Reaearch On Crystallization Behavior And Mechanism Of PES/PEO Polymer Blends

It has been reported that polymer blending could improve the physical and mechanical properties of polymers, enhance work-ability, reduce production costs and expand the scope of application. Polymer blending has been extensively used to obtain the comprehensive performance of ideal polymer materials.In the crystalline/crystalline blend system,the main factors of influencing the material performances are crystallization behavior and crystal morphology of mixing.However, the crystalline polymers can form a variety of crystal morphology due to its nature, different admixture, co-polymerization and crystallization conditions. In this work, we mainly discussed the polymer blend system of the PES/PEO by using the method of ultra low concentration solution of isothermal crystallization. The crystal nucleation and morphology under different temperature the samples was examined by atomic force microscope(AFM) in tapping mode in details.Single crystals were grown using the self-seeding method to produce small and uniform crystals. Blends of PVDF and PBS were prepared by solution blending. Both of them were dissolved in DMF, which serves as a common solvent, with concentration of 5×10-6g/ml.Thin films for AFM observations were prepared by casting on glass slides, to studied under different crystallization temperature and component ratio,crystallization behavior and crystal morphology.When PES/PEO(40/60) and PES/PEO(50/50), in a wider temperature range, PES and PEO form a uniform laminar crystals simultaneously. PES is lozenge crystals and PEO is square shape crystals.PES crystal began melting phenomenon at 60℃ and the crystallization behavior of PEO single crystal more lower melting temperature than PES single crystal, which began to melt at 40℃. PEO can form a regular flaky crystal at 25-40℃, but PEO crystal begins to melt at over 40℃, and PES has been in regular shape single crystal exists at 25-60℃. In the melting process, the melting behavior of PEO and PES is all from the lamellar crystal of the edge to the crystal interior and the lamellar thicknessincreases. This is mainly due to the polymer lamellar thickness is thin in metastable state, and the surface area of folded chain can be reduced by increasing the lamellar thickness, thus the crystal in a more stable state by reducing the surface energy of crystal.To further study the crystallization behavior of PES/PEO(40/60) and crystal morphology of three different polymer blends. PES crystal formed multilayer diamond crystal with opposite spiral direction at 25℃, which is mainly due to the existence of screw dislocation. When the defect concentrated in the interior of the wafer, due to the factors internal stress and lattice dislocation, will form multilayer lamellae with spiral dislocation like PES. When the growth front of PES and PEO single crystal contact with each other, they will have three different crystallization behavior and crystal morphology in compatible blend system. On the one hand, When they are in contact with each other, PEO and PES are simply superimposed together to grow independently and maintain their own crystal morphology; On the other one,Because the faster crystallization time and diffusion ability of PEO crystals, and will enter the PES crystals by growth, which is similar to the spherulite of high concentration. And then PES crystals will change the crystallization direction continued to grow until fully crystallized according to the growth direction of the PEO crystals. Finally, forming the crystal morphology with a PEO-PES-PEO sandwich structure, which due to the collapse of the polymer chain in the two crystal pieces.