Morphologies And Properties Of Polyamide 6 Film After Hydrothermal Treatment

Water can be considered as the most abundant,cheap,safe and environmentally liquid medium and solvent around the world.Under ambient condition,water shows strong polarity with density 1.0 g/cm³,dielectric constant 79.3,and ionic product 10^-14.Many chemical species cannot dissolve in water at room temperature and atmosphere pressure.When temperature>374? and pressure>22.1 MPa,water is in supercritical state.Higher than ambient boiling temperature and less than 374? water is in super-heated state.In super-heated state or supercritical state,dielectric constant,conductivity,ionic product,viscosity,heat capacity,diffusion coefficient,density and even the structure of the H-bond network of water tremendously change compared with ambient water.Therefore,supper-heated or supper-critical water can be used as solvent,chemical regent or catalysis.Polyamide?PA?is a type of important synthetic material.Some aliphatic polyamide can dissolve in the supper-heated water and their crystallization forms are easily transformed by the influence of the external environment,indicating that there is possibility to use water as solvent to processing polyamide.Polyamide 6?Nylon 6?,widely used for plastics and fiber industry,melts at225?,while in the supper-heated water it melts and dissolve at 160?.In dissolved state,polyamide will hydrolyze,and the hydrolysis strengthens as the treating time prolonged and the temperature elevated.When the temperature further increased to make water into supercritical state,polyamide would decompose to monomers.In this paper,we studied the hydrothermal treatment of biaxially oriented polyamide 6 film?BOPA?in the temperature region before dissolving.Different characterization and measurement were used to investigate the structural generation and performance variation of BOPA,which included scanning electron microscopy?SEM?,thermal analysis?DSC?,X-ray diffraction?XRD?,T-peel strength test and so on.The conclusions of the study are as follows:1.After hydrothermal treatment?130-160??,there are nano-structured pattern formed on the surface,and the pattern has the characteristics of crystalline morphology.2.XRD and FT-IR characterization indicated that before and after hydrothermal treatment,the crystal structure of PA6 kept to be?form3.In the temperature region?140-160??as the hydrothermal temperature elevates,the crystalline degree of the film will further increase.4.After hydrothermal treatment,the initial modulus of the film is constant,the toughness increases and the tensile strength decreases.The printing and compound performance of the film surface are increased.The permeability and oxygen barrier of the film decreased slightly.From the conclusions above,we known that the superheated water is a good etchant for PA6,it can dissolve or remove unstable amorphous parts and reveal the surface crystalline morphology of the film.After hydrothermal treatment,the crystallization was protected and improved,the adhesion of the film surface increases obviously and the film is not seriously damaged.