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. 2025 May 17;10(21):22224–22234. doi: 10.1021/acsomega.5c02670

Preparation of High-Performance Biobased Itaconate Elastomer Nanocomposites by Constructing Dual-Cross-Linked Networks

Yanguo Li †,‡, Hui Yang †, Jing Xu ‡, Haijun Ji †,*, Wencai Wang †,*, Runguo Wang †,*, Feng Wang ‡, Liqun Zhang †,§
PMCID: PMC12138595  PMID: 40488022

Abstract

As a high biobased synthetic rubber, an itaconate elastomer is critical for advancing sustainable tire manufacturing, thereby offering a viable solution to mitigate reliance on petrochemical feedstocks and curtail carbon emissions within the rubber industry. In this study, performance comparisons between two industrially available biobased itaconate elastomers (BIE) and commercial solution-polymerized styrene–butadiene rubber (SSBR) indicated that BIE/silica exhibited higher dry sliding/rolling friction coefficients. It is attributed to the superior frictional damping efficiency of side ester groups in BIE compared to styrene and vinyl moieties in SSBR. In addition, to address the inherent challenges of low cross-linking efficiency and network density caused by the molecular structure of BIE, an innovative dual cross-linking system was developed by combining amino-functionalized polysulfide (PDAS) with sulfur. This system simultaneously activated cross-linking reactions at both double bonds and diester groups, enabling efficient vulcanization of the elastomer. Systematic investigations were conducted to characterize the effects of the PDAS dosage on cross-linking density, filler dispersion, and dynamic/static mechanical properties. Validated with a high-performance tire formulation, BIE/silica with the dual-cross-linked system had reached the same level as SSBR/silica in terms of cross-linking density, mechanical properties (tensile strength: 17.4 MPa, elongation at break: 422%), and Akron abrasion resistance. It also showed balanced dynamic mechanical properties (tan δ = 0.744 at 0 °C and tan δ = 0.092 at 60 °C). These results provide data support and a technical path reference for the industrial application of BIE in green tire manufacturing.

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1. Introduction

Amidst the sustained expansion in the global transportation sector and the rapid growth of the automotive industry, the tire industry, serving as a core supporting sector, is experiencing new growth opportunities. Both the steady evolution of traditional fuel-powered vehicles and the rapid rise of new energy vehicles continue to generate persistent and substantial demand for tires. It can be foreseen that the tire industry will maintain a robust growth trajectory in the future.

The reliance on nonrenewable resources such as petroleum-based rubbers and synthetic fibers in traditional tire manufacturing, coupled with greenhouse gas emissions and microplastic pollution during usage, has posed serious ecological and environmental challenges. , Data indicate that the automotive industry accounts for approximately 40% of global pollutant emissions, with tire lifecycle environmental impacts (encompassing raw material extraction, production, and usage wear) contributing 20–30% of this total. As the critical component directly contacting road surfaces, passenger tire tread compound systems remain highly dependent on traditional petroleum-based synthetic rubbers represented by functionalized solution-polymerized styrene–butadiene rubber and cis-polybutadiene rubber. These materials generate significant carbon footprints throughout their entire industrial chain, from fossil fuel extraction to synthesis, alongside high resource consumption.

To tackle the challenges of carbon emissions and unsustainable resource use, replacing traditional petroleum-based materials with biobased materials during tread manufacturing represents an effective strategy for carbon reduction in the tire industry. − Currently, a substantial amount of research has reported the use of epoxidized natural rubber, lignin, or cellulose as biobased materials in the development of tire tread materials. In addition, researchers worldwide have accelerated studies on biobased synthetic elastomers, focusing on developing biotechnological routes for key traditional olefin monomers − (e.g., butadiene and isoprene) to create next-generation sustainable tread material systems such as biobased cis-polybutadiene rubber and biobased styrene–butadiene rubber. As an important raw material for the sustainable development of synthetic rubber, biobased butadiene is mainly prepared through processes such as the catalytic conversion of biobased ethanol or the dehydration of biobased butanediol. However, constrained by bottlenecks in production costs and large-scale production, the current tire industry still mainly uses petroleum-based butadiene as the raw material. In response to the strategic orientation of carbon neutrality, companies such as Synthos Group S.A., Goodyear, and Michelin have already started to promote the industrialization projects of biobased butadiene. With the optimization of the technical routes and the increase in production capacity, this biobased butadiene is expected to gradually change the existing market pattern.

