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Custom PVC Injection Molding Factory
PVC injection molding manufacturing and design guide
Resources for The Complete Guide to PVC Injection Molding
What is PVC?
PVC was first made in the 1800s, but it didn’t really take off until the 1920s when they figured out how to make it more flexible.
PVC stands for Polyvinyl Chloride. It’s a type of plastic. It’s made from vinyl chloride, which comes from petroleum.
PVC is a synthetic plastic polymer. Here’s what you need to know about it:
PVC is the third most widely used plastic after polyethylene and polypropylene. They make about 40 million tons of PVC every year.
PVC comes in two types: rigid and flexible. They use rigid PVC for things like pipes, doors, and windows. They use flexible PVC for things like plumbing, electrical cables, flooring, and inflatable stuff.
PVC is a white, brittle solid. You can get it in powder or granule form. It’s resistant to chemicals, weather, and corrosion. That makes it a strong and versatile material.
You can make PVC more flexible by adding plasticizers. It has good electrical insulation properties. It puts itself out if it catches on fire. It’s also pretty cheap to make.
PVC is used in a lot of industries. You can find it in construction, healthcare, cars, packaging, and more. They use it to make pipes, window frames, electrical cables, medical devices, clothes, and all sorts of other stuff.
What types of PVC materials are there?
They are many types of PVC(Polyvinyl chloride), the main types are:
1. Rigid PVC (UPVC or unplasticized PVC)
It has high mechanical strength, weather resistance, and fire resistance. It is used for pipes, window frames, building materials. PVC-U (unplasticised) is hard and rigid with an ultimate tensile stress of about 52 MPa at 20°C and is resistant to most chemicals. PVC-U can generally be used at temperatures up to 60°C, although the actual temperature limit depends on stress and environmental conditions.
2. Flexible PVC (Soft PVC):
Another type is flexible PVC (plasticized PVC), which has 30-70% plasticizers. It is flexible, elastic, and can be molded into complex shapes. It is used for electrical cable insulation, flooring, medical tubing, automotive interiors. The variability from compound to compound in plasticised PVC is greater than that in PVC-U. Vinidex doesn’t make pressure pipes using plasticised PVC.
3. Chlorinated PVC (CPVC):
Another type is CPVC (chlorinated PVC), which is PVC that has been further chlorinated to increase the chlorine content to 65-72%. It has better heat resistance, aging resistance, corrosion resistance, and chemical stability. It is often used for plumbing and piping. PVC-C (chlorinated) is similar to PVC-U in most of its properties, but it has a higher temperature resistance and can function up to 95°C.
4. PVC-M (Modified PVC):
Another type is impact modified PVC, which incorporates modifiers like acrylic and rubber to improve impact resistance. It has lower tensile strength and yield stress compared to rigid PVC.
5. PVC-O (Biaxially Oriented PVC):
Another type is oriented PVC (PVC-O), which is PVC that has been stretched to align the molecular chains, enhancing strength and pressure resistance. The versatility of PVC allows it to be tailored for a wide range of applications across industries like construction, plumbing, electrical, automotive, and more by adjusting the formulation and additives.
What are the characteristics of Polyvinyl Chloride (PVC)?
PVC, or polyvinyl chloride, is a super useful and popular plastic that’s known for being tough, resistant to chemicals, and cheap. Here are some things to know about PVC:
Electrical Properties
Insulation: PVC is a good insulator because it has good dielectric strength.
Durability
Weather Resistance: PVC is resistant to weathering, chemical rotting, corrosion, shock, and abrasion, making it suitable for long-life and outdoor applications.
Corrosion Resistance: PVC is resistant to corrosion, so it lasts a long time in all kinds of environments.
Flame Retardancy
PVC is self-extinguishing, which means it stops burning when the source of the fire is removed. This is because PVC has a lot of chlorine in it, which helps prevent fires.
Mechanical Properties
Abrasion Resistance: PVC is tough, lightweight, and resistant to abrasion, so it’s good for lots of different things.
Strength: Rigid PVC has a yield strength of 4,500 to 8,700 psi (31-60 MPa), and flexible PVC has a yield strength of 1,450 to 3,600 psi (10.0-24.8 MPa).
Chemical Resistance
Resistance to Inorganic Chemicals: PVC is resistant to all inorganic chemicals, like weak acids, weak bases, and aliphatic hydrocarbons.
Resistance to Organic Chemicals: Some types of PVC can be damaged by ketones and esters, chlorinated and aromatic hydrocarbons, aromatic ethers and amines, and nitro compounds.
Cost/Performance Ratio
Cost-Effective: PVC is a good deal because it lasts a long time and doesn’t need much upkeep.
Additives
Plasticizers: Plasticizers make PVC better by making it easier to work with and by making it tougher and stronger when it’s done.
Heat Stabilizers: Heat stabilizers keep PVC from breaking down when it’s being made or when it’s out in the sun.
What are the properties of PVC?
