How is castor oil made

Anyone who experiences an allergic reaction to castor oil should seek medical attention immediately. Using castor oil is a useful and inexpensive way to promote skin health, and it may have particular benefits for facial skin.

However, much of the evidence underlying these benefits is yet to be deemed conclusive, and a greater degree of scientific research will be required to determine the full benefits of castor oil. This oil is relatively safe, but it can cause some side effects that should be considered when deciding whether to use castor oil on the face and skin. Read the article in Spanish. Integrative medicine IM combines conventional medicine with complementary treatments.

Learn more about IM here. Qigong may have benefits for mental and physical health, but the scientific evidence is limited. Learn about qigong's benefits here. What is fire cider, and how do people make it? Read on to learn more about the natural remedy, including its potential health benefits and side…. Some people claim that armpit detox can benefit the immune system and even fight cancer. But what is an armpit detox, and is it necessary?

Find out…. Progressive muscle relaxation PMR is a relaxation technique that involves a person gradually tensing and relaxing muscles one by one. Benefits of castor oil for the face and skin. Medically reviewed by Debra Rose Wilson, Ph.

A root-end filling material simply refers to root-end preparations filled with experimental materials. The main objective of this type of material is to provide an apical seal preventing the movements of bacteria and the diffusion of bacterial products from the root canal system into the periapical tissues.

MTA is primarily composed of tricalcic silicate, tricalcic alluminate, and bismuth oxide and is a particular endodontic cement. Biodegradable polyesters are one of the most common applications using castor oil. That is, most fatty acids have a single carboxylic acid group. RA, however, is known to be one of the few naturally available bifunctional fatty acids with an additional hydroxy group along with the terminal carboxylic acid Fig.

The presence of this hydroxyl group provides additional functionality for the preparation of polyesters or polyester-anhydrides. The dangling chains of the RA impart hydrophobicity to the resulting polyesters, thereby influencing the mechanical and physical property of the polymers.

These chains act as plasticizers by reducing the glass transition temperatures of the polyesters. Fine-tuning these copolymers can provide materials with different properties that find use in products ranging from solid implants to in situ injectable hydrophobic gel. Castor oil has been used to produce soaps in some studies.

Total vegetable oil greases are those in which both the lubricant and gellant are formed from vegetable oil. Their study utilized a simultaneous reaction scheme to form sodium and lithium greases using castor oil. Castor oil has also been used for developing low pour point lubricant base stocks through the synthesis of acyloxy castor polyol esters. In his research, a biodegradable two-stroke 2T oil, a popular variety of lubricating oil used on two-stroke engines in scooters and motorcycles, 57 was developed from castor oil, which consisted of tolyl monoesters and performance additives, but no miscibility solvent.

Production of castor oil generates two main byproducts: husks and meal. For each ton of castor oil, 1. A study by Lima et al 62 showed that blends of castor meal and castor husks used as fertilizer promoted substantial plant growth up to the dose of 4. However, doses exceeding 4.

Their study showed that castor meal may be used as a good organic fertilizer due to its high nitrogen and phosphorus content, but blending with castor husks is not necessary. Coatings and paints are also another application of castor oil. Castor oil can be effectively dehydrated by nonconjugated oil—maleic anhydride adducts to give useful paint or furniture oil applications Fig.

The reaction is known to be relatively rapid and proceeded to high yield under mild conditions. In a separate study by Thakur and Karak, 65 advanced surface coating materials were synthesized from castor oil-based hyperbranched polyurethanes HBPUs , a highly branched macromolecule.

The HBPs exhibited excellent performance as surface coating materials with the monoglyceride-based HBPU, exhibiting higher tensile strength than direct oil-based coatings.

Ceramer coatings are also another coating application of castor oil. Beyond this infamous application of castor oil, it is considered to be an important feedstock utilized by the chemical industry, particularly in producing a wide array of materials, many of which are superior to equivalent products derived from petroleum. The high percent composition of RA in proximity to the double bond makes this oil poised for various physical, chemical, and even physiological activities, as described in the aforementioned paragraphs.