Diverging from conventional technical pathways, our research team has pioneered a new pathway in biobased synthetic rubber development through technological innovation, establishing differentiated competitive advantages in this emerging field. A biobased itaconate elastomer (BIE) , is a novel synthetic rubber derived from itaconic acid, which the U.S. Department of Energy has listed as one of the 12 most promising biobased chemicals. This material is synthesized via a two-step esterification-emulsion copolymerization process: first, itaconic acid is esterified with monohydric alcohols to prepare itaconate monomers, followed by emulsion copolymerization with butadiene to construct the elastomer molecular chains. The most distinct feature compared to traditional petroleum-based rubbers lies in the abundant pendant polar ester groups of BIE. These polar groups enable strong hydrogen bonding interactions between the raw rubber and “green filler” silica, thereby improving filler dispersion. To meet the performance requirements of tire tread materials, the research team has developed a series of products, including poly­(itaconate-co-isoprene), fully biobased poly­(diethyl itaconate-co-myrcene), and poly­(dibutyl itaconate-co-butadiene). By tailoring the side-chain alkyl length, comonomer type, and copolymerization ratio, molecular chain structures are systematically designed to promote the continuous improvement and iteration of itaconate elastomers. A kiloton-scale demonstration production line has been established based on these technological achievements, enabling stable production. However, despite extensive research on structural design and synthesis, the limited exploration of high-performance composite systems for itaconate elastomers has substantially restricted their engineering application development and potential to replace traditional petroleum-based rubbers.

In this study, we focus on analyzing the performance advantages of BIE materials and addressing existing challenges to develop high-performance green composites for tires. Comparative analysis between industrial BIE products and commercial SSBR revealed the contribution of the high friction-damping efficiency of ester groups to the material’s antislip performance. Additionally, the study identified that insufficient cross-link density in BIE composites led to inferior dynamic-static mechanical properties. To address this issue, a novel dual-network cross-linking strategy based on the synergistic effect of amino-functionalized polysulfide (PDAS) and sulfur was proposed. The influence of the PDAS dosage on cross-linking density, dynamic-static mechanical properties, and silica dispersion was systematically investigated. High-performance tire formulations validated the engineering application potential of BIE composites in the field of high-performance green tires.

2. Experimental Section

2.1. Materials

BIEs (BIE6600, BIE6610) were supplied by Shandong Chambroad Petrochemicals Co., Ltd. PDAS was supplied by the South China University of Technology. Solution-polymerized styrene–butadiene rubber (SSBR-A, SSBR-B) and all compounding ingredients were of industrial grade and obtained from the open market (Table S1).

2.2. Preparation of BIE/Silica and BIE/Silica-PDAS Composites

The experimental formulations were used to prepare the BIE/silica and BIE/silica-PDAS composites (Table ). For BIE/silica composites, BIE6600 or BIE6610 gum, zinc oxide, stearic acid, antioxidant, wax, silica, silica dispersant, and Si-75 were first blended in the Haake mixer. The Haake mixer was then heated to 150 °C, and the above mixture was processed for 5 min. The resulting compound was subsequently kneaded with an accelerator and sulfur on a two-roll mill, followed by compression molding in a hot press at 151 °C and 15 MPa to finalize the composite. The preparation of BIE/silica-PDAS composites followed the same procedure as that for BIE/silica composites, with PDAS incorporated during the two-roll mill compounding step.

