Study of the influence of non-polar rubbers on the low-temperature properties of chloroprene rubbers

Abstract

Improving the frost resistance and resistance of rubber to aggressive environments remains a pressing challenge in the development of elastomeric materials for use in cold climates. Despite the versatile performance properties of chloroprene rubber (CR), its tendency to crystallize and insufficient frost resistance limit its use at low temperatures. A promising area of research is modifying CR using non-polar rubbers with high elasticity and a low glass transition temperature. The aim of this work is to increase the frost resistance of rubbers based on chloroprene rubber by introducing a mixture of butadiene (BR) and styrene-butadiene (SBR) rubbers, as well as to study the effectiveness of using rubber mixtures to improve the performance characteristics of rubbers under low temperature conditions. The subjects of this study were rubber compounds based on CR grade Denka S40, BR grade B- Ti, and SBR grade 1810F. It has been established that the introduction of non-polar rubbers into CR-based rubbers improves frost resistance and stabilizes properties at low temperatures. Low-temperature studies have shown that the blended compounds exhibit higher frost resistance than the original CR-based rubber, confirming the effectiveness of the formulation modification approach. This is due to the fact that the introduction of low-glass transition rubbers (BR, SBR) and the reduction in crystallization ensure the preservation of elasticity at lower temperatures. Optimization of the formulation has achieved a balance between strength and frost resistance, making these compounds promising for use in cold climates.

Keywords

frost resistance chloroprene rubber butadiene rubber styrene-butadiene rubber low-temperature properties

Introduction

In cold climates, rubber products are significantly affected by low temperatures, which can cause loss of elasticity, cracking, and a decrease in strength characteristics.^1–5 Although chloroprene rubbers are not frost-resistant elastomers, they remain relevant in a number of applications due to their balanced resistance to ozone, atmospheric influences, and moderate resistance to oils and fuels.^6–12 In this regard, there is a need to study the possibility of expanding the operating temperature range of chloroprene rubbers by modifying their composition or structure.¹³ Due to their strength, resistance to oils and chemicals, and elasticity, chloroprene rubbers are widely used in various industries such as the automotive industry, construction, mining, cable production, and sealing materials, thanks to their versatile properties. These materials are used for the production of tires, conveyor belts, seals, protective coatings and products that can withstand exposure to aggressive environments.¹⁴

However, the use of such materials in extremely low-temperature conditions is accompanied by a number of problems, the main ones being reduced frost resistance and deterioration of physical properties.¹⁵ These changes not only limit the service life of rubber products but also increase maintenance and replacement costs. To address this issue, developments aimed at increasing the frost resistance of rubber are needed, which is especially relevant for use in northern and arctic regions.

One of the main principles in the creation of modern frost-resistant rubbers for use in arctic zones is a combination of rubbers of different types.^2,3,16 Small additions of butadiene rubber (BR) with a glass transition temperature, depending on its grade, from minus 95 to minus 110°C are used in rubbers based on polar rubbers to increase their frost resistance.¹⁷ However, due to the high crystallization rate of polybutadiene with a high content of cis-1,4-units, the frost resistance of rubbers based on it is limited by crystallization of the rubber, which can begin already at minus 40°C.¹⁸ Therefore, the advantage associated with the low glass transition temperature of stereoregular polybutadienes is not realized. The easy crystallization of polybutadiene significantly impairs the performance of rubbers based on it at low temperatures due to a significant decrease in elasticity and specific volume of the products. Thus, rubber seals lose their sealing ability.¹⁸ Therefore, to suppress crystallization processes, BR is most often used in mixtures with styrene-butadiene or isoprene rubbers.

The aim of this work is to increase the frost resistance of chloroprene rubber by adding butadiene and styrene-butadiene rubbers to the mixture, as well as to study the effectiveness of using rubber mixtures to improve the performance of rubbers at low temperatures.

