I am doing a lab and there is one question I can't get. We have the enthalpy of fusion of crystalline polyeythlene, mass, onset temperature and energy required for a phase change of both low density polyethylene and high density polyethylene. They as to calculate the percent crystallinity of both by calculating the fraction of crystalline polymer in the samples. I really have no clue how to go about this I'm stumped. Any help would be greatly appreciated. Thanks.

Question

I am doing a lab and there is one question I can't get. We have the enthalpy of fusion of crystalline polyeythlene, mass, onset temperature and energy required for a phase change of both low density polyethylene and high density polyethylene. They as to calculate the percent crystallinity of both by calculating the fraction of crystalline polymer in the samples. I really have no clue how to go about this I'm stumped. Any help would be greatly appreciated. Thanks.

Answer 1

I realize that you have posted this question once before and got no responses. I regret that I am not able to answer it. I am hoping that another teacher will be able to help you.

I did try "googling" the words <crystalline polyethylene fusion> and came up with several references, some of which you might find helpful. I suggest that you try doing the same, if you haven't already.

Answer 2

You might find chapter 5 of this book on polyethylene properties useful:

http://books.google.com/books?id=OPuWyxwJwJwC&pg=PA177&lpg=PA177&dq=crystalline+polyethylene+fusion&source=web&ots=VpCgGdCVbC&sig=Nc4SaE1AFejpwiDidKjj1WAV0qE#PPA125,M1

Answer 3

To calculate the percent crystallinity of both low density polyethylene (LDPE) and high density polyethylene (HDPE), you need to use the enthalpy of fusion and the energy required for a phase change for each sample.

Here's a step-by-step guide on how to calculate the percent crystallinity:

1. Start by calculating the energy required for a phase change (ΔH_pc) for both LDPE and HDPE samples using the formula:
ΔH_pc = enthalpy of fusion * mass

2. Next, calculate the total energy required for a complete phase change (ΔH_total) for both samples using the formula:
ΔH_total = energy required for a phase change * mass

3. Now, calculate the energy required to melt the amorphous portion (ΔH_amorphous) of each sample using the formula:
ΔH_amorphous = ΔH_total - ΔH_pc

4. Calculate the mass of the crystalline polymer (mass_crystalline) using the formula:
mass_crystalline = ΔH_pc / enthalpy of fusion

5. Finally, calculate the percent crystallinity using the formula:
Percent crystallinity = (mass_crystalline / mass) * 100

Follow these steps separately for both LDPE and HDPE to obtain their respective percent crystallinity values.

Note: The enthalpy of fusion, mass, and energy required for a phase change values should be given in the lab instructions or data provided. Make sure to use consistent units throughout the calculations.

Hope this helps! Let me know if you need further clarification.