Is the engineering plastic polyamide suitable for use in high temperature environments?

The applicability of engineering plastic polyamide (nylon) in high temperature environments needs to be comprehensively judged based on material modification technology and actual working conditions. The key points of its high temperature characteristics are as follows:

1. Basic temperature resistance limitations
Pure polyamide molecular chains are prone to melting and softening at sustained high temperatures, while conventional unmodified grades (such as PA6/PA66) have a long-term usage temperature limit of about 80 ℃. When the temperature exceeds this limit, the rigidity of the material drops sharply, and the gears are prone to creep deformation, resulting in a loss of meshing accuracy.

2. Modification and strengthening methods
High temperature tolerance can be improved through the following techniques:
Fiberglass reinforcement (GF): By adding 30% -50% glass fiber, the thermal deformation temperature can exceed 200 ℃, significantly suppressing high-temperature creep.
Mineral filling: fillers such as talc powder and mica block thermal insulation and slow down the overall softening rate.
Heat resistant copolymerization modification: Introducing semi aromatic polyamides (such as PA6T, PA9T) or poly (phthalamide) (PPA), with strong molecular chain rigidity and long-term temperature resistance up to 150-180 ℃.

3. Short term peak tolerance
Fiberglass reinforced polyamide can withstand instantaneous high temperature impact (such as 180 ℃ -230 ℃ for several minutes), suitable for intermittent hot environments such as automotive engine compartments, but it is necessary to strictly avoid continuous overheating operation.

4. Risk of high temperature lubrication failure
When the temperature exceeds 120 ℃:
Self lubricating additives (MoS ₂/PTFE) may oxidize and fail, leading to a sharp increase in friction coefficient.
Molecular chain activity intensifies and accelerates wear, requiring the use of high-temperature resistant special lubricants (such as polyimide micro powder).

5. Impact of humid and hot environment
Polyamide has hygroscopicity, and in high temperature and high humidity environments (such as injection molding machines and steam equipment):
The plasticizing effect of water intensifies material softening, resulting in a decrease of 20-30 ℃ in actual temperature resistance.
Thermodynamic testing verification must be conducted under humid and hot conditions.

6. Thermal aging life attenuation
Continuous exposure to high temperatures can lead to:
Molecular chain oxidation leads to chain breakage and material embrittlement and cracking.
The dynamic fatigue strength decreases, and the risk of gear tooth breakage increases.
Component lifespan needs to be estimated through accelerated aging experiments.

Principles of Industrial Application
Scenario above 150 ℃: Priority should be given to using heat-resistant plastics or metal gears such as PPS and PEEK.
120-150 ℃ range: Limit the use of glass fiber reinforced PA66 or PPA, and design a safety factor of over 20%.
Below 80 ℃: Conventional polyamide is safe and does not require modification.