chlorinated polyethylene
English name: Chlorinated Polyester Structural formula: [CH2-CHCl-CH2-CH2-CH2] n English abbreviation: CPE or CM
Chlorinated polyethylene (CPE) is a high molecular material made from high density polyethylene (HDPE) by chlorination substitution reaction. According to different structures and uses, chlorinated polyethylene can be divided into two categories: resin based chlorinated polyethylene (CPE) and elastomeric chlorinated polyethylene (CM). In addition to being used alone, thermoplastic resins can also be blended with resins such as polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), polystyrene (PS), ABS, and even polyurethane (PU). In the rubber industry, CPE can be used as a high-performance and high-quality special rubber, and can also be blended with other rubbers such as ethylene propylene rubber (EPR), butyl rubber (IIR), nitrile rubber (NBR), chlorosulfonated polyethylene (CSM), etc.
Chlorinated polyethylene (CPE) is a saturated polymer material with a white powder appearance, non-toxic and odorless. It has excellent weather resistance, ozone resistance, chemical resistance, and aging resistance, as well as good oil resistance, flame retardancy, and coloring properties. Good toughness (still flexible at -30 ℃), good compatibility with other polymer materials, high decomposition temperature, decomposition to produce HCl, which can catalyze the dechlorination reaction of CPE.
Characteristics of chlorinated polyethylene
1) CPE is a saturated rubber with excellent heat resistance, oxygen aging, ozone aging, acid and alkali resistance, and chemical properties.
2) CPE contains chlorine element, which has excellent flame retardancy and flame retardant properties. It can be combined with antimony based flame retardants, chlorinated paraffin, and Al (OH) 3 in an appropriate proportion to obtain flame retardant materials with excellent flame retardancy and low cost.
3) CPE has excellent oil resistance, with excellent resistance to ASTM1 and ASTM2 oils, comparable to NBR; The resistance to ASTM3 oil is excellent, superior to CR, and equivalent to CSM.
4) CPE is non-toxic, free from heavy metals and PAHS, and fully meets environmental requirements.
5) CPE has high filling performance and can produce products that meet various performance requirements. The processing performance of CPE is good, and there are multiple grades to choose from when the Mooney viscosity (ML1211+4) ranges from 50 to 100. The main purpose of editing this paragraph
In the late 1990s, there was an increasing demand for high-performance flame-retardant rubber in China, especially in the development of the wire and cable industry and automotive parts manufacturing industry, which drove the consumption demand for rubber based CPE. Rubber type CPE is a special synthetic rubber with excellent comprehensive performance, heat resistance to oxygen ozone aging, and good flame retardancy.
Mainly used in: wire and cable (coal mine cables, UL and VDE standards), hydraulic hose, automotive hose, tape, rubber plate, PVC profile pipe modification, magnetic materials, ABS modification, and so on.
Reinforcement filling system
CPE is a non self reinforcing rubber that requires a reinforcement system to achieve good strength. Its reinforcement filling system is similar to general rubber, with carbon black and white carbon black as the main reinforcement agents. White carbon black can improve the tear resistance of CPE, and can form a meta methyl white system to improve the adhesion between CPE and the skeleton. CPE has high filling properties, and the filling systems mainly include calcium carbonate, talc powder, clay, etc. Plasticizing system
When CPE is heated or vulcanized (non peroxide vulcanization system), hydrogen chloride will be removed. Therefore, stabilizers with acid absorption function, such as calcium stearate, barium stearate, tribasic lead sulfate or magnesium oxide, should be used in the formula.
CPE vulcanization system
CPE is a saturated rubber that cannot be effectively vulcanized by a universal sulfur vulcanization system.
The CPE vulcanization system was first used as a thiourea system, of which Na-22 is the most effective. However, Na-22 has a slow vulcanization speed, poor aging performance, high compression set, and Na-22 is a serious carcinogen, which produces an unpleasant smell during vulcanization, which has been restricted in use abroad.
