PVC resin is a hard and brittle material with poor impact strength, generally only 3-5 kJ/m. The main reason for the need to improve the impact strength of unplasticized PVC is its sensitivity to notching. Besides, it is necessary to improve its low temperature impact resistance.

By co-blending impact modifiers in PVC polymers, the toughness of PVC materials can be increased．These impact modifiers are polymer elastomers with certain compatibility with PVC, which can make the blending system can maintain the high modulus and high rigidity of UPVC, but also greatly improve its notched impact strength and significantly improve the low-temperature impact strength. Due to the simple and flexible operation of the compounding process and the economy of the compounding modification method, it has been widely used.

(1) CPE

CPE is made of HDPE chlorinated under appropriate conditions, HDPE is chlorinated, the crystallinity is destroyed, thus becoming soft and has the properties of rubber-like elastomer. The content of CPE has a great impact on the modification effect, CPE with a Cl content of less than 25% is not compatible with PVC and cannot be used in the co-blending impact modification of PVC: CPE with a Cl content of 25%-40% Semi-compatible with PVC, is a better impact modifier, including chlorine content of 34%-37% CPE has better processability, dispersion, impact resistance, PVC is a good impact performance modifier: Cl content of 42% or more CPE, and PVC compatibility increases and due to the high content of chlorinated structures on the molecular chain and the chain segment hardened, the glass transition temperature is higher, itself less elastic The CPE cannot be used for PVC blending impact modification.

(2) ACR

ACR-type impact modifiers belong to the core-shell structure copolymer, the core is a class of low cross-linked acrylate rubber polymer, the shell is methyl methacrylate graft copolymer. The structure of the modifier, often through the addition of typical cross-linking monomers for cross-linking, so that its "core" has a good elasticity, "shell" is a high glass transition temperature polymer, easy to separate between the particles, can be more uniformly dispersed to the PVC substrate and PVC substrate interaction, so this type of modifier can improve the impact resistance, but also play a similar role to ACR processing aids, to promote the gelation and plasticization of PVC resin. Promote the gelation and plasticization of PVC resin.

(3) EVA

EVA is a random copolymer of ethylene and VAc it is a rubber-like elastomer similar to CPE, its performance and VAc molecular weight size and content has a great relationship. As a PVC modifier of EVA, its VAc content is generally 40%-50%, it is reported that the impact modification of PVC, EVA content in 5%-10% more appropriate, more than 10% of the material tensile strength, rigidity, impact resistance will be reduced. Although the modification effect of EVA, weather resistance is good, but due to EVA molding at high temperatures to get the profile welding strength is low and the higher the temperature notch impact strength is lower, therefore, it is in the PVC profile, pipe application is a significant downward trend, has been basically replaced by CPE and ACR.

(4) MBS&ABS

MBS is the best material to improve the impact performance of PVC and make transparent products, almost all transparent PVC products use it as impact modifier, its dosage is generally between 8-15 parts.

ABS can improve the impact strength of PVC, as well as improve the appearance quality of products, while playing the role of processing aids to improve the processing performance of PVC. When its dosage is within 30 parts, the impact modification strength of the blended material tends to increase as the dosage increases.

Because MBS and ABS contain double bonds, they have poor weather resistance and are rarely used in PVC window extrusion and door profile extrusion and pipe extruder for outdoor use.