Materials and methods

The main sample of the study was rubber based on chloroprene rubber (CR) of the Denka S-40 brand manufactured by DENKI KAGAKU KOGYO KABUSHIKI KAISHA (Japan). To improve the frost resistance of the material, butadiene rubber (BR) of the B- Ti brand (content of cis-1,4-units 87–93%) manufactured by JSC Voronezhsintezkauchuk (Russia) (TU 38.403750-2001) was selected. Styrene-butadiene rubber (SBR) of the 1810F brand manufactured by JSC Voronezhsintezkauchuk (Russia) (TU 2294-015-00148889-2012) was used to prevent BR crystallization. It is known that polybutadienes are used mainly in mixtures with other rubbers, most often with butadiene-styrene or isoprene, in quantities from 20 to 60 parts by weight per 100 parts by weight of rubber.³ Since the introduction of a large amount of non-polar rubbers will lead not only to an increase in the frost resistance of the blended compositions, but also to a deterioration in the oil and petrol resistance of the material, the total content of BR and SBR in the experimental rubbers does not exceed 20 parts by weight per 100 parts by weight of rubber, and SBR is added to the mixtures in quantities of 20 and 30 wt.% relative to the BR content. The formulations of the rubber mixtures are presented in Table 1.

Table 1.

Formulation of rubber compounds.

Ingredient	Rubber mixture
	RS 1	RS 2	RS 3	RS 4	RS5
	Content, wt.h.
CR Denka S40	100.0	90.0	80.0	90.0	80.0
BR B- Ti	-	8.0	16.0	6.7	13.3
SBR 1810F	-	2.0	4.0	3.3	6.7
Sulfur	1.0	1.0	1.0	1.0	1.0
N,N' - diphenylguanidine	1.0	1.0	1.0	1.0	1.0
Tetramethylthiuramdi-sulfide	1.0	1.0	1.0	1.0	1.0
Magnesium oxide	4.0	4.0	4.0	4.0	4.0
Zinc oxide	5.0	5.0	5.0	5.0	5.0
Carbon black P-803	50.0	50.0	50.0	50.0	50.0
Stearic acid	0.5	0.5	0.5	0.5	0.5

Carbon black grade P803 produced by JSC Ivanovo Tekhuglerod i Rezina (Russia) (CAS No. 1333-86-4), sulfur produced by Kaspiygaz LLC (Russia) (CAS No. 7704-34-9), zinc oxide produced by Chelyabinsk Chemical Plant OKSID LLC (Russia) (CAS No. 1314-13-2), magnesium oxide produced Mikhailovsky Plant of Chemical Reagents LLC (Russia) (CAS No. 1309-48-4), N, N′- diphenylguanidine produced by Willing New Materials Technology CO LTD (China) (CAS No. 102-06-7), tetramethylthiuram disulfide produced by Willing New Materials Technology CO LTD (China) (CAS No. 137-26-8) and stearic acid produced by Komponent-Reaktiv LLC (Russia) (CAS No. 57-11-4) were used for the preparation of rubber compounds. The rubber combination and plasticizer content in the studied rubber compounds are presented in Table 1. Rubber mixtures were prepared at a temperature not exceeding 100°C for 40 min on Cm350 150/150 rollers (China).

Results and discussion

The study of the vulcanization characteristics of elastomers was carried out on a rotorless rheometer RPA 2000 from Alpha Technologies (USA). Vulcanization characteristics were determined at a temperature of 145 and 150°C, deformation of 6.98%, deformation frequency of 1.67 Hz, for 30 min according to GOST R 54547-2011. Physical and mechanical properties were studied in accordance with accepted standards: elastic strength properties (GOST 270-75), density (GOST 267-73), Shore A hardness (GOST 263-75), resistance to hydrocarbon environments (GOST 9.030-74), wear resistance under abrasive wear (GOST 23509-79), relative residual compression deformation (GOST 9.029-74). The following low-temperature parameters were determined: brittleness temperature limit (GOST 7912-74), frost resistance coefficient under tension (GOST 408-78), ability to crystallize under compression (GOST 13270–85), glass transition temperature using a differential scanning calorimeter DSC 204 HP/1/G Phoenix from NETZSCH (Germany); measurements were carried out in the temperature range from −100°C to +25°C at a heating rate of 20 K/min.

