{"id":"wpc-foundations30-article-008-en","slug":"wpc-particle-size-aspect-ratio-pith","locale":"en","url":"https://woodplasticcomposite.net/guides/wpc-particle-size-aspect-ratio-pith/","title":"Particle size, aspect ratio and pith: why filler geometry matters","answer":"Mesh size describes a screening operation, while aspect ratio describes particle shape. Neither number alone predicts composite strength.","author":"NFC & WPC Knowledge Reference","faqIds":[],"tagIds":[],"noindex":false,"related":["wpc-foundations30-article-006-en","wpc-foundations30-article-007-en","wpc-foundations30-article-013-en"],"version":1,"modified":"2026-10-16","reviewer":"","sections":[{"id":"read-a-mesh-specification-correctly","text":"The phrase 20–60 mesh is useful only when the sieve convention and retained/passing fractions are defined. It is not a universal optimum. Two fillers with the same nominal mesh label can contain different mixtures of fines and elongated particles.\n\nStark and Rowlands compared several wood-flour sizes in polypropylene. Their results included different trends for notched and unnotched impact, illustrating why a larger particle cannot simply be labelled better. A separate investigation of wood flour and polyethylene considered size, aspect ratio and moulding temperature together. [R20,R21]","heading":"Read a mesh specification correctly","references":[],"url":"https://woodplasticcomposite.net/guides/wpc-particle-size-aspect-ratio-pith/#read-a-mesh-specification-correctly"},{"id":"look-beyond-the-particle-width","text":"Aspect ratio is length relative to width or diameter under a stated measurement method. Specify whether it was measured before compounding or in the finished composite. The distinction matters when a process changes the reinforcement geometry.\n\nCanola straw with pith and depithed straw is a sensible comparison to investigate, but this collection does not claim a verified numerical advantage for either. A study of wood-flour geometry provides a more general basis for keeping particle form and processing history visible in the comparison.","heading":"Look beyond the particle width","references":[3],"url":"https://woodplasticcomposite.net/guides/wpc-particle-size-aspect-ratio-pith/#look-beyond-the-particle-width"},{"id":"a-practical-supplier-comparison","text":"Request the sieve distribution, microscopy method, moisture result and batch identity. Compare fillers using the same polymer, equipment and test conditions before changing production specifications. Add the handling question: can the filler be fed consistently at the required output?\n\nFor specifiers, the consequence is simple. A supplier's particle-size claim may explain part of its process, but the finished product still needs the relevant performance evidence. Mesh numbers do not replace a board test.","heading":"A practical supplier comparison","references":[],"url":"https://woodplasticcomposite.net/guides/wpc-particle-size-aspect-ratio-pith/#a-practical-supplier-comparison"},{"id":"evidence-scope","text":"[1] Experimental study; official abstract.\n\n[2] Experimental study.\n\n[3] Experimental study; geometry, not proof of a canola-pith result.","heading":"Evidence and source scope","references":[1,2,3],"url":"https://woodplasticcomposite.net/guides/wpc-particle-size-aspect-ratio-pith/#evidence-scope"}],"seoTitle":"Particle size, aspect ratio and pith: why filler geometry matters","topicIds":[],"published":"2026-10-16","tableText":"","takeaways":"","aiAssisted":true,"categoryId":"wpc-foundations30-category-fillers-feedstocks","reviewedAt":"","change_note":"Converted from the referenced English foundations collection. General technical information and editorial specification guidance; not product certification.","description":"Understand mesh grades, particle-size distributions, aspect ratio and pith content, and learn how to compare WPC filler specifications accurately.","heroImageId":"","referenceIds":["wpc-foundations30-ref-r20","wpc-foundations30-ref-r21","wpc-foundations30-ref-r22"],"review_status":"AI-assisted English article. Human technical review has not been recorded.","table_caption":"","seoDescription":"Understand mesh grades, particle-size distributions, aspect ratio and pith content, and learn how to compare WPC filler specifications accurately.","translationGroup":"wpc-foundations30-008-2026","references":[{"url":"https://research.fs.usda.gov/treesearch/8558","type":"web","title":"Effects of wood fiber characteristics on mechanical properties of wood/polypropylene composites; Stark and Rowlands","noindex":false,"accessed":"2026-10-15","seoTitle":"Effects of wood fiber characteristics on mechanical properties of wood/polypropylene composites; Stark and Rowlands","publisher":"research.fs.usda.gov","description":"Experimental study; official abstract","seoDescription":"Experimental study; official abstract"},{"url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC8235768/","type":"web","title":"Investigation of Wood Flour Size, Aspect Ratios, and Injection Molding Temperature on Mechanical Properties of Wood Flour/Polyethylene Composites","noindex":false,"accessed":"2026-10-15","seoTitle":"Investigation of Wood Flour Size, Aspect Ratios, and Injection Molding Temperature on Mechanical Properties of Wood Flour/Polyethylene Composites","publisher":"pmc.ncbi.nlm.nih.gov","description":"Experimental study","seoDescription":"Experimental study"},{"url":"https://www.scielo.cl/scielo.php?pid=S0718-221X2015000300009&script=sci_arttext","type":"web","title":"Study on the effects of wood flour geometry on physical and mechanical properties of wood-plastic composites","noindex":false,"accessed":"2026-10-15","seoTitle":"Study on the effects of wood flour geometry on physical and mechanical properties of wood-plastic composites","publisher":"www.scielo.cl","description":"Experimental study; geometry, not proof of a canola-pith result","seoDescription":"Experimental study; geometry, not proof of a canola-pith result"}],"faqs":[]}