by Jackie Johnson Jackie Johnson No Comments

Rising Prices of Polymers

In North America, prices for polyethylene, PVC and other solid polystyrenes have risen to unprecedent highs in 2021. This is due to a variety of factors, the most common being a distinct lack of materials used to make the plastics. Whether due to the pandemic, a mechanical failure, or simply being unable to keep up with the demand, it is clear that the scarcity of materials is causing an increase in prices.

In this week’s blog post we will go over several different polymers and why the prices have hiked in 2021.

Climb in Prices

Regional PE prices climbed an average of 9 cents per pound since April 1st of this year. Due to the pandemic and by outages caused by Winter Storm Uri in February, supplies of the material remain increasingly scarce. Some grades are harder to find than others. For example, high density PE for blow molding has been particularly hard to find, to the point where work has been delayed.

PE market analyst Mike Burns of Resin Technology Inc in Fort Worth, Texas says that allocations are moving higher than 70 percent, however demand is still vastly exceeding supply.

Force Majeure

On top of the already scarce supply of materials, North American PE supplies are further strained by a mechanical failure at a Nova Chemicals Corp. production site.

In April of this year Nova was forced to declare a force majeure, a term where an unforeseeable circumstance has prevented someone from fulfilling a contract, which covers all PE resins produced in the Sarnia, Ontario region. This includes low density PE, HDPE, and more.

A Nova spokesperson said in a letter released to the public that the firm “has experienced a mechanical failure beyond our control…. Which supplies ethylene to our polyethylene facilities…”

According to the spokesperson, there were no injuries or environmental impacts from the event, and that they did not know how long the force majeure would be in place.

PVC

With limited supplies and strong demand, PVC prices have risen by 4 cents per pound in April. Because of Winter Storm Uri, PVC makers have had a hard time finding supplies of stabilizers and other additives needed to make PVC compounds, contributing to the ever-tight supply of PVC.

This has hit the construction market has been hit particularly hard by the lack of product, with housing starts at a whopping 1.74 million rate for March, up by almost 40 percent compared to March 2020.

Prices for suspension PVC are up by 21 cents as of May 2021, up a net of 33.5 cents per pound since January of 2020.

PS

As a result of higher prices for benzene feedstock, where prices were up 38 cents for the moth to $3.01 per gallon, prices for solid PS (solid polystyrene) have surged to 9 cents per pound.

Solid PS prices for this year are up 25 cents, and 37 cents as of last year. Benzene prices are up 78 cents in the last two months alone, an increase of almost 35 percent.

The reason for this dramatic price increase? Styrene and benzene supplies have been limited. Some Gulf Coast styrene operations are only operating at 50-60 percent in recent months.

Other Materials

There are several other plastics that have seen an increase in cost of the past few months. Nylon 6 is up an average of 15 cents with Nylon 6/6 up by 25 cents. As of the first of the year, polycarbonate and ABS are both up an average of 30 cents.

On a Positive Note

Despite the increase in prices, the demand for polymers has not slowed down in the slightest. In 2020 alone, the market size was valued at USD 579.7 billion. That number has increased to USD 594 billion by 2021, with an estimated net worth of USD 750.1 billion by 2028. That is a growth rate of 3.4%!

The demand is clearly there, and it is safe to say that once the supply issues have been solved, the price of plastics will once again level out.

In Conclusion

Prices for polymers has increased over the past few months due to a variety of circumstances ranging from mechanical failure to the global pandemic. Despite this the plastics industry has remained steadfast and continues to innovate and provide quality products.

by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

All About Automolding

PTFE is an excellent material for many different applications and operating environments. Its low friction, chemical compatibility, and ability to maintain key properties at extreme temperatures has made it ideal for everything from seals in sterile food handling equipment to sleeve bearings in the harsh world of oil and gas

And there are several different options when it comes to manufacturing PTFE components, but not all methods are the same. In this blog post, we will be discussing auto molding in the context of manufacturing PTFE components.

What is Auto Molding?

Auto molding, as known as compression molding, is a popular manufacturing technique for making thermoset and thermoplastic parts–and one of the oldest plastic forming methods still in use. In short, auto molding uses compression and dies to form a near net shape polymer part. 

Where is Auto Molding Used?

