The effect of nanocellulose (3 or 5 wt%) on the PLA properties was investigated. Moreover, the possibility of using such composites as an expansion joint material was considered. Nanocellulose was obtained from wastepaper by mechano-chemical treatment. The structure, impact strength, tensile strength of the composites and the adhesion to the cement were studied. It was observed that with the increasing nanocellulose content, the impact strength and tensile strength decreased because of weak interactions at the interface and formation of agglomerates.

Two-dimensional (2D) materials have been widely used for the construction of functional materials with enhanced properties and functions. In this work, we demonstrate the fabrication of carbon fiber (CF)-based composites through the modification of CFs with 2D MXene (Ti3C2Tx) nanosheets via the layer-by-layer (LbL) technique, which is assisted by the bridge crosslinking of poly(3-glycidyloxypropyldimethoxymethylsilane) (pGPDMS). It is found that the Ti3C2Tx/pGPDMS hierarchical structure provides powerful mechanical interlocking and chemical bonding interactions between CFs and the epoxy (EP) matrix, contributing to the formation of high-quality interface materials of CF/EP composites. Compared with unmodified CF/EP composites, the fabricated Ti3C2Tx/pGPDMS-CF/EP composites with four-layer Ti3C2Tx nanosheets exhibit the largest interfacial shear strength with an increase of 82.2%. In addition, the surface energy and compatibility of CFs are greatly improved. This study presents a potential strategy to construct hierarchical structure via 2D material modification and LbL assembly, and shows successful pathway to enhance the interfacial and mechanical performance of CF/EP composites.

Polymer composites with tailored structure and enhanced properties and functions have attracted great attentions due to their wide applications in materials science, nanotechnology, and engineering science. In this work, we demonstrate the innovative concepts of fabricating both gradual "rigid-flexible" and alternate "rigid-flexible" structures, which are achieved by altering the grafting sequence of flexible polyethyleneimine with high flexibility and polydopamine with suitable rigidity. Then, the effect of different rigid-flexible structures on the structure and properties of the carbon fiber-epoxy (CF/EP) composites are studied. It is found that the composites reinforced by the alternate rigid-flexible polymer layer possess superior interfacial effects and mechanical properties. Compared with the CF/EP without polymer layer modification, the rigid-flexible layer contributes to about 80.3% and 167.3% on the interfacial shear strength and the impact strength of final composites. These great improvements are attributed to the complex crack propagation path, more energy consumption, wider interface region, higher wettability, as well as strong physical and chemical interactions. This work provides practical and scalable potentials for regulating the structure and functions of the CF-reinforced polymer composites by optimal interfacial design.

Carbon nanotubes (CNT) and ethanol -assisted mixing were used to obtain composites based on a mixture of natural rubber and butadiene rubber (NR/BR 80/20). The structure of the composites was determined by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Thermal aging tests were also carried out and the vulcanization process was characterized. SEM confirmed the homogeneous dispersion of CNTs in the polymer matrix. Improvements in tensile and tear strength as well as thermal stability were also achieved.

The effect of the mixing method (normal and ethanol-assisted) on selected properties of natural rubber with butadiene rubber blends (NR/BR 80/20) was investigated. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) were used to evaluate the properties. In addition, the mechanical tensile properties, tear resistance and thermal aging, as well as vulcanization characteristic were determined. It was found that ethanol-assisted mixing can significantly improve the mechanical properties and thermal stability of the blends as a result of better dispersion of additives in the rubber matrix.

Carbon fiber (CF) reinforced matrix composites have been applied widely, however, the interfacial adhesion of composites is weak due to smooth and chemically inert of CF surface. To solve this problem, A polydopamine/nano-silica (PDA-SiO2) interfacial layer on carbon fiber surface was constructed via polydopamine and nano- SiO2 (CF-PDA-SiO2) by a facile and effective method to reinforce polyamide 6 composites (CFs/PA6). The effects of PDA-SiO2 interfacial layer on crystallization structure and behavior, thermal properties, and mechanical properties of CFs/PA6 composites were investigated. Furthermore, interfacial reinforcement mechanism of composites has been discussed. This interfacial layer greatly increased the number of active groups of CF surface and its wettability obviously. The tensile strength of CF-PDA-SiO2/PA6 composites increased by 28.09%, 19.37%, and 26.22% compared to untreated-CF/PA6, CF-PDA/PA6, and CF-SiO2/PA6 composites, respectively, which might be caused by the increased interfacial adhesion between CF and PA6 matrix. The thermal stability, crystallization temperature, crystallinity, and glass transition temperature (T-g) of CF-PDA-SiO2/PA6 composites improved correspondingly, attributing to the heterogeneous nucleation of nano-SiO2 in the crystalline area and hydrogen bonds with molecular chains of PA6 in the amorphous area. This work provides a novel strategy for the construction of interfaces suitable for advanced CF composites with different structures.

