Properties Of Nylon (PA) Materials

Properties of nylon (PA) materials

Introduction to Nylon

Nylon (Nylon, Polyamide, PA for short) refers to plastics composed of polyamide resins. Such resins can be produced by polycondensation of diamines and dicarboxylic acids, or by ring-opening polymerization of amino acids formed after dehydration of the lactam. Unlike PS, PE, PP, etc., PA does not soften gradually with the increase in heat temperature, but softens in a narrow temperature range near the melting point, which is very pronounced, and the melting point is 215-225°C. Once the temperature is reached, it appears to flow. Flow occurs once the temperature is reached.

There are many varieties of PA, mainly Pa6, Pa66, PA610, PA11, PA12, PA1010, PA612, PA46, PA6T, PA9T, MXD-6 aromatic amides and so on. PA6, PA66, PA610, PA11, PA12 are the most commonly used.

Nylon engineering plastics are presented in the appearance of angular, tough, bright surface, white (or milky white) or yellowish, transparent or translucent crystalline resin, it is easy to be written into any color. The molecular weights of nylons as engineering plastics are generally 15-30 thousand. Their densities are slightly greater than 1, density: 1.14-1.15g/cm3. tensile strength: > 60.0MPa. elongation: > 30%. flexural strength: 90.0 MPa. Bending strength: 90.0 MPa. Notched impact strength: (kJ/m2) ＞ 5. The shrinkage rate of nylon is 1% to 2%.

Dimensional changes due to moisture absorption after molding should be noted. Water absorption 100% 8% when saturated with relative moisture absorption. Operating temperature: -40~105°C. Melting point: 215~225°C. Melting point: 215~225℃. Suitable wall thickness 2~3.5mm. PA mechanical properties such as tensile and compressive strength with temperature and moisture absorption and change, so water is relatively PA plasticizer, adding fiberglass, its tensile and compressive strength can be increased by about 2 times, the ability to withstand the temperature is also increased accordingly, the PA itself is very high abrasion resistance, so it can be operated non-stop without lubrication, such as want to get special lubrication effect, you can add sulfide in the PA. If you want to get special lubrication effect, you can add sulfide into PA.

The main advantages of PA performance

1. High mechanical strength, good toughness, high tensile and compressive strength. Than the tensile strength is higher than the metal, than the compression strength and metal is not similar, but it is not as rigid as metal. Tensile strength is close to yield strength, more than twice as high as ABS. Impact, stress vibration absorption ability, impact strength is much higher than the general plastic, and better than Acetal resin.

2. Outstanding fatigue resistance, the parts can still maintain the original mechanical strength after repeated folding. Common escalator handrails, new plastic bicycle rims and other cyclical fatigue role is very obvious occasions often apply PA.

3. High softening point, heat-resistant (such as nylon 46, high crystallinity nylon heat distortion temperature is high, can be used for a long time at 150 degrees Celsius. PA66 after glass fiber reinforced, its heat distortion temperature reaches more than 250 degrees Celsius).

4. Smooth surface, small coefficient of friction, wear-resistant. For the activity of mechanical components, self-lubricating, low noise, in the friction role is not too high when can not add lubricants to use; if you really need to use lubricants to reduce friction or to help dissipate heat, then the water oil, grease and so on can be selected. Thus, it has a long service life as a transmission part. 5.

5. Corrosion resistance, very resistant to alkali and most salt solutions, but also resistant to weak acids, oil, gasoline, resistant to aromatic compounds and general solvents,, inert to aromatic compounds, but not resistant to strong acids and oxidizing agents. It is resistant to gasoline, oil, fat, alcohol, weak alkali, etc. and has good anti-aging ability. It can be used as packaging materials for lubricants, fuels, etc.

6. Self-extinguishing, non-toxic, odorless, good weather resistance, inert to biological erosion, good antibacterial, anti-mold ability.

7. Excellent electrical properties. Good electrical insulation, nylon volume resistance is very high, high breakdown voltage, in a dry environment, can be used as frequency insulation, even in high humidity environment still has good electrical insulation.

8. Light weight, easy to dye, easy to mold. Because of low melt viscosity, it can flow quickly. Easy to fill the mold, filling the mold after the solidification point is high, can be quickly shaped, so the molding cycle is short, high production efficiency.

The main disadvantages of PA properties

1. Easy to absorb water. Water absorption, saturated water can reach more than 3%. To a certain extent affects the dimensional stability and electrical properties, especially thin-walled parts of the thickening of the greater impact; water absorption will also greatly reduce the mechanical strength of the plastic. In the selection of materials, should take into account the use of the environment and other components with the impact of precision. Fiber reinforcement can reduce the resin water absorption rate, so that it can work in high temperature, high humidity. Nylon and glass fiber affinity is very good. Commonly used in the production of combs, toothbrushes, coat hooks, fan bones, mesh bags, rope, fruit bags and so on. Non-toxic, but not long-term contact with acid and alkali. It is worth noting that, after adding glass fiber, the tensile strength of nylon can be increased by about 2 times, and the temperature resistance is also improved accordingly.

2. Poor light resistance. In the long-term high-temperature environment will be oxidized with the oxygen in the air, the beginning of the color brown, followed by broken surface cracking.

3. Injection molding technology requirements are more stringent: the presence of trace amounts of water will cause great damage to the molding quality; due to thermal expansion so that the dimensional stability of the product is more difficult to control; the existence of sharp corners in the product will lead to stress concentration and reduce the mechanical strength; wall thickness, if uneven will lead to distortion, deformation of the parts; after processing the parts of the high precision requirements of the equipment.

4. Will absorb water, alcohol and dissolve, not resistant to strong acids and oxidizers, can not be used as acid-resistant materials.