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What Is PVC Plastic?
Poly(vinyl) chloride —-PVC is a common thermoplastic with excellent strength and higher chemical resistance properties against diluted alkalis, diluted acids, and aliphatic hydrocarbons. Manufacturers across industries use this plastic for several applications since it exhibits high durability and UV resistance. This engineering plastic is produced with vinyl chloride monomers (VCM) and exists in two forms- flexible (plasticized) and rigid (plasticized).
Polyvinyl chloride can become molten by heating and solidifies by cooling. One chlorine atom, two carbon atoms, and three hydrogen atoms structured in a vinyl structure constitute the PVC’s molecular structure. Un-plasticized PVC has two types – Type I and Type II. The former is the most commonly used type and exhibits high corrosion resistance. Meanwhile, type II has higher impact strength with slightly reduced corrosion resistance.
| Property | Type I PVC | Type II PVC |
|---|---|---|
| Chemical Resistance | Excellent resistance to acids, bases, and salts | Good resistance; slightly less than Type I |
| Impact Resistance | Standard impact resistance | Enhanced impact resistance |
| Tensile Strength | High | Slightly lower than Type I |
| Flexural Strength | Good | Slightly reduced compared to Type I |
| Operating Temperature | Up to 140°F (60°C) | Up to 140°F (60°C) |
| Applications | Piping systems, chemical processing equipment, industrial uses | Outdoor fixtures, construction materials where durability is more important than chemical resistance |
| Softening/Brittleness | Becomes soft or may deform at temperatures higher than 140°F (60°C) | Retains toughness at low temperatures, less brittle at low temperatures |
| Specific Gravity | Typically around 1.40 | Typically around 1.35 |
| Processing Techniques | Similar for both types | Similar for both types |
| Regulatory Compliance | Meets various standards for chemical resistance | Meets standards for impact resistance |
CNC machining PVC involves using computer-controlled digital technology to cut raw PVC material into desired shapes. The CNC machine uses different cutting tools depending on your design requirements. Besides, PVC is highly machinable, which facilitates close tolerances without complications. It is one of the available greenest plastics because fewer nonrenewable raw materials are used in its production.
Properties of PVC Plastic
PVC material exhibits excellent mechanical properties, making it a widely used machining material for different purposes. Below are some of them:
- Low moisture absorption
- High chemical resistance
- Flame retardant and self-extinguishing
- Remarkable insulating properties
- Higher impact strength and machinability
- Good dimensional strength and water resistance
- Low weight and high hardness
- Resistance to tear and wear
- Excellent resistance to inorganic chemicals
Common PVC Plastics Used in CNC Machining
PVC plastics are of different types, each with different compounding ingredients. Below are the typical PVC plastics :
| Property | PVC (Plasticized) | UPVC (Unplasticized) | PVC-C (Chlorinated) | PVC-M (Modified) | PVC-O (Oriented) |
|---|---|---|---|---|---|
| Flexibility | Flexible due to plasticizers | Rigid, no added plasticizers | Similar rigidity to UPVC | High impact strength, tougher than UPVC | Extremely strong with high impact resistance |
| Chemical Resistance | Good | Excellent | Better than UPVC, higher chlorine content | Good, better than standard UPVC | Good chemical resistance |
| Temperature Resistance | Lower than UPVC | Up to about 60°C | Up to about 80-95°C | Improved compared to UPVC | High-temperature performance |
| Applications | Flexible hoses, cable insulation, inflatable products | Window frames, doors, piping | Hot water transportation, chemical processing | High impact areas, underground pipes | Pressure pipes, water mains, sewers |
| Durability and Strength | Less durable than UPVC | Very durable and strong | Increased due to higher resistance | Enhanced toughness | Exceptional durability, enhanced strength |
| Susceptibility to Deformation | Susceptible under heat and pressure | Resistant to deformation | Less susceptible to thermal deformation | Less deformation under impact | High resistance to deformation |
PVC (Plasticized)
Plasticized PVC is a more flexible and less rigid type of PVC-containing plasticizer. This PVC plastic type exhibits incredibly high impact strength regardless of whether it belongs to the flexible PVC category. Hence, it is easy to work with in plastic injection molding, extrusion, and other plastic production.
However, this PVC type exhibits reduced resistance to temperature and chemicals. Similarly, Plasticized PVC has a low tensile strength compared to UPVC.
UPVC (Unplasticized)
This type of PVC plastic exhibits tensile stress up to 52MPa at a temperature of 20°C. However, it has a variety of applications at temperatures of about 60°C. Nonetheless, it is crucial that different factors, such as environmental conditions and stress, determine the actual temperature limit of UPVC.
PVC-C
PVC-C, or chlorinated PVC, has properties similar to unplasticized PVC. However, this type of PVC exhibits a higher temperature resistance due to its high quantity of chlorine. PVC-C can function at temperatures up to 95°C. Like Unplasticized PVC, PVC-C exhibits ultimate stress at 20°C and ultimate tensile stress of 15 MPa at 80°C.
PVC-M
PVC-M or modified PVC belongs in the rigid material category. Although it exhibits reduced elastic modulus, ultimate tensile strength, and yield stress than unplasticized PVC, it offers high impact resistance. Besides, the amount and type of modifier used in PVC-M production plays a vital role in its properties.
PVC-O
PVC-O or PVC-oriented offers twice the ultimate tensile strength of un-plasticized PVC. It is suitable for a process that yields circumferential orientation or hoop direction of PVC molecules. Long-chain PVC molecules are also often used in this process.
PVC-O provides a tensile strength of 90 MPa and 4000 MPa elastic modulus when oriented in the hoop direction. This makes it applicable in a broad range of industries, such as the production of pressure pipes, high-strength garbage bags, films, carbonated beverage bottles, etc.
Expert Tips for Effective PVC CNC Machining
Regardless of PVC’s versatility, certain factors must be considered to machine PVC plastic parts successfully. Here are some of them:
Setup Considerations
Your workspace setup contributes to the success of your PVC machining tasks. When machining PVC material, variables such as machining speed, friction, bite angle, pressure, and tooth counts should be considered. However, it is best to machine PVC parts with lower speeds and force to avoid distortion.
Use the Appropriate Cutting Tool
Using the right CNC tool when machining PVC material impacts the machined part’s quality, ensuring close tolerances. Since PVC exhibits stronger corrosive tendencies, it is crucial to machine it with a corrosion-resistant cutting tool like stainless steel. This would ensure the safety and improve the precision of the cutting process.
Drilling and Milling
Machining experts recommend using little downward pressure and slow to medium speed for CNC PVC drilling. In addition, use bits or spade bits for drilling PVC plastic when making holes of about ¼ -inch or larger. Conversely, it would be best to use a high shear or high positive geometry cutter for face milling tasks when CNC milling PVC plastic.
Prevent Contamination
Generally, contamination is a critical concern when CNC machining PVC plastic components. Most notably in machined PVC parts for the aerospace and medical sectors. As a result, the immediate removal of chips from the machined parts and the appropriate use of coolant help to avoid contamination.
Conclusion
PVC plastic is one of the most widely used thermoplastics in CNC machining tasks. Its durability, versatility, and better cost-to-performance ratio make it a well-suited material for many applications. However, it is crucial to understand the PVC material and types for effective PVC material selection and machining.
AT-Machining is a top plastic CNC machining services expert. Our CNC-machined PVC plastic components are high-quality and work best as intended. We leverage our cutting-edge CNC machinery to meet any complex design requirements from any client. Trust us to deliver your PVC machined parts as soon as needed because we offer faster lead times. Contact us now to get a quote for your PVC machining project!
