Thesis
Study of the effect of RF synthesis parameters on the superinsulating properties of xerogel composite blankets
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2020
- Thesis identifier
- T15765
- Person Identifier (Local)
- 201463064
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- Materials produced from the synthesis of resorcinol-formaldehyde (RF) gels, can be used in a wide range of applications, from contact lenses to water filtration media. As a result of their versatility, there is a need to control the properties of these materials to optimise their performance in such applications; this study investigates the effects of synthetic conditions on the final thermal conductivity of RF gel materials for use in insulation applications. Novel RF xerogel blankets, for use in insulation applications, were synthesised and studied. The xerogel blankets were fabricated by moulding a base-catalysed mixture of resorcinol-formaldehyde into a polyethylene terephthalate (PET) unwoven fibrous mat. The similar process was employed in the preparation of the parent RF xerogels, utilising identical processing conditions. Altering the formulation of the sol could significantly impact the nanoscale structure, and density of the resulting materials, therefore, their final properties, including thermal conductivity. Thermal conductivity measurements on the xerogel blankets were performed using a heat flow meter (HFM) assembly. The obtained results specify that the thermal conductivity of the composite blankets tends to decrease with increasing average pore size, towards a critical value, which is less than the mean free path of air. There is good evidence that the average pore size increases as the R/C ratio increases. Within the sample series examined, the bulk density of the materials is inversely proportional to thermal conductivity. However, when the density is below 280 kg/m3 , the thermal conductivity tends to increase. It was observed that the bulk density of the blankets decreases when the percentage of solids content decreases, and the molar R/C ratio increases. Altering the catalyst used in the synthetic process also resulted in slight changes in the textural characteristics, and thermal conductivities of the blankets. The RF xerogel blanket obtained using an R/C of 600, and a solids content of 30%, shows the lowest thermal conductivity ( 23.47 mW/m.K) among, those obtained using other conditions. In the case of subcritical dried RF organic gels (xerogel), the thermal conductivity measurements of both monolithic and powdered gels were performed using thermal iii analysis methods. The findings indicate that thermal conductivity decreases with decreasing density; however, limitations in the results obtained demonstrate the potential difficulties in obtaining a correlation between porous structure and thermal conductivity. Studies of the thermal behaviour of RF xerogels and their blankets indicates that these materials are thermally stable up to 300 °C (573 K). Thermal decomposition profiles reveal traces of moisture, released between 100-200 °C (373-473 K); which requires further treatment of the final products. The results obtained, which focus on the processing steps that can be used to tailor the texture of RF blankets by modifying the composition of the parent sol, demonstrate the potential of such routes to controlling and optimising the thermal conductivity of composite blankets for use as insulating materials.
- Advisor / supervisor
- Fletcher, Ashleigh
- Resource Type
- Note
- This thesis was previously held under Moratorium from 2nd December 2020 until 2nd December 2025.
- DOI
- Date Created
- 2020
- Former identifier
- 9912928791002996
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