Mullins’ effect in thermoplastic elastomers: Experiments and modeling

Published Date
Mechanics Research Communications
June 2009, Vol.36(4):437–443, doi:10.1016/j.mechrescom.2008.12.007

• Author 

• A.D. Drozdov ^,

• Danish Technological Institute, Plastics Technology, Gregersensvej 1, DK–2630 Taastrup, Denmark

Received 25 September 2008. Revised 2 December 2008. Available online 25 December 2008. 

Abstract

Observations are reported on carbon black-reinforced thermoplastic elastomer in uniaxial cyclic tensile tests with various maximum strains at room temperature. A constitutive model is derived for a polymer composite that accounts for its viscoplastic response and damage. Adjustable parameters in the stress–strain relations are found by fitting the experimental data. It is shown that the model correctly reproduce characteristic features of the Mullins effect.

Keywords

Thermoplastic elastomer

Viscoplasticity

Damage 

Mullins’ effect

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A model for the mechanical response of composites with thermoplastic-elastomer matrices

Published Date
Composites Science and Technology
1 December 2006, Vol.66(15):2648–2663, doi:10.1016/j.compscitech.2006.03.017

• Author 

• A.D. Drozdov ^,

• Department of Chemical Engineering, Ben-Gurion University of the Negev, P.O. Box 653, Beer-Sheva 84105, Israel

Received 21 February 2006. Accepted 20 March 2006. Available online 5 May 2006. 

Abstract

Constitutive equations are derived for the elastic response of composites with thermoplastic-elastomer matrices at arbitrary three-dimensional deformations with finite strains. With reference to the homogenization method, a composite is thought of as an incompressible network of strands bridged by permanent junctions (filler particles and micro-domains in the crystalline or glassy states). Unlike conventional models for rubber elasticity, excluded-volume interactions between segments are taken into account. An explicit expression is developed for the strain energy density of a network of flexible chains with weak self-repellent interactions, and a phenomenological equation is suggested for the mechanically induced evolution in strength of segment interactions. The stress–strain relations involve three to four material constants that are found by matching experimental data on thermoplastic elastomers reinforced with short fibres and in situ composites with liquid-crystalline fillers. Good agreement is demonstrated between the observations and the results of numerical simulation at uniaxial tension with elongation ratios up to 1300%. It is shown that (i) adjustable parameters in the constitutive equations are affected by thermo-mechanical factors in a physically plausible way, and (ii) the model can predict the elastic response at one deformation mode when its material parameters are determined by fitting observations at another mode.

Keywords

A. Polymer-matrix composites (PMCs)

B. Stress/strain curves

C. Elastic properties

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A nanostructured carbon-reinforced polyisobutylene-based thermoplastic elastomer

Published Date
Biomaterials
March 2010, Vol.31(9):2477–2488, doi:10.1016/j.biomaterials.2009.12.003

Author 

Dedicated to Joseph P. Kennedy on the occasion of his 82nd birthday.

• Judit E. Puskas ^a,,
• Elizabeth A. Foreman-Orlowski ^a
• Goy Teck Lim ^a
• Sara E. Porosky ^a
• Michelle M. Evancho-Chapman ^b
• Steven P. Schmidt ^b
• Mirosława El Fray ^c
• Marta Piątek ^c
• Piotr Prowans ^d
• Krystal Lovejoy ^e

• aDepartment of Polymer Science, The University of Akron, Akron, OH 44325, USA
• bBiomedical Research Associates, 526 S. Main St., Akron, OH 44311, USA
• cPolymer Institute, Division of Biomaterials and Microbiological Technologies, Szczecin University of Technology, 70-322 Szczecin, Poland
• dClinic of General and Hand Surgery, Pomeranian Medical Academy in Szczecin, 71-252 Szczecin, Poland
• ePolyInsight, LLC, 526 S. Main St. Akron, OH 44325, USA

Received 8 November 2009. Accepted 1 December 2009. Available online 24 December 2009. 

Abstract

This paper presents the synthesis and characterization of a polyisobutylene (PIB)-based nanostructured carbon-reinforced thermoplastic elastomer. This thermoplastic elastomer is based on a self-assembling block copolymer having a branched PIB core carrying –OH functional groups at each branch point, flanked by blocks of poly(isobutylene-co-para-methylstyrene). The block copolymer has thermolabile physical crosslinks and can be processed as a plastic, yet retains its rubbery properties at room temperature. The carbon-reinforced thermoplastic elastomer had more than twice the tensile strength of the neat polymer, exceeding the strength of medical grade silicone rubber, while remaining significantly softer. The carbon-reinforced thermoplastic elastomer displayed a high T_g of 126 °C, rendering the material steam-sterilizable. The carbon also acted as a free radical trap, increasing the onset temperature of thermal decomposition in the neat polymer from 256.6 °C to 327.7 °C. The carbon-reinforced thermoplastic elastomer had the lowest water contact angle at 82° and surface nano-topography. After 180 days of implantation into rabbit soft tissues, the carbon-reinforced thermoplastic elastomer had the thinnest tissue capsule around the microdumbbell specimens, with no eosinophiles present. The material also showed excellent integration into bones.

Keywords

Biomaterials

SIBS

Carbon-reinforced thermoplastic elastomer

Mechanical properties

Hydrolytic stability

In vivo biocompatibility

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• ∗ 
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