Embedding Programs
There is a choice of 3 embedding programs in the EMS POLY III catering for 3 different solvents. They have been pre-programmed for general use but the user can change the programs to fit specific specimens.
Program 1: for removal of ethanol Program 2: for removal of acetone Program 3: for removal of propylene oxide
The programs each have up to 5 steps that bring the specimens from the resin/solvent mix through removal of the solvent into pure resin.
The individual steps, using Program 1 as an example: The Program starts at a temperature of 25°C. The vapor pressure of ethanol at that temperature is ~8kPa.
Note: Steps 4 and 5 are mandatory steps when working with low vapor pressure solvents such as ethanol. More volatile solvents can usually be removed in a shorter procedure only using Step 3, or using Step 3 and 4.
Step 1 serves the gentle removal of air bubbles that may have been introduced.
Step 2 aims at the bulk removal of ethanol, using a pressure of 15kPa at 25°, which is slightly above the max vapor pressure. Ethanol will evaporate from the surface of the resin/solvent mixture. The pressure will increase as a result.
Evaporated ethanol is diluted with air that is admitted into the recipient and then pumped away. These events are controlled by the setting of global variables:
∆P1, which relates to the pressure increase resulting from evaporation and
∆P2, which determines how much air is admitted to dilute the evaporated solvent.
The technical manual provides information on how to set the parameter values for these variables.
When, as a result of evaporation, the pressure has increased by preset threshold level ∆P1, the air admission valve opens. The time that passes before this happens is in the order of minutes and depends on the number of specimens, more accurately on the total evaporating area in the recipient, the pressure in the recipient and on the volatility of the solvent.
Example: Let us assume ∆P1 was set to 1kPa and ∆P2 to 25kPa, which are recommended settings.
When the pressure in the recipient has gone up by 1kPa to 16-17kPa (error margins ± 1kPa) the air admission valve opens. The pressure in the recipient increases as a result and when it has gone up by 25kPa the air admission valve is closed again. The pump is activated and diluted ethanol vapor is removed until the set pressure of 15kPa has been reached again and the pump switches off. As long as ethanol keeps evaporating this process will be
repeating itself, initially with short time intervals, later with gradually increasing intervals. When the interval time has increased to >30 min, indicating that the bulk of the ethanol has been removed, the instrument automatically switches to Step 3, regardless of whether the set time (in the default set up this is 5 hrs) has not yet been completed.
Step 3 starts with raising the temperature and lowering the pressure. Residual ethanol is more easily removed under these conditions and the process described for Step 2 continues until the interval time between pump cycles has increased to >30 min. Then a flush/pump cycle is started: the air valve is opened and the pump switched on so the pump works under gas ballast conditions, improving evaporated solvent removal. This flush/pump cycle is repeated twice within a few minutes, after which the system is pumped down to the set vacuum level. After 30 min the process is repeated. After a total number of twelve of these cycles the system goes to Step 4.
Step 4 starts with raising the temperature after which the same process as described for Step 3 is activated.
Step 5 as Step 4. The program ends after Step 5 has been completed.
The Technical Manual describes programming steps as well as deleting steps.
Polymerization programs There is a choice of 2 programs for polymerization in the EMS POLY III. They have been pre-programmed for general use but the user can change the programs to fit specific specimens.
Program 4: for 24 hr polymerization (temperature curing)
Program 5: for 48 hr polymerization (temperature curing)
The programs each have up to 5 steps.
The individual steps are explained using Program 4 as an example. Note: each step switches to the next one based on the programmed time, unlike the steps in Programs 1, 2 and 3.
When embedding has been completed, specimens need to be polymerized. The programs use a minimum of 2 steps.
Step 1 raises the temperature over a period of approximately 30-40 minutes to the 60°C whereas the vacuum is set at 10kPa. Under these conditions the viscosity of epoxy resin is much reduced and the specimens yield the last traces of solvent.
Step 2 starts with releasing the vacuum and slightly raising the temperature. The start of step 2 is the preferred moment for the BEEM vials to be topped up with pure resin. After the polymerization time has passed the polymerized specimens are removed from the recipient.
Table 2: Factory preset programs 1-3 and steps
Program 123 Solvent Resin
ethanol
Step 1 Duration
Step 2 Duration
Step 3 Duration
Step 4 Duration
Step 5 Duration
Temperature 25°C Pressure
Temperature 25°C Pressure
Temperature 30°C Pressure
00:05:00 65kPa
05:00:00 15kPa
02:00:00 10kPa
Temperature 35°C Pressure
02:00:00 10kPa
Temperature 45°C Pressure
02:00:00 10kPa
acetone
00:05:00 25°C
65kPa
05:00:00 25°C
30kPa
02:00:00 30°C
20kPa
02:00:00 30°C
10kPa
02:00:00 45°C
10kPa
propylene oxide
00:30:00 15°C
100kPa
00:05:00 15°C
65kPa
05:00:00 20°C
60kPa 6 hr. flush 6 hr. flush 6 hr. flush
02:00:00 25°C
40kPa 6 hr. flush 6 hr. flush 6 hr. flush
05:00:00 45°C
20kPa 6 hr. flush 6 hr. flush 6 hr. flush Table 3: Factory preset programs 4-5 and steps
Program 45 Polymerization short Resin
Step 1 Duration
Step 2 Duration
Step 3, 4, 5 Duration
Temperature Pressure
Temperature 60°C Pressure
Temperature 65°C Pressure
2:00:00 10kPa
22:00:00 100kPa
unused long epoxy methacrylate epoxy methacrylate
2:00:00 60°C
10kPa
46:00:00 60°C
100kPa unused
P.O. Box 550 • 1560 Industry Rd. • Hatfield, Pa 19440 Tel: (215) 412-8400 • Fax: (215) 412-8450 email:
sgkcck@aol.com or
stacie@ems-secure.com
www.emsdiasum.com
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