Numerical analysis of the effect of temperature and its fluctuations on the vulcanization process of rubber seals

doi:10.11949/0438-1157.20231213

Abstract

Abstract:

As a key process in the rubber sealing molding, vulcanization has a significant impact on the performance of rubber sealing products. However, the rubber industry often adopts empirical vulcanization molding methods, lacking understanding of the evolution of vulcanization, making it difficult to theoretically guide the actual production process of rubber seals. In response to this weak link that restricts the improvement of rubber sealing quality, the paper conducted numerical simulation research on the vulcanization molding process of rubber seals. A transient simulation model for thermal-chemical coupling of rubber products was established based on an integral reaction kinetics model and a heat transfer control equation with variable physical parameters. Real time prediction of the time-varying temperature field and vulcanization degree field during the rubber product forming process was achieved, and the correctness of the model and solution method was verified through experiments. Furthermore, the vulcanization process of typical structural seals was simulated and analyzed, and the influence of mold temperature, rubber preheating temperature and temperature fluctuation behavior on the rubber seal vulcanization molding process was discussed. Finally, suggestions and references were provided for the actual vulcanization production of rubber seals.

Key words: rubber seals, fabrication, reaction kinetics, temperature fluctuations, numerical analysis

摘要：

硫化是橡胶密封成型过程的关键工艺，对橡胶密封产品性能有决定性影响。目前橡胶行业多采用经验式硫化成型方法，对橡胶密封硫化演变过程缺乏理解，难以理论指导橡胶密封实际生产过程。针对这一制约橡胶密封质量提升的薄弱环节，开展了橡胶密封硫化成型过程数值仿真研究。基于胶料的积分型反应动力学模型与变物性参数传热控制方程，建立了橡胶制品热-化学耦合的瞬态仿真模型，实现了橡胶制品成型过程时变温度场及硫化程度场的实时预测，并通过试验验证了模型及求解方法的正确性。进而，仿真分析了典型结构密封件的硫化过程，探讨了模具温度、胶料预热温度和温度波动行为对橡胶密封硫化成型过程的影响规律，最后为橡胶密封实际硫化生产提供了参考。

关键词: 橡胶密封, 加工制造, 反应动力学, 温度波动, 数值分析

CLC Number:

TQ 330.67

Zhaoxiang ZHANG, Maokun CAI, Zhiying REN, Xiaohong JIA, Fei GUO. Numerical analysis of the effect of temperature and its fluctuations on the vulcanization process of rubber seals[J]. CIESC Journal, 2024, 75(2): 715-726.

张兆想, 蔡茂坤, 任志英, 贾晓红, 郭飞. 温度及其波动对橡胶密封硫化过程影响的仿真分析[J]. 化工学报, 2024, 75(2): 715-726.

Figures/Tables 17

Table 1 Parameters of the reaction kinetics model for EPDM-60 rubber during vulcanization period

参数	数值/公式（160~185℃）
E_a /R	16606.73
h(α)	$h α = - 8.072 × 10 - 16 + 3.90698 × 10 - 21 e α - 0.48202 / 0.03156 + 1.20495 × 10 - 14 e α - 0.48202 / 0.29952$
h′(α)	$h' α = 3.90698 × 10 - 21 0.03156 e α - 0.48202 / 0.03156 + 1.20495 × 10 - 14 0.29952 e α - 0.48202 / 0.29952$

Table 1 Parameters of the reaction kinetics model for EPDM-60 rubber during vulcanization period

参数	数值/公式（160~185℃）
E_a /R	16606.73
h(α)	$h α = - 8.072 × 10 - 16 + 3.90698 × 10 - 21 e α - 0.48202 / 0.03156 + 1.20495 × 10 - 14 e α - 0.48202 / 0.29952$
h′(α)	$h' α = 3.90698 × 10 - 21 0.03156 e α - 0.48202 / 0.03156 + 1.20495 × 10 - 14 0.29952 e α - 0.48202 / 0.29952$

Fig.1 Comparison between model calculation curve and experimental curve

Table 2 Relationship between EPDM-60 thermophysical parameters and degree of vulcanization and temperature

参数	关系式
比定压热容/(J/(kg·K))	$c p α, T = 2806.51 - 3567.18 α + 2400.64 α 2 + 7.22 T - 6.76 × 10 - 3 T 2 - 4.76 α T$
热导率/(W/(m·K))	$k α, T = 0.23586 + 0.15850 α + 0.15146 α 2 - 0.24368 α 3 - 1.38146 × 10 - 4 T - 1.83456 × 10 - 7 T 2$

Table 2 Relationship between EPDM-60 thermophysical parameters and degree of vulcanization and temperature

参数	关系式
比定压热容/(J/(kg·K))	$c p α, T = 2806.51 - 3567.18 α + 2400.64 α 2 + 7.22 T - 6.76 × 10 - 3 T 2 - 4.76 α T$
热导率/(W/(m·K))	$k α, T = 0.23586 + 0.15850 α + 0.15146 α 2 - 0.24368 α 3 - 1.38146 × 10 - 4 T - 1.83456 × 10 - 7 T 2$

Fig.2 Solution schematic of transient heat transfer vulcanization coupling finite element model for rubber vulcanization

Fig.3 Subprogram for heat transfer vulcanization coupling solution in rubber vulcanization process

Fig.4 Sectional view of cylindrical vulcanized specimen

Fig.5 DSC test curves of different regions of the sample at different times

Fig.6 Calculation results of cylindrical rubber vulcanization

Fig.7 Comparison of experimental and simulation results for producing cylindrical rubber samples

Fig.8 Schematic diagram of seal structure in the study

Fig.9 Vulcanization process of seals of different sizes at different mold temperatures

Fig.10 Times required for different sizes and seal methods of seals to achieve 90% vulcanization

Fig.11 Comparison of vulcanization process of seals with a size of 20 mm at 175℃ with different preheating temperatures

Fig.12 Comparison of temperature and vulcanization degree at the center of the O-ring seal before and after preheating

Fig.13 Schematic diagram of mold temperature fluctuations at different adjustment frequencies

Fig.14 Vulcanization of O-ring seals with a cross-sectional diameter of 5 mm under different temperature fluctuations

Fig.15 Vulcanization of O-ring seals with a cross-sectional diameter of 20 mm under different temperature fluctuations

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