Polyvinyl chloride, abbreviated as PVC, is a polymer formed by the polymerization of vinyl chloride monomer (VCM) under the action of initiators such as peroxides and azo compounds, or under the action of light and heat, according to the free radical polymerization mechanism. Polyvinyl chloride homopolymers and copolymers are collectively referred to as polyvinyl chloride resin. (PVC eco-friendly products, eco-friendly crosslinking agents, eco-friendly plasticizers)

PVC was once the world's largest-produced general-purpose plastic and has a wide range of applications. It is widely used in building materials, industrial products, daily necessities, floor coverings, floor tiles, artificial leather, pipes, wires and cables, packaging films, bottles, foam materials, sealing materials, fibers, etc. Its main uses include polyvinyl chloride profiles, polyvinyl chloride pipes, polyvinyl chloride films, PVC hard materials and sheets, general PVC soft goods, polyvinyl chloride packaging materials, polyvinyl chloride wall panels and flooring, polyvinyl chloride daily consumer goods, PVC coated products, PVC foam products, PVC transparent sheets, etc.

PVC has excellent mechanical properties, chemical properties such as acid and alkali corrosion resistance, inherent flame retardant properties, low thermal conductivity, heat insulation, sound insulation and noise reduction, formaldehyde-free products, and excellent properties such as physical and chemical modification. It has become an important material in the green home and engineering construction market, entering thousands of households and becoming known and recognized by more and more people.

I. Introduction to Polyvinyl Chloride

My name is Polyvinyl Chloride, and those in the know call me "PVC." Although I look quite similar to PE (chlorine atom replacing hydrogen), my mother isn't his mother, and his father isn't my father. I have fair skin (white powder), a relatively easy-going personality, and I easily blossom (soften) with a little sunshine (80-85℃); with warm sunshine (130℃), I become happy and excited (viscoelastic state); with intense sun (160-180℃), I become tearful and emotional (viscous flow state). Since I've always been rather frail (tensile strength around 60 MPa, impact strength 5~10 kJ/m2), I'm also afraid of "light and heat" (under light and heat, chlorine can be substituted). Therefore, from a young age, I undergo a procedure to control my condition (modification). (PVC eco-friendly products, eco-friendly crosslinking agents, eco-friendly plasticizers)

II. PVC Classification

My mother told me that before we were born, our physical characteristics could be altered by modifying our DNA. For example, those without any modifications (initiated by monomers) will only develop into "general-purpose PVC"; those with "elongated DNA chains" (addition of chain growth agents) will become "high-polymer PVC"; and there's another type that changes itself by "introducing other races' DNA" (adding crosslinking agents containing dienes and polyenes) to grow into "crosslinked PVC." Thus, we have a unique variety of types.

1. According to different application ranges, PVC can be divided into: general-purpose PVC resin, high-polymer PVC resin, and crosslinked PVC resin. General-purpose PVC: is formed by the polymerization of vinyl chloride monomers under the action of initiators; High-polymer PVC: refers to the resin formed by polymerization with the addition of chain growth agents in the vinyl chloride monomer polymerization system; Crosslinked PVC: is the resin formed by polymerization with the addition of crosslinking agents containing dienes and polyenes in the vinyl chloride monomer polymerization system.

2. Classified by the method of obtaining vinyl chloride monomers: calcium carbide method, ethylene method.

3. Classified by plasticizer content: According to the amount of plasticizer, PVC plastic is often divided into: unplasticized PVC, plasticizer content is 0; hard PVC, plasticizer content is less than 10%; semi-hard PVC, plasticizer content is 10-30%; soft PVC, plasticizer content is 30-70%; PVC paste plastic, plasticizer content is over 80%.

III. Knowing Our Family Since Birth

Speaking of our birth, it was a difficult and challenging journey. Poor families (lacking coal and natural gas) generally use the calcium carbide method, which requires collecting calcium carbide, coal, and raw salt, and causes significant environmental pollution; wealthy families (abundant coal and natural gas) mainly use the acetylene method.

1. PVC Preparation Process

There are two main preparation processes for PVC production: the calcium carbide method, with the main raw materials being calcium carbide, coal, and raw salt; and the acetylene method, with petroleum as the main raw material. In the international market, PVC production is mainly based on the acetylene method, while in China, due to resource endowments of abundant coal, scarce oil, and little gas, the calcium carbide method is mainly used.

2. Four Polymerization Methods of PVC

PVC resin is usually produced using suspension polymerization, bulk polymerization, emulsion polymerization, and solution polymerization methods. Suspension polymerization accounts for approximately 80%, bulk polymerization accounts for approximately 10%, and emulsion polymerization accounts for over 10%. (PVC eco-friendly products, eco-friendly crosslinking agents, eco-friendly plasticizers)

IV. PVC Modification Methods

Although my birth was difficult, and I've always had a "chlorine atom" and can't tolerate "light and heat." This fact is well-known, but to adapt to external survival conditions and improve my body's functions, I willingly underwent treatments such as copolymerization, grafting, chlorination, and foaming to enhance my resistance to "light and heat" (Note: Under light and heat conditions, the autocatalytic dehydrochlorination reaction initiated by the active site forms a conjugated polyene chain, and then undergoes chain breaking, crosslinking, and other reactions, causing discoloration and degradation, resulting in deterioration of the quality and performance of plastic products, thus affecting their processing and use performance).

1. Copolymerization Modification: This involves copolymerizing vinyl chloride monomers with other monomers.

2. Grafting Reaction: Introducing another monomer group or another polymer onto the PVC side chain for a grafting reaction.

3. Chlorination: Chlorinating PVC using an aqueous suspension method (or gas phase method) to increase the chlorine content from the original 57% to about 65%. The purpose of this modification is to improve the heat resistance of PVC, with a usable temperature 35-40℃ higher than that of the original PVC. This is called chlorinated polyvinyl chloride (CPVC).

4. Foaming Modification: This is mainly divided into rigid foaming and soft foaming. Foamed PVC not only reduces density and saves costs, but also has many excellent physical and mechanical properties. (PVC eco-friendly products, eco-friendly crosslinking agents, eco-friendly plasticizers)

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