PVC is a thermoplastic polymer. Its properties are typically categorized as rigid PVC and soft PVC.
| Property | Unit of measurement | Rigid PVC | Soft PVC |
|---|---|---|---|
| Density | g/cm3 | 1.3–1.45 | 1.1–1.35 |
| Thermal conductivity | W/(m·K) | 0.14–0.28 | 0.14–0.17 |
| Yield strength | psi | 4,500–8,700 | 1,450–3,600 |
| MPa | 31–60 | 10.0–24.8 | |
| Flexural strength | psi | 10,500 | — |
| MPa | 72 | — | |
| Compression strength | psi | 9,500 | — |
| MPa | 66 | — |
What are the advantages of Injection Molding PVC?
Injection molding PVC (Polyvinyl Chloride) offers several advantages, including:
① Cost-Effective: PVC injection molding is a cost-effective method for producing large quantities of PVC products, like pipes, fittings, and other plastic components.
② High-Quality Products: PVC injection molding makes high-quality products with precise dimensions, smooth surfaces, and consistent wall thickness.
③ Consistent Quality: The injection molding process ensures consistent quality products. Molten PVC is injected into the mold under high pressure, which results in a uniform product.
④ Fast Production: PVC injection molding is a fast production process. It allows for high-volume production and quick turnaround times.
⑤ Low Labor Costs: The automation of the injection molding process reduces labor costs, which is good for manufacturers.
⑥ Wide Range of Applications: PVC injection molding can be used to make a wide range of products, like pipes, fittings, tubing, and other plastic components.
⑦ Resistance to Corrosion: PVC is resistant to corrosion, which makes it a good material for applications where there is exposure to chemicals, acids, or other corrosive substances.
⑧ Fire-Resistant: PVC doesn’t catch fire easily and doesn’t produce much smoke, so it’s a good choice for applications where fire safety is important.
⑨ Easy Installation: PVC products are easy to install. You can connect them using solvent cement or heat fusion, which is why they’re popular for plumbing and piping.
⑩ Recyclable: PVC can be recycled, so it’s a good option for manufacturers and consumers who care about the environment.
⑪ Wide Temperature Range: PVC can handle a wide range of temperatures, so it’s a good choice for applications where there are extreme temperatures.
⑫ Chemical Resistance: PVC is resistant to a lot of chemicals, like acids, bases, and solvents, so it’s a good material for applications where there is exposure to chemicals.
What are the disadvantages of Injection Molding PVC?
While injection molding PVC offers numerous advantages, it also comes with certain disadvantages, including:
① Higher Up-Front Costs: PVC material is highly corrosive, and the mold is easy to rust during injection molding. Injection molds need to be made of stainless steel materials such as 4Cr13 or S136, and the mold cost is higher than other plastic materials.
② Environmental and Health Concerns: When you burn PVC, it releases dioxins and chlorine. These are bad for the environment and for you. Also, PVC stuff doesn’t break down easily, which adds to the plastic waste problem.
③ Toxicity: PVC gives off toxic fumes when it burns or melts, and these fumes are bad for your health.
④ Limited Heat Resistance: PVC doesn’t handle heat as well as other plastics. When you’re injection molding with PVC, it can break down and let out bad gases.
⑤ Limited Flexibility: PVC is a stiff material, so it’s hard to make complicated shapes or things that need to bend.
⑥ UV Degradation: UV Degradation: PVC can break down if it’s in the sun a lot. That can make it look bad and not work as well after a while.
⑦ Softening: PVC can get soft if it gets too hot. That can make it change shape and not work as well.
⑧ Difficult to Bond: PVC is hard to stick to other stuff. That can make it tough to make things that have a lot of parts.
⑨ Limited Recyclability: You can recycle PVC, but it’s hard because it has a lot of different stuff in it.
⑩ Limited Color Options: PVC is hard to color, so you don’t have as many choices when you’re injection molding.
⑪ Moisture Absorption: PVC can soak up water, and that can make it change shape and not work as well after a while.
Resources for The Complete Guide PVC Injection Molding Manufacturing
Can PVC be Injection Molded?
Sure, PVC can be injection mold. PVC injection molding is a well-liked manufacturing process this used to make many plastic products and parts.
PVC is a versatile material that can be molded into various items ranging from soft toys that require flexibility to rigid structures, like pipes. It is cost-effective, easily recyclable, dense, and has a high strength.
In order for PVC injection molding to be a success, you’ll need to carefully consider a few things, like the moisture content, temperature control, injection pressure and speed, and mold design.
How to Perform PVC Injection Molding: A Step-by-Step Guide
PVC injection molding is a complex process that transforms raw PVC material into durable plastic parts. Whether you are a beginner, a professional, or a student in the field, understanding the step-by-step process is crucial for achieving optimal results. This guide will cover everything you need to know, from temperature settings to injection speeds, to help you master PVC injection molding.
