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Created page with "{{Language_sel|LANG=ger|ARTIKEL=Formmasseprüfung}} {{PSM_Infobox}} <span style="font-size:1.2em;font-weight:bold;">Moulding compound test</span> __FORCETOC__ ==Methods of moulding compound testing== The properties of the moulding compound are essentially determined by its chemical composition and the associated manufacturing processes, and are therefore largely independent of the material’s geometry and history. However, this is only true if..."

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{{Language_sel|LANG=ger|ARTIKEL=Formmasseprüfung}}
{{PSM_Infobox}}
<span style="font-size:1.2em;font-weight:bold;">Moulding compound test</span>
__FORCETOC__

==Methods of moulding compound testing==

The properties of the moulding compound are essentially determined by its chemical composition and the associated manufacturing processes, and are therefore largely independent of the [[Material & Werkstoff|material’s]] geometry and history. However, this is only true if the manufacturing process does not involve extrusion followed by granulation using processing aids or the incorporation of reinforcing agents or fillers.

Moulding compound testing therefore constitutes an analytical task that provides information not only on the chemical and physical [[Polymers & Structure|structure]] of the [[Plastics|plastic]], but also on its rheological and processing [[Material Value|characteristic values]]. The physical testing methods used are not only employed for analytical characterisation in the context of plastics analysis, but also form the crucial basis for establishing correlations between the [[Microscopic Structure|structure]] of macromolecular materials, their manufacturing and processing conditions, and their technological properties.

Typical identification methods used in incoming inspections in industrial practice, which provide characteristic information on the composition or differentiation of plastics, include [[Density|density]] measurement, determination of melting and [[Vicat Softening Temperature|softening temperatures]], [[Ashing Method|ash analysis]], combustion tests and/or pyrolysis tests, which can be supplemented where necessary by spectroscopic testing methods such as [[FTIR Spectroscopy|infrared spectroscopy (FTIR)]] or [[Thermogravimetric Analysis (TGA)|thermogravimetric analysis (TGA)]], [[Differential Scanning Calorimetry (DSC)|differential scanning calorimetry (DSC)]] and [[Thermomechanical Analysis|thermomechanical analysis]] (TMA), as only small sample quantities are required here.

The processability of plastics can be assessed using either simple technological methods or more complex rheological test procedures, depending on the specific requirements and the type of material. From an industrial perspective, particle size analysis and the measurement of [[Viscosity|viscosity]] or melt flow rate ([[Melt Volume-Flow Rate|MVR]], [[Melt Mass-Flow Rate|MFR]]) are particularly important. Due to the known correlations between molecular weight, molecular weight distribution and the [[Polymers & Structure|structure]] of macromolecules with application-related properties such as [[Strength|strength]], [[Ductility Plastics|ductility]], [[Toughness|toughness]] and [[Density|density]], it is possible to draw certain conclusions from the determined levels of these [[Material Value|characteristic values]] regarding the influence of the processing and manufacturing process on chemical degradation effects [1].

==Methodology of specimen extraction==

Sampling plays an important role in characterising the properties of [[Moulding Compound|moulding compounds]], as the statistical sample taken – usually consisting of small quantities of material ('''Fig. 1''') – is intended to represent the entire population of properties. The accuracy of the characterisation of these properties depends not only on the measurement techniques used, but also significantly on the method of sampling.

[[File:Formmassepruefung_1.jpg]]
{|
|- valign="top"
|width="50px"|'''Fig. 1''':
|width="600px" |Single-type coloured plastic granules (a) and pulverised or shredded plastic regranulate (b)
|}

If no suitable sample divider is available, the total quantity to be characterised must be thoroughly mixed, and samples must then be taken at three points sufficiently far from the [[Surface|surface]]. Sampling at different positions is intended to compensate for changes in particle size distribution and [[Standard Atmospheres|moisture]] content caused by transport and storage, as well as segregation effects. If mixing is not possible, as is the case with silo storage, for example, the statistical samples should be taken evenly from several depths. Moisture measurement can also be carried out online, e.g. using a moisture sensor. A common sampling technique for granules and powders is the so-called quartering method [2, 3]. For the purposes of traceability and accountability, the test report to be drawn up must document all details identifying the [[Plastics|plastic]] (type of material, delivery date, bag number, filling date, type and condition of packaging, etc.). As with the processing of the material, a material-specific pre-treatment must be carried out prior to [[Testing|testing]] in order, for example, to remove condensation or foreign particles resulting from storage and to establish a defined reference condition.