Owing to the activity of RA in the intestine, castor oil has been widely used in various bioassays involving antidiarrhea activity on laboratory animals. Castor oil is often administered orally to induce diarrhea in rats.

In modern-day medicine, castor oil is also used as a drug delivery vehicle. The product is a polyexthoxylated castor oil, a mixture CAS No. This product is often used as an excipient or additive in drugs and is also used to form stable emulsions of nonpolar materials in various aqueous systems. It is also often used as a drug delivery vehicle for very nonpolar drugs such as the anticancer drugs paclitaxel and docetaxel.

The extraction process begins with the removal of the hull from the seeds. This can be accomplished mechanically with the aid of a castor bean dehuller or manually with the hands. When economically feasible, the use of a machine to aid in the dehulling process is more preferable. After the hull is removed from the seed, the seeds are then cleaned to remove any foreign materials such as sticks, stems, leaves, sand, or dirt. Magnets used above the conveyer belts can remove iron. The seeds can then be heated to harden the interior of the seeds for extraction.

In this process, the seeds are warmed in a steam-jacketed press to remove moisture, and this hardening process will aid in extraction. The cooked seeds are then dried before the extraction process begins. A continuous screw or hydraulic press is used to crush the castor oil seeds to facilitate removal of the oil Fig. The first part of this extraction phase is called prepressing. Prepressing usually involves using a screw press called an oil expeller.

The oil expeller is a high-pressure continuous screw press to extract the oil. Cold-pressed castor oil has lower acid and iodine content and is lighter in color than solvent-extracted castor oil. Following extraction, the oil is collected and filtered and the filtered material is combined back with new, fresh seeds for repeat extraction.

In this way, the bulk filtered material keeps getting collected and runs through several extraction cycles combining with new bulk material as the process gets repeated.

This material is finally ejected from the press and is known as castor cake. A Soxhlet or commercial solvent extractor is used for extracting oil from the castor cake. Use of organic solvents such as hexane, heptane, or a petroleum ether as a solvent in the extraction process then results in removal of most of the residual oil still inaccessible in the remaining seed bulk. Following extraction of the oil through the use of a press, there still remain impurities in the extracted oil.

To aid in the removal of the remaining impurities, filtration systems are usually employed. The filtration systems are able to remove large and small size particulates, any dissolved gases, acids, and even water from the oil. Crude castor seed oil is pale yellow or straw colored but can be made colorless or near colorless following refining and bleaching.

The crude oil also has a distinct odor but can also be deodorized during the refining process. After filtration, the crude or unrefined oil is sent to a refinery for processing. During the refining process, impurities such as colloidal matter, phospholipids, excess free fatty acids FFAs , and coloring agents are removed from the oil. Removal of these impurities facilitates the oil not to deteriorate during extended storage. The refining process steps include degumming, neutralization, bleaching, and deodorization.

This process can be repeated. Following the degumming step, a strong base such as sodium hydroxide is added for neutralization. The base is then removed using hot water and separation between the aqueous layer and oil allows for removal of the water layer. Neutralization is followed by bleaching to remove color, remaining phospholipids, and any leftover oxidation products. The castor oil is then deodorized to remove any odor from the oil.

The refined castor oil typically has a long shelf life about 12 months as long as it is not subjected to excessive heat. The steps involved in crude castor oil refining are further discussed in the next section.

While the previous section briefly discussed the general overview involved in a castor oil refining step, this section thoroughly explains each of the processes involved in it.

The order of the steps performed in the refining process, which includes degumming, neutralization, bleaching, deodorization, and sometimes winterization, should be taken into consideration for efficient oil refining Fig. The first step in the castor oil refining process, called degumming, is used to reduce the phosphatides and the metal content of the crude oil. The phosphatides present in crude castor oil can be found in the form of lecithin, cephalin, and phosphatidic acids.

