In order to explore the thermal conductivity of polypropylene(PP)/hexagonal boron nitride(BN) composites,PP composites filled with different proportions of BN were prepared through extrution compounding,injection moul...In order to explore the thermal conductivity of polypropylene(PP)/hexagonal boron nitride(BN) composites,PP composites filled with different proportions of BN were prepared through extrution compounding,injection moulding and compression moulding.The composites were filled with BN particles of 5 and 20 μm respectively,and their mass fractions in composites were considered.Percentage of BN was varied from 0 to 25wt% in steps of 5wt%.The effects of BN filler on mechanical properties of the composites were evaluated.The thermal behaviors were studied using DSC and TGA,and the thermal conductivity was also investigated by Laser Flash Device and the Model of 3D Heat Conduction respectively.The experimental results show that impact strength of PP/BN can be enhanced with the addition of BN,but that composites exhibit lower breaking elongation & tensile strength when compared to unfilled ones.It is found that mass fraction of BN influenced the final thermal stability and degree of crystallization of PP matrix,the degree of crystallization of PP with 15wt% of 20 μm BN can be improved by 25% than neat PP.Meanwhile,crystallization temperatures of PP composites are elevated by about 10 ℃.The thermal conductivity results demonstrate that the maximum value of the thermal conductivity is achieved from PP/BN with 20wt% of 20 μm BN,higher than that of pure PP by 95.65%,close to the simulation one.展开更多
Drought stress is a serious threat to the germination of plant seeds and the growth of seedlings.Melatonin has been proven to play an important role in alleviating plant stress.However,its effect on seed germination u...Drought stress is a serious threat to the germination of plant seeds and the growth of seedlings.Melatonin has been proven to play an important role in alleviating plant stress.However,its effect on seed germination under drought conditions is still poorly understood.Therefore,we studied the effects of melatonin on rice seed germination and physiological characteristics under drought stress.Rice seeds were treated with different concentrations of melatonin(i.e.,0,20,100,and 500μM)and drought stress was simulated with 5%polyethylene glycol 6000(PEG6000).The results showed that 100μM melatonin can effectively improve the germination potential,rate and index;the vigor index of rice seeds;and the length of the shoot and root.In addition,that treatment also increased the activity of superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT),and reduced the content of malondialdehyde(MDA).The grey relational grade between the shoot MDA content and the melatonin seed-soaking treatment was the highest,which could be useful for evaluating the effect of melatonin on drought tolerance.Two-way analysis of variance showed that the effect of single melatonin treatment on rice seeds was more significant than that of single drought stress and interaction treatment of drought and melatonin(p<0.05).The subordinate function results showed that 100μM melatonin significantly improved the germination and physiological indexes of rice seeds and effectively alleviated the adverse effects of drought stress on rice seedlings.The results helped to improve the understanding of the morphological and physiological involvement of melatonin in promoting seed germination and seedling development under drought stress.展开更多
基金Funded by the State Grid Henan Electric Power Company Technology Project(No.521790200018)the 2021 Key Scientific Research Projects of Higher Education Institutions in Henan Province(No.21A430047)the Excellent Team Project of Scientific and Technological Innovation in Henan Province(HNST [2017] No.9)。
文摘In order to explore the thermal conductivity of polypropylene(PP)/hexagonal boron nitride(BN) composites,PP composites filled with different proportions of BN were prepared through extrution compounding,injection moulding and compression moulding.The composites were filled with BN particles of 5 and 20 μm respectively,and their mass fractions in composites were considered.Percentage of BN was varied from 0 to 25wt% in steps of 5wt%.The effects of BN filler on mechanical properties of the composites were evaluated.The thermal behaviors were studied using DSC and TGA,and the thermal conductivity was also investigated by Laser Flash Device and the Model of 3D Heat Conduction respectively.The experimental results show that impact strength of PP/BN can be enhanced with the addition of BN,but that composites exhibit lower breaking elongation & tensile strength when compared to unfilled ones.It is found that mass fraction of BN influenced the final thermal stability and degree of crystallization of PP matrix,the degree of crystallization of PP with 15wt% of 20 μm BN can be improved by 25% than neat PP.Meanwhile,crystallization temperatures of PP composites are elevated by about 10 ℃.The thermal conductivity results demonstrate that the maximum value of the thermal conductivity is achieved from PP/BN with 20wt% of 20 μm BN,higher than that of pure PP by 95.65%,close to the simulation one.
基金This work was funded by the National Natural Science Foundation of China(31971923,31301650)the National Key R&D Program of China(2017YFD0301501)+2 种基金the Hunan Provincial Natural Science Foundation of China(2020JJ4360)the Key Scientific Research Project of Hunan Provincial Education Department of China(19A220)Innovation and Entrepreneurship Training Program for College Students of Hunan Agricultural University(XCX2021038).
文摘Drought stress is a serious threat to the germination of plant seeds and the growth of seedlings.Melatonin has been proven to play an important role in alleviating plant stress.However,its effect on seed germination under drought conditions is still poorly understood.Therefore,we studied the effects of melatonin on rice seed germination and physiological characteristics under drought stress.Rice seeds were treated with different concentrations of melatonin(i.e.,0,20,100,and 500μM)and drought stress was simulated with 5%polyethylene glycol 6000(PEG6000).The results showed that 100μM melatonin can effectively improve the germination potential,rate and index;the vigor index of rice seeds;and the length of the shoot and root.In addition,that treatment also increased the activity of superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT),and reduced the content of malondialdehyde(MDA).The grey relational grade between the shoot MDA content and the melatonin seed-soaking treatment was the highest,which could be useful for evaluating the effect of melatonin on drought tolerance.Two-way analysis of variance showed that the effect of single melatonin treatment on rice seeds was more significant than that of single drought stress and interaction treatment of drought and melatonin(p<0.05).The subordinate function results showed that 100μM melatonin significantly improved the germination and physiological indexes of rice seeds and effectively alleviated the adverse effects of drought stress on rice seedlings.The results helped to improve the understanding of the morphological and physiological involvement of melatonin in promoting seed germination and seedling development under drought stress.
