PHYSICO-CHEMICAL STUDIES ON PLASTICS WITH SPECIAL REFERENCE TO THEIR APPLICATIONS IN BUILDINGS.

Abstract

Shortage of traditional materials emphasises the need of introducing new building materials to supplement them with the best possible advantages. Plastics are one such new materials which offer groat potential for use in buildings. They possess a good combination of physico-raeclianical properties not exhibited generally by conventional building materials such as light weight, transparency good electrical insulating properties, low moisture absorption, low thermal conductivity and chemical resistance. In fact, plastics can be tailor-made to suit a particular requirement. Glass fibre reinforced polyester sheets are an important class of plastics finding a variety of applications in building industry particularly as roof lighting, partitions, decorative fixtures, bathroom accessories and concrete pouring forms etc. Since in most of these applications these sheets are used exposed to various natural agencies such as heat, light, moisture and oxygen, their weathering performance is of great importance. Since these are relatively new materials not much is known about their weathering behaviour particularly so in our climatic conditions. Reinforced plastics are heterogeneous systems involving two components the resin and the glass fibres requiring good adhesion of the resin to reinforcement. Durability of these sheets will depend to a : iv s great extent upon the bond conditions existing at the glass/resin interface. The investigations reported in this thesis cover various physico-chemical aspects of glass fibre reinforced unsaturated polyester resin sheets and the contents of the thesis are divided into two sections. Section I is mainly concerned with the studies on interfacial beliaviour of glass fibre reinforced polyester laminates. A size material is always applied on the glass fibre to protect it from damage during handling and to improve glass/resin bond in the laminate. The important constituents of a size are film binder and coupling agent. Whereas behaviour of a coupling agent at glass/resin interface has been well studied by many workers, not much attention lias been paid to the behaviour of other constituents of a size such as film binder. Experiments were performed to determine the effect of individual sizing components on processing characteristics of glass fibres and on the properties of the laminate in the present study. Ihe impregnating beliaviour of various fibrous reinforcing materials with respect to their processibility in the filament winding process has been investigated and various methods for the measurement of the impregnating behaviour of fibrous reinforcing materials compared and their relative suitability evaluated. Two types of glass fibre reinforcements namely, A and E types are generally used for producing reinforced plastics in India. Producers many times claim equal performance for the two types of laminates which is misleading. A study was, therefore, conducted to • : v » polyester laminates at various aging conditions. Section II of the thesis deals with the studies on x/eathering behaviour of glass fibre reinforced polyester sheets. In order to develop plastics for buildings with satisfactory resistance to weather, it is necessary to understand weathering elements and their deteriorating effects on plastics. How a plastic sheet is going to weather in our climatic conditions? Ibw the life of these sheets can be improved to bring them at par with the time - tested conventional building materials? These are come of the questions which interfere with the large scale use of these sheets. Weathering behaviour of commercially produced GRP sheets of different brands was evaluated by subjecting them to natural and accele rated weathering. A study has also been made to see the effect of degree of cure of resin on the weathering beliaviour of glass fibre reinforced polyester sheets. Lighting characteristics of these sheets depend upon their compositional details such as- type of resin, type of glass fibre, moulding and curing methods and surface treatments. Investigations wore carried out to study influence of compositional variables and weathering on lighting characteristics of these sheets. Weathering performance of a material evaluated at one place may not show the representative value fbr the whole country. With this in view, natural weathering exposure of these sheets was carried out at : vi i three representative sites viz., Roorkee (relatively tamperate), Jodhpur (desert) and Mandapam (coastal). These sheets were also subjected to accelerated weathering and results of comparative study under accelerated and natural weathering conditions were evaluated.