Study On MC Nylon Modified With Laurolactam

Synthetic method of MC nylon modified with laurolactam was presented. Copolymer of caprolactam with laurolactam was prepared by activated anionic copolymerization under adiabatic condition. Effect of MC nylon modified on its properties was systematically studied. The structure of the copolymer was established by DSC , DMA and a polarizing microscope. The depndence of properties on the amount of laurolactam was also examined.The course of the anionic copolymerization of caprolactam with laurolactam depends on the reaction mechanism. The conditions of reaction were established for the adiabatic copolymerization of the two lactams below the melting point of the product. Sodium hydroxide was used as catalyst as well as activator concentrations were 0.25mol%. The initial temperature of the copolymerization was 130℃.The mp values of copolymers were established from DSC measurements and the crystalline phase content was determined from the area of endothermic melting peaks. The crystalline copolymer of caprolactam with laurolactam exhibits only one melting peak at the new melting temperature, decreasing with comonomer concentration. Thus, It can be assumed that random copolymer are formed. The decrease of the crystallinity by influence of the copolymerization is cuased. The shape of endothermic melting peak in the DSC curve also offers information on the crystalline phase structure. A low and wide peak measured with the copolymer suggests that the crystallites are characterized by a wide distribution of melting points, irregularly developed, and disturbed by high content of amorphous chains.The dynamic modulous G' and mechanical damping tanδ of the copolymer were measured by the free vibration method on a torsion pendulum. The polyamide is characterized by one relaxation process, α -maximum. This process is attributed to motions of long segments of the chain in the amorphous regions. From increase of thea-maximum intensity and its shift to lower temperature, it can be assumed that the copolymerization leads not only to increasing the amorphous phrase content, but also to changing the structure of the amorphous phase where a lower concentration of hydrogen bonds makes possible a larger mobility of the chains. Ta varies with the concentration of comonomer. A remarkable decrease in Ta was found for the content of 10 mol% of laurolactam in the copolymer. Thus, it can be suggested that an addition of 10 mol% of the comonomer shows a remarkable plasticizing effect on MC nylon.The morphological structure was established by a polarizing microscrop. MC nylon's morphogical structure is relatively regular. MC nylon modified with 10 mol% laurolactam has very well-developed spherulites although the spherulitic structure is less regular. In the presence of 30 mol% laurolactam in the copolymer, the spherulitic structure is disturbed remarkably by action of a high portion of amorphous regions that limit spherulite growth.Change in mechanical properties occur as a result of the copolymerization of caprolactam with laurolactam. It was obvious from the examination that the notched impact strength and deformability are increased with the increase in laurolactam content of the copolymer. The yield stress of copolymer drops with increasing concentration of comonomer in accordance with the decrease in the crystallinity. Thanks to a higher content of the amorphous phase, and to changes in amorphous phase structure and mouphologic structure, the ductile-brittle transition of MC nylon modified with laurolactam was shifted to more severe impact conditions, i.e. to a lower temperature or higher strain rate.