Explore the vast range of titles available.

Polyurethane (PU) is one of the most commonly used plastics, typically synthesized from diisocyanates and polyols derived from non‐renewable or unsustainable sources. This study proposes a synthesis route for polyurethanes that originates from bio‐based polyols. The polyols were obtained through the metathesis depolymerization of butadiene rubber using fatty alcohol and Hoveyda‐Grubbs second‐generation catalyst (HG2), resulting in hydroxyl‐terminated polybutadiene (HTPB). FT‐IR and GPC analyses confirmed the successful synthesis of polyols, indicating molecular weights between 535 and 2200 g/mol. Three polyurethanes (PU1, PU2, and PU3) were synthesized using these bio‐based polyols, while a fourth polyurethane (PU0) was produced with polyethylene glycol as a standard polyol for comparative property analysis. FT‐IR analysis identified the characteristic signals and functional groups of the polyurethanes. TGA and DSC evaluated the thermal properties of the polyurethanes, revealing decomposition temperatures (Tmax) between 300 and 450°C. PU materials were practically amorphous, as shown by XRD. SEM micrographs illustrated the varying morphologies of the polyurethanes, providing deeper insights into their properties. This synthesis process is vital for recycling rubber waste, transforming it into hydroxy‐terminated compounds, HTPB, or polyols using vegetable oils and renewable resources. When integrated into PU synthesis, these compounds promote the development of sustainable materials and significantly contribute to environmental conservation and the sustainable production of adhesives, paints, and coatings, among other valuable products. This study proposes a synthesis route for polyurethanes (PUs) derived from bio‐based polyols. The polyols were obtained through metathesis depolymerization of butadiene rubber using fatty alcohol (a castor oil derivative) as a chain transfer agent to produce hydroxyl‐terminated polybutadiene (HTPB). These bio‐based PUs show promise for designing sustainable polymers and materials for various applications, including foams, coatings, adhesives, the automotive sector, and biomedical uses.

Core–shell polybutadiene‐graft‐polystyrene (PB‐g‐PS) graft copolymers with different ratios of PB to PS are synthesized by emulsion polymerization. Further, the PB‐g‐PS copolymers are blended with polypheylene ether (PPE) and PS to prepare PPE/PS/PB‐g‐PS blends. The effects of PB‐g‐PS copolymer structure and matrix composition on the morphological, mechanical properties, and deformation mechanism of the blends are studied. The results show that the synthesized submicrometer‐sized PB‐g‐PS copolymer has an excellent toughening efficiency, both the copolymer and PS are introduced into PPE resin to produce a ternary blend which is combined with high toughness and processing properties. The optimum toughening effect on PPE/PS matrix is observed at the core–shell weight ratio of 70/30 in PB‐g‐PS copolymer, and the impact strength of the blends increased from 101 to 550 J m−1. In addition, the dispersion pattern of rubber particles in the matrix gradually changes from uniform dispersion to aggregation as the core–shell ratio of PB‐g‐PS copolymers increases. On the other hand, with the increase of PPE content, the dispersion of rubber particles in PPE/PS matrix is improved, and the deformation mechanism is changed from cracking to a combination of crazing and shear yielding, which can lead to absorb more energy to achieve better toughness. The polybutadiene‐graft‐polystyrene (PB‐g‐PS) graft copolymers with different ratios of PB to PS are blended with polypheylene ether (PPE) and PS to prepare PPE/PS/PB‐g‐PS blends. It is found that the synthesized submicrometer‐sized PB‐g‐PS copolymer at the core–shell weight ratio of 70/30 has an excellent toughening efficiency, and the deformation mechanism of the blend is a combination of crazing and shears yielding.

