Cellulose Acetate Butyrate and Cellulose Esters: Analysis of Supplier, Structure, Performance and Application

Cellulose Acetate Butyrate and Cellulose Esters: Comprehensive Analysis of Structure, Performance and Application

Cellulose acetate butyrate (CAB, sometimes called CAB resin), is a significant cellulose ester. The semi-synthetic polymer features unique characteristics and diverse applications. From here, you can see that cellulose ester is a large category, which includes the cellulose acetate butyrate series of products.

In order to further understand the difference between the two, this article will systematically introduce the relationship between CAB and other cellulose esters. It includes their suppliers, chemical structure, synthesis method, performance characteristics and applications in different industrial fields. Comparative analysis helps users better understand these materials' scientific properties, technical advantages, and real-world applications in coatings, inks, plastics, and films. The article also covers the latest research and future trends, serving as a reference for researchers and engineers.

Overview of Cellulose Esters

Cellulose esters are a type of polymer compound derived from natural cellulose through esterification reaction, and its history can be traced back to the mid-19th century. In 1865, French chemist Paul Schützenberger first produced cellulose acetate by reacting acetic anhydride with cellulose, which pioneered the chemical modification of cellulose6. With the development of the chemical industry, in the early 20th century, a variety of cellulose esters were developed and industrialized, including cellulose acetate (CA), cellulose acetate propionate (CAP) and cellulose acetate butyrate (CAB). These materials have gradually replaced some petroleum-based synthetic polymer materials in many fields due to their excellent performance and renewable properties (this is an important knowledge point).

So how do you distinguish the classification of these cellulose esters? At present, iSuoChem mainly divides cellulose into 3 different categories based on the type of substituent group:

 Cellulose acetate (CA): only contains acetyl (-COCH₃) as a substituent

 Cellulose acetate propionate (CAP): contains both acetyl and propionyl (-COC₂H₅)

 Cellulose acetate butyrate (CAB): contains both acetyl and butyryl (-COC₃H₇)

The typical structural feature of CAB is the simultaneous presence of acetyl, butyryl and a small amount of unreacted hydroxyl groups on the molecular chain. The relative content of these three functional groups determines the final performance of the material1.

Common characteristics of cellulose esters include:

 Good film-forming and processability

 High transparency and glossiness

 Excellent weather resistance and chemical resistance

 Biodegradability and renewability

 Good compatibility with a variety of plasticizers and resins

 However, different types of cellulose esters exhibit unique properties. Taking CAB as an example, compared with ordinary cellulose acetate, it has lower density, better hydrophobicity and wider solubility range due to the introduction of a larger volume of butyryl groups1. These differences in characteristics make different cellulose esters have their own strengths in application, forming a complementary rather than competitive relationship.

From the perspective of sustainable development, cellulose esters, as one of the representatives of "green chemicals", its raw material cellulose comes from renewable plant resources such as wood and cotton, which gives it special advantages in today's industrial background that emphasizes environmental protection and sustainable development6. With the increasing depletion of petroleum resources and the intensification of environmental problems, the research and development and application of cellulose ester materials are ushering in new development opportunities.

Suppliers of cellulose acetate butyrate

Among them, cellulose acetate butyrate (CAB) is also the main product promoted by iSuoChem at present. It is favored by the market in order to replace the CAB series of EASTMAN! 

Chemical structure and synthesis of cellulose acetate butyrate (CAB)

Cellulose acetate butyrate (CAB) is an important engineering material obtained by chemically modifying natural cellulose, and its molecular structure is complex and delicate. From the chemical essence, CAB is a mixed ester formed by partial replacement of the hydroxyl groups on the glucose ring of cellulose by acetyl (CH₃CO-) and butyryl (C₃H₇CO-). This unique structure gives CAB special properties that are different from other cellulose esters, making it an irreplaceable position in many application fields.

