A method for monomer copolymerization to promote ip-1-b to form i' crystal directly from melt

Abstract

The invention discloses a method for promoting iP-1-B to form I' crystals directly from melt through monomer copolymerization. Propylene and 1-butylene copolymer is subjected to heating heat preservation and cooling, meanwhile, the melt crystallization behavior of the copolymer is observed in situ through wide-angle X-ray scattering, it is found that only II crystals formed by the copolymer and homopolymerized iP-1-B are different, a small number of I' crystals can be generated while the II crystals are mainly formed, then in the multi-time cyclic heating and cooling process that the temperature is raised to 125 DEG C and then reduced to 30 DEG C, more crystal forms I' can be generated by the propylene monomer copolymerized iP-1-B obviously compared with the homopolymerized iP-1-B, along with increase of 30-125 DEG C cyclic heating and cooling frequency, the proportion of the generated I' crystals is increased, and the method is simple in process and easy to operate.

Description

technical field [0001] The invention belongs to the technical field of polymer processing, and more specifically relates to a method for promoting iP-1-B to form I' crystal directly from a melt through copolymerization of a small amount of monomers. Background technique [0002] Isotactic poly-1-butene (iP-1-B) is a thermoplastic resin belonging to the semi-crystalline polyolefins known for its good mechanical properties, outstanding creep resistance, low temperature flow resistance and environmental stress cracking resistance Durability, wear resistance, flexibility and high filler filling, etc., known as "plastic gold", currently mainly used in hot water pipes, synthetic fibers, food packaging, medical equipment and other fields. As a polycrystalline polymer, iP-1-B crystallizes under different conditions to form five different crystal forms I, II, III, I', and II', of which the crystal form II is a thermodynamically metastable tetragonal crystal, and the molecular chain ...

AI Technical Summary

Problems solved by technology

However, it should be noted that when the comonomer content is relatively high, the comonomer can introduce more structural defects in the iP-1-B molecular chain, which can directly form a thermodynamically stable I' crystal from the melt, and also It will change the crystalline form and reduce the crystallinity, thermal stability and melting point, etc., and will be affected to a certain extent in terms of comprehensive mechanical properties, especially the tensile modulus and strength will be lower

Therefore, as far as the prior art is concerned, the homopolymer iP-1-B is not easy to directly form a thermodynamically stable crystal structure from the melt, while the copolymer containing a high content of comonomer can directly form part or all of the thermodynamically stable crystal structure from the melt. Stable crystalline structure, but its comprehensive mechanical properties are restricted, and often can be obtained directly from the melt such as I' crystal at a lower melting temperature

Images