A comparison of the effect of different flame retardants on the compressive strength and fire behaviour of rigid polyurethane foams.(Report)

INTRODUCTION

Rigid polyurethane foams are considered the materials of choice for many applications because of their excellent heat insulating and good physical and mechanical properties (1). They have wide range of applications both as insulating and structured materials (2,3) and final application in refrigeration technology, transportation, building and construction, automotive industry, packaging and sporting goods (4,5). The word wide demand for these foams has been estimated to be about 5% of the total world consumption of plastics (6).

However, the rigid polyurethane foams are particularly flammable due to their high surface area and more attention has been paid to improve the flame retardant properties of PU foams through numerous studies (1,7-8).

The main approach reaching such a target is to incorporate flame retardant materials into the foams. Many flame retardant materials and methods of their application have been used to improve fire retardancy of polyurethane foams (9-12). The most widely used flame retardants are halogen (13,14), phosphorous (13,15-16) and nitrogen (17-20) compounds, although use of halogenated additives may be restricted because of corrosive, obscuring and toxic smoke release and environmental protection which is a key factor in all stages (7-8).

Although the effect of different kind of flame retardant on fire behavior of rigid polyurethane foams have been studied and reported individually (12), but comparison between these different kinds of materials on fire retardancy have not been reported.

The aim of the present study is to investigate and compare the influence of different flame retardant materials on fire behavior of rigid polyurethane foams. For this purposes the amount and structure of ammonium poly phosphate, borax, aluminum trihydrate, melamine cyanurate and expanded graphite on some properties of the foams, mainly on their resistance to combustion are studied and reported.

EXPERIMENTAL

Materials

The isocyanate used in this study was a polymeric aromatic isocyanate based on diphenylmethane 4,4'-diisocyanate with NCO%=24.3, from Bayer, Germany.

Polyol with OH No=350mgKOH/g according to ASTMD4274-05was obtained from Bayer, Germany. The polyol was premixed with catalyst, blowing agent and surface active agent before use.

Ammonium poly phosphate (APP), Borax (Bo), melamine cyanurate (M), Aluminium trihydrate (ATH) and expanded graphite (EG) were obtained from local market in Iran.

Foam Preparation

The filler containing polyurethane foam samples was prepared by hand mixing technique by using a mechanical stirrer with variable speed. The chemical compositions of the studied formulation are given in Table 1.

The flame retardants materials were first well …