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CPE is chlorinated polyethylene, which is made by chlorination of high-density polyethylene (HDPE), that is, the product of partially replacing hydrogen atoms on the HDPE molecular chain with chlorine atoms.
CPE is chlorinated polyethylene explanation: It is made by chlorination of high-density polyethylene (HDPE), that is, the product of partially replacing hydrogen atoms on the HDPE molecular chain with chlorine atoms.
It is a white powder, non-toxic.
[CH2-CHCl-CH2-CH2]n, English abbreviation: CPE or CM Chlorinated polyethylene (CPE) is a saturated polymer material.
Because CPE molecules do not contain double chains, they have good weather resistance, and at the same time have better flame resistance and thermal stability than PVC, low cost and excellent performance. It is soluble in aromatic hydrocarbons and halogenated hydrocarbons, insoluble in aliphatic hydrocarbons, decomposes above 170¡ãC, and releases hydrogen chloride gas. It has a stable chemical structure, excellent aging resistance, flame resistance, cold resistance, weather resistance, free coloring, chemical resistance, ozone resistance and electrical insulation, as well as good compatibility and processability. It can be mixed with PVC, PE, PS and rubber to improve its physical properties.
First: The type of PE used-----The CPE obtained from high molecular weight polyethylene has higher viscosity and tensile strength, but the adhesion between this CPE and PVC resin is low. The viscosity and tensile strength of CPE obtained from low molecular weight polyethylene are lower. The CPE obtained from high density polyethylene has good heat resistance.
Second: The size of the raw material particles-----If the particle size is too small, it is easy to form a gel or agglomerate CPE. When the particle size is too large, the distribution of chlorine is uneven and it is difficult to dissolve in organic solvents. The particle size range is 0.1-200 ¦Ìm.
Third: The degree of CPE chlorination - when the chlorine content is below 25%, it has poor compatibility with PVC and cannot be used as a modifier; when the chlorine content is greater than 40%, it has good compatibility with PVC and can be used as a solid plasticizer, but is not suitable for impact modifiers; CPE with a chlorine content of 36-38% has good elasticity and compatibility with PVC, and is therefore widely used as an impact modifier for PVC. The most commonly used CPE is CPE containing 35% chlorine. CPE with a chlorine content of about 35% has low crystallinity and glass transition temperature, good rubber elasticity, and suitable compatibility with PVC. It is widely used as an impact modifier for PVC hard products.
CPE is mainly produced by suspension method, which is divided into water phase method and hydrochloric acid phase method. The water phase method has a high chlorine utilization rate and a stable chlorine content in the product, but the equipment is severely corroded and the amount of three wastes is large. The hydrochloric acid phase method is the most advanced production method, with a short process, stable product quality, and low three wastes.
CPE impact modifier selection
1) Chinese CPE models are generally identified by 135A, 140B, 239C, etc., where the first digits 1 and 2 represent the residual crystallinity (TAC value), 1 represents a TAC value of 0-10%, 2 represents a TAC value>10%, the second and third digits represent the chlorine content, such as 35 represents a chlorine content of 35%, and the last digit is the letters ABC, which are used to represent the molecular weight of the raw material PE, A is the largest, and C is the smallest.
2) Influence of molecular weight: CPE type A has the largest molecular weight and high melt viscosity. Its viscosity is most compatible with PVC, and it has the best dispersion effect in PVC, and can form an ideal network-like dispersion form, so CPE type A is generally selected as a modifier for PVC.
3) TAC value: TAC value indicates the content of PE crystal and amorphous state in CPE molecule, which reflects the uniform distribution of chlorine atoms on CPE molecule to a certain extent. A large TAC value indicates that PE segment has more crystals, and the compatibility of PE segment with PVC is poor. A small TAC value indicates that PE and PVC have good compatibility. Generally, CPE with TAC value less than 5 is selected as impact agent.
