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PREPARATION AND PROPERTIES OF PA66/6
- Jan 21, 2019 -

PA66 and PA6 are the most productive and widely used varieties in PA products, and they have excellent properties. However, the higher melting point and narrow processing temperature range of PA66 and the lower impact strength of PA6 will limit their application in some fields. If PA66/6 is prepared from adipic acid hexamethylene diamine salt (AH Salt) and caprolactam (CPL) by copolymerization modification, the application field of PA66/6 will be broadened by combining their excellent properties.

At present, the research on PA66/6 at home and abroad mostly focuses on the single system with CPL or AH Salt as the main raw material, and the modification of the ratio of CPL and AH Salt in a small range. Donghua University uses melt polycondensation method to prepare PA66/6 with full range of PA66/6 using AH Salt and CPL as raw materials. The structure and properties of PA66/6 are systematically studied in order to provide the necessary theory for the development and application of PA66/6 products. On data.

The raw materials used are as follows

AH Salt, CPL: Industrial Grade, Basf (China) Co., Ltd.

Adipic acid (ADA): Analytical Purity, Chemical Reagent Co., Ltd. of China Pharmaceutical Group;

Deionized water (H2O): Self-made.

The sample was prepared in this way.

According to the formula in Table 1, raw materials are added into the high temperature and high pressure reactor, and nitrogen is injected for 15 min to discharge the air in the reactor; after exhaust, the closed reactor is closed, stirring is opened at a speed of 100 r/min, and the temperature rises to 210 r~220 C within 1 h, keeping the pressure between 1.8 MPa and 1.85 MPa during the period; after pressure-holding, the exhaust valve is opened, and the pressure is released to 0 MPa at about 1_h, then the temperature rises to 20_25_C; The pressure from empty to autoclave is - 0.5 MPa, which further improves the degree of copolymer polymerization. Then PA66/6 particles are obtained by casting strip and pelleting. PA66/6 was extracted in a constant temperature water bath at about 100 ~C for 48 h to remove unreacted caprolactam monomers and oligomers. The extracted copolymers were dried in a blast oven at 60 ~C for 24 h to remove surface moisture. The extracted and dried PA66/6 was placed in a vacuum drying chamber at 105 (?) C for 24 h to remove the residual moisture in the amorphous area of its surface and structure. The drawing spline was prepared by injection moulding machine. The temperature of the mould was 30 C, the temperature of the barrel was about 20 C higher than the melting point of the sample, the injection pressure was 0.9 MPa, and the holding time was 10 s.

The performance summary is as follows

(1) The introduction of copolymer reduces the regularity of PA66/6 molecular chain and intermolecular force. The molecular structure of PA66/6 is dominated by alpha crystal. When the mass ratio of AH Salt to CPL is close to 1:1, it is beneficial to form unstable gamma crystal.

(2) During the copolymerization process, with the addition of the second monomer, the melting point, crystallinity and tensile strength of the prepared PA66/6 decreased gradually, but the elongation at break increased and the thermal stability was good.

(3) When the mass ratio of AH Salt to CPL is 40:60, the melting point of PA66/6 decreases to 169.7 C, the crystallinity is 16.2%, the tensile strength is 33.9_MPa, but the elongation at break increases to 122.9%, which is higher than that of pure PA66 and pure PA6. It shows that copolymerization can improve the processing performance and toughness of PA66/6 effectively.