Preparation and characterization of rigid polyurethane foam prepared from sugar-cane bagasse polyol

https://doi.org/10.1016/j.matchemphys.2011.04.008Get rights and content

Abstract

Rigid polyurethane foam (PUF) was prepared by the reaction of bio-polyol prepared from liquefied sugar-cane bagasse (LBP) with commercial methylene diphenyl diisocyanate (MDI) and polyethylene glycol in the presence of N,N-dimethylcyclohexylamine as a catalyst, water as a chemical blowing agent, and silicon oil as a surfactant. The effect of partial replacement of polyethylene glycol polyol (PEG) by the prepared bio polyol on physical, mechanical, thermal conductivity, and thermal stability of polyurethane foam was studied. The obtained results revealed that, the prepared polyurethane foam showed longer cream and tack free times more than blank polyurethane foam (100% PEG). The foam density and compressive strength improved with increasing of biomass-based polyol content. Increasing the percents of bio polyol more than 30% replacement resulted in heterogeneous surface and irregular pore shape. Also thermal conductivity reduced from 0.035 to 0.029 with increasing bio polyol content. Polyurethane foam additives such as blowing agent, catalyst, and surfactant content effects on polyurethane foam properties were studied.

Highlights

Polyurethane foam prepared from liquefied sugar-cane bagasse as a polyol. ► The compressive strength has been improved using this novel renewable polyol. ► Thermal conductivities of these foam samples have been improved.

Introduction

Polyurethanes (PUs) are versatile engineering materials which find a wide range of applications because of their properties can be readily tailored by the type and composition of their components [1], [2], [3]. Rigid polyurethane (PU) foam is an available material with the lowest thermal conductivity among foamed polymers used commercially [4]. It has been widely utilized in the appliance and construction industry because of its excellent and unique combination of thermal insulation and mechanical properties. PU foams perform well in the most areas of low-temperature insulations. Products with density ranging from approximately 30–200 kg m−3 with stand temperatures down to −196 °C [5]. PU foam is usually synthesized by the reaction of diisocyanate with polyol. In general, blowing agent, catalyst and surfactant are also employed to regulate the properties and morphology of the cell structures. Biomass resource such as agricultural residues are renewable natural polymers and easily obtainable. In recent years, effective utilization of biomass resources has paid growing attention right from the starting to seek a substitute for petroleum and environmental protection [6]. This is not only in concern of the future shortage of petroleum supplies, but also due to a common sense of ecological protection. Liquefaction techniques can convert the solid lignocellulosic biomass into liquid products which contain some –OH groups and have potential values of substituting the polyester or polyether polyol to prepare PU foams [7], which can be friendly to the environment [8]. The reaction type of these liquid products with diisocyanate is poly addition polymerization (structure 1) [9].

Many studies utilizing the natural materials such as starch, soybean oil and cellulose to prepare or modify the properties and degradability of polyurethane have been carried out [10], [11], [12], [13], [14], [15], [16]. Foams that made at least partially from biomass can be created using cellulose from wood fibers once the cellulose is converted into a fluid form. Polyurethane foams can be made from polyol containing as much as 50% biomass by combined dissolution of wood and starch. Maldas et al. [17] studied liquefaction of wood in the presence of polyol using NaOH as a catalyst and its application to polyurethane foams. Liquefaction of waste paper (WP) was conducted in the presence of polyhydric alcohols to prepare biodegradable polyurethane foam [18]. In this study, rigid polyurethane foam was manufactured from isocyanate and polyol of liquefied sugar-cane bagasse which prepared as described elsewhere [19]. The optimal preparation conditions and characteristics of the prepared foamed polyurethane were investigated.

Section snippets

Materials

Liquefied sugar-cane bagasse polyol of hydroxyl number 234.92 mg/KOH and acid number 22.17 mg/KOH has been prepared and characterized in the previous study [Nassar et al. 2010]. Commercial methylene diphenyl diisocyanate (Dow Chemical Company, USA), Polyethylene glycol is a laboratory grade; N,N-dicyclohexaylamine catalyst (Dow Chemical Company, USA), silicon surfactant, and distilled water as blowing agent were used.

Preparation of foam

The rigid polyurethane foam samples with various densities were synthesized with

FTIR spectrum

Fig. 1 illustrates the typical FTIR spectrum of polyurethane foam prepared from mixture of bio-polyol with commercial polyol and methylene diphenyl diisocyanate. FT-IR spectrum verified the existing of the polymer structure. The wide absorption band at 3339 cm−1 represents stretching vibration of N–H urethane hydrogen bonded. The bands at 1530 cm−1, 1220 cm−1, and 1213 cm−1 can be attributed to the δ (N–H), υ (C–N), and υ C–O which confirm that urethane linkages were formed between hydroxyl groups

Conclusion

Liquefied sugar-cane bagasse polyol is suitable for preparing rigid polyurethane foam. The partial replacement of polyethylene glycol polyol by liquefied sugar-cane bagasse polyol had significant effect on physical, mechanical, and thermal properties of polyurethane foam. Increasing liquefied bio polyol shifted the cream and tack free times to longer side. Density of polyurethane foam increased with increasing bio polyol content while compressive strength decreased when the bio polyol was more

References (29)

  • A. Gandini

    Polymers from renewable resources: a challenge for the future of macromolecular materials

    Macromolecules

    (2008)
  • V.T. Breslin

    Degradation of starch–plastic composites in a municipal solid waste landfill

    J. Environ. Polym. Degrad.

    (1993)
  • M.H. Alma et al.

    New polyurethane-type rigid foams from liquefied wood powders

    J. Mater. Sci. Lett.

    (2003)
  • L. Vojtova et al.

    Dedgradace a Recyklace Polyurethanovych Pen

    (2004)
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