When the addition amount is less than 10 parts, the impact strength of PVC increases rapidly with the addition of CPE, but further increasing the addition amount of CPE will increase the impact strength of PVC very little. Therefore, when used as impact agent, the addition amount of CPE is preferably 8-10 parts. At the same time, with the increase of CPE, the tensile strength of PVC blends continues to decrease, and the elongation at break increases. If the toughness is expressed by the product of tensile strength and elongation at break, it is obvious that the toughness of PVC will increase significantly with the increase of CPE addition.
Some literatures believe that when the amount of CPE exceeds 8 parts, it will exceed the saturated solubility in PVC and precipitate from PVC, forming a microphase separation structure with PVC as the sea and CPE as the island, thereby significantly improving the impact strength of PVC. Some literatures believe that when CPE exceeds 6 parts, it can form a network in the formula, thereby playing an impact modification role. However, when CPE is added at a low amount (such as 1 part), it can neither form a network in the formula system nor exceed its saturated solubility in PVC and precipitate, and its impact modification effect in the formula is minimal.
When the amount of CPE added is less than 5 parts, it delays plasticization. At 5 parts, it has basically no effect on the plasticization of the formula system. When CPE exceeds 5 parts, it plays a role in promoting plasticization. With the increase of CPE, the plasticization time of the formula becomes shorter and shorter, the maximum plasticization torque and equilibrium torque increase, and the plasticization temperature gradually decreases.
The chlorine content of CPE is 35%. There are two segments in its structure: one is the chlorinated segment in which hydrogen atoms are replaced by chlorine atoms. This segment has a strong structure and is similar to PVC. The two have good compatibility. The other is the PE segment in which hydrogen atoms are not replaced by chlorine atoms. This segment has a very weak structural polarity and poor compatibility with PVC. It plays an external lubricating role between PVC and can delay the plasticization of PVC.
The glass transition temperature of CPE is around 10¡æ, while that of PVC is 80¡æ. Under the test conditions, CPE shows a tendency to soften and plasticize earlier than PVC and has a slightly higher viscosity. When the amount of CPE added is small, the total amount of polar segments with good compatibility between CPE and PVC is small, and the external lubrication of the PE segments dominates, delaying the plasticization of the system. With the increase of CPE, a large number of CPE molecules soften and plasticize in advance and the higher viscosity increase the viscosity of the entire formulation system. At this time, the effect of CPE on the viscosity of the overall material overcomes the external lubrication of the PE segments in its structure, so that the entire formulation system begins to plasticize at a lower temperature, which promotes the plasticization of the material.
The feature of adding low-component CPE to delay plasticization has been applied in actual production. When promoting ACR, since the viscosity of the ACR impact modified formula system is greater than that of CPE, the plasticization time is shorter and the plasticization torque is higher, there are some problems in directly replacing CPE with ACR. Therefore, a small amount of CPE is used in the ACR impact system to delay plasticization, which to a certain extent alleviates the disadvantage of too fast plasticization of the ACR formula, which is better than completely using lubricants to adjust the plasticization behavior.
LGCE6040, Samsung N220P, Liaoyang Petrochemical L0555P, Yangzi Petrochemical YEC5505T, Beijing Additives Plant No. 2.
LGCE6040 product features: the advantage is good toughness. The disadvantages are low strength and small product volume.
Samsung N220P product features: the advantages are good toughness, coarse particles, and large product volume. The disadvantages are high viscosity, poor fluidity, and high pressure during production that is difficult to control.
Product features of L0555P produced by Liaoyang Petrochemical: Advantages are relatively balanced toughness and strength, high conversion rate, and large product volume. Disadvantages are low raw material output and difficulty in purchasing.
Product features of YEC5505T produced by Yangzi Petrochemical and Beijing raw materials: Advantages are low prices. Disadvantages are that all indicators do not meet the production requirements of CPE, difficult to process, and low conversion rate.
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