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Application

Rigid PVC: processing and granulation

Excellent mechanical, electrical and optical properties

The creation of PVC from vinyl chloride (VC) was first described during the first half of the nineteenth century. Large-scale PVC production started around 1928 in the USA and 1930 in Germany. By the time the Second World War ended, it was already the most-produced plastic. With a chlorine content of 56.7% molar mass, PVC is a welcome co-product in chlorine production. Due to their low content of hydrocarbon-based components, PVC materials have a comparatively favorable energy balance and carbon dioxide footprint.

In case of fire or thermal disposal and use, substances containing hydrochloric acid or even dioxin may be released. Due to the respective consequences for the environment, the majority of the PVC industry has focused on durable products via programs such as “Vinylplus”. The consequent substitution of additives containing heavy metals was implemented rapidly and the industry evolved into a leader in material recycling. NGOs such as “The Natural Step” accompany and monitor this self-regulation, thus providing it with credibility. The total PVC market continues to grow with 2-3 % per year (CAGR).

Typical applications

Window frame with seals as an example of compounding rigid and flexible PVC
PVC-U window frame demonstrates the application options for PVC granulate following rigid PVC compounding
Injection molds in beakers as an example of rigid PVC compounding
Yellowish granulate after rigid PVC compounding with a BUSS compounding system
White tubes, manufactured from PVC-U from rigid PVC compounding using BUSS compounding technology

Thanks to its good mechanical, electrical and optical properties, as well as good chemical resistance, rigid PVC is very useful for many applications. It is used in apparatus and machine construction, pressure pipes, pipe coupling, fans, air ducting, fittings, pumps, tanks for the chemical industry and rigid PVC (PVC-U) linings.

Also, for applications in the construction sector, wastewater pipes, roof gutters, rainwater pipes, gas pipes, drainage pipes, window profiles, facade elements, ventilation shafts and anti-glare screens.

In electrical engineering, rigid PVC is used for manufacturing insulating conduits, transparent distribution box covers, housings, and cable conduits and the time-honoured vinyl records consisting of rigid PVC.

Further insights into our options for the plastics industry

Benefits

The advantages of the BUSS compounding technology for rigid PVC processing

Uniform shear rates allow controlled mixing in the compounding machine at lower temperatures while imparting only the required shear energy for the task at hand. The narrow shear rate distribution compared to alternative systems ensures uniform shear histories for every individual particle. This results in high-quality processing with reduced energy input.

The BUSS Kneader allows precise temperature control due to controlled energy input and uniform, moderate shear rates as well as their temperature monitoring by thermocouples, which are mounted in drilled kneading pins surrounded by polymer at relevant positions along the process section.

The BUSS Kneader guarantees intense distributive mixing, as the superimposition of rotation and axial movement of the mixing and kneading screw causes flow separations and a large number of shearing surfaces, thereby generating cross-channel mixing.

The BUSS compounding machine technology allows high filler loadings by splitting to 2-3 feed positions, use of feed-in processes such as side feeders, gravimetric dosing units, back venting and excellent conveying efficiency. The moderate kneader shear rates allow effortless handling of the high viscosities arising with high filler loadings.

The separate execution of compounding in the BUSS Kneader and pressure build-up in the discharge unit enables processing at low pressures and temperatures. Thus, the configuration of application-specific screw geometries in each process zone can guarantee an optimized temperature profile in each process zone.

Compounding requirements

for rigid PVC

Rigid PVC is normally processed via hot/cold mixing in the powder phase. This is followed by compounding on the BUSS Kneader for all molding processes for which granulates are required such as injection molding. If high aggregate content or specific quality requirements are called for, this two-stage process is also applied. For simpler formulations, molding from the powder premix can suffice.

The requirements of rigid PVC compounding can be described as follows: the pulverized dryblend, which in addition to the PVC resin contains further formulation components such as stabilizers, additives, filling and reinforcing materials as well as flame retardants must be dispersively and distributively intensively mixed, gelled and broken down in the compounding machine. Here, clearly defined temperature limits must be adhered to.

The BUSS Kneader excels with its uniform, moderate and if necessary, adjustable shear rates. The compounding process and the pressure build-up step are strictly separated and optimized in a two-stage system.

Low specific energies with the most intensive mixing processes, volumetric scale-up procedures and maximum availability are possible thanks to wide operating windows and reinforce the technological and market leadership gained in rigid PVC compounding technology since the beginning of mass production in the mid-20th century.

Typical plant layout

Typical plant layout for a rigid PVC compounding system

COMPEO compounder for PVC compounding

Take a look at our typical plant layout for the production of PVC compounds in our COMPEO showroom.

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BUSS Kneaders

around the globe

Our patented kneaders are in operation worldwide today and support our customers when producing plastics. Our customers can handle all the demanding requirements of PVC compounding using the BUSS compounding systems.

World map with an overview of the Co-Kneaders used for PVC compounding

Number of kneaders used for PVC compounding

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COMPEO series

We present: COMPEO, the state-of-the-art compounder that offers more versatility in its application, higher flexibility in process engineering, and increased added value in compound manufacturing.

PVC Fact Sheet

Thanks to its good mechanical, electrical and optical properties as well as its good chemical resistance, PVC can be used for many applications.

Soft PVC

During the first half of the 19th century, the creation of PVC from vinyl chloride (VC) was first described. By the time the Second World War ended, it was already the most-produced plastic. Today, industries such as medical technology rely on the unique properties of PVC-P.