What Is Chlorinated Rubber Resin? An Analysis of Structural Characteristics, Chlorination Modification, and Coating Film-Formation Mechanisms

1 Material Positioning of Chlorinated Rubber Resin

1.1 Basic Characteristics of Chlorinated Rubber Resin for Coatings

Chlorinated rubber resin is a common type of chlorine-containing film-forming resin used in coatings, inks, and adhesives. It is usually produced by chlorinating natural rubber or synthetic rubber, and typically appears as a white or light-colored powder, granule, or flaky solid. Compared with the original rubber, chlorinated rubber resin no longer mainly exhibits rubber elasticity. Instead, it shows the characteristics of a thermoplastic resin with high chlorine content, solubility, and film-forming capability. Industrial chlorinated rubber resins are usually high-chlorine-content products. Some sources list the chlorine content of industrial products at approximately 62%–67%, with the specific value varying depending on raw materials, production process, and product grade.

From the perspective of coatings, the material positioning of chlorinated rubber resin can be summarized as follows:

Material Attribute	Significance for Coatings
High-chlorine-content resin	Helps form good barrier properties and water/salt resistance
Thermoplastic film-forming material	Can form a continuous coating film through solvent evaporation
Resin suitable for solvent-based systems	Suitable for formulating fast-drying, one-component coatings
Physical-drying resin	Does not rely on complex crosslinking reactions, making application and recoating relatively convenient
Chlorine-containing modified polymer	More stable than the original rubber material

1.2 Structure and Film-Formation Method

The basic performance of chlorinated rubber resin is determined by the following two questions:

① What changes occur in the molecular structure of rubber after chlorination?

② How does this resin form a coating film in coatings?

Its core logic can be summarized as:

chlorination modification of rubber molecules → high-chlorine-content thermoplastic resin → coating film formation through solvent evaporation → fast drying, easy recoating, water resistance, salt resistance, and good adhesion

Among these factors, the high chlorine content mainly affects the stability and barrier properties of the coating film, while thermoplasticity and the physical-drying film-formation method determine its fast drying, recoating performance, and ease of application.

2 Basic Concepts and Differences from Related Materials

2.1 Basic Definition of Chlorinated Rubber Resin

Chlorinated rubber resin is a thermoplastic resin obtained by chlorinating rubber raw materials such as natural rubber, synthetic polyisoprene, or polybutadiene. The chlorination reaction significantly changes the rubber molecules, which originally feature flexibility and elasticity:

① A large number of chlorine atoms are introduced into the molecular chain.

② The original unsaturated double bonds are reduced.

③ Molecular polarity is increased.

④ Resin stability is enhanced.

⑤ The material shifts from elastomeric characteristics to film-forming resin characteristics.

In coatings, chlorinated rubber resin is usually not added directly to the application system as a solid resin. Instead, it is first dissolved in a suitable organic solvent to form a resin solution, which is then combined with pigments, fillers, additives, and other components to form a coating system.

2.2 Structural and Application Differences from Natural Rubber

Chlorinated rubber resin is derived from rubber, but it should not be equated with natural rubber. Natural rubber is mainly characterized by flexible molecular chains, obvious elasticity, and a relatively high content of unsaturated structures. These structures make natural rubber suitable for elastic products, but they also make it susceptible to oxygen, ozone, ultraviolet light, and heat. If natural rubber is used directly as the main film-forming material in coatings, its aging resistance, medium resistance, and film-forming stability usually cannot meet the requirements of protective coatings. After chlorination modification, the material attributes of chlorinated rubber resin change significantly:

Comparison Item	Natural Rubber	Chlorinated Rubber Resin
Material type	Elastomer	Thermoplastic film-forming resin
Main structural characteristics	Flexible molecular chains and high unsaturation	High chlorine content and reduced unsaturated structures
Typical properties	Outstanding elasticity and flexibility	Outstanding film-forming ability, barrier properties, and stability
Role in coatings	Not commonly used as the main resin in protective coatings	Can be used as a film-forming resin in solvent-based coatings
Main applications	Elastic products	Protective coatings, inks, adhesives, etc.

2.3 Differences in Material Attributes from Chloroprene Rubber

Both chlorinated rubber resin and chloroprene rubber contain chlorine, but they differ in source, structure, and application focus.

