Penetration Test of a Glue Stick with Electric Surface Detection

This Application Report gives an example on how to measure the consistency of glue sticks with Anton Paar’s penetrometer PNR 12. You will get information about how the consistency of glue sticks is measured with the PNR 12 and what kind of information the results deliver about the material under test.

We come across consistency in everyday life without ever thinking about it. One typical example is the glue stick. If the consistency of this adhesive is too hard (low penetration value), it will not adhere to the material it is applied to or the stick may break easily. If the consistency is too soft (high penetration value), the glue stick may deform or too much of the adhesive material is applied to the paper.

The PNR 12 automatically measures the resistance a material provides to being pierced by a specifically shaped test body. Therefore, a needle-shaped or conical test body is precisely lowered to the surface of the material under test. It will sink into the sample by its own weight for a fixed period of time. This allows a rating of the plasticity or consistency.

The origin of Anton Paar’s penetrometer lies in the petroleum industry for testing the constitution of lubricating greases and waxes, and in measuring the hardness of bitumen. The PNR 12 has gained a wide scope of application, due to the ease of adapting the gravity penetrometer to a broad range of applications – making it possible to test materials such as glue sticks.

When performing a consistency test a needle shaped or conical test body is precisely lowered to the surface of the material, and then sinks into the sample by its own weight for a defined test duration. After the penetration with the test body, the distance the test body sank into the material is measured and then converted into Penetration Units [PU].