Preparation,Structure And Properties Of PA6/PA66 Copolyamide And Its Fibers

Nylon（Nylon）is a polyamide thermoplastic resin,also known as PA.Because of its high strength,abrasion and impact resistance,PA is widely used in engineering plastics,synthetic fibers,plastic films,coatings and adhesives.One of the most common PA-like materials is PA6,which is widely used in automotive products,such as heater boxes,radiator blades,body parts and airbags.PA6 is widely used in bearings,various rollers,fan blades and worm gears in industry and manufacturing.PA6 is also mainly used in textile clothing to make underwear,socks and cord fabrics.Although PA6 has the above excellent characteristics,there are also many deficiencies,such as: low resin toughness,transparency,and fiber collusion retention rate.Therefore,PA6 in the production of transparent film,filter,collusion fabric is restricted.In order to improve the performance of PA6,this paper reviews the research methods and progress of modified PA6 in recent years,and chooses to melt polycondensation of PA66 with PA6 to achieve the improvement of PA6 transparency,toughness and hook strength.The structure and properties of PA6/PA66 copolyamides and its fibers were also investigated with a view to broadening the application range of PA6.The main research contents of the paper are as follows:1.Adipic acid（ADA）and hexanediamine（HMDA）were used as raw materials,and equimolar ADA and HMDA were dissolved in anhydrous ethanol to form adipic acid hexanediamine salt（AH Salt）.Fourier infrared（FTIR）spectroscopy was performed on AH Salt,and the FTIR spectrum showed that adipic acid adipamide salt was successfully synthesized.2.Adipic acid hexanediamine salt,caprolactam（CPL）,amino caproic acid（ACA）and deionized water are added to the high temperature autoclave in different mass ratios for melt polycondensation reaction.A series of PA6/PA66 copolyamides were successfully synthesized.Nuclear magnetic resonance hydrogen spectroscopy（1H-NMR）and Fourier Conversion Infrared Spectroscopy（FTIR）test results show that PA6/PA66 copolyamide was successfully synthesized.The viscosity test results show that the relative viscosity of PA6/PA66 copolyamide prepared by adding AH Salt with different mass fractions are almost maintained between 2.1 and 2.6,which can meet the needs of subsequent processing.The differential scanning calorimetry（DSC）test results show that the glass transition temperature,melting temperature and crystallinity of PA6/PA66 copolyamide decrease with the increase of AH Salt content.The thermo gravimetric analysis（TGA）test results show that the higher the AH Salt content in the nitrogen atmosphere,the lower the initial decomposition temperature of PA6/PA66 copolyamide,but it is much higher than the fiber spinning temperature,which has no great influence on subsequent spinning processing.The ultraviolet transmittance results show that with the increase of AH Salt content,the light transmittance can reach up to 93%,which is more than 10%higher than PA6;The mechanical properties test results show that with the increase of AH Salt content,the fracture strength of PA6/PA66 copolyamide shows a downward trend,but the elongation at break is greatly improved.When the AH Salt mass fraction is 30%,the elongation at break reaches 494.5%,which is more than 4 times higher than PA6.It shows that the copolymerization modification of PA6 with the addition of AH Salt can greatly improve the toughness and transparency of PA6.3.The isothermal and non-isothermal crystallization properties of PA6/PA66 copolyamides were investigated using DSC.The crystallization rate and crystallization time were calculated by using Avrami equation and Jeziorny model,respectively.The results showed that the crystallization rate of PA6/PA66 decreased,the crystallization time became larger,and the activation energy of crystallization decreased as the addition of AH Salt gradually increased.From the theoretical aspect,it is explained that the addition of AH Salt reduces the crystallization ability of PA6 and the transparency increases significantly4.PA6/PA66 copolyamide fibers with AH Salt mass fractions of 10% and 20% were prepared by spinning PA6/PA66 copolyamide using melt spinning method.The structural properties of the fibers were tested and analyzed using an acoustic velocity orientation meter,an X-ray diffractometer,an eight-basket constant temperature oven and a yarn tensiometer.The results showed that due to the introduction of AH Salt copolymer monomer,the molecular chain regularity of PA6/PA66 decreased,the crystallinity,orientation and breaking strength of the fibers decreased,and the rewetting rate of the fibers increased.the knot strength ratio and breaking elongation retention rate of PA6/PA66 copolyamide fibers increased significantly compared with those of PA6 fibers,indicating that PA6/PA66 copolyamide fibers can significantly improve the knot strength ratio and toughness of PA6 fibers,which is suitable for knotted fabrics.