Oil And Mining: How To Produce The Most Durable Polyurethanes?

Oil and mining industries rely on pipelines to transport highly corrosive and abrasive materials. The pipes must, therefore, be engineered to withstand the long-term effects of these materials on the inner and outer pipe surfaces. Polycarbonate polyurethanes (PC-PU) offer superior mechanical properties and high chemical and abrasion resistance, compared to other materials.

What are the benefits of PC-PU and how do you produce extremely durable polyurethanes? Let's check out...

We use pipes in the oil industry for transportation of:

• Crude oil
• Petroleum derivatives
• Petrochemicals, and
• Cement slurries

They are also used for hydro fracturing, brine and saltwater service, as riser pipes and in dredging. In mining, we use pipes for solution mining, heap leaching, dewatering, and transport of process water, slurries and tailings.

In both industries, we use slurries a lot for the transportation of solid particles. These slurries, however, are generally abrasive and corrosive and can have a devastating effect on the inner pipe surface.

Abrasive wear occurs when sharp, hard particles are forced against or scrape along pipe walls. It produces a cutting or shearing effect, resulting in piping material loss. Over time, the abrasion can cause pipe leaks and may even lead to complete pipeline failure. This leads to significant maintenance costs and causing replacement downtime. Pipes used for these slurries need to have excellent abrasion and corrosion resistance.

The materials used for pipes in the oil & mining industry

What are the traditional materials used for pipes and why are they limited?

Traditionally, we use steel pipes for such applications. But steel pipes are susceptible to abrasion and corrosion. As we improve the abrasion resistance of steel by increasing the carbon or alloy metal content, its weldability deteriorates, and formability is reduced.

Plastic pipes offer better corrosion resistance than steel pipes. Among them, we have polyethylene (PE), high-density polyethylene (HDPE) and polyvinyl chloride (PVC). Yet their use has been limited to transport of non-abrasive materials at moderate temperature and pressure.

The use of polyurethane elastomers for improved resistance

Polyurethane (PU) elastomers have shown a marked improvement in wear resistance of pipes. Fillers and additives are added to improve the abrasion resistance of polyether and polyester-based PU elastomers. Yet we still see major limitations on the use of standard PUs as pipeline elastomers for the oil and mining industries.

The polyether and polyester-based PU elastomers have limited hydrolytic stability and chemical resistance. The additives required to improve abrasion resistance are expensive, making the material uneconomical in increasingly cost-sensitive oil and mining industries. Despite the improvement in some properties, standard PU pipelines need frequent maintenance to remain in service.

How can we improve the performance of polyurethanes with polycarbonate-based polyurethane prepolymers?

Using polycarbonate-based polyurethanes (PC-PU), we see a remarkable improvement in:

• Abrasion, chemical, and aging resistance
• Enhanced mechanical properties, and
• Best in class weatherability

These polyurethanes are more durable with superior properties when compared to polyether-diol or polyester-diol based polyurethanes. We can use PC-PUs in the casting of oil & mining pipes to resist intense internal abrasion. They can also serve as an exterior coating for resistance to extreme weather and geological conditions.

What is a polycarbonate-based polyurethane prepolymer?

Polycarbonate-polyurethanes include carbonate linkages which distinguish them from polyether and polyester-based polyurethanes. To produce these high-performing PC-PUs, we can use polycarbonate-diols or polycarbonate-based polyurethane prepolymers.

A polycarbonate polyurethane prepolymer is a derivative of the corresponding polycarbonate diol in which all the polyol hydroxyl (OH) end groups have been reacted with an isocyanate leaving isocyanate groups (NCO) at the termini instead of hydroxyls.

PC-PU prepolymers are generally liquids or low-melting solids, resulting in ease of handling. Prepolymers are storage stable (in the absence of moisture) and provide a source of isocyanate functionality with lower vapor pressure as compared to free isocyanates. PC-PU prepolymers provide better compatibility with other PU formulation components due to their lower surface tension. They help produce a more uniform final polyurethane structure with improved polymer properties.

Improved mechanical properties with PC-PU prepolymers

The mechanical properties of polyurethanes based on polycarbonate prepolymers are vastly superior to those of non-polycarbonate-based polyurethanes, such as on Polytetramethyleneglycol (PTMEG) and other premium polyols.

Figure below shows that polyurethanes based on polycarbonate prepolymers have, compared to PTMEG based polyurethanes:

• 4 times the tensile strength
• 4.3 times the elastic modulus
• 1.4 times the tear strength
• About 6.5 times the resilience and elastic limit

What are the other applications of PC-PU prepolymers in the oil and mining industry?

The excellent mechanical properties of polyurethanes based on PC-PU prepolymers are better retained on exposure to harsh chemical environments when compared to other premium polyol-based polyurethanes, such as PTMEG.

Thus, polyurethanes based on PC-PU prepolymers can help produce excellent vibration reducing materials. They can also help optimizing joint-sealants with high mechanical or thermal stress in the oil and mining industry. Figure below shows that polyurethanes based on polycarbonate prepolymers exhibit lower variation in mechanical properties when compared to PTMEG PUs on exposure to harsh chemical environments.



When using polyurethanes based on polycarbonate prepolymers, the loss of tensile strength, change in the elastic modulus, break strength, toughness, and resilience are all reduced by almost half. This improved chemical resistance makes PC-PU best fitted for vibration reducing materials and sealants used in the oil and mining industries.

In addition, studies have shown that PUs based on polycarbonate prepolymers have about 52% lower water absorption in hydrolytic environments. We also see a 88% reduction in cast/coating loss on exposure to abrasive conditions.

Where can we find polycarbonate-based polyurethane prepolymers?

Polycarbonate-based prepolymers and polycarbonate diols are available from several suppliers in the market. Among them, UBE is considered to be one of the leaders for this technology, with production facilities worldwide.

UBE is an international company providing higher value-added chemicals. They have developed a strong focus on polycarbonate diols solutions, with ETERNACOLL® for the production of polycarbonate polyurethanes. They also offer ETERNATHANE®, a wide range of polycarbonate-based and isocyanate-terminated urethane prepolymer.

The prepolymers come with customizable polycarbonate and isocyanate composition. The ETERNATHANE® polycarbonate-based polyurethane prepolymers are ideally fitted for the needs of the oil and mining industries. In these industries, polyurethanes need enhanced durability against extreme conditions and to maintain original performance over time.

Conclusion

Polyurethanes based on polycarbonate prepolymers are ideal for the casting of oil & mining pipes. The pipes are more resistant to chemicals, corrosion and intense internal abrasion. We can also use polycarbonate prepolymers for exterior coatings. The coatings will have improved resistance to extreme weather conditions and hydrolytic environments. Using PC-PUs will significantly extend the life of pipelines in oil and mineral industry applications. Polycarbonate-based polyurethanes prepolymers will help lower maintenance costs and reduce downtime.

Select your polycarbonate-based polyurethane prepolymer and related products