Reference no: EM133015593

POLYMER TESTING LABORATORY

EXPERIMENT 2 - Flexural Properties

INTRODUCTION:
Flexural tests are used to measure the stiffness of a material. The stiffness of a material could be a significant factor depending on the end use. Therefor Flexural Modulus and Flexural Strength are important in the polymer industry. The results from these tests are used on most specifications or material data sheets for material suppliers and manufacturers.
AIM:
To carry out flexural modulus and flexural strength (3 Point Bend Test) on two polymer materials and gain an understanding of the measurements and the procedures required to obtain them.

PROCEDURE:
The test specimens are to be measure for thickness and width following the procedure in the relevant standard which is ASTM D 790. (using a micrometer)
The specimen measurements will need to be put into an Excel spreadsheet to determine the average measurements.
The support span needs to be determined by using the average thickness of the specimens (see data sheet provided or ASTM D 790). The supports are then adjusted to the span required and measured as per the data form.
Support Span L = 16 x average thickness (mm)
The speed of the test needs to be calculated using the actual span and thickness. (see the data sheet provided or ASTM D 790). The speed and the average thickness and widths are then put into the Trapezium method before testing can begin.
To operate the Shimadzu AG-IS the PTL Procedure will be used.

As the specimen bends, a graph will be plotted as force vs displacement or stress vs stroke/strain and at the end of the test the results will be presented in a table as the peak force (N), flexural modulus and flexural strength in MPa. The graph should display a line of best fit to the straightest and steepest part of the curve. If this looks like it is in the right location, no changes need to be made but in some cases the line may not fit the graph correctly. In such cases if there is an odd one the graph can be changed or an adjustment can be made by right clicking on the graph and selecting adjustment setting. The curser can then be used to move the line to the best fit and then right click again to get the menu and select the adjustment setting again to confirm the change. This will also change the result in the table.
Record the results and save the test.

PROCEDURE FOR THE DETERMINATION OF FLEXURAL MODULUS & FLEXURAL STRENGTH

ASTM D 790

1. Measure the thickness and width of each of the five specimens to be tested using a micrometer and record on the appropriate ‘Dataform'. Determine the average thickness of the specimens. This is needed to calculate the speed of the test.

2. Click on the grey part of the window to bring up the ‘Navigation Bar'. If the method does not need to be changed but specimen dimension need to be entered select ‘Specimen Sizes'. In this window put in each specimen's thickness and width and the support span (49.64 mm) and then click on ‘Finish' to return to testing window.

3. If other parameter in the test method also need to be changed such as; specimens sizes,
speed, range, chart (x,y scales), select ‘Re-analyse & Edit Method'.

When all changes have been made, click on ‘Finish' at the bottom of the window.

4. Place the first specimen on the support span (centralised). The Cross Head can be manually lowered to just above the specimen. Press the ‘Position Zero' button on the hand held control.

5. Press ‘Start' on the hand held control panel or click on the screen to bring up the ‘Navigation Bar' and click on ‘Start' and then ‘Begin Test'.

6. Run the test until the graph has reached a peak (max.) force and started to go down. Press ‘Stop' on the hand held control panel.

7. The Cross Head can return to its start position by pressing the ‘Return' button on the hand held control for 1 second.

8. Remove the specimen from the supports. Replace it with the next specimen and repeat from step 4. Until all specimens are tested.

9. Once all five specimens have been tested click on the screen to get the ‘Navigation Bar' and select ‘Save Test' or save via menu at the top of the screen.

10. Write down results in the appropriate Dataform. If the line on each specimen's curve is not in the correct position - steepest straightest part of the curve this can be changed either on the graph or in ‘Reanalyse' and ‘Data Processing'.

11. Flexural Modulus average and standard deviation can be calculated by going into an Excel file

Guidelines for Writing Laboratory Reports

Student are often required to provide the details of their laboratory experiments in the format of the traditional laboratory report which may contain headings such as Introduction, Method, Results, Discussion and Conclusions, and References. The most important factor in getting a good grade (besides using the format correctly) is to give the examiner of your report (in this case, your Lecturer) evidence of your ability to interpret experimental data, and relate the data to the theories covered in the academic discipline. Your audience is the examiner who is likely to know more than you about the subject.
However, this is irrelevant because your aim is to demonstrate your understanding of the topics being investigated, and your skill in explaining observations and thinking about their implications.
When writing your report, you should use formal and precise expressions in the report; avoid slangs and colloqialism. Also, write in full sentences with correct grammar and spelling; avoid long-winded and potentially confusing sentences. Limit your use of personal pronouns (eg, I, you, we), emotionally loaded words (eg, wonderful, useless, lovely), and casual or ambiguous expressions (eg, the reaction carried on for 10 minutes). Use of contractions (eg, isn't, there's) should also be avoided.
In order to help you in the writing of your technical laboratory report, the major headings of such reports are illustrated below.
Title Page: It is the first page of the report (following the Assignment Cover Sheet) and it should contain the following information:
Subject's Title and Code Title of Experiment
Name(s) of Author(s) of the Report Date of Experiment

Abstract: Briefly describe the purpose of the experiment, and summarise the most important finding of your investigation.
Introduction: Describe the topic you are investigating in this experiment, and explain the theory which covers the particular aspects of this topic. Under this heading, you can also clearly state the objective(s) of the laboratory experiment you are performing.
Experimental Procedure: In this section, you describe the procedure of the laboratory experiment by outlining step-by-step what you have done in the laboratory; the statements should all be in the past tense. You should avoid copying the procedure from the handout which you have received because you may have necessarily performed the experiment in a different manner than what is outlined in the handout; the procedure in the handout is always in the present tense.
Calculation Method and Results: The method of calculation and the relevant equations (with sample calculations) are included under this heading. If possible, all experimental errors should be identified and quantified.
Your results can be presented in Tables and Figures (which include graphs, pictures and any other images). Figures and Tables are numbered in the order in which they appear in the text. All tables and figures must have meaningful captions not just "Graph of Y vs X". Some examples of figure and table captions are:

While title of tables are provided at the top of the table, captions for figures appear at the bottom of the diagram. Pay particular attention to graphs. Each graph should have its own caption/title which must be descriptive. For example, if you have a graph showing the effect of temperature on efficiency, then do not use the caption "Temperature vs Efficiency". Rather, use "The Effect of Source Reservoir Temperature on the Thermal Efficiency of the Stirling Engine". Use POINTS for experimental data and LINES for model or theoretical predictions. You should not attempt to curve fit every set of data. There is no point putting a linear curve fit through data unless you have a physical reason for believing that the response should be linear. Do not force the lines to go through every data point - this is physically unreasonable and not consistent with experimental error in your data. Label your axes clearly and specify the units.
Discussions and Conclusions: In this section, the results of your laboratory experiments should be compared with each other, with similar results from other sources, and with results of theoretical calculations. These findings should be discussed here, and appropriate conclusions should be drawn.
When discussing your results, you need to identify the trends of the reulsts and explain why they are as they are. You should attempt to answer the following questions: Do the results agree with the theory? Why not? Were there any experimental limitations that might have affected the accuracy of your data? Were your results expected?
The discussion is primarily about what the results mean. For example, when you obtain a graph of a desired form (eg, a straight line), state that this indicates a certain relationship between the variables - do not simply find the value of the slope of the line and forget to say, for instance, that the data supports the theoretical linear relationship between the pressure and liquid flow rate. Include uncertainties in your data so that statements such as "the data were in good agreement with literature values" can be assessed. Claiming that the difference between your results and the expected values is very small and hence your result is accurate is not valid; the uncertainty in your result is the indication of accuracy.
Finally, present a short conclusion for the experiment. State whether the aim of the experiment has been achieved or not. Summarise what you did and what your key findings were. This is NOT a repetition of your discussion - it is your conclusion. Include key numerical data, along with experimental uncertainties, and comparisons with expected values. Where appropriate, summarise the limitations of your work as well as mentioning future work that should be done.

POLYMER TESTING LABORATORY

EXPERIMENT 3 - Izod Impact Strength

INTRODUCTION:
Izod Impact Strength is important in the polymer industry. The results from these tests are used on most specifications or material data sheets for material suppliers and manufacturers. Impact Strength measures the ability of the plastic to withstand a rapidly applied stress. The instrument being used to obtain this information is called an Izod Impact Instrument. This instrument uses a hammer of known energy to impact a specimen in a pendulum movement. The energy absorbed by the specimen from the hammer is given in Joules per metre (energy per width of specimen). The V notch used gives a good indication of the notch sensitivity of the material.
AIM:
To carry out impact strength on two polymer materials and gain an understanding of the measurements and the procedures required to obtain them.

PROCEDURE:
This procedure can be used in conjunction with the PTL Procedure and ASTM D256.
10-12 specimen are needed for testing. Number them. The specimens will all be pre- notched with a Notching apparatus and conditioned prior to testing. A clean notch is required.
The test specimens are to be measured for thickness and width and width behind the notch following the procedure in the relevant standard which is ASTM D 256. (using a flat micrometer and wedge micrometer). Convert from mm to m.
Mount the first specimen in the clamp at the base making sure the specimen holder is the correct size and the specimen is held against the side of the holder. The notch in this experiment will be facing towards the impact (hammer). The apex of the notch should be in line with the top of the support.

Release the hammer. The hammer will swing down and hit the specimen where the notch is located. Note the type of break and the energy reading from the dial in joules shown on the large dial. If the 2 Joule hammer is used then the reading should be taken from the scale for that hammer. The reading in joules is divided by the specimen thickness in metres to obtain Joule/meter. Record the results and the type of break.
Calculate from the results the average Impact Energy and the standard deviation.

POLYMER TESTING LABORATORY

EXPERIMENT 1 - Tensile Strength

INTRODUCTION:

Tensile properties are important in the polymer industry. The results from these tests are used on most specifications or material data sheets for material suppliers and manufacturers. This test measures the resistance of the materials to deformation and how much extension the material can withstand before breaking.
Tensile Strength is calculated by dividing the maximum load in Newton by the average original cross-sectional area (mm2). The result will be expressed in Megapascals (MPa). Tensile strength at yield (tensile stress at yield) and tensile strength at break (tensile stress at break) can be obtained depending on the material.
Percentage Elongation is the change in gage length relative to the original gage length in percentage. Percent Elongation at Yield is the extension or change in gage length at the point of yield divided by the original gage length x 100.
Percentage Elongation at Break is the extension or change in gage length at the point of break divided by the original gage length x 100.
Modulus of Elasticity or Tensile Modulus is determined by extending the initial linear portion of the load extension curve and dividing the difference in stress corresponding to any segment of section on this straight line by the corresponding difference in strain. Again this measurement uses the average original cross-sectional area in the calculation. The result is expressed in MPa.
AIM:

In this experiment you will test two materials to ISO 527 to determine the tensile strength, percentage elongation and tensile modulus. The test will be carried out under particular conditions of preparation, temperature, humidity and testing speed as tensile properties can vary depending on the environment and also by the way they have been prepared. Comparison testing should always be carried out using the same preparation, conditions and test parameters. All these details/parameters will be recorded.

PROCEDURE:

All the test specimens will have been conditioned for 48 hours at 23°C +/- 2°C and 50 % +/- 5% Relative Humidity.
The testing carried out will be undertaken at these same conditions. This should be checked before starting the test by pushing the button on the wall mounted digital Testo Temperature/Humidity monitor. Testing should only start if the readings are within tolerances.
Follow the PTL Procedure for the Shimadzu testing machine and ISO 527.

Measure each of the test specimens in the gage area (the narrow part of the dumbbell). The thickness and width will need to be measured several times and Excel will be used to calculate the average dimensions for each specimen and as a total. This will be used to determine the cross-sectional area. Measurements will be taken using the calibrated micrometer. These measurements are required in the Trapezium software to determine the strength in Mega Pascals (MPa) after the test.
Go through PTL Procedure.

Once the Shimadzu testing machine is running and the Extensometer has gone through its initialisation go into the Trapezium software, skip login and choose the ‘Select the Method and Test' option in the main menu. Select the tensile test "ISO 527 20 kN" method.
Specimen dimensions, speed etc will be put into the test.

Place the specimen in the grips and tighten. Click on Extensometer and select middle point. This will adjust the extensometer arms to sit in the middle between the grips.
Zero the machine.

Press the ‘Start' button on the hand held device twice or click on the screen.

Once the specimen has broken, follow the instruction for the extensometer that pop up on the screen. Press the ‘Return' button. Once the machine has returned to its original position remove the broken specimen and put in the next specimen. Repeat the procedure.

RESULTS:

Results will automatically be calculated and will be displayed in the table. Adjustments may need to be made. Normally the graph will be displaced in stress vs strain.
Record the results in the data sheet. Raw data will be used to obtain this graph.

Attachment:- Guidelines for writing lab experiment.rar