Review on polyolefin elastomers with dynamic-chemical cross-linking

doi:10.11949/0438-1157.20231408

Abstract

Abstract:

Polyolefin elastomer (POE) is a high-end polyolefin material that is copolymerized from ethylene and α-olefin. It has excellent properties such as chemical stability, weather resistance and electrical insulation, and is widely used in various fields such as photovoltaic, automobile and cable. Dynamic-chemical cross-linking (DCC) can further improve its mechanical properties and thermal stability, and expand its application range while ensuring its processability. This paper reviews the preparation methods of DCC POEs, including one-step direct cross-linking and multistep cross-linking after functionalization. The functionalization methods, such as post-functionalization and copolymerization of ethylene and functional monomer, are elaborated. The characterization methods of DCC POEs and the relationship between their chain structure, aggregation structure and properties are discussed. The future prospects of DCC POEs are also presented. This paper aims to provide theoretical guidance and technical support for the controlled synthesis, structure-activity relationship study and high value application of DCC POEs, and to promote the innovation and development of high-end polyolefin materials.

Key words: polymer reaction engineering, high-end polyolefin, polyolefin elastomer, dynamic-chemical cross-linking, functionalization, structure-activity relationship

摘要：

聚烯烃类弹性体是由乙烯与丙烯或其他高碳α-烯烃共聚而成的高端聚烯烃材料，具有出色的化学稳定性、耐候性和电绝缘性，广泛应用于光伏、汽车、电缆等领域。通过动态化学交联可在保证其加工性的前提下，进一步提高其力学性能与热稳定性，拓展应用范围。综述了动态化学交联聚烯烃弹性体的制备工艺，包括一步法直接交联和功能化后再交联（多步法）。详细介绍了后功能化、乙烯与功能化单体共聚等功能化方法。讨论了动态化学交联聚烯烃类弹性体的表征手段及其链结构、聚集态结构和性能之间的关系。展望了动态交联聚烯烃类弹性体的未来发展。为动态化学交联聚烯烃类弹性体的可控制备、构效关系研究以及高值应用提供理论指导与技术支持，推动高端聚烯烃材料的创新和发展。

关键词: 聚合物反应工程, 高端聚烯烃, 聚烯烃类弹性体, 动态化学交联, 功能化, 构效关系

CLC Number:

TH 3

Yangke XIAO, Yinlong CHANG, Ping LI, Wenjun WANG, Bogeng LI, Pingwei LIU. Review on polyolefin elastomers with dynamic-chemical cross-linking[J]. CIESC Journal, 2024, 75(4): 1394-1413.

肖扬可, 常印龙, 李平, 王文俊, 李伯耿, 刘平伟. 动态化学交联聚烯烃类弹性体研究进展[J]. 化工学报, 2024, 75(4): 1394-1413.

Figures/Tables 15

Fig.1 Synthesis method of dynamically cross-linked polyolefin elastomers

Fig.2 (a) Free radical initiation reaction of DCP and OBC; (b) Free radical triggering double-ended vinyl boronic ester to cross-link OBC; (c) Free radical initiating small molecule cross-linker with disulfide bond to cross-link OBC; (d) Stress-strain curves of boronic ester dynamically cross-linked OBC using different DCP amount; (e) Processing of disulfide cross-linked OBC films using different dynamic cross-linker and DCP amount [the ratio of numbers in the figures, such as 3-1, represents 3%(mass) cross-linker loading and 1%(mass) DCP loading]

Fig.3 (a) The DASP functionalization and cross-linking of EPR; (b) Epoxidized EPDM cross-linked with biobased sebacic acid

Fig.4 (a) Synthesis of ethylene/1-tetradecene/9-(but-3-en-1-yl)anthracene copolymers with boronic ester cross-linking; (b) Synthesis of ethylene/1-octene/5-vinyl-2-norbornene copolymer with boronic ester cross-linking; (c) Synthesis of ethylene/propylene /8-furan-1-octene copolymer with DA or imine bond cross-linking; (d) Synthesis of branched POE with carboxyl group and POE with vinyl and polar functional group using Pd catalyst

