Degradation of Natural Rubber and Synthetic Elastomers

Published Date
Reference Module in Materials Science and Materials Engineering
2017, doi:10.1016/B978-0-12-803581-8.09212-2

• Author 

• A. Bin Samsuri

• A.A. Abdullahi

Abstract

Degradation elastomers is very complex as it involves many factors such as oxygen, ozone, mechanical strain, heat, trace metals. However, elastomers have unique superior features over metals; which make these materials suitable for special applications. For instance, the elastomers are used in bridge bearings and seismic bearings, vibration isolators, engine mounts, and springs. Meanwhile, some applications of rubbers are in manufacturing of tires, curing bladders, gaskets, seals, automotive components, rubber springs, and rubber bearing. In addition, these engineering materials are used in protecting metals against corrosion. Despite these benefits, rubbers and elastomers experienced degradation associated with oxidation, ozone cracking, heat aging, flex cracking, and liquid absorption. Factors affecting the degradation of rubber as well as the mechanisms of reducing the degradation are presented. Improved natural rubber and synthetic elastomers will be more useful for both domestic and industrial applications in construction of aeronautical and automobile engineering products. Therefore, this state-of-the-art review on natural rubber and synthetic elastomers is required for present and future applications of the desired elastomeric products.

Keywords

• Antioxidants
• Antiozonants
• Blooming
• Corrosion
• Degradation
• Elastomers
• Heat aging
• Natural rubber
• Oxidation
• Ozone cracking
• Polymers
• Rubber-to-metal bonding
• Strength
• 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

Polysulfide 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)

A₀

Unstrained (original) cross-sectional area (m²)

B

Crack growth constant

c

Crack length (mm, m)

c₀

Natural flaw size (mm, m)

C₀

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.

• ☆
  Change History: December 2015. A.A. Abdullahi added Abstract and Keywords; Introduction section is expanded with additional recent review of literature; Equation numbering is consolidated; Figures 1, 6 and Table 6 is updated; acknowledgments section is updated accordingly; and updated the list of references.

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