Failure in extensional flow of entangled polymer melts

摘要提案编号：CTS-0625072主要研究者：MORTON DENNINSTITUTION：CUNY CITY COLLEGEFAILURE IN EXTENSIONAL FLOW OF INTENGGED POLYMER MELTS该基金支持一项研究，重点是使用缠结聚合物液体的随机模型研究聚合物熔体在拉伸流动中的失效。建模结果将进行比较，以了解这种现象在粗粒度的分子水平的目标，在故障和可恢复应变应变的实验数据。PI最近发展了一个剪切流中缠结链的一致随机管模型。该模型准确地预测稳态剪切流变缠结窄分布的线性聚合物没有可调参数，它预测的瞬态剪切流变与一个单一的可调参数，定义的时间尺度。随机模型已被改编为研究流动的缠绕聚合物附近的壁，覆盖着拴系链;该模型成功地预测壁滑移速度和滑移长度在实验观察到的范围内的剪切流，其中所观察到的增加滑移随着剪切速率的增加是一个结果，在附近的壁缠结密度的减少。在此授权下，随机模型将适用于拉伸流动，以研究高速率拉伸流动和回收缠结的聚合物液体，并探讨在高速率上的缠结密度和可能的故障机制在聚合物熔体的延伸的后果。拟议的研究解决了聚合物加工中的一个关键问题，有可能对工业实践产生重大影响。该研究小组是跨学科的本杰明·莱维希物理化学流体力学研究所和NSF-CREST中心介观建模与仿真的一部分，来自化学，生物医学和机械工程，化学和物理系的教师和学生之间有相当大的互动。还将定期举办联合研讨会和新的软材料课程，作为NSF-IGERT软材料多尺度现象计划的一部分。城市学院是一所城市机构，总体上有85%的少数民族学生，工程学院有50%的少数民族学生，其中包括许多回国的学生，他们往往有家庭责任。研究小组每年招收两名本科生，他们希望从事本科生独立研究或暑期研究。PI将受益于校园内已经实施的许多项目，以提高科学和工程领域代表性不足的群体成员的参与，包括为有兴趣攻读博士学位的本科生提供的纽约市立大学管道项目。程序.

ABSTRACTPROPOSAL NO.: CTS-0625072PRINCIPAL INVESTIGATOR: MORTON DENNINSTITUTION: CUNY CITY COLLEGEFAILURE IN EXTENSIONAL FLOW OF ENTANGLED POLYMER MELTS This grant supports a study focused on the failure of polymer melts in extensional flows using a stochastic model for entangled polymer liquids. Modeling results will be compared to experimental data for strain at failure and recoverable strain with the goal of understanding this phenomenon at a coarse-grained molecular level. The PI has recently developed a consistent stochastic tube model of entangled chains in shear flow. The model accurately predicts the steady shear rheology of entangled narrow-distribution linear polymers without adjustable parameters, and it predicts the transient shear rheology with a single adjustable parameter that defines the time scale. The stochastic model has been adapted to study flow of an entangled polymer near a wall that is covered with tethered chains; the model successfully predicts wall slip velocities and slip lengths in shear flow within the range observed experimentally, where the observed increase in slip with increasing shear rate is a consequence of a decrease in the entanglement density near the wall. Under this grant the stochastic model will be adapted to extensional flows in order to study high-rate extensional flow and recovery of entangled polymeric liquids, and to explore the consequences of extension at high rates on the entanglement density and possible failure mechanisms in polymer melts. The proposed research addresses a critical problem in polymer processing, with the potential to have a major impact on industrial practice. The research group is a part of the interdisciplinary Benjamin Levich Institute for Physico-Chemical Hydrodynamics and the NSF-CREST Center for Mesoscopic Modeling and Simulation, and there is considerable interaction among the faculty and students, from the Departments of Chemical, Biomedical, and Mechanical Engineering, Chemistry, and Physics. There will also be regular joint seminars and new soft materials courses developed as part of an NSF-IGERT program on Multiscale Phenomena in Soft Materials. City College is an urban institution with an 85% minority student body overall and a 50% minority student body in the School of Engineering that includes many returning students, often with family responsibilities. Two undergraduates, who wish to pursue undergraduate independent research or summer research, will be recruited into research group annually. The PI will benefit from the presence on the campus of many programs already in operation to enhance the participation of members of groups underrepresented in science and engineering, including the CUNY Pipeline Program for undergraduates interested in pursuing a Ph.D. program.