While hydratable phosphatides can be removed in most part by water degumming, nonhydratable phosphatides can only be removed by means of acid or enzymatic degumming procedures. Water degumming is a relatively simple, inexpensive process to remove as much gums as possible in the initial stages of oil refining. Water is then added to the crude oil and the resulting mixture is stirred well and allowed to stand for 30 minutes during which time, the phosphatides present in the crude oil become hydrated and thereby become oil-insoluble.

Water degumming allows the removal of even small amounts of nonhydratable phosphatides along with the hydratable phosphatides.

The extracted gums can be processed into lecithin for food, feed, or technical purposes. In general, the acid degumming process can be considered as the best alternative to the water degumming process if the crude oil possesses a significant amount of nonhydratable phosphatides.

The precipitated gums are then separated by centrifugation followed by vacuum drying of the degummed oil. The conversion of nonhydratable phosphatides to hydratable phosphatides can also be attained using enzymes. A high-speed rotating mixer is used for effective mixing of oil and enzyme.

The oil is then separated from the hydrated gum by mechanical separation and is subjected to vacuum drying. These enzymes have specific functions and specificities. Good quality castor seeds stored under controlled conditions produce only low FFA content of approximately 0. Hence, it is highly essential to remove the high FFA content so as to produce a high-quality castor oil. This process of removal of FFA from the degummed oil is referred to as neutralization.

In general, the refining process can be divided into two methods: chemical and physical refining. Under these processing conditions, the low boiling point FFA is vacuum distilled from the high boiling point triglycerides.

On the other hand, chemical refining is based on the solubility principle of triglycerides and soaps of fatty acids. The formed soap is generally insoluble in the oil and, hence, can be easily separated from the oil based on the difference in specific gravity between the soap and triglycerides. The specific gravity of soap is higher than that of triglycerides and therefore tends to settle at the bottom of the reactor. Most of the modern refineries use high-speed centrifuges to separate soap and oil mixture.

Alkali neutralization or chemical refining reduces the content of the following components: FFAs, oxidation products of FFAs, residual proteins, phosphatides, carbohydrates, traces of metals, and a part of the pigments.

The obtained soap has a higher specific gravity than the neutral oil and tends to settle at the bottom. The oil can be separated from the soap either by gravity separation or by using commercial centrifuges. Small-scale refiners use gravity separation route, whereas large capacity plants utilizes commercial vertical stack bowl centrifuges.

The separated oil is then washed with hot water to remove soap, alkali solution, and other impurities. Castor oil neutralization is a high loss-refining step. This loss is presumably due to the small difference in specific gravity of the generated soap and neutral viscous castor oil. Although castor oil obtained after degumming and neutralization processes yield a clear liquid by appearance, it may still contain colored bodies, natural pigments, and antioxidants tocopherols and tocotrienols , which were extracted along with the crude oil from the castor beans.

The reduction in the oil color can be measured using an analytical instrument, called a tintometer. Activated earths are clay ores that contain minerals, namely, bentonite and montmorillonite. These types of clay are generally found on every continent generated through unique geographical movements millions of years ago. Normally, unprocessed clay has lower bleachability than acid-activated or processed clays.

The unprocessed clays when activated by concentrated acid followed by washing and drying acquire more adsorptive power to adsorb color pigments from the oil. Under these processing conditions, colored bodies, soap, and phosphatides adsorb onto the activated earth and carbon. The activated earth and carbon are removed by using a commercial filter. Bleaching castor oil containing higher phosphatide and soap content often leads to high retention of oil due to the large amount of activated earth used and thus causes filtration issues.

Deodorization is simply a vacuum steam distillation process that removes the relatively volatile components that give rise to undesirable flavors, colors, and odors in fats and oils. Unlike other vegetable oils, castor oil requires limited or no deodorization, as it is a nonedible oil where slight pungent odor is not an issue for most of its applications, with the only exception being pharmaceutical grade castor oil. The majority of vegetable oils contain high concentrations of waxes, fatty acids, and lipids.

