新型硬质聚氨酯泡沫的热分解行为及动力学

利用热重分析法比较研究了新型硬质聚氨酯泡沫[超支化聚氨酯多元醇型(HBPU型)]和硬质聚氨酯泡沫(RPUF)在氮气中的热分解行为,探讨了HBPU型RPUF在不同升温速率下的热分解动力学,运用Kissinger最大失重率法和Flynn-Wall-Ozawa等失重百分率法计算获得了其热分解过程的活化能。研究结果表明,HBPU型RPUF的初始分解温度(T5%)为205℃,半寿温度(T50%)为361℃,略低于传统的RPUF。Kissinger法得到的HBPU型RPUF的热分解表观活化能为159.8 kJ/mol;Flynn-Wall-Ozawa法得到的热分解过程分为三个阶段:第一阶段的平均活化能为82.8 kJ/mol,第二阶段的平均活化能为140.7 kJ/mol,第三阶段的平均活化能为111.3 kJ/mol,HBPU型RPUF具有较好的热稳定性。     

三聚氰胺甲醛树脂泡沫制备的研究

以三聚氰胺和甲醛为原料制得三聚氰胺甲醛树脂(MF),将其与辛基苯酚聚氧乙烯(10)(OP-10)、正戊烷、甲酸混合均匀后制备MF泡沫.结果表明,MF的黏度随反应时间增加而提高;MF泡沫的表观密度首先随着甲酸用量的增加而减小,然后再增加;MF泡沫有良好的阻燃性和热稳定性.     

氰酸酯复合泡沫的机械性能与耐热性能研究

以氰酸酯树脂和中空玻璃微球为原料制备了复合泡沫。通过检测复合泡沫的剪切强度、平面拉伸强度以及压缩强度评价复合泡沫的机械性能。结果表明,复合泡沫的机械性能由玻璃微球的性质以及在复合泡沫中的含量决定。微球的密度越大,泡沫的机械性能越高,反之亦然。泡沫的力学性能与微球的含量几乎呈线性降低的关系。通过TG分析表明,复合泡沫的热性能主要由氰酸酯本身性质决定,起始分解温度为400℃,但在高温阶段,微球的存在加速了复合泡沫的分解速率。在180℃下经过30d热老化试验,复合泡沫的热失重不明显,但固化物的外观颜色加深。     

三聚氰胺甲醛树脂研究与应用进展

三聚氰胺甲醛树脂是一种具有良好的绝缘性、抗腐蚀性和良好的机械性能的高分子材料.文章中主要介绍了三聚氰胺甲醛树脂的近几年的研究与应用进展情况.包括：利用新的引入特征元素或基团的合成方法制备出性能优异或具有某种特色功能的新型三聚氰胺甲醛树脂;三聚氰胺甲醛树脂在泡沫以及在光学材料的研究进展.最后对三聚氰胺甲醛树脂的发展方向和应用前景提出了一些展望.     

三聚氰胺甲醛树脂泡沫生产工艺及技术改进

三聚氰胺甲醛树脂泡沫是一种以三聚氰胺为原料制取的高开孔率的三维网格结构的新型环保泡沫塑料,具有吸音、阻燃等众多优异性能。本文介绍了三聚氰胺甲醛树脂泡沫的理化性能、国内外技术发展情况、以及实验室和工业制备方法。最后针对三聚氰胺甲醛树脂泡沫连续化生产的要求,改进了生产工艺流程和反应器。     

树脂包覆法阻燃EPS泡沫塑料的制备及其燃烧性能的表征

探索了制备可发性聚苯乙烯(EPS)的工艺流程和参数,研究了三聚氰胺甲醛树脂(MF)预聚体包覆聚磷酸铵(APP)以及硼酸锌(ZB)对EPS泡沫的阻燃性能的影响,分别使用极限氧指数测试和热失重分析对其燃烧性能和热稳定性进行了表征。结果表明,包覆阻燃可以明显提高EPS泡沫塑料的阻燃性能,极限氧指数由18.0%提高到22.6%,残炭量提高了85.0%,遇火收缩的现象得到显著改善,燃烧速度可减小51.7%。加入ZB可以进一步提高成炭量和炭层的强度,从而进一步提高阻燃性能。     