In terms of synthesis mechanism, the industrial production of CAB usually adopts homogeneous or heterogeneous esterification process. In a typical production process, high-purity cellulose raw materials (usually derived from cotton linters or wood pulp) are first activated to increase their reactivity, and then esterified with a mixture of acetic anhydride and butyric anhydride in the presence of catalysts such as sulfuric acid. During the reaction, the hydroxyl groups on the glucose unit of cellulose undergo nucleophilic substitution with the anhydride to form the corresponding ester bond. By precisely controlling the reaction conditions (such as temperature, time, catalyst dosage and anhydride ratio), the content and distribution of different ester groups in the final product can be regulated.

The structural parameters of CAB are usually described by three key indicators:

 Total degree of substitution (DS): indicates the average number of hydroxyl groups substituted on each glucose unit, with a theoretical maximum value of 3

 Acetyl content: affects the melting point, mechanical strength and heat resistance of the material

 Butyryl content: determines the solubility, flexibility and hydrophobicity of the material

Commercial CAB products can be divided into multiple grades according to the butyryl content, which is generally between 17% and 55%. With the increase of butyryl content, the material exhibits lower density, better low-temperature toughness and wider solvent compatibility, but the tensile strength and heat deformation temperature will decrease accordingly.

Post-synthesis treatment of CAB is also crucial. After the reaction is completed, the excess anhydride needs to be removed through a hydrolysis step and the product is neutralized to a stable state. After washing, purification and drying, a CAB product that meets the requirements is finally obtained. It is worth noting that a small amount of unsubstituted hydroxyl groups are usually retained on the CAB molecular chain. These polar groups not only affect the performance of the material itself, but also provide active sites for subsequent chemical modifications (such as cross-linking, grafting, etc.) 2.

Cellulose acetate CA is a more mainstream product on the market. Then, compared with ordinary cellulose acetate (CA), the structural advantages of CAB are mainly reflected in:

Steric hindrance effect of butyryl group: the larger butyryl group increases the molecular chain spacing and reduces the crystallinity, thereby improving the solubility and processability of the material

Enhanced hydrophobicity: the long carbon chain structure of butyryl group gives the material better moisture resistance and water resistance

Internal plasticization: the presence of butyryl group reduces the dependence on external plasticizers and makes the material itself more flexible

The degree of substitution and substituent distribution of CAB can be accurately determined by characterization methods such as nuclear magnetic resonance (NMR), infrared spectroscopy (FTIR) and elemental analysis5. These structural information is of great significance for understanding material properties, guiding process optimization and developing new applications.

In recent years, the green synthesis process of CAB has also made significant progress. A large amount of organic solvents and strong acid catalysts used in traditional methods are gradually replaced by environmentally friendly media such as ionic liquids and supercritical fluids6. These new processes not only reduce environmental pollution, but also improve reaction efficiency and product quality, opening up new ways for the sustainable development of CAB.

Performance characteristics comparison

As a special type of cellulose ester, CAB has the following outstanding properties

Although different types of cellulose esters have similar chemical bases, they exhibit significantly different physical and chemical properties due to differences in substitution groups. A deep understanding of these performance differences is crucial for material selection and engineering applications. This section will systematically compare the performance characteristics of cellulose acetate butyrate (CAB) with other major cellulose esters from multiple dimensions such as thermal properties, mechanical properties, and solubility.

Thermal stability: can be used for a long time at 135°C

The thermal stability of CAB is lower than that of CA, but it still maintains a high level and can be used for a long time at 135°C without destroying its structure19. This thermal stability makes CAB suitable for processing processes that require high temperature treatment, such as injection molding and hot pressing. It is worth noting that the glass transition temperature (Tg) of CAB is usually lower than that of CA, which is related to the internal plasticization effect brought by its larger butyryl group.

Mechanical properties: good balance of strength and flexibility

Comparison of mechanical properties shows that CA has higher stiffness and tensile strength, but greater brittleness; while CAB exhibits excellent flexibility and impact resistance. According to research data, the tensile strength of CAB increases with the increase of acetyl content, while flexibility increases with the decrease of acetyl content within a certain range1.

Solubility: wider solvent compatibility than CA (soluble in alcohols, esters, etc.)