Hence, it is subjected to the process of winterization before its final use. Winterization of oil is a process, whereby waxes are crystallized and removed by a filtering process to avoid clouding of the liquid fraction at cooler temperatures. Kieselguhr is the generally used filter aid and the filter cake obtained at the end can be recycled to a feed ingredient.

Castor oil is a promising commodity that has a variety of applications in the coming years, particularly as a renewable energy source. Essential to the production and marketing of castor oil is the scientific investigation of the processing parameters needed to improve oil yield.

In the recent years, machine learning predictive modeling algorithms and calculations were performed and implemented in the prediction and optimization of any process parameters in castor oil production.

Utilization of an artificial neural network ANN coupled with genetic algorithm GA and central composite design CCD experiments were able to develop a statistical model for optimization of multiple variables predicting the best performance conditions with minimum number of experiments and high castor oil production.

Such mathematical experimental design and methodology can prove to be useful in the analysis of the effects and interactions of many experimental factors involved in castor oil production. With the advent of biotechnological innovations, genetic engineering has the potential of improving both the quality and quantity of castor oil.

Genetic engineering can be categorized into two parts: one approach is to increase certain fatty acids, while the second approach is to engineer biosynthetic pathways of industrially high-valued oils.

In one particular study by Lu et al, 95 Arabidopsis thaliana expressing castor fatty acid hydroxylase 12 FAH12 was used to mine genes that can improve the hydoxy fatty acid accumulation among developed transgenic seeds. The aforementioned study was able to identify certain proteins that can improve the hydroxy fatty acid content of castor seeds. These proteins include oleosins a small protein involved in the formation of lipid bodies and phosphatidylethanolamine a protein involved in fatty acid modification and is channeled to triacylglycerol.

With the dawn of the —omics era, genomics, transcriptomics, and proteomics can be key players in understanding the genetics of improving the quality and quantity of oil production. Advances in genomics have drafted the genome sequence of the castor bean, which has led to insights about its genetic diversity.

Further, proteomics can be used to understand proteins and enzymes that are expressed by the castor bean plant. As a source of biodiesel, recent studies showed that the biodiesel synthesis from castor oil is limited by a number of factors that include having the proper reaction temperature, oil-to-methanol molar ratio, and the quantity of catalyst. A study using response surface methodology as a model has been used to optimize the reaction factor for biodiesel synthesis from castor oil.

It was determined that the reaction temperature and mixing intensity can be optimized. Using the optimum results, the authors proposed a kinetic model that resulted in establishing an equation for the beginning rate of transesterification reaction.

Second-order polynomial model was obtained to predict biodiesel yield as a function of these variables. To add further, a simple model using a ping-pong bi-bi mechanism has been proposed, which summarizes an efficient method of noncatalytic transesterification of castor oil in supercritical methanol and ethanol.

An enzyme reacts first with one substrate to form a product and a modified enzyme. The modified enzyme would then react with a second substrate to form a final product and would regenerate the original enzyme. In this model, an enzyme is perceived as a ping-pong ball that bounces from one state to another.

Biodiesel production from castor oil is, indeed, a promising enterprise. Advances in models and simulations have facilitated optimization of key processing parameters necessary to obtain good yields of such biodiesel. In this review, we present both an extensive and intensive analysis of castor bean oil, ranging from its industrial to pharmacological use.

Moreover, this review discussed traditional and modern castor bean oil processing and the future directions as we enter the —omics and computational analysis era. We would like to thank Jayant Oils and Derivatives and SDI Farms, Inc for allowing us to use their facilities that led to the conceptualization of this manuscript. Other authors disclose no potential conflicts of interest. Paper subject to independent expert single-blind peer review. All editorial decisions made by independent academic editor.

Upon submission manuscript was subject to anti-plagiarism scanning. Prior to publication all authors have given signed confirmation of agreement to article publication and compliance with all applicable ethical and legal requirements, including the accuracy of author and contributor information, disclosure of competing interests and funding sources, compliance with ethical requirements relating to human and animal study participants, and compliance with any copyright requirements of third parties.

