Engineer Education Series #10: Material Selection for Extruded Plastic Parts

Material selection is one of the most critical decisions in the design of extruded plastic components. The selected material directly influences part performance, durability, manufacturability, and overall cost.

While geometry and tooling are important, even a well-designed profile can fail if the material is not suited for the application. Understanding how different thermoplastics behave during extrusion and in real-world environments allows engineers to make more informed decisions early in the design process.

Key Material Properties to Consider

Selecting the right material starts with understanding the performance requirements of the application.

Important properties include:

• Strength and stiffness – determines load-bearing capability and resistance to deformation
• Flexibility – important for snap-fit features, seals, or impact absorption
• Impact resistance – critical for components exposed to shock or vibration
• Temperature resistance – ability to maintain performance across operating ranges
• Chemical resistance – required for exposure to oils, solvents, fertilizers, or industrial chemicals

Each application prioritizes these properties differently, so material selection should be driven by actual use conditions rather than general assumptions.

Common Materials Used in Plastic Extrusion

Several thermoplastics are commonly used in extrusion, each offering different advantages.

PVC (Polyvinyl Chloride)
• cost-effective and widely used
• good weather and chemical resistance
• suitable for rigid and flexible applications

HDPE (High-Density Polyethylene)
• excellent chemical and moisture resistance
• good impact strength
• commonly used in outdoor and industrial environments

ABS (Acrylonitrile Butadiene Styrene)
• strong and impact resistant
• good surface finish
• often used in more rigid applications

Polycarbonate (PC)
• high strength and durability
• excellent impact resistance
• suitable for demanding structural applications

TPE (Thermoplastic Elastomers)
• flexible and rubber-like
• ideal for seals, grips, and soft-touch surfaces

Each material behaves differently during extrusion and cooling, which directly affects final dimensions and performance.

Material Behavior During Extrusion

Material selection must account for how the polymer behaves during processing.

Key considerations include:

• melt flow characteristics – affects how material fills the die
• shrinkage during cooling – influences final dimensions and tolerances
• thermal stability – determines processing temperature range
• dimensional stability – impacts consistency in production

Some materials are easier to process and maintain tighter tolerances, while others may require more precise control and tooling adjustments.

Environmental and Application-Specific Factors

Real-world conditions often play a major role in material selection.

Engineers should evaluate:

• UV exposure – may require UV-stabilized materials
• moisture and humidity – impacts absorption and long-term durability
• temperature extremes – affects flexibility and structural integrity
• chemical exposure – can degrade certain materials over time

Failing to account for environmental factors can lead to premature part failure, even if the initial design meets performance requirements.

Balancing Performance and Cost

Material selection is often a balance between performance requirements and cost constraints.

Higher-performance materials may offer:

• increased durability
• better environmental resistance
• improved mechanical properties

However, they may also:

• increase material cost
• require more complex processing
• extend development timelines

In many cases, the optimal solution is not the highest-performing material, but the one that meets requirements efficiently.

Collaboration Improves Material Selection

Working with an extrusion manufacturer early in the design process can help engineers select the most appropriate material.

Manufacturers can provide insight into:

• material availability
• processing characteristics
• cost implications
• real-world performance

This collaboration helps ensure the selected material aligns with both design intent and manufacturing capabilities.

Designing for Material Success

Successful extrusion projects typically involve:

• selecting materials based on real application conditions
• understanding how materials behave during extrusion
• balancing performance with cost
• collaborating early with manufacturing partners

Material selection is not just a specification — it is a key factor in long-term product performance and production success.