Aim

• To measure the strength of PL Premium glue using the standard 1cm x 1cm test on PET plastic.
• To measure the strength of Sikaflex 11FC glue using the standard 1cm x 1cm test on PET plastic.

Experiment Setup

The samples were lightly sanded before gluing. The samples were allowed to fully cure for almost 3 weeks. The standard procedure was used to measure the strength of the glue. Five samples were tested altogether.

All the samples were prepared exactly the same way. They were lightly sanded and then pressed them together to make sure all of the 1 cm square was covered with glue without air pockets. The samples were not weighted down but just rested on their side while curing.

	PL Premium samples on the left and Sikaflex 11 FC on the right
	Detail of the clamp used to hold one end of the sample.
	Assembled clamp with one half of the sample.
	The other clamp was made from a small desk vice that was suspended from the ceiling.
	Test setup showing the suspended sample. The second rope is a safety rope to prevent the bottle from hitting the ground.

Results

The following results were obtained from the experiment:

Sample	Breaking Weight (Kg)
1	9.45
2	9.8
3	9.55
4	9.75
5	9.9
Average	9.7

Sikaflex 11 FC - Breaking weight at failure

 

Sample	Breaking Weight (Kg)
6	21.05
7	30.5
8	27.25
9	27.35
10	26.1
Average	26.45

PL Premium - Breaking weight at failure

Images

	Sikaflex 11FC samples after test.
	PL Premium samples after test.
	One PL premium sample held all these items before breaking.

Conclusions / Analysis

• The Sikaflex results varied a little bit but were pretty close to the average. The PL varied more in the breaking strength but on average it held about 2.6 x better than the Sikaflex 11FC.
• The Sikaflex samples always failed in the glue. They showed signs that the glue bonded well to the PET plastic but its own bond strength was ultimately what failed. With the PL, a number of the samples showed that it was the PET substrate that failed as it can be seen partially delaminated.

Observations

• The Sikaflex 11FC could be seen to very slowly yield when the load was around 80% of the breaking amount. It may be possible that if the sample was left at the 80% amount for an extended period of time it may have let go earlier. The PL showed no sign of this.
• On two occasions the plastic had ripped at the suspended vice before the PL failed. The sample was gripped again and the test repeated.