Long before biopharmaceuticals existed, humanity used resins for numerous applications. From building materials to jewelry, the use of resins has evolved over time to meet society’s ever-changing needs and demands.
Let’s explore the chemistry of resins, their history, and the various applications they serve. We’ll then explore why industrialists prefer synthetic resins over their natural counterparts and the potential for future developments in resin technology.
What Are Resins?
Resins are highly viscous or solid organic polymers. Depending on their purpose, they can be either naturally occurring or chemically synthesized. Their primary characteristic is the ability to turn from viscous to hard solids with temperature changes, making them unique and highly versatile materials.
Another way to describe resins is as the oxidative products of essential oils. They are partially or fully insoluble in water but can dissolve in organic solvents, making them useful for various applications.
Again, resins exist in natural or synthetic forms. Natural resins have to be extracted from particular trees like pine or fir. Did you know that resins are actually an evolutionary survival mechanism for trees?
Woody plants produce resin to protect themselves from predators and bacterial infections. Typically, trees only produce resins when they’re damaged. The resin oozes out of the wound, creating a protective layer around it.
Naturally, the outer environment is warmer, so the resin hardens quickly, allowing it to seal and protect the wound. That way, the resin keeps the tree from getting infected or eaten by insects.
The Chemistry of Resins
Tree species like pine, fir, and cedar have a particular substance called terpene. These organic compound mixtures are responsible for the piney scent of conifer trees. It goes without saying that every resin from different wood species oozes a unique aroma.
Terpenes give resin its characteristic scent. However, terpenes have a more critical role in tree ecology; they act as insect repellents and also help heal wounds.
Insects use a variety of chemicals, including terpenes, in their pheromones to communicate with each other. The effect of terpene levels on insect populations is complex. Some terpenes repel insects, while others might even attract specific species. However, many insects have adapted to utilize terpenes for their own benefit.
When a tree is injured, it often increases its production of terpenes. These terpenes are designed to act as a defense mechanism, deterring insect herbivores and pathogens from further damage.
Terpenes are also useful for humans, especially in essential oils and fragrances. These compounds also have therapeutic properties such as anti-inflammatory, antiseptic, and antibacterial effects.
Types of Natural Resins
1. Hard Resins
Copals, sandarac, and dammars are some of the hardest resins. They are insoluble in water and have a higher melting point, making them ideal for use as varnishes and adhesives.
Moreover, mastic and sandarac were used in ancient times for mummification. Today, they help make varnishes, paints, and adhesives.
2. Gum Resins
These resins are hybrids of pure gum and soft resins. They contain both water-soluble gum and insoluble resin. The most popular gum resin is myrrh, which comes from a tree native to eastern Mediterranean countries.
Woody plants in dry areas are more likely to produce gum resins like myrrh and frankincense. Guggul and salai are also examples of gum resins. These resins help make incense, perfumes, and traditional medicines.
3. Oleoresins
Oleoresins are mixtures of resin and essential oils. These resins come from trees with high oil content, such as frankincense, mastic, and turpentine.
You have to evaporate the oils to get a pure resin. Processors extract oleoresins mostly from common spices. For example, cinnamon and ginger oleoresins present healing properties that traditional medicine leverages.
Moreover, marjoram, nutmeg, and parsley produce water-soluble oleoresins, making them ideal for perfumes.
What Are Resins Used For?
The use of resins dates back to ancient times when humans used tree sap and plant extracts for medicinal purposes. For example, the ancient Egyptians used pine resin as a disinfectant, while the Greeks and Romans used resin for embalming.
Different uses of resins became popular and global as civilizations developed and expanded trade routes. The ancient Greeks and Romans used resins as varnishes, adhesives, and ingredients in incense and perfumes.
Resins were highly valued during the Middle Ages for their medicinal properties. They also served practical purposes, such as waterproofing ships and buildings.
The 19th century saw a surge in demand for resins due to the industrial revolution. With advancements in technology, resins are now used in various industries, including:
- Construction.
- Textiles.
- Pharmaceuticals.
- Cosmetics.
- Food and beverage.
Modern Uses of Resins
Today, resins continue to be an essential component in many industries. However, sustainability concerns were the first reason industrialists considered avoiding plant-based resins.
Harvesting resins from woody trees involves making incisions in their trunks, harvesting their roots, or bruising their leaves. This extraction process damages, even killing the trees, causing deforestation and decreased biodiversity.
Resins in Chemistry
Resins have numerous applications in chemistry, particularly in polymer science. They serve as binders and coatings for paints and varnishes, adhesives, and composites for construction materials.
Moreover, resins play a vital role in producing plastics like polyethylene terephthalate (PET), commonly used for beverage bottles, and epoxy resins, widely utilized in coatings and adhesives.
Resins in Medicine
Resins also have a long history of use in medicine. They possess anti-inflammatory and antimicrobial properties, making them useful in traditional remedies for various ailments.
In modern medicine, resins are still used as ingredients in ointments, creams, and other pharmaceutical products. They are also used in drug delivery systems, such as transdermal patches and sustained-release tablets.
Synthetically Produced Resins
In recent years, synthetic resins have gained popularity due to their consistent quality and lower cost than natural resins. Synthetic resins mimic natural resin properties but are produced in a laboratory setting using various chemicals and processes.
These resins have expanded the applications of resin-based products, such as modern plastics, adhesives, and coatings. The two main categories of synthetic resins are:
1. Thermoplastic Resins
These industrial materials soften and become viscous when heated intensely, allowing them to be molded into various shapes and forms. You can also melt and reshape them multiple times without altering their properties.
Common examples of thermoplastic resins include polyethylene, polystyrene, and polyvinyl chloride.
2. Thermosetting Resins
Thermosetting resins require chemical reactions with other compounds to harden permanently. Once cured, you can’t melt or reshape them. They are ideal for applications where high strength, durability, and chemical resistance are necessary.
For example, modern construction and furniture heavily depend on epoxy, vinyl ester, and silicone resins. While epoxy resins dominate the adhesive market, vinyl ester resins are super resistant to environmental factors and can easily withstand high temperatures.
Embrace Resins in Chemistry
Resins remain integral to many industries, such as pharmaceuticals, construction, and manufacturing. Chemists continue to drive innovation by creating new resin forms and properties that improve product performance.The future holds even more possibilities for resins as we discover more efficient ways to synthesize them and find new applications for their unique properties. For example, the resins at Advanced ChemTech are constantly being developed and improved to meet the evolving needs of various industries.