Author Contributions. Wrote the first draft of the manuscript: VRP. All the authors reviewed and approved the final manuscript. National Center for Biotechnology Information , U. Journal List Lipid Insights v. Lipid Insights. The hydroxyl group in ricinoleic acid Fig. For instance, the oil has relatively high viscosity and specific gravity; it is soluble in alcohols in any proportion and has limited solubility in aliphatic petroleum solvents [ 11 ].

In addition, the polar hydroxyl group in castor oil makes it compatible with plasticizers of a wide variety of natural and synthetic resins, waxes, polymers and elastomers [ 12 ].

Notable changes on the properties of the castor oil can also be due to several factors such as the method of extraction, seed varieties, weather conditions and soil type.

For instance, cold-pressed castor oils have low acid value, low iodine value and a slightly higher saponification value than solvent-extracted oil [ 1 ].

It has further been observed that castor seeds from different climatic conditions produce castor oils of different composition and physical—chemical properties [ 14 , 15 , 17 ].

Malaysian castor seeds for instance, contain total lipids castor oil reaching up to The unique properties and diverse applications of castor oil and its derivatives make castor oil popular and even more important among vegetable oils. The presence of ester linkage, a double bond and the hydroxyl group in ricinoleic acid favours the oil as a suitable renewable resource for many chemical reactions, modifications and transformations. The presence of carboxylic group for example, allow transformation of castor oil via several reactions such as esterification, amidation [ 13 , 16 , 18 ] whereas the presence of a double bond, affords the transformation of the oil through reactions such as hydrogenation [ 16 , 19 ], carbonylation [ 20 ] and epoxidation [ 21 ].

Furthermore, the hydroxyl functional group can be acetylated [ 21 , 22 ] alkoxylated [ 23 , 24 ] or removed by dehydration [ 25 , 26 ] to increase the unsaturation of the oil. Catalytic dehydration leads into formation of a new double bond in the chain of ricinoleic acid resulting into a conjugated acid.

This change imparts good flexibility, rapid drying, excellent color retention, and water resistance for protective coatings [ 26 ]. Both ring-opened glyceryl ricinoleates and epoxy alkyl ricinoleates functionalized castor oil derivatives have recently been prepared with very high yields [ 27 ].

The ring-opened glyceryl ricinoleates was achieved through catalytic ring opening and transesterification using epoxidized castor oil ECO as a raw material using Amberlyst 15 acid catalyst while the epoxy alkyl ricinoleates was achieved by transesterification of ECO with methanol using CaAl-layered double hydroxide base catalyst.

Interestingly, the physical properties of these functionalized castor-based derivatives further demostrate the opportunity to design tailor-made materials suiting industrial needs from the oil.

Pyrolysis of castor oil cleaves the molecule to produce new useful compounds such as undecylenic acid and heptaldehyde. Addition of hydrogen bromide to the cleaved castor oil produces bromo undecanoic, which upon reacting with ammonia, forms aminoundecanoic acid; a monomer for nylon 11 polymer [ 28 ]. Generally, the three functional groups in ricinoleic acid provide multitude of possibilities of converting or modifying castor oil into many other useful products depending on the intended specific uses Fig.

Chemical transformations of castor oil into castor oil based products are discussed in the subsequent sections. Addition of hydrogen to the unsaturated fatty acid in the presence of nickel or palladium catalyst transform the liquid ricinoleic acid into semi-solid saturated hydroxystearic acid Scheme 1. The semi-solid saturated ricinoleic acid is a valuable material in industries and in resin or polymer mixtures. The oil has high melting point, improved storage qualities, taste, and odor.

Moreover, the hydrogenated oil has an improved oxidative and thermal stability. A good quality hydrogenated castor with high hydroxyl value and low iodine value is obtained at K; 1.

