The key "ingredients" that make up the vinyl frame for a window can vary greatly among manufacturers. Each additive to a company's vinyl "recipe" helps determine the long-term characteristics of the final product. It's weatherability and resistance to impact, for example. Or how it handles the summer heat and winter chill.
At Milgard, they understand the impact their vinyl compounds have on their window products over time. That's why they choose only quality materials, at optimal levels, whatever their price.
Impact resistance: A major consideration when working with vinyl is its inherent brittleness. Without a plasticizer, even properly processed vinyl can be as brittle as glass. So Milgard blends their compounds to an exacting balance of rigidity and flexibility. Rather than use a liquid plasticizer (like vegetable oil), they use a solid impact modifier.
Ultraviolet: The sun's ultraviolet light can be quite damaging to many materials - including vinyl. So in order to maintain a window's finish and strength over time, an ultraviolet inhibitor must be added to the "mix." It's a sunscreen of sorts that protects the window from the sun's harmful rays. Milgard uses a precise level of ultraviolet barriers to make sure your vinyl windows will continue to look - and perform beautifully for a lifetime. Many lesser-grade vinyl products use calcium carbonate - ground-up limestone - or what we commonly call "chalk". Milgard uses titanium dioxide exclusively as a UV inhibitor.
One of the oldest myths of vinyl compounding is that first-run, or "virgin" vinyl, is a better product. Milgard thought so also when they first began producing vinyl - and soon learned otherwise. After they tested different batches they decided to include specific percentages of regrind (recycled Milgard extrusions) to the mix. The finished product is now more impact resistant and has enhanced edge lines.
Here's some "ammo" against anyone stating that vinyl with regrind loses strength: Milgard has shown that they can extrude, chop up, and re-extrude their compound up to thirteen times without loss of performance!