Comparison Item	Chlorinated Rubber Resin	Chloroprene Rubber
English name	Chlorinated Rubber	Chloroprene Rubber / Polychloroprene
Source	Natural or synthetic rubber modified by chlorination	Polymerization of chloroprene monomer
Material type	Thermoplastic chlorine-containing resin	Synthetic rubber
Main uses	Film-forming or binding material in coatings, inks, and adhesives	Rubber products, adhesives, sealing materials, etc.
Key focus in coatings	Fast drying, film formation, barrier protection, and protective performance	Elasticity, bonding, weather resistance, oil resistance, and other rubber characteristics

3 Effect of Chlorination Modification on Molecular Structure

3.1 Structural Characteristics of Original Rubber Molecules

Rubber materials such as natural rubber, polyisoprene, and polybutadiene usually have flexible molecular chain structures and contain a certain number of unsaturated double bonds. This structure gives rubber good elasticity and flexibility, but it also brings certain limitations:

① Unsaturated double bonds are prone to oxidation.

② Resistance to ultraviolet light and ozone is limited.

③ Long-term exposure can lead to aging, hardening, or cracking.

④ When directly used in protective coatings, water resistance, salt resistance, and barrier performance are insufficient.

⑤ It is difficult to form a coating film that combines hardness, adhesion, and protective properties.

Therefore, to make rubber materials more suitable for coating film formation, it is necessary to reduce the adverse effects of unsaturated structures and improve molecular stability and coating-film barrier properties.

3.2 Modification of Unsaturated Structures by Chlorination

Chlorination modification is not simply a process of “adding chlorine.” In practice, it may involve structural changes such as addition, substitution, and cyclization. Overall, after chlorine atoms enter the rubber molecular structure, the original molecular chain characteristics are altered. These changes mainly include:

Structural Change	Material Effect
Chlorine atoms introduced into the molecular chain	Increased molecular polarity
Reduction of unsaturated structures	Lower oxidation sensitivity
Restricted molecular chain mobility	Material shifts from elastomeric characteristics to resin characteristics
Improved molecular stability	Better resistance to water, salt, and some corrosive media
Changed dissolution behavior	Suitable for solvent-based coating systems

After chlorination modification, the elastic characteristics of the original rubber are significantly weakened, while the hardness, polarity, stability, and film-forming ability of the resin are enhanced. This is the basis for using chlorinated rubber as a coating resin.

4 Thermoplastic Resin Attributes and Dissolution-Based Film Formation

4.1 From Elastomer to Thermoplastic Film-Forming Resin

One key attribute of chlorinated rubber resin is its thermoplasticity. Thermoplastic resins can dissolve in suitable organic solvents and form a solid coating film as the solvent evaporates after application. A coating film that has already formed may also swell or soften under the action of certain solvents.

Chlorinated rubber resin does not form a coating film through rubber vulcanization or high-level crosslinking. Instead, after solvent evaporation, resin molecules move closer together, aggregate, and form a continuous film layer. This is also an important reason why chlorinated rubber coatings are fast-drying, easy to apply, and easy to recoat.

4.2 Organic-Solvent Solubility and Suitability for Coatings

Chlorinated rubber resin is usually insoluble in water and needs to be dissolved in suitable organic solvents before being made into coatings. It is generally soluble in aromatic hydrocarbons and some ester and ketone solvents. However, its specific solubility is affected by the resin product, chlorine content, molecular weight, and solvent system, and should be confirmed based on the product technical data or actual testing. Its film-formation pathway is as follows:

Stage	State Change
Resin dissolution	Chlorinated rubber resin dissolves in an organic solvent
Coating application	Resin, pigments, fillers, and additives are distributed in the wet film
Solvent evaporation	Wet-film viscosity increases and resin concentration rises
Resin aggregation	Resin molecules gradually move closer together and form a continuous phase
Coating-film formation	A thermoplastic protective coating film is ultimately formed

5 Physical-Drying Film-Formation Mechanism

5.1 Formation of a Continuous Coating Film Through Solvent Evaporation

The main film-formation method of chlorinated rubber coatings is physical drying. Physical drying means that after coating application, the solvent gradually evaporates and the resin changes from a dissolved state into a solid continuous film. During this process, no obvious chemical crosslinking usually occurs between resin molecules. The film-formation process can be divided into four stages:

Film-Formation Stage	Main Change
Wet-film stage	The resin is dissolved in the solvent, and the coating film remains fluid
Solvent-evaporation stage	The solvent is gradually released, and coating-film viscosity increases
Initial film-formation stage	Resin molecules move closer together, and an initial surface film layer forms
Complete drying stage	Residual solvent continues to be released, and coating-film strength gradually develops

Physical drying is not the same as simple drying. The surface of the coating film may reach a tack-free state relatively quickly, but residual solvent inside the film still needs to continue releasing. Excessive film thickness, poor ventilation, or slow solvent release may affect the final coating-film performance.

5.2 Difference from Crosslinking-Curing Film Formation

The physical-drying film formation of chlorinated rubber resin differs from the crosslinking-curing film formation of reactive resins such as epoxy and polyurethane.

