酚醛泡沫的燃烧行为及阻燃研究进展

酚醛泡沫因兼具优异的保温性能和阻燃性能在工程领域得到广泛应用,但其经高温燃烧后质量残留率很低,炭层疏松、强度低,离开火焰后还易出现阴燃现象。目前有关酚醛泡沫燃烧行为的研究大多集中在如何进一步提高酚醛泡沫塑料的阻燃等级或在改善其脆性的同时不降低固有的阻燃性能,还未见关于酚醛泡沫燃烧全过程行为的综述报道。文章介绍了酚醛泡沫在明火燃烧和阴燃状态的燃烧行为,分析了影响酚醛泡沫燃烧行为的因素,并总结了现有酚醛泡沫阻燃研究的进展。目前酚醛泡沫的燃烧行为及阻燃研究主要集中在泡沫的明火燃烧,对酚醛泡沫阴燃问题的研究重视不足,缺乏针对酚醛泡沫燃烧全过程的行为和机理探究。因此,提出应加大对酚醛泡沫阴燃行为的研究投入,注重对酚醛泡沫燃烧全过程的机理探索与阻燃方案研究,设计并研发出解决酚醛泡沫燃烧全过程问题的有效途径。     

原竹纤维增强酚醛泡沫材料的燃烧特性

采用锥形量热仪研究了不同原竹纤维加入量对酚醛泡沫材料的燃烧性能和烟气释放特性的影响。结果表明,酚醛泡沫材料的引燃时间随着原竹纤维加入量的增大而缩短,热释放速率、总放热量、质量损失速率、生烟速率和总发烟量随原竹纤维加入量的增大而总体呈增大趋势,但由于酚醛泡沫材料具有良好的阻燃性能,其燃烧快速成炭特性阻碍了热量在材料内层传递,减缓了原竹纤维在0~480 s燃烧阶段的热释放和烟气释放,使得加入量为1.5 %~3.5 %的原竹纤维作为其增强材料时,对酚醛泡沫材料的阻燃性能影响较小;而原竹纤维的加入量≥5.0 %时,对酚醛泡沫材料的阻燃性能有较大的降低作用,必须进行阻燃改性。     

轻质阻燃酚醛泡沫材料的制备与构效关系研究（摘要）

针对可发性酚醛树脂及酚醛泡沫存在的问题,本文作者采用新型不脱水工艺,直接合成了固含量在70％～85％的可发性高固含甲阶酚醛树脂。分析了甲醛／苯酚（F／P）物质的量之比和催化剂种类对树脂性能的影响;讨论了酚醛泡沫制备工艺,建立了酚醛泡沫表观密度一力学性能模型;采用木质纤维表面处理方法制备纤维复合酚醛泡沫;采用无卤阻燃系统制备阻燃改性的酚醛泡沫;采用酸化处理方法制备无机复合酚醛泡沫。主要研究内容和结论如下：     

聚氨酯泡沫阻燃技术的研究进展

概述了聚氨酯泡沫的燃烧过程及其燃烧的3个阶段,分析了聚氨酯泡沫燃烧的化学反应机理和阻燃剂的阻燃机理,阐述了卤系阻燃剂、磷系阻燃剂、氮系阻燃剂、硼系阻燃剂、填充型阻燃剂和可膨胀型阻燃剂的特点并比较其实际应用情况。综述了近几年国内外学者在聚氨酯阻燃技术上的研究进展,并对聚氨酯泡沫的阻燃研究和发展趋势作出了展望,指出一方面可对无机添加型阻燃剂进行结构改性,提高微胶囊化和表面改性后的阻燃剂微粒的产率,进一步改善阻燃剂微粒在泡沫中的分布;另一方面研究阻燃剂复配后的协效作用机理。     

阻燃丁苯橡胶燃烧特性的主要影响因素

研究阻燃丁苯橡胶(SBR)配方中氯化石蜡/三氧化二锑并用比、炭黑和白炭黑对其燃烧特性和阴燃性能的影响。结果表明:氯化石蜡/三氧化二锑并用比为1∶1时,阻燃SBR的阻燃性能最好;与未添加炭黑的阻燃SBR相比,添加炭黑的阻燃SBR的阻燃性能提高,但阴燃现象严重;与未添加白炭黑的阻燃SBR相比,添加白炭黑的阻燃SBR的阻燃性能提高,且未产生阴燃现象。     

