PVC-U pipes have poor impact resistance in daily engineering applications, so that there are many unsafe factors in the application process, which indirectly reflects the shortcomings of PVC-U pipes are high brittleness and poor cracking and impact resistance. The main method for toughening modification of PVC is to add impact modifiers in the PVC formula to make the material have good toughness and improve the ability of the pipe to resist load. When the impact modifier is added to a certain amount of PVC, its toughness will reach a transition, that is, from a complete brittle fracture to an incomplete ductile fracture, achieving super toughness, and its toughness is increased many times. When this super-tough PVC mixture is applied to plastic water supply pipes to make PVC-M pipes (also known as PVC-A pipes), the use coefficient will be greatly improved, and the design stress will be greatly improved. For toughened and modified PVC M pipes, different countries use different names. The United States and Australia called PVC-M, Japan and the Netherlands called high-impact PVC pipes PVC-HI, and the United Kingdom named PVC-A.

In addition to the advantages of PVC U, such as light weight, good water tightness, sanitation, convenient construction and installation, and long service life, PVC M also has its unique toughness, impact resistance, environmental cracking resistance, chemical resistance, etc. It can be widely used in drinking water transmission and distribution pipe network and industrial and agricultural production water pipe network.