We present linear viscoelastic data with anionically synthesized and critically fractionated polybutadiene (rich in vinyl content) rings having about Z  = 22 entanglements. These rings are experimentally as pure as currently possible. They exhibit a power-law stress relaxation G(t) that is well-described by the state-of-the-art fractal loopy globule (FLG) model (power-law exponent of − 3/7). Previously reported data with polystyrene rings, prepared by anionic synthesis in dilute solution and purified by liquid chromatography at the critical condition, having Z  = 14 entanglements, showed a power-law G (t) as well. Recent developments with different synthetic methods yielding not so well-characterized rings with a very large number of entanglements (up to 300), suggest that a rubbery plateau emerges in the linear viscoelastic response for Z  > 15. Our work confirms the power-law G (t) with the FLG exponent with another chemistry and contributes to the current discussion about different regimes of rheological behavior, indicating that a possible deviation from the power-law FLG type of behavior toward rubbery plateau may occur for Z > 22. To fully capture the experimental G (t) data, the FLG model is complemented by two additional relaxation modes which are attributed to ring-ring (RR) and ring-linear (RL) threading, in accordance with recent reports in the literature. The faster RR mode likely reflects a new mechanism of stress relaxation not described by FLG, and the slower RL mode is attributed to synthetic and material handling imperfections (for example, due to thermal treatment). However, it does not change the punchline of the work: no rubbery plateau for entangled rings with up to 22 entanglements. Graphical Abstract Stress relaxation modulus for entangled ring polybutadiene (exhibiting power-law decay) and its linear precursor (exhibiting rubbery plateau), along with fits to the data: tube model for linear chains, and fractal loopy globule (FLG) with slow modes (RR and Tsalikis et al.) for the ring.

Traditional crosslinked diene rubber has excellent thermal–mechanical properties and solvent resistance, yet it is incapable of being recycled via universal molding or injecting. Vitrimers, a new class of covalently crosslinked polymer networks, can be topologically rearranged with the associative exchange mechanism, endowing them with thermoplasticity. Introducing the concept of vitrimers into crosslinked networks for the recycling of rubbers is currently an attractive research topic. However, designing tailored rubber vitrimers still remains a challenge. Herein, polybutadiene (PB) vitrimers with different structures were prepared via partial epoxidation of double bonds and ring-opening esterification reactions. Their mechanical and relaxation properties were investigated. It was found that the increasing crosslinking density can increase tensile strength and activation energy for altering the network topology. The influence of side-group effects on their relaxation properties shows that an increase in the number of epoxy groups on the polybutadiene chain can increase the chance of an effective exchange of disulfide units. This work provides a simple network design which can tune vitrimer properties via altering the crosslinking density and side-group effects.

Dynamic cross-linked networks (DCNs) endow thermoset rubber with self-healability and recyclability to extend its lifetime and alleviate environmental pollution. However, the contradiction between high self-healing and mechanical properties in DCNs rubber is always difficult to be resolved. Herein, we used boronic ester (BO) and Diels-Alder dynamic covalent bonds (DA) to synthesize polybutadiene-based dual networks rubber (PB-BO-DA) via thiol-ene reaction. This approach achieved a tensile strength of 16.46 MPa and 99% self-healing efficiency, facilitated by extensive intermolecular interactions (π-π packing and N-B coordination) and fully dynamic cross-linking. In addition, multiple dynamic cross-linked networks (MDCNs) polybutadiene-based rubber also show excellent shape memory ability and recyclability. This strategy might open a helpful pathway to fabricate intelligent multifunctional polymers with high strength and high self-healing efficiency.

Solvent processing hampers the reliability and energy density of self-healing binders for energetic materials. We report a solvent-free curing route for a Diels–Alder self-healing furanyl-terminated polybutadiene enabled by a functional external plasticizer, dibutyl phthalate (DBP), which acts not only to lower the viscosity of the binder but to disperse the high-melting bismaleimide, thereby driving crosslinked network formation. The 50 wt% DBP-plasticized film healed a pre-cut crack in 5 min at 120 °C and recovered nearly full mechanical properties after 24 h at 60 °C. Based on this binder system, a self-healing solid propellant with 80 wt% solid content was solvent-free cast into a dense and void-free grain that healed surface cracks within 5 min at 120 °C. This solvent-free approach overcomes the limitations of solvent-based processing and offers a viable fabrication route for self-healing energetic materials.

Most acrylate adhesives do not bond well to low-surface-energy substrates (e.g., polyethylene and polypropylene) due to the weak interaction force between the polar adhesive molecules and the substrate. To enhance the adhesion performance on low-surface-energy substrates and investigate the effects of substrate surface energy, roughness, pressure-sensitive adhesive (PSA) surface energy, viscosity, and modulus on adhesion performance, this study modifies the acrylate adhesive by incorporating a hydrogenated-terminated hydroxylated polybutadiene (HHTPB) structure with a double bond at one end. The results demonstrate an enhancement in the adhesion performance of the modified PSAs on High-Density Polyethylene (HDPE). The 24 h peel strength and loop tack increase to 4.88 N/25 mm and 8.14 N/25 mm at 20 °C, respectively, with the failure modes remaining adhesive failure. However, as the temperature increases, the peel strength decreases. The high-temperature resistance of the adhesive improves. Based on the experimental data, a mathematical model is proposed that incorporates both the wetting area and loss factor to predict peel strength. The influence of these two factors on the peel strength of the PSA is dependent on the application temperature of the adhesive.