Hydrogenation of castor oil at low pressure 1. Castor oil hydrogenation can also be done by catalytic transfer hydrogenation CTH Scheme 2. Catalytic transfer hydrogenation has the advantage in that it can utilize organic molecules as hydrogen donors at ambient pressure and moderate temperatures. Moreover, no special reactors are required and the solvent is used as a hydrogen donor along with a selected catalyst. Hydrogenated castor oil HCO is insoluble in water and in most organic solvents but it is soluble in hot organic solvents like ether and chloroform [ 29 ].

This insolubility is among good qualities that make HCO valuable for lubricant industries because of water resistance and retention of its lubricity. Moreover, the polarity and surface wetting properties of HCO are useful in cosmetics, hair dressing, solid lubricant, paint additives, manufacture of waxes, polishes, carbon paper, candles and crayons [ 28 ]. Pyrolysis is an increasingly popular option for converting biomass to solid, liquid, and gaseous fuels.

It is a thermal treatment of a biomass in the absence of air that decomposes organic biomass into low molecular weight liquid, solid and gaseous products [ 34 ].

The absence of air during pyrolysis prevents the combustion of biomass into carbon dioxide. Pyrolysis is normally done at medium to high temperature — K in which the biomass is degraded to yield pyrolysis oil or bio-oil.

An extensive review on pyrolysis of different vegetable oils such as tung oil, sunflower oil, canola oil, soybean oil, palm oil, macauba fruit oil, cooking oil, palm oils, soybean, and castor oils have been reported [ 35 ].

Generally, the process can be done by either direct thermal cracking or by a combination of thermal and catalytic cracking. Reaction products depend on the catalyst type and the reaction conditions and can range from diesel like to gasoline like fractions. Pyrolysis of triglycerides represent an alternative method for producing renewable bio-based products suitable for use in fuel and chemical applications.

Pyrolysis of castor oil for example, at K with 20 min residence time and 1. Moreover, methanolysis of castor oil yields methyl ricinoleate which upon pyrolysis under reduced pressure 6. The two products are vital intermediates in the perfumery, pharmaceutical and polymeric formulations. Heptaldehyde is also an organic solvent for various polymers and a source of emulsifier, plasticizers and insecticides. For the undecylenic acid, it serves as a source of bactericides and fungicides but also further reactions on the acid Scheme 3 can produce monomers for the formation of nylon 11 [ 28 , 37 ].

Upon heating at K in the presence of NaOH, sebacic acid a 10 carbon dicarboxylic acid and capryl alcohol 2-octanol are produced Scheme 4. Both sebacic acid and capryl alcohol have many uses. The alcohol finds its uses as plasticizer, as a solvent, dehydrater, antibubbling agent and also as a floatation agent in coal industry [ 36 ].

The esters of sebacic acid on the other hand are plasticizers for vinyl resins and are also used in the manufacture of dioctyl sebacate DOS , a jet lubricant and lubricant in air cooled combustion motors [ 1 , 38 ] Furthermore; sebacic acid is used as a monomer where it reacts with hexamethylenediamine to produce nylon 6—10 [ 38 ].

The dehydration of ricinoleic acid is an acid catalysed reaction which removes the hydroxyl group in the form of water to introduce a new double bond. The reaction results into the production of both non-conjugated linoleic acid and the conjugated linoleic acid Scheme 5 [ 37 ]. The dehydration of castor oil is usually done at temperatures above K in the presence of an acid catalyst such as concentrated sulphuric acid, phosphoric acid, p-toluenesulfonic acid, sodium bisulfate, or activated clays under inert atmosphere [ 25 ].

The formed linoleic acids have various industrial applications including the production of protective coating, vanishes, lubricants, soaps, paints, inks, manufacture of alkyd resins, coatings, appliance finishes and primers [ 1 , 39 , 40 ]. The linoleic acids are also basic ingredients in racing motor oil for high-performance automobile motorcycle engines.