1. Mixing Formulations of Itaconate Elastomer Composites.

ingredients content (phr)
raw rubber 100
silica100 65
silane coupling agent Si-75 5.2
silica dispersant 3
carbon black N330 5
stearic acid 2
antioxidant 4020 2
antioxidant RD 2
WAX100 2
zinc oxide 3
sulfur 1.7
accelerator CBS 1.7
accelerator D 1.65
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2.3. Characterization Methods

1H NMR spectra of BIE were performed on a Bruker AV400 spectrometer (Bruker, Germany) at 600 MHz using CDCl3 as the solvent. Molecular weights of BIE were characterized via gel permeation chromatography (GPC) using a Waters 515–717–2410 GPC System. Tetrahydrofuran (THF) was employed as the eluent at a flow rate of 1.0 mL/min. Glass transition temperature (T g) values of the BIE were determined using a DSC1 STARe system (Mettler-Toledo, Switzerland). The program was as follows: annealing at 80 °C for 5 min to erase thermal history, cooling to −60 °C at 10 °C/min, and reheating to 80 °C at 10 °C/min. In situ Fourier transform infrared spectra of BIE-PDAS were recorded with a Tensor II infrared spectrometer (Bruker, Germany). The optimum curing time and torque difference (M H – M L) of the BIE/silica and SSBR/silica were determined on a rotorless rheometer at 151 °C. The Payne effect of uncured BIE/silica and SSBR/silica compounds were performed on a D-RPA 3000 rheometer (MonTech, Buchen, Germany) at 0.83 Hz and 80 °C. Mechanical properties of BIE/silica and SSBR/silica were tested at a stretch rate of 500 mm/min according to GB/T528–2009 by an electronic tensile tester (ZWICK, Germany) The dynamic mechanical properties of BIE/silica and SSBR/silica were characterized using a VA3000 DMTA (Metravib, France), with test parameters set as follows: temperature range −60 to 80 °C, heating rate 3.0 °C/min, static strain 5%, dynamic strain 0.2%, and frequency 10.0 Hz. The friction coefficients of BIE/silica and SSBR/silica were measured using a British Pendulum Skid–Resistance Tester (BPST) and Laboratory-Abrasion-Tester (LAT-100). Morphologies of BIE/silica and SSBR/silica were observed using a Multimode 8 atomic force microscope (AFM, Bruker, Germany) with the sample surface polished prior to testing.

3. Results and Discussion

3.1. Performance Comparison of Two Industrial BIE Products

BIE demonstrate distinct advantages over traditional petroleum-based synthetic rubbers through the flexible designability of their side-chain structures. Leveraging this feature, Shandong Jingbo Zhongju New Materials Co., Ltd. has successfully achieved large-scale production of two BIE, poly­(diethyl itaconate-co-butadiene) (BIE6610) and poly­(dibutyl itaconate-co-butadiene) (BIE6600)-via emulsion copolymerization of diethyl itaconate or dibutyl itaconate with butadiene. The corresponding raw rubber blocks are presented in Figure a. This study systematically investigated how side-chain length variations in these elastomers influence composite material properties, including mechanical performance, processing characteristics, and dynamic mechanical behaviors.

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(a) Two industrial itaconate elastomers BIE6610 and BIE6600, (b) 1H NMR spectra, (c) DSC curves.

The microstructures and copolymer compositions of the two industrial itaconate elastomers were characterized using 1H NMR spectra (Figure b). All proton chemical shifts in the spectra corresponded well to the respective monomer units in both elastomers, with the identical portions between both materials arising from different configurations of butadiene units. For the diethyl itaconate units, characteristic proton signals appeared at 4.04, 2.52, and 1.17 ppm. Dibutyl itaconate units exhibited distinct chemical shifts at 3.98, 2.54, and 0.87 ppm. The butadiene segments showed typical resonances for trans-1,4-structures (5.33 ppm), cis-1,4-structures (5.24 ppm), and 1,2-vinyl structures (4.89 ppm). Mestrenova NMR analysis software was employed to integrate peak areas corresponding to these proton signals, enabling determination of the actual molar ratios of copolymer components, which are presented in Table . BIE6610 elastomer contained 31.1 mol % diethyl itaconate units with butadiene segment composition of 44.0 mol % trans-1,4 structure, 17.9 mol % cis-1,4 structure, and 7.0 mol % 1,2-vinyl structure. The BIE6600 elastomer showed 25.7 mol % dibutyl itaconate units and butadiene segment composition of 51.6 mol % trans-1,4 structure, 14.6 mol % cis-1,4 structure, and 8.1 mol % 1,2-vinyl structure. In comparison, BIE6600 exhibited a lower itaconate molar fraction and a higher butadiene molar fraction, with its butadiene segments predominantly consisting of trans-1,4-configurations.

