Chlorinated Polyethylene (CPE) is chlorinated from High-Density Polyethylene. As a kind of PVC processing modifier, chlorine content of CPE is 35-38%. Because CPE has performances of weather resistance, coldness resistance, oil resistance, flame retardancy, impact resistance, chemical stability and good compatibility with PVC Resins, CPE has been the most widely used impact modifier. In general, performances of CPE are determined by two main factors as below:-
1. HDPE’s Molecular Structure
Molecular structures and performances of PE homopolymer HDPE have certain differences due to different workmanship used for the polymerization of PE, thus performances of CPE chlorinated from HDPE with different properties are also different. Therefore, CPE manufacturers must choose suitable HDPE in powder type designed for the production of quality CPE Resin.
2. Chlorination Conditions
As PVC impact modifier, CPE is usually manufactured with the aqueous-phase suspension chlorination method. The main conditions of such method involves light energy, dosage of initiator, reaction pressure, reaction temperature, reaction duration and neutralization reaction conditions. The theory of the chlorination of PE is simple, but the mechanism of chlorination is complicated.
There are plenty of poor CPE on the market. In general, poor CPE include two major type, one is manufactured by unqualified manufacturers with under-developed chlorination method, while the other is CPE adding some Calcium Carbonate powder or talcum powder as a way of unfair competition.
Regarding the former poor CPE, buyers can avoid loss by purchasing those manufactured by qualified and well-known manufacturers. But for the latter poor CPE, many people don’t have enough knowledge for it. As we all know, the prices of Calcium Carbonate and Talcum Powder are 400-500RMB/Ton, while CPE is 8000-8500RMB/Ton. Some illegal manufacturers add some cheap materials as filler and sell at a rate lower than market price to earn market shares. Generally, the price of this type of CPE is 7000-8000RMB/Ton even much lower to 5000-6000RMB/Ton.
If such poor CPE is used in PVC products processing as impact modifier, the dosage of CPE will have to increase for the purpose of strengthening the flexibility and impact strength, resulting in the increase of plasticization time and decrease of equilibrium torque. The above-mentioned matters will lead to the decrease of overall performances and increase of scrap rate. Therefore, disadvantage of poor CPE is obvious.
Comparison between Quality CPE and Poor CPE CPE 135A of Jubang