It takes some work, but you can learn to spot the differences between products and, hopefully, avoid future callbacks. Here's a start.
As Much Art as Science
Creating composites and PVC often is compared to cooking, but lots of chefs would be sorely tested if they tried to whip up a deckboard or piece of trim. That's because, unlike in a kitchen, you can't count on the ingredients to be consistent from one day to another.
Wood and plastic typically make up roughly 85% to 95% of the ingredients' total weight. Most of the wood consists of cast-offs from flooring factories. And except for virgin PVC flakes, all the plastic had a previous life as well. WPC and PVC manufacturers work constantly to get reliable streams of raw product, but if the wood flour has a different mix of species or the recycled plastic shipment was heavier on low-density polyethylene film, the manufacturer may need to adjust its formula.