Table 2 presents the results of determining the vulcanization characteristics of rubber compounds at different temperatures. It is shown that the addition of non-polar rubbers to the CR results in increased minimum and maximum torques for all rubber compounds, with the exception of the RS5 compound, which contains the highest amount of SBR.

Table 2.

Vulcanization properties of rubber compounds at 145/150°C.

No.	Vulcanization index	Value of the indicator at 145°C/150°C
No.	Vulcanization index	RS1	RS2	RS3	RS4	RS5
1	S' _max, dN-m	18.98/20.04	21.22/21.86	24.23/24.64	21.77/22.59	17.42/17.41
2	S' _min, dN-m	1.42/1.33	1.78/1.63	2.04/1.91	1.76/1.71	1.85/1.74
3	S' _max - S′ _min, dN-m	17.56/18.71	19.44/20.23	22.19/22.73	20.01/20.88	15.57/15.67
4	T ₅, min	3.99/3.21	3.44/2.65	1.93/1.59	3.13/2.50	2.31/1.80
5	T _35, min	8.71/6.75	8.55/6.42	4.88/3.87	7.90/5.98	5.14/3.86
6	T ₉₀, min	21.97/19.23	21.19/17.94	18.57/15.56	19.97/16.58	12.99/10.19
7	R _v, min⁻¹	5.56/6.24	5.63/6.54	6.01/7.16	5.94/7.10	9.36/11.92

S' _max, dN-m – maximum torque; S′ _min, dN-m – minimum torque; T ₅, min – pre-vulcanization start time; T _{35, min –} pre-vulcanization end time; T ₉₀, min – time to reach optimum vulcanization, R _V, min⁻¹ – vulcanization speed.

The longest induction period, which is the time from the start of heating the mixture to the onset of intense cross-linking (i.e., the loss of plasticity), was found in the CR-based rubber without the addition of other rubbers (mixture RS1). This indicates high processability of the mixture at the initial stage. Mixtures RS3 and RS5 are characterized by the shortest induction period, indicating their accelerated cross-linking reaction.

These same compounds (RS3 and RS5) reach optimum vulcanization faster than the others. Optimum vulcanization corresponds to the time at which the best combination of rubber strength and elasticity is achieved, which is reflected in the peak of the vulcanization curve. RS3 and RS5 compounds also exhibit the highest rate of spatial network formation during vulcanization, making them more reactive.

Increasing the vulcanization temperature accelerates all stages of the process: the start and completion times of scorch are reduced, and the time it takes to reach optimum vulcanization is also shortened. However, torque values change only slightly.

Based on the results of the vulcanization characteristics study, all samples were vulcanized in a Y1000D vacuum hydraulic press (China) at a temperature of 150°C for 25 min.

The results of the physical and mechanical tests of the rubbers are presented in Table 3. The nominal tensile strength, which is the stress generated in a sample at the moment of its failure under the action of a uniaxial tensile force, was virtually identical for all the vulcanizates studied, with deviations not exceeding 10%. This indicates comparable strength of the vulcanizates at final deformation, regardless of the rubber compound composition.

Table 3.

Physical and mechanical properties of rubbers.

No.	Indicators	Designation of rubber compound
No.	Indicators	RS1	RS2	RS3	RS4	RS5
1	Conventional tensile strength, MPa	21.6 ± 1.3	20.4 ± 1.2	20.1 ± 1.6	21.2 ± 1.9	21.4 ± 1.7
2	Stress at 100% elongation, MPa	3.9 ± 0.3	4.5 ± 0.2	5.5 ± 0.1	4.6 ± 0.2	3.7 ± 0.07
3	Relative elongation at break, %	479 ± 21	405 ± 15	333 ± 14	411 ± 21	519 ± 21
4	Density, g/^cm3	1.433 ± 0.06	1.394 ± 0.07	1.346 ± 0.006	1.379 ± 0.004	1.364 ± 0.007
5	Shore A hardness, c.u.	57 ± 4	68 ± 1	71 ± 2	68 ± 1	64 ± 1
6	Volumetric wear, ^cm3	0.038 ± 0.001	0.042 ± 0.001	0.049 ± 0.002	0.046 ± 0.0006	0.046 ± 0.001
7	Residual compression strain, %	71 ± 4	63 ± 3	56 ± 2	57 ± 1	56 ± 2
8	Degree of swelling in IRM-901 (72h*100°C), %	13.2 ± 0.6	17.0 ± 0.6	22.2 ± 0.8	17.5 ± 0.08	22.4 ± 0.5

