No abstract

No abstract

Aliphatic waterborne polyurethane-ureas (WPUU) were prepared using 1,6-hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI) as mixed diisocyanates. The effects of the HDI/IPDI ratio on the phase morphology of WPUU films including the hydrogen bonding, crystallization of the soft segment and hard segment, and phase separation were investigated. The relationship between the phase morphology and the mechanical properties was also studied. The FTIR spectrum showed that the hydrogen bonding degree in the hard segments increased as the HDI/IPDI ratio increased. XRD analysis revealed the excellent crystallinity of WPUU films. DSC analysis indicated that the degree of phase separation was improved with increasing HDI/IPDI ratio, and DMA analysis showed that the storage modulus of the WPUU film increased at first and then decreased. When the HDI/IPDI ratio was 4:1, the WPUU films exhibited high tensile strength.

The non-polarity of polypropylene has restricted its use; therefore it needs to be modified. Maleic anhydride grafted polypropylene(PP-g-MAH) is such a kind of modified polypropylene; however its polarity is still low. In order to improve its polarity, chlorinated maleic anhydride-grafted polypropylene (Cl-PP-g-MAH) prepared by free radical polymerization was carried out using PP-g-MAH as reaction material, carbon tetrachloride (CCl4) as solvent and benzoyl peroxide (BPO) as initiator. The products were characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Nuclear Magnetic Resonance Spectroscopy (NMR). The effects of the reaction temperature, reaction time, flow rate of chlorine and concentrations of PP-g-MAH and BPO initiator on the degree of chlorination were studied. The optimum technological conditions were obtained, and the surface tension, light transmission, particle size and tensile strength of chlorinated maleic anhydride grafted polypropylene were better than those of maleic anhydride grafted polypropylene. After modification by maleic anhydride and chlorine, PP could meet commercial needs in the fibre composites, adhesives, printing inks, coatings and plastics industries.

In this paper, PVA/PAA‐PAM‐IS/GC composite hydrogels are prepared using polyvinyl alcohol (PVA), poly acrylic acid (PAA), poly acrylamide (PAM), and iron sulfate hydrate (IS) glycerol (GC). The crosslinking network is formed by the coordination of carboxyl groups with ions, which forms PVA with semi‐interpenetrating network. The mechanical properties and self‐healing properties of PVA/PAA‐PAM‐IS/GC composite hydrogels are excellent. The stress, strain and self‐healing efficiency of PVA/PAA‐PAM‐IS/GC composite hydrogels can reach 840 kPa, 784%, and above 95%, respectively. The antifreeze and water retention properties of PVA/PAA‐PAM‐IS/GC composite hydrogels are improved by glycerol. PVA/PAA‐PAM‐IS/GC composite hydrogels remains flexible at low temperatures and moist for a long time at room temperature. The conductivity of the hydrogel increases with the increase of temperature because the interactions between glycerol, water molecules and ammonium ions are affected by the temperature, the multifunctional conductive hydrogel can be used in strain sensing and temperature sensing. In summary, PVA/PAA‐PAM‐IS/GC composite hydrogels can provide a guide in the field of electronic intelligence.

Intercropping is widely used in agricultural production due to its capability of raising land productivity and providing an opportunity to achieve sustainable intensification of agriculture. In this study, soil samples from 10 to 20 cm depth of intercropping Pinto peanut in litchi orchard and litchi monoculture mode were established to determine soil attributes, enzyme activities, as well as the effect on soil bacterial diversity. On this basis, 16S rRNA V4-V5 region of soil bacterial communities in litchi/Pinto peanut intercropping (LP) mode and litchi monoculture mode (CK) was detected by the Illumina MiSeq sequencing platform. The results showed that the content of available potassium (AK) in LP was significantly higher than that in CK by 138.9%, and the content of available nitrogen (AN) in LP was significantly lower than that in CK by 19.6%. The soil enzyme activities were higher in LP as a whole, especially sucrase (SC) and acid protease (PT) were significantly higher by 154.4 and 76.5%, respectively. The absolute abundance and alpha diversity of soil microbiota were significantly higher in the intercropping group. Most importantly, endemic species with a significant difference in LP was higher by ~60 times compared to CK treatment. In the aspect of soil bacterial community structure, the dominant phyla of the two groups were Acidobacteria, Proteobacteria, Chloroflexi, and Actinobacteria. At the genus level, the absolute abundance of Flavobacterium and Nitrososphaera was significantly higher by 79.20 and 72.93%, respectively, while that of Candidatus_Koribacter was significantly lower with an amplitude of 62.24% in LP than in CK. Furthermore, the redundancy analysis (RDA) suggested that AK, which was highly associated with the dominant genera and phyla, is the vitally dominating environmental factors in LP groups, while in CK groups, it is AN and pH. In addition, PICRUSt2 analysis indicated that intercropping improved the metabolic activity of bacteria which can be correlated to the resistance of litchi root systems to soil-borne diseases. Overall, this study is expected to provide a theoretical basis and technical support for the healthy intercropping cultivation of litchi.