三聚氰胺甲醛树脂泡沫塑料碳化研究

以三聚氰胺甲醛树脂泡沫塑料为前驱体进行碳化研究。通过实验可以看出,三聚氰胺甲醛树脂泡沫材料密度和压陷硬度随温度的升高先有所上升后逐渐降低,体积收缩比较明显,但仍具有一定的弹性;采用扫描电子显微镜观察到随着温度的升高,泡沫塑料泡孔逐渐萎缩、骨架变细更容易断裂;利用同步热分析仪记录了泡沫塑料碳化过程质量损失情况,在400~800℃三聚氰胺甲醛树脂泡沫碳化速率最快;借助全自动元素分析仪分析了三聚氰胺甲醛树脂泡沫材料各元素相对含量的变化趋势,在20~700℃之间,泡沫中N元素相对含量先增加后降低,C元素相对含量在300℃后显著增加。     

三聚氰胺甲醛树脂包覆不同目数红磷的稳定化研究

采用原位聚合方法制备了三聚氰胺甲醛树脂包覆不同目数的红磷。对包覆红磷进行了扫描电镜、X射线光电子能谱(XPS)、吸水性、抗氧化性、pH值及热重分析测试。扫描电镜和XPS结果表明,三聚氰胺甲醛树脂在红磷表面形成了有效包覆。吸水率结果表明,三聚氰胺甲醛树脂包覆后的红磷,其吸水率随着时间增长显著降低,7 d后的吸水率低于0.6%;抗氧化测试表明,其抗氧化能力比未包覆红磷提高27倍以上;热失重结果表明,包覆后起始氧化增重温度提高70℃以上。1000目包覆红磷的稳定性比1500目更优。     

三聚氰胺甲醛的微波发泡工艺研究

以三聚氰胺和多聚甲醛为原料合成了三聚氰胺甲醛树脂,并利用微波加热发泡工艺进行发泡。在树脂的合成过程中,探究了原料配比、反应温度以及反应时间对树脂性能的影响,确定了合成三聚氰胺甲醛树脂的适宜工艺条件。在树脂的发泡过程中,研究了树脂黏度、固含量、发泡功率及时间对泡沫体性能的影响,制得性能良好的泡沫保温材料,并对泡沫体的一些性能指标进行了测试。     

复合垃圾衍生燃料燃烧-热解特性的研究

采用热重和气-质联用仪对复合垃圾衍生燃料(CRDF)的燃烧特性和氯释放特性进行分析,结果表明在燃烧和热解条件下,CRDF中氯的释放特性有明显的区别,在温度为500～600℃时CRDF燃烧无机氯的释放率可达90%以上,而CRDF热解无机氯的释放为76%;当温度达800℃时CRDF热解过程释放的有机氯化合物种类和浓度均高于燃烧过程。热重分析结果显示CRDF在热处理中存在3个明显的失重阶段,第一失重阶段温度约200～300℃,失重率38.5%;第二失重阶段温度约为400～500℃,失重率为20.35%,第三阶段为一个缓慢的失重阶段,温度在600～800℃,失重率约22.35%。     

Thermogravimetric and qualitative analysis of thermal decomposition characteristics of polyurethane foams based on polyols with carbamide or oxamide and borate groups

The thermal stability and the kinds of products of thermal decomposition of polyurethane foams modified with urea or oxamide and borate groups were studied. Incorporation of urea or oxamide groups and borate groups enhances the thermal stability of polyurethane foams compared to polyurethane foams based on typical polyols. Thermal stability of foams modified with oxamide groups is somewhat higher that of foams modified with urea groups. In turn, simultaneous incorporation of borate groups results in an increase in thermal stability of the foams modified with urea. The temperature of thermal decomposition of the foams with oxamide and borate groups does not change or undergoes a slight decrease. The thermal degradation products of investigated foams are similar and they are usually water, ammonia, carbon dioxide and/or nitrous oxide. Additionally, hydrogen cyanide can be released during thermal decomposition of polyurethane foams modified with urea groups. The presence of borate groups prevents the formation of hydrogen cyanide. The opposite situation is observed in the case of the foams modified with oxamide and borate groups. Thus, from the point of view of a fire hazard, the use of the foams modified with urea and borate groups is safer. © 2017 Society of Chemical Industry     

