There are three main categories of common causes.
Material-related issues
ABS features poor low-temperature resistance and tends to turn brittle in cold environments. Materials with a high glass transition temperature and insufficient toughness are also susceptible to cracking. It is widely recommended to adopt PC/ABS blends, or improve performance via toughening modification and elastomer compounding. The core is to conduct thorough pre-verification. For instance, test the low-temperature resistance at -20 °C in compliance with international standards and require suppliers to provide third-party certification reports. Otherwise, even high-grade materials will not work effectively.
Process-related issues
Improper control of molding temperature, injection pressure, holding pressure and cooling during injection molding will lead to excessive residual stress inside the housing. Poorly designed cooling channels in molds will also result in uneven shrinkage. It is essential to ensure full visibility of process data from suppliers and calibrate equipment parameters on a regular basis. Otherwise, cracking is highly likely to occur during low-temperature tests.
Design-related issues
Abrupt wall thickness transitions and sharp corners will give rise to stress concentration. In addition, inadequate annealing after injection molding will further increase the risk of cracking at low temperatures.
Low-temperature Resistance Test for Injection-Molded Outdoor Surveillance Camera Housings
The finished product tests mainly focus on brittleness, cracking and dimensional stability after exposure to low temperatures. The commonly used test methods are listed below:
Low-temperature Impact Test
Perform Izod impact test in accordance with ASTM D256 to assess the risk of low-temperature brittle cracking of security housings. A cold bath is additionally required for low-temperature testing, as the original standard is mainly designed for impact strength measurement.
Low-temperature Chamber & Thermal Shock Test
Follow GB/T 2423.1. Place the housings in a low-temperature chamber or thermal shock test chamber, and inspect for cracking, deformation and dimensional stability.
Low-temperature Tensile & Flexural Test
Refer to ISO 527-2, ASTM D638 and ISO 178 to examine changes in tensile strength, elongation at break and flexural strength.
Preliminary On-site Inspection
Simulate the environment of -30°C with dry ice and alcohol, then conduct manual bending and impact checks to identify brittleness and cracking.
Note: This method is only for preliminary screening and cannot replace standard tests. Please follow safety precautions during operation.
