Alkyd Resins: From Oil/Fatty-Acid-Modified Polyesters to Autoxidative Drying — Understanding Their Structure and Film-Formation Mechanism
Alkyd Resins: From Oil/Fatty-Acid-Modified Polyesters to Autoxidative Drying — Understanding Their Structure and Film-Formation Mechanism
1. What Is an Alkyd Resin?
Alkyd resins are a class of oil- or fatty-acid-modified polyester resins. They are typically prepared by esterification polycondensation of polyols, polyacids or acid anhydrides, and vegetable oils or fatty acids. The name “alkyd” is derived from alcohol and acid, reflecting the basic feature that these resins are formed by polycondensation of alcohol-based and acid-based raw materials.
From a structural perspective, an alkyd resin is neither simply a natural oil nor an ordinary polyester. Its molecular structure contains all of the following:
1. Polyester backbone
Formed by the reaction between polyols and polyacids or acid anhydrides, this is the main structural framework of the resin.
2. Fatty acid segments
Introduced from vegetable oils or fatty acids, these segments impart flexibility, solubility, and oxidative drying capability to the resin.
3. Unsaturated structures
The unsaturated structures related to air-drying mainly come from unsaturated fatty acids. They are the basis for oxidative crosslinking between air-drying alkyd resins and oxygen in the air.
The essence of an alkyd resin can be summarized as follows: an alkyd resin is a film-forming resin that uses a polyester structure as its backbone, fatty acid segments as modifying components, and can undergo air-oxidative crosslinking through unsaturated fatty acids.
2. Structural Basis and Performance Origin of Alkyd Resins
The performance and drying behavior of alkyd resins depend strongly on their molecular structure. Simply knowing whether an alkyd is “long-oil,” “medium-oil,” or “short-oil” is not enough to understand alkyd resins, because oil length is only one structural variable. Factors that determine the behavior of alkyd resins include:
Structural factor | Direction of influence |
Type of polyol | Affects branching degree, molecular weight growth, and residual hydroxyl groups |
Type of polyacid/acid anhydride | Affects the rigidity, polarity, and ester-bond structure of the polyester backbone |
Type of oil or fatty acid | Affects unsaturation, oxidative drying capability, and flexibility |
Oil length | Affects the ratio between fatty acid segments and the polyester backbone |
Acid value, hydroxyl value, viscosity | Reflect the degree of polycondensation and the control state of the resin structure |
Drier system | Affects the rate of oxidative crosslinking and the balance of drying |
The structural logic of alkyd resins can be understood as follows: raw materials determine the structure; raw materials and formulation ratios determine structural variables, including oil length and unsaturation; oil length and unsaturation determine the potential for oxidative drying; and the drier system determines the actual drying efficiency.
3. Basic Raw Material Composition of Alkyd Resins
Alkyd resins are mainly composed of three types of raw materials: polyols, polyacids or acid anhydrides, and vegetable oils or fatty acids.
3.1 Polyols
Polyols provide hydroxyl groups, which react with acidic components through esterification to form a polyester structure.
Polyol | Structural characteristics | Influence on resin structure |
Glycerol | Trifunctional alcohol | A traditional raw material commonly used in alkyd resins; can form branched structures |
Pentaerythritol | Tetrafunctional alcohol | Increases branching degree and molecular weight growth efficiency, but gelation risk must be controlled |
Trimethylolpropane | Trifunctional alcohol | Helps form relatively stable branched structures |
Ethylene glycol, neopentyl glycol | Difunctional alcohols | Help form relatively linear polyester segments |
The higher the functionality of the polyol, the more easily the resin forms a branched structure. Moderate branching helps improve the cohesive strength of the film after formation, but excessive branching may cause overly high viscosity during the reaction and may even lead to gelation.
3.2 Polyacids or Acid Anhydrides
Polyacids or acid anhydrides provide carboxyl groups or anhydride groups, which react with polyols to form ester bonds. They are another core raw material for constructing the polyester backbone.
Acid raw material | Structural characteristics | Influence on resin structure |
Phthalic anhydride | Aromatic acid anhydride | A classic alkyd raw material that provides rigidity and cost effectiveness |
Isophthalic acid | Aromatic diacid | Can improve the stability of the polyester backbone |
Maleic anhydride | Contains unsaturated structure | Can introduce unsaturated structures and reactivity for structural modification, but air-drying oxidation still mainly relies on unsaturated fatty acid segments; side reactions must be controlled |
Trimellitic anhydride | Multifunctional acid anhydride | Can increase branching degree and acid-value control capability |
The ester bonds in alkyd resins are mainly formed by the reaction between polyols and acidic raw materials. Ester bonds are the fundamental structure of the polyester backbone, and they also determine that alkyd resins have a certain degree of hydrolytic sensitivity under conditions such as water, alkali, and high temperature.