玻纤增强酚醛泡沫的制备及性能研究

为了研究玻璃纤维长度及含量对酚醛泡沫性能的影响,分别将微米级玻纤粉、3mm短切玻纤和6mm短切玻纤按照一定比例添加到酚醛泡沫体系中,利用Instron万能材料试验机,分别测试玻纤增强酚醛泡沫的压缩、拉伸强度,并利用扫描电镜观察酚醛泡沫的微观形貌。结果表明,添加了12%的3mm短切玻纤增强酚醛泡沫压缩性能最好,其压缩强度比纯酚醛泡沫增加了38%;添加了8%的6mm短切玻纤增强酚醛泡沫拉伸性能最好,其拉伸强度比纯酚醛泡沫增加47%;添加了12%的3mm短切玻纤增强酚醛泡沫的阻燃性能最好,其极限氧指数为44.1。     

Nomex纸蜂窝增强酚醛泡沫的制备及性能研究

本文以自制酚醛树脂发泡制备的酚醛泡沫为基体,Nomex纸蜂窝为增强体,采用特定的发泡制备工艺制得了Nomex纸蜂窝增强酚醛泡沫.通过对该材料微观形貌、力学性能和热性能的表征,初步探讨了材料基体和界面效应对其力学性能和隔热性能的影响.研究结果发现,填充了酚醛泡沫后,Nomex纸蜂窝增强酚醛泡沫的力学性能显著提高,导热系数显著降低.分析认为,良好的强结合界面保障了酚醛泡沫对Nomex纸蜂窝增强酚醛泡沫力学性能和隔热性能的贡献,该材料是一种综合性能较好的隔热、阻燃材料.     

酚醛泡沫的发展现状及应用

酚醛泡沫是一种新兴的保温绝热材料,被称为第三代新兴保温材料,是目前泡沫保温材料中发展最快的品种,被称为＂保温之王＂。由于其轻质、隔热、阻燃等优点而具有十分广阔的应用前景。本文论述了酚醛泡沫的发展概况,介绍了酚醛泡沫的制备,性能和应用。     

阻燃泡沫聚乙烯的研究和发展

本文论述了泡沫聚乙烯的燃烧机理及阻燃机理，并介绍了泡沫聚乙烯的阻燃方法及研究发展动态。     

PFF与PUF热稳定性及燃烧性能研究

制备了酚醛泡沫和聚氨酯泡沫，并研究了酚醛硬泡与聚氨酯硬泡的热稳定性及燃烧性能。结果表明：和聚氨酯泡沫比较，酚醛泡沫的热失重小，热释放速率和热释放总量低。因此酚醛泡沫的热稳定性和阻燃性能明显优于聚氨酯泡沫。     

Studying smoldering to flaming transition in polyurethane furniture subassemblies: Effects of fabrics,flame retardants,and material type

The transition from smoldering to flaming was studied on fabric, batting, and foam assemblies via an electric spot ignition source of similar intensity to a cigarette. The materials studied included four different fabrics (cotton, polyester, cotton/polyester blend, flame retardant cotton/polyester blend), two types of batting (cotton, polyester), and three types of polyurethane foam (nonflame retardant, flame retardant by FMVSS 302 testing, flame retardant by BS5852 testing). The results from testing found that materials highly prone to smoldering could propagate smoldering into foams and lead to ignition, whereas materials that tended to melt back from the ignition source did not. Flame retardant fabrics or foam can and do prevent the transition from smoldering to flaming provided sufficient levels of flame retardants are incorporated in the upholstery fabric or foam. The transition from smoldering to flaming of cotton fabric/nonflame retardant foam assembly was also studied using temperature measurements and evolved gas analysis. It was determined that the transition takes place when the oxygen consumption by accelerating smoldering front exceeds the oxygen supply. At this point, the solid fuel gasification becomes driven by thermal decomposition rather than by surface oxidation which leads to high enough concentrations of fuel for flaming combustion to occur.     

Grafting modification bamboo kraft lignin and its performance in rigid polyurethane foams

In order to improve the efficiency of intumescent flame retardant (IFR), bamboo kraft lignin (BKL) was chemically functionalized by grafting melamine (MEL) and diethyl phosphite (DEP) and used for rigid polyurethane (RPU) foam. The BKL, MEL, and DEP in IFR system were used as char forming agent, gas, and acid source, respectively. The FTIR and XPS results indicated that the nitrogen (N) and phosphorus (P) containing BKL was successfully synthesized. The limiting oxygen index (LOI) value of N-BKL and N/P-BKL RPU foams were higher than BKL RPU foam, suggesting that N-BKL and N/P-BKL improved flame retardancy of the foams. The total heat release (THR), heat release rate (HRR), effective heat of combustion (EHC), and fire growth rate (FIGRA) values of N-BKL and N/P-BKL RPU foams were much lower than that of BKL RPU foam. The flame retardancy index value of N/P-BKL RPU foams was higher comparing to N-BKL RPU foam. These results indicated that the synergistic interaction between N containing compound of MEL and P containing compound of DEP led to the improvement flame retardant properties. Comparing to BKL RPU foam, the N/P-BKL RPU foam increased 74°C of maximum weight loss temperature and decreased 18.1 wt% of mass loss, indicating enhanced thermal stability. The morphology of char after cone calorimeter testing showed the N/P-BKL RPU foam presented more continuous and compact char residues, which could reduce heat and mass transfer, protecting underlying materials from further combustion in a fire, thus resulting in good flame retardancy and thermal stability properties. This work suggests a promising route to enhancing the flame-retardant performance of RPU foam using nontoxic and more environmentally friendly grafted bamboo lignin.     