Due to the fact that peroxides are cross-linked through free radical reactions, some acidic fillers can affect the generation of free radicals, so this type of filler should not be used. EataMixTCHC is a complex type of CPE specific vulcanizing agent, which is non-toxic and introduced by Shanghai Youlun Chemical to meet domestic needs.
At present, the mature application of CM vulcanization system is the peroxide vulcanization system, which has a faster vulcanization speed, good physical properties of the product, and small compression permanent deformation. Peroxides are not suitable for low pressure, mold free vulcanization. The peroxide system can be used for the production of adhesive tapes, and the products have good physical properties, heat resistance, and oil resistance. When combined with this system, the addition of crosslinking agents such as TAIC, TAC, TMPTM, HVA-2 can significantly improve its physical and mechanical properties and heat resistance.
The application cost is much lower than that of foreign thiadiazole systems, which can be applied to various vulcanization processes, including lower temperature, mold free and pressure free low-pressure vulcanization. This type of system has a fast vulcanization speed, excellent physical properties, low compression set, good heat resistance to oxygen, ozone aging, and oil resistance. It is also an effective co crosslinking system for CPE and diene rubber, and has been successfully applied in the rubber hose industry. TCHC has a slower vulcanization rate than peroxide, but can vulcanize at lower temperatures, under pressure and mold free conditions, and has excellent vulcanization properties.
TCHC can use inexpensive aromatic oil as a plasticizer, resulting in excellent vulcanization performance. The activity of MgO has little effect on the physical and aging properties of TCHC system vulcanizates. Ultrafine Mg (OH) 2 as an acid absorbent is equivalent to high activity magnesium oxide with an iodine absorption value of 150, which can replace expensive imported high activity magnesium oxide and greatly reduce manufacturing costs.
In recent years, GEO Corporation in the United States and Rheinland Chemical in Germany have launched a new type of thiadiazole vulcanization system, which, when combined with amine accelerators, has good vulcanization effects. However, the chemical composition of this system is not disclosed, and the price is high, resulting in slow promotion in China. The thiadiazole system mainly consists of crosslinking agents and accelerators. The main crosslinking agents include ECHO. A, ECHO. MB, and TDD. The main accelerators include Vanax808, EataAccelDH, and NC. It is a promising type of additive.
Properties of polyvinyl chloride (PVC)
PVC is an amorphous plastic with poor thermal stability and is prone to thermal decomposition. PVC is difficult to burn (with good flame retardancy), high viscosity, and poor flowability. There are many types of PVC, including soft, semi hard, and hard PVC, with a density of
1.1-1.3g/cm3 (heavier than water), with a large shrinkage rate (1.5-2.5%), and poor surface gloss of PVC products. (Recently, a transparent hard PVC was developed in the United States that can rival PC).
Process characteristics of polyvinyl chloride (PVC)
The residence time of PVC material in the high-temperature barrel shall not exceed 15 minutes. Compared to PVC, it is better to use high water grade adhesive and use "medium pressure, slow speed, and low temperature" conditions for molding and processing. Compared to PVC products, it is easier to stick to the front mold, and the mold opening speed (the first stage) should not be too fast. It is better to make a pull buckle type water outlet at the cold material hole of the flow channel. Before stopping the production of beer PVC materials, it is necessary to clean the barrel with PS water outlet material (or PE material) in a timely manner to prevent PVC from decomposing and generating Hd ↑, which can corrode the screw and inner wall of the barrel.
Compared to PVC, the processing temperature range is narrower (160-185 ℃), making it more difficult to process and requiring high process requirements. Generally, drying is not necessary during processing (if drying is required, it should be done at 60-70 ℃). The mold temperature is relatively low (20-40 ℃). During the processing of PVC, it is easy to produce air marks, black marks, etc. It is necessary to strictly control the processing temperature. The screw speed should be lower (below 50%), the residual amount should be less, and the back pressure should not be too high. The mold exhaust is better.
