膨胀型多元醇阻燃硬质聚氨酯泡沫性能及机理研究

Rigid polyurethane foam (RPUF) as an excellent insulating and structural material is widely used in many fields, however, it is also known for its high flammability. Even though the traditional flame-retardants can improve the fire resistance, damage for the mechanical property of RPUF has been an unresolved problem until now. To enhance the flame-retardance and simultaneously maintain the mechanical performance of RPUF is an important aspect. In the light of the above issues, in this project, polyols containing both intumescent parts and polyhydroxy with nitrogen element structures are designed and synthesized as intumescent flame retardant. Based on the chemical nature of polyhydric alcohol group which can participate in the molding reaction of polyurethane form through chain-extension or cross-linking reaction, reactive intumescent flame-retardant molecular structure is introduced to polyurethane foam to actualize inherent flame retardant RPUF. The RPUF material with both good flame-retardance and mechanical property is successfully fabricated through dual functions of flame-retardant and cross-linking which come from intumescent flame-retardant part and polyhydroxy part, respectively. A series of intumescent polyols with different cyclic organic phosphate structure and hydroxyl functionality are designed and synthesized. The flame-retardance, thermal behaviors, mechanical properties and toxic gases releasing of RPUF modified by polyols flame retardants with different structures are systematically investigated. The decomposition behaviors of flame retardant foams in condensed and gaseous phase during pyrolysis at higher temperature are investigated. Micro-morphology, strength, chemical constitution and graphite structures of the char-layers after combustion are also analyzed. Based on the results, reasonable flame-retardant mechanisms can be proposed. Due to the studies of mechanisms, compound and synergistic methods can be used to remedy the mechanism defects of relevant system while enhancing the flame-retardant efficiency. This work will provide a novel insight for designing and preparing of the polyurethane materials with reactive intumescent flame-retardant system.

硬质聚氨酯泡沫（RPUF）作为优良的保温和结构材料被广泛应用，但极为易燃，提升阻燃效用并保持力学性能是目前RPUF阻燃研究的重要方向。本项目设计合成兼具含磷膨胀单元与含氮多羟基结构的膨胀型多元醇阻燃剂，利用多元醇可以通过交联/扩链方式参与硬质聚氨酯泡沫成型的化学属性，将膨胀阻燃结构引入聚氨酯分子链，实现本质阻燃。在膨胀阻燃结构与多元醇阻燃-扩链/交联的双重作用下，获得阻燃与力学性能俱佳的泡沫材料。改变膨胀阻燃结构与羟基官能度探索膨胀型多元醇结构对RPUF阻燃性能、热性能、力学性能及烟气毒性释放等影响规律。深入研究阻燃材料高温热解时气/固双相分解行为及燃烧炭层形貌、强度、化学组成、石墨化结构等，综合分析并提出合理科学的阻燃机理。根据研究结果设计复合、协效等方式弥补相关阻燃体系中的机理缺陷，优化阻燃体系，提高阻燃效率。本课题的研究将为聚氨酯相关材料反应型膨胀阻燃体系的设计和建立提供一种思路。

硬质聚氨酯泡沫（RPUF）作为优良的保温和结构材料被广泛使用，但非常易燃，存在极大的火灾安全隐患。本项目基于醇羟基可以参与RPUF发泡反应的基本原理，设计合成含磷膨胀单元与含氮多羟基结构的膨胀型多元醇用于RPUF的本质阻燃研究。在项目执行期间，研究内容如下：（1）四种新型磷氮膨胀型多元醇的合成与表征；（2）膨胀型多元醇阻燃RPUF研究；（3）膨胀型多元醇复合可膨胀石墨阻燃RPUF研究。同时，本项目还将膨胀型多元醇应用于棉织物阻燃，进行了系统研究。研究结果表明，项目所合成的四种新型磷氮膨胀型多元醇（DEPA、DPDA、DPPT、PDDT）具有较好的热稳定性、高成炭性和热膨胀效应。随着多元醇阻燃剂添加量的增大，RPUF材料极限氧指数（LOI）从19.0%逐步提高到24.0%附近，通过水平燃烧测试。进一步，采用可膨胀石墨与多元醇阻燃剂复合协同阻燃RPUF时，材料LOI值达到30%以上，在锥形量热测试中大幅降低了材料最大热释放速率（PHRR）及烟气释放。气固双相阻燃机理探索表明复合阻燃体系在凝聚相中促进形成富磷蠕虫状石墨保护性炭层，在气相中大大抑制了可燃性气体产生。多元醇应用于阻燃棉织物表现出优异的阻燃效果，同时具有明显的结构依赖性。四种多元醇阻燃对棉织物阻燃效率的顺序为：DEPA<DPDA<DPPT<PDDT，后三种阻燃剂能将棉织物LOI从19.0%提高到29.3~31.6%，垂直燃烧测试离火自熄。阻燃多元醇的使用有效降低棉织物PHRR值，大幅提高燃烧残炭。气固双相阻燃机理测试分析表明凝聚相中大量含磷成分促进保护性炭层形成，有效保护棉织物基体不被破坏。同时，磷酸化作用使气相中可燃性成分如CO、醚类及含羰基物质的释放得到有效抑制。本项目研究成果对新型阻燃多元醇设计合成及其应用具有重要的指导和借鉴意义。