What is the difference between polycarbonate and acrylic?

Polycarbonate offers 250 times the impact strength of glass and 30 times stronger than acrylic, making it virtually unbreakable for safety applications. Acrylic provides superior optical clarity and costs 30-40% less than polycarbonate but is more brittle. Choose polycarbonate when impact resistance is critical; select acrylic when clarity and weather resistance matter most.

Which plastics are FDA compliant for food contact applications?

FDA-compliant plastics meeting 21 CFR 177 regulations include natural UHMW polyethylene, white acetal copolymer, FDA-grade HDPE, polypropylene, clear polycarbonate, and acrylic. Port Plastics provides material certification documentation confirming FDA compliance with every shipment.

What temperature can PEEK plastic withstand?

PEEK maintains continuous service at temperatures up to 480°F (250°C) and can withstand short-term excursions to 570°F (300°C) without degradation. PEEK retains 90% of its room-temperature tensile strength at 300°F and performs in extreme cold to -40°F without becoming brittle.

Do you offer same-day delivery?

Same-day delivery is available for in-stock materials ordered before noon local time within our standard delivery radius. Each of our 11 facilities maintains inventory of commonly specified materials. Contact your local Port Plastics branch for specific delivery timelines.

CLTE vs Moisture Absorption

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When designing precision applications for semiconductor manufacturing environments, understanding dimensional stability is critical. Two key factors influence how plastic materials behave in these demanding conditions: Moisture Absorption and the Coefficient of Linear Thermal Expansion (CLTE). But which property has the greater impact on your finished application?

Understanding Moisture Absorption in Engineering Plastics

Moisture Absorption measures the weight gain of a plastic specimen both during short-term immersion (24 hours) and at full saturation, following ASTM D590 testing standards. This property is crucial for understanding how materials behave in humid or wet environments common in semiconductor fabrication facilities.

How Moisture Absorption Works

For most engineering plastics, moisture exists in a free state within nano-sized pockets throughout the polymer matrix. While 24-hour immersion testing provides valuable data about the rate of absorption, saturation levels primarily apply to applications that will exist in continuously saturated environments—a relatively rare scenario in most semiconductor applications.

Key Insight: Practical Moisture Absorption

The practical moisture absorption of a specific plastic material depends on reaching equilibrium within its actual operating environment. A material will not reach full saturation unless it is completely immersed in liquid—a condition that rarely occurs in semiconductor tooling and fixtures.

The Coefficient of Linear Thermal Expansion (CLTE) Explained

CLTE is a measure of the change in length of a plastic material per unit temperature change. This coefficient quantifies how much a material expands or contracts as temperature fluctuates—a critical consideration in precision semiconductor equipment where tolerances are measured in microns.

Material-Specific Coefficients

Every engineering plastic material has its own unique CLTE coefficient that engineers can use to calculate expected dimensional changes over specific temperature ranges. For engineering plastic materials used in semiconductor applications, the standard test range spans from -30°F to 300°F (-34°C to 149°C), covering the extreme conditions these materials may encounter.

Technical Note: CLTE is typically expressed in units of in/in/°F (inches per inch per degree Fahrenheit) or mm/mm/°C (millimeters per millimeter per degree Celsius). This ratio allows engineers to calculate dimensional changes for components of any size.

The Great Race: CLTE vs Moisture Absorption

The critical question for engineers designing semiconductor tooling and fixtures is: Which property has a larger impact on material growth and dimensional stability?

Real-World Testing with PEEK

To answer this question definitively, Port Plastics conducted comparative testing using PEEK (Polyetheretherketone), one of the most common high-performance polymers in semiconductor applications. The results were striking and may surprise many engineers.

Test Parameters and Results

Test Sample: 50mm PEEK bar
CLTE Value: 2.6 × 10⁻⁵ in/in/°F
Temperature Range: 0°F to 150°F (83°C range)
Moisture Saturation Value: 0.5%
Moisture Test: Completely dry to full saturation

The Winner: CLTE by a Factor of Nearly 7X

? Growth from CLTE (0°F to 150°F): 0.20mm
? Growth from Moisture (dry to saturation): 0.03mm
? Impact Ratio: CLTE has ~6.7× more impact than moisture absorption

Dimensional Changes Across the Length of Material

Understanding how dimensional changes accumulate across the length of a component is essential for precision applications. The following data shows calculated movement at 10mm increments along the 50mm PEEK test bar due to CLTE, compared to the total moisture absorption impact: