# Designing a good downscaled compaction test

When storing a large amount of polymer material, afterwards we are experiencing bad flow properties during processing. We expect it is due to storing the material for long periods of time at high temperature and humidity in our warehouse.

I want to do some small scale test to reproduce the conditions and test a number of additives to enhance the flow properties of the material. We want to have a relatively small amount ($3\,\mathrm{kg}$) of material in a box and add weights to simulate the weight of the $500\,\mathrm{kg}$ box.

1. Are there any standardized test for these types of compaction test?
2. How do I determine the weights needed to simulate the weight of a $500\,\mathrm{kg}$?

An attempt at answering question 2 was made by assuming we want the same pressure on the large box as on the test scale. In the large box, assuming the material a hydrostatic fluid, it experiences a pressure at the bottom of the box:

$$P = \rho_b g h \approx 10\,\mathrm{kPa}$$

where I have assumed a bulk material density $\rho_b=500\,\mathrm{kg/m^3}$, gravitational acceleration $g\approx10\,\mathrm{m/s^2}$ and a material height $h=2\,\mathrm{m}$. At the test scale we then need to provide the same pressure by applying a force: $$F=m_tg=PA_t \rightarrow m_t={{PA_t}\over{g}}=\rho_bA_th=50\,\mathrm{kg}$$

for test box with area $A_t=0.1\,\mathrm{m^2}$.

The polymer is a TPE (SEBS) with about 10% oil by weight, Shore 60 hardness but flexible when compounded.

• What material? Amide-based polymers (and others which are strengthened by hydrogen bonding) absorb ambient water. Jun 28, 2016 at 22:46
• @starrise its a TPE (SEBS) with about 10w% oil, Shore 60 hardness but flexibele when compounded Jun 29, 2016 at 5:32
• Weight (actually, pressure), ambient humidity,and temperature all contribute to material changes or compaction. Without knowing which changes in your material are causing your flow problems, there's no way to design an appropriate accelerated life test. Jun 29, 2016 at 12:30