Nondestructive Computed Tomography Volumetric Void Acceptance Criteria for Heavy Polymer Sections
Computed tomography volumetric void acceptance requires zoning heavy polymer walls by stress field, setting pore limits below 0.1% in tensile skins.
Equivalent Spherical Diameter
Meaning
Particle size quantification describes the diameter of an ideal sphere having the same volume as an irregular object. Equivalent spherical diameter relies on the assumption that a non-spherical particle occupies a space matching its actual volume despite complex surface geometry. This value provides a common base for comparing disparate filler geometries or pigment additives within polymer matrices.
Accuracy drops when high aspect ratio fillers such as glass fibres or flaky mica reach high concentrations where inter-particle orientation dominates rheological behavior.
Resin Dispersion
Powder morphology dictates the flow properties of thermoset compounds and thermoplastic resins during the plasticization phase. An equivalent spherical diameter calculation allows compounding engineers to model how fillers shift packing fractions in high-load scenarios. Small particles reduce the void volume between resin beads, which decreases the viscosity of the melt flow if the surface chemistry remains constant.
High surface area particles with low calculated diameters often absorb higher levels of chemical additives, which alters the curing kinetics or the final heat deflection temperature of the moulded part.
Metric Variation
Datasheets for commercial resins report average values derived from laser diffraction or dynamic light scattering methods. Processing equipment expects consistency in these values to avoid fluctuations in gate pressure and clamp tonnage requirements. Regrind material frequently exhibits higher standard deviations in calculated dimensions than virgin resin due to mechanical degradation and the presence of fines.
Moulding setups calibrated for precise virgin feedstocks suffer from shot weight variation when the distribution of dimensions shifts due to the introduction of regrind.
Part Consistency
Surface finish and structural integrity depend on the uniform distribution of these calculated dimensions across the entire molded cross section. Dense packing of fillers with uniform dimensions prevents resin rich areas from forming on the surface of thin walled parts. Voids appear if the size distribution is too broad, leading to localized stress concentrations that initiate premature failure under load.
Proper control of the filler dimension spectrum maintains the mechanical properties of the component against the limits of the specified material.