Relationship between the thermal degradation chemistry and flammability of commercial flexible polyurethane foams

In this article, we report the use of a variety of analytical methods, in particular, solid‐state ¹H‐NMR and ¹³C‐NMR to characterize the relationship between the condensed‐phase chemistry and burning behavior as determined by a series of combustion tests for two commercially derived flexible polyurethane foams, one combustion‐modified. The combustion tests showed that the foams met several regulatory requirements in terms of their fire performance, whether or not they were combustion‐modified. Both foams passed the MV SS 302 and CAL 117 small‐flame tests. The nonmodified foam failed the Crib 5 test, but this test had a much larger ignition source. The particular problem with the nonmodified foam was melt drip into the flame zone. This led to a steady maintenance of the fuel feed and a rapid escalation of the fire. In contrast, the combustion‐modified foam showed little melt drip and self‐extinguished. Thermal analysis data for the two foams showed that melamine acted in part as an endothermic heat sink. This alone did not account for the much reduced melt flow and drip of the combustion‐modified foam, but the solid‐state ¹H‐NMR data clearly showed that the molecular mobility of the combustion char from combustion‐modified foam was lower than the unmodified foam char, which indicated that the flame‐retardant formulation in the combustion‐modified foam acted by a condensed‐phase mechanism. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3024–3033, 2006     

Flame retardation and thermal stability of novel phosphoramide/expandable graphite in rigid polyurethane foam

A novel flame retardant named diethylene N,N',N''‐tri (diethoxy)phosphoramide (DTP) was synthesized using diethyl phosphate and diethylenetriamine via Atherton–Todd reaction. Then, series of flame‐retardant water‐blown rigid polyurethane foams (RPUFs) with expandable graphite (EG) and DTP were prepared through box‐foaming. The results of thermogravimetric analysis showed that DTP/EG changed thermal degradation process of RPUF and promoted enhancing char residues. The complex flame‐retardant system (EG/DTP) endowed RPUF higher limiting oxygen index (LOI) values (29.1%–30.2%) and lower heat release rate peak (PHRR) values according to LOI and microscale combustion calorimeter tests. More importantly, the synergistic flame‐retardant effect between EG and DTP in RPUF was proved by the analysis of synergistic effectivity values. Based on the analysis of cone calorimetric tests, EG/DTP revealed remarkable effects to inhibit the fire intensity and smoke release of RPUF with decreased PHRR and total smoke production due to good char‐forming action. To further investigate the char‐residues of the foams after combustion, scanning electron microscope and energy dispersive X‐ray spectroscopy analyses were conducted. The results suggested that EG/DTP flame‐retardant system promoted RPUF forming a compact, continuous and phosphorus‐rich char layer as a good fire barrier in combustion. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46434.     

A void surface flame retardant strategy for polymeric polyHIPEs

Effective flame retardant strategy for open-cell foam (e.g., polyHIPE) remains of a great challenge. Herein, a void surface flame retardant strategy for polyHIPE was presented. An open-cell polystyrene (PS) polyHIPE was fabricated through an emulsion-templating technique. Polyphosphazene (PSZ), a highly efficient flame retardant polymer, was then in situ fabricated and covalently attached to the void surface of the foam to be a uniform flame retardant protective layer, while the open-cell structure of the foam was perfectly preserved. Compared with the pristine PS polyHIPE, the PSZ modified one had significantly improved thermal stability (char residues yield at 800°C increased from 3.36 to 16.53 wt%) and mechanical properties (Young's modulus increased by 2.6 times); the values of average heat release rate and total heat release of combustion were reduced by 62.36% and 41.57%, respectively. While, the value of limiting oxygen index was increased from 17.39% to 19.75%, owing to the combined action of condensed phase flame retardant and gas phase flame retardant. These results indicate that the in situ surface modification strategy is effective for improving the flame retardancy of highly interconnected polymer foams.     

