PVC Compound Applications
What’s a PVC Compound?
PVC compound or Polyvinyl Chloride is presented in pellet form after being extruded. It has been previously formulated with a set of plastic additives depending on the desired properties and on the product to be manufactured. PVC by nature is a colorless and odorless material, but it needs these additives to be functional. Within these properties we can give a certain hardness or flexibility, its appearance can be altered to make it opaque or transparent, give different colors, have impact resistance and even weather resistance. For this reason, PVC plastic is the most versatile in the industry.
Here we try to use chemical additives that comply with the most stringent regulations worldwide in terms of toxicity and environmental restrictions. Moreover, we adapt our PVC compounds to our customer’s process needs and final product demands.
Below we present some of the applications you’ll find with our compounds:
Aplicaciones de compuesto de pvc
Wire & Cable Sheathing and Insulation
Our PVC compounds for Wire & cable either, for jacketing (sheathing) or insulations comply with the most stringent requirements. Some of these are vertical flammability tests, low-smoke emission (LSF), LOI and dielectric properties. Our grades are suitable for 60°C, 75°C, 90°C and 105°C from heat emitted from the cable. Several colors available and natural color if you need to include pigments.
Rigid Profiles
Profiles for interior design/outdoors either opaque or transparent applications such as plastic wood with excellent impact resistance and UV protection when needed. Also employed for window profiles, fences, label holder, rigid film and others. Flame retardant or low-smoke grades available.
Flexible Profiles
Flexible profiles with different Shore A hardness according to your needs. Both in color, black, white, opaque or transparent. Our grades are non-toxic materials (Reach/Rohs). Some applications are garden hose, industrial hose, window seals and so on. Chemical attack and low-temp resistance under request.
Shrink Labels
Label that shrinks with heat. Useful as a safety seal for beverage packaging and gas tanks for instance. Available in different colors both solid and translucent.
Pipe Fittings
Perfect to produce pipes fittings for PVC pipes. It fits the regulation requirements in terms of weight and mechanical properties.
Food Film
Non-toxic food film with great stickiness and roll release. Excellent in low-temperature elongation, ideal for frozen food packaging. Translucent light-yellow color.
Injected Parts
Injected parts for different industries such automotive, medical, food, hardware and home appliances. We have electrical grades with flame resistance and LSF (Low Smoke & Fumes). Available either opaque or transparent, impact and hydrocarbon resistant. Some applications are automotive seals, medical devices, traffic signs or interior mats.
Medical Devices
Our grades are transparent or opaque, in colors, rigid or flexible, all according to our customer needs. They are appropriate for USP Class 1 or 2 applications for limited internal human exposure. Some applications are blood bags, oxygen hoses, oxygen masks, droppers, blood (IV) hoses among others. Medical devices free from phthalates, lead, mercury or other heavy metal that may pose a threat to human health.
Traffic Signs
Traffic cones and lane separators. Ideal to resist weather conditions and UV sunlight. When run-over they have structural memory. Glowing colors and transparent applications.
Footwear
Sandals, Cattle footwear, rain boots and foamed footwear are some examples. Depending on which grade we have PVC compounds in colors, opaque or transparent. Some grades are resistant from chemical extraction.
Toys
Non-toxic grades according to REACH and Prop 65 Listing regulation. Flexible and Rigid, opaque and transparent, crystal or in colors.
Bottles
For non-toxic grades according to REACH and FDA compliance. Good transparency and impact resistance. Some applications include cosmetic bottlers, water bottles, containers trays or shampoo bottles.
PVC main manufacturing processes
There are two main manufacturing processes in the plastics industry: injection and extrusion, from which several variants derive. Below we present a detailed description of these processes and the important characteristics where we should pay more attention:
INJECTION MOLDING
For the flexible PVC compound, it's a process that's relatively simpler than its counterpart in rigid PVC due to the good flow this plastic has to fill the cavities of its mold and, in turn, withstand high compression temperatures. Conversely, rigid PVC is subject to greater pressure and shrinkage forces, which can cause it to degrade easily and deform the final piece.
The process basically consists of a small extruder and a mold that operate under the following 4 phases:
The screw exerts a counter-rotating shear, where velocity and residence time are important factors in determining the correct fusion of the material. However, it is important to be aware of the effect that longer production cycles may have on productivity.
Generally speaking, flexible PVC compound tends to have a greater thermal resistance, so it supports a longer residence time inside the equipment without having thermal degradation.
As a general rule, a higher injection speed is desired, however, depending on the complexity of the product to be injected and changes in flow direction, this may not be as easy to achieve without flashing, reflow or thermal degradation of the material. . The operator must set the pressures and speeds that are convenient for the process. Rapid injection into rigid PVC can cause thermal degradation issues.
It refers to the last pressure of the injection process which is the one required to fill the remaining 1-5% of the mold. This way we avoid surface finish defects. Its usefulness depends on how complex it is to process and the end product itself.
Flexible PVC compound tends to be much easier to cool down because the mass is not subject to such high shear or pressures, therefore its internal temperature does not rise as much as with rigid PVC. Of course, it is important to guarantee a correct cooling of the mold and to have the internal cavities well polished in order to avoid deformations or surface finish defects.
It must be considered that the temperature of melted PVC is not the same as the temperature indicated by the process and that is why slight adjustments to process conditions may be required along any production day. Here external factors such as ambient temperature can considerably affect processing conditions.
Extrusion
For the general PVC compound, the extrusion process has certain complications as it is usually more challenging than injection to achieve proper fusion and a smooth finish. It's important to be aware of this, as the formulation can result in significant changes, causing process control issues if a material not designed for the desired process type is chosen.
The process essentially consists of a screw inside a barrel equipped with thermocouples and pyrometers, which, through a rotary movement, advances the material until it reaches the exit through a head, thereby giving dimension to the PVC or the plastic in question. The basic idea here is to melt the material with the help of high temperatures and friction generated by the equipment, to pass the material through a cavity and then cool it to obtain our finished product.
There are many variants to this process, such as tubular extrusion, blown extrusion, flat die extrusion, co-extrusion and so on. This is an important aspect when choosing the ideal compound because we need to consider aspects, such as lubrication, that adapts to the process. This is where the art of our work comes into play and our specialist technicians can help you.
Extrusion process involves the following heating phases:
The process basically consists of a small extruder and a mold that operate under the following 4 phases:
The hopper feeds the pellets to the extruder and it reaches feeding zone. It normally has a low screw compression ratio or inner space, which allows pellets to enter the equipment. In this area, we begin to see a heat transfer, through thermocouples, to the material to start the fusion process. The temperature is lower compared to following heating zones; however, they must be high, as the polymer, a poor heat conductor, must be pre-heated.
In this phase, second and third heating zones intervene where we see a gradual increase in the compression ratio in our screw. Shear and torque increases and the mass acquires a pseudo-plastic appearance. Here it is important to control temperatures to achieve a homogeneous fused mass in case of adding pigments.
Maximum compression is achieved and a homogeneous melt is obtained. Usually this is where the highest temperatures are achieved before the mass passes through the die.
It is also considered a conveying zone with temperatures similar to the previous zone. This is where surface gloss can be given to the finished product. This is also where we can control the flow of the material in order to control our production line. Remember that viscosity in inversely proportional to heat. Sometimes when the equipment is worn out, it is recommended to add meshes that help increase compression and thus promote the fusion of the material.
Once our material exists the extruder, a pulling process is carried to go on to a cooling, drying and cutting process. The peculiar characteristics of the following processes are a unique part of the product to be manufactured and the choice of the manufacturer.
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