The rheological properties of polymers before and after mixing are of primary concern because of the damage to the original molecular weight of polymers during processing. In order to reveal the correlation between mixing speed, rheological properties of polymer melts, and their molecular weight parameters, different grades of polybutadiene rubber (BR) at different mixing speeds were prepared in this study. Furthermore, the selected samples were subjected to the dynamic melt viscoelasticity test using a rubber process analyzer (RPA). The molecular weight changes of BR after mixing were observed on a rheological basis to analyze the effects of mechanical shear and thermo-oxidative aging on the molecular weight and distribution of the rubber. The measured values were directly compared with those obtained from gel permeation chromatography (GPC). The results showed that lower mixing speeds did not significantly affect the number-mean molecular weight (Mn), while the Z-mean molecular weight (Mz) and the weight-mean molecular weight (Mw) were increased, and the molecular weight distribution (MWD) was expanded. In addition, a transition state between thermo-oxidative aging and mechanical shear was further demonstrated. The behavior of the rubber was further elucidated and validated through large-amplitude oscillatory shear (LAOS) tests and thermal stability tests, demonstrating that the gel is a manifestation of the molecular weight coalescence of rubber and associating it with the mixing process of BR. According to the results of the RPA tests, melt rheology characterization is an environmentally friendly and fast way to provide information about the molecular structure of the BR.

In recent years, click chemistry has shown significant potential in the design and performance optimization of polymers for solid propellants, owing to its high efficiency, modularity, and superior selectivity. In the field of solid propellants, click chemistry provides innovative strategies for the development of high-performance binders, reactive plasticizers, new cross-linking curing modes, and controllably functionalized polymers, which play a significant role in enhancing the energy level of solid propellants, optimizing the production process, and enhancing mechanical properties. This paper focuses on three click chemistry reactions—the azide-alkyne cycloaddition, the thiol-ene reaction, and the nitrile oxide-alkyne cycloaddition—and their applications in solid propellant systems based on azide polymers, hydroxy-terminated polybutadiene, polyethers, and other binders. Despite promising prospects, practical implementation remains challenged by critical issues such as scalability, metal catalyst residues, or energetic group compatibility. Future research should aim to address these bottlenecks to enable a transition from laboratory-scale investigations to large-scale engineered applications, ultimately establishing click chemistry as a complementary technology to conventional polymer binder systems. Such advancement will provide crucial pathways for innovation in solid propellant technology. [Display omitted] •A review of click chemistry was carried out focusing on its research progress in polymers for solid propellants.•The click chemistry covered in this review consists of three main types, azide-alkyne cycloaddition reactions, nitrile oxygen-alkyne cycloaddition reactions, and mercapto-alkyne click reactions.•Elucidating the structure–property relationships among group characteristics, click chemistry types, and application performance for distinct solid propellant systems (azido-, HTPB-based, and polyether-type binders).

This research aims to enhance the mechanical characteristics of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) by using epoxidized natural rubber (ENR-25 and ENR-50) as a toughening agent and polybutadiene (PB) grafted with maleic anhydride (MA) (3 MA groups/chain) as a compatibilizer. The PHBV/ENR blends were mixed in 100/0, 90/10, 80/20, and 70/30 with PB- g -MA at 0, 5, and 10% (wt./wt.), using an internal mixer set to 175 °C with a rotor speed of 50 rpm. The findings indicated that at 70/30 PHBV/ENR composition, the impact strength of the blends with 25 and 50 epoxide contents were the greatest at 6.92 ± 0.35 J m −1 and 7.33 ± 1.19 J m −1 , respectively, which are about two times greater than that of neat PHBV. Furthermore, the biodegradability of the PHBV/ENR blends was more substantial than that of neat PHBV, showing a mass reduction of approximately 40% and 45% for PHBV/ENR-25 and PHBV/ENR-50, respectively. In comparison, while the mass loss of PHBV was approximately 37% after three months of soil burial. The results indicate that ENR improves the toughness of the blends while simultaneously increasing PHBV degradation, which could pave the way for broadening PHBV for sustainability purposes.