What type of material is described as a thermoplastic molding material that can be molded under heat?

Cellulose propionate is indeed a thermoplastic molding material that can be molded under heat, making it suitable for applications such as eyewear frames. Thermoplastics are characterized by their ability to soften upon heating and harden upon cooling, which allows them to be reshaped multiple times without significant degradation.

Cellulose propionate stands out within the context of eyewear due to its lightweight nature, flexibility, and impact resistance. These properties enable manufacturers to create comfortable, durable frames that can be easily adjusted for fit and style. The material is also known for its clarity and ability to accept various surface finishes, making it visually appealing for eyewear applications.

In contrast, while Optyl is another thermoplastic known for its shape retention and lightweight properties, it is not specifically referred to as cellulose propionate. Cellulose acetate is also a thermoplastic and commonly used in eyewear, but it is distinct from cellulose propionate in chemical structure and properties. Polypropylene, although a thermoplastic, is generally not used for eyewear due to its lower clarity and less favorable aesthetic properties compared to cellulose-based materials.