How to Test the Impact Resistance of Polyamide Thermal Break Strips in Cold Environments?

Polyamide thermal break strips play a critical role in maintaining window and door insulation in cold climates, but low temperatures can make the material brittle, reducing its impact resistance. A thermal break strip that cracks or breaks in cold weather fails to block heat transfer and damages the entire window system. As a thermal break strip manufacturer with R&D experience since 2006, we’ve developed rigorous testing protocols to ensure our polyamide thermal break strips perform reliably in freezing conditions. Through our one-stop service—covering twin-screw granulated materials, single-screw extrusion production, and technical testing support—we help customers verify the cold-environment impact resistance of their thermal break strips, ensuring long-term durability.

Why Cold-Environment Impact Resistance Matters for Thermal Break Strips

Low-Temperature Brittle Transition of Polyamide

Polyamide, like most plastics, undergoes a brittle transition at low temperatures—below a certain threshold, its flexibility drops sharply, and it becomes prone to breaking under impact. For thermal break strips used in cold regions (e.g., temperatures as low as -40°C), this transition is a major risk. A standard polyamide thermal break strip that performs well at room temperature may crack when hit by a small impact (e.g., a falling tool during installation) in -30°C weather. This crack creates a heat bridge, destroying the strip’s insulation function and requiring costly replacement. Our 17 years of industry experience show that thermal break strips with poor cold impact resistance are 3 times more likely to fail in winter, making this test critical for product quality.

Real-World Risks in Cold-Weather Installation and Use

Thermal break strips face multiple impact risks in cold environments. During installation in winter, workers may accidentally drop aluminum profiles onto the strips, or tools may bump against them—impacts that wouldn’t damage the strip at room temperature can cause fractures in the cold. After installation, wind-blown debris or even thermal expansion/contraction cycles can create minor impacts that weaken the strip. A reliable thermal break strip must withstand these stresses without breaking. Our testing protocols simulate these real-world scenarios, ensuring the thermal break strips we produce (and support through our one-stop service) can handle cold-environment impacts.

Key Preparations for Cold-Environment Impact Testing

Low-Temperature Conditioning of Thermal Break Strips

Before testing, thermal break strips must be conditioned to the target cold temperature to mimic real-world conditions. Rushing this step leads to inaccurate results—if the strip isn’t fully cooled, its impact resistance will seem higher than it is in actual use. Our protocol requires placing the thermal break strips (cut to standard test sizes: 100mm long × 20mm wide, matching common production dimensions from our single-screw extruders) in a temperature-controlled chamber. We set the chamber to the test temperature (-20°C, -30°C, or -40°C, depending on the customer’s target region) and leave the strips for at least 4 hours—this ensures the entire strip, not just the surface, reaches the cold temperature. As part of our one-stop service, we provide customers with conditioning guidelines and can even pre-condition strips in our lab before testing.

Selection of Representative Test Samples

To ensure test results reflect the performance of an entire batch, samples must be representative of the production run. We recommend taking 10-15 samples from different parts of the thermal break strip production line (e.g., start, middle, end of a batch) to account for any minor variations in extrusion. Our thermal break strips are produced with single-screw extruders (the only equipment capable of making thermal break strips—twin-screw extruders are used solely for granulation), which ensure consistent dimensions and material distribution, but sampling from multiple points adds confidence. We also use samples with no surface defects (Missing edges, white spots, and water marks……) since these can act as stress points and skew test results.

Core Testing Methods for Cold-Environment Impact Resistance

Low-Temperature Charpy Impact Test

The Charpy impact test is the most common method for evaluating thermal break strip impact resistance in cold environments. It measures the energy required to break a notched sample under a single impact—higher energy means better impact resistance. Our protocol uses a Charpy impact tester calibrated to ISO 179 standards. Here’s how we perform the test:

• Notch each conditioned thermal break strip with a V-shaped notch (depth 2mm, angle 45°)—this simulates a small flaw that could form in real use.

• Keep the sample in the cold chamber until immediately before testing (to prevent warming).

• Release the tester’s pendulum (with a known weight, usually 2J for polyamide thermal break strips) to strike the notched area of the sample.

• Record the energy absorbed by the sample—our thermal break strips typically absorb ≥1.2J at -40°C, well above the industry minimum of 0.8J.

Our one-stop service includes training customers to use Charpy testers and interpret results. We also provide reference samples (made from our twin-screw granulated polyamide, which has uniform glass fiber distribution to boost impact resistance) for customers to calibrate their tests.

Low-Temperature Izod Impact Test

For thermal break strips with thinner cross-sections (1.5-2mm thick), the Izod impact test is more suitable—it clamps the sample vertically, making it easier to test narrow strips. The process is similar to Charpy, but the sample is held at one end, and the pendulum strikes the free end. We use an Izod tester with a 1J pendulum for thin thermal break strips. At -30°C, our strips absorb ≥0.9J, ensuring they don’t break under typical cold-environment impacts. The Izod test is especially useful for customers producing thermal break strips for slim-window designs, and we include this test in our one-stop technical support package.

Post-Impact Visual and Structural Inspection

After impact testing, we inspect the thermal break strips to assess damage—passing samples should have no full fractures (only minor cracks, if any) and should retain their structural integrity. A strip that breaks completely fails the test, as it would lose its thermal break function in real use. We also check for delamination between the polyamide and glass fibers—our twin-screw granulation process ensures strong fiber-polymer bonding, so our strips rarely delaminate. For customers, this inspection step is critical: even if a strip absorbs enough energy, visible damage may indicate long-term reliability issues. Our one-stop service includes detailed inspection checklists to help customers document results and make informed decisions about their thermal break strips.

How Our Production Ecosystem Supports Reliable Cold-Environment Impact Resistance

Twin-Screw Granulation for Enhanced Impact Performance

The foundation of our thermal break strips’ cold impact resistance is our twin-screw granulated polyamide. Twin-screw extruders intermesh to disperse glass fibers evenly into the polyamide matrix, forming a network structure that absorbs impact energy in cold temperatures. Unlike single-screw granulation (which creates clumped fibers that weaken the strip), our twin-screw process ensures fibers are distributed at 25-30% content, boosting impact resistance by 30% compared to standard polyamide. When these granules are extruded into strips via our single-screw extruders, the fiber network remains intact, providing consistent cold-environment performance.

One-Stop Testing and Improvement Support

If a customer’s thermal break strips fail cold impact tests, we use our one-stop service to identify and solve the problem. Common issues include low glass fiber content (fixed by adjusting our twin-screw granulation parameters) or uneven extrusion (fixed by optimizing single-screw extruder temperature or speed). We work with customers to adjust production processes and retest samples until they meet the required impact resistance standards. This end-to-end support ensures customers don’t just test their thermal break strips—they improve them.

Testing the impact resistance of polyamide thermal break strips in cold environments is essential for ensuring product reliability and customer satisfaction. Our 17 years of R&D, twin-screw granulation technology, single-screw extrusion expertise, and one-stop service make us the ideal partner for this critical task. Whether you need to test your own thermal break strips or optimize production to boost cold impact resistance, we provide the tools, knowledge, and support to ensure your thermal break strips perform well—even in the coldest climates.