A Comparison of Image Analysis With Other Methods of particle size measurement for general purpose PVC resins

Abstract

Of all methods of particle size analysis determination only microscopy and subsequent image analysis enables accurate, geometrically determined size parameters to be measured. For this reason image analysis is a convenient referee or umpire method against which to compare other techniques. In this study, a series of seven poly(vinyl) chloride (PVC) resins were characterized by optical microscopy and image analysis, sieves, HIAC and Coulter counter. It was not found possible to perform the image analysis measurements without operator intervention with a light pen to separate agglomerates. The PVC particles were far too irregular to enable this task to be performed by erosion and dialation techniques. The errors at 90% confidence associated with the image analysis study were: calibration ± 1.7%, counting statistics ± 1% (max) with a focus and algorithms error which ranged from ½‐3% depending upon the quantity being measured. These numbers gave a total error of ± 2% (ca. one pixel) for equivalent circular diameter (ECD) and ± 4% (ca. two pixels) for object breadth. In general the agreement between the various techniques was quite good suggesting that the object breadth (OB) as measured by sieves was nearly identical to equivalent spherical diameter (ECD) as measured by the HIAC and Coulter counter for the samples investigates. A study of the image analysis data alone confirmed that OB and ECD were nearly identical with ECD running about 6.1 m̈m above OB. Mass resin samples, which are prone to electrostatic charging effects, tended to give slightly higher results in those methods which measured the resin in the dry state (HIAC and sieves). Finally, it should be suggested that many of the classical concepts of resolution and depth of focus which are used to place limits upon the performance of the optical microscope do not necessarily apply to particle size determination by image analysis. If the chord through the particle which describes its diameter can be considered an approximation to a square wave then it is the fundamental frequency of the Fourier components of that square wave that contains the size information. This should be true for microscopic objects which are absorbing of light and non‐retarding in nature. Once this fundamental frequency can be identified then sizing accuracy is dependent chiefly on the signal to noise ratio of the system.

Batch emulsion polymerization of vinyl chloride: Application of experimental design to investigate the effects of operating variables on particle size and particle size distribution

“…The average PS in each micrograph was determined by means of Sigma Scanpro5® software (version 5.0), in which the surface area of each particle was measured by filling the surface with pixels. The number of pixels (NP) is then equaled to the surface area of a circle, so that the equivalent circular diameter (ECD) is obtained in dimension of pixel numbers23: …”

PVC Morphology

“…115 The original grain structure and skin were destroyed. [116][117] 115 At the same time, precipitated polymer had much higher absorption of plasticizer due to its substantially smaller bulk density and more developed structure.…”

Particle Size Distribution Analysis of an Alumina Powder: Influence of Some Dispersants, pH and Supersonic Vibration

“…Various particle size determination techniques have been developed, however a lot of difficulties inherent to each technique arises in order to obtain accurate values [2][3][4][5][6]. For that reason reproducibility becomes more relevant in process control, although accuracy is demanded in research and development activities [7].…”