The Effects of Some Phosphorus-Containing Fire Retardants on the Properties of Glass Fibre-Reinforced Composite Laminates Made from Blends of Unsaturated Polyester and Phenolic Resins

Latha Krishnan,Baljinder K Kandola,John R Ebdon

doi:10.3390/jcs5100258

Abstract

This study investigated the effects of phosphorus fire retardants (FRs) in matrices from co-cured blends of an unsaturated polyester (UP) with inherently fire-retardant phenolic resoles (PH) on the mechanical and flammability properties of resultant glass fibre-reinforced composites. Three different phenolic resoles with UP have been used: (i) an ethanol soluble (PH-S), (ii) an epoxy-functionalised (PH-Ep), and (iii) an allyl-functionalised resin (PH-Al) with two different phosphorus FRs: resorcinol bis (diphenyl phosphate) (RDP) and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO). The flammabilities of the resultant composites were evaluated using cone calorimetry and the UL-94 test. Cone calorimetric results showed reductions in peak heat release rate (PHRR) and total heat released (THR) as expected compared to those of UP and respective UP/PH composite laminates without FRs. UL-94 tests results showed that while all composites had HB rating, FR containing samples self-extinguished after removal of the flame. The mechanical properties of the composites were evaluated using flexural, tensile and impact tests. All FRs reduced the mechanical properties, and the reduction in mechanical properties was more severe in UP/PH-S (least compatible blends) composites with FRs than in UP/PH-Al (most compatible blends) composites with FRs. Amongst the different composites, those from UP/PH-Al with DOPO showed the best fire retardancy with little deterioration of mechanical performance.

Highlights

Unsaturated polyester (UP) based glass fibre-reinforced composite (GFRC) is one of the widely used composites in marine applications owing to its excellent mechanical properties, good moisture resistance, and good corrosion and chemical resistance [1,2,3,4,5]
The heat release rate (HRR) vs. time curves and rate of smoke release (RSR) vs. time curves for GFRC laminate systems of UP, UP/phenolic resoles (PH)-S, UP/PH-Ep and UP/PH-Al with and without fire retardants (FRs) are shown in Figure 1a–c, respectively
This work has shown that the fire retardancy of GFRC of UP/PH-S, UP/PH-Ep and with UP/PH-Al can be further improved by the addition of Resorcinol bis(diphenyl phosphate) (RDP) or DOPO

Summary

Introduction

Unsaturated polyester (UP) based glass fibre-reinforced composite (GFRC) is one of the widely used composites in marine applications owing to its excellent mechanical properties, good moisture resistance, and good corrosion and chemical resistance [1,2,3,4,5]. The intrinsic flammability of UP can be altered either by chemical modification of the resin or by adding fire retardant chemicals into it [8,9]. Each method has drawbacks associated with it such as the following: the chemical modification of UP usually involves using halogenated elements, which raises environmental issues [10]; high concentrations (typically >30 wt.%) of mineral fillers such as aluminium trihydrate and magnesium hydroxide or inorganic phosphates cause deleterious effects upon physical and mechanical properties and processing difficulties [11,12]. An alternative approach is to use protective surface coatings of ceramic or intumescent materials, but these cause additional weight [13,14,15]

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Conclusion