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In this digital age, it may surprise you to learn that vinyl records are making a comeback. The New York Times reported that, according to the Recording Industry Association of America, 13 million vinyl LPs were sold in the United States in 2014, making it one of the record business’s few growth areas.
Not as surprising is the fact that vinyl record makers are having trouble keeping up with the demand; the presses used to make vinyl LPs were built in the 1970s and are now showing wear. To alleviate the months-long backlog of orders, a German start-up company and U.S. mold maker and parts supplier are building new presses that should be pressing discs in spring 2016, according to Plastics News. The article explains that these new presses, the first ones built in decades, are basically the same design but but incorporate modern features like an electronic control system and a hydraulic power supply to squeeze the molds.
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What is vinyl?
Vinyl is made from chlorine and ethylene, with various additives to impart flexibility, rigidity, fluidity, or thickness. Vinylinfo.org explains that the ethylene in vinyl is obtained by processing, or cracking, hydrocarbon-based raw materials (petroleum, natural gas or coal) into polymers. The chlorine half of the vinyl polymer is not derived from hydrocarbons and is readily available and inexpensive. Ethylene and chlorine combine to form ethylene dichloride, which is transformed into vinyl chloride monomer (VCM). The final polymerization step converts the monomer into vinyl polymer known as polyvinyl chloride (PVC), or simply “vinyl.” Chemical modifiers are then added to achieve the various properties desired in vinyl end-products.
How does vinyl become an LP?
Vinyl LPs start as pellets that are extruded and then placed between metal stampers. The Gizmodo article, How Records Are Made offers the following overview of the process:
Each stamper, which is attached to an autonomous 100-ton hydraulic press, works essentially like a waffle iron and can churn out thousands of records before needing replacement. A sheet of preheated vinyl roughly half the area but 3 times the thickness of a finished disc, known as the biscuit, is slipped between the jaws of the press, 300° F steam is applied to further soften the material before the jaws close, and squeeze the hot vinyl into its final shape while imprinting the audio. The disc is then cooled and hardened in a water bath and labelled—all of which is done automatically, the only human input is the loading of the two disc labels sandwiched around the biscuit.
Once it comes off the stamper, the record’s ragged edges are trimmed into a neat circle on an automated trimmer table and the record is inspected, both visually and audibly. Many, many, pressings don’t pass muster and are subsequently melted back down into biscuits for another go.
Start with the right PVC blend
PVC blends are complex mixtures of PVC particles, fillers, lubricants, stabilizers and plasticizers. Manufacturers often must modify these recipes due to technological advances, cost pressures or regulatory requirements.
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When it comes to testing the fusion behavior, compound stability, and processing behavior of PVC formulations, the laboratory mixer is an ideal measuring tool when handled in a reproducible manner. A laboratory mixer is very sensitive to any changes caused by the compound formulation, or any changes of the dry blend components. Read the application note, PVC Mixer Tests: Reproducibility and Influence of Test Conditions which describes the good reproducibility of mixer tests as well as how changes in the testing conditions will influence measuring results.
[Editor’s Note: If you’re like me and are now curious as to how that vinyl material enables you to hear music, the technology is nicely explained in this “ExplainThatStuff” article. Hint: It has to do with kinetic energy, vibrations, and making bumps on a surface. You can hear some of the original 78 rpm disc recordings on the US Library of Congress National Jukebox website.]