Trivex (PPG) Optical Polymer: High Abbe Value (45), Tensile Strength & Rimless Drill-Mount Resistance

While polycarbonate is a thermoplastic squeezed under violent pressure, Trivex is a quasi-thermoset polyurethane polymer cured slowly via thermal polymerization. This produces three major structural advantages:

1. Zero Internal Mold Stress: Cast molding eliminates the optical birefringence and rainbow swirls ubiquitous in polycarbonate.
2. Ballistic Impact Protection: Exceeds MIL-PRF-32432A ballistic fragmentation standards ($15\text{--}16\ \text{Joules}$ impact absorption).
3. Optical Abbe Purity: At $V_d = 45$, Trivex delivers chromatic dispersion nearly identical to CR-39 ($58$), with zero perceptible color fringing across the entire lens aperture.

In 3-piece rimless drill-mount eyewear, the entire frame structure is anchored through holes drilled directly through the temporal and nasal edges of the lens:

$$\text{Tensile Pull Resistance: } \text{Trivex } (\mathbf{60\text{--}80\ \text{kgf}}) \gg \text{Polycarbonate } (35\ \text{kgf}) > \text{CR-39 } (15\ \text{kgf})$$

Polycarbonate drilled holes notch-crack and spider-web within months from flexing strain or solvent exposure (alcohol lens sprays). Trivex does not notch-fracture and is 100% impervious to acetone, alcohol, and skin oils.

The only engineering limitation of Trivex is its refractive index ($n_d = 1.530$). For mild prescriptions (Plano to $\pm 3.00\ \text{D}$), its ultra-thin $1.0\ \text{mm}$ center thickness makes it thinner than CR-39. However, for prescriptions $> \pm 4.50\ \text{D}$, edge thickness increases noticeably compared to 1.60 or 1.67 thiourethane resins.