyser. Native waxy maize starch and SNC showed a typical A-type crystalline structure with 35% and 44% of relative crystallinity respectively. In terms of thermal behaviour, SNC displayed higher endothermic temperature peak than native starch as SNC was found to have a higher degree of crystallinity. For sulphur-cured rubber films, the following results were observed: (i) the crosslink density and tensile stress were found to increase while elongation at break decreases with higher loading of sulphur, (ii) increasing content of sulphur resulted in a decrease of swelling percentage in toluene, (iii) the samples exhibited a trend of maintaining in glassy state below its glass transition temperature (Tg) with decreasing storage modulus while Tg of ENRLs-based rubber films is higher than its NRLs counterpart. As for SNC reinforced rubber composite films, (i) SNC is well dispersed in the rubber matrices (ii) crosslink density and tensile stress increased with SNC content while incorporation of SNC maintained the deformability of the rubber nanocomposites films, (iii) water and toluene uptake of the rubber nanocomposites films were found to be in contrast with addition of SNC, (iv) comparable Tg was found in their respective RL types with incorporation of SNC, (v) two weight loss steps corresponding to degradation of SNC and rubber matrix were found from the thermogram.
For the second objective, in terms of shape memory behaviour, the most lightly crosslinked rubber films (0.2phr sulphur) was determined to exhibit the best overall SME. Therefore, all rubber nanocomposites films were crosslinked with 0.2 phr sulphur with varying SNC contents. The results suggested that incorporation of 8% SNC into the rubber composite films achieved Sf of the 93.3% while retained 100% Sr of the material. This outcome suggested that the rubber nanocomposite film is capable of storing strain at the elongated state which translated to the storage of certain amount of elastic deformation energy. Thus, from the findings of SME, third objective of the work investigate the energy storage potential of the rubber nanocomposite films. The greatest attained energy stored was calculated to be 20.91 MJ/m3 while manual experiment showed that the smart rubber was able to perform work by lifting a load in the vertical direction which is similar to the application of one-way actuator. This fabricated smart rubber is expected to possess environmentally friendly green energy storage capabilities and can be considered as an option for future energy storage.
It can be concluded that the smart rubber fabricated in this study possessed high mechanical properties, excellent SME and green energy storage potential. The SME and energy stored during the deformation process can be harnessed in various ways, broadening its potential application across multiple fields including soft robotics, self-deployable structures, medical devices and implants as well as energy storing devices. In all of these applications, smart rubber enables not only shape transformation but also the storage and release of mechanical energy making them highly versatile for both mechanical tasks and energy management solutions across various industries.
| Item Type: |
Thesis (University of Nottingham only)
(PhD)
|
| Supervisors: |
Chai, Ai-Bao
Tshai, Kim Yeow
Ho, Jee Hou
Kamaruddin, Shamsul
Andriyana, Andri |
| Keywords: |
smart rubber; shape memory effect (SME); starch nanocrystals (SNC); energy storage; natural rubber composites |
| Subjects: |
T Technology > TJ Mechanical engineering and machinery |
| Faculties/Schools: |
University of Nottingham, Malaysia > Faculty of Science and Engineering — Engineering > Department of Mechanical, Materials and Manufacturing Engineering |
| Item ID: |
80613 |
| Depositing User: |
Tan, Yi Wei
|
| Date Deposited: |
26 Jul 2025 04:40 |
| Last Modified: |
26 Jul 2025 04:40 |
| URI: |
https://eprints.nottingham.ac.uk/id/eprint/80613 |
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