Enhanced thermal and mechanical properties of liquid crystalline-grafted graphene oxide-filled epoxy composites

The effects of functionalized graphene oxide on the thermal and mechanical properties of liquid crystalline polymers

Herein, we report a robust approach for the selective covalent functionalization of graphene oxide (GO) with 4-hydroxybenzoic acid (HBA) for developing polymeric nanocomposites based on liquid crystalline polymers (LCPs). The functionalization of GO with HBA was confirmed by Raman spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, and X-ray diffraction (XRD) spectroscopy. The surface morphology of GO and functionalized GO (FGO) was studied using field emission scanning electron microscopy (FE-SEM). Furthermore, the interactions between FGO and LCPs have been investigated by FT-IR spectroscopy, whereas dispersion of GO and FGO in the LCP matrix was analyzed by FE-SEM. The better dispersion of FGO can be attributed to the hydrogen bonding and π-π stacking interactions between FGO and LCPs. Our results showed that even the addition of 5 wt% FGO in the LCP matrix significantly enhances the tensile strength and storage modulus of the pristine LCPs by 84% and 78% respectively. Compared to neat LCPs, FGO incorporated composites also demonstrate an improvement in the melting temperature (T_m) by 11 °C and glass transition temperature (T_g) by 12 °C. Furthermore, thermogravimetric analysis (TGA) was performed to evaluate the thermal stability of the composite. The 5 and 50% decomposition temperature for the LCP/FGO nanocomposites (containing 5 wt% FGO) increased by 75 °C and 107 °C respectively.

Nano-modified epoxy: the effect of GO-based complex structures on mechanical performance

The application of nanofillers (NFs) in multicomponent polymer systems is accompanied by important structure-directing effects that are more marked in partially miscible systems, such as polymer-modified epoxy. This study deals with rubber-modified epoxy using different combinations of GO and amine-terminated butadiene-acrylonitrile copolymer (ATBN), including in situ and pre-made grafting. Moreover, GO grafted via planar epoxy groups or solely edge-localized carboxyls was used. It is shown that the grafted ATBN chains promote the assembly of GO-g-ATBN into nacre-mimicking lamellar structures instead of usual exfoliation in thermoplastics. This complex structure of elastically embedded GO leads to the best mechanical performance. It is obvious that a small concentration of the grafted polymer exceeds the contribution of a higher concentration of separately added ATBN. The results highlight the important effect of the degree of grafted chains and geometry of the internal structure of the self-assembled arrays and their effect on the mechanical performance.

ATBN-grafted GO forms nacre-mimicking lamellar structures in epoxy; the effect of grafting geometry on the structure/property relationship is highlighted.

The influence of liquid crystals on the properties of sisal fibre polyurethanes with multi-shape memory effects

LC-SF-SMPUs show excellent multi-shape memory properties.

Research on the preparation of heat-resistant epoxy resin cured by o-carborane-based diamine

A novel carborane-containing epoxy resin was prepared via the curing reaction between epoxy resin (E51) and 1,2-bis(4-aminophthalimide)dimethyl-1,2-dicarba-closododecaborane (4-AP CBR). According to the nonisothermal differential scanning calorimetry method and the T-β extrapolation method, the curing temperatures of the 4-AP CBR/E51 system were theoretically determined. The cured carboranyl epoxy resin was analyzed by thermogravimetric analysis (TGA), which revealed that the resin had excellent thermal stability and thermal oxidative stability. The results of TGA indicated that the initial decomposition temperature of the resin was exceeding 400°C and the char yield at 800°C was around 60% both under nitrogen and in air atmosphere.