Solubility is a key parameter in the application of cellulose esters. CA is only soluble in a limited number of polar solvents (such as acetone and dimethylformamide), while CAB has a significantly wider solubility range due to the introduction of butyryl groups. As the butyryl content increases, CAB is soluble in a wider range of organic solvents, including alcohols, esters, and certain hydrocarbon solvents1. This excellent solubility gives CAB a clear advantage in coating and ink formulations. Table 1 compares the dissolution behavior of three main cellulose esters in common solvents:

Table 1: Comparison of solubility of different types of cellulose esters

In terms of optical properties, cellulose esters generally have high transparency and low birefringence, making them suitable for optical applications. CAB is particularly outstanding in this regard, with a transmittance of more than 90% and extremely low haze1. In addition, CAB's UV resistance is better than most synthetic polymer materials, and it is not easy to yellow after long-term outdoor use. This feature makes it an ideal choice for high-end outdoor coatings and packaging materials.

Weather resistance and chemical resistance are also important performance indicators of cellulose esters. CAB shows excellent moisture resistance, with a significantly lower water absorption rate than CA, and better dimensional stability in humid environments1. At the same time, CAB has good resistance to oils, weak acids and weak bases, but will hydrolyze under strong acid or strong base conditions. It is worth mentioning that CAB's weather resistance makes it particularly suitable for outdoor applications, such as automotive coatings, building exterior finishes, etc., and can maintain stable appearance and performance for a long time.

In terms of surface properties, CAB exhibits low surface energy, which makes it excellent in anti-sticking and easy to clean. At the same time, the surface of CAB film is smooth and uniform, and a high-gloss coating can be formed5. These characteristics, coupled with its good printability, make CAB popular in the packaging and decoration fields.

It is worth noting that the performance of cellulose esters depends not only on the type of substituents, but also on microstructural parameters such as molecular weight distribution and substituent uniformity. By precisely controlling these parameters, manufacturers can provide customized products that meet specific application requirements. With the advancement of analytical technology and process control, the performance adjustability of cellulose esters will be further improved, creating more opportunities for its application in high value-added fields.

Modification technology of cellulose acetate butyrate (CAB)

Although cellulose acetate butyrate (CAB) itself has many excellent properties, researchers have developed a variety of CAB modification technologies to meet specific application requirements or further improve its performance. These modification methods not only expand the application scope of CAB, but also provide new ideas for the development of high-performance cellulose-based materials. This section will introduce in detail the main modification strategies of CAB and their effects on material properties.

UV curing modification is an important breakthrough in the functionalization of CAB in recent years. Studies have shown that by reacting isocyanates (such as IPDI) and hydroxyethyl methacrylate (HEMA) with CAB, photosensitive double bonds can be introduced to obtain UV-curable CAB2. This modification method makes full use of the reactivity of residual hydroxyl groups on the CAB molecular chain, and gives the material photocuring properties without significantly changing the properties of the matrix. Compared with unmodified CAB, the modified UV-curable CAB has significantly improved film hardness (up to 4H), and significantly improved abrasion resistance, water resistance and solvent resistance2. At the same time, this material maintains good adhesion (grade 1) and high gloss (138), making it very suitable as a high-end decorative and protective coating. The introduction of UV curing technology also enables CAB coatings to be cured within seconds, greatly improving production efficiency and reducing energy consumption.

Cross-linking modification is an effective means to improve the heat resistance and dimensional stability of CAB. The residual hydroxyl groups on the CAB molecular chain can be used to form a three-dimensional network structure with cross-linking agents such as polyisocyanates, epoxy compounds or metal organic frameworks. Moderate cross-linking can significantly increase the heat deformation temperature and reduce the swelling rate of CAB while maintaining its transparency and mechanical strength2. For example, the solvent resistance of CAB film cross-linked with hexamethylene diisocyanate (HDI) is significantly improved, and the dissolution time in acetone is extended from a few minutes to a few hours. This cross-linked CAB is particularly suitable for applications that require chemical resistance, such as chemical equipment linings, anti-corrosion coatings, etc.

Nanocomposite modification is an emerging method