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首页> 外文学位 >Characterization of polyisocyanurate foams: The effect of blowing agents and exposure conditions on physical, chemical, and microstructural properties.
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Characterization of polyisocyanurate foams: The effect of blowing agents and exposure conditions on physical, chemical, and microstructural properties.

机译：聚异氰脲酸酯泡沫的特征：发泡剂和暴露条件对物理，化学和微观结构性质的影响。

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The effects of blowing agents and exposure conditions on the physical, chemical, and microstructural properties were determined for rigid, polyisocyanurate (PIR) foams. At the onset of this project, the two most promising alternatives to CFC-11 as a blowing agent were HCFC-141b and HCFC-123. Since that time, HCFC-123 has been removed from the market and the advent of coblowing has arrived. The thermal properties of foams produced using these new materials and methods have been investigated extensively, but the role of the alternative blowing agents on the mechanical properties of the foams has not been studied. Additionally, the changes which occur in the foams as they age are not well understood. Therefore, this project had the following objectives, to characterize the independent or associated roles that blowing agent and aging have in determining mechanical properties of PIR foams.; The foams tested had three different blowing agents combined in various fashions to produce six formulations.; The foams were exposed to three environments, a field exposure on a roof at Oak Ridge National Laboratory for 16 months, 75{dollar}spcirc{dollar}C/10%RH for 1, 5, and 25 weeks, or 60{dollar}spcirc{dollar}C/75%RH for 1, 5, and 25 weeks.; The microstructural results for the foams were consistent regardless of blowing agent or exposure condition. The cell size increased for the foams with increased exposure while the cell wall thickness declined.; The chemical analysis of the foams again showed no differences between the blowing agents. Each of the test methods, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and Fourier transform infrared (FTIR) spectroscopy, showed a decrease in blowing agent, a decrease in unreacted isocyanate (NCO), or an increase in polyurethane or polyisocyanurate components.; The physical properties (including mechanical) were determined for the foams using a number of methods. Again, no difference could be discerned in the behavior of the foam based on the blowing agent used. The density of the foams decreased with increasing exposure. This was in agreement with the increase in the cell size and decrease in cell wall thickness observed earlier. The ultrasonic moduli, Young's and shear, increased with exposure as did the compressive modulus. This result was the opposite of the expected behavior since mechanical properties in foams are believed to vary in the same fashion as the density. The explanation offered is that the crosslinking which occurred led to a higher modulus which more than compensated for the decrease in density.
机译：确定了硬质聚异氰脲酸酯（PIR）泡沫的发泡剂和暴露条件对物理，化学和微观结构性质的影响。在该项目开始时，作为发泡剂的CFC-11的两个最有希望的替代品是HCFC-141b和HCFC-123。自那时以来，HCFC-123已从市场上撤出，并且共花式的到来已经到来。已经广泛研究了使用这些新材料和方法生产的泡沫的热性能，但尚未研究替代发泡剂对泡沫机械性能的作用。另外，人们还不太了解泡沫随着年龄的增长而发生的变化。因此，该项目具有以下目标，以表征发泡剂和老化在确定PIR泡沫的机械性能方面的独立或相关作用。所测试的泡沫具有三种不同的发泡剂，它们以各种方式结合在一起以产生六种配方。将泡沫暴露于三种环境中，在橡树岭国家实验室的屋顶上暴露16个月，在75 {sp} {circ} C / 10％RH的条件下暴露1、5和25周，或60 {dol}溅水{美元} C / 75％RH，持续1、5和25周。不管发泡剂或暴露条件如何，泡沫的微观结构结果都是一致的。泡沫的泡孔尺寸随着暴露增加而增加，而泡孔壁厚度下降。泡沫的化学分析再次表明发泡剂之间没有差异。每种测试方法，差示扫描量热法（DSC），热重分析（TGA）和傅立叶变换红外（FTIR）光谱法均显示发泡剂减少，未反应的异氰酸酯（NCO）减少或聚氨酯或聚异氰脲酸酯组分。使用多种方法确定了泡沫的物理性能（包括机械性能）。同样，基于所使用的发泡剂，在泡沫的行为上没有区别。泡沫的密度随着暴露的增加而降低。这与早期观察到的细胞大小增加和细胞壁厚度减少一致。超声模量，杨氏模量和剪切力随着暴露而增加，压缩模量也随之增加。该结果与预期的行为相反，因为人们认为泡沫的机械性能以与密度相同的方式变化。所提供的解释是发生的交联导致较高的模量，大于补偿了密度的降低。

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