As a traditional and widely used PVC toughening agent, Chlorinated Polyethylene (CPE) holds an important position in the field of PVC processing due to its unique performance characteristics.

I. Structural Features of CPE

CPE is a kind of polymer material obtained by chlorinating High - Density Polyethylene (HDPE). The chlorine content, which generally ranges from 30% to 40%, is a key factor affecting the properties of CPE.

II. Toughening Principle of CPE for PVC

A. Rubber Elasticity and Energy Absorption

CPE has rubber - like elasticity. When added to PVC, it forms a dispersed phase in the PVC matrix. When subjected to external impact, the rubber - phase region of CPE can undergo elastic deformation and absorb a large amount of energy. At the same time, the rubber - phase particles can act as stress - concentration points, triggering the formation of silver streaks and shear bands in the surrounding PVC matrix. The development and interaction of silver streaks and shear bands consume energy and prevent the rapid propagation of cracks, thus improving the toughness of PVC.

B. Compatibility and Interfacial Interaction

CPE has a certain degree of compatibility with PVC, enabling the formation of a good interfacial bond between them. This interfacial bonding force helps to effectively transfer stress between the CPE rubber phase and the PVC matrix, giving full play to the toughening effect. An appropriate interfacial interaction not only ensures the uniform dispersion of CPE in PVC but also enables the two to jointly resist external forces, enhancing the overall performance of the material.

III. Application Scenarios of CPE in PVC Products

A. Door and Window Profiles

This is one of the most widely used fields of CPE - toughened PVC. The toughening effect of CPE makes the profiles less likely to break when subjected to external impact, improving the safety and durability of doors and windows. It also maintains the stability of color and performance, and is less prone to problems such as aging and fading.

B. Pipe Fittings

In the production of PVC pipe fittings, CPE is commonly used in the production of drainage pipes, wire and cable sheaths, etc. For drainage pipes, the pipes need to have a certain degree of toughness to adapt to different installation environments and resist possible external impacts. In wire and cable sheaths, CPE not only provides a toughening effect but also enhances the flame - retardant performance of the pipes, ensuring the safe use of wire and cable.

C. Stone - Plastic Sheets

Stone - plastic sheets are often used in fields such as building decoration and advertising production. They have high requirements for hardness and rigidity, but also need to have a certain degree of toughness to prevent brittleness and cracking. After adding an appropriate amount of CPE toughening agent, the impact strength of stone - plastic sheets is significantly improved.

IV. Limitations of CPE Toughening Agent in PVC Production

A. High Cost

To achieve an ideal toughening effect, a relatively high addition amount may be required, increasing the overall raw material cost.

B. Reduction of Tensile Strength

The strength of CPE itself is inferior to that of PVC. After addition, it will dilute the strength of the PVC matrix, resulting in a decrease in tensile strength. In PVC products with high requirements for tensile strength, such as building structural components and industrial load - bearing pipes, excessive addition of CPE will make the products difficult to withstand tensile stress and prone to breakage during use.

C. Aging Problem

CPE is prone to aging. At high temperatures, the molecular chain of CPE degrades, weakening the toughening effect. Under ultraviolet irradiation, CPE undergoes a photo - oxidation reaction, causing the surface of PVC products to discolor, powder, and crack, reducing toughness and mechanical properties. For example, outdoor PVC billboards, due to sunlight exposure, the aging of CPE makes them brittle and prone to cracking.

D. Loss of Toughening Effect at Low Temperatures

The glass transition temperature  of CPE is - 25℃, and it will lose its toughening effect at low temperatures.

E. Stringent Temperature Requirements for Processing

CPE processing has strict temperature requirements. If the temperature is too high, CPE decomposes, releasing hydrogen chloride gas, which corrodes equipment and affects product performance. If the temperature is too low, the compatibility between CPE and PVC is poor, resulting in uneven dispersion and product defects such as rough surfaces and uneven internal structures.