Swinburne University of Technology Sarawak campus

MEE30001 Materials and Manufacturing 2

Lab 1: Polymer processing and testing

1. Compression molding of polypropylene samples for mechanical testing.

Introduction

The methods by which sample materials are prepared and molded influence the mechanical properties of the specimen. Unlike injection molding, the objective of compression molding is to produce test specimens or sheets that are both homogeneous and isotropic. Molded specimens may be made from powder or pellets such as are received directly from a material manufacturer, particles produced in a recycle recovery operation, or from a milled preform or sheet prepared on a two-roll mill. The powder, pellets, particles, preform, or sheet are melted and molded in a mold designed to produce a finished specimen of a given geometry, size, and thickness, or melted and molded in the form of a smooth plaque or sheet of uniform thickness from which desired specimens are cut, punched, or machined.

Procedure

Compression molding is a procedure where a molding material is placed in an open, heated mold cavity. The mold is closed with a top and pressure is applied to force the material to contact the entire mold area. Heat and pressure are maintained until a desired cure time. Different materials require different cure times, temperatures, pressure, and cooling. The compression molder in lab 1115 is a 30 ton Hydraulic Hot Press LS-22071 (Lotus Scientific, Malaysia).

1. Close the guard door. 2. Turn the Disconnect switch (Red knob on yellow panel on the right/west top side of the

compression molder) to the On (closed position). 3. Ensure the EMERGENCY STOP BUTTON IS PULLED OUT. 4. Press CONTROL POWER ON button and the green light will illuminate. 5. Press the HYDRAULIC PUMP ENABLE button and the green light will illuminate. 6. Press the PLATEN HEAT ON button and the green light will illuminate. 7. Select the MANUAL position of the MAN/SEMIAUTO selector switch. 8. Adjust the temperature controller to the desired setpoint. 9. When desired temperature is reached, open the guard door and place mold in between the

two platens then close the guard door. 10. Press and hold the two CLAMP CLOSE buttons. The hydraulics should move the two

platens together. a. If Air cooling is required for your procedure, pull the AIR button to activate the air cooling feature.

11. When the clamp is sealed, you can adjust the pressure with the CLAMP PRESSURE

ADJUSTMENT knob. The max is 15 tons. 12. Leave the mold in place under pressure and heat for your cure time. 13. After your cure time, if water cooling is needed pull the WATER ON button to activate

water cooling. 14. When temperature reaches between 70-80 degrees, press the CLAMP OPEN button. 15. It is now safe to open the guard door and remove the mold. 16. For precautionary purposes, use hot glove to remove the mold from the platens.

Health and safety information for materials used: This machine operates under high temperatures and immense pressure. Never place any body parts in the machine while it is warming up, loading, or unloading. Pay attention to the warning tags on the machine. Never try to bypass any safety features of the machine. To ensure safety, keep the front door closed when the machine is operating. Hazard Control Measures:

Safety glasses Lab coat Heat Resistant Gloves

2. Mechanical testing of polypropylene samples.

Tensile testing of thermoplastics

Standards: AS 1145 (Australian standard), ASTM D 638 (US standard)

Testing equipment

Universal testing machine (T-Machine)

Electronic digital caliper Pro-max.

Method

Measure and record the dimensions of the cross sections of the test specimen;

Clamp up specimen in the crossheads of machine and run the test. Set distance between grips

100 mm

Perform five tensile tests.

Determine the mean and standard deviation of the samples tensile strength (maximum stress

from stress-strain curve)

Save all your data on a USB data key for later analysis

R 76

10 20

60

G 105

150

Figure 1. Tensile test specimen.

TESTING OF PP: RESULTS

Table 1. Measured, recorded and calculated results for tensile testing of PP

Specimen number

1 2 3 4 5 Mean S.D.

Width (d), mm

Thickness (b), mm

Maximum load, N

Maximum stress, MPa

Discussion (Factors effecting reproducibility of tests results).

Conclusion

Determination of polypropylene Melt Flow Index

Standards: ASTM D 1238 (US standard)

Testing equipment: CEA7024F CEAST (Italy)

Settings: Temperature 230 C, weight 2.16 kg

Method

Prepare 6 g of PP in granular form.

Prepare the correct weight and place next to the instrument.

Insert the piston in the barrel for a few minutes (preheating).

Press start on the main menu.

Fill in the field operator your group number.

Press start.

When the temperature is reached the set value insert material in the barrel and manually compact

it using a provided tool.

Insert the preheated piston.

Preheat the material without weight till the acoustic signal.

Manually place the test weight on the piston.

The instrument automatically begins measurements when the set position is reached.

Cut the extruded filament at the end of the test.

The instrument will guide the operator by emitting an acoustic signal at the beginning and

at the end of each test.

Measure weight of the extruded fillament and insert data.

Print out the results

Clean the piston, barrel and the die. Remember to wear thermally insulated gloves.

Polypropylene MFI (MFR)

Mean

Standard deviation

Discussion (factors effecting reproducibility of test results).

Conclusion