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Mechanical strength and toughness are usually mutually exclusive, but they can both appear in natural rubber (NR). Previous studies ascribe such excellent properties to highly cis stereoregularity of NR. To our surprise, after the removal of non-rubber components (NRC) by centrifugation, the strength and toughness of NR decrease dramatically. It is still a challenge for us to make out for the problem of how NRC affect the properties of NR. Our group ascribes the superior mechanical robustness of NR to NRC. To further verify such a viewpoint, we add phospholipids (phosphatidylcholines) into NR without NRC. Phosphatidylcholines construct a sacrificial network, which ruptures preferentially upon deformation to dissipate energy. Moreover, some of phosphatidylcholines participate in the vulcanization reaction, which further improves the mechanical strength and energy dissipation. As a result, the mechanical strength and toughness of samples are as high as 21.1 MPa and 49.6 kJ/m2, respectively, which have reached the same level as that of NR. Therefore, this work not only imitates the excellent mechanical robustness of NR but also further provides a rational design for elastomers with excellent mechanical robustness.

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Natural rubber is one of most famous self-reinforced rubbers thanks to the phenomenon of strain-induced crystallization. It is usually used in avulcanized form to enhance the mechanical strength but this results in recycling issues.Herein at hermoplastic analogue of vulcanized natural rubber is obtained as as tructural mimic. Terminally functionalized polyisoprene rubber B-4A-PIP was prepared by using tetraanaline as physical crosslinking units.T he strong binding of tetra-analine groups gave B-4A-PIP ah igh tensile strength (15 MPa) and breaking strain of 890 %, which is muchhigher than those of undecorated copolymer B-OH-PIP.B -4A-PIP has as imilar onset strain of crystallization and crystallization index to vulcanized natural rubber.R andomly functionalized polyisoprene R-4A-PIP showed am uchl ower mechanical strength and SIC properties although R-4A-PIP and B-4A-PIP possessed similar molecular weights and amounts of tetraanaline groups.Rubbers derived from conjugated diene monomers present avast kind of commodity in the tire industry and our everyday life.A mong them, natural rubber products possess superior properties such as high tensile strength, high toughness and crack growth resistance,w hich are closely related to their terminal polar components and strain-induced crystallization (SIC) phenomena. [1][2][3] Although synthetic polyisoprene possesses similar main chain structure with natural rubber,i ts performance such as raw rubber strength, anti-fatigue and SIC properties of vulcanized form still lag behind of natural rubber. [4] Not only are the stereoregularity and molecular weights of polyisoprenes associated with their performance, but also the terminal structures. [5] Ty pically,the w-terminal of natural rubber consists of non-covalently connected proteins and a-terminal consists of phospholipids.Each polar terminal contributed to mechanical performance with specific way. [6] Inspired by this unique phenomenon found in natural rubber, one way to improve the performance of synthetic diene rubber should tune to terminal functionalization. However, this approach is rarely adopted mainly due to lack of suitable synthetic methods.A nd successful mimic of terminal struc-ture and functionality of natural rubber will deepen our understanding on high performance diene rubbers.In the meantime,r ecyclability is also very important for rubber usage.Ahuge amount of vulcanized rubbers are buried or incinerated because of inefficient recycling techniques,not only resulting in waste but also pollution. To solve this problem, malleable materials such as thermoplastic rubbers or thermosets with covalent dynamic networks [7] could be alternative options.T ypical thermoplastic rubber such as SBS does not possess the self-reinforcement properties.R ubber with ad ual-dynamic network design was made by Guo and his co-workers to achieve high mechanical performance with self-healing capability, [8] but the SIC peaks were weak even at high strain. Arecently developed vitrimer with dynamic covalent networks is still in its ...

Non-rubber components, mainly indicating phospholipid and protein, were separately removed from natural rubber to individually study their effect on structure and properties of the rubber. Fourier Transform Infrared Spectroscopy (FTIR) and 1 H nuclear magnetic resonance ( 1 H NMR) were applied to characterize the chemical structure and the non-rubber component residual. Rheology study and stress relaxation measurement were adopted to study the role non-rubbers played in natural networks. Rheological study of natural rubber (NR) and deproteinized natural rubber (DPNR) exhibited similar dynamic modulus at 170 o C. The lack of superposition in van Gurp Palmen (vGP) curves at different temperature for NR and DPNR, together with the shape of vGP curves proved that long chain branching was mainly constructed by phospholipid. Stress relaxation measurement at room temperature was fitted with Maxwell model and showed that NR relaxation curve underwent a quick decrease and then come to 58% equilibrium stress retention, about 3 times higher than that of DPNR, indicating that protein in NR contributed to the network structure at room temperature. Combined the chemical with molecule dynamic study, the interaction between protein and phospholipid in non-rubber component network was proposed.

Waste rubber powder (WRP) was modified by microwave, sol-gel method, and both microwave and sol-gel method, respectively. The mechanical and dynamic mechanical properties of natural rubber (NR)/modified WRP composite were investigated. The influence of bis-(3-(triethoxysilyl)-propyl)-tetrasulfide (TESPT) content on curing characteristics and mechanical properties of vulcanizate was also studied. The results showed that NR/WRP modified by both microwave and sol-gel method composite owned the best mechanical properties. Rubber processing analyzer was used to characterize the interaction between silica and rubber chains and the dispersion of silica. With increase of TESPT content, the Payne effect decreased. Scanning electron microscopy indicated the coherency and homogeneity of in situ generated silica filled vulcanizate. Dynamic mechanical analyzer showed that NR/WRP modified by both microwave and sol-gel method composite with 5 phr TESPT exhibited the lower tan d at temperature range of 50-80 C, compared with composite without TESPT and the higher tan d at temperature of 0 C, compared with the conventional modification of WRP.