What is Dropping Point? What is Softening Point?

What is Dropping Point? What is Softening Point?

Definitions, Determination Principle, Influences, Measurement Tips and Hints, Regulations & More

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dropping point determination
What is dropping point
What is softening point
dropping point tar

Generally, a dropping point or softening point is determined by heating the sample. The furnace is used to control the temperature program during an analysis. Temperature control and temperature recording is guaranteed by a digital platinum temperature sensor. In the Dropping Point instruments from METTLER TOLEDO, a white balanced LED light shines on the test assembly, which consists of the cup and holder inside the furnace. The sample behavior is recorded by a video camera.

Length diagram of a duplicate determination of the softening point shown in the graphic on the right side. The steeper the slope (indication of the flow speed), the lower the viscosity.

softening point length diagram
softening point length diagram
dropping point
softening point

 Manual setupDigital setup
Sample holderCupCup
Temperature regulationCirculating liquid bathMetal block
Temperature rangeLiquid dependent or different mediumWide range
Temperature measurementMercury thermometer (*)Digital sensor (e.g. Pt100)
DetectionVisual, i.e. human eyeVisual and automatic (transmittance, photometric, video/image analysis)

(*) EU 847/2012 - WARNING—Mercury has been designated by many regulatory agencies as a hazardous material that can cause central nervous system, kidney and liver damage.

Ubbelohde method

The following table shows the maximum repeatability and reproducibility ranges specified in the DIN standard. Such high testing errors cope with operator bias, but render results reliability questionable and actually unsuitable for comparison.

Dropping Point [°C]Repeatable variation range (one observer, one device) [°C]Comparable variation range (various observers, various devices) [°C]
80-100±2±5
100-150±4±7
150-200±6±12
>200±8±16

 

dropping point sample cups
Softening Point Ring-and-Ball

Adhesive resins

Ink resins

Gum rosin (E915)

Phenolic rosin

Glycerol ester (E445)

Polyol maleic rosin ester A

Penta rosin ester

Polyol maleic rosin ester B

Polyterpene resin

 

 

Taking glycerol ester as a representative example, in the figure below it can be demonstrated how close the softening point of a ring-and-ball and cup-and-ball are. Both cup-and-ball standard deviations are smaller than the corresponding ring-and-ball, which indicates a better precision, and hence better repeatability and reproducibility of the cup-and-ball method. This is also the case for the other substances.
Taking glycerol ester as a representative example, in the figure below it can be demonstrated how close the softening point of a ring-and-ball and cup-and-ball are. Both cup-and-ball standard deviations are smaller than the corresponding ring-and-ball, which indicates a better precision, and hence better repeatability and reproducibility of the cup-and-ball method. This is also the case for the other substances.
The following figure reveals that there is a close correlation between the two methods, ring-and-ball and cup-and-ball, and that the results can be considered equivalent.
The following figure reveals that there is a close correlation between the two methods, ring-and-ball and cup-and-ball, and that the results can be considered equivalent.

Sample

Standard

Operation Mode

Asphalt & Pitch

ASTM D3461

SP

Asphalt & Pitch

ASTM D3104

SP

Lubricating grease

IP 396

DP

Waxes & Polyolefins

ASTM D3954

DP

Resins

ASTM D6090

SP

Paints & Varnishes

ISO 4625-2

SP

Binding & Impregnating materials

DIN EN 51920

SP

Edible fats & oils

AOCS Cc 18-80

DP

Vaseline, Paraffins, Waxes

Ph. Eur. 2.2.17

DP

SP – softening point DP – dropping point

IP 396 workflow requirements
dropping point calibration procedure
melting point calibration and adjustment

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