Abstract A double grafted interfacial layer on CF surface was constructed via PDA and nano-SiO2 (CF-PDA-SiO2) by a facile and effective method to reinforce polyamide 6 composites (CFs/PA6). The effects of double grafted interfacial layer on crystallization structure and behavior, thermal properties, and mechanical properties of CFs/PA6 composites were investigated. This interfacial layer greatly increased the number of active groups, roughness and wettability of CF surface, the tensile strength of CF-PDA-SiO2/PA6 composites increased by 28.09%, 19.37%, and 26.22% compared to untreated-CF/PA6, CF-PDA/PA6, and CF-SiO2/PA6 composites, respectively, which might be caused by the increased interfacial adhesion between CF and PA6 matrix. The thermal stability, crystallization temperature, crystallinity, as well as glass transition temperature (Tg) of CF-PDA-SiO2/PA6 composites improved correspondingly, attributing to the heterogeneous nucleation of nano-SiO2 in the crystalline area and hydrogen bonds with molecular chains of PA6 in the amorphous area. Furthermore, interfacial reinforcement mechanism of composites have been discussed.

Schiff’s base iron salt can be used as a new and effective antioxidant for rubber compounds.The tensile strength after 96 h of aging was approx. 36% and 12% higher, respectively, than in the caseof the antioxidants 4010NA and BHT used. Natural rubber vulcanizate (NR) containing the iron salt of Schiff’s base showed excellent rheological and mechanical properties, as well as very good thermalstability. These properties were far superior to that of other commercially available antioxidant rubber blends.

The influence of UV radiation on the physical and mechanical properties of polyurethane resins and three-proof polyurethane coatings was examined. Changes of mechanical properties and the gloss of resins and coatings were determined. The structure of materials was confirmed using scanning microscopy SEM and Fourier transform infrared spectroscopy FTIR; thermogravimetric TGA and DTG studies were also performed. It turned out that the gloss of finished protective coatings was worse than the gloss of individual resins, and aging significantly lowered these values (from 81.3° to 8.9° in case of resins and from 61.1° to 2.8° in case of coatings after 1200 hours of irradiation). Tensile strength of resins decreased constantly during aging while their elongation at break decreased than increased reaching minimum at exposure time of 100 hours. In case of coatings, both tensile strength and elongation at break firstly decreased than increased reaching minimum at exposure time of 800 hours; after long exposure time, more than 1200 hours, these properties decreased again.

An optimized "rigid-flexible" structure with multistage gradient modulus was constructed on carbon fiber (CF) surface via chemical grafting using "flexible" polyethyleneimine (PEI) and "rigid" polydopamine (PDA) between "rigid" CF and "flexible" epoxy (EP) to elaborate a double alternant "rigid-flexible" structure for simultaneously strengthening and toughening CF/EP composites. PDA and PEI polymers can greatly enhance the roughness and wettability of CF surfaces, further strengthening the mechanical interlocking and chemical interactions between CFs and epoxy. Besides, the "rigid-flexible" structure endows the interface with a gradient transition modulus, which could uniformly transfer internal stress and effectively avoid the stress concentration. Moreover, the double alternant "rigid-flexible" could buffer the external loading, induce more micro cracks and propagation paths and, thereby, consume more energy during the destruction of the composite. The interfacial shear strength, interlaminar shear strength, impact strength increased by 80.2%, 23.5% and 167.2%, and the fracture toughness improved by 227.2%, compared with those of the unmodified CF composite, respectively. This creative strategy and design afford a promising guidance for the preparation and production of advanced CF/EP structural materials with high strength and toughness.