Jackfruit (Artocarpus heterophyllus) is an important tropical commercial fruit crop grown in Hainan province, China. In recent years, severe jackfruit bronzing disease has been found in 11 cities and counties in Hainan. On average, 80% of trees in a jackfruit orchard are affected once bronzing disease is detected. The disease is characterized by yellow-orange to reddish discoloration of the pulp and rags of infected fruit (Hernández-Morales et al. 2017). Jackfruit bronzing disease has been reported previously in the Philippines (Gapasin et al. 2012), Malaysia (Zulperi et al. 2017), and Mexico (Hernández-Morales et al. 2017). Diseased samples of jackfruit ‘Tai Eight’ with the bronzing symptoms were collected from a plantation in Changjiang, Hainan. The samples were sterilized with 75% ethanol for 30 s, then soaked with 1% sodium hypochlorite for 8 min, and rinsed with sterilized distilled water. The sterilized tissues were ground in 2 mL sterile water, and allowed to stand for 30 min. Then, 500 μL of the supernatant was spread on Glucose–Yeast agar medium and incubated overnight at 28ºC. Representative bacterial colonies were lemon-yellow, convex and smooth, transparent with entire edges. Colonies were Gram-negative, positive for catalase and gelatin liquefaction, which were consistent with the characteristics of P. stewartii subsp. stewartii. In PCR amplifications, an 920 bp amplicon of strain JTPE2 with the primers ES16/ESIG2c (Coplin et al. 2002) and an 1100 bp amplicon of strain JTPC2 with the primers CPSL1/CPSR2c (Ibrahim et al. 2019) were obtained, whereas no bands were observed for the negative control samples. The ES16/ESIG2c and CPSL1/CPSR2c fragments were sequenced for nucleotide BLAST (BLASTn) searches of the NCBI database and phylogenetic tree construction. The obtained ES16/ESIG2c sequences (SAR accession no. SRR22405292) showed 99.07%–99.60% similarity with P. stewartii subsp. stewartii (CP017581, AJ311838 and MF598163). The obtained CPSL1/CPSR2c sequences (SAR accession no. SRR22405293) showed 99.40%–99.99% similarity with P. stewartii subsp. stewartii (MW971422, MH752485 and MH257287). Phylogenetic analysis based on cpsDE sequences (Ibrahim et al. 2019) using the maximum likelihood method revealed that strains JTPE2 and JTPC2 were clustered together with P. stewartii subsp. stewartii. A pathogenicity test was conducted by injecting 2 mL of 108 CFU/ml bacterial suspension into pulp from healthy, surface-sterilized jackfruit. Pulp injected with sterilized distilled water served as a negative control. All inoculated samples produced bronzing symptoms from 2–3 weeks post-inoculation similar to the field-observed symptoms, whereas control fruit were asymptomatic. The strains were reisolated from symptomatic jackfruit pulp to complete Koch’s postulates. The bacterial suspension was inoculated on 2-week-old maize seedlings to supplement in vivo pathogenicity testing. Typical Stewart’s disease leaf symptoms were visible at 2 weeks post-inoculation. Based on morphological, biochemical, and physiological evidence, pathogenicity tests, and molecular analyses, the pathogenic bacterium isolated from ‘Tai Eight’ jackfruit was identified as P. stewartii subsp. stewartii. To our knowledge, this is the first report of bronzing disease caused by P. stewartii subsp. stewartii on jackfruit in China, which may assist in preventing the global spread of jackfruit bronzing disease.

Acrylic acid (AA) grafting onto chlorinated polypropylene (CPP) was carried out using toluene as solvent and benzoyl peroxide (BPO) as initiator by free radical polymerization. The effects of reaction temperature, concentration of acrylic acid monomer and benzoyl peroxide initiator on the rate of graft polymerization were studied. The rate of graft polymerization depended on the initiator and monomer concentrations. The actual rate constant of graft polymerization was found to obey the Arrhenius law and the activation energy E value was 40.6 kJ/mol. The kinetic equation for the grafting of acrylic acid onto chlorinated polypropylene was R = K [BPO] [AA]0.62.