Transesterification of vegetable oils refer to the breaking down of vegetable oil molecules by reacting an alcohol with an ester in the vegetable oil in which the glycerol functional group from the triglyceride is removed and replaced by an alcohol [ 18 , 41 ] producing a biodiesel Scheme 6.

The catalysts used in the transesterification are often acid catalysts e. Transesterification reactions are reversible and therefore an excess alcohol is usually used to shift the equilibrium to the formation of the biodiesel.

Generally transesterification reduces the molecular weight and thus reducing the viscosity of the castor oil which is not required in the biodiesel [ 42 ]. Transesterification also increases the volatility while maintaining the cetane number and heating value of the biodiesel [ 43 , 44 ].

The increased production of biodiesel from vegetable oils has led to the overproduction of glycerol. For instance, Worldwide crude glycerol derived from biodiesel conversion has increased from , tonnes in to 1.

Due to this overproduction of glycerol, scientists are finding new applications for refined and crude glycerol. Examples of such applications include but are not limited to the use of crude glycerol in animal feeds both for ruminants and non ruminants animals [ 46 ]. Feed stock for fermentative production 1,3-propanediol by Klebsiella pneumonia [ 47 ], biosynthesis of citric acid from crude glycerol by Yarrowia lipolytica ACA-DC [ 46 ] and fermentative conversion of crude glycerol to hydrogen by the bacterium Rhodopseudomonas palustris [ 48 , 49 , 50 ].

Glycerol can also be a good source of various solvents such as propylene glycols, glycerol ethers and esters. Crude glycerol without any purification is a green solvent and a reducing agent for metal-catalyzed transfer hydrogenation reactions and nanoparticles formation [ 51 ]. Glycerol have also shown potential as a high-boiling-point organic solvent to enhance enzymatic hydrolysis of lignocellulosic biomass during atmospheric autocatalytic organosolvent pre-treatment [ 52 ].

Synthesis of aliphatic polyesters from glycerol by reacting it with adipic acid Scheme 7 is also reported elsewhere [ 53 ]. Sulphation refers to the introduction of SO 3 group into an organic compound to produce the characteristic C-OSO 3 configuration.

Sulphation of castor oil produces sulphuric acid esters Turkey-red oil in which the hydroxyl group of ricinoleic acid has been esterified Scheme 8 [ 54 ]. The reaction is done by treating raw castor oil at room temperature or at temperature less than Kwith concentrated sulphuric acid for 3—4 h.

In addition, Turkey-red oil is an active wetting agent in dyeing and in finishing of Scheme 8 cotton and linen. It is also used in bath oil recipes along with natural or synthetic fragrance or essential oils or in shampoos [ 55 ].

The depletion of fossil fuels and environmental issues has necessitated researchers to focus their attention and efforts to the utilization of renewable resources as raw materials for the synthesis of polymeric materials.

Bio-based polymers offer a number of advantages over polymers prepared from petroleum-based monomers as they are cheaper, readily available from renewable natural resources and they possess comparable or better properties.

Some bio-based polymers are biodegradable, nontoxic and have low carbon footprints [ 56 ]. Polyamides, polyethers, polyesters and interpenetrating polymer networks have been synthesized from castor oil [ 10 , 39 , 57 — 61 ]. Most of these castor oil polymers are particularly on the production of polyurethanes, polyamides and polyesters.

In another development, the synthesis of interpenetrating polymer networks based on polyol modified castor oil polyurethane and poly 2-hydroxyethylmethacrylate has been reported [ 58 ]. Ozonolysis of castor oil followed by reduction Scheme 9 produces triglycerides of 9-carbon fatty acids with terminal hydroxyl groups.

The 9-carbon fatty acids can be used as monomers in the preparation of condensation polymers such as polyurethane, polyethers and polyesters. They are among the most important and versatile classes of polymers as they can vary from thermoplastic to thermosetting materials [ 62 — 68 ]. The industrial production of polyurethanes is normally accomplished through the polyaddition reaction between organic isocyanates and compounds containing active hydroxyl groups, such as polyols [ 68 ].