There are numerous industries that depend on auto molded parts, such as aerospace, chemical processing, and the manufacture of semiconductors.

Auto molding is used to manufacture a wide range of parts, as well. These include …

  • Bearings
  • Bushings
  • Piston rings
  • Sleeves
  • Seals
  • Gaskets
  • Valves
  • Valve Seats
  • Diaphragms
  • Bellows
  • Electrical components

When compression molding of a PTFE part is done correctly, then you can depend on key aspects such as specific density, strength, elongation, and flex life as well as permeation resistance.

How Auto Molding Works

In the auto molding process, the raw materials are in the form of molding compounds. These molding compounds may be preforms (which is already shaped somewhat like the final part), granules, or putty-like masses. 

The basic design for the mold is usually generated from a 3D CAD file, and the tool and die maker will then base the mold design on that file. However, the mold designer must account for shrinkage, molding compound flow, size and positioning of channels to carry away excess material, and achieving uniform curing temperatures for the part. It is also important to ensure that the part can be removed from the mold, and there may be a need for ejector pins to achieve this. Needless to say, the mold is the most expensive aspect of auto molding.

Once the mold design is complete, it is manufactured out of steel using a CAD/CAM (Computer-Aided Design / Computer Aided Manufacturing) system and a CNC (Computer Numeric Control) milling machine. Additional features and surface finishes may require post-processing of the mold.

Once the mold is ready to go, the amount of compound needed for the part is carefully measured out and placed in the pre-heated open mold cavity. Once in place, the other side of the mold closes over the mold cavity and pressure is applied (most often by a hydraulic ram) in one direction to force the raw materials to fill up all cavities within the mold. Any excess material is carried away from the mold via overflow grooves.

Heat and pressure are both maintained until the polymer has completely cured. Once the part has cured and cooled, it is removed from the mold, and this part of the process may require the use of part ejection pins to completely free the newly cured part from the mold. After the part is removed, any flash can be easily trimmed away and precision machining can be used to ensure the part meets necessary tolerances.

Auto Molding PTFE

There are certain key aspects to auto molding PTFE compounds, including …

  • Pressure (usually between 3,000 and 4,500 psi)
  • Sintering temperature (in the range of 685°F – 720°F)
  • Dwell time (how long the part is held at the sintering temperature)

Pressure and dwell time are dependent on the volume and geometry of the part, as well as the machine being used.

Benefits of Auto Molding 

Auto molding PTFE has numerous benefits:

  • Range of geometries and shapes are possible
  • Can produce larger parts than possible with extrusion
  • Minimal waste material
  • Very cost-effective when compared to injection molding
  • Good surface finish
  • Close tolerances
  • Avoids defects associated with machining a polymer (e.g., internal stresses, warping)

In addition, auto molding can be used with both virgin and filled PTFE. Fillers can include both those that enhance structural and material properties (e.g., carbon fiber, molybdenum disulfide MoS2) and colors. Depending on the size and geometry of the part, it may be possible to compression mold multiple parts simultaneously. In such cases, a multi-cavity die would be used.

Disadvantages of Auto Molding

However, there are pros and cons to every PTFE manufacturing process. In the case of auto molded PTFE, the production speed is slower compared to injection molding (due to longer cycle times). Flash will always form and needs to be removed before the part can be considered finished, and this can also add a bit to the production time. While compression molding can be used to manufacture complex parts, there can be issues, such as underfilling in certain areas and the inability to achieve undercuts.

Auto Molding Costs

The most expensive aspect of auto molding, aside from the machinery needed, is the compression molds. Mold cost depends in part on the size of the component, but is more heavily influenced by the complexity of the die. The more complex the geometry of a part, the more expensive the die will be. However, the cost of a compression molding die is significantly less than that of an injection molding die. This is mostly due to the fact that compression molds do not require a complicated system of gates and runners that are necessary in injection molds.

Conclusion

Auto molding works well for manufacturing PTFE components that are not overly complex, have no undercuts, and involve a medium to large production run. In addition, the auto molding process is generally far more cost effective than injection molding. However, for PTFE parts to be high quality and durable, you need a company that is familiar with the process.

At Advanced EMC, we have the knowledge and experience to assist you with auto molding PTFE parts for your applications. Contact us today if you have any questions or are interested in obtaining a quote.