PT Blog

Contraction Slows for Processors

The Gardner Business Index for plastics processing moved up by eight points in May, registering 41.5 after setting an all-time low in April. For the first time since the government curtailed normal business operations to prevent the spread of COVID-19, all components of the Index moved towards more “normal” levels. Excluding supplier deliveries, all components moved higher from their prior-month readings, although each remained below 50. This situation signals that the industry is experiencing a slowing contraction, meaning that while conditions deteriorated further in the latest month, they did so at a slower rate than in the prior month.

The supplier delivery reading fell slightly in May, which may indicate a turning point in the unprecedented disruption that affected upstream production and slowed deliveries earlier in the year. (Quickening supplier deliveries lower this Index component’s reading.) The plastics processing market was exceptional in May in that survey participants reported both falling material prices and weaker pricing power for their own products.

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All plastics processing starts with moving resin to the machine, and while it can be easy to overlook the first step in any multi-step activity, processors would be remiss to downplay the vital role conveying plays in establishing a robust operation. From the silo or the gaylord to the mold or the die, there are three key areas processors need to think about when they start moving material. The design and operation of your conveying system, the choice of elbows for that system, and accounting for fines and streamers will get your conveying on the right track.
 

Selecting the right pneumatic conveying system is important for economic and reliable operation of your processing plant. Poorly designed conveying systems cause plantwide inefficiencies like high scrap rate, high maintenance costs, and housekeeping problems, to name a few.

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At last October’s K 2019 show in Germany, an engineer from a large U.S.-based thermoformer asked why injection molding technology seemed to be so far ahead of thermoforming. While it is true that injection molded parts are produced at very high tolerances and thermoformed parts typically have some deviation, recent developments suggest thermoforming is not so far behind its injection cousins where technology advances are concerned. High speeds, automation, smarter process control, integrated vision systems, and better decoration techniques are becoming more common among practitioners of the “black art” of thermoforming. In fact, it might be time to retire that label.

This article highlights five areas of thin-gauge thermoforming where advances in technology are occurring at a fast pace, looking at the interplay of plastic materials, metal tooling, and production equipment. It is not meant to be comprehensive, and adoption is not uniform around the world. Like any specialized topic, the deeper you dig, the more details you find. There is a wide variety of applications in thermoforming that covers both heavy-gauge and thin-gauge processes.
 

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Extrusion: The Importance of Zone 1 Barrel Temperature

Perhaps the most misunderstood part of the extrusion process is the effectiveness of the barrel temperature in Zone 1. In the feed section of the extruder, the solids are always well below the melt temperature (unless melt fed) and the screw conveys them forward in auger-like fashion. They become compacted from the drag and frictional forces acting upon the particles. During compression, some pressure develops in the solid polymer as it is forced into intimate contact with the barrel wall.

With the screw rotation and resulting sliding/shearing of the compacted mass against the barrel wall, as well as some conducted heat from the barrel, the solids adjacent to the barrel wall accumulate enough energy to form a thin layer of melted polymer on that surface. This usually occurs from one to three diameters after the cooled feedthroat and is often referred to as the “delay in melting.” From that point the forwarding force or output depends on that thin film dragging the solids underneath.

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Moving Toward Third Quarter, Prices of All Volume Commodity Resins Appear to Have Bottomed Out

As we approach the third quarter, prices of all nine volume commodity resins appeared to have bottomed out generally. Still, there might be some further downward pressure for resins such as PS, nylon 6 and PET, while there is upward pressure for PE and possibly PVC with the return of the Chinese export market along with higher feedstock costs.

Here’s a look at how our industry colleagues with pricing expertise view things for each of these commodity volume resins. They include purchasing consultants from Resin Technology, Inc. (RTi), Fort Worth, Texas; senior editors from Houston-based PetroChemWire; and CEO Michael Greenberg of the Plastics Exchange in Chicago.

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