Question

discussion questions: 1. the mfr is considered a guideline, but not a definitive measure of processing ease for injection molding. why might that be? 2. what significant set - up parameters on the lmfi 5000 might change for other polymer types? 3. what material property significantly affects the melt flow rate? how does the mfr correlate with the property? 4. list the melt flow rate results for pp or pe here. find and record the corresponding mfr value given by astm d1238. compare the average mfr to the astm d1238 value. numerical comparison is expected. 5. based on its mfr, what general conclusions can be drawn about the relative ease of processing your polymer, compared to other polymers listed in astm d1238? 6. what general conclusions, if any, can be drawn about the physical and thermal properties of the polymer based on its mfr?

Explanation:

Step1: Answer question 1

MFR is a simple test. It has inherent variability and doesn't account for all factors in injection - molding like mold design, cooling rate etc. So it's a guideline not a definitive measure.

Step2: Answer question 2

For different polymer types on LMFI 5000, significant set - up parameters are temperature (affects melt viscosity) and die diameter (affects flow resistance).

Step3: Answer question 3

Molecular weight significantly affects MFR. There is an inverse correlation: lower molecular weight polymers have higher MFR as they flow more easily.

Step4: Answer question 4

To answer this, one needs to conduct MFR tests on PP or PE, record the results, find the ASTM D1238 values, and calculate the average of the test results to compare numerically. Without actual test data, a specific numerical comparison cannot be provided.

Step5: Answer question 5

If a polymer has a higher MFR compared to others in ASTM D1238, it generally has an easier processing in injection - molding as it flows more readily under the same conditions.

Step6: Answer question 6

A high MFR indicates lower molecular weight polymers. These polymers typically have lower melting points and lower mechanical strength (due to weaker intermolecular forces), but better flowability during processing.

Answer:

1. MFR is a simple test with variability and doesn't account for all injection - molding factors.
2. Temperature and die diameter are significant parameters for different polymer types on LMFI 5000.
3. Molecular weight affects MFR inversely: lower molecular weight means higher MFR.
4. Conduct tests, record results, find ASTM values and compare numerically (actual data needed).
5. Higher MFR generally means easier processing compared to other polymers in ASTM D1238.
6. High MFR implies lower molecular weight polymers with lower melting points, lower mechanical strength and better flowability.