Why is PVC shrink film easy to break?

PVC shrink film is very common in the current packaging market, such as the outer packaging of cosmetics, stationery, doors and windows, aluminum, and various stainless steel pipes. Due to the good shrinkage and strong tensile strength of PVC shrink film, as well as the simple and easy operation of packaging, it can be tightly fixed on the surface of the product by heating with a high-power hair dryer or semi-automatic or fully automatic heat shrink machine. However, regarding the outer packaging of some products, some PVC shrink film packaged products are prone to breakage and breakage at a slight touch. 

What is the reason behind this?

4、 The product is not brand new material.