3.3 Vegetable Oils or Fatty Acids
Vegetable oils or fatty acids are the key raw materials that distinguish alkyd resins from ordinary polyesters. They introduce long-chain fatty acid structures into the polyester, giving the resin oil-modified characteristics. Fatty acid segments mainly provide three functions:
1. Improving flexibility
Long-chain fatty acids have flexible structures and can reduce the brittleness of ordinary polyesters.
2. Improving solubility and flow
Fatty acid segments have relatively strong nonpolar characteristics, which help the resin dissolve in traditional organic solvents and improve application flow.
3. Providing oxidative crosslinking sites
The carbon-carbon double bonds in unsaturated fatty acids and the adjacent active positions are the basis for autoxidative crosslinking in air-drying alkyd resins.
For fatty acids, their degree of unsaturation and double-bond structure should be considered. In general, the higher the content of polyunsaturated fatty acids, the more readily oxidative drying occurs; the higher the content of saturated fatty acids, the weaker the air-drying capability. The degree of unsaturation of the fatty acids, whether they contain hydroxyl groups, and the hydroxyl value of the resin all affect the structure and performance of alkyd resins.
4. Synthesis Routes and Process Control of Alkyd Resins
The synthesis of alkyd resins is essentially an esterification polycondensation reaction. The hydroxyl groups in polyols react with the carboxyl groups in polyacids or acid anhydrides to form ester bonds, while vegetable oils or fatty acids are introduced into the resin structure.
The common industrial synthesis routes for alkyd resins mainly include three types: the fatty acid process, the alcoholysis process, and the acidolysis process. Among them, the fatty acid process and alcoholysis process are the most commonly discussed in the coatings field.
4.1 Fatty Acid Process
The fatty acid process involves direct esterification polycondensation of fatty acids, polyols, and polyacids or acid anhydrides. Its basic process is as follows:
1. Fatty acids undergo esterification with polyols.
2. Polyacids or acid anhydrides further participate in the reaction, forming the polyester backbone.
3. As polycondensation proceeds, the acid value decreases, while molecular weight and viscosity increase.
4. After the target acid value and viscosity are reached, the system is cooled and diluted to the target solids content to obtain the resin solution.
The advantage of the fatty acid process is that the fatty acid composition is relatively defined, making it easier to adjust the resin structure and drying property. The disadvantage is that it has certain requirements for the quality and cost of fatty acid raw materials.
4.2 Alcoholysis Process
The alcoholysis process usually uses vegetable oil as the raw material. Vegetable oils are mainly fatty acid glycerides and cannot directly undergo sufficiently uniform polycondensation with acid anhydrides. Therefore, they are usually first subjected to alcoholysis with polyols to generate monoglycerides or partial glycerides, which are then polycondensed with polyacids or acid anhydrides. The basic process is as follows:
1. Vegetable oil undergoes alcoholysis with polyols.
2. Hydroxyl-containing monoglyceride or partial glyceride intermediates are formed.
3. Polyacids or acid anhydrides are added for esterification polycondensation.
4. The reaction endpoint is controlled by acid value, viscosity, color, and tolerance.
The advantage of the alcoholysis process is that vegetable oils can be used directly, giving it good economic efficiency. The disadvantage is that vegetable oils are mixed fatty acid glycerides with complex compositions, so the resin structure distribution is usually broader than that obtained by the fatty acid process.
4.3 Key Control Indicators During Synthesis
Alkyd resin synthesis is not simply a matter of making the reaction “complete”; rather, the resin must be controlled at an appropriate structural state.
Indicator | Structural meaning | Application judgment |
Acid value | Reflects the residual carboxyl content and esterification degree in the resin | Affects resin polarity, compatibility, storage stability, and potential for waterborne modification |
Hydroxyl value | Reflects the residual hydroxyl content in the resin | Affects reactivity with crosslinkers such as amino resins and isocyanates |
Viscosity | Reflects molecular weight, branching degree, and solids content state | Affects application properties, leveling, dilution behavior, and formulation compatibility |
Color | Reflects raw material color, side reactions, and thermal history | Affects the appearance of clear varnishes, white paints, and light-colored paints |
Compatibility | Reflects matching between the resin and solvents, additives, or other resins | Affects system transparency, storage stability, and film uniformity |
Among these, acid value and viscosity are the most commonly used indicators in synthesis control. An excessively high acid value usually indicates insufficient esterification; excessively high viscosity may indicate excessive molecular weight growth or that the system is approaching the risk of gelation.
