Preparation And Foaming Properties Of Thermoplastic Polyamide 6 Elastomer Composites

In recent years,thermoplastic polyamide elastomers（TPAEs）foamed materials have overcome the shortcomings of other elastomer foamed materials,such as poor durability of ethylene vinyl acetate copolymer（EVA）and high density of thermoplastic polyurethane elastomer（TPU）.Its application in footwear industry has drawn much attention.The current popular TPAEs in footwear foamed materials are polyamide 12（PA12）based TPAEs,however,they are expensive and are usually used in high-end footwear.In TPAEs,thermoplastic polyamide 6 elastomers（PA6 series TPAEs）have the wide raw material sources,low price and excellent performance,which have great application potential in the footwear industry.In this paper,PA6 series TPAEs were prepared by dibasic acid method,and long afterglow luminescent materials were added to endow them with luminescent function.Finally,the corresponding foamed materials were prepared by supercritical CO₂foaming technology.The main research contents were as follows:（1）Using PA6 as the hard segment and PEG（polyethylene glycol）as the soft segment,TPAEs with different soft segment molecular weights（300,600 and 1000）were synthesized.The results showed that with the increase of the molecular weight of the soft segment,the tensile strength and thermal stability decreased gradually,the elongation at break increased gradually,the crystallinity and crystallization rate decreased gradually,and the phase separation became more obvious.When the molecular weight of the soft segment was 600,the tensile strength and elongation at break were（35.50±3.54）MPa and（316.05±20.58）%,respectively.Combined with the above results,PA6 series TPAEs with excellent comprehensive performance and soft segment molecular weight of 600 were selected as the matrix for the following research.（2）Green,blue and orange noctilucent PA6 series TPAEs composites were prepared by in situ polymerization using different kinds of long afterglow luminescent materials as fillers.When the filler was Sr Al₂O₄:Eu²⁺,Dy³⁺,the composite materials emitted green light.With the increase of filler content,the tensile strength,thermal stability and crystallinity of the composite materials increased first and then decreased,and reached the maximum value when the filler content was 1.5 wt%.The afterglow time and luminous brightness increased with the increase of filler content,and the afterglow time were 36 min,75 min,125 min and 148 min respectively.When the fillers were Sr₂Mg Si₂O₇:Eu²⁺,Dy³⁺and Y₂O₂S:Eu³⁺,Mg²⁺,Ti⁴⁺,the composites emitted blue and orange light,respectively,in the dark environment,and the afterglow time was 34 min and 10 min respectively（the content was 1.5 wt%）.（3）PA6 series TPAEs foamed materials were prepared by supercritical CO₂foaming technology.The results showed that the cell structure of PA6 series TPAEs was better when foaming pressure was 10 MPa and foaming time was 2 h.Based on this process condition,the effect of foaming temperature on the foaming properties of composite(filler was Sr Al₂O₄:Eu²⁺,Dy³⁺,1.5 wt%)was studied.At 175℃,the average cell size reached the maximum（47.12μm）,the expansion rate was as high as 8.54 and the cell density was 2.33×10⁸cells/cm³.The foaming properties of different kinds of long afterglow luminescent composites were studied under this foaming condition.The prepared PA6 series TPAEs long afterglow foamed material not only had good resilience,but also emitted green,blue and orange light in the dark environment,and had broad application prospects in luminous shoe materials and other fields.