2. Copolymerization Compositions of BIE6610 and BIE6600.

    different configurations of butadiene
samples itaconate unit mol % (wt %) trans-mol % (wt %) cis-mol % (wt %) vinyl mol % (wt %)
BIE6610 31.1 (60.9) 44.0 (25.0) 17.9 (10.1) 7.0 (4.0)
BIE6600 25.7 (60.8) 51.6 (27.2) 14.6 (7.7) 8.1 (4.3)
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Differential scanning calorimetry (DSC) analysis was used to investigate the effect of the side-chain length on the glass transition temperature (T g) of two industrial itaconate elastomers. As shown in Figure c, BIE6610 and BIE6600 exhibited T g values of −52.7 and −36.8 °C, respectively, both below ambient temperature, which endows these copolymers with excellent elasticity and ductility during practical applications. Notably, BIE6610 showed a 16 °C higher T g than BIE6600, attributed to the longer alkyl chain length of dibutyl itaconate enhancing segmental mobility compared to diethyl itaconate combined with the elevated actual molar fraction of butadiene units in BIE6600. Additionally, no crystalline peaks were observed between −80 and 80 °C, confirming the amorphous state of both industrial itaconate elastomers.

As indicated in Table , both industrial itaconate elastomers exhibited number-average molecular weights (M n) exceeding 250,000 g/mol with polydispersity indices (D̵) of 3.0 and 3.5, consistent with the high-molecular weight and broad distribution characteristics typical of emulsion polymerization products. It is well-established that high conversion rates often lead to severe gel formation, negatively affecting subsequent material properties. For example, styrene–butadiene rubber (SBR) typically requires conversion control between 60 and 70% to achieve optimal performance. Remarkably, BIE6610 and BIE6600 achieved yields exceeding 90% with gel contents below 2%. This “high-conversion-low-gel” phenomenon arises because the butadiene content in these itaconate elastomers is substantially lower than that in SBR, effectively minimizing branching or cross-linking during polymerization. Overall, BIE6610 and BIE6600 with high molecular weight and low gel content ensured excellent processability, sufficient mechanical properties, and elasticity after curing.

3. Molecular Weight, Gel Content, and Yield of BIE6610 and BIE6600.

sample Mn (104) Mw (104) D̵ yield (%) gel content (%)
BIE6610 25.1 86.8 3.5 94 1.8
BIE6600 29.3 86.8 3.0 92 1.5
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For amorphous elastomers, practical utility can only be achieved through nanoreinforcement and the formation of three-dimensional network structures. Silica was employed as the reinforcing agent and sulfur as the cross-linking agent to prepare BIE/silica, with SSBR/silica prepared under identical formulations for performance comparison. Rotorless cure meter analysis was first conducted to characterize the vulcanization properties of BIE6600/silica, BIE6610/silica, SSBR-A/silica, and SSBR-B/silica, as presented in Table . The shorter optimal curing time (T 90) observed in BIE6610/silica compared to that in BIE6600/silica is attributed to the following reason: the polar diethyl ester groups in BIE6610 form stronger hydrogen bonds with silica surface silanols (Si–OH), effectively reducing accelerator adsorption on the filler surface, thereby enhancing the vulcanization rate. Torque difference (M H – M L) serves as an indicator of the relative cross-linking density in the rubber industry. As shown in Figure a, BIE6600/silica demonstrated lower torque difference than BIE6610/silica due to steric hindrance from dibutyl itaconate’s long side chains masking some butadiene double bonds, leading to reduced cross-linking density. Both BIE6600/silica and BIE6610/silica exhibited lower torque differences compared to SSBR-A/silica and SSBR-B/silica, attributed to significantly higher butadiene content in the SSBR molecular chains. Lower cross-linking density of BIE/silica negatively impacts both the dynamic and static mechanical properties of the composites.

