Investigations On The Miscibility,Structure And Properties Of Polyoxymethylene(POM)/Poly(butylene Succinate)(PBSU) Blends

Owing to abundant crystallization morphologies and complex microstructures,miscible crystalline/crystalline polymer blends have attracted increasingly attention in recent years.In this work,the miscibility,crystallization behaviors and mechanical properties of polyoxymethylene(POM)/poly(butylene succinate)(PBSU)blends were first investigated.Besides,the films with oriented-paralleled banded spherulites structure on the surface were fabricated by applying shear field.The formation mechanism and wettability of such structure were further investigated.The main content of this paper includes:Part one,investigations on the miscibility of POM/PBSU blends.The POM/PBSU blends were miscible in the melt and presented as homogeneous melts.The miscibility derived from the interaction between the methylene groups of POM molecules and carbonyl groups of PBSU molecules.After the crystallization of blends from the melt,the blends exhibit an interfibrillar structure.It was further found that the blends have two each other shifted glass transition temperatures.We attributed the glass transition temperature to the relaxation of the amorphous region in each crystal bundle.Part two,investigations on the crystallization behaviors of POM/PBSU blends.Due to the large difference in melting temperature of POM and PBSU,characteristic stepwise crystallization behaviors were observed in POM/PBSU blends.When cooling from the homogeneous melts,POM crystallized first and formed the volume-filled banded spherulites.The growth rate and band spacing of POM banded spherulites were influenced by the composition of blends.After the complete crystallization of POM,the PBSU crystallization took place.It was found,in the blends that PBSU content > 50 wt%,the crystallization rate of PBSU was much faster than that of neat PBSU due to the nucleation effect of POM crystals on PBSU crystallization.However,when the PBSU content < 50 wt%,with the decreasing of PBSU interconnectedness in blends,the crystallization of PBSU was inhibited or even stopped,and the crystallization rate was gradually decreased.Part three,investigations on the mechanical properties of POM/PBSU blends.In the blends that POM content > 30 wt%,the PBSU could highly increase the toughness of POM,and POM could increase the using temperature of PBSU.When the content of POM ranged from 3-10 wt%,the blends exhibited unexpected brittleness.It was found that POM can form loose crystal networks in the blends.Due to the nucleation effect of POM crystals on PBSU crystallization,the PBSU crystallized into less-connected tiny spherulites in POM crystal networks.When the external force was applied on the blends,due to the weak POM crystal network and less-connected PBSU spherulites,the blends were very weak and brittle.When the content of POM in blend was 1 wt%,the blend was ductile and depicted a mechanical behavior similar to that of neat PBSU,as the POM crystallized into tiny crystals due to the extremely low content.Part four,fabrication of the oriented-paralleled banded spherulites structures and its application.The oriented-paralleled banded spherulites structures on the thin films of POM/PBSU blends were successfully fabricated via shear field.It was found that such structure was highly influenced by the shearing temperature and shearing rate.When shearing with a lower shearing temperature and a higher shearing rate,the orientation of the chains at the shearing interface was much higher and thus formed compact POM nucleation sites.With the increasing POM nucleation densities,the morphologies of POM banded spherulites transformed from the semicircle to fanshaped,and finally to cylindrites.The wettability of such structure was close to that of the unoriented banded spherulites.After increasing the altitude difference between the valley and peak of the banded spherulites by selected etching,the hydrophilicity of surface was increased,while the shearing had little effect on the wettability of the surface.