Comparison Item	Chlorinated Rubber Resin System	Crosslinking-Curing System
Film-formation method	Solvent evaporation and physical drying	Chemical reaction or crosslinking curing
Component form	Mostly one-component systems	Commonly two-component or multi-component systems
Film structure	Thermoplastic continuous film	Crosslinked network structure
Application characteristics	Relatively convenient formulation and application	Requires ratio control, mixing, and pot-life management
Recoating characteristics	Old film can be rewetted by the solvent in the new coating	Recoating depends more on surface treatment and recoat intervals
Typical advantages	Fast drying, easy application, easy recoating	Usually stronger solvent resistance, heat resistance, and mechanical strength

6 Reasons for the Formation of Basic Properties

6.1 Reason for Fast Drying

The fast-drying property of chlorinated rubber coatings mainly comes from their physical-drying film-formation method. Since coating-film formation does not rely on complex chemical reactions, after application, as long as the solvent gradually evaporates, the resin concentration increases and a continuous film forms, allowing the coating film to reach a tack-free state relatively quickly.

The main factors affecting drying speed include resin dissolution state, solvent evaporation rate, coating-film thickness, ambient temperature, air flow, pigment/filler content, and wet-film structure.

6.2 Reason for Recoating Performance

Chlorinated rubber coatings usually have good recoating performance, which is related to their thermoplastic film-forming characteristics. When a new coat is applied over an old coating film, the solvent in the new coating can wet and slightly swell the surface of the old film, allowing the new and old coating layers to form closer contact.

The basic process can be summarized as follows:

old film surface rewetted by solvent → surface resin slightly activated → good intercoat bonding formed between old and new coating layers

This is also one of the important reasons why chlorinated rubber coatings are suitable for maintenance applications.

However, good recoating performance does not mean that application control can be ignored. If the solvent in the new coating has excessive solvency, the application is too thick, or the old film is in poor condition, defects such as softening, wrinkling, or poor appearance of the old coating may occur.

6.3 Sources of Barrier Properties and Water/Salt Resistance

The important value of chlorinated rubber resin in protective coatings lies in its ability to form a relatively continuous and dense coating film, which hinders the migration of water, oxygen, and salts toward the substrate surface. Its water resistance, salt resistance, and barrier properties mainly come from three aspects:

① High-chlorine-content structure

Chlorination modification increases the polarity and stability of resin molecules, helping form a more stable coating-film structure.

② Reduction of unsaturated structures

After some of the unsaturated double bonds in the original rubber are modified, the resin becomes less sensitive to oxidation and environmental aging.

③ Continuous thermoplastic film layer

After solvent evaporation, resin molecules form a continuous film layer, reducing the permeation rate of water vapor, oxygen, and salts.

The medium resistance of chlorinated rubber resin is mainly reflected in its good resistance to water, salt spray, industrial atmospheres, and some dilute acids and dilute alkalis. It should not be generalized as having high resistance to all chemicals.

6.4 Structural Basis of Adhesion Performance

Chlorinated rubber resin has a good adhesion basis for metals and mineral substrates, which is related to the increased molecular polarity after chlorination. Increased molecular polarity improves the wetting and contact ability of the resin on the substrate surface, helping form good interfacial bonding.

Coating-film adhesion is not determined solely by the resin. It is also affected by substrate cleanliness, surface roughness, substrate moisture content, solvent system, coating-film thickness, application environment, and coating-system compatibility. Chlorinated rubber resin provides the material basis for adhesion performance, while the final adhesion result still depends on the coating system and application quality.

6.5 Relationship Between Structure, Film Formation, and Performance

Structural or Film-Formation Feature	Direct Effect	Coating Performance
High chlorine content	Increased polarity and stability	Good water resistance, salt resistance, and barrier properties
Reduced unsaturated structures	Lower oxidation sensitivity	Better stability than the original rubber
Thermoplastic resin attribute	Soluble and rewettable	Fast drying and easy recoating
Physical-drying film formation	Does not rely on complex crosslinking reactions	Convenient one-component application
Continuous coating-film formation	Reduces migration of water, oxygen, and salts	Provides protection for the substrate
Non-highly-crosslinked structure	Coating film can be affected by strong solvents	Limited resistance to strong solvents and high temperatures
Reduced segmental flexibility after chlorination	Coating film may be relatively hard	Flexibility needs to be adjusted through formulation

It should be noted that chlorinated rubber coating films are thermoplastic physical-drying films. Their resistance to strong solvents, high temperatures, and long-term intense UV exposure is usually inferior to that of crosslinked systems such as epoxy and polyurethane. Under high-temperature or strong light-and-heat conditions, attention should also be paid to risks such as coating-film softening, chalking, loss of gloss, or thermal decomposition with hydrogen chloride release.