4. Comparison of Vulcanization Characteristic, Static, and Dynamic Mechanical Properties between BIE/Silica and SSBR/Silica.

sample BIE6600/silica BIE6610/silica SSBR-A/silica SSBR-B/silica
T10/min 8:59 7:39 7:04 9:42
T90/min 22:38 20:47 17:15 22:45
MH – M L/dN·m 7.4 9.2 11.1 10.3
σ/MPa 12.3 ± 0.3 11.1 ± 0.4 16.2 ± 0.5 13.4 ± 0.3
σε=300%/MPa 6.4 ± 0.2 7.5 ± 0.2 12.0 ± 0.3 10.4 ± 0.2
ε/% 494 ± 15 411 ± 12 372 ± 20 363 ± 15
0 °C tan δ 0.479 0.718 0.269 0.562
25 °C tan δ 0.226 0.342 0.110 0.140
60 °C tan δ 0.114 0.151 0.061 0.071
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(a) Torque difference M H – M L, (b) stress–strain curves, (c) storage modulus–temperature curves, (d) tan δ-temperature curves of BIE/silica and SSBR/silica.

Rubber products, particularly tire materials, are subjected to enormous external forces during service. Therefore, the mechanical properties of composite materials are critical indicators of their application potential. Figure b presents the stress–strain curves of BIE/silica and SSBR/silica composites. The BIE6600/silica composite exhibited a tensile strength of 12.3 MPa and an elongation at break of 494%, while BIE6610/silica showed 11.1 MPa tensile strength and 411% elongation at break. By contrast, SSBR/silica demonstrated higher tensile strength and modulus (at specific elongations), along with lower elongation at break. This discrepancy is attributed to the higher cross-linking density of SSBR/silica compared to BIE/silica composites. Additionally, the bis-ester groups in BIE/silica impede molecular chain orientation and slippage during deformation. To meet the mechanical requirements of tire materials, it is essential to enhance the cross-linking density of BIE/silica composites to improve their tensile strength and modulus.

Dynamic mechanical analysis (DMA) plays a critical role in evaluating the performance of rubber compounds for tire tread applications. In the rubber industry, the temperature-dependent loss tangent (tan δ) reveals key functional characteristics: the tan δ value at 0 °C, 25 °C, and 60 °C predicts wet skid resistance, dry braking performance, and rolling resistance, respectively. , As shown in Figure c,d and Table , BIE6600/silica, BIE6610/silica, SSBR-A/silica, and SSBR-B/silica vulcanizates exhibited comparable initial storage moduli, with glass transition temperatures (T g) of −26.0 °C, −10.1 °C, −28.1 °C, and −14.1 °C. Compared to SSBR/silica composites at equivalent T g, BIE/silica demonstrated significantly higher tan δ values at 0 and 25 °C, indicating superior wet skid resistance and dry braking performance, advantageous traits for driving safety. This enhancement stemmed from the presence of bis-ester branches in BIE’s molecular chains, which increased frictional interactions between polymer chains and between chains and fillers, thereby elevating tan δ. However, tire materials require balancing wet skid resistance, dry braking performance, and rolling resistance. Therefore, BIE6600/silica better aligns with the dynamic performance requirements for tire materials. However, compared with SSBR/silica, BIE6600/silica still exhibited a higher tan δ value at 60 °C, corresponding to elevated rolling resistance. This limitation is attributed to its relatively low cross-linking density. Consequently, there is an urgent need to develop cross-linking enhancement strategies tailored for BIE6600 systems to simultaneously improve both dynamic and static mechanical properties.

