Failure in extensional flow of entangled polymer melts

缠结聚合物熔体的拉伸流动失败

• 批准号: 0625072
• 负责人: Morton Denn
• 金额: --
• 依托单位: CUNY City College
• 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: 2006-09-01 至 2011-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0625072&HistoricalAwards=false
• 关键词: Failure; extensional; flow; entangled; polymer

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.

项目编号：CTS-0625072 PRINCIPAL调查员：Morton DENNINSTUTION：CUNY City COLLEGEFAILURE in拉伸流动的纠缠聚合物熔体这笔赠款支持了一项使用缠绕聚合物液体的随机模型来研究聚合物熔体在拉伸流动中失效的研究。模拟结果将与失效应变和可恢复应变的实验数据进行比较，目的是在粗粒度分子水平上理解这种现象。PI最近发展了一种剪切流中纠缠链的一致随机管模型。该模型准确地预测了无参数可调的纠缠窄分布线性聚合物的稳态剪切流变性，并用定义时间尺度的单一可调参数预测了瞬时剪切流变性。该随机模型被用来研究缠绕聚合物在被系链覆盖的壁面附近的流动，该模型成功地预测了在实验观察的范围内的壁面滑移速度和滑移长度，其中观察到的滑移随剪切速率的增加而增加是壁面附近缠结密度减小的结果。在这项资助下，随机模型将适用于拉伸流动，以研究高速拉伸流动和纠缠聚合物液体的恢复，并探索高速拉伸对聚合物熔体中纠缠密度的影响和可能的破坏机制。这项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。该研究小组是本杰明·莱维奇物理化学流体力学跨学科研究所和NSF-CREST介观建模与模拟中心的一部分，来自化学、生物医学和机械工程、化学和物理系的教职员工和学生之间有相当大的互动。还将举办定期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学院，学生总数中有85%是少数族裔，工程学院有50%的少数族裔学生，其中包括许多归国的学生，通常有家庭责任。每年招收两名希望进行本科自主研究或暑期研究的本科生进入研究组。PPI将受益于许多已经在运作的项目，以加强科学和工程领域代表性不足的群体的成员的参与，包括为有兴趣攻读博士学位的本科生设立的CUNY管道项目。