Synthesis of reactive macromolecular antioxidants and their antioxidation properties in EPDM

doi:10.19491/j.issn.1001-9278.2023.01.015

Abstract

Abstract:

A reactive macromolecular antioxidant （hereafter named "TMPTMA/MB"） was synthesized through a free radical⁃initiated reaction of trimethylolpropane trimethacrylate （TMPTMA） with 2⁃mercaptobenzimidazole （MB）. The chemical structure of TMPTMA/MB was characterized by using Fourier⁃transform infrared spectroscopy， X⁃ray photoelectron spectroscopy， and elemental analysis. The effect of TMPTMA/MB on the vulcanization characteristics， tensile properties， and oxidation resistance of EPDM were investigated. The results indicated that TMPTMA/MB was grafted onto the EPDM molecular chains， followed by consuming the alkoxy radicals generated by the peroxide decomposition. This slowed down the vulcanization rate of the rubber and reduced its crosslinking degree. The grafted TMPTMA/MB enhanced the internal friction of molecular chains under the action of external forces and therefore improved the tensile properties of EPDM. In addition， the TMPTMA/MB grafted on the EPDM molecular chains has high migration resistance， thus improving the oxidation resistance of EPDM significantly.

Key words: reactive macromolecular antioxidant, vulcanization characteristics, tensile property, migration resistance, oxidation resistance

CLC Number:

TQ314.24

LIU Qingkun, CONG Chuanbo, MENG Xiaoyu, ZHOU Qiong. Synthesis of reactive macromolecular antioxidants and their antioxidation properties in EPDM[J]. China Plastics, 2023, 37(1): 99-105.

Figures/Tables 12

样品	EPDM质量	MB/EPDM 质量	TMPTMA/MB/EPDM质量
生胶	100	100	100
DCP	1	1	1
MB	-	1	-
TMPTMA/MB	-	-	5.9

Tab.1. Rubber compound formulation

Fig.1. Scheme of chemical structures of MB and TMPTMA

Fig.2. FTIR spectra of MB， TMPTMA and TMPTMA/MB

Fig.3. XPS spectra of MB， TMPTMA and TMPTMA/MB

样品	C含量	N含量	H含量	S含量
MB^T	56.00	18.67	4	21.33
MB^E	55.84	18.49	3.96	21.44
TMPTMA^T	63.9	0	7.69	0
TMPTMA：MB=2.2：1^T	62.6	3.14	7.07	3.60
TMPTMA/MB^E	62.1	3.38	7.00	3.63

Tab.2. Element analysis of MB， TMPTMA and TMPTMA/MB

Fig.4. Reaction mechanism of TMPTMA with MB

Fig.5. Vulcanization curves of EPDM， MB/EPDM and TMPTMA/MB/EPDM blends

样品	tc₁₀/min∶s	tc₉₀/min∶s	M_L/dN•m	M_H/dN•m	CR_max/dN•m•min^-1	交联密度/×10^-4 mol•cm^-3
EPDM	1∶48	18∶07	0.48	7.11	0.72	1.03±0.01
MB/EPDM	1∶58	17∶08	0.38	4.81	0.52	0.51±0.03
TMPTMA/MB/EPDM	2∶33	19∶57	0.35	4.00	0.31	0.32±0.02

Tab.3. The vulcanization parameters and crosslinking densities of EPDM， MB/EPDM and TMPTMA/MB/EPDM vulcanizates

Fig.6. The stress⁃strain curves of EPDM， MB/EPDM and TMPTMA/MB/EPDM vulcanizates

Fig.7. N 1s XPS spectra of EPDM raw rubber sheets in contact with antioxidant/EPDM vulcanizates

Fig.8. Crosslinking density and change rate for crosslinking density of EPDM， MB/EPDM and TMPTMA/MB/EPDM vulcanizates

Fig.9. Tensile strength， elongation at break and aging coefficient K of EPDM， MB/EPDM and TMPTMA/MB/EPDM vulcanizates before and after aging

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