Anisotropic Shrinkage Variance in Glass-Filled Polyamide Secondary Tooling Nests
Secondary tooling nests for glass-filled polyamide accommodate anisotropic shrinkage through floating datum pins aligned with transverse contraction vectors.
ISO 62
Meaning
International test standards establish uniform laboratory procedures for measuring the physical and chemical characteristics of polymer resins. ISO 62 specifies methods for determining the moisture absorption properties of plastics when immersed in water or exposed to a humid atmosphere. This testing is essential for evaluating how dimensional stability and mechanical performance will change under wet operating conditions.
Moisture Measurement
The standard provides protocol for measuring the mass increase of standardized specimens under controlled temperature and humidity. Materials are tested until they reach saturation or after specific exposure times, and the results are expressed as a percentage of weight gain.
Testing Method
The test specimens are typically flat disks or square plaques molded under controlled conditions to ensure consistent thickness and surface area. These specimens are dried in an oven before being weighed, placed in the exposure medium, and weighed again at regular intervals until the weight stabilizes. Accurate balance measurements down to one-tenth of a milligram are required to ensure the precision of the absorption curve.
This controlled procedure allows direct comparison of moisture resistance across different polymer grades.
Molding Consequence
Knowing the moisture absorption rate of a resin allows processors to design appropriate drying times for hygroscopic polymers like nylon or polyester. High moisture content during injection molding triggers hydrolysis, which breaks the polymer chains and reduces the mechanical strength of the molded part. This test standard helps determine the dry state required to prevent such degradation.