5. Oil Length: A Key Indicator for Understanding Structural Differences in Alkyd Resins
Oil length refers to the proportion of oil or fatty acid components in an alkyd resin. According to oil length, alkyd resins are usually classified as long-oil alkyds, medium-oil alkyds, and short-oil alkyds.
According to the classification given by Britannica: long-oil alkyds contain about 60% fatty acids, medium-oil alkyds contain about 40%–60% fatty acids, and short-oil alkyds contain less than 40% fatty acids. The ranges may vary slightly among different sources and company standards, but the basic classification logic is consistent.
Type | Common oil length range | Structural characteristics | Influence on drying mechanism |
Long-oil alkyd | About 60% or higher | High proportion of fatty acid segments and low proportion of polyester backbone | More oxidative reaction sites, but in-film oxidation and hardening rate are strongly affected by oil type and oxygen diffusion |
Medium-oil alkyd | About 40%–60% | Relatively balanced ratio of fatty acid segments and polyester backbone | Oxidative crosslinking capability and contribution from the polyester backbone are relatively balanced |
Short-oil alkyd | Below about 40% | High proportion of polyester backbone and low proportion of fatty acid segments | The proportion of fatty acid segments is relatively low, so independent air-drying capability is comparatively limited; if used in an air-drying system, it must be designed together with highly unsaturated oils or fatty acids and an appropriate drier system |
When understanding oil length, three points should be noted:
1. Oil length reflects a structural proportion, not a single performance indicator
A high oil length means more fatty acid segments; a low oil length means a higher proportion of polyester backbone.
2. Oil length affects drying, but does not determine drying by itself
Even for long-oil alkyds, if the degree of fatty acid unsaturation differs, the oxidative drying capability may differ significantly.
3. Oil length should be evaluated together with oil type
Oil length answers the question “how many fatty acid segments are present,” while oil type answers the question “how readily these fatty acid segments oxidize.”
Therefore, when evaluating the structure of an alkyd resin, one should not only look at whether it is “long-oil,” “medium-oil,” or “short-oil.” Fatty acid composition, unsaturation, acid value, hydroxyl value, and viscosity should also be considered.
6. Drying Oils, Semi-Drying Oils, and Non-Drying Oils
Whether an alkyd resin can air-dry depends primarily on whether its fatty acid segments have sufficient unsaturated structures. In the coatings industry, oils are commonly classified as drying oils, semi-drying oils, and non-drying oils.
Type | Structural characteristics | Significance for alkyd resins |
Drying oil | High content of polyunsaturated fatty acids | Readily undergoes air-oxidative crosslinking and is suitable for preparing air-drying alkyds |
Semi-drying oil | Moderate degree of unsaturation | Can undergo oxidative drying, but drying rate and degree of hardening are strongly affected by formulation |
Non-drying oil | Insufficient effective unsaturated structures | Weak air-drying capability and greater dependence on other film-forming or crosslinking methods |
Common drying oils include linseed oil and tung oil; soybean oil is usually classified as a semi-drying oil; oils with relatively high proportions of saturated fatty acids, such as coconut oil, are generally not suitable as the main drying source for air-drying alkyds.
It should be noted that drying oils, semi-drying oils, and non-drying oils are only relative classifications of the oxidative drying capability of oils. They cannot be used alone to determine the actual drying performance of an alkyd resin. The actual drying rate and degree of hardening are also affected by factors such as fatty acid composition, unsaturation, degree of double-bond conjugation, resin structure, and drier system.
From a structural perspective, an air-drying alkyd resin needs to meet the following conditions:
1. The resin contains unsaturated fatty acid segments.
2. The unsaturated structures can undergo autoxidation with oxygen in the air.
3. Free radicals formed during oxidation can initiate intermolecular crosslinking.
4. Driers can promote peroxide decomposition and improve reaction efficiency.
7. The Drying Essence of Air-Drying Alkyd Resins
The drying of air-drying alkyd resins is not simply solvent evaporation. Instead, it is completed through two processes:
1. Physical drying: solvent evaporation
After application, the solvent first evaporates, the resin concentration increases, and the coating film gradually loses fluidity.
