Which of the following properties is/are true for thermoplastics?

Options

A. The intermolecular forces of attraction are intermediate between elastomers and fibres
B. They have cross-linking between them
C. They cannot be molded by heating
D. All of the above

Answer

To determine which properties are true for thermoplastics, we will analyze the characteristics of thermoplastic polymers step by step.

### Step 1: Understanding Thermoplastics
Thermoplastics are a type of polymer that can be molded and remolded upon heating. They do not undergo any significant chemical change during this process, which allows them to be reshaped multiple times.

**Hint:** Remember that thermoplastics can be reshaped when heated, unlike thermosetting plastics.

### Step 2: Intermolecular Forces
Thermoplastics have intermolecular forces that are intermediate between elastomers (which have weak forces) and fibers (which have strong forces). This means that thermoplastics have moderate strength and flexibility.

**Hint:** Compare the strength of intermolecular forces in elastomers, thermoplastics, and fibers.

### Step 3: Crystalline and Amorphous Regions
Thermoplastics possess both ordered crystalline regions and amorphous (non-crystalline) regions. This structure contributes to their mechanical properties and behavior when heated.

**Hint:** Think about how the arrangement of molecules affects the physical properties of materials.

### Step 4: Cross-Linking
A key characteristic of thermoplastics is that they do not have cross-linking between their polymer chains. This lack of cross-linking allows them to be melted and reshaped easily.

**Hint:** Recall that cross-linking in polymers generally leads to thermosetting properties, which are different from thermoplastics.

### Step 5: Molding Process
Thermoplastics can be molded by heating. This is one of their defining features, as they can be reshaped multiple times without undergoing any chemical change.

**Hint:** Consider how heating affects the physical state of thermoplastics compared to thermosetting plastics.

### Conclusion
Based on the analysis:
- **Statement 1**: True (intermolecular forces are intermediate between elastomers and fibers)
- **Statement 2**: False (thermoplastics do not have cross-linking)
- **Statement 3**: False (they can be molded by heating)
- **Statement 4**: False (not all statements are true)

Thus, the correct answer is that only **Statement 1** is true regarding thermoplastics.

### Final Answer
The correct property true for thermoplastics is: **Intermolecular forces are intermediate between elastomers and fibers.**