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Title: Dependence of nanomechanical modification of polymers on plasma-induced cross-linking

Abstract

The nanomechanical properties of low-density polyethylene (LDPE) modified by inductively coupled, radio-frequency Ar plasma were investigated by surface force microscopy. The polymer surface was modified under plasma conditions of different ion energy fluences and radiation intensities obtained by varying the sample distance from the plasma power source. Nanoindentation results of the surface stiffness versus maximum penetration depth did not reveal discernible differences between untreated and plasma-treated LDPE, presumably due to the small thickness of the modified surface layer that resulted in a substrate effect. On the contrary, nanoscratching experiments demonstrated a significant increase in the surface shear resistance of plasma-modified LDPE due to chain cross-linking. These experiments revealed an enhancement of cross-linking with increasing ion energy fluence and radiation intensity, and a tip size effect on the friction force and dominant friction mechanisms (adhesion, plowing, and microcutting). In addition, LDPE samples with a LiF crystal shield were exposed to identical plasma conditions to determine the role of vacuum ultraviolet (VUV) and ultraviolet (UV) radiation in the cross-linking process. The cross-linked layer of plasma-treated LDPE exhibited much higher shear strength than that of VUV/UV-treated LDPE. Plasma-induced surface modification of the nanomechanical properties of LDPE is interpreted in the context of molecularmore » models of the untreated and cross-linked polymer surfaces derived from experimental findings.« less

Authors:
;  [1]
  1. Department of Mechanical Engineering, University of California, Berkeley, California 94720 (United States)
Publication Date:
OSTI Identifier:
20884972
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 101; Journal Issue: 1; Other Information: DOI: 10.1063/1.2402033; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ADHESION; CROSS-LINKING; CRYSTALS; FAR ULTRAVIOLET RADIATION; FRICTION; LAYERS; LITHIUM FLUORIDES; MICROSCOPY; MOLECULAR MODELS; PENETRATION DEPTH; PLASMA; POLYETHYLENES; RADIOWAVE RADIATION; SHEAR PROPERTIES; SUBSTRATES; SURFACE FORCES; SURFACE TREATMENTS; THICKNESS

Citation Formats

Tajima, S., and Komvopoulos, K. Dependence of nanomechanical modification of polymers on plasma-induced cross-linking. United States: N. p., 2007. Web. doi:10.1063/1.2402033.
Tajima, S., & Komvopoulos, K. Dependence of nanomechanical modification of polymers on plasma-induced cross-linking. United States. doi:10.1063/1.2402033.
Tajima, S., and Komvopoulos, K. Mon . "Dependence of nanomechanical modification of polymers on plasma-induced cross-linking". United States. doi:10.1063/1.2402033.
@article{osti_20884972,
title = {Dependence of nanomechanical modification of polymers on plasma-induced cross-linking},
author = {Tajima, S. and Komvopoulos, K.},
abstractNote = {The nanomechanical properties of low-density polyethylene (LDPE) modified by inductively coupled, radio-frequency Ar plasma were investigated by surface force microscopy. The polymer surface was modified under plasma conditions of different ion energy fluences and radiation intensities obtained by varying the sample distance from the plasma power source. Nanoindentation results of the surface stiffness versus maximum penetration depth did not reveal discernible differences between untreated and plasma-treated LDPE, presumably due to the small thickness of the modified surface layer that resulted in a substrate effect. On the contrary, nanoscratching experiments demonstrated a significant increase in the surface shear resistance of plasma-modified LDPE due to chain cross-linking. These experiments revealed an enhancement of cross-linking with increasing ion energy fluence and radiation intensity, and a tip size effect on the friction force and dominant friction mechanisms (adhesion, plowing, and microcutting). In addition, LDPE samples with a LiF crystal shield were exposed to identical plasma conditions to determine the role of vacuum ultraviolet (VUV) and ultraviolet (UV) radiation in the cross-linking process. The cross-linked layer of plasma-treated LDPE exhibited much higher shear strength than that of VUV/UV-treated LDPE. Plasma-induced surface modification of the nanomechanical properties of LDPE is interpreted in the context of molecular models of the untreated and cross-linked polymer surfaces derived from experimental findings.},
doi = {10.1063/1.2402033},
journal = {Journal of Applied Physics},
number = 1,
volume = 101,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}