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 more amorphous having the characteristic of irregular spacing between its molecules, it makes HIPS tough and therefore able to within sudden impact making it the highest impact strength.
GPPS on the other hand though it is amorphous in nature, it does not has the addition of polybutadiene and thus it will lose out to HIPS in impact strength test. Furthermore, as it is amorphous, there is no regular spacing between the molecules thus it is brittle making it unable to withstand the stress applied on it therefore it has the lowest impact strength of 3036. 61J/m? HDPE has the second highest impact strength of 5602. 689J/m? due to its crystalline structure.
As it has a crystalline structure, the molecules will be packed together closely due to the stronger intermolecular forces of attraction and this gives HDPE the characteristic of stiffness making able to withstand impact well. Thus it has a moderately high impact strength. According to the results, PP has an impact strength of 3155. 398 J/m2. It has a slightly higher impact strength than GPPS. PP is semi crystalline which means it is arranged in a regular pattern. Hence, when a sudden impact was given to PP, its resistance to the sudden impact was low compared to HIPS, which has a higher impact strength. . 2 The Izod Impact Test is a method to determine the impact strength of materials. The width and thickness of the specimens is attained by measuring using a vernier caliper. The specimen is clamped vertically with the notch facing the pendulum. When the pendulum swings downwards impacting the specimen at the bottom of its swing, the machine will be able to determine the fracture strength of the specimen. Hence, by comparing the results of the different specimens, we will be able to rank the materials by their impact strength.