Mechanical properties and thermal stability of rice husk ash filled epoxy foams

Mechanical properties and thermal stability of epoxy foams filled with white and black rice husk ash were studied. Epoxy foams were prepared from a commercial system and filled with different amounts of both the ashes (0, 6.8, 12.8, 18.0, and 22.7 wt %). The incorporation of both the ashes modified the final morphology of the foam, decreasing the average cell size and increasing the number of cells per volume unit. For all filler percentages used, the specific modulus and strength results showed that the white ash is more effective as reinforcing agent than the black ash. The initial degradation temperature was not affected by the content and type of ash used as the filler. The integral procedure decomposition temperature, weight loss, and char residue results were related to the ash type and atmosphere used in the thermogravimetric analysis. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Nitrogen-containing products from the thermal decomposition of flexible polyurethane foams

The thermal decomposition of a polyester and a polyether flexible foam in a nitrogen atmosphere has been studied by gas chromatography, mass spec-trometry and elemental ultramicroanalysis. It is shown that the decomposition behaviours of the two foams are similar. At low temperatures (200 to 300 °C) there is a rapid and complete loss of the tolylene diisocyanate unit of each foam as a volatile yellow smoke leaving a polyol residue. The smoke has been isolated as a yellow solid (common to both foams) which contains virtually all of the nitrogen of the original foams and, under the conditions of test, is stable at temperatures up to 750 °C. Nitrogen-containing products of low molecular weight (mainly hydrogen cyanide, acetonitrile, acrylonitrile, pyridine and benzonitrile) observed during the high temperature decomposition (over 800 °C) of the foams are shown to be derived from the yellow smokes. At 1000 °C, approximately 70% of the available nitrogen has been recovered as hydrogen cyanide.     

Toxic products from the combustion and pyrolysis of polyurethane foams

Products from the thermal decomposition of four polyurethane foams heated to temperatures in the range 220 to 400 °C, in atmospheres of nitrogen, of 6% oxygen in nitrogen and of air were examined for some of the anticipated toxic materials. When phosphorus-containing inhibitors were added to or chemically incorporated in the foams, phosphorus compounds were evolved under most of the conditions employed. Other materials detected were hydrogen cyanide, isocyanate, urea, halogenated compounds and alkenes. A brief discussion is given of the hazard presented by polyurethane foams decomposing under these conditions.     

Reinforcement of soy polyol‐based rigid polyurethane foams by cellulose microfibers and nanoclays

Water‐blown rigid polyurethane foams from soy‐based polyol were prepared and their structure–property correlations investigated. Cellulose microfibers and nanoclays were added to the formulations to investigate their effect on morphology, mechanical, and thermal properties of polyurethane foams. Physical properties of foams, including density and compressive strength, were determined. The cellular morphologies of foams were analyzed by SEM and X‐ray micro‐CT and revealed that incorporation of microfibers and nanoclays into foam altered the cellular structure of the foams. Average cell size decreased, cell size distribution narrowed and number fractions of small cells increased with the incorporation of microfibers and nanoclays into the foam, thereby altering the foam mechanical properties. The morphology and properties of nanoclay reinforced polyurethane foams were also found to be dependent on the functional groups of the organic modifiers. Results showed that the compressive strengths of rigid foams were increased by addition of cellulose microfibers or nanoclays into the foams. Thermogravimetric analysis (TGA) was used to characterize the thermal decomposition properties of the foams. The thermal decomposition behavior of all soy‐based polyurethane foams was a three‐step process and while the addition of cellulose microfibers delayed the onset of degradation, incorporation of nanoclays seemed to have no significant influence on the thermal degradation properties of the foams as compared to the foams without reinforcements. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of tetraacid on the properties of ODPA/4,4′‒ODA polyimide foams

