Selecting the correct resin is the foundation of successful part performance in manufacturing. With over 85,000 commercial options available, engineers must navigate a complex hierarchy of polymers ranging from commodity resins to ultra-high-performance thermoplastics. This guide provides a structured material selection matrix comparing industry standards like Acrylonitrile Butadiene Styrene (ABS), Polycarbonate (PC), Polyamide (PA/Nylon), and Polyether Ether Ketone (PEEK).

What are the Key Parameters for a Plastic Material Selection Guide?

A robust plastic material selection guide¹ categorizes resins based on their polymer morphology (amorphous vs. semi-crystalline) and their performance tier. The selection matrix generally filters materials through four primary lenses: Thermal Performance, Mechanical Strength, Chemical Resistance, and Cost.

The Polymer Pyramid Hierarchy

How Do ABS and Polycarbonate Properties Compare?

When designing enclosures, consumer electronics, or automotive interiors, the debate often settles on ABS vs Polycarbonate properties².

아크릴로니트릴 부타디엔 스티렌(ABS) is an amorphous polymer known for its toughness, ease of machining, and excellent surface finish.
폴리카보네이트(PC) is a transparent amorphous thermoplastic known for extreme impact resistance and higher heat deflection.

Comparative Data: ABS vs. PC

참고: For applications requiring the processability of ABS and the strength of PC, a PC/ABS blend is often used.

What Are High-Performance Thermoplastics and When Should They Be Used?

High-performance thermoplastics³ are defined by their ability to maintain mechanical properties at elevated temperatures (continuous use >150°C) and resist harsh chemicals.

Polyamide (PA/Nylon) vs. Polyether Ether Ketone (PEEK)

1. Polyamide 66 (PA66): A semi-crystalline engineering plastic. When reinforced with glass fibers (GF), PA66 rivals metals in structural rigidity. However, it is hygroscopic (absorbs moisture), which affects dimensional stability.
2. Polyether Ether Ketone (PEEK): The apex of the polymer pyramid. It offers exceptional chemical resistance, hydrolysis resistance (steam), and high-temperature performance.

Performance Data Matrix

How to Interpret an Injection Molding Resin Chart?

An injection molding resin chart⁴ provides technical data points that dictate processability. To use these charts effectively, follow this stepwise selection process:

1. Identify Thermal Constraints: Look at the Heat Deflection Temperature (HDT). The material must withstand the application’s maximum temperature without warping.
2. Determine Mechanical Load: Check Tensile Modulus (stiffness) and Yield Strength. If the part bears weight, prioritize glass-filled variants.
3. Assess Environmental Exposure: Consult chemical resistance charts. Amorphous resins (PC, ABS) are generally prone to stress cracking from solvents; Semi-crystalline resins (Nylon, PEEK, PP) offer better resistance.
4. Review Shrinkage Rates: High shrinkage materials (like PEEK or POM) require precise mold design considerations compared to low shrinkage materials (ABS, PC).

What are the Considerations for Medical Grade Plastics?

Selecting medical grade plastics⁵ introduces regulatory and sterilization variables beyond standard mechanical properties.

Key Regulatory Standards

• USP Class VI: The strictest testing tier for biocompatibility under US Pharmacopeia.
• ISO 10993: The global standard for biological evaluation of medical devices.

Sterilization Compatibility Table

What are the Practical Pros and Cons of Common Thermoplastics?

What are the Typical Application Scenarios?

• 자동차:
  • Interiors: ABS, PC/ABS (Dashboards, buttons).
  • Under-the-hood: PA66 GF30 (Engine covers, air intake manifolds).
• 소비자 가전:
  • Housings: PC, PC/ABS (Laptops, phone cases).
  • 커넥터: LCP (Liquid Crystal Polymer) or PBT.
• 의료 기기:
  • Disposables: PP, PS (Syringes, petri dishes).
  • 수술 도구: PEEK, PPSU (Handles, retractors).
• Industrial/Aerospace:
  • Gears/Bearings: POM (Acetal), Nylon.
  • 구조 브래킷: PEEK, PEI (Ultem).

FAQ: Material Selection

1. How does moisture affect Nylon (PA) during injection molding?
Nylon is hygroscopic. If not dried to <0.2% moisture content before molding, the water turns to steam, causing splay marks (silver streaks) and significantly reducing the mechanical strength of the part.

2. Can ABS be used for outdoor applications?
Standard ABS has poor UV resistance and will degrade/discolor in sunlight. For outdoor use, ABS requires UV stabilizers or should be replaced with ASA (Acrylonitrile Styrene Acrylate), which has similar properties but superior UV stability.

3. Why is PEEK considered a metal replacement?
PEEK offers a unique combination of high strength-to-weight ratio, chemical inertness, and the ability to hold tight tolerances at high temperatures, allowing it to replace aluminum or steel in aerospace and medical components.

4. What is the difference between amorphous and semi-crystalline plastics?
Amorphous plastics (ABS, PC) have a random molecular structure, shrinking less and offering better transparency. Semi-crystalline plastics (Nylon, PEEK, PP) have ordered structures, offering better chemical and wear resistance but higher shrinkage rates.

5. When should I use glass-filled (GF) materials?
Use glass-filled resins (e.g., PA66 30% GF) when the application requires increased tensile strength, stiffness, and heat resistance. Note that glass fibers can make the material more brittle and abrasive to the mold.

요약

Choosing the right thermoplastic involves navigating a matrix of trade-offs. ABS serves as a versatile, aesthetic choice for general housing; 폴리카보네이트(PC) offers superior toughness and clarity; 나일론(PA) provides structural integrity for mechanical parts; and PEEK delivers unrivaled performance in extreme environments. Engineers must align these material properties with the specific regulatory, thermal, and mechanical demands of the final application to ensure product success.