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Best PVC Compound Machine

What is PVC?

PVC, or Polyvinyl Chloride, stands as one of the most prevalent plastic materials in our daily lives, seamlessly integrated into numerous products and applications. PVC possesses advantages such as durability, abrasion resistance, affordability, excellent electrical insulation, impact resistance, and good chemical resistance. 

Before being processed into finished products, PVC always needs to be transformed into compounds by adding additives. PVC with less than 10% plasticizer added to the raw material is considered rigid PVC, while PVC with more than 30% plasticizer added is considered soft PVC. These distinctions arise from differences in polymerization processes and the addition of plasticizers, which impart varying degrees of flexibility to the final PVC products.

1, Rigid PVC

Rigid PVC, also known as unplasticized PVC or uPVC, is characterized by its stiff and durable nature. This type of PVC is produced through polymerization without the addition of plasticizers, resulting in a rigid polymer matrix. Rigid PVC exhibits excellent mechanical strength, chemical resistance, and dimensional stability, making it ideal for structural applications where strength and rigidity are paramount.

Applications of Rigid PVC

Pipes and Fittings
Rigid PVC pipes and fittings are extensively used in plumbing, drainage, and sewage systems due to their corrosion resistance, smooth interior surface, and long-term durability.

rigid PVC

Window Frames and Profiles
Rigid PVC window frames and profiles offer excellent thermal insulation, weather resistance, and low maintenance requirements, making them a popular choice in construction and building applications.

Signage and Display Boards
Rigid PVC sheets are commonly utilized in signage, advertising, and display applications due to their lightweight, weatherproof, and printable surfaces.

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2, Soft PVC

Soft PVC, also known as plasticized PVC or flexible PVC, undergoes polymerization with the addition of plasticizers, which impart flexibility and elasticity to the polymer matrix. Soft PVC exhibits a softer, more pliable texture compared to rigid PVC, making it suitable for applications where flexibility and malleability are desired.

Applications of Soft PVC

Wire and Cable Insulation
Soft PVC is widely used as insulation for electrical wires and cables due to its flexibility, electrical insulation properties, and resistance to abrasion and chemicals.

Soft PVC Wire and Cable

Medical Tubing and Equipment
Soft PVC medical tubing, IV bags, and medical devices benefit from their flexibility, biocompatibility, and ease of sterilization, ensuring safe and comfortable healthcare delivery.


Automotive Interiors and Upholstery
Soft PVC upholstery and interior trim components in automobiles offer comfort, durability, and resistance to wear and tear, enhancing the aesthetic appeal and functionality of vehicle interiors.

PVC has no distinct melting point. It softens at 60°C, becomes viscoelastic at 100-150°C, melts and decomposes at 140°C, with rapid decomposition at 170°C. Its softening point is close to its decomposition point, releasing HCl gas upon decomposition. PVC is a thermosensitive plastic with poor heat stability and flowability. Therefore, controlling temperature and time during PVC compounding and blending poses a challenge. Strict control of temperature and time is necessary, with screw design aimed at minimizing shear to prevent overheating.

pvc-automotive interiors

Challenges of PVC processing

Thermal Degradation

PVC is susceptible to thermal degradation when exposed to high temperatures for extended periods. During processing, such as extrusion or molding, excessive heat can lead to discoloration, degradation of mechanical properties, and the release of harmful gases. Variations in temperature can result in processing difficulties, such as poor melt flow, uneven material distribution, and surface defects.

Shear Sensitivity

PVC exhibits shear sensitivity, meaning its viscosity and flow behavior can change significantly under shear forces during processing. High shear rates, such as those encountered in extrusion or injection molding, can lead to viscosity fluctuations, melt fracture, and surface imperfections in the final product.

What is the Best PVC Compound Machine?

To ensure the excellent physical properties of profiles in the molding of multi-component thermosensitive polymer materials, it is essential to explore the “low-temperature” molding process of polymer materials. This discussion also involves exploring the crucial equipment needed to guarantee the low-temperature molding process. Here,  Cowellextrusion recommends a two stage extruder composed of two separate screws extruders and works in tandem. The first stage machine of the  two stage extruder employs a co-rotating parallel twin-screw extruder, while the second stage machine utilizes a  single-screw extruder. The advantage of this  two stage extruder lies in combining extruders with different functional characteristics into a single unit, allowing for low-temperature extrusion molding of thermosensitive polymer materials and efficient production of high-performance polymer material profiles.

Firstly, analyzing the material running process, the first stage machine utilizes a co-rotating parallel twin-screw extruder with superior mixing capacity to achieve efficient dispersion and distribution of materials. This is particularly suitable for the extrusion molding of multi-component thermosensitive polymer materials, such as the production of sheet materials for soft PVC artificial leather surfaces. The production materials include powdered resin, powdered calcium powder, powdered plasticizers, powdered additives, and powdered pigments, totaling up to 7 components.

After the material is fully compounded by the co-rotating parallel twin-screw extruder with an appropriate length-to-diameter ratio, it is directly fed into the low-shear single-screw extruder of the second stage machine without being retained by the die head. After appropriate cooling, stable pressure extrusion is achieved, avoiding the risk of material high-temperature decomposition caused by continuous high-shear action of the screw inside the extruder due to material retention at the die head of the twin-screw extruder. There is no process of cooling the material inside this design of the two stage extruder, including external heat input and internal shear heating, allowing for rapid low-temperature extrusion molding. Products produced using this method retain the toughness and elasticity of polymer materials to the greatest extent, maintaining excellent creep resistance, geometric stability, and impact resistance even at low temperatures.

Secondly, the design of this two stage extruder can fully utilize the function of the co-rotating parallel twin-screw extruder in forcing materials to undergo an “∞” displacement under the action of the twin screws, effectively performing the mixing function of the parallel twin-screw extruder. At the same time, it can fully utilize the function of the single-screw extruder in forcing materials to undergo positive displacement, focusing on material cooling and stable pressure extrusion. The separate decomposition of the two functions, combined into one integrated extruder, facilitates the optimization of the design parameters of the two parts of the extruder, not only conducive to low-temperature extrusion of products but also advantageous for optimizing the extruder’s specific output and reducing specific power consumption, achieving energy-saving, consumption-reducing, and productivity-increasing purposes.


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