The tensile stress at 100% elongation, that is, the force required to stretch a sample twice, is an indicator of the rubber’s resistance to deformation in the elastic regime. This indicator naturally increases with increasing butadiene and styrene-butadiene rubber content in rubber compounds. At the same time, a tendency toward a decrease in relative elongation at break is observed, with the exception of the RS5 compound, which may be due to the structural organization of the cross-linked network.

It was also found that the introduction of BR and SBR rubbers leads to an increase in rubber hardness by 8–17%, to values of 64–71 Shore A units. At the same time, the volumetric wear of the rubber increases from 9 to 22%, which may indicate a change in the microstructure of the material and an increase in its resistance to abrasion.

The results of determining the density of the rubber compounds are presented in Table 5. As can be seen from the presented data, the density of the compositions varies in the range from 1.346 to 1.433 g/cm³. The highest density value was recorded for the RS1 compound (1.433 g/cm³), containing only chloroprene rubber, which is explained by the high intrinsic density of this rubber, caused by the presence of chlorine atoms in the polymer structure. With the introduction of butadiene and styrene-butadiene rubbers, which have a lower density, a natural decrease in the density of the rubbers is observed. The minimum value was observed for the RS3 sample (1.346 g/cm³), which includes a significant amount of low-density butadiene rubber. Mixtures RS4 and RS5 demonstrate intermediate density values - 1.379 and 1.364 g/cm³, respectively, which reflects the combined effect of the interaction of all components. Thus, it can be concluded that the density of rubber compounds depends significantly on the nature and proportion of the rubbers used, as well as the possible influence of fillers and other formulation components. Reducing the material’s density can be considered a positive factor in terms of reducing the weight of finished products, but it must also take into account the potential changes in other performance characteristics.

One of the important performance indicators of rubber seals is the relative compressive strain (RCS), which is composed of reversible (relaxation) and irreversible (crosslinking or degradation) components. The lower the RCS, the greater the elastic recovery of the rubber after compression.^19,20 Rubbers with the highest SBR content, namely, mixtures of RS3 and RS5, exhibit minimal RCS.

In addition to adequate elastic-strength properties, a critical indicator of the operational reliability of rubbers used in seals is their resistance to hydrocarbon environments.²¹ Table 3 presents the results of determining the degree of swelling of rubbers in a medium containing IRM-901, which is a distillate product from low-paraffin crude oil. Since IRM-901 is a hydrocarbon medium, the swelling of the blended compositions increases with increasing content of non-polar rubbers BR and SBR.

A disadvantage of chloroprene rubber-based products is the operating temperature range of products made from them, namely, low frost resistance. The addition of butadiene and styrene-butadiene rubbers to the rubber composition significantly increases the frost resistance of the material. Figure 1 shows the results of determining the brittleness temperature limit. For CR-based rubber, this value is minus 33°C. With the addition of 16.0 parts by weight of BR and 4.0 parts by weight of SBR, the temperature drops to minus 59°C, and with the addition of 13.3 parts by weight of BR and 6.7 parts by weight of SBR, the temperature drops to minus 61°C. This is due to the high frost resistance of BR and the prevention of crystallization by the addition of SBR.

Rubber produced from a blend of chloroprene, butadiene, and styrene-butadiene rubbers has a low glass transition temperature (Table 4). This property allows the material to maintain elasticity and mechanical properties at low temperatures, which is especially important for use in extreme cold conditions, such as arctic zones.

Table 4.

Glass transition temperature and frost resistance coefficient of rubbers.

