Chemical Resistance of Common Engineering Plastics

Chemical Resistance of Common Engineering Plastics

Introduction: why chemical resistance matters for Engineering Plastic applications

Chemical resistance directly affects the longevity, safety, and total cost of ownership for parts made from Engineering Plastic. Choosing the right polymer prevents unexpected failures, costly downtime, and regulatory issues in industries such as chemical processing, oil & gas, food handling, medical devices, and automotive. This article explains how common engineering plastics behave in contact with acids, bases, solvents and oils, and provides practical selection guidance you can use today.

Common engineering plastics covered

This guide reviews the most widely used engineering plastics: PTFE (Teflon), PEEK, PVDF, POM (acetal / Delrin), Nylon (PA6/PA66), Polycarbonate (PC), ABS, PPS, PET, UHMWPE, PVC and HDPE/PP family. Each material has distinct chemical resistance profiles, mechanical properties and service temperature limits that determine suitability for specific environments.

How chemical resistance is evaluated

Chemical resistance depends on concentration, temperature, contact time, mechanical stress and the presence of other chemicals (synergy). Standard tests include immersion (ISO, ASTM methods), stress cracking evaluation, and permeation testing. Ratings in this article are generalized (Excellent/Good/Fair/Poor) and intended for preliminary selection; always consult specific chemical compatibility charts and perform application-level testing.

Quick reference: comparative chemical resistance table

The table below summarizes typical resistance of common Engineering Plastic materials against representative chemical groups. Ratings reflect bulk material behavior at ambient to moderate temperatures (<60°C) unless otherwise noted.

Notes on the resistance table and real-world caveats

The table is a high-level guide. For example, PTFE resists nearly all chemicals at ambient temperatures but will not withstand fluorine gas or molten alkali metals. PVDF is widely used in chemical piping for acids and some solvents but can be attacked by certain chlorinated solvents at elevated temperature. Nylon absorbs moisture which can change dimensional stability and mechanical strength. Always verify with manufacturer chemical compatibility charts and perform immersion and stress tests at expected operating temperatures and concentrations.

Service temperature ranges and how temperature affects chemical resistance

Temperature accelerates chemical attack and diffusion. Typical continuous service temperatures (approximate): PTFE up to ~250–260°C, PEEK up to ~250°C, PVDF up to ~150°C, PPS up to ~200°C, Nylon up to ~120°C (reduced by moisture), POM up to ~100°C, UHMWPE up to ~80°C, PC up to ~120–135°C (glass transition). When choosing an Engineering Plastic for a hot chemical environment, select materials whose continuous use temperature exceeds the process temperature and confirm chemical compatibility at that elevated temperature.

Mechanical stress, permeation and stress cracking

Combined mechanical load and chemical exposure can cause environmental stress cracking (ESC) even when static immersion tests look favorable. Materials like HDPE and ABS are particularly susceptible to ESC in presence of certain solvents. Permeation is another issue for seals and thin films; a material rated as 'Good' for bulk resistance might still allow slow permeation that is unacceptable for barrier applications.

Selection checklist for engineering plastic chemical compatibility

Use this checklist when selecting an Engineering Plastic: 1) Identify chemicals, concentrations and temperatures; 2) Determine contact type (immersion, splash, vapor); 3) Evaluate mechanical loads and pressure; 4) Review long-term aging and UV exposure; 5) Consult supplier compatibility data and request sample testing; 6) Consider coatings, composites or liners if a single polymer cannot meet all requirements.

Enhancements: fillers, coatings and blends to improve resistance

Modifiers and coatings can boost performance. Fluoropolymer coatings and liners (PTFE, FEP) provide excellent chemical barriers. Glass or carbon fiber reinforcement increases strength and temperature capability (e.g., PEEK-CF). Toughened blends and specialty grades with antioxidants or flame retardants can extend service life in specific environments. However, additives may change chemical resistance — for example, plasticizers or certain fillers can degrade resistance to oils or solvents — so test final formulations.

Design and manufacturing considerations for chemical service

Design choices matter: thicker sections reduce permeation but increase residual stresses; seamless liners reduce leak paths; proper mating of dissimilar materials avoids galvanic-like incompatibilities. Manufacturing methods (injection molding, machining, extrusion, over-molding or insert molding) can affect surface finish and micro-cracks that initiate chemical attack. For sealing applications, consider elastomer compatibility (Viton, EPDM, PTFE seals) alongside rigid Engineering Plastic choices.

