How to choose the right LFT-G material resin ?

LFT Material Selection Guide: Choosing the Right Resin for Your Application

PP, PA, PPS, or PEEK? Here's a systematic 4-step decision tree to match the right long-fiber thermoplastic to your operating conditions, mechanical demands, and budget.

You've decided that long-fiber reinforced thermoplastics (LFT) are the right solution for your lightweighting or metal-replacement project. But with multiple resin options available - each with its own thermal, chemical, and mechanical profile - how do you choose the right one?

The answer isn't always obvious. PP is economical but temperature-limited. PA offers excellent impact resistance but absorbs moisture. PPS handles high heat and chemicals but costs more. PEEK delivers extreme performance at a premium price.

This guide walks you through a 4-dimensional decision framework - temperature, chemical exposure, mechanical load, and cost - to systematically narrow your options and select the optimal LFT grade for your specific application.

Know to Different: LCF and LGF Material

The 4-Step Decision Tree

Instead of starting with a material and trying to fit it to your application, work through these four filters in order. Each step eliminates candidates that don't meet your requirements, leaving you with a shortlist of viable options.

LFT Materials Laboratory

Step 1 – Operating Temperature: < 80°C → PP / PA | < 120°C → PA / PPS | < 200°C → PPS / PEEK | > 200°C → PEEK
Step 2 – Chemical Exposure: Water/glycol → PA | Acids/solvents → PPS / PEEK | Fuels/oils → PA / PPS | Strong oxidizers → PEEK
Step 3 – Mechanical Load: Static/light → PP | Cyclic/fatigue → PA | High creep/strength → PPS / PEEK | Impact/toughness → PA (LGF)
Step 4 – Cost Budget: Economy → PP | Balanced → PA | High-performance → PPS | Extreme conditions → PEEK

Material Comparison: PP vs. PA vs. PPS vs. PEEK

The table below compares typical properties for 30% long glass fiber (LGF) grades. Actual values vary by fiber content and additives, but this gives you a reliable starting point.

Property	PP-LFT	PA-LFT	PPS-LFT	PEEK-LFT
Service Temp (continuous)	≤ 80°C	≤ 120°C	≤ 200°C	≤ 240°C
Chemical Resistance	Good vs. acids/bases; poor vs. hydrocarbons	Good vs. oils/fuels; poor vs. strong acids	Excellent vs. acids & solvents	Exceptional vs. nearly all chemicals
Tensile Strength (MPa)	~80–110	~150–200	~180–230	~220–280
Flexural Modulus (GPa)	~5–7	~8–12	~12–16	~15–20
Moisture Absorption	Very low	High (requires conditioning)	Very low	Very low
Best for	Low-cost, non-structural, water contact	Automotive structures, impact, fuel systems	High-temp + chemicals, E&E components	Extreme temp/corrosion, aerospace
Avoid for	High heat, strong organic solvents	Strong acids, long-term humid heat	Low-temperature impact, cost-sensitive	Non-extreme applications, tight budgets

Fiber Content: 20% to 60% – What's the Right Loading?

Beyond resin selection, the glass fiber content is your second critical decision. Higher fiber loading increases stiffness, creep resistance, and heat deflection temperature, but reduces flowability and impact toughness.

20%

Balanced

Good flow for thin walls, excellent toughness. Ideal for housings and interior trim.

30–35%

Workhorse

Sweet spot for overall properties. First choice for automotive and industrial structures.

40–50%

High Stiffness

Maximum creep resistance for metal replacement. Reduced flow; gate design critical.

60%

Extreme

Near-metal rigidity and heat deflection. Reserve for specialty high-load brackets.

Pro tip: Start with 30% for most structures. Target 40–50% for die-cast aluminum replacement. Drop to 20–30% for long flow paths. For high-load grades (>40%), consider Direct LFT (D-LFT) molding to preserve fiber length.

Application-Specific Recommendations

Use these real-world application mappings to validate your selection:

Automotive & EV

Why PP LGF30 Outperforms PA6 GF30 in Hot-Humid Automotive Cooling Shrouds

Battery enclosures: PA-LFT (30–40%) for impact and flame retardance
Engine covers: PP-LFT (30%) for cost and heat resistance up to 80°C
Structural brackets: PA-LFT (40–50%) for metal replacement

Aerospace & Defense

Structural supports: PEEK-LFT (40–60%) for extreme temperature and chemical resistance
Interior components: PPS-LFT (30%) for FST (flame, smoke, toxicity) compliance

Industrial & E&E

Industrial Gearbox Plastic housing made by LFT-G PA66 CF Compounds.png

Pump housings: PPS-LFT (30–40%) for chemical and heat resistance
Connectors: PA-LFT (20–30%) for toughness and electrical insulation

Consumer & Robotics

A high-speed industrial robotic arm component made from lightweight PA66 CF40 composite.png

Drone arms: PA-LFT (30–40%) for high strength-to-weight ratio
Robotic joints: PEEK-LFT (30%) for wear resistance and dimensional stability

Common Selection Mistakes

❌ Over-specifying for temperature

Choosing PEEK for a 100°C application when PA would do. You pay for performance you don't need. Match the material to your actual continuous operating temperature, not the peak.

❌ Ignoring the processing constraints

Some LFT grades require specialized screws, higher mold temperatures, or longer cycle times. Account for these costs and capabilities before finalizing your selection.

❌ Forgetting about moisture

PA absorbs moisture, which affects dimensional stability and mechanical properties. If your application is in a humid environment, factor this in or consider PPS/PEEK as alternatives.

How to Validate Your Selection

Once you've narrowed down your candidates, take these steps to confirm the choice:

Request material samples: Get actual molded test bars from your LFT supplier, not just data sheets. Test under your specific conditions.
Run mold flow simulation: Verify that the material will fill your cavity without excessive fiber breakage or weld line issues.
Prototype early: If possible, produce prototype parts and measure mechanical properties against your requirements. Fiber length retention in the final part should be ≥70% of the original pellet length.

Need help? LFT-G^® provides application engineering support including material recommendations, mold flow analysis, and on-site processing assistance. Contact us for a free consultation.

LFT-G Composite Plastic

Get expert material selection advice

Xiamen LFT Composite Plastic Co., Ltd. is a global supplier of long-fiber-reinforced thermoplastics with 20+ years of innovation. We specialize in LFT‑PP, LFT‑PA, LFT‑PPS, and LFT‑Elastomers – offering high‑strength, lightweight alternatives to metal for automotive, aerospace, and industrial applications.