What are Short-chain and Long-chain Polyamides
Polyamides with less than 10 carbon atoms in their chains are generally referred to as short-chain polyamides (or short-chain nylons), such as polyamide 6 (PA6), polyamide 66 (PA66), and polyamide 46 (PA46). Polyamides with 10 or more carbon atoms in their chains are called long-chain polyamides (or long-chain nylons), such as polyamide 610 (PA610), polyamide 612 (PA612), polyamide 1012 (PA1012), and polyamide 12 (PA12). Due to the lower amide bond content in long-chain polyamides, they have lower water absorption, better dimensional stability, and better ductility compared to short-chain polyamides.
PA12 Applications and Alternatives
PA12, a type of long-chain polyamide, is mainly used in automotive components, 3D printing, machinery, and aerospace. In automotive components, glass fiber (GF)-reinforced PA12 is primarily used in fuel line systems, automotive evaporation systems, and quick connectors. Currently, the technology for injection molding of PA12 and its modified materials is mainly held by foreign modification companies, such as Arkema in France, Evonik in Germany, and Ube Industries in Japan. Although domestic research on PA12 resins and their modified materials has been conducted, there is no industrial production of PA12 resins in China yet. Therefore, the price of PA12 materials in China is still very high, hence the research and development of PA12 alternative materials has significant practical significance. Additionally, long-chain polyamides made from partially or fully bio-based materials, such as PA610, PA612, and PA1012, have environmental advantages over PA12, which is derived from non-renewable fossil fuels.
Fuchen New Material‘s Research
Fuchen New Material has compared the properties of three materials: GF30-reinforced PA612, PA1012, and PA12, all with a glass fiber content of 30%. They also conducted trial production on the mold of a mass-produced automotive fuel line quick connector to compare the performance of these materials. This research provides a basis for the subsequent development of alternatives to PA12/GF30 materials using other types of reinforced long-chain polyamides.
Summary of Key Points
(1) The tensile strength, bending strength and bending elastic modulus of PA612/GF30 materials are the best, followed by PA1012/GF30 materials, and the worst is PA12/GF30 materials.However, whether it is the notch impact strength at room temperature or low temperature, PA1012/GF30 material is the best, PA12/GF30 material is the second, and PA612/GF30 material is the worst.
(2) The order of material density, thermal deformation temperature, and melting point from high to low is: PA612/GF30, PA1012/GF30, PA12/GF30.The shrinkage rate of the three GF-reinforced long-chain polyamides is the same, and the water absorption rate is low, which is not much different, but the appearance of the products injected from PA1012/GF30 material is better than that of PA612/GF30.
(3) Based on the performance of the material and the injection molding situation, PA1012/GF30 material is the most economical alternative to PA12/GF30 material.
Material Preparation
The raw materials PA612 and PA1012 were dried at 100℃ for 4h, and the relevant materials were weighed according to the ratio of the resin matrix, GF and antioxidant mass fractions of 69.8% and 30% of 0.2%, respectively. The resin and antioxidant were first added to the vertical mixer and mixed evenly, and then added to the co-directional twin-screw extruder. Melt and squeeze out, GF is added by side feeding.Then the extruded strips are cooled by water and dried by a hair dryer, and the pellets are granulated by a granulator.The temperature of the feeding section of the extruder is 230~250℃, the temperature of the melting section is 210~230℃, the temperature of the head section is 230~250℃, and the host screw speed is 350~380r/h.
After the prepared pellets are dried, a standard spline is prepared by an injection molding machine.The temperature is 230～260℃, the decompression is 80mpa, and the time is 35s.Drop P12/GF30 at 100℃ for 4 hours.
Main Results
(1) Mechanical properties
The picture below shows the force-increasing performance described by GF.The tensile strength, bending strength and bending elastic modulus of PA612/GF30 materials are the best, followed by PA1012/GF30 materials, and the worst is PA12/GF30 materials.The tensile strength, bending strength and bending elastic modulus of PA612/GF30 material are 50, 50MPa and 1 200 MPa higher than that of PA12/GF30 material, respectively.The tensile strength, bending strength and bending elastic modulus of PA1012/GF30 material are 16, 15Mpa and 400MPa higher than that of PA12/GF30 material, respectively.However, whether it is the notch impact strength at room temperature or low temperature, PA1012/GF30 material is the best, PA12/GF30 material is the second, and PA612/GF30 is the worst.
Bending Elastic Modulus Comparison
Bending Strength Comparison
Notch Impact Strength Comparison
Tensile Strength Comparison
GF enhances the performance differences of different long-chain polyamides mainly due to the different molecular structures of long-chain polyamides.The molecular structure of different long-chain polyamides is shown in the figure below.As the content of the amide group increases, the symmetry of the molecular chain increases and the crystallinity increases, its strength also increases; on the contrary, as the content of the amide group decreases (the increase of the methyl group in the polyamide molecular chain), the strength gradually decreases and the compliance increases.
a—PA12；b—PA1012；c—PA612
(2) In the practical application of engineering plastics, especially for the surrounding materials of automobile engine parts, special attention needs to be paid to the thermal deformation temperature of the materials.The picture below shows the thermal deformation temperature of GF reinforced different long-chain polyamides.It can be seen that the highest thermal deformation temperature of PA612/GF30 material is 185℃, followed by PA1012/GF30 material, which is 175℃, and the worst is PA12/GF30 material, which is 160℃.This may be due to the fact that PA612 has the highest amide content and the largest crystallinity, resulting in the highest thermal deformation temperature.The higher thermal deformation temperature means that the material can be used in auto parts with higher temperature requirements.
Thermal Deformation Temperature Comparison
(3) Comparison of actual injection molded products
Taking a quick-coupling injection molding product of an automobile evaporation system as an example, the molding quality of three GF-reinforced long-chain polyamide materials was compared on the injection molding machine. The injection molding process is shown in Table 1.Table 2 shows the actual comparison of the molding quality of GF reinforced different long-chain polyamide injection molded products.As can be seen from Table 2, the dimensions of PA612/GF30 and PA1012/GF30 meet customer requirements, but the appearance of PA1012/GF30 is better than that of PA612/GF30.This may be due to the fact that the melting point of PA612/GF30 material is higher than that of PA1012/GF30. Under the same injection molding conditions, the fluidity of PA1012/GF30 material is better.In addition, products made by PA1012/GF30 are 0.1g heavier than products made by PA12/GF30, while products made by PA612/GF30 are 0.5g heavier than products made by PA12/GF30.Judging from the performance of the material and the actual injection molding situation, PA1012/GF30 is the most economical material to replace PA12/GF30.
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