2. Chemical drying: autoxidative crosslinking
Unsaturated fatty acid segments react with oxygen in the air, forming peroxides and free radicals, eventually leading to intermolecular crosslinking and gradual hardening of the film.
The drying process of an air-drying alkyd resin can be simplified as follows:
Solvent evaporation → resin concentration and film formation → oxygen uptake by unsaturated fatty acid segments and formation of hydroperoxides → drier-promoted decomposition of hydroperoxides → free-radical reactions and intermolecular crosslinking → gradual hardening of the coating film
8. Autoxidative Drying Mechanism
Autoxidation is the core reaction in the film formation of air-drying alkyd resins. It mainly occurs on unsaturated fatty acid segments, especially at active positions adjacent to double bonds.
8.1 Induction Stage
After the coating film is formed, unsaturated fatty acid segments begin to contact oxygen in the air. At this stage, the reaction rate is relatively low, and the system gradually generates small amounts of free radicals and oxidative intermediates.
8.2 Hydroperoxide Formation Stage
The unsaturated fatty acid segments are oxidized to form hydroperoxides. Hydroperoxides are important intermediates for subsequent free-radical reactions.
8.3 Hydroperoxide Decomposition Stage
Under the action of metal driers, hydroperoxides decompose to produce active species such as alkoxy radicals and peroxy radicals. This stage has a significant influence on drying speed.
8.4 Crosslinking Stage
Free radicals continue to undergo coupling, addition, and oxidation reactions, forming crosslinked structures between different resin molecules. As crosslink density increases, the coating film gradually changes from a soft and tacky state to a through-dried and hardened state.
The structural changes at each stage can be understood through the following table:
Stage | Main change | Result |
Induction stage | Oxygen begins to participate in the reaction | Active intermediates gradually form |
Peroxide formation | Fatty acid segments are oxidized | Hydroperoxides are formed |
Peroxide decomposition | Driers promote free-radical generation | Oxidation reactions accelerate |
Intermolecular crosslinking | Free radicals undergo coupling or addition | A crosslinked network forms in the coating film |
9. Role of Driers in the Drying Process
Although air-drying alkyd resins can undergo autoxidation with oxygen in the air, in practical coatings, drying speed usually cannot meet application requirements without driers. Driers are usually metal carboxylates or related metal complexes. Their core function is to promote hydroperoxide decomposition and accelerate free-radical generation, thereby driving oxidative crosslinking.
9.1 Mechanism of Action of Driers
The core function of driers is to promote the decomposition of hydroperoxides during the oxidative drying of alkyd resins. This can be simplified as follows:
ROOH decomposes under the action of metal driers → alkoxy radicals RO· / peroxy radicals ROO· are generated → further oxidation and coupling of fatty acid segments are initiated → intermolecular crosslinked structures form → the coating film gradually hardens
Metal driers do not dry the coating film by “absorbing solvent.” Instead, they participate in the autoxidation reaction through redox cycles, promoting free-radical generation and chemical crosslinking. Solvent evaporation is only part of the physical drying process. The key factor that gradually hardens an air-drying alkyd coating film is oxidative crosslinking of unsaturated fatty acid segments.
9.2 Primary Driers and Auxiliary Driers
Type | Common metals | Main function |
Primary driers | Cobalt, manganese, iron, etc. | Promote peroxide decomposition and accelerate oxidative drying |
Auxiliary driers | Calcium, zirconium, zinc, etc. | Improve through-drying, act synergistically with primary driers, and adjust drying balance |
Anti-skinning-related additives | Ketoximes, etc. | Inhibit premature surface oxidation and skin formation in the can |
The use of driers requires balance. Excessively strong primary driers may cause overly rapid surface oxidation; insufficient drier loading may lead to delayed drying. The key is to keep surface oxidation, internal oxidation, and solvent evaporation coordinated.
10. Mechanistic Differences Among Surface Drying, Through-Drying, and Post-Hardening
The drying of alkyd resins occurs in stages. Surface drying, through-drying, and hard drying represent different degrees of physical evaporation and chemical crosslinking.