To clarify the contribution of BIE6600/silica side ester groups to antislip, we further quantified the friction coefficients of BIE/silica composites with varying filler loadings using a BPST (Figure a) and Laboratory-Abrasion-Tester (LAT-100, Figure c). For intuitive evaluation, SSBR-A/silica composites were prepared under compounding formulations and processing conditions identical to those of control samples. As shown in Figure b,d, BIE6600/silica consistently exhibited significantly higher friction coefficients than SSBR-A/silica across all filler loadings, with the highest value achieved at 75 phr silica reinforcementa filler fraction closely aligned with commercial tire formulations. The reason can be attributed to the higher frictional damping efficiency of the ester groups in BIE6600 compared to styrene and vinyl groups in SSBR, which contributes to the improvement of the friction coefficient. These results demonstrate that BIE6600/silica composites have the potential to achieve superior traction performance when used as tire tread materials.

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(a) BPST sample test images, (b) BPST friction coefficient, (c) LAT-100 sample test images, (d) LAT-100 friction coefficient.

3.2. Fabrication of Dual-Cross-Linked System of BIE/Silica

Sulfur vulcanization systems remain the dominant cross-linking approach for tire tread materials, imparting excellent dynamic and static mechanical properties through the formation of polysulfidic (-Sx-) cross-link networks. However, simply increasing the sulfur content to enhance cross-linking density often leads to blooming issues that compromise material performance. To address the insufficient cross-linking density challenge in BIE6600/silica systems, this study proposes a synergistic dual-cross-linked network strategy leveraging the structural characteristics of BIE6600s double bonds and bis-ester groups. By retaining sulfur’s cross-linking action on unsaturated double bonds while simultaneously activating bis-ester sites through a novel covulcanizing agent, thereby achieving the enhancement of cross-linking density.

As shown in Figure a, the dual cross-linking network was constructed by combining sulfur with amino-functionalized polysulfide (PDAS) synthesized via antivulcanization of sulfur and m-phenylenediamine, enabling efficient vulcanization of BIE6600/silica. To verify the amine–ester reaction between BIE6600 and PDAS, a mixture containing only BIE6600 and PDAS was blended using an open mill and vulcanized at 151 °C. The emerging peak at 1550 cm–1 corresponding to δN–H bending (amide II band) indicated that the amine groups of PDAS have reacted with the ester groups of BIE6600 to form a cross-linking network (Figure b). In situ FTIR monitoring dynamically tracked the vulcanization progression, demonstrating continuous attenuation of ester group absorption intensity at 1736 cm–1 with concomitant increase in the amide bond signal at 1550 cm–1(Figure c), which confirmed the correlation between the aminolysis reaction process and cross-linking network development.

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(a) Schematic for the amine–ester reaction by BIE6600 and PDAS, (b) FTIR spectra of uncured and cured BIE6600/PDAS, (c) in situ FTIR spectra of the curing process at 151 °C.

The Payne effect in rubber composites manifests as a nonlinear decrease in storage modulus (G′) with increasing shear strain, where the filler network strength can be characterized by ΔG′ (G 0′ – G ∞′). As shown in Figure a, the G′ values of all BIE/silica-PDAS systems continuously decreased with increasing shear strain and eventually converged, indicating that the filler network gradually dissociates under shear. The ΔG′ values for systems with different PDAS loadings were 426.3, 418.5, 404.4, 389.9, and 388.7 kPa, respectively, demonstrating a significant attenuation of filler network strength with increasing PDAS content. Analysis indicated that residual amine groups in PDAS and reaction-generated amide groups promote homogenization of silica dispersion through hydrogen bonding interactions with silica surfaces, thereby reducing filler network density and leading to a decreased initial storage modulus.

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(a) G′-strain curves of rubber compound, (b) torque difference M H – M L, (c) stress–strain curves, (d) tan δ-temperature curves of BIE6600/silica with different PDAS.

