Plastics play many essential roles in products we frequently use, but where do all these helpful plastics originate from? The raw ingredients for most plastics we see daily come from byproducts of oil and natural gas. According to the experts over at Trecora, understanding how hydrocarbons convert into versatile, moldable plastic polymers provides insight into why they suit a variety of handy applications while keeping costs low.
Cracking Long Chains
The hydrocarbon molecules in fossil fuels consist of long chains of hydrogen and carbon atoms bonded together. Applying heat breaks large hydrocarbon molecules down into smaller building blocks in a process called cracking. One method pumps heated oil into a furnace to thermally crack molecules. Another technique uses a catalyst like silica or rhenium to enable the cracking at lower temperatures. Whether through heat alone or catalysts’ aid, cracking chopped up hydrocarbons creates lighter molecules ready to undergo polymerization into new materials. Distilling then separates out the various molecules by size and structure. Lighter hydrocarbons become fuels while some separated fractions are designated to make plastics and polymers.
Assembling Monomers
Industrial chemistry transforms small, cracked hydrocarbon molecules into monomers – the repeat units that link up into plastic polymer chains. A four-carbon butane molecule from gas, for example, converts into a vinyl chloride monomer for PVC plastic. Ethane molecules cracked from natural gas transform into ethylene building blocks for polyethylene. Simple hydrocarbon ingredients shape up into molecular representatives equipped to chemically assemble into full-fledged polymers. The monomers also pack pendant atoms that impart useful qualities such as strength, flexibility or heat resistance to finished plastics. Leveraging hydrocarbons allows manufacturers to summon up monomers to support low-cost, high-performing polymer production through their forthcoming chemical connections.
Polymerizing Chains
The distinct attributes of plastics arise when their tiny subunits chemically bond together into long repeating chains called polymers. Under the right conditions, molecular monomers link arms and build strands of interconnected repeating units. Think of it like snapping together lots of plastic brick pieces into flexible chains. The tiny connections between molecular building blocks lend durability, while pendant atoms lend specialized traits. Polymerizing creates giant macromolecules from little monomers as chains grow longer through more monomer attachment. Eventually, chains entangle and align into crystalline arrangements of polymer plastic. Different monomers and reaction conditions yield polymers with unique strength, chemical and heat resistance suited to their applications.
Processing Pellets
Raw polymer resin straight from production holds little useful form, like unset gelatin. Melt spinning, extrusion and molding transform amorphous polymer resin into handy plastic objects. Sheets, films, fibers like polyester, foam padding, containers and packaging all begin with polymer pellets. Melting the pellets enables them to flow into molds and take shape as they cool and harden, much like a baker pouring batter into shaped pans. Fast cooling after forming prevents crystallization, resulting in clear rather than opaque plastic. Cutting and post-processing finish raw molded plastic stock into functional fittings and parts ready for end products. Additives introduced during processing can color, stiffen, or protect objects during regular use.
Conclusion
The prolific plastics we routinely rely on start out as hydrocarbons cracked and distilled from petroleum and natural gas. Transformed into specialty molecular representatives, these monomers team up into repeating polymer chains with attributes like strength, flexibility and durability. Molding and processing adaptations then craft them into the many shapes and forms making modern life smooth and more enjoyable. So each time you unscrew a plastic lid, it pays to think about the tiny chemical predecessors that powered up the creation of these extremely useful materials we see and touch every day.
