This procedure is used to measure the sheer strength of a
glue sample. This test is aimed at comparing glues and their
effectiveness in bonding to PET plastic. Adhesion quality to PET
is usually not covered in manufacturers data sheets.
The main purpose of this test is for quick evaluation of the
glue whether it is suitable for splicing bottles. A sample that
passes this test at a low load is very unlikely to be suitable
for splicing. A sample that passes this test at a fairly high
load is a good candidate for performing a more complicated
2 clamps capable of holding a sample of PET plastic
Weights, container for water
Cut 1 cm wide strip approximately 10 cm in length from a
Clean the strip, removing any grease and dirt.
Cut the strip in half, and label both ends of the
Lightly sand the end of each strip that will overlap.
Draw a line on both halves 1 cm from the end.
Apply enough glue to the strip to completely cover the
Carefully overlap the two strips using the lines on each
half and clamp if necessary.
Allow sample to fully cure according to the
manufacturer's instructions before testing.
Clamp both ends of the sample in the two clamps. Make
sure the sample is well aligned so that the sample is not
pulled to one side or twisted when load is applied.
Suspend one of the clamps from a strong support such as
a door frame.
Suspend weights from the other clamp until the sample
brakes. An empty container of water can be suspended from
the clamp and water gradually poured in until the sample
After the break, use the scale to measure the weight
that was suspended
under the lower clamp. Don't forget to also include the
weight of the clamp and any ropes used to hold the weight.
This is the sample's breaking weight. Record this
Repeat the experiment a number of times and average the
There can be a substantial amount of weight hanging from
the sample. Make sure the weight dropping will not damage
A second slack safety line can be used threaded through
the weights so that it will stop the weights impacting with
The safety line can also be used to prevent the water
spilling from the water container so that it can be
These tests can show a high variability in the results
between samples. It is a good idea to make more than 3
measurements for each glue being tested.