Discussion on Impact Strength

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  • Topic: Polymer, Polyethylene, Izod impact strength test
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  • Published : May 18, 2013
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Experiment 1 Part B: Impact Strength
Group Number: Group 1
Discussion
General Purpose Polystyrene (GPPS)
No.| Width(A), mm| Thickness(W),mm| Energy, J| Joules/Fracture Surface, J/m²| 1| 11.16| 3.27| 0.110| 3014.26|
2| 11.17| 3.28| 0.116| 3166.15|
3| 11.17| 3.27| 0.107| 2929.43|

High Impact Polystyrene (HIPS)
No.| Width(A), mm| Thickness(W), mm| Energy, J| Joules/Fracture Surface, J/m²| 1| 11.06| 3.28| 0.295| 8131.92|
2| 10.89| 3.25| 0.251| 7091.90|
3| 11.05| 3.29| 0.281| 7729.44|

High Density Polyethylene (HDPE)
No.| Width(A), mm| Thickness(W), mm| Energy, J| Joules/Fracture Surface, J/m²| 1| 10.91| 3.20| 0.193| 5528.19|
2| 10.85| 3.20| 0.195| 5616.36|
3| 10.87| 3.20| 0.197| 5663.52|

Polypropylene (PP)
No.| Width(A), mm| Thickness(W), mm| Energy, J| Joules/Fracture Surface, J/m²| 1| 11.00| 3.24| 0.108| 3030.303|
2| 11.11| 3.25| 0.115| 3184.934|
3| 11.10| 3.27| 0.118| 3250.957|

Average impact strength obtained for the specimens:
Specimen| Joules/Fracture Strength, J/m²|
GPPS| 3036.61|
HIPS| 7651.09|
HDPE| 5602.69|
PP| 3155.40|

8.1 HIPS has the highest impact strength while GPPS has the lowest impact strength. HIPS has the highest impact strength of 7651.086J/m² due to the addition of polybutadiene into GPPS during polymerisation imbues it with some of its properties. Thus, this increases the impact strength of the material.

According to the results, HIPS has an impact strength of 5602.69 J/m2 while GPPS has an impact strength of 3036.61 J/m2. This evidently proves the addition of polybutadiene increases the impact strength of HIPS.

During polymerisation, the addition of polybutadiene prevents the polymer chains from aligning. This means that there will a reduction of crystalline structures that can be formed. This results in a larger amorphous area, giving it the properties of an amorphous polymer. Since it is...
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