Proper sample preparation in plastic testing is essential to ensure reliable, repeatable results that are comparable to regulatory standards (such as ISO or ASTM). The mechanical, thermal, and rheological properties of polymers are strongly influenced by factors such as the molding method, molecular orientation, the presence of residual stresses, and environmental conditions. A sample prepared in a non-compliant manner—for example, with imprecise geometries, damaged surfaces, or uncontrolled conditioning conditions—can significantly alter test results (tensile, impact, flexural). Even small variations during the cutting or molding phase can introduce internal defects or anisotropies that compromise data interpretation. Careful preparation therefore reduces experimental variability and yields data representative of the material’s actual behavior.