Drying state | Observable behavior | Mechanistic meaning |
Surface dry | The surface is not obviously tacky | Surface solvent has evaporated and initial oxidation has occurred |
Through-dry | The overall coating film is basically no longer fluid | The interior of the coating film has also undergone relatively sufficient oxidative crosslinking |
Hard dry | The coating film has reached a relatively high degree of hardness | The crosslinked network further develops, and film strength increases |
After an alkyd resin becomes surface-dry, the interior may still continue to absorb oxygen and undergo crosslinking. Therefore, air-drying alkyd coating films often exhibit a post-hardening process. The main factors affecting this process include:
1. Resin oil length.
2. Fatty acid unsaturation.
3. Type and dosage of driers.
4. Coating film thickness.
5. Oxygen diffusion conditions.
6. Temperature, humidity, and ventilation conditions.
11. Overall Relationship Between Structure and Film-Formation Mechanism
The relationship between alkyd resin structure and drying mechanism can be summarized in the following table.
Structure or factor | Influence on film-formation mechanism |
Polyester backbone | Provides the main resin structure and basic cohesive strength |
Fatty acid segments | Provide flexibility and oxidation reaction sites |
Unsaturated double bonds | Determine whether air-oxidative crosslinking can occur |
Oil length | Determines the ratio between fatty acid segments and the polyester backbone |
Acid value | Reflects residual carboxyl groups and degree of esterification |
Hydroxyl value | Reflects residual hydroxyl groups and potential reactivity |
Viscosity | Reflects molecular weight, branching degree, and solids content state |
Driers | Promote peroxide decomposition and free-radical generation |
Oxygen diffusion | Affects the balance of surface drying, through-drying, and thick-film drying |
12. Raw Materials and Additives Related to Alkyd Resin Structure Construction and Oxidative Drying with Tables 1–3
Table 1. Raw Materials for Constructing the Polyester Backbone of Alkyd Resins
Category | CAS No. | Aladdin Cat. No. | Name | Specification or purity | Product features and applications |
Polyacid/acid anhydride | 85-44-9 | o-Phthalic anhydride | Guaranteed reagent, ≥99% | A classic aromatic acid anhydride raw material used to construct the polyester backbone of alkyd resins; affects resin rigidity, acid value, and the polycondensation reaction process | |
Polyol | 56-81-5 | Glycerol | For electrophoresis, ≥99% | A trifunctional polyol raw material used in oil-modified polyester synthesis; affects resin branching structure, hydroxyl content, and molecular weight growth | |
Polyol | 107-21-1 | Ethylene glycol | Anhydrous, ≥99.8% | A difunctional polyol raw material used to adjust polyester segment structure, esterification reaction, and resin viscosity | |
Monofunctional acid/structure modifier | 65-85-0 | Benzoic acid | Sublimed grade, ≥99% | A monofunctional aromatic carboxylic acid used to adjust molecular weight, acid value, and chain-end structure of alkyd resins | |
Polyacid/acid anhydride | 108-31-6 | Maleic anhydride | AR, ≥99% (GC) | An acid anhydride raw material containing unsaturated structures; used for structural modification of alkyd resins, reactivity control, and introduction of unsaturated backbone structures | |
Polyacid/acid anhydride | 121-91-5 | Isophthalic acid | AR, ≥99% | An aromatic diacid raw material used to construct the polyester backbone; affects resin structural stability, rigidity, and the basis of resistance properties | |
Polyol | 115-77-5 | P103696 | Pentaerythritol | AR, ≥98% | A tetrafunctional polyol raw material used to increase the branching degree, hydroxyl density, and crosslinking precursor structure of alkyd resins |
Polyol | 126-30-7 | Neopentyl glycol | ≥99% | A sterically hindered diol raw material used to adjust polyester segment structure, resin stability, and polycondensation reaction design | |
Polyol | 77-99-6 | 1,1,1-Tris(hydroxymethyl)propane | ≥98% | A trifunctional polyol raw material used in the design of branched alkyd resin structures; affects hydroxyl value, viscosity, and film-forming network precursors | |
Polyacid/acid anhydride | 552-30-7 | 1,2,4-Benzenetricarboxylic anhydride | ≥97% | A trifunctional aromatic acid anhydride raw material used to adjust branched structure, acid value, and waterborne alkyd resin structural design |
