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HINA R&P TECHNOLOGY AND EQUIPMENT

after aging. applications. Typical EPDM aging temperatures include 70°C,
100°C, 125°C, 150°C, and 175°C. ASTM D 4637 specifies
2 Results and discussion requirements for black EPDM roofing membranes, which
2.1 Rubber compound processing performance undergo oven aging at 116°C for 28 days or 7 days, with tensile
The Mooney viscosity and vulcanization characteristics strength after aging not less than 8.3 MPa and elongation at
of the rubber compound are shown in Table 1. break not less than 200%.
Table 1 Vulcanization characteristics of rubber This study tested the tensile properties of a kind of
compound EPDM vulcanized rubber with two formulations after aging
Formula Number
Project at temperatures of 100°C, 120°C, 130°C, and 150°C, and
1 # 2 #
M L (1+4)125 ℃ 56.2 60.6 established a simple model for predicting the thermal aging
t 10 /min 3 2
t 90 /min 21 18 properties of EPDM rubber at different temperatures and
durations.
2.2 Aging performance standards for rubber 2.3 Change in tensile properties after aging
compound Tables 2~5 and Figure 1 show the changes in tensile

Thermo-oxidative aging is the primary cause of rubber strength of 1 and 2 ethylene propylene diene monomer
#
#
damage. Rubber undergoes thermo-oxidative aging below (EPDM) vulcanizate samples after undergoing different aging
200 ℃, with oxygen being the main factor causing aging, and times at 100 ℃, 120 ℃, 130 ℃, and 150 ℃, respectively.
heat playing a role in activating oxidation and accelerating the From the figures and tables, it can be observed that the
process. Aging occurs through free radical reactions, where peroxide-vulcanized 2# vulcanizate has higher strength and
bonds in the polymer break, forming carbon radicals, which lower elongation at break compared to the sulfur-vulcanized 1#
may lead to the formation of new cross-linking bonds. The vulcanizate. After aging, both vulcanizate samples exhibit the
generation of new cross-linking bonds causes the polymer to same pattern of physical property loss, with the tensile strength
harden and become brittle. For EPDM, changes in elongation initially showing a sharp decrease, followed by a gradual
at break are a sensitive indicator of aging. decrease as the aging time increases, while the elongation
Conveyor belts are frequently utilized in high- at break continues to decrease significantly. Furthermore,
temperature environments such as chemical and metallurgical the higher the aging temperature, the more severe the loss
industries, necessitating their maintenance of superior in strength and elongation at break. From the figure, it is
mechanical properties under such conditions. According to the also possible to estimate the corresponding time at various
specifications outlined in GB/T20021-2005 for heat-resistant aging temperatures assuming a certain level of strength and
canvas core conveyor belts, these belts are categorized into elongation at break after aging. These results indicate that
four grades based on their level of heat resistance. Specifically, high-temperature short-time aging can be used to infer the
Grade T3 is suitable for use in environments with temperatures application at low temperatures.
up to 150℃, while Grade T4 is suitable for temperatures up to Table 2 Performance of the sample before and after
175℃. Generally, heat-resistant conveyor belts of Grades T3 aging, with an aging temperature of 100 ℃
1 # 2 #
and T4 incorporate EPR or EPDM in combination with other Aging time /h tensile Elongation at tensile Elongation at
heat-resistant materials, along with additional measures, to strength T b break E b strength T b break E b
0 12 532 14.4 472
enhance their heat resistance. 168 12.1 301 14.9 321
336 12 266 14.9 296
The automotive and roofing industries widely use
672 11.9 254 14.6 243
accelerated thermal aging methods for quality assurance 1008 11.2 216 13.8 230
1680 10.7 160 13 196
testing of elastomeric vulcanizates, typically specifying 4224 8.8 92 11.8 118
minimum values after aging. Standards ASTM D 2000 8760 8.4 73 11.7 35
and SAE J200 specify test conditions for many automotive

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