Applications and commercial use cases for engineering plastics

Typical uses where chemical resistance is critical: pump components, valve seats, seals, piping, fittings, tanks and liners, heat exchangers, sensor housings and gaskets. For example, PTFE and PVDF are common in aggressive acid handling systems; PEEK is favored for high-temperature, high-pressure valve parts and aerospace components; UHMWPE is used for wear surfaces in contact with oils and slurries.

Bost: strengths and product portfolio in Engineering Plastic solutions

Bost is a professional and innovative high-tech green energy engineering plastics manufacturer specializing in R&D, production and sales. Bost focuses on high-quality engineering plastic sheets, rods and molded parts with specialized properties: ultra-high anti-scar, super corrosion resistance, superior fatigue durability, ultra abrasion resistance and high-temperature transparency. The company excels in material modification, toughening, flame retardancy and conductive/thermal property enhancement. Bost's strong R&D and production teams deliver integrated services including mold design, machining, and composite steel-plastic assemblies. This makes Bost well-suited for industries demanding customized Engineering Plastic solutions, fluoroplastics, over-molding and insert molding, as well as specialized rubber seal integration.

Bost's main product advantages: Engineering Plastic, Fluoroplastic, Over Molding and more

Bost provides a range of advantages: Engineering Plastic products optimized for wear and chemical resistance; Fluoroplastics (PTFE, FEP, PFA-like solutions) offering broad chemical inertness; Over Molding and Insert Molding services that ensure robust bonding and leak-free assemblies; Special Engineering Plastics with tailored mechanical and thermal properties; and integrated rubber seals designed for superior chemical compatibility. Bost combines material science, precise molding and machining to produce components that reduce maintenance and increase system uptime.

Practical example: choosing a material for a chemical pump seat

For a pump seat exposed to 30% hydrochloric acid at 60°C and occasional hydrocarbon splashes: PVDF offers excellent acid resistance and mechanical properties, but if temperatures or abrasive solids are higher, PTFE with a wear-resistant backing or PEEK (if higher temperature and mechanical load) may be preferred. Bost can provide over-molded designs combining a PTFE sealing surface with a tougher PEEK or glass-reinforced polymer backing to balance sealing, wear and dimensional stability.

Conclusion: match environment, mechanics and manufacturing

Selecting the right Engineering Plastic requires balancing chemical compatibility with temperature, mechanical load and manufacturing constraints. Use compatibility charts as a starting point, but validate with application-specific testing. For complex or critical applications, work with experienced suppliers like Bost who can customize materials, molding and seal solutions to meet both chemical and mechanical requirements.

FAQ: Which Engineering Plastic resists strong acids best?

PTFE and PVDF are top choices for mineral acids. PTFE gives the broadest chemical inertness; PVDF offers a more economical option with good mechanical strength. Confirm at the target concentration and temperature.

FAQ: Can I use POM (acetal) in contact with fuels and oils?

POM typically performs well with aliphatic hydrocarbons, fuels and oils at ambient temperatures. However, POM is vulnerable to strong acids, chlorinated solvents and ketones. Test for long-term exposure and pressure conditions.

FAQ: Is Nylon suitable for outdoor chemical applications?

Nylon can be used outdoors, but its hygroscopic nature changes dimensions and mechanical strength. UV exposure and certain chemicals (strong acids/alkalis) can further degrade performance. Consider protective coatings or alternative polymers if dimensional stability is critical.

FAQ: How should I test a chosen Engineering Plastic for my process?

Perform accelerated immersion tests at the expected temperature and concentration, stress-cracking tests under expected mechanical loads, and permeation tests for seals. Evaluate thermal aging and any cyclic exposure scenarios. Work with material suppliers to get standard test data and request custom testing as needed.

FAQ: When should I consider fluoroplastics like PTFE?

Choose PTFE when unmatched chemical inertness, very low friction, and wide temperature tolerance are required. PTFE is ideal for aggressive chemistries, but it can be more expensive and has lower mechanical stiffness than some engineering thermoplastics; often used with backing materials or as a lining/coating.

FAQ: Can additives or fillers change chemical resistance?

Yes. Fillers, plasticizers and flame retardants can alter permeation and chemical interactions. Reinforcements like carbon or glass fiber generally improve mechanical and thermal properties but may change chemical exposure behavior at the surface or create galvanic concerns in metal-plastic interfaces. Always test the exact formulation used in production.