Polyhexamethylene adipamide, abbreviated as MXD6 in English, is generally referred to as “nylon MXD6”. Compared with other engineering plastics, this resin has higher mechanical strength and modulus. It is also a special high-barrier nylon material. Although the barrier property of MXD6 is slightly inferior to that of PVDC and EVOH, it is not affected by temperature and humidity, making it particularly suitable for use in high-temperature and humid environments. In the current trend of barrier packaging and plastic replacing steel, nylon MXD6 has become one of the notable new plastic varieties.
Structural properties: PA MXD6 nylon material has high strength, high rigidity, high heat distortion temperature, and a small coefficient of thermal expansion; it has good dimensional stability, low water absorption, and little dimensional change after water absorption, with little change in mechanical strength; it has a very small molding shrinkage rate, suitable for precision molding processing; it has excellent coating performance, especially suitable for surface coating at high temperatures; it has excellent barrier properties against oxygen, carbon dioxide and other gases.
Advantages of nylon MXD6:
1. Maintains high strength and high rigidity over a wide temperature range.
2. High heat distortion temperature and small coefficient of thermal expansion.
3. Low water absorption, little dimensional change after water absorption, and little reduction in mechanical strength.
4. Very small molding shrinkage rate, suitable for precision molding processing.
5. Excellent coating performance, especially suitable for surface coating at high temperatures.
6. Excellent barrier properties against oxygen, carbon dioxide and other gases.
Mold temperature and drying conditions for molding nylon MXD6
For high-performance nylon MXD6 injection molding, it is recommended to select a relatively high mold temperature (mold surface temperature of 120 to 140°C). If molding is done at a mold temperature of around 80°C, annealing treatment (at 130°C for about 1 hour) is required after molding to increase the crystallinity of the molded product, thereby ensuring strength and rigidity. Additionally, in a moisture-absorbed state, abnormal phenomena such as silver streaks (silver color) may occur on the surface of the molded product. It is recommended to perform hot air drying (at 80°C for more than 12 hours or at 120°C for more than 4 hours) before molding.
Application fields of MXD6
MXD6 in the plastic modification industry application
MXD6 can be compounded with glass fiber, carbon fiber, minerals and/or advanced fillers, and is used in materials with 50-60% glass fiber reinforcement, offering extraordinary strength and rigidity. Even when filled with a high content of glass fiber, its smooth, resin-rich surface can form a high-gloss surface free of glass fiber, making it extremely suitable for painting, metal plating or creating naturally reflective shells.
1. Excellent flowability for thin walls
MXD6 is a resin with extremely high flowability. Even when the glass fiber content is as high as 60%, it can easily fill thin walls with a thickness of only 0.5 mm.
2. Superior surface finish
The perfect surface of MXD6, rich in resin, has a highly smooth appearance, even with a high glass fiber content.
3. High strength and stiffness
When 50-60% glass fiber reinforcement is added to MXD6, its tensile strength and flexural strength are similar to many cast metals and alloys.
4. Good dimensional stability
At ambient temperature, the coefficient of linear thermal expansion (CLTE) of MXD6 glass fiber composites is close to that of many cast metals and alloys. Due to low shrinkage and the ability to maintain tight tolerances (if molded properly, the length tolerance can be as low as ±0.05%), it has strong reproducibility.
MXD6 is used to replace metals in making high-quality structural components for automobiles, electronics and electrical appliances.
In automotive parts, many applications require materials with high mechanical strength, good oil resistance, and the ability to be used for long periods at temperatures ranging from 120 to 160°C. Glass fiber reinforced MXD6 has a heat resistance of up to 225°C, maintains high strength at high temperatures, and can be used in engine blocks, cylinder heads, pistons, and timing gears of automobiles. MXD6/PPO alloys possess high-temperature resistance, high strength, oil resistance, wear resistance, and good dimensional stability, making them suitable for vertical outer panels of car bodies, front and rear mudguards, wheel covers, and curved parts that cannot be formed by stamping steel plates, as well as for automotive chassis.
The Application of MXD6 in Barrier Fields
The application in high-barrier packaging materials shows great potential for development. Food packaging is mainly used in the form of PET/MXD6 blends for bottle-making, for the packaging of wine, beverages, medicines and food. Cushioning materials are used for shockproof packaging of precision instruments, meters and valuable items.
PET/MXD6 multilayer bottle
The bottle is formed by injection molding with two materials, PET resin and MXD6, and then extended blow-molded into a multi-layer bottle. The structure of the PET/MXD6/PET multi-layer bottle has high transparency and excellent gas barrier performance, effectively preventing the infiltration of oxygen and the loss of carbon dioxide. It can meet the requirements of products with high barrier performance, such as high-concentration fruit juice, tea, beer, carbonated beverages and functional beverages.
2. PET/MXD6 single blend bottle
Bottles made by blending PET and MXD6 are called single-mix bottles. The molding process of single-mix bottles is simple and can be produced using conventional machines without issues such as delamination or peeling. Single-mix bottles have excellent gas barrier properties, but their appearance is not completely transparent, with a hazy layer similar to the color of pearls. Single-mix bottles with 5% MX nylon added have a shelf life twice that of ordinary PET bottles.
3. Film
NYLON-MXD6 is suitable for the production of multi-layer and blend films. Due to its superior barrier performance under high humidity conditions, good processability and excellent thermal stability, MXD6 is the preferred barrier material for nylon 6 multi-layer films, nylon 6 blend films and PET blend films. Whether it is multi-layer films or single blend films, adding a certain amount of MXD6 can effectively improve the gas barrier property of the films.