Rubber	RS1	RS2	RS3	RS4	RS5
Tg, °C	−37.8	−40.7	−42.4	−40.4	−41.8
Km at −45°C	0.010	0.031	0.193	0.033	0.362

The results of the study determining the frost resistance coefficient at −45°C are presented in Table 4. Rubber based on a blend of chloroprene, butadiene, and styrene-butadiene rubbers is characterized by an increased tensile frost resistance coefficient. This indicator indicates the material’s ability to maintain strength and resist destruction under low temperatures, making it suitable for use in extremely cold conditions.

The most important factor limiting the performance of chloroprene rubbers at low temperatures is their tendency to spontaneous crystallization. This phenomenon is characteristic primarily of chloroprene rubber, whose molecules have a regular structure and polar side groups (chlorine atoms), which facilitate the ordered arrangement of chains. Crystallization is accompanied by a decrease in elasticity, an increase in rigidity, and can lead to brittle fracture of the material during use. According to literature, chloroprene rubbers are prone to slow but stable crystallization during storage, especially at temperatures ranging from −5 to +15°C, making it necessary to study this process when designing frost-resistant rubber compounds.²²

Evaluating the crystallization properties of the developed rubbers allowed us to determine how effectively blending chloroprene rubber with other elastomers reduces the material’s tendency to form a uniform structure and, consequently, improves its performance at low temperatures. The degree of crystallinity (Y) was used for this evaluation (1).

Y = 1 - \frac{K_{1}}{K_{0}}

(1)

where,

K₁ – sample recoverability after crystallization,

K₀ – recoverability of a sample in the absence of crystallization.

According to the data obtained (Figure 2), RS1 rubber, which contains only chloroprene rubber, exhibits the highest crystallinity: its degree of crystallinity is 0.62—the highest value among all the samples studied. With the addition of butadiene (BR) and styrene-butadiene (SBR) rubbers, the degree of crystallinity decreases. The minimum Y value of 0.31 was observed for RS5 rubber, indicating the lowest proportion of the crystalline phase at equilibrium. The results of determining the crystallization capacity of rubbers correlate with their brittleness temperature. For example, RS5 rubber has a minimal proportion of the crystalline phase, which is why this rubber has better frost resistance.

Conclusion

It has been shown that the combination of chloroprene rubber with butadiene and styrene-butadiene rubbers makes it possible to obtain a material with a satisfactory set of physical, mechanical and low-temperature properties with the following ratios of rubbers CR/BR/SBR (parts by weight): 80.0/16.0/4.0 (RS3) and 80.0/13.3/6.7 (RS5). The main advantage of introducing non-polar rubbers into a chloroprene rubber-based compound is a significant improvement in frost resistance due to reduced CR crystallization. This is due to the disruption of molecular packing due to the blending of rubbers with different structures. Increasing the frost resistance of the studied rubbers will allow for the reliable use of rubbers in various industries at low temperatures.

Footnotes

ORCID iDs

Aytalina F. Fedorova

Mariya L. Davydova

Funding

The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by Ministry of Science and Higher Education of the Russian Federation; Grant No: 125121014137-4.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

References

Buznik

Kablov

Koshurina

. Materialy dlya slozhnykh tekhnicheskikh ustrojstv arkticheskogo primeneniya. Nauchno-tekhnicheskie problemy osvoeniya arktiki. Nauka, 2015, pp. 275–285.

Chajkun

Eliseev

Naumov

, et al. Osobennosti postroeniya receptur dlya morozostojkikh rezin. Aviacionnye Materialy I Tekhnologii 2013; 3: 53.

Buznik

Vasilevich

. Materialy dlya osvoeniya arkticheskikh territorij – Vyzovy i resheniya. Laboratoriya I Proizvodstvo 2020; 1(11): 98–107. https://doi.org/10.32757/2619-0923.2020.1.11.98.107

Vahrusheva

YumashevO

Chajkun

. Sovremennye tendencii v oblasti morozostojkih rezin na osnove polyarnyh i nepolyarnyh kauchukov. Trudy VIAM 2022; 4(108): 06. https://doi.org/10.18577/2307-6046-2022-0-4-6-6

Muhin

Petrova

Lazareva

. Vliyanie sostava i tekhnologii izgotovleniya kompozicij na strukturu i svojstva morozostojkih rezin na osnove smesej polyarnyh i nepolyarnyh kauchukov. Prirodnye Resursy Arktiki I Subarktiki 2023; 2(28): 346–357. https://doi.org/10.31242/2618-9494-2023-28-2-346-357

