Effects Of Additive TAB-1 On The Crystallization And Transition Behaviors Of Isotactic Polybutene-1

Isotactic Polybutene-1(i PB-1)has excellent physical and mechanical properties,but the application is limited by it’s special crystal transition.It will first form metastable crystal form II when cooling from the melt,and form II spontaneously transits to stable crystal form I.This process is inevitable and time-consuming,which severely restricts the industrial application of i PB-1.In this paper,an additive(trade name TAB-1)with good compatibility with i PB-1was selected.The effect of TAB-1 on the crystallization behavior of i PB-1,especially the crystal transition behavior,and the mechanical properties were studied using polarizing microscope,DSC,X-ray technology,and stretching hot stage.After testing the samples with TAB-1 concentration of 0-5wt%,we found that the additive TAB-1can effectively accelerate the crystal form transition,and the transition rate is accelerated as the concentration increases.After mixing with TAB-1,the thermal stability of the material is enhanced,and the mechanical properties are almost unchanged,indicating that TAB-1 is a good additive suitable for adding to the processing process to solve the crystal form transition problem.It was also found that the total crystallinity of form II and form I increased in the initial stage of the transition,the "more stable" form II crystallized at higher temperatures transformed into form I faster than the "less stable" form II crystallized at low temperatures,and the transition rate is not affected by the cooling temperature,which are not consistent with the widely accepted solid-solid transition theory.According to the temperature conformation selection and the melting point changes of the two crystal forms during the transition,this paper proposes and discusses a more possible mechanism of the transition.The direct formation of form I in the amorphous region destroys the original equilibrium state and becomes the driving force for the transition.There is a packed-mesophase state during the transition process between form II and form I,and the key of the transition is form Ⅱ to packed-mesophase.