Preparation And Foaming Properties Of Polyamide 1212 Elastomer/Polyurethane Composites

Polymer foams cover almost all fields of industrial production and life due to their light weight,high specific strength,excellent heat and sound insulation properties and superior cushioning performance.Recently,thermoplastic polyamide elastomer（TPAE）foams have attracted much attention because of their excellent fatigue resistance,flexural resistance,high elasticity and low-temperature toughness widely used in sports equipment,and have become a new hot spot in the footwear industry,but they are expensive and only used in high-end footwear materials,so it is important to prepare TPAE foams with excellent performance and low price.In this paper,a new thermoplastic polyamide elastomer（TPAE1212）with different molecular weights of hard and soft segments was synthesized by a simple"two-step"melt polycondensation reaction using dodecanediamine,dodecanedioic acid and polybutylene glycol as raw materials,and then melt blended with TPU to prepare TPAE/TPU composites in order to limit the crystallization of hard segments of polyamide and reduce the production cost.Finally,the chain extender ADR was added to improve the compatibility and melt strength of the composites,and the composites were treated with supercritical CO₂foaming to prepare the corresponding foams.（1）Long carbon chain thermoplastic polyamide elastomers（TPAE1212）with polyamide 1212（PA1212）as the hard segment and polybutylene glycol（PTMG）as the soft segment were successfully synthesized.The results showed that the prepared TPAEs have good toughness and thermal properties.Due to the restriction of PA1212crystals and low melt strength,CO₂ could not diffuse sufficiently within the melt,and the prepared TPAE showed poor foaming properties,and only at higher foaming temperatures,a small number of bubble holes existed in TPAE with more soft segments.（2）Thermoplastic polyurethane（TPU）was added to compensate for the high cost of TPAE,while reducing the crystallization of the hard segment of polyamide and improving the foaming performance,and the foaming behavior was significantly improved because TPU limited the crystallization of the hard segment of TPAE.When the TPU content increased to 30%,the number of cells in the foaming material increased and the foaming properties improved,but the low melt strength and poor interfacial compatibility were not enough to support the growth of cells,which collapsed or ruptured during the growth process leading to the inability to form a superior cell structure.（3）The chain extender ADR was introduced to improve the melt strength and interfacial compatibility of TPAE/TPU composites.It was found that the melt strength and interfacial compatibility of the composites were significantly improved after modification by chain spreading,and the composite foams showed more perfect cells structure,higher cell density and expansion ratio.With the increase of ADR content,the cell size and expansion ratio of TPAE70%/TPU30%composite foam showed a trend of first increasing and then decreasing.The maximum cell size of 25.81μm was achieved when the ADR content was 2%,and the composite foam was proved to have excellent resilience by cyclic compression test.