Effects of Chemically Treated Eucalyptus Fibers on Mechanical, Thermal and Insulating Properties of Polyurethane Composite Foams.

Sylwia Członka,Anna Strąkowska,Krzysztof Strzelec,Piotr Pospiech

doi:10.3390/ma13071781

Abstract

In this work, rigid polyurethane (PUR) foams were prepared by incorporating 2 wt% of eucalyptus fibers. The eucalyptus fibers were surface-modified by maleic anhydride, alkali, and silane (triphenylsilanol) treatment. The impact of the modified eucalyptus fibers on the mechanical, thermal, and fire performances of polyurethane foams was analyzed. It was observed that the addition of eucalyptus fibers showed improved mechanical and thermal properties and the best properties were shown by silane-treated fibers with a compressive strength of 312 kPa and a flexural strength of 432 kPa. Moreover, the thermal stability values showed the lowest decline for polyurethane foams modified with the silane-treated fibers, due to the better thermal stability of such modified fibers. Furthermore, the flame resistance of polyurethane foams modified with the silane-treated fibers was also the best among the studied composites. A cone calorimetry test showed a decrease in the peak of heat release from 245 to 110 kW∙m−2 by the incorporation of silane-treated fibers. Furthermore, total heat release and total smoke release were also found to decrease remarkably upon the incorporation of silane-treated fibers. The value of limiting oxygen index was increased from 20.2% to 22.1%. Char residue was also found to be increased from 24.4% to 28.3%. It can be concluded that the application of chemically modified eucalyptus fibers has great potential as an additive to incorporate good mechanical, thermal, and fire properties in rigid polyurethane foams.

Highlights

Polyurethanes (PURs) are one of the most versatile materials
The difference between the dynamic viscosity of the modified systems indicates that the chemical modification of eucalyptus fibers disturbs the formation of larger agglomerates and distributes fibers more evenly in polyol mixture, which results in lower viscosity of the modified systems
This study aims to evaluate the influence of maleic anhydride, alkali, and silane treatments on the eucalyptus fibers and their polyurethane foam composites

Summary

Introduction

Polyurethanes (PURs) are one of the most versatile materials. Polyurethane foams are applied across several areas such as building, industrial insulation, construction, automotive, and domestic appliances [1] due to its excellent properties such as low thermal conductivity, good mechanical properties, and water resistance.As a structural material, rigid polyurethane foams should possess a certain strength, toughness, and heat resistance. Polyurethanes (PURs) are one of the most versatile materials. Polyurethane foams are applied across several areas such as building, industrial insulation, construction, automotive, and domestic appliances [1] due to its excellent properties such as low thermal conductivity, good mechanical properties, and water resistance. Rigid polyurethane foams should possess a certain strength, toughness, and heat resistance. Many additives such as nanoparticles or fibers have been used as reinforcement fillers for the production of rigid polyurethane foams [2,3,4,5,6,7,8]. Besides several inorganic fillers, such as nanoclay [9,10], expandable graphite [11,12,13,14], silica [15,16,17,18,19], talc [17,20,21], or polyhedral oligosilsesquioxanes (POSS) [22,23,24,25], the production of composite foams with bio-based fillers from natural recourses has attracted attention due to their environmentally friendly character [26,27,28,29].

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