Question

Compression moulded isotropic polypropylene film exhibits

• A. spot pattern
• B. circular ring pattern
• C. circular ring and spot pattern
• D. arc pattern

Hint:

In X-ray diffraction analysis, crystalline materials typically show distinct spot patterns, while isotropic and amorphous materials exhibit circular ring patterns due to the lack of long-range order in their atomic structures.

Answer 1

The Correct Option is B

Compression moulded isotropic polypropylene film is a type of polymer that has been processed in such a way that its molecular structure is randomly oriented. This results in an isotropic material, meaning it has the same properties in all directions. When such a film is subjected to X-ray diffraction analysis, the resulting pattern provides insights into its structural properties.

Step 1: Understanding X-ray Diffraction Patterns.
X-ray diffraction (XRD) is a powerful technique used to analyze the structure of materials. When a material is irradiated with X-rays, the X-rays interact with the atomic planes in the material, causing diffraction. The diffraction pattern depends on the arrangement of atoms in the material. Crystalline materials typically exhibit distinct spot patterns, as the atomic planes are regularly spaced and oriented in a predictable manner. On the other hand, materials with isotropic structures (such as amorphous or unoriented materials) tend to produce patterns that are more diffuse and uniform.

Step 2: Isotropic Materials and Diffraction Patterns.
In the case of compression moulded isotropic polypropylene films, the polymer chains are oriented in a random fashion. This means the atomic planes are not aligned in a regular or periodic structure, as would be the case with crystalline materials. As a result, X-ray diffraction of isotropic materials typically produces a circular ring pattern. This pattern is indicative of the lack of long-range order in the material. The diffraction rings arise from the superposition of diffraction from many different crystal planes, each contributing to a part of the circular pattern.

Step 3: Analyzing the Options.
- (A) Spot pattern: This pattern is typical of crystalline materials with highly ordered atomic structures. Since polypropylene film is isotropic, it does not exhibit a spot pattern. Therefore, this option is incorrect.
- (B) Circular ring pattern: This is the correct answer. As explained earlier, isotropic polypropylene films exhibit circular rings in their diffraction patterns due to the random arrangement of polymer chains. This is a hallmark of materials that lack long-range order, like amorphous or isotropic substances.
- (C) Circular ring and spot pattern: This option suggests the presence of both a circular ring and a spot pattern. However, this is not typical of isotropic materials. The presence of both patterns would imply some degree of crystallinity, which is not the case for isotropic polypropylene. Therefore, this option is incorrect.
- (D) Arc pattern: An arc pattern would suggest some partial ordering or directional alignment in the material. Isotropic materials, by definition, do not show such partial alignments, so this option is also incorrect.

Step 4: Conclusion.
The correct answer is (B) circular ring pattern, as isotropic polypropylene films exhibit this type of diffraction pattern due to their lack of long-range atomic order.

Final Answer: \text{(B) circular ring pattern}