A Study of Structure-Process-Property Relationships in BlownPolymeric Films

吹塑聚合物薄膜结构-工艺-性能关系的研究

• 批准号: 9713372
• 负责人: Junuthula Reddy
• 金额: $ 40万
• 依托单位: Texas A&M Engineering Experiment Station
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-10-01 至 2000-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9713372&HistoricalAwards=false
• 关键词: Study; Structure; Process; Property; Relationships

This research has the long term objective of establishing the structure-process-property relationships in both high density polyethylene (HDPE) and low density polyethylene (LDPE) blown films. Crystallization kinetics and film morphology as a function of both molecular architecture and processing parameters will be investigated using physical models and numerical simulation of the process. The research will include the development of suitable constitutive models for the theology and crystallinity of the polymer being blown. Experiments based on commercial scale film blowing apparatus will be used to evaluate Constitutive models and determine appropriate boundary and initial conditions for the numerical simulation of the film blowing process. A transient, non- axisymmetric, and nonlinear finite element model of the process will be developed. The computational model will also be used to study collapse and instability in a non-axisymmetric setting. The three principal investigators are uniquely qualified, because of their background in theoretical and computational mechanics,polymer structure and mechanical property characterizations, and polymer processing and theology, to successfully carry out the research. A stable film blowing process requires a delicate balance between the excess pressure inside the bubble, the resin extrusion rate, the film wind-up speed, and the cooling rate. These parameters vary considerably from polymer to polymer due to slight differences in melt strength and crystallinity. In practice, the best combinations of process variables required to produce good quality film is achieved through a series of trial-and-error steps that results in large-scale wastage of polymer resin and person hours. Computer simulations of film blowing process offers an attractive alternative for at least three reasons. First, computer simulations can help answer basic questions about how specific process variables influence bubble stability. Second, simulations will help identify which resin Properties are most important in determining performance in film blowing processes. Third, if the constitutive relationship between molecular orientation and polymer crystallinity is properly formulated, the connection between the ultimate film properties and process conditions can be identified. Together-, these three factors should significantly reduce the number of experiments needed to optimize commercial film blowing processes for new polymer resins. The research investigates phenomena that are interdisciplinary in nature. Phase change, crystallization and surface flow phenomena are of interest to various manufacturing processes and scientific problems. The research will be carried with the help of students, who will be trained to develop theoretical formulations, finite element model, and interpretation and correlation of the numerical results, and the students will also be trained to run the film blowing equipment and collect data to assist and correlate numerical simulations. This training of students to think and understand the fundamental, as well practical aspects, is considered as important contribution as the results of the research.

本研究的长期目标是建立高密度聚乙烯（HDPE）和低密度聚乙烯（LDPE）吹膜的结构-工艺-性能关系。结晶动力学和薄膜形态作为分子结构和加工参数的函数将使用物理模型和过程的数值模拟进行研究。这项研究将包括为被吹制的聚合物的神学和结晶度开发合适的本构模型。基于商业规模吹膜装置的实验将用于评估本构模型，并确定吹膜过程数值模拟的适当边界和初始条件。该过程的瞬态、非轴对称和非线性有限元模型将被开发。该计算模型还将用于研究非轴对称环境下的坍塌和不稳定性。由于他们在理论和计算力学、聚合物结构和力学性能表征、聚合物加工和神学方面的背景，三位主要研究人员具有独特的资格，可以成功地开展研究。一个稳定的吹膜过程需要在气泡内的超压、树脂挤出速度、薄膜卷绕速度和冷却速度之间取得微妙的平衡。由于熔体强度和结晶度的细微差别，这些参数因聚合物而异。在实践中，生产高质量薄膜所需的工艺变量的最佳组合是通过一系列的试错步骤来实现的，这导致了聚合物树脂和工时的大规模浪费。吹膜过程的计算机模拟提供了一个有吸引力的替代方案，至少有三个原因。首先，计算机模拟可以帮助回答有关特定过程变量如何影响气泡稳定性的基本问题。其次，模拟将有助于确定哪些树脂特性在决定吹膜过程中的性能方面最重要。第三，如果分子取向和聚合物结晶度之间的本构关系得到适当的表述，则可以确定最终薄膜性能与工艺条件之间的联系。综上所述，这三个因素将显著减少优化新型聚合物树脂的商业吹膜工艺所需的实验次数。这项研究调查了跨学科性质的现象。相变、结晶和表面流动现象是各种制造工艺和科学问题的兴趣所在。该研究将在学生的帮助下进行，他们将被训练建立理论公式，有限元模型，以及数值结果的解释和关联，学生还将被训练操作吹膜设备并收集数据以辅助和关联数值模拟。这种训练学生思考和理解的基础，以及实际的方面，被认为是研究成果的重要贡献。