What Are Resins?
Time and time again, plastics prove themselves to be one of the most useable and versatile materials ever developed. They have truly changed history as they allow for things to happen that would’ve been impossible otherwise. Many of of the most common household and industrial items used in the world today are crafted from plastics. There are countless different types of plastic, each with a unique purpose; allowing for them to be relevant in a multitude of different industries. Perhaps one of the most overlooked plastics is the resin family, which has existed for thousands of years and manifested themselves in numerous different forms. Traditionally, resins have been associated with either the natural products harvested from plants, or as the manufactured synthetic materials. Chemically speaking though, they are insoluble and complex substances. Synthetic resins are polymers, which are categorized as plastics.
The Evolution of Resins
Natural resin is usually found in tree bark, herbal flowers, or shrub buds. For example, a damaged pine tree can often be seen with a thick, sticky, and hard material commonly called sap. This sap seeps out from the bark to repair the damaged part of the tree. As time passes, it will fossilize into amber. Scientists have found amber that’s been around for millenia and contains fossilized remains of insects and other small organisms. Amber has also been widely used as a material in art and jewelry because it can be quite beautiful and come in many different colors. Two other well-known ancient products were collected from the resin of their trees from which they get their name, the incenses of frankincense and myrrh. Natural resins have been since as early as the days of ancient Egypt, and more extensively in the 1200’s AD by the Mongols. The Mongols invented the world’s first composite (made of multiple components) bow, which were bound together with natural pine resin. Many historians suggest that these were the most formidable weapons in the world until firearms emerged a couple centuries later. It was also a long-time material for ship-builders, as it was an excellent sealant and waterproofing agent on wooden vessels. Turpentine, varnish, and lacquer are even more noteworthy products originally derived from natural resin. Some of these remain in use even in the current day.
The late 19th century was an era of global industrial modernization, in which the time-honored traditions of the past were replaced by their new-and-improved modern descendants. This was widespread and affected nearly every major industry, and resins weren’t immune to the progressive spirit. Starting in the 1870’s and continuing into the 1930’s, scientists were developing the very first synthetically-manufactured resins. The innovation of polymerization created a seismic shift towards plastics. Resins were some of the original synthetic polymers. Plastics became an increasingly crucial commodity. Technology improved greatly, and millions around the world recognized that plastic would inevitably only become more and more important in the future ahead.
Primary Types of Resins
There are two primary types of synthetic resins- thermoset resins, and thermoplastic resins.
Thermosetting resins are formed during processing to create permanent crosslinked structures that cannot be remelted after they’re formed. This technique is often referred to as curing. In most cases, waste from the manufacturing of thermosets is either discarded or used as a filler in low-cost products. The valuable inorganic components can occasionally be extracted and recycled for future use. Thermosets usually come in either a liquid form or partially polymerized molding powder. They can then be produced into their final shape and fully polymerized. In general, the fundamental properties and characteristics of thermosets include that they cannot be melted and typically do not swell when exposed to solvents (they are insoluble and they are highly resistant to deformation). Some of the most common applications of thermoset resins/polymers include polyester, epoxy, phenolic, vinyl ester, polyurethane, polyamides, anaerobic adhesives, and silicone.
The other category of resins are the thermoplastics. These are more like metals in the sense that heated, softened, melted, and reformed over time. The process of softening and melting thermoplastics can be accomplished repeatedly without negatively affecting the composition of the substance. Unlike thermosets, there is no chemical bonding formed during the curing process. The most significant advantages and attributes of thermoplastics would include their recyclability, aesthetics, resistance to impact and chemicals, surface options, and the general eco-friendly method of manufacture. However, they are normally more expensive than thermosets and can inadvertently melt if exposed to heat. Typical thermoplastic resins are items such as: polycarbonate, polyethylene, acrylic, nylon, and teflon.
Resins may very well be taken for granted in modern society. However, a world without resins would be a far cry from the world as we know it now.