==Manufacturing process for test specimens==

In order to characterise the properties of polymer [[Moulding Compound|moulding compounds]] using mechanical, thermal or electrical [[Material Parameter|parameters]], precisely specified test [[Specimen|specimens]] are required in accordance with the relevant standards; these must meet defined requirements regarding their dimensions and condition. These test specimens can be produced separately or together with a [[Plastic Component|structural]] or [[Moulding Compound|moulded part]], or can be taken from such a part, e.g. for investigating the property profile within the moulded part or for [[Failure Analysis – Basics|failure analysis]]. The direct and indirect methods of moulding and forming technology commonly used for test specimen production are listed below, whereby test specimens made from pressed or injection-moulded sheets are to be preferred due to their low [[Tensile Test Residual Stresses Orientations|residual stresses]] and the absence or dominance of [[Tensile Test Residual Stresses Orientations|orientation]]:

* Direct forming processes
** Injection moulding
** Injection stamping
** Compression moulding
** Casting
* Indirect forming processes
** Extrusion
** Calendering
** Stamping
** Cutting

==Influence of the inner state of order==

Regardless of the type of shaping process, material-dependent [[Energy Elasticity|elastic]], [[Entropy Elasticity|entropic]] and [[Deformation#Viscous deformation|viscous deformations]] occur during manufacture. These deformations are caused by shearing, e.g. during the injection and flow process, stretching and elongation of macromolecules, as well as cooling and solidification processes within the mould, and have a dominant influence on the subsequent internal state of the component or test specimen. Energy-elastic deformation is based on reversible changes in the vibrational and rotational states of atoms and parts of the macromolecule and is therefore time-independent. Entropic-elastic deformations correspond to changes in entropy, i.e. in the internal state of order, with translational movements of chain segments occurring at elevated temperatures. These processes are reversible, but depend on time and temperature. Irreversible viscous deformations result from the slippage of macromolecules due to [[Shear Viscosity|shear]] and/or stretching during the manufacturing process.

As an additional deformation, a material-dependent volume contraction occurs during the transition from the molten to the solid state; this is also referred to as [[Processing Shrinkage|processing shrinkage]] and must be taken into account by allowing for an appropriate amount of material allowance in the mould design. [[Processing Shrinkage|Shrinkage affects]] dimensional accuracy and tolerances, and is generally less pronounced in [[Particle-filled Thermoplastics|filled]] or [[Fibre-reinforced Plastics|reinforced]] materials than in the matrix material.

Depending on the complexity of the [[Moulding Compound|moulded part]], these various processes generally result in an uneven distribution of internal stresses ([[Tensile Test Residual Stresses Orientations|residual stresses]]), matrix and filler orientations, and morphological [[Material Parameter|parameters]] of the [[Plastics|plastic]]. This makes it clear that the characteristic values determined on test [[Specimen|specimens]] do not, as a rule, represent the properties of the moulded material, but rather characterise the properties of the test specimen, which is in a specific state determined by the manufacturing process. Determining material-specific [[Material Value|characteristic values]] therefore requires fundamental information on the state of the test specimen and the selected test conditions.

==See also==

* [[Moulding Compound|Moulding compound]]
* [[Standard Atmospheres|Standard atmospheres]]
* [[Test Climate|Test climate]]
* [[Water Absorption|Water absorption]]

==References==

{|
|-valign="top"
|[1]
|[[Bierögel,_Christian|Bierögel, C.]]: Preparation of Specimen. In: [[Grellmann,_Wolfgang|Grellmann, W.]], [[Seidler,_Sabine|Seidler, S.]] (Eds.): Polymer Testing. Carl Hanser, Munich (2022), 3rd Edition, pp. 18–19 (ISBN 978-1-56990-806-8; E-Book: ISBN 978-1-56990-807-5; see [[AMK-Library]] under A 23)
|-valign="top"
|[2]
|Brown, R. (Ed.): Handbook of Polymer Testing: Physical Methods. Marcel Dekker, New York Basel (1999) (ISBN 0-8247-0171-2; see [[AMK-Library]] under C 5)
|-valign="top"
|[3]
|Brown, R.: Handbook of Polymer Testing – Short-Term Mechanical Tests. Rapra Technology Limited, Shawbury (2002) (ISBN 1-85957-324-X)
|}

[[Category:Specimen Preparation]]

Moulding Compound Test - Revision history