Which material is described as lightweight, hypo-allergenic and behaves differently at various temperatures?

The material described as lightweight, hypo-allergenic, and one that behaves differently at various temperatures is Optyl. Optyl is a thermoplastic material that is known for its unique properties; it becomes more flexible when heated and returns to its original shape once cooled. This characteristic allows for a comfortable fit in eyewear, as the frames can be adjusted without compromising their structural integrity.

Being hypo-allergenic, Optyl is suitable for individuals with sensitive skin or allergies, making it a popular choice in optical designs. Its lightweight nature contributes to the overall comfort of eyewear, especially for prolonged use. These properties combined make Optyl particularly advantageous for opticians when selecting materials for frames that need to cater to a variety of client needs.

The other materials listed may have their own set of advantages, but they do not share the same combination of lightweight, hypo-allergenic qualities, and temperature-dependent flexibility that Optyl offers.