In this research, a new flexible polyimide (PI) foams was successfully prepared and characterized based on precursor powder foaming. This foams were derived from 3,3',4,4'‒oxydiphethalic anhydride (ODPA), 3,3',4,4'‒oxydiphethalic tetraacid (ODPA‒tetraacid), and 4,4'‒oxydianiline (4,4'‒ODA). With varying molar percentage of ODPA‒tetraacid in (ODPA + ODPA‒tetraacid), the changes of properties of PI precursor powders and PI foams were comparatively investigated. The foaming processes of PI foams were observed by a self‒made visualization device. The decomposition products of precursor powders were analyzed by thermogravimetry‒Fourier transform infrared spectroscopy (TG‒FTIR). The crystallinity of precursor powders was investigated by wide‒angle X‒ray diffraction (WXRD). The chemical structure of PI precursor powders and foams was analyzed by FTIR. The thermal properties of PI foams were tested by the methods of dynamic mechanical analysis (DMA), and TG/differential thermogravimetry (DTG) analysis. The cell structure of PI foams was observed by a scanning electron microscopy. The rebound resilience of PI foams was studied by a self‒made drop‒ball instrument. With the increasing of ODPA‒tetraacid, the inflation onset temperatures and inflation degrees of PI foams decreased from 210°C to 118°C and increased from 10 to 14.8 times, respectively. The crystallinity of PI precursor powders increased. The thermal stability of PI foams decreased. The cell structure of PI foams became more uniform and the rebound rates increased linearly. Besides, ODPA‒tetraacid did not yield any negative effect on the complete imidization of the PI precursor powder by the FTIR spectra. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Mechanical and thermal properties of modified red mud‐reinforced phenolic foams

A new type of composite based on phenolic foams reinforced with red mud microparticles was prepared using a thermal foaming method. Red mud was ground into ultrafine particles with grain diameters ranging from 1 to 1.5 μm. Silane coupling agent γ‐ureidopropyltriethoxysilane was used to modify the red mud microparticles to improve particle dispersion and adhesion between the particles and the phenolic matrix. The effects of the modified red mud microparticles on the mechanical and thermal properties of the composite were investigated at weight ratios ranging from 0 to 21%. The phenolic foams incorporating 15 wt% of the filler exhibited the best integrated performance. In comparison with native phenolic foams, tensile strength and impact strength were increased by 81.8 and 82.3%, respectively. Furthermore, the addition of modified red mud microparticles to the phenolic foam significantly decreased its thermal conductivity while increasing its limiting oxygen index. A morphological analysis using scanning electron microscopy indicated that incorporation of the modified red mud microparticles into the foam produced relatively small and uniformly sized cells within the material, which indicated that the observed improvements in mechanical and thermal properties were primarily due to the chemical adhesion between the particles and the matrix and good dispersion of particles in the matrix. The reinforced foams described in this study can be used in a variety of applications in the field of heat insulation. © 2018 Society of Chemical Industry     

Vermiculite Filler Modified with Casein,Chitosan, and Potato Protein as a Flame Retardant for Polyurethane Foams

In this study, polyurethane (PU) composite foams were modified with 2 wt.% of vermiculite fillers, which were themselves modified with casein, chitosan, and potato protein. The impact of the fillers on selected properties of the obtained composites, including their rheological (foaming behavior, dynamic viscosity), thermal (temperature of thermal decomposition stages), flame-retardant (e.g., limiting oxygen index, ignition time, heat peak release), and mechanical properties (toughness, compressive strength (parallel and perpendicular), flexural strength) were investigated. Among all the modified polyurethane composites, the greatest improvement was noticed in the PU foams filled with vermiculite modified with casein and chitosan. For example, after the addition of modified vermiculite fillers, the foams’ compressive strength was enhanced by ~6–18%, their flexural strength by ~2–10%, and their toughness by ~1–5%. Most importantly, the polyurethane composites filled with vermiculite filler and modified vermiculite fillers exhibited improved flame resistance characteristics (the value of total smoke release was reduced by ~34%, the value of peak heat release was reduced by ~25%).     

Influence of structure of hydroxyl-terminated maleopimaric acid ester on thermal stability of rigid polyurethane foams

A series of hydroxyl-terminated maleopimaric acid esters (HTMAEs) and rigid polyurethane (PU) foams based on these HTMAEs were synthesized using chemically modified natural gum rosin and its derivative maleopimaric acid as raw materials. Thermal stability of these polyols and their corresponding rigid PU foams was studied by a thermogravimetric method and a dimensional stability measurement. It was shown that the thermal stability of the final foams was strongly dependent on the structure of their corresponding polyols. The thermogravimetric analysis curves of these rosin-based rigid PU foams displayed two distinct regions of weight loss. It has been shown that at the initial stage of weight loss the process was dominated by polyol component degradation; the second stage was governed by isocyanate component degradation. © 1995 John Wiley & Sons, Inc.