Fig.5 (a) Preparation of high-performance polyolefin based TPE by dynamic-chemical combination method; (b) Comparison of tensile properties of novel TPE with other dynamically cross-linked elastomers, OBC, and CPOE

Fig.6 Different dynamic-chemical cross-linking through dissociation or exchange mechanisms

Fig.7 (a) Schematic of proposed mesostructure, fractal structure, and aggregate structure of boronic ester cross-linked PE; (b) AFM images of epoxidized myrcene and isoprene copolymers using cross-linkers with different chain length; (c) TEM images of dynamically cross-linked EPR with PEG of different number-average molecular weight(Mn); (d) SEM image of paraffin wax dynamically cross-linked POE

Table 1 Mechanical properties of dynamically cross-linked polyolefin based elastomers

样品类型	动态化学键	T_m/℃	杨氏模量/MPa	断裂强度/MPa	断裂伸长/ %	文献
商品EPDM	—	—	—	8.0~17.7	184~324	[11]
商品POE	—	36~104	3.8~5.8	1.4~38	600~1000	[11, 20, 86]
商品OBC	—	120	10.6	3~15	1300	[11, 86]
EPDM	酯键	—	2.5~4.5	19.4~22.7	240~390	[29]
EPR	DA键	—	0.84~26.04	4~6	<380	[45]
EPR	亚胺键	—	0.99~5.41	0.83~1.81	42~135	[40]
EPR	DA键	—	—	0.006~0.01	40~750	[87]
POE	硼酸酯键	—	4.2~12.8	2.5~21.3	250~1950	[39]
POE	硼酸酯键	55~80	14.8~29.0	12.8~23.8	470~630	[37]
POE	硼酸酯键	75.9~79.8	—	27.5~35.3	>800	[38]
OBC	硼酸酯键	—	—	15.3	2375	[46]

Fig.8 (a) Normalized stress relaxation curves at different temperatures; (b) Dilatometry test to determine Tv; (c) Illustration of the temperature-dependent AIE; (d) Coalesce of frequency-dependent material functions at Tv for tanδ

Fig.9 Comparison of functional EPDM, DA bond cross-linked EPDM, and sulfur-cured or peroxide-cured EPDM in Young’s modulus, tensile strength at break and elongation at break (a), and hardness and compression ratio (b); Hot pressing process and reprocessing mechanism of imide and disulfide dynamic chemical cross-linked PB (c); Photos and reaction mechanism of imide and disulfide dynamic chemical cross-linked PB via chemical recycling (d)

Fig.10 (a) Schematic illustrating cross-linking reaction and topological rearrangements via exchange reactions in ester bond cross-linked EPDM; (b) Typical stress-strain curves after multiple reprocessing cycles

Fig.11 Photos of fractured and repaired boronic ester cross-linked SBR, and photos of stretching repaired SBR (a); The typical stress-strain curves of the boronic ester cross-linked SBR repaired at 80℃ for various time (b) and repaired at different temperatures for 24 h (c); Fractured EPDM/SiO2 composites, and self-healing of EPDM/SiO2 composites under external force and heating (d)

Fig.12 Comparison of cross-linked polycycloctene (blue curve) and self-healing samples (red curve): the self-healing sample containing 0.5%(mole fraction) slow boronic ester cross-linking (a), and the self-healing sample containing 0.5%(mole fraction) fast boronic ester cross-linking (b); adhesion test and adhesion mechanism of PB samples with boronic ester cross-linking and permanent cross-linking (c); Adhesion properties of dynamic boronic ester cross-linked SBS (SBS-B) compared with original SBS and irreversible cross-linked SBS (SBS-H) (d)

Fig.13 (a) Reversible shape memory effects of ester bond cross-linked PEVA; (b) Angular variation in the temporary shape “V” of ester cross-linked PEVA during heating and cooling cycles; (c) Heat-triggered shape recovery performance of SBS; (d) Qualitative and quantitative characterization of shape memory behaviour

Fig.14 Boronic ester cross-linked POE/paraffin wax composites as actuators and artificial muscles

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