Subsequently, the effect of PDAS content on the vulcanization properties of BIE6600/silica composites was investigated with vulcanization characteristic parameters presented in Table . The introduction of PDAS decelerated vulcanization rate, primarily originating from the longer dynamic equilibrium time required for synergistic construction of sulfur-cross-linked networks and amidation-derived networks. Concurrently, the progressive increase in torque difference (Figure b) with the PDAS content increment confirmed effectively enhanced cross-linking density through synergistic construction of dual cross-linking networks.

5. Vulcanization Characteristic, Static, and Dynamic Mechanical Properties of BIE/Silica with Different PDAS.

sample 0 PDAS 0.3 PDAS 0.6 PDAS 0.9 PDAS 1.2 PDAS
T10/min 6:30 6:38 6:19 6:05 6:05
T90/min 15:41 17:36 17:54 19:12 19:50
MH – M L/dN·m 7.6 8.1 8.4 8.9 9.3
σ/MPa 12.1 ± 0.2 12.3 ± 0.2 12.3 ± 0.5 13.1 ± 0.3 13.7 ± 0.2
σε=300%/MPa 6.8 ± 0.3 6.9 ± 0.2 7.5 ± 0.4 8.2 ± 0.2 8.1 ± 0.1
ε/% 482 ± 12 476 ± 18 452 ± 10 449 ± 26 474 ± 9
Tg /°C –26.0 –26.1 –26.1 –25.9 –23.9
0 °C tan δ 0.409 0.409 0.410 0.403 0.444
25 °C tan δ 0.219 0.209 0.217 0.206 0.225
60 °C tan δ 0.116 0.113 0.114 0.107 0.106
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The mechanical properties of BIE6600/silica composites with varying PDAS contents were systematically evaluated with stress–strain curves, and detailed data are presented in Figure c and Table . The tensile strength of BIE6600/silica ranged from 12.1 to 13.7 MPa, while the elongation at break maintained values between 449% and 482%. A progressive increase in tensile strength and 300% modulus was observed with higher PDAS loading, indicating that the formation of sulfur-amide dual-cross-linked networks effectively enhanced the mechanical performance of BIE6600/silica composites.

From the perspective of dynamic mechanical properties (Figure d), the T g of the BIE6600/silica ranged from −26.1 to −23.9 °C, demonstrating a slight upward trend with increasing PDAS loading. When the PDAS content was below 0.9 phr, the tan δ value at 0 °C remained approximately 0.41. Notably, increasing PDAS loading to 1.2 phr led to a significant increase of tan δ at 0 °C to 0.444, signifying enhanced wet skid resistance attributed to the synergistic formation of dual-cross-linked networks at higher PDAS concentrations. Meanwhile, tan δ values at 60 °C exhibited a decreasing trend with increasing PDAS content, suggesting that enhanced cross-linking density restricted macromolecular chain mobility, thereby reducing frictional losses and improving rolling resistance, a desirable characteristic for green tire tread applications.

Furthermore, atomic force microscopy (AFM) was employed to characterize the morphology of the BIE6600/silica composites. AFM images of the samples with various PDAS contents are presented in Figure . Regions with high moduli appear blue, corresponding to the silica particles, while regions with low moduli appear yellow, representing the continuous BIE matrix. With increasing PDAS content, the dispersion homogeneity of silica particles was significantly optimized, particularly evident in the reduction of micrometer-scale aggregates.

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AFM LogDMT modulus images of BIE6600/silica with different PDASs.

3.3. Comparison between BIE6600-PDAS and SSBR in High-Performance Tire Formulations

Building upon the aforementioned work, to accurately evaluate the potential of BIE6600 as a replacement for SSBR in green tire manufacturing, industrial high-performance tire formulations (Table S2) were selected to prepare SSBR and BIE composites designated as HT158 and P2HT200-PDAS, respectively. A comprehensive comparative analysis was conducted on their vulcanization characteristics, Payne effect, mechanical properties, abrasion resistance, dynamic mechanical performance, and filler dispersion.

