Dynamic ageing research of cross‐linked polyethylene cable insulation based on temporal‐spatial dimension under combined electro‐thermal effect

Dynamic ageing process of cross‐linked polyethylene(XLPE)cable insulation under combined electro‐thermal effect is investigated by the construction of theoretical analysis model and the practice of operation‐simulated ageing test.Firstly,theoretical analysis model is constructed from time and spatial dimensions.From the time dimension,in the light of the impeding trend of internal stress to external stress,the XLPE ageing process of Steady state‐Transition state‐Steady state(STS)is proposed to illustrate the dynamic ageing process of XLPE.From the spatial dimension,the insulation is divided into three scales to quantify the ageing.Secondly,to practice the theoretical analysis model,an operation‐simulated ageing test was conducted on two high voltage alternating current cables with service years of 15 and 30 for 540 days.Subsequently,relevant diagnostic measurements were applied to analyse the influence of physicochemical characteristics on the dielectric and heat transfer performances of the cables.The results show that the degradation of the actual operating cable is an extremely slow process.On the one hand,the response in physical changes of morphology counterbalances the external stress,maintaining the stability.On the other hand,once the chemical changes occur,negative feedback mechanism tends to impede the occurrence of further degradation by regulating fields distribution.

Exploiting styrene-maleic acid copolymer grafting chromatographic stationary phase materials for separation of membrane lipids

High performance liquid chromatography-mass spectrometry is one of the most commonly used strategies for lipid analysis.The development of versatile chromatographic stationary phases to meet the increasing demands for separation of complex lipids is very important.Styrene-maleic acid(SMA)copolymer is an amphiphilic polymer,which has been proven to have the ability to solubilize lipid molecules of various structures.In this study,styrene-maleic anhydride copolymer coated silica was first prepared by the thiol-ene click reaction.With L-cysteine hydrochloride or dodecanol as the post-modification reagents,Sil-SMA-amino acid and Sil-SMA-dodecanol stationary phase materials were further successfully fabricated via nucleophilic ring-opening reaction.The Fourier-transform infrared,thermogravimetric analysis,and elemental analysis results confirmed the two stationary phase materials were successfully prepared.Furthermore,both the Sil-SMA-dodecanol column and the Sil-SMA-amino acid column possessed reversed-phase/hydrophilic interaction/ion exchange mixed-mode retention mechanisms.The column efficiency of the Sil-SMA-derivatives columns reached 77,300 N/m.Based on the mixed-mode retention characteristics,the Sil-SMA-derivatives columns achieved both the lipid classes and species separation via a single column.The Sil-SMA-amino acid column was further successfully used to separate lipid extract from gastric cancer cell membrane.All these results demonstrated that the SMA-based stationary phase materials have a good potential for use in lipid separation.