减少石油开采刺激了使用生物可用来源生产多元醇的尝试,这是获得聚氨酯泡沫的基本成分。植物是用之不竭的油脂来源,糖,糖淀粉,和纤维素。获得多元醇的类似底物是壳聚糖。市售改性壳聚糖可溶于水,这使它们有可能与羟烷基化剂反应。我们先前使用水溶性壳聚糖来获得适用于生产硬质聚氨酯泡沫的多元醇。这里,我们描述了低分子量壳聚糖(低聚壳聚糖)与缩水甘油和碳酸亚乙酯的羟烷基化以获得多元醇。通过红外光谱对多元醇进行了详细的分离和研究,1H-NMR,和MALDI-ToF方法。他们的财产,比如密度,粘度,表面张力,和羟基数,决心。比较了水溶性壳聚糖和壳聚糖低聚物与缩水甘油的羟烷基化反应的进展,以表征该过程的反应性和机理。我们发现,壳聚糖与甘油中缩水甘油的羟烷基化导致形成多功能产物,该产物适合进一步转化为具有良好性能的聚氨酯泡沫。壳聚糖与缩水甘油的直接羟烷基化伴随着缩水甘油的低聚。在碳酸亚乙酯存在下,壳聚糖与缩水甘油的羟烷基化伴随着壳聚糖与碳酸亚乙酯的少量羟烷基化。选择的多元醇用于获得硬质聚氨酯泡沫,其特征在于物理参数,如表观密度,吸水,尺寸稳定性,热导率,抗压强度,和在150和175°C下的耐热性。比较了从壳聚糖低聚物和水溶性壳聚糖来源获得的聚氨酯泡沫的性能。由在甘油存在下合成的多元醇获得的聚氨酯泡沫具有有利的性质,例如低热导率,增强的热阻,尺寸稳定性,低吸水率,和高抗压强度,在热暴露后显著增长。
Decreasing oil extraction stimulates attempts to use biologically available sources to produce polyols, which are the basic components for obtaining polyurethane foams. Plants are inexhaustible source of oils, sugars, starches, and cellulose. Similar substrates to obtain polyols are chitosans. Commercially available modified chitosans are soluble in water, which gives them the possibility to react with hydroxyalkylating agents. We used a water-soluble chitosan previously to obtain polyols suitable for producing rigid polyurethane foams. Here, we described hydroxyalkylation of a low-molecular-weight chitosan (oligomeric chitosan) with glycidol and ethylene carbonate to obtain polyols. The polyols were isolated and studied in detail by IR, 1H-NMR, and MALDI-ToF methods. Their properties, such as density, viscosity, surface tension, and hydroxyl numbers, were determined. The progress of the hydroxyalkylation reaction of water-soluble chitosan and chitosan oligomer with glycidol was compared in order to characterize the reactivity and mechanism of the process. We found that the hydroxyalkylation of chitosan with glycidol in glycerol resulted in the formation of a multifunctional product suitable for further conversion to polyurethane foams with favorable properties. The straightforward hydroxyalkylation of chitosan with glycidol was accompanied by the oligomerization of glycidol. The hydroxyalkylation of chitosan with glycidol in the presence of ethylene carbonate was accompanied by minor hydroxyalkylation of chitosan with ethylene carbonate. The chosen polyols were used to obtain rigid polyurethane foams which were characterized by physical parameters such as apparent density, water uptake, dimension stability, heat conductance, compressive strength, and heat resistance at 150 and 175 °C. The properties of polyurethane foams obtained from chitosan-oligomer and water-soluble-chitosan sources were compared. Polyurethane foams obtained from polyols synthesized in the presence of glycerol had advantageous properties such as low thermal conductivity, enhanced thermal resistance, dimensional stability, low water uptake, and high compressive strength, growing remarkably upon thermal exposure.