Development of low cost thermal insulating materials

The disadvantaged people in South Africa are unfortunate by virtue of their financial status. It was estimated in 1992 that 20 % of the South African population live in informal settlements. The houses in these settlements are found to be very energy inefficient. This study was aimed at developing low cost thermal insulating materials that can be used to increase energy efficiency of the houses in these informal settlements. This was done by firstly studying the properties of thermal insulation materials. Furthermore, common thermal insulating materials in South Africa were studied and evaluated. Only recycled polymeric based materials were examined for selecting the raw materials that were used to investigate the feasibility of the thermal insulating materials from waste material. The experimental work was extended to construct a thermal conductivity rig that was to be used in measuring the thermal conductivity of both the developed and existing thermal insulating materials. The expanded polystyrene obtained from Sagex (Pty) Ltd and polyester obtained from Isotherm (Pty) Ltd. were evaluated and compared to the manufactured recycled polymer slabs and expanded polyethylene foams (EPEF). Expanded polyethylene foam and recycled polymer slab samples were subjected to mechanical and physical testing. A temperature comparison test and thermal conductivity determination were conducted on both the expanded polyethylene foam (EPEF) and recycled polymer slab (RPS) samples. The scanning electron microscope (SEM) was used to reveal the micro-structures of all the developed thermal insulating material samples. The expanded polystyrene and polyester thermal insulating materials were also examined using the SEM. Optical microscopy was only used on RPS samples. It was found in this research, that the properties that govern the viability of thermal insulating materials are: thermal conductivity (k-value), thermal resistance (R-value), combustibility, moisture absorption and the presence of hazardous gases during burning. The temperature comparison test showed that the recycled polymer slab (RPS) and expanded polyethylene foam (EPEF) retards the flow of heat to levels comparable to that of the locally obtained thermal insulation. The comparative cut bar method was found to be relatively cheap to design and it was ideal for the measurement of the thermal conductivity of polymeric based materials. The k-value of all the EPEF samples was measured to be around 0.04 W.m-¹K-¹ and the RPS k-value was found to be 0.05 W.m-¹K-¹. This is attributed to air pockets with lower conductivities values, found within the structure of the polymeric thermal insulating materials. The porous structure is evident from the SEM micrographs of both the EPEF and RPS samples. One grade of expanded polyethylene foam, the SPX80, had accumulated less moisture when moisture absorption was compared with other EPEF samples. The RPS material did have a propensity for absorption of water. The flammability retardant tests have showed that gypsum board has to be incorporated during service for the RPS and SPX80. The mechanical testing results also suggest that both the EPEF and RPS need to be supported when installed in a ceiling, for example.

Grantor dc:publisher.institution

Centre for Materials Engineering

Year dc:date.issued

2005

Author dc:creator

• Meletse, Thabo Frans

Advisor dc:contributor.advisor

• Marcus, Kashif

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/11427/8724

OAI identifier oai:identifier

oai:open.uct.ac.za:11427/8724