Preparation And Properties Of Copolyamide 6/1012

Polyamide 6(PA6)is a wide range of synthetic fiber and plastic raw materials with excellent wear resistance,solvent resistance and good mechanical properties.However,the toughness,especially at low temperature,it can not meet the requirements for use in harsh environments.Long carbon chain polyamide has high flexibility of molecular chain,low content of amide bond and hydrogen bond,and is superior to the former in toughness and low moisture absorption.But the cost of manufacture is high,and the domestic production process is not mature.Long carbon chain amide copolymerization modification of PA6 is an important method.PA6 was copolymerized with Nylon 1012 salt in this work is in order to improve the polymer's overall mechanical qualities.One of the monomers in Nylon 1012 salt is decanediamine,which comes from the renewable resource castor oil,so the introduction of polyamide 1012(PA1012)with PA6as the main body can reduce the production cost and has good environmental benefitsThe synthesis of Nylon 1012 salt was studied,and the Nylon 1012 salt with better thermal stability was determined by means of ~1H NMR,FT-IR,TGA and wide-angle X-ray diffraction.The effects of polymerization temperature,duration,and end capping agent amount on the reaction degree of copolyamide 6/1012(PA6/1012)were explored in details,and a controlled preparation with relative viscosity between 2.46-4.01 has been achieved.The effects of various concentrations of 1012 amide monomer on polymerization degree,crystallization and melting behavior,rheological characteristics,and mechanical properties of PA6/1012 were investigated on this basis.The results show:the extractable content reduced as the number of 1012 amide monomers increased;the sequence structure of copolyamide tends to be random as the number of 1012 amide monomers increases;and the glass transition temperature(T_g)of copolyamide drops monotonously.When the concentration of 1012 amide monomer is less than 21%,the melting temperature(T_m)drops monotonously as the concentration rises.When the concentration exceeds 21%,the melting point range decreases dramatically.Furthermore,as the melting peak changes from a single to a double peak,the strength ratio of the main peak to the sub peak drops,which is connected to the size and quantity of spherulites.The crystal morphology obtained with a polarized microscope demonstrates that by increasing 1012 content,spherulite radius and amount would decrease accordingly.When the concentrations of 1012 amide monomer is greater than 21%,imperfect crystals take precedence,and spherulites become scarce and tiny.The non-isothermal crystallization kinetics of PA6/1012 was analyzed by Jeziorny method and Mozhishen method.In the early crystallization stage,Avrami index n was between 2 and 3,and the crystal growth mode was the superposition form of one-dimensional fiber growth,two-dimensional disk growth and three-dimensional spherical growth.In addition,the influence of1012 amide monomer content on the non isothermal crystallization activation energy of the copolymer was calculated and compared by Kissinger method.Compared with the non isothermal crystallization activation energyof pure PA6(-25.09 kj/mol),the figure of PA6/1012 can be increased to-9.88 kj/mol.The rheological properties of three different PA6/1012 copolymerization ratios(including pure PA6)were investigated.The results show that PA6/1012 belongs to a pseudoplastic non-Newtonian fluid in the temperature range of 260-280?,with a non-Newtonian index of0.72-0.76 and a structural viscosity index of 0.85-0.94;the viscous flow activation energy of PA6/1012 is 13.6-26.9 k J/mol at a shear rate of 62.5-4 000 s^-1.The introduction of 1012 can effectively improve the fluidity of copolymer melt.Based on the above results about T_g,T_m,T_c(crystallization temperature)and rheological properties,the injection molding process and post-treatment process suitable for PA6/1012 with different copolymerization ratios were discussed and determined.Under diverse test settings,the effects of copolymerization ratio on the tensile,bending and impact properties of the samples were compared.The results showed that the tensile strength,tensile modulus,flexural strength and flexural modulus decreased by increasing of 1012 amide monomer content,while the elongation at break and impact strength increased significantly.PA6/1012 can enhance elongation at break by91%when the tensile strength declines by no more than 12%in a low temperature and low humidity environment(the tensile property values of pure PA6 are 68.38 MPa and 46.06%).PA6/1012 can also increase the elongation at break by 202%when the tensile strength decreases by no more than 15%in a normal temperature and high humidity environment(the tensile property parameters of pure PA6 are 57.13 MPa and 101.06%);In three environments of low temperature and low humidity,normal temperature and high humidity,and ultra-low temperature and low humidity,the notched impact strength of PA6/1012 was increased to 5.53 k J/m~2,10.35 k J/m~2,and4.26 k J/m~2respectively.