Second Natural Rubber with Self-Reinforcing Effect Based on Strain-Induced Crystallization

Abstract

Natural rubber (NR) has a strategic position in the rubber industry due to its excellent properties, but it faces the problem of insufficient output and difficulty in recycling. Here, a high-performance elastomer was prepared by the simple epoxidation modification of bio-based Eucommia ulmoides gum (EUG). For the first time, it was found that epoxidized EUG (EEUG) with an epoxy degree of 12.3%−17.4% no longer crystallized at room temperature but had the ability to strain-induced crystallization (SIC). As a result, its vulcanizates showed excellent tensile strength (17 MPa), toughness (37.8 MJ m −3 ), and elasticity (strain recovery values >97%) without filler reinforcement, which is comparable with vulcanized NR. The SIC of EEUG was studied by synchrotron radiation wide-angle X-ray diffraction (SR-WAXD), and its performance was also compared with NR under the reinforcement of carbon black. In addition, through cross-linking by disulfide bonds, EEUG could be used to prepare highperformance (tensile strength of 10.5 MPa, toughness of 30.7 MJ m −3 ), recyclable green elastomers. This new kind of elastomer can be used as the second natural rubber, which is of great significance to solve the problem of insufficient production and difficult recovery of NR.

Bioinspired Sustainable Polymer with Stereochemistry-Controllable Thermomechanical Properties

“…Its SIC capability was verified by the appearance of diffraction arcs at a 2D WAXD pattern when the sample was stretched to 600% (Figure 5d). This is consistent with our previous study about epoxidized EUG, 18 that is, the proper molecular chain regularity can enable EUG to have the same SIC capability as NR. In the stretched state, the molecular chains are oriented along the stretched direction.…”

“…In addition, the loss factor (tan δ) measured by DMA can be used to predict tire performance. The tan δ value at 60 °C represents the rolling resistance, and the tan δ value at 0 °C represents the wet-skid resistance . The tan δ values of F-IEUG-10.7%-S-1 at 0 and 60 °C are 0.15 and 0.13, while the values of F-NR-S-1 are 0.18 and 0.165, respectively (Figure d).…”

“…EUG and NR possess different properties that are dependent on stereochemistry. Since the higher regularity in trans -configuration, EUG crystallizes quickly at room temperature. − Meanwhile, NR is amorphous, soft, flexible, and elastic. , Based on stereochemistry, we hypothesized that if the cis : trans ratios of EUG could be regulated, new materials with different thermomechanical properties could be prepared, even new elastomers with properties comparable to NR. To modulate the cis : trans ratios, Cunneen et al , attempted to isomerize NR and EUG with sulfur dioxide or thiol acid, but the isomerization process is difficult to control, resulting in poor mechanical properties.…”

Achieving high elasticity of trans-1,4-polyisoprene with a combination of radiation crosslinking and thiol–ene grafting

“…10b and d, where the strain recovery increases with the reaction time. The strain recovery of g-xTPI was about 90%, which is a relatively high value compared to other elastomers such as olefin block copolymers (OBCs, ∼75%) 50 and polybutadiene elastomer (∼87%), 34 and is close to styrene–butadiene rubber (∼92%), 59 natural rubber (∼94%) 60–62 and polyolefin elastomers (POEs, ∼92%). 63 However, the tensile recovery of the sample shows a slight decrease, from 90% to 87%, when the reaction time was increased from 2 to 4 h. According to Carstensen, 64 this may suggest that the UV reaction caused the degradation of xTPI, causing a decrease in strain recovery.…”

On the influence of the amorphous phase on the stability of crystals in poly(cis‐1,4‐isoprene) networks

“…Crystals in natural rubber (NR) networks are a good example of this polymer‐typical characteristic, 5 because they form at room temperature only under strain but spontaneously melt when the stretching force is released and the rubber retracts back to its original dimensions. This phenomenon, referred to as strain‐induced crystallization (SIC), is intensively studied since its discovery in the 1920s, because it is assumed to be responsible for the outstanding high tensile strength of NR at high elongations 6–19 …”