1. Mold Design & Mold Material Selection:
a. Mold Design: The mold needs a draft angle of 0.5° to 1° so there’s enough venting in the mold cavity.
b. Vent Hole Sizes: People usually use vent hole sizes that are 0.03-0.05mm deep and 6mm wide, or a gap of 0.03-0.05mm around each ejector pin.
c. Mold Material Selection: PVC material is super corrosive, so you have to make the mold steel out of 4Cr13, 2344, S136, and other stainless steel materials based on how many products you’re making.
2. Runners and Gates:
You can use regular gates, but for small parts, you should use needle-type or submarine gates, and for thicker sections, you should use fan gates. The smallest diameter for needle-type or submarine gates should be 1mm.
3. Injection Machine Type:
a. Screw Design: You should use a general-purpose low compression screw with a 2.0-2.2 compression ratio. The screw should turn just fast enough to fill the shot before the mold opens.
b. You usually use reciprocating screw injection molding machines for PVC. These machines need plasticating screws and a clamp force of 1.5 to 2.5 tons per square inch.
4. Drying the PVC material:
PVC can soak up moisture, so you have to dry it at 75-90°C for 1.5-2.5 hours before you use it.
5. Temperature Settings:
a. Set the barrel temperature 20°C lower than the recommended stock temperature. Set the nozzle temperature 10-20°C lower than the barrel temperature. Keep the mold temperature below 20°C, but don’t let it go above 70°C.
b. The melt temperature should be between 170°C and 190°C. Adjust the nozzle temperature so the melted PVC stays in the injection cylinder..
6. Injection Pressure and Speed:
Injection Pressure and Speed: You should use 20-40% of the maximum allowable injection pressure, with a back pressure of 0.4-0.7 MPa. Injection speed should be medium, but slower for thicker parts.
7. Processing Time:
It usually takes 30-60 seconds to process PVC parts. The time depends on things like part size, dimensions, and mold temperatures.
Injection Molding PVC Specifications
Here are some common specifications for injection molding PVC (Polyvinyl Chloride):
Material Properties:
| PVC Resin | UPVC (unplasticized) or CPVC(plasticized) depending on the application |
| Density | 1.35-1.45 g/cm³ |
| Melt Flow Index (MFI) | 3-15 g/10 min (depending on the grade) |
| Vicat Softening Point | 70-120°C |
| Tensile Strength | 40-60 MPa |
| Elongation at Break | 100-300% |
| Flexural Strength | 60-100 MPa |
Injection Molding Process:
| Melt Temperature: | 180-220°C |
| Injection Pressure | 50-150 bar |
| Injection Speed | 10-50 mm/s |
| Cooling Time | 10-30 seconds |
| Ejection Force | 5-20 kN |
Tooling and Mold Design:
| Mold Material |
Stainless steel mold materials(4Cr13, 2344, S136) Choose different mold materials according to product quantity |
| Mold Temperature | 50-100°C |
| Cooling System | Water or air cooling |
| Gate Type | Sub-gate, edge gate, or corner gate |
| Ejection System | Mechanical or hydraulic ejection |
Design Guidelines for PVC Injection Molding
Here are some design guidelines for PVC injection molding. They’ll help you make sure your PVC injection molded parts meet the required specifications and standards and are made efficiently and cost-effectively.
Wall Thickness: The recommended wall thickness for PVC is 1.2-3.5mm. If the walls are too thick, you’ll get sink marks, warping, and longer cycle times. If the walls are too thin, the parts will be weak or not fill up all the way.
Ribs: Make the ribs 0.5-0.7 times the nominal wall thickness. The height of the ribs should be less than 3 times the rib thickness so you don’t get sink marks.
Draft Angles: You should have a minimum draft angle of 1-2 degrees on all vertical surfaces so the parts come out easily. If the surfaces have texture, you might need 3-5 degrees of draft.
Corners and Edges: Don’t use sharp corners. Instead, use rounded corners that are at least 0.5 times the wall thickness. That way, you won’t get stress concentrations and the material will flow better.
Bosses and Threads: You should use threaded inserts instead of molding threads right into the part. If you have integral bosses, they should have a draft angle and rounded corners.
What are the Applications of PVC Injection Molding?
PVC injection molding is a versatile process that can make all kinds of stuff, like:
Pipe Fittings: People usually use PVC injection molding to make pipe fittings, like elbows, tees, couplings, and adapters, for plumbing and piping systems.
Electrical Components: People use PVC injection molding to make electrical components, like connectors, sockets, and switches, for all kinds of industries, like automotive, aerospace, and consumer electronics.
Medical Devices: People use PVC injection molding to make medical devices, like syringes, test tubes, and medical tubing, for the healthcare industry.
Furniture: PVC injection molding is used to produce furniture components, such as chair legs, table bases, and cabinet hardware, for the furniture industry.
Toys and Games: People use PVC injection molding to make toys and games, like action figures, dolls, and board game pieces, for the toy industry.
Agricultural Equipment: People use PVC injection molding to make agricultural equipment, like irrigation systems, farm equipment, and animal husbandry equipment, for the agricultural industry.
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