Preparation And Mechanical Properties Of Polydopamine Modified Inorganic Fiber Reinforced Polyamide 6 Composites

Fiber reinforced polyamide 6 composites have excellent corrosion resistance,durability,mechanical properties,high specific strength,high specific modulus,easy processability,recyclability,and lightweight,making them widely used in large-scale fields such as automotive manufacturing,building reinforcement,aerospace,and sports and leisure.The poor interfacial compatibility between fiber and polyamide 6 resin limits its application in more demanding fields.The interfacial bonding quality between fibers and resin matrix dominates the performance of composite materials.A better interfacial bonding quality leads to a higher stress transfer efficiency,which has a significant impact on the mechanical properties of composite materials.However,most methods for fiber modification have limitations such as complicated experimental steps,easy to damage the structure and strength of the fiber itself.Based on the above drawbacks,this paper aims to increase the surface roughness and chemical activity of fibers,this paper constructs a simple,mild and effective interface layer to improve the interface binding force between the fiber and polyamide 6 resin matrix,so as to improve the overall mechanical properties of the composite material without damaging the mechanical properties and structure of the fiber itself.The main research contents are as follows:(1)Carbon fiber was modified by dopamine self-polymerization coating and then used to fabricate carbon fiber reinforced polyamide 6 composites(CF/PA6).The surface of carbon fiber treated by modification is covered with a uniform PDA film,which notably increased the surface activity,roughness and chemical bonding capacity of carbon fiber.The interfacial compatibility between carbon fiber and polyamide 6 resin matrix was substantially improved.The composite with PDA treatment for 16 h showed the highest interfacial adhesion strength,with an interlaminar shear strength of 31.7MPa,which rose by 72.3% compared to that before modification.The flexural strength reached 308.2 MPa,which rose by 56.9% compared to that before modification.(2)A composite coating of PDA and hexagonal boron nitride(h-BN)was coated on the surface of glass fiber to prepare glass fiber reinforced polyamide 6 composite(GF/PA6).The surface roughness,activity and chemical bond energy of glass fiber were significantly increased by treating it with a composite coating of PDA and h-BN,which greatly enhanced the interfacial interlocking effect between glass fiber and polyamide 6resin matrix.The addition of composite coating also induced PA6 to change its crystal type from γ type to α type.The composite material with 0.75% h-BN content showed the best mechanical properties,with a tensile strength of 129.8 MPa(79.2% higher than before modification),a bending strength of 194.8 MPa(32.2% higher than before modification)and a storage modulus of 1742 MPa(69.9% higher than before modification).To sum up,this paper presents a method of modifying inorganic fiber surface that offers a novel approach for designing interfacial layers that are simple,mild and effective in enhancing the mechanical performance of fiber-reinforced composite.