Treger

Morozov

Dasaeva

, et al. Chloroprene rubber: application and production. Fine Chem Technol 2018; 13(4): 26–38. https://doi.org/10.32362/2410-6593-2018-13-4-26-38

Das

Costa

Wagenknecht

, et al. Nanocomposites based on chloroprene rubber: effect of chemical nature and organic modification of nanoclay on the vulcanizate properties. Eur Polym J 2008; 44: 3456–3465. https://doi.org/10.1016/j.eurpolymj.2008.08.025

Zheng

Wen

, et al. Graphene oxide-supported zinc oxide nanoparticles for chloroprene rubber with improved crosslinking network and mechanical properties. Composites, Part A 2019; 124: 105492. https://doi.org/10.1016/j.compositesa.2019.105492

Xiang

Rong

Zhang

. Self-healing, reshaping, and recycling of vulcanized chloroprene rubber: a case study of multitask cyclic utilization of cross-linked polymer. ACS Sustainable Chem Eng 2016; 4(6): 2715–2724. https://doi.org/10.1021/acssuschemeng.6b00237

10.

Kapgate

Das

, et al. Reinforced chloroprene rubber by in situ generated silica particles: evidence of bound rubber on the silica surface. J Appl Polym Sci 2016; 133(28): 43717. https://doi.org/10.1002/app.43717

11.

Kong

Zhu

Huang

, et al. Carbon nanodots as dual role of crosslinking and reinforcing chloroprene rubber. Compos Commun 2020; 22: 100441. https://doi.org/10.1016/j.coco.2020.100441

12.

Maya

George

Jose

, et al. Development of a flexible and conductive elastomeric composite based on chloroprene rubber. Polym Test 2018; 65: 256–263. https://doi.org/10.1016/j.polymertest.2017.11.012

13.

Kochnev

Galibeev

. Modifikaciya polimerov. Kazanskij Gosudarstvennyj Tekhnologicheskij Universitet, 2008, pp. 533s.

14.

Denka Company . Official website. URL. https://www.denka.co.jp/eng/product/detail_00002, Accessed: January 18, 2026.

15.

Petrova

. Principy sozdaniya maslo-i morozostojkikh rezin i ikh realizaciya dlya ehkspluatacii v usloviyakh kholodnogo klimata: dis. ... d-ra tekhn, nauk: 05.17.06; MITKHT im. M.V. Lomonosova. – Kazan. 2008; 312 p.

16.

Grishin

BS.

Rezinovaya promyshlennost’ Rossii — ot nastoyashchego, cherez proshloe k budushchemu. Promyshlennoe proizvodstvo i ispol’zovanie ehlastomerov. 2015; 1: 3–9.

17.

Kornev

Bukanov

Sheverdyaev

. Tekhnologiya ehlastomernykh materialov . M.: NPPA «IsteK». 2009; 504.

18.

Bol’shoj spravochnik rezinshchika. Ch.2. Reziny i rezinotekhnicheskie izdeliya/Pod red. Reznichenko S.V., Morozova Yu.L. M.: OOO «Izd. centr «TekhinforM» MAI» 2012; 649 p.

19.

Gavrilov

Fiziko-mekhanicheskie svojstva khloroprenovykh rezin i ikh iznosostojkost. Vestnik Kazanskogo Tekhnologicheskogo Universiteta 2019; 5 (22): 45–50.

20.

Petrov

Smirnov

Vliyanie napolnitelej na iznosostojkost’ khloroprenovykh rezin. Polimery 2020; 3 (62): 28–34.

21.

Uitiro

Takasi

. Kodzuka takakhiro khloroprenovyj kauchuk, kompoziciya khloroprenovogo kauchuka, ego vulkanizat i formovannoe izdelie: patent RF № 2612939. – opubl. Zayavitel’: Denka Kompani Limited, 2017.

22.

Bukhina

Kurlyand

. Morozostojkost’ ehlastomerov. 176 s. Khimiya, 1989.