Why PTFE Is Called the "King of Plastics"

PTFE (Polytetrafluoroethylene) has a molecular backbone tightly wrapped in a layer of fluorine atoms, forming an inert shell of extremely low surface energy. This brings three highly valuable engineering properties: an extremely low friction coefficient, a "non-stick" surface that adheres to almost nothing, and strong chemical inertness—apart from a few high-temperature strong oxidizers, it barely reacts with acids, alkalis or solvents. That is why it is widely used in non-stick cookware, seals, bearing bushings, and self-lubricating coatings for fasteners.

On fasteners, PTFE is usually not "solid plastic" but is applied as a dry-film lubricant coating, together with a binder resin and solid-lubricant fillers, onto the thread surface and cured into a thin, uniform film. YF Zhichengjia's polymer dry-film lubrication system uses an eco-friendly lubricating resin with nano solid-lubricant powder, low-temperature cured with no oil residue; it can penetrate fine thread gaps and improve fine-thread screw jamming and assembly catching.

Applied to Threads: How Non-Stick and Low Friction Work

When a thread is tightened, relative sliding occurs between the bolt and nut flanks and roots. The traditional approach relies on grease to "separate" two metal surfaces at the contact; but grease attracts dust, soils the assembly line, and evaporates and dries out over time. The PTFE dry-film idea is completely different: it pre-cures a solid lubricant film on the thread surface, and the PTFE particles squeezed between the contact faces during tightening act as "solid ball bearings", turning direct metal-on-metal friction into low-friction metal-PTFE-metal sliding.

The so-called "non-stick" property is essentially PTFE's extremely low surface energy making it hard for glue, oil and resin to adhere; at the same time the film separates the mating faces of seizure-prone materials such as stainless steel, preventing cold welding. For 304/316 stainless fasteners, this is one of the effective means to solve assembly locking and seizure.

What makes this different from oil is durability: oil is consumed, sheared out, and dries, so its friction coefficient drifts over the service life and across batches; a PTFE dry film is there from the start and stays there, so the joint behaves consistently on the first assembly and the fifth. That consistency is what automated assembly lines—where every tightening cycle must land in the same torque window—actually buy when they pay for a coated fastener.

Friction Coefficient, Temperature Range and Chemical Inertness: Performance Boundaries

When engineers choose a PTFE coating, the three numbers they care about most are the friction coefficient, the temperature range, and its effect on the torque coefficient.

PTFE Coating vs Oil Lubrication vs Other Dry Films

Historically there are three main routes for fasteners to reduce friction and prevent seizure, each with its own boundaries:

• Oil lubrication / oiling: lowest cost, but easily attracts dust, contaminates cleanrooms, dries out over time, and has large friction-coefficient scatter; not suited to automated lines and high-purity environments.
• PTFE dry film: oil-free, clean, stable friction coefficient, chemical-resistant and wide-temperature; suited to electronics, medical, food equipment and automated assembly. But under extremely high contact pressure and ultra-low-speed creep, its load capacity is weaker than molybdenum disulfide.
• Molybdenum disulfide (MoS2) / graphite dry film: better suited to heavy load, boundary lubrication and vacuum; MoS2 has high load-bearing pressure, while graphite relies on atmospheric moisture to work.

In short: for cleanliness, low friction, anti-stick and anti-seizure choose PTFE; for heavy load, boundary lubrication and vacuum choose molybdenum disulfide. The two are also often combined to balance low friction with high load capacity.

Typical Applications and Selection Recommendations

• 3C electronics and AI-server micro screws: require dust-free, oil-free, smooth automatic driving; an ultra-thin PTFE dry film avoids thread jamming and catching.
• Stainless-fastener anti-seizure: 304/316 bolts prone to cold welding under high temperature and repeated disassembly; the PTFE film separates the mating faces.
• Food, medical and clean equipment: PTFE is chemically inert, non-toxic and non-stick, with no oil contamination.
• Wide-temperature service: stable self-lubrication from cryogenic up to about 260°C.
• Where precise preload is needed: after choosing a PTFE dry film, redo the torque-clamp-force test and set tightening torque from the measured K factor.

One practical caveat: because PTFE has such low surface energy, secondary bonding or sealing against the coated surface can be difficult—designers should not expect paint, threadlocker or gaskets to adhere well over the film. The film is excellent at making the joint slide and stay clean, but it should be seen as a tribological layer, not a bonding surface. In production, batch-to-batch friction consistency matters far more than chasing the lowest possible absolute μ, which is why measured torque-coefficient data should always accompany the coating specification.