In this work,the optimal electrospinning conditions of trans-polyisoprene(TPI)solutions were evaluated nevertheless its lower glass transition temperature than the room temperature.Subsequently,chemical crosslinking o...In this work,the optimal electrospinning conditions of trans-polyisoprene(TPI)solutions were evaluated nevertheless its lower glass transition temperature than the room temperature.Subsequently,chemical crosslinking of TPI nonwovens was firstly investigated by vulcanizing at high temperatures in the case of the persistence of nanofiber structure.For this purpose,curing agents of TPI were embedded in TPI nanofibers by co-electrospinning,and then a protect layer was coated on TPI nanofibers by filtering gelatin solution going through TPI nonwoven before the vulcanization at 140-160℃.The results showed that the vulcanization of TPI fibrous nonwoven at high temperatures did not destroy the fiber morphology.Interestingly,TPI fibrous nonwovens after vulcanization showed excellent mechanical properties(N17 MPa of tensile strength)that could be comparable to or even higher than that of some bulk rubber materials.展开更多
For the solid-solid transformation from formⅡto formⅠof isotactic polybutene-1(iPB),the temperature dependence of formⅠnucleation and growth was deemed to control the transformation process.However,the relationship...For the solid-solid transformation from formⅡto formⅠof isotactic polybutene-1(iPB),the temperature dependence of formⅠnucleation and growth was deemed to control the transformation process.However,the relationship between formⅠformation and formⅡdisappearance in the transformation process is not clear.In this work,the spontaneous crystal transformation from formⅡtoⅠof iPB with 81 mol%mmmm sequence concentration is studied firstly by tracking the two processes,the decay of formⅡand the yielding of formⅠin a wide range of temperature spanning from 0℃to 50℃and in a long transformation time ranging from 5 min to 65 days with in situ FTIR and WAXD.Unlike the literature reports,the decay rate of formⅡis firstly found to be lower than the yielding rate of formⅠat all studied temperatures,especially at low transition temperature.This is attributed to the amorphous chains which locate near crystal lamella participating into the nucleation of formⅡ.The regular chain folding and growth of i PB formⅠfrom amorphous chains containing short isotactic sequences also lead to an increase in crystallinity of formⅠcompared with that of initial formⅡcrystallized at 60℃.An increase in the annealing temperature results in decrease in crystallinity and increase in lamellae thickness of i PB formⅠ.展开更多
Solvent annealing is a facile method for changing the aggregated microstructure and physical properties of polymer materials.In this paper,we addressed the effects of solvent vapor annealing,including chloroform and w...Solvent annealing is a facile method for changing the aggregated microstructure and physical properties of polymer materials.In this paper,we addressed the effects of solvent vapor annealing,including chloroform and water vapor,on the polymorphic transformation in both hot-pressed film and electrospun nonwoven of isotactic polybutene-1(PB-1)by means of in situ Fourier transform infrared spectroscopy(FTIR).The pretty rapid transition rate caused by the increased motion of molecular chains under chloroform vapor is associated with a lowest crystallinity.Also,a decreased crystallinity with the crystal transition occurred in electrospun nonwovens resulting from the relaxation of the stretched molecular chains into amorphous state rather than realignment into crystal form I predominating the crystal transition process.展开更多
In this work, the crystallization of immiscible polypropylene （PP）/polybutene-1 （PB） blends, in particular the effect of crystal morphology of PP （HTC, high Tm component） on the subsequent crystallization behavi...In this work, the crystallization of immiscible polypropylene （PP）/polybutene-1 （PB） blends, in particular the effect of crystal morphology of PP （HTC, high Tm component） on the subsequent crystallization behavior of PB （LTC, low Tm component） was studied. Herein, we firstly indicated that PP/PB blends were not completely compatible but characterized as the LCST-like phase diagram above the melting temperature of PP. Crystallization of PP at different crystallization temperatures brought about different PP crystal morphologies and PB was segregated and confined at different locations. Much larger-sized domain of PB component appeared in PP spherulites resulting from the effects of non-negligible phase separation and the slower PP crystallization rate as PP crystallized at high temperature. As temperature continued to fall below Tm of PB, the fractionated and confined crystallization of PB occurred in the framework of PP spherulites, reflected by the decreased crystallization temperature （To） of PB and the formation of form I＇ beside form II. Notably, if PP previously crystallized at high Tc, fractionated crystallization of PB became predominant and confined crystallization of PB became weak due to the much wider droplet-size distribution of PB domains.展开更多
基金financially supported by the National Basic Research Program of China(No.2015CB654700(2015CB654706))the National Natural Science Foundation of China(Nos.51473083 and 21174074)+3 种基金Special Foundation of Taishan Mountain Scholar Constructive ProgramShandong Provincial Key R&D program(No.2015GGX102019)Shandong Provincial Natural Science Fund for Distinguished Young Scholars(No.JQ201213)the Yellow River Delta Scholar program(Office of National University Science&Technology Park Administrative Committee(China University of Petroleum))
文摘In this work,the optimal electrospinning conditions of trans-polyisoprene(TPI)solutions were evaluated nevertheless its lower glass transition temperature than the room temperature.Subsequently,chemical crosslinking of TPI nonwovens was firstly investigated by vulcanizing at high temperatures in the case of the persistence of nanofiber structure.For this purpose,curing agents of TPI were embedded in TPI nanofibers by co-electrospinning,and then a protect layer was coated on TPI nanofibers by filtering gelatin solution going through TPI nonwoven before the vulcanization at 140-160℃.The results showed that the vulcanization of TPI fibrous nonwoven at high temperatures did not destroy the fiber morphology.Interestingly,TPI fibrous nonwovens after vulcanization showed excellent mechanical properties(N17 MPa of tensile strength)that could be comparable to or even higher than that of some bulk rubber materials.