Table 2. Oils and Fatty Acid Modification Raw Materials
Category | CAS No. | Aladdin Cat. No. | Name | Specification or purity | Product features and applications |
Semi-drying oil | 8001-22-7 | Soybean oil | Reagent grade | A semi-drying vegetable oil raw material used to prepare soybean-oil-modified alkyd resins and to study oil length, unsaturation, and oxidative drying behavior | |
Hydroxyl-containing oil | 8001-79-4 | C434218 | Castor oil | European Pharmacopoeia (Ph. Eur.) | A hydroxyl-containing fatty acid oil raw material used for castor-oil-modified alkyd resins; adjusts the hydroxyl characteristics, flexibility, polarity, and resin hydroxyl value of fatty acid segments |
Saturated fatty acid | 57-11-4 | Stearic acid | Moligand™, Standard for GC, ≥99% (GC) | A saturated long-chain fatty acid used to compare the effects of saturated segments on the hydrophobicity, flexibility, and oxidative drying capability of alkyd resins | |
Monounsaturated fatty acid | 112-80-1 | Oleic acid | Moligand™, ≥99% (HPLC) | A monounsaturated fatty acid used to study the influence of a single double-bond structure on the flexibility, oil length, and oxidative reaction activity of alkyd resins | |
Polyunsaturated fatty acid | 60-33-3 | Linoleic acid | Moligand™, ≥99% (GC) | A dienoic unsaturated fatty acid used to study unsaturation, autoxidation rate, and crosslinking film-formation behavior | |
Polyunsaturated fatty acid | 463-40-1 | Linolenic acid (α-Lnn) | Moligand™, ≥99% | A trienoic unsaturated fatty acid used to study oxidative drying, free-radical crosslinking, and drying-oil structures in alkyd resins | |
Drying oil | 8001-26-1 | Linseed oil | ≥99% | A typical drying vegetable oil raw material used for the preparation of linseed-oil alkyd resins and air-drying oxidative crosslinking experiments | |
Drying oil | 8001-20-5 | Tung oil | — | A conjugated unsaturated drying oil raw material used to study tung-oil-modified alkyd resins, oxidative drying rate, and crosslinking reactions |
Table 3. Additives Related to Oxidative Drying and Metal Drier Systems
Category | CAS No. | Aladdin Cat. No. | Name | Specification or purity | Product features and applications |
Metal soap raw material | 149-57-5 | 2-Ethylhexanoic acid | Chemical pure (CP), ≥98% | A raw material for preparing metal carboxylate driers; used in synthesis studies of cobalt, manganese, iron, zirconium, zinc, calcium, and other drier systems | |
Auxiliary drier | 22464-99-9 | Zirconyl 2-ethylhexanoate in mineral spirits (~6% Zr) | In mineral spirits (~6% Zr) | A zirconium-based auxiliary drier used to study through-drying of alkyd coating films, surface/through-drying balance, and synergistic drying with metal soaps | |
Auxiliary drier | 136-53-8 | Zinc 2-ethylhexanoate | ca. 80% in mineral spirits (17–19% Zn) | A zinc-based auxiliary drier used to study synergistic oxidative drying of alkyds, storage stability, and drying balance of coating films | |
Primary drier | 136-52-7 | Cobalt(II) 2-ethylhexanoate solution | 65 wt.% in mineral spirits | A cobalt-based primary drier used to promote hydroperoxide decomposition, free-radical generation, and surface-drying reactions of alkyd resins | |
Primary drier | 7321-53-1 | Iron(III) 2-ethylhexanoate solution | 50 wt.% in mineral spirits | An iron-based drier used for autoxidation catalysis of alkyd resins, cobalt-free drier systems, and comparative studies of metal driers | |
Auxiliary drier | 136-51-6 | Calcium 2-ethylhexanoate | ≥98% | A calcium-based auxiliary drier used to improve drier-system synergy, pigment wetting, and storage stability of alkyd coatings |
References
[1] Encyclopaedia Britannica. Alkyd Resin: Uses, Properties & Manufacturing Process. Encyclopaedia Britannica.
[2] ScienceDirect Topics. Alkyd Resins — Chemical Engineering. Elsevier.
[3] Soucek M. D., Khattab T., Wu J. Review of Autoxidation and Driers. Progress in Organic Coatings, 2012, 73(4): 435–454. DOI: 10.1016/j.porgcoat.2011.08.021.
[4] Soucek M. D., Salata R. R. Alkyd Resin Synthesis. In: Kobayashi S., Müllen K., eds. Encyclopedia of Polymeric Nanomaterials. Springer, Berlin, Heidelberg, 2014. DOI: 10.1007/978-3-642-36199-9_278-1.
[5] Ding Yongbo, Gong Dunhong, Xia Yun, Shen Liang. Curing Mechanism and Driers of Autoxidation Alkyd Resin Coatings. Paint & Coatings Industry, 2019(7): 76–80. DOI: 10.12020/j.issn.0253-4312.2019.7.76.
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