Apparatus for investigating the burning and dripping of vertically oriented polyurethane foams

The burning and dripping behaviour of polyurethane (PU) foam is crucial for upholstered furniture fires due to the melting and dripping behaviour of the foam that results in a pool fire under the furniture, which enhances the combustion. The sample feeding vertical cone is developed to investigate the two-dimensional small-scale burning and dripping behaviour of vertically oriented PU foams where a constant irradiance is maintained at the exposed surface by means of automatic sample compensation. Seven different PU foams were investigated and classified as conventional foam or char-forming foam according to the observed surface phenomena during exposure to heat fluxes. The burning and dripping behaviour is found to depend on the foam density as well as the solid-phase char formation by the presence of fire retardant additives. The total mass loss rate and the dripping rate increase with higher foam density and with the presence of char formation. In contrary, the vaporisation rate is favoured at lower foam density and with the absence of char formation. Flexible foams of low density without the ability to form char tend to achieve low dripping rate where majority of the mass loss is via vaporisation, contributing directly to the gas-phase combustion.     

线型酚醛与微胶囊红磷阻燃ABS的研究

采用线型酚醛(Novolac)与微胶囊红磷(MRP)复配阻燃,制备了无卤阻燃丙烯腈-丁二烯-苯乙烯(ABS)复合材料。研究了Novolac/MRP质量比和用量对阻燃ABS性能的影响。研究结果表明:Novolac/MRP的质量比为3/2,总量为15%(质量分数)时,可以制备极限氧指数(LOI)为26.7%,垂直燃烧(UL94)V-0级的无卤阻燃ABS;Novolac的酚羟基与MRP燃烧产生的聚磷酸在高温下发生的脱水成炭反应减缓了ABS的分解;SEM炭层形貌分析表明:Novolac/MRP复合阻燃ABS材料燃烧表面形成了平整、致密的炭层,该炭层能够有效地隔绝燃烧过程所产生的易燃气体及热量,起到较好的阻燃效果。     

Flame‐retardant mechanism of expandable polystyrene foam with a macromolecular nitrogen–phosphorus intumescent flame retardant

Expandable polystyrene (EPS) foam is largely used as the thermally insulating external wall in buildings and constructions, but it is extremely flammable because of the presence of almost 98% air into its porous structure, its high surface‐area‐to‐mass ratio, and its elemental composition. Lots of serious fire disasters caused by EPS foam have posed great threats to people's properties and lives in recent years. Thus, a halogen‐free, flame‐retardant EPS is urgently needed, and its preparation is still a global challenge. To solve the problem that it is easy for EPS foam to form melt dripping and difficult for it to generate a char layer during the combustion process, a macromolecular nitrogen–phosphorus intumescent flame retardant (MNP) was selected to prepare flame‐retardant EPS foam and good mechanical and flame‐retardant properties were obtained. The scanning electron microscopy characterization revealed that MNP could penetrate into the gap between the beads, and a thin physical coating layer formed on the surface of the bead. The data from the thermogravimetry–Fourier transform infrared test indicated that a nitrogenous noncombustible gas was generated by the pyrolysis of MNP. When the MNP content increased to 30%, the limiting oxygen index and the smoking density rate of the EPS–MNP foam were 28.8 and 23.6, respectively, and a UL94 V‐0 classification was achieved. In addition, the heat‐release rate, total heat‐release, smoke produce rate, and carbon dioxide production of the EPS–MNP foams all decreased obviously; this was attributed to the flame‐retardant effects of MNP in both the condensed and gas phases. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44356.     

Lightweight,Elastomeric, and Flame‐Retardant Foams from Expanded Chlorinated Polymers

Intrinsically flame‐retardant polymers based on lightweight and elastomeric microcellular foams are successfully prepared from flexible chlorinated polyethylene (CPE)/chlorinated polyvinylchloride (CPVC) compounds through compression molding foaming technology. The incorporation of CPVC to CPE at once improves the foam characteristics, and enhances the mechanical and fire performances. Due to the plausible intermolecular and intramolecular crosslinking among the polymer chains, the dense network structure of CPE/CPVC with enhanced strength results in increased cell size, reduced cell density, and improved dimensional stability of CPE/CPVC foams (CCFs). These improvements are noticed to be enhanced with increasing CPVC content in the CCF. Also, the flame‐retardant properties of the foams (i.e., limiting oxygen index and cone calorimeter combustion) are found to be increased with the increase of CPVC content. For instance, a highly flame‐retardant CCF at CPE/CPVC ratio of 60/40 shows a shorter combustion period, as derived from the respective heat release rate vs time curve. Corresponding peaks of heat release rate, total heat release rate, peak of mass loss rate, total smoke release, and char residue are recorded to be 8.4%, 5.8%, 3.0%, 6.6%, and 1000.1% of those recorded for the pristine CPE foam.