基金financially supported by the Major Science and Technology Innovation Project of Shandong Province(No.2019JZZY010352)Natural Science Foundation of Shandong Province(ZR2019MB072)Taishan Scholar Program
文摘For the solid-solid transformation from formⅡto formⅠof isotactic polybutene-1(iPB),the temperature dependence of formⅠnucleation and growth was deemed to control the transformation process.However,the relationship between formⅠformation and formⅡdisappearance in the transformation process is not clear.In this work,the spontaneous crystal transformation from formⅡtoⅠof iPB with 81 mol%mmmm sequence concentration is studied firstly by tracking the two processes,the decay of formⅡand the yielding of formⅠin a wide range of temperature spanning from 0℃to 50℃and in a long transformation time ranging from 5 min to 65 days with in situ FTIR and WAXD.Unlike the literature reports,the decay rate of formⅡis firstly found to be lower than the yielding rate of formⅠat all studied temperatures,especially at low transition temperature.This is attributed to the amorphous chains which locate near crystal lamella participating into the nucleation of formⅡ.The regular chain folding and growth of i PB formⅠfrom amorphous chains containing short isotactic sequences also lead to an increase in crystallinity of formⅠcompared with that of initial formⅡcrystallized at 60℃.An increase in the annealing temperature results in decrease in crystallinity and increase in lamellae thickness of i PB formⅠ.
基金financially supported by the Special Foundation of Taishan Mountain Scholar Constructive Programthe National Natural Science Foundation of China(No.21174074)+3 种基金Shandong Provincical Key R&D Program(No.2015GGX102019)Shandong Provincial Natural Science Fund for Distinguished Young Scholars(No.JQ201213)the Nature Science Foundation of Shandong Province(No.ZR2013BM004)the Yellow River Delta Scholar program(Office of National University Science&Technology Park Administrative Committee(China University of Petroleum))
文摘Solvent annealing is a facile method for changing the aggregated microstructure and physical properties of polymer materials.In this paper,we addressed the effects of solvent vapor annealing,including chloroform and water vapor,on the polymorphic transformation in both hot-pressed film and electrospun nonwoven of isotactic polybutene-1(PB-1)by means of in situ Fourier transform infrared spectroscopy(FTIR).The pretty rapid transition rate caused by the increased motion of molecular chains under chloroform vapor is associated with a lowest crystallinity.Also,a decreased crystallinity with the crystal transition occurred in electrospun nonwovens resulting from the relaxation of the stretched molecular chains into amorphous state rather than realignment into crystal form I predominating the crystal transition process.
基金financially supported by Shandong Provincial Key R&D Program (No. 2015GGX102019)the Taishan Scholar Program
文摘In this work, the crystallization of immiscible polypropylene （PP）/polybutene-1 （PB） blends, in particular the effect of crystal morphology of PP （HTC, high Tm component） on the subsequent crystallization behavior of PB （LTC, low Tm component） was studied. Herein, we firstly indicated that PP/PB blends were not completely compatible but characterized as the LCST-like phase diagram above the melting temperature of PP. Crystallization of PP at different crystallization temperatures brought about different PP crystal morphologies and PB was segregated and confined at different locations. Much larger-sized domain of PB component appeared in PP spherulites resulting from the effects of non-negligible phase separation and the slower PP crystallization rate as PP crystallized at high temperature. As temperature continued to fall below Tm of PB, the fractionated and confined crystallization of PB occurred in the framework of PP spherulites, reflected by the decreased crystallization temperature （To） of PB and the formation of form I＇ beside form II. Notably, if PP previously crystallized at high Tc, fractionated crystallization of PB became predominant and confined crystallization of PB became weak due to the much wider droplet-size distribution of PB domains.