From an environmental viewpoint, this method is not advantageous because it uses highly reactive and toxic isocyanates, which are commonly produced from an even more dangerous component, phosgene [ 69 ]. In the search for green routes to the key polyurethane intermediates, fats and oils offer important alternatives for the production of diols, polyols, and other oxo chemicals, thus, enabling to substitute petrochemicals [ 20 ].

Environmentally friendly production of polyurethanes is achieved using plant-derived diols and diisocyanates or using nonisocyanate chemistries [ 70 ]. Polyurethanes prepared from vegetable oils exhibit a number of excellent properties that are attributable to its hydrophobicity. Castor oil as a source of polyols, is increasingly finding application in the manufacture of polyurethane. Polyurethane networks based on castor oil as a renewable resource polyol and poly ethylene glycol PEG with tunable biodegradation rates for biomedical implants and tissue engineering is documented elsewhere [ 10 ].

The synthesis involved the reaction of epoxy-terminated polyurethane prepolymers EPUs from castor oil with 1,6-hexamethylene diamine curing agent. This is interesting given that there are a limited number of naturally occurring triglycerides which contain the unreacted hydroxyl groups and castor oil being the only commercially-available natural oil polyol that is produced directly from a plant source as all other natural oil polyols require chemical modification prior to their use [ 63 ].

Polyurethane derived from castor oil find their applications in areas such as biomedical implants, coatings, cast elastomers, thermoplastic elastomers, rigid foams, semi-rigid foams, sealants, adhesives and flexible foams. Methoxycarbonylation of plant oils to form diesters is a crucial discovery towards making polymer precursors from plant oils. Pd 2 dba 3 , 1,2-bis ditertiarybutylphosphinomethyl benzene DTBPMB , and methane sulfonic acid in methanol have been reported to be an effective catalytic system for making linear diesters from plant oils [ 20 , 71 , 72 ].

Undecylenic acid with the double bond in the terminal position is a product of pyrolysis of ricinoleic acid from castor oil. Methoxycarbonylation of undecenoic acid or esters produces dimethyl 1,dodecanedioate, which is a component of Nylon, Overall, growth of biopolymers from castor oil industries makes the oil potential for it to play a much larger role in the world economy on polymers and to humanity.

The high percentage of ricinoleic acid and its structural features makes castor oil capable of forming covalent dative bonds with active surface dangling orbitals of chalcogenides quantum dots.

Green synthesis of chalcogenides nanomaterials using castor oil and its isolate ricinoleic acid as eco-friendly bio-based capping agents have recently been reported [ 73 — 79 ]. This is environmentally interesting because the use of castor oil and ricinoleic acid as both capping and dispersing agents, eliminate the need for the use of air-sensitive, toxic and expensive chemicals such as trioctylphosphine TOP , trioctylphosphine oxide TOPO and alkyl amines.

It is worth noting that the boiling points of castor oil and ricinoleic acid are and K, respectively and thus they are simple to work with since they are liquid at room temperature.

Literature reports the high ability of castor oil to prevent agglomeration of the synthesized nanoparticles due to the presence of long-chain hydrophobic moieties, thus forming ultra-small, well dispersed and stable quantum dots for a long period of time [ 76 — 79 ]. Some of these nanomaterials synthesized using castor oil or ricinoleic acid can be suitable for biological and medical applications because no toxic reagents are used in their preparation [ 80 ].

The diversity of chemicals and products produced from castor oil has proven that castor is an important and potential non-edible oilseed crop. The great utilitarian value in industry, agriculture, cosmetics and pharmaceutical sectors is a direct proof that castor oil is a potential bio-based starting material.

The presence of a hydroxyl group, carboxylate and double bonds in the ricinoleic acid, imparts unique properties for the derivatization of castor oil into vital industrial raw materials. It has been shown how castor oil can be used as a renewable bio-based raw material for the production a multitude of functional materials. It is equally noted that the diverse possibilities of castor oil transformation mainly depend on the presence of the three functional groups.