An Effective Expanded Graphite Coating on Polystyrene Bead for Improving Flame Retardancy.

Minjung Bae,Hyunhwa Lee,Jaesik Kang,Gyeongseok Choi

doi:10.3390/ma14216729

Minjung Bae, Hyunhwa Lee + Show 2 more

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https://doi.org/10.3390/ma14216729

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Abstract

Although foamed plastic insulation is widely used in construction in the Korean market, it is vulnerable to fire. To improve the flame retardancy, the method of flame-retardant coating with the EG in water-soluble state on the surface of expanded polystyrene (EPS) beads has been widely used. However, polystyrene beads coated with a water-soluble flame retardant easily separate the coated flame retardant in manufacturing. In this study is devised a flame-retardant coating and two steps of coating process for adhering the flame-retardant coating film evenly to the surface of the polystyrene bead without exfoliation. It was analyzed whether a flame-retardant EPS (FR-EPS) with excellent flame retardancy could be manufactured using polystyrene beads coated in this way. Ten FR-EPS samples satisfied the HF-1 and V-0 levels in horizontal and vertical burning tests, respectively. The THR of eight FR-EPS samples for ten minutes did not exceed 8 MJ∙m−2 and the maximum HRR did not exceed 200 kW∙m−2 for more than ten consecutive seconds. FR-EPS passed the building material standard of semi-nonflammability in Korean regulations, in contrast to commercial EPS, which have not passed the semi-nonflammability standard. It was also analyzed how effective the designed coating is in this study, comparing it with composites that were planned to improve the flame resistance of polystyrene, as reported in the literature. Flame Retardancy Index (FRI) values of FR-EPS proved the “excellent” level and had higher values compared with other polystyrene composites. These results demonstrated that the coated EPS containing a water-soluble flame retardant manufactured from EG and two steps of application with the coating solution achieved fire safety standard regulations.

Highlights

The Korean government has begun to implement policies to strengthen the flame retardancy of building insulation
The external insulation system should satisfy the regulation [2] for thermal performance on each part of the building and include a fire prevention structure defined by the regulation or consist of building materials certified for the performance of being semi-nonflammable
PUR, phenolic foam (PF), and PIR samples did not pass the minimum level of flame-retardant materials indicated in the regulation because their Total Heat Release rate (THR) exceeded 8 MJ·m−2 before 4 min

Summary

Introduction

The Korean government has begun to implement policies to strengthen the flame retardancy of building insulation. Korean regulations [1] provide test methods and standards for classifying building finishes, including insulation, as nonflammable, semi-nonflammable, and flame-retardant materials. The external insulation system should satisfy the regulation [2] for thermal performance on each part of the building and include a fire prevention structure defined by the regulation or consist of building materials certified for the performance of being semi-nonflammable. The reinforced policy calls for building insulation products that secure fire safety and thermal performance at the same time. Especially expanded polystyrene (EPS), are widely used as insulation materials for buildings in Korea due to their inexpensive price, sufficient thermal performance, and easy construction. When exposed to fire, it ignites and emits a large amount of heat and smoke as it burns, making it relatively vulnerable to fire [3,4,5]

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