In order to obtain multiwalled carbon nanotubes (MWNTs)/epoxy composites with good mechanical properties at cryogenic temperature, two methods were adopted to modify MWNTs. MWNTs were first treated by acid mixture (oxidized MWNTs, O-MWNTs) and then maleic anhydride (MA) and isophorone diisocyanate (IPDI) grafting was carried out. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses proved the effectiveness of acid mixture treatment and confirmed the grafting reaction of MA and IPDI with MWNTs. High-resolution transmission electron microscopy analysis indicates that MA and IPDI chain were grafted onto the MWNTs surface, creating a rigid covalent bond between MWNTs and epoxy resin and forming a thin layer. The tensile strength, Young’s modulus, and impact strength of composites at liquid nitrogen temperature (77 K) are all enhanced by the addition of MWNTs. Results of dynamic mechanical analysis indicated that introducing a small amount of functionalized MWNTs to epoxy can enhance their storage modulus at 77 K and glass transition temperature of composites. The results indicated that surface-modified MWNTs can be effectively utilized to improve the properties of epoxy-based composites at cryogenic temperature.
In order to obtain epoxy based composite with low coefficient of thermal expansion (CTE) and good mechanical properties at cryogenic temperature (77 K), core–shell rubber (CSR) particles were integrated into epoxy. Fourier transform infrared spectroscopy results showed the occurrence of intermolecular hydrogen bond between the CSR particles and the epoxy matrix. The results of thermomechanical analysis indicate that the CTE of CSR–epoxy composites below Tg reached the minimum of the CSR content of 0·5 wt-%, then followed by an increase when the CSR content was higher than 0·5 wt-%. The CTE value under Tg was decreased 18·89% with 0·5 wt-% CSR content. The tensile strength, Young's modulus and impact strength of CSR–epoxy composites at 77 K all reached a maximum with the CSR content of 0·5 wt-%, followed by a decrease when the CSR content was higher than 0·5 wt-%. The storage modulus of CSR modified epoxy resin in glassy region was higher than that of the neat epoxy resin.
Tinospora sagittata (Oliv.) Gagnep. is an important medicinal tetraploid plant in the Menispermaceae family. Its tuber, namely "Radix Tinosporae" used in Traditional Chinese Medicine, is rich in medicinal terpenoids and benzylisoquinoline alkaloids (BIAs), To enhance understanding the biosynthesis of medicinal compounds, we, herein, report the assembly of a high quality chromosome-scale genome with both PacBio HiFi and Illumina sequencing technologies. The size of assembled genome was 2.33 Gb consisting of 4070 scaffolds (N50=42.06Mb), of which 92.05% were assigned to 26 pseudochromosomes in A and B sub-genomes. A phylogenetic analysis with the T. sagittata and other 16 plant genomes estimated the evolutionary placement of T. sagittata and its divergence time in Ranunculales. Further genome evolution analysis characterized one round tandem duplication about 1.5 million years ago (MYA) and one whole-genome duplication (WGD) about 86.9 MYA. WGD contributed to the duplication of clade-specific cytochrome P450 gene family in Ranunculales. Moreover, sequencing mining obtained genome-wide genes involved in the biosynthesis of alkaloids and terpenoids. TsA02G014550, one candidate, was functionally characterized to catalyze the formation of (S)-canadine in the jatrorrhizine biosynthetic pathway. Taken together, the assembled genome of T. sagittata provides useful sequences to understand the biosynthesis of jatrorrhizine and other BIAs in plants.
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