Thermal degradation of Poly(methyl methacrylate) with a 1.064 μm Nd:YAG laser in a buoyant flow
Thermal degradation of Poly(methyl methacrylate) with a 1.064 μm Nd:YAG laser in a buoyant flow
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DOI：
10.1016/j.polymdegradstab.2015.06.016
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发表时间：
2015-11
影响因子：
5.9
通讯作者：
R. I. Acosta;K. Gross;G. Perram
中科院分区：
文献类型：
--
作者：
R. I. Acosta;K. Gross;G. Perram
利用成像傅里叶变换红外光谱（IFTS）研究了聚甲基丙烯酸甲酯（PMMA）的激光辐射氧化分解过程及其气相分解产物。利用足够的空间分辨率（每像素0.81 mm 2）和光谱分辨率（2 cm-1）研究了空气中气体羽流的空间和时间演变。用连续1.064 μ mNd：YAG激光器以4 ~ 22 W/cm 2的功率密度辐照黑色PMMA样品表面。甲基丙烯酸甲酯（MMA）的强光谱发射在红外观察。羽流温度和MMA柱密度的空间地图，通过假设一个均匀的单羽流辐射传输模型（RTM）从模拟观测到的光谱。光谱模型被用来计算气体发射率从实验测量，内插和外推MMA吸收系数数据库。此外，从照射PMMA表面的光谱辐射与普朗克分布拟合，得到时间和空间的表面温度分布。峰值信噪比超过50：1，使得羽流温度和MMA柱密度测定具有低统计误差。在22 W/cm ~ 2的激光辐照下，PMMA的稳定表面温度为613.9 ± 0.8 K，峰值气相温度为700 ± 19 K。所有结果报告的统计不确定性定义为95%置信区间的半宽，不包括与均匀羽流假设或湍流效应相关的系统误差。随着激光强度的增加，气体温度降低的表面边界层。为了了解CO2和Nd：YAG激光器的波长依赖性表面加热速率，开发了一种简化的热分析。MMA形成在表面上的一个单一的像素的阿克里尼乌斯图进行了比较与建立的动力学模型。在450-600 K的表面温度下，得到的有效活化能为30.83 ± 8.29 kJ/mol，与单体的表面脱附一致。
The laser radiative oxidative decomposition of poly(methyl methacrylate) (PMMA) and the evolved decomposition products in the gas-phase are investigated using imaging Fourier transform infrared spectroscopy (IFTS). The spatial and temporal evolution of the gas plume in air was investigated with adequate spatial (0.81 mm2per pixel) and spectral resolutions (2 cm−1). Surfaces of black PMMA samples were irradiated from 4 to 22 W/cm2with a cw 1.064 μm Nd:YAG laser. Strong spectral emission of methyl methacrylate (MMA) was observed in the infrared. Spatial maps of plume temperature and MMA column density were obtained from modeling the observed spectra by assuming a homogeneous single-plume radiative transfer model (RTM). A spectral model was used to compute the gas emissivity from an experimentally measured, interpolated and extrapolated MMA absorption coefficient database. In addition, the spectral radiance from the irradiated PMMA surface was fitted with Planck's distribution to obtain temporal and spatial surface temperature profiles. The peak signal-to-noise exceeded 50:1, allowing plume temperature and MMA column density determinations with low statistical errors. Laser irradiated PMMA reached a steady surface temperature of 613.9 ± 0.8 K and a peak gas-phase temperature of 700 ± 19 K at 22 W/cm2. The reported statistical uncertainties for all the results are defined as the half-width of the 95% confidence interval and do not include systematic errors associated with the assumption of a homogeneous plume or the effects of turbulence. As laser intensity increased, gas temperature decreased at the surface-boundary layer. A simplified thermal analysis was developed to understand the wavelength dependent surface heating rates from using both CO2and Nd:YAG lasers. An Arrhenius plot of MMA formation at the surface for a single pixel was compared with established kinetics models. At surface temperatures of 450–600 K, an effective activation energy of 30.83 ± 8.29 kJ/mol was obtained, consistent with surface desorption of the monomer.