As shown in Figure a, the torque difference of P2HT200-PDAS prepared with a high-performance tire formulation was slightly higher than that of HT158, confirming that the dual cross-linking network effectively addressed the cross-linking efficiency issue caused by insufficient double bond density in BIE molecular chains. From Figure b, the weaker Payne effect of P2HT200-PDAS indicated that the hydrogen bonding interaction between BIE6600-PDAS and silica contributed to improving filler dispersion and imparting superior processing properties. In terms of mechanical properties, P2HT200-PDAS exhibited higher tensile strength, modulus at 300%, and elongation at break compared with HT158 (Figure c). The DMA comparison between HT158 and P2HT200-PDAS revealed that P2HT200-PDAS had a higher tan δ at 0 °C, signifying better wet skid resistance. Although its tan δ at 60 °C was slightly elevated, it remained below 0.1, meeting the dynamic mechanical requirements for tread rubber applications (Figure e,f). The AFM images showed that P2HT200-PDAS achieved better silica dispersion (Figure g), consistent with the Payne effect results. From Figure h, the composite material prepared with BIE6600-PDAS demonstrated significant advantages in filler dispersion and wet skid resistance while maintaining comparable mechanical properties and abrasion resistance. However, further optimization of rolling resistance is still required to meet high -performance green tire standards. Thus, BIE6600-PDAS may be promising for biobased tire tread material as a supplement to petroleum-based SSBR.

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(a) Vulcanization curves, (b) G′-strain curves of rubber compound, (c) stress–strain curves, (d) Akron abrasion test results, (e) tan δ-temperature curves, (f) value of 0 °C tan δ and 60 °C tan δ, (g) AFM LogDMT modulus images, (h) comparison of the comprehensive properties of the high-performance tire formulations based on BIE-PDAS and SSBR.

4. Conclusions

In summary, this study conducted performance comparisons between two industrial-grade BIE6610, BIE6600 and commercial SSBR, identifying BIE6600 as a promising candidate for green tire tread applications. BPST and LAT-100 friction tests demonstrated superior frictional coefficients in BIE6600/silica, attributed to the high damping efficiency of pendant ester groups, which enhance tire safety during driving. To address the technical bottleneck of low cross-linking density in BIE6600/silica, an innovative sulfur/PDAS synergistic cross-linking system was developed. This system achieved dual-network construction through activated double bond vulcanization and ester group aminolysis reactions, significantly improving the cross-linking density and dynamic/static mechanical properties. Additionally, residual amine groups in PDAS and amide bonds formed via amine-esterification established hydrogen bonding interactions with silica, promoting filler dispersion. Validation with high-performance tire formulations demonstrated balanced performance in BIE6600/silica systems compared with SSBR/silica: comparable cross-linking density and Akron abrasion resistance were achieved alongside improvements in tensile strength (17.4 MPa, a 4.2% increase) and elongation at break (422%, an 8.2% increase). Notably, wet skid resistance of BIE6600/silica (tan δ = 0.744 at 0 °C) showed a 36.5% enhancement over the SSBR/silica (tan δ = 0.545 at 0 °C). This research provides a technical pathway for BIE in green tire applications and opens up new avenues for designing ester copolymer cross-linking systems through dual-network synergistic reinforcement strategies.

Supplementary Material

ao5c02670_si_001.pdf (86.3KB, pdf)

Acknowledgments

The work was supported by the National Key Research and Development Program of China (2022YFC2104700) and the National Natural Science Foundation of China (51988102, 51503010). The authors thank for the support of Shandong Linglong Tyre Co., Ltd.

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsomega.5c02670.

  • Mixing formulations of itaconate elastomer composites and compound formulation of HT158 and P2HT200-PDAS (PDF)

Conceptualization, Liqun Zhang; supervision, Wencai Wang and Runguo Wang; formal analysis, Yanguo Li and Haijun Ji; investigation, Yanguo Li, Hui Yang, and Jing Xu; writingoriginal draft, Yanguo Li and Haijun Ji; and writingreview and editing, Wencai Wang and Runguo Wang.

The authors declare no competing financial interest.

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Associated Data

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Supplementary Materials

ao5c02670_si_001.pdf (86.3KB, pdf)

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