Constraints in Semicrystalline Polymers During the Transition from the Liquid to the Solid State

半晶聚合物从液态到固态转变过程中的限制

• 批准号: 0602473
• 负责人: Peggy Cebe
• 金额: $ 32.7万
• 依托单位: Tufts University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-06-01 至 2013-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0602473&HistoricalAwards=false
• 关键词: Constraints; Semicrystalline; Polymers; During; Transition

TECHNICAL SUMMARY:The confining effect of crystals, during the transformation from liquid to semicrystalline solid of semicrystalline polymers, will be investigated in this research program. The research will answer the following specific questions about structure and relaxation dynamics vis--vis confinement. 1. Does the length, xCRR, of cooperatively rearranging regions, CRRs, at the glass transition correlate with the development of the solid fraction, the crystal fraction, or both? 2. Do the alpha relaxation (glass transition) dynamics vary in a manner correlated with the development of these same fractions? and, 3. What is the structure of the resultant nanophases during solidification? The answers to these questions will provide a fundamental level of understanding about the relationship between the crystals and the non-crystalline portions of the semicrystalline polymer, as confinement occurs during the transition from the liquid to the solid state. A major, and novel, aspect of this research will be the use of quasi-isothermal measurements of the reversing heat capacity to study the time development of formation of the crystal constraints. The time development of the solid fraction, and the crystalline fraction, respectively, will be assessed from the earliest stages of crystallization, through spherulite impingement, and finally to completion of the crystallization process. The alpha relaxation (glass transition process) will be studied using dielectric relaxation spectroscopy, and lamellar structure will be determined using small angle X-ray scattering and atomic force microscopy. NON-TECHNICAL SUMMARY:Plastics are ubiquitous materials in everyday life. The majority of commercially useful plastics are processed using heat and pressure to form them into desired shapes. An important class of plastics comprises those that also have the ability to crystallize during processing. The crystals have very complicated shapes, and tend to form in clusters. But in a very simplified picture, the crystals act like miniature staples, holding the plastic together on the nanometer length scale, and preventing the constituent molecules from shifting around. To improve the ultimate properties of the plastics, it is important to: understand when and how the staples form; characterize the actual crystal shape, size, and organization; and determine how crystals restrict the motion of the other molecules. This research will lead to new products and processing strategies for plastics, improving our global competitiveness. The program also serves to educate the next generation of scientists, with a special focus and outreach to students who are deaf or hard of hearing.

技术概要：本研究计划将研究半结晶聚合物从液体到半结晶固体转变过程中晶体的限制效应。 这项研究将回答以下关于结构和弛豫动力学维斯约束的具体问题。 1.在玻璃化转变时，协同重排区域的长度xCRR是否与固体部分、晶体部分或两者的发展相关？ 2.α弛豫（玻璃化转变）动力学变化的方式与这些相同的馏分的发展？ 和3.固化过程中所得纳米相的结构是什么？ 这些问题的答案将提供一个基本水平的理解之间的关系的晶体和半结晶聚合物的非结晶部分，作为约束发生在从液体到固体状态的转变。 一个主要的，新颖的，本研究的一个方面将是使用准等温测量的反向热容量来研究形成的晶体约束的时间发展。 将分别从结晶的最早阶段、通过球晶撞击和最终完成结晶过程评估固体部分和结晶部分的时间发展。 将使用介电弛豫光谱研究α弛豫（玻璃化转变过程），并使用小角X射线散射和原子力显微镜确定层状结构。 非技术总结：塑料是日常生活中无处不在的材料。 大多数商业上有用的塑料都是通过加热和加压来加工成所需形状的。 一类重要的塑料包括那些在加工过程中也具有结晶能力的塑料。 晶体具有非常复杂的形状，并且倾向于形成簇。 但在一个非常简化的图片中，晶体就像微型斯台普斯一样，将塑料在纳米长度尺度上固定在一起，并防止组成分子四处移动。 为了提高塑料的最终性能，重要的是：了解斯台普斯何时以及如何形成;表征实际晶体形状，大小和组织;并确定晶体如何限制其他分子的运动。 这项研究将带来新的塑料产品和加工策略，提高我们的全球竞争力。 该计划还有助于教育下一代科学家，特别关注和推广聋人或听力困难的学生。