Here are the similarities and differences between PVC (Polyvinyl Chloride) and PVDC (Polyvinylidene Chloride):

Similarities:

1. Chemical Composition: Both PVC and PVDC are thermoplastic polymers that contain chlorine in their chemical structure.
2. Barrier Properties: Both materials exhibit good barrier properties against moisture, oxygen, and other gases, making them suitable for packaging applications.
3. Transparency: Both PVC and PVDC can be manufactured in transparent forms, allowing visibility of the packaged contents.
4. Processability: Both materials can be easily processed through various techniques such as extrusion, injection molding, and calendaring.

Differences:

1. Chemical Structure: PVC is a vinyl polymer with a repeating unit of CH2=CHCl, while PVDC is a vinylidene chloride polymer with a repeating unit of CH2=CCl2.
2. Barrier Performance: PVDC has superior barrier properties compared to PVC. PVDC films provide excellent moisture and gas barrier, offering better protection to sensitive products such as pharmaceuticals and perishable foods.
3. Thermal Stability: PVDC has higher thermal stability than PVC. It can withstand higher temperatures without undergoing significant degradation.
4. Cost: PVC is generally less expensive compared to PVDC, making it more widely used in various applications, including pipes, cables, and some packaging applications.
5. Environmental Impact: PVC has been associated with environmental concerns due to the release of chlorine and dioxins during production and disposal. PVDC is considered more environmentally friendly as it does not release chlorine or dioxins during its lifecycle.

It’s important to note that PVC and PVDC have different properties and are suited for different applications. PVDC is often used in high-barrier packaging applications where superior barrier properties are required, while PVC finds applications in a wide range of industries due to its versatility and cost-effectiveness.