Spatially-Resolved Polymer Degradation Via Electron Spin Resonance Imaging (ESRI)

通过电子自旋共振成像 (ESRI) 进行空间分辨聚合物降解

• 批准号: 0105622
• 负责人: Shulamith Schlick
• 金额: $ 32.4万
• 依托单位: University of Detroit Mercy
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-07-01 至 2005-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0105622&HistoricalAwards=false
• 关键词: Spatially; Resolved; Polymer; Degradation; Via

This award is directed to the study of polymer degradation due to UV irradiation and thermal treatment in the presence of air and ozone/air mixtures. The proposed studies will be performed on polymers containing hindered amine stabilizers (HAS) as protecting additives. The main method of study is electron spin resonance imaging (ESRI) of nitroxides and other radical intermediates formed in the degradation process. Spatial information will be encoded in the spectroscopy by collecting ESR spectra in the presence of magnetic field gradients. 1D ESRI will provide the spatial distribution of the radical intensity, and 2D spatial-spectral ESRI will allow visualization of the line shapes along the sample depth. The experiments will be performed as a function of treatment time, wavelength of the UV source, and temperature in thermal degradation. Additional information will be obtained by spin probe ESR, UV, FTIR, and differential scanning calorimetry (DSC). Photo- and thermal degradation will be performed on two classes of polymers: 1. Polymers based on styrene, acrylonitrile and butadiene, as homopolymers and in different combinations as copolymers. This group will include the copolymers poly(styrene-co-butadiene), poly(acrylonitrile-co-butadiene) and poly(styrene-co-acrylonitrile), and poly(acrylonitrile-butadiene-styrene) (ABS). 2. Copolymers of polypropylene and ethylene prepared by sequential polymerization. These polymers consist of a semicrystalline polypropylene (PP) matrix and a dispersed amorphous elastomeric component, and have a phase-separated morphology; the study of these systems will benefit from the rich literature available on polypropylene degradation, but will present the challenge and advantage of properties modification by addition of the elastomer phase. The ability to perform nondestructive profiling via ESRI is an important advantage compared to other (destructive) methods now in use for probing the spatial dimension.%%%The proposed research is expected to: identify specific morphological domains where the degradation process is accelerated; map the consumption of the stabilizer within the sample depth on the scale of mm, and within the morphological domains on the scale of micrometers, contribute to the understanding of environmental factors, for instance the effect of irradiation wavelength and ozone; and lead to nondestructive spectral profiling as a method for the detection of early events in polymer degradation and stabilization.

该奖项针对在空气和臭氧/空气混合物存在的情况下，由于紫外线照射和热处理而导致聚合物降解的研究。提出的研究将在含有受阻胺稳定剂（HAS）作为保护添加剂的聚合物上进行。主要的研究方法是利用电子自旋共振成像（ESRI）对氮氧化物和降解过程中形成的其他自由基中间体进行研究。在磁场梯度存在的情况下，通过收集ESR光谱，将空间信息编码到光谱中。一维ESRI将提供自由基强度的空间分布，二维空间光谱ESRI将允许沿样品深度的线形可视化。实验将按照处理时间、紫外源波长和热降解温度的函数进行。其他信息将通过自旋探针ESR， UV， FTIR和差示扫描量热法（DSC）获得。光降解和热降解将在两类聚合物上进行：以苯乙烯、丙烯腈和丁二烯为基的聚合物，均聚物和以不同组合为共聚物的聚合物。这一组将包括共聚物聚（苯乙烯-共丁二烯）、聚（丙烯腈-共丁二烯）和聚（苯乙烯-共丙烯腈）以及聚（丙烯腈-丁二烯-苯乙烯）（ABS）。2. 用顺序聚合法制备的聚丙烯和乙烯共聚物。这些聚合物由半结晶聚丙烯（PP）基体和分散的非晶态弹性体组分组成，并且具有相分离的形态；这些体系的研究将受益于聚丙烯降解方面的丰富文献，但通过添加弹性体相来改性将带来挑战和优势。与目前用于探测空间维度的其他（破坏性）方法相比，通过ESRI进行非破坏性剖面的能力是一个重要的优势。%%%拟议的研究预计将：确定加速降解过程的特定形态域；绘制稳定剂在样品深度内（以毫米为单位）和形态域内（以微米为单位）的消耗图，有助于了解环境因素，例如辐照波长和臭氧的影响；并导致非破坏性光谱分析作为一种方法来检测早期事件的聚合物降解和稳定。