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Created page with "{{Language_sel|LANG=ger|ARTIKEL=Mikroporen}} {{PSM_Infobox}} <span style="font-size:1.2em;font-weight:bold;">Micropores</span> During the injection moulding process, volume contraction (see: processing shrinkage) occurs as the material cools. In areas where material has accumulated, this volume contraction of the melt is greater, and the reduced volume cannot be replaced by fresh melt. As a result, Tensile Test Residual Stresses Orientations|..."

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{{Language_sel|LANG=ger|ARTIKEL=Mikroporen}}
{{PSM_Infobox}}
<span style="font-size:1.2em;font-weight:bold;">Micropores</span>

During the injection moulding process, volume contraction (see: [[Processing Shrinkage|processing shrinkage]]) occurs as the material cools. In areas where material has accumulated, this volume contraction of the melt is greater, and the reduced volume cannot be replaced by fresh melt. As a result, [[Tensile Test Residual Stresses Orientations|tensile residual stresses]] build up within the material.

Micropores occur when the solidified surface layer is sufficiently stable to counteract the internal tendency to contract. Due to the tensile stresses acting within the material, the [[Moulding Compound|moulding compound]] tears open at the centre of material accumulations. Micropores are very small [[Shrink Voids|shrink voids]] (vacuoles) that occur in the plastic core. As they are very small, they are largely inconsequential in terms of [[Strength|strength]] and [[stiffness|stiffness]], but can be observed as white discolouration in unfilled moulded parts. In transparent or translucent materials, however, they impair the optical properties (see '''Figure''').

[[File:Mikroporen1.jpg]]
{|
|- valign="top"
|width="50px"|'''Figure''':
|width="600px" |Micropores in a translucent plastic component made of polypropylene ([[Plastics – Symbols and Abbreviated Terms|abbreviation]]: PP)
|}

==See also==

* [[Micro-Damage Limit|Micro-damage limit]]
* [[Failure Analysis Plastics Products, VDI Guideline 3822|Failure analysis plastics products, VDI Guideline 3822]]
* [[Failure Analysis – Basics|Failure analysis – Basics]]
* [[Gas Bubbles|Gas bubbles]]
* [[Shrink Voids|Shrink voids]]
* [[Hole Formation Films|Hole formation films]]
* [[Hole Formation Plastics|Hole formation plastics]]

==References==

{|
|-valign="top"
|[1]
|VDI 3822 Blatt 2.1.2 (2024-06): Failure Analysis – Defects of Thermoplastic Products Made of Plastics Caused by Faulty Processing
|}

'''Additional references on polymer diagnostics/damage analysis '''

* [[Ehrenstein, Gottfried W.|Ehrenstein, G. W.]]: Kunststoff-Schadensanalyse – Methoden und Verfahren. Carl Hanser, Munich Vienna (1992) (ISBN 978-3-446-17329-3; see [[AMK-Library]] under D 2)
* Ehrenstein, G. W.: SEM of Plastics Failure – REM von Kunststoffschäden. Carl Hanser, Munich (2010) (ISBN 978-3-446-42242-1; see [[AMK-Library]] under D 5)
* Engel, D., Klingele, H., Ehrenstein, G. W., Schaper, H.: Rasterelektronenmikroskopische Untersuchungen von Kunststoffschäden. Carl Hanser, Munich Vienna (1978) 1st Edition (ISBN 978-3-446-12560-5, see [[AMK-Library]] under D 8)
* Brostow, W., Corneliussen, R. D.: Failure of Plastics. Carl Hanser, Munich Vienna (1986) (ISBN 978-3-446-14199-5; see [[AMK-Library]] under D 10)
* Ezrin, Myer: Plastics Failure Guide – Cause and Prevention. Carl Hanser, Munich 2nd Edition (2013) (ISBN 978-1-56990-449-7; see [[AMK-Library]] under D 7)
* Kurr, F.: Praxishandbuch der Qualitäts- und Schadensanalyse für Kunststoffe. Carl Hanser, Munich (2014) (ISBN 978-3-446-43775-3; see [[AMK-Library]] under D 6-2)

[[Category:Damage Analysis_Component Failure]]

Micropores - Revision history