7 Research Reagents Related to Structural Understanding, Solubility Evaluation, and Residue Control of Chlorinated Rubber Resin

Table 1 Rubber Raw Materials and Related Polymer Reference Materials

Category	CAS No.	Aladdin Cat. No.	Name	Specification or Purity	Product Features and Applications
Rubber raw material	9003-17-2	P485919	Polybutadiene, mainly 1,2-addition	Approx. 90% 1,2-vinyl	Can be used to study the effects of vinyl content in polybutadiene structure on chlorination reactions, changes in segmental polarity, and performance of film-forming resins
Rubber raw material	104389-31-3	P485890	Polyisoprene, cis	GPC average Mw ~38,000, made from natural rubber	Can be used as a structural model of natural rubber to understand the structural basis for the conversion of cis-polyisoprene into chlorinated rubber resin after chlorination
Rubber raw material	104389-32-4	P347708	trans-Polyisoprene	≥99% trans-1,4, pellets	Can be used to compare the differences between cis- and trans-polyisoprene in chain-segment regularity, crystallization tendency, and chlorination modification research
Easily confused chlorine-containing rubber material	9010-98-4	P466846	Polychloroprene	85% trans, 10% cis	Can be used to distinguish chlorinated rubber resin from chloroprene rubber in terms of structural source, material attributes, and coating application differences
Related chlorine-containing polymer	9002-86-2	P107106	Polyvinyl chloride (PVC)	K-value 72–71	Can be used as a chlorine-containing polymer reference material to compare PVC and chlorinated rubber resin in terms of solubility, polarity, and film-forming behavior

Table 2 Reagents Related to Dissolution-Based Film Formation and Residue Control

Category	CAS No.	Aladdin Cat. No.	Name	Specification or Purity	Product Features and Applications
Ester solvent	141-78-6	E119698	Ethyl acetate	Anhydrous grade, ≥99.8%	Can be used to study the solubility, evaporation rate, and physical-drying film-formation process of chlorinated rubber resin
Aromatic hydrocarbon solvent	108-88-3	T399633	Toluene (regulated precursor chemical)	Anhydrous grade, ≥99.8%	Can be used for chlorinated rubber resin solution preparation, viscosity testing, and solvent-evaporation film-formation experiments
Ester solvent	123-86-4	B119685	Butyl acetate	Anhydrous grade, ≥99%	Can be used to adjust the evaporation gradient, leveling, and surface-drying process of chlorinated rubber resin coating systems
Aromatic hydrocarbon solvent	1330-20-7	X139941	Xylene	Anhydrous grade, ≥98%, mixture of isomers	Can be used for chlorinated rubber resin dissolution, resin solution preparation, and solvent-based coating film-formation research
Ketone solvent	78-93-3	B1506282	Methyl ethyl ketone, MEK (regulated precursor chemical)	AR, ≥99%	Can be used to improve the solvency for chlorinated rubber resin and is suitable for resin solution preparation and fast-drying film-formation experiments
Ketone solvent	108-10-1	M108740	Methyl isobutyl ketone, MIBK	AR, ≥99.5%	Can be used in chlorinated rubber resin coatings to adjust solvency, evaporation rate, and application open time
Ketone solvent	108-94-1	C116451	Cyclohexanone	≥99.5% (GC)	Can be used for chlorinated rubber resin solubility research and the design of slower-evaporating solvent components
Ketone solvent	67-64-1	A399767	Acetone (regulated precursor chemical)	≥99.5%	Can be used for solubility screening, evaporation-behavior comparison, and fast-drying film-formation research; its solvency for different chlorinated rubber resins should be confirmed through actual testing
Process residue and compliance concern	56-23-5	C639782	Carbon tetrachloride	Analytical standard, ≥99.9%	Can be used for carbon tetrachloride residue testing, method development, and quality-control research in chlorinated rubber resin

Note: The above are representative Aladdin products. More product specifications can be searched on the Aladdin website by product name, CAS number, or catalog number.

References

[1] LOOK Chemical. A Brief Discussion on Chlorinated Rubber Coatings.

[2] Covestro. Pergut® | Powdered Chlorinated Polymers.

[3] Junteng Chemical. Chlorinated Rubber for Corrosion-Resistant Coatings.

[4] Galaxy International FZC. Chlorinated Rubber.

For more related articles, please see below:

A Panorama Guide to Synthetic Resins: Definitions & Polymerization Mechanisms, Classification Frameworks, Common Resins and Applications, Packaging Codes, and a Selection Roadmap (Tables 1–3)