Study On Mechanism Of Enhancement Of Solvent Vapor Treatment On Phase Transition Of Polybutene-1

Isotactic polybutene-1 has high commercial potential in the fields of pipe and film as a high performance polyolefin material with many advantages such as abrasion resistance,torsional resistance,creep resistance and chemical corrosion resistance.The product made in the industrial process is metastable crystal type I,It has to take several days to convert to stable crystal type I,to get better performance stability.This long time crystal conversion process influence the production and inventory,increases production costs,has to be improved to broaden the market.In order to obtain the stable crystal I structure as soon as possible,scientists have explored many methods,including using copolymerization,blending,mechanics,atmosphere,and solvent methods,achieved many different crystal transformation promoting effects.solvent vapor treatment is found to be an effective method,but the problem what kind of solvent has an effect on the acceleration effect,and the effect of solvent properties on acceleration haven`t been thoroughly studied.In this paper,the effect of solvent vapor treatment conditions on the crystal transformation of polybutene-1 materials was systematically researched by in-situ wide-angle X-ray diffraction,two-dimensional X-ray diffraction analysis and differential scanning calorimetry(DSC)analysis.Firstly we research the effect of thickness of PB-1 resin sample on the crystal transformation process of solvent fumigation,The effect of the thickness of PB-1 on the crystal transition from PB-1 type II to I during solvent fumigation was in-situ characterized by two-dimensional X-ray diffrotometry,tested the whole process of n-hexane crystal transformation by four kinds of PB-1 thicknesses with in-situ fumigation attachment,comparing the rate of crystal II disappearance and the rate of crystal I formation with the time required,building a linear relationship between the thickness and the time required for crystal transformation.The results show that,the shorter the sample thickness is,the shorter the phase transition time is.On the contrary,the larger the sample thickness is,the longer the phase transformation time is,the sample thickness is proportional to the transformation time.Then we explore the Effect of solvent type on crystal transition of PB-1,chose the crystal type II PB-1 samples obtained by isothermal crystallization of 50?,and fumigate them with different solvents steam,In combination with the results of the analysis researched by DSC and in-situ XRD,researching the II-I phase transformation of PB-1 by solvent fumigation.The result shows that,except water and alcohol solvent,most other solvents such as n-hexane,chloroform,1,2-dichloroethane,benzene,toluene,xylene,chlorobenzene,ethyl acetate,tetrahydrofuran,acetone solvent has obvious promoting effect for phase II-I change process,can make the crystal transformation that normally completed in four to five days accelerated to dozens of minutes.During the solvent fumigation Crystal II disappears along wsith crystal I,The acceleration effect of solvent mainly depends on the geometrical size of solvent molecule,besides small size of single direction corresponds to the larger acceleration effect.On the basis of the toxicity and cost performance of the solvent,alkanes are the better solvent to promote the II-I phase transformation process of polybutene-1 material.