The Crystal Properties Of High And Low Molecular Weigh Polyethylene Oxide And Their Blend

Biodegradable material polyethylene oxide (PEO) is a easily crystallizableof thermoplastic water-soluble polymer. PEO materials can be used in medicine,paper printing, oil, building materials, agriculture, municipal construction and soon. It has attracted more and more attention. The crystallization properties ofPEO are important for its use. This paper mainly focus on the crystallizationdifference of the different molecular PEO and their blends to broaden the PEOapplication. The main researches are as follows:In this paper,10k PEO and200k PEO were used. The differences innonisothermal crystallization and isothermal crystallization of PEO and its blendswere observed from DSC. The experiment proved that the blends had a faster crystallization rates, shorter crystallization time, the crystallinity increase withthe increase of10k PEO content and the onset temperature increase in thenonisothermal crystallization. In the isothermal crystallization, it was also foundthat crystallization time of the blends became short, the crystallization ratespeeded up, the crystallization beginning time bring forward. The Avrami index nwere not change, so crystallization mechanism is unchanged.This paper made a series of experiments to explain the reason of the aboveresults. XRD proved PEO blends had the same crystal form as pure component.Therefore, the nucleation and growth mechanism mainly were researched. XRDand POM experiments show that the number of PEO blends nucleation pointswere in the middle of the pure component. Compared with10k PEO,200k PEOchain period of density fluctuations were violent, and were more apt to nucleate.So it is inferred that PEO blends nucleate by200k PEO component. AFM showedthat the lamellae melt from the middle section, other than melt in region. Hence,the conclusion that both components entered the same lattice to form a cocrystalcan be drawn. POM picture illustrated the10k PEO grows at a higher rate at thesame crystallization temperature, and the blends spherulite growth rate curveexist intermediate of the two pure PEO. Low molecular weight PEO owns ahigher kinetic coefficient of growth and smaller diffusional limitations. So10kPEO plays a solvent effect to make chain movement better in blends, andtherefore chain fold and arrangement were easier than pure200k PEO. The crystallinity of blends was higher than pure200k PEO, and increased with theincreased of the content of10k PEO.In short, PEO blends nucleated by200k PEO, and then chains of the blendsfolded to form cocrystal.10k PEO plays a solvent effect to make a fasterspherulite growth rates and higher crystallinity than that of pure200k PEO. Thehigher nucleation capability, faster spherulite growth rates of PEO blends madethe crystallization peak temperature Tp of the nonisothermal crystallization bringforward and half crystallization time of isothermal crystallization become shorter.