Title: Tensile Fracture of Welded Polymer Interfaces: Miscibility, Entanglements, and Crazing

Abstract

Large-scale molecular simulations are performed to investigate tensile failure of polymer interfaces as a function of welding time t. Changes in the tensile stress, mode of failure and interfacial fracture energy G_I are correlated to changes in the interfacial entanglements as determined from Primitive Path Analysis. Bulk polymers fail through craze formation, followed by craze breakdown through chain scission. At small t welded interfaces are not strong enough to support craze formation and fail at small strains through chain pullout at the interface. Once chains have formed an average of about one entanglement across the interface, a stable craze is formed throughout the sample. The failure stress of the craze rises with welding time and the mode of craze breakdown changes from chain pullout to chain scission as the interface approaches bulk strength. The interfacial fracture energy G_I is calculated by coupling the simulation results to a continuum fracture mechanics model. As in experiment, G_I increases as t^1/2 before saturating at the average bulk fracture energy G_b. As in previous studies of shear strength, saturation coincides with the recovery of the bulk entanglement density. Before saturation, G_I is proportional to the areal density of interfacial entanglements. Immiscibiltiy limits interdiffusion andmore » thus suppresses entanglements at the interface. Even small degrees of immisciblity reduce interfacial entanglements enough that failure occurs by chain pullout and G_I << G_b.« less

Authors:

Ge, Ting ^[1]; Grest, Gary S. ^[2]; Robbins, Mark O. ^[3]

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+ Show Author Affiliations

1. Johns Hopkins Univ., Baltimore, MD (United States). Department of Physics and Astronomy; Univ. of North Carolina, Chapel Hill, NC (United States). Dept. of Chemistry
2. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
3. Johns Hopkins Univ., Baltimore, MD (United States). Department of Physics and Astronomy

Publication Date:

Fri Sep 26 00:00:00 EDT 2014

Research Org.:

Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1183119

Report Number(s):

SAND-2014-17313J
Journal ID: ISSN 0024-9297; 537227

Grant/Contract Number:  

AC04-94AL85000

Resource Type:

Accepted Manuscript

Journal Name:

Macromolecules

Additional Journal Information:

Journal Volume: 47; Journal Issue: 19; Journal ID: ISSN 0024-9297

Publisher:

American Chemical Society

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE