3.33. Degradation of Natural Rubber and Synthetic Elastomers

Published Date
Reference Module in Materials Science and Materials Engineering

Shreir's Corrosion

Volume 3, 2010, Pages 2407–2438, doi:10.1016/B978-044452787-5.00117-7

Current as of 28 October 2015.

Author 

• A. bin Samsuri

This chapter begins with some basic definitions and classifications of rubber and elastomers, followed by short discussions on the structure–property relationship and a brief introduction to rubber compounding and technology. The idea is to facilitate the understanding of readers who may have little background in the field of rubber science and technology, in view of the wide background of anticipated readership. The technology of bonding rubber to metal is an important aspect of protecting metal surfaces against corrosion, and this chapter covers all the important aspects of obtaining efficient bonding and high bond strength. Although rubbers protect metals against corrosion, they are also subject to corrosion brought about by degradation associated with oxidation, ozone cracking, heat aging, flex cracking and liquid absorption. Factors affecting the degradation of rubber and the means of protecting against degradation and the relevant mechanisms are also discussed.

Keywords

• Antioxidants
• Antiozonants
• Blooming
• Corrosion
• Elastomers
• Heat aging
• Oxidation
• Ozone cracking
• Rubber-to-metal bonding
• Volume swell

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Abbreviations

ACM

Polyacrylic rubber

ASTM

American Society for Testing Materials

CED

Cohesive energy density

CIIR

Chlorinated butyl rubber

CM

Cement metal failure

CP

Cement primer failure

CR

Polychloroprene rubber

CSM

Chlorosulfonated polyethylene rubber

DCP

Dicumyl peroxide

DOPPD

Dioctyl-p-phenylenediamines

ECO

Copolymer of epichlorohydrin rubber

ENR50

Epoxidized natural rubber (50 mol% epoxidation)

EPM

Ethylene propylene rubber

EV

Efficient vulcanization

GRG

General rubber goods

IHRD

International Rubber Hardness Degrees

IIR

Isobutylene isoprene (butyl) rubber

IR

Synthetic polyisoprene rubber

IRG

Industrial rubber goods

ISO

International Organization for Standardization

MRB

Malaysian Rubber Board

MRPRA

Malaysian Rubber Producers Research Association

MS

Malaysian standard

NBR

Nitrile rubber

NR

Natural rubber

PP

Polypropylene

PTR

Polysulphide rubber

SBR

Styrene butadiene rubber

TAC

Triallyl cyanurate

TAIC

Triallylisosyanurate

TARRC

Tun Abdul Razak Research Centre

UiTM

Mara University of Technology

UV

Ultraviolet light

XNBR

Carboxylated nitrile rubber

Symbols

A

Cross-sectional area (m²)

A_o

Unstrained (original) cross-sectional area (m²)

B

Crack growth constant

c

Crack length (mm, m)

c_o

Natural flaw size (mm, m)

C_o

Concentration of antiozonant (mg cm⁻²)

C_s

Concentration of antiozonant at the rubber surface (mg cm⁻²)

D

Diffusion coefficient (m² s⁻¹)

dc/dt

Crack growth rate (m s⁻¹)

f

Force (N)

f_f

Frequency (Hz)

h

Height (m)

k_c

Compression stiffness (N m⁻¹)

k_s

Shear stiffness (N m⁻¹)

l

Half thickness of film sheet (mm, m)

L

Length (m)

M

Molecular weight (g mol⁻¹)

M_∞

Total mass of liquid absorbed after an infinite time (g, kg)

M_L

Mass of layer per unit area of surface (g mm⁻², kg m⁻²)

M_t

Total amount of liquid absorbed per unit area after immersion time, t (g mm⁻²s^1/2)

N

Number of molecules per unit volume of rubber (mol cm⁻³)

N_f

Fatigue life (number of cycles of failure) (cycles, kilocycles)

R

Molar gas constant (8314 J mol⁻¹ K⁻¹)

S

Shape factor

T

Absolute temperature (K)

t

Time (s)

T_g

Glass-transition temperature (°C, K)

V₁

Molar volume of solvent (m³)

v_f

Volume fraction of seeding particles present in the rubber

v_r

Volume fraction of rubber in the swollen gel

W

Width (m)

W_s

Strain energy density (J m⁻³)

[X]_phy.

Physically manifested crosslink concentration (mol kg⁻¹)

δ

Solubility parameter (MPa)^1/2

ΔH

Latent heat of vaporization (J)

λ

Extension ratio

ρ

Density (kg m⁻³)

χ

Rubber–solvent interaction parameter

Figure 1.

 Table 1

Table 1.

 Table 2

Table 2.

 Table 3

Table 3.

 Table 4

Table 4.

Figure 2.

Figure 3.

 Table 5

Table 5.

Figure 4.

 Table 6

Table 6.

Figure 5.

 Table 7

Table 7.

Figure 6.

Figure 7.

Figure 8.

Figure 9.

Figure 10.

Figure 11.

Figure 12.

Figure 13.

Figure 14.

Figure 15.

 Table 8

Table 8.

Figure 16.

Figure 17.

Figure 18.

Figure 19.

Figure 20.

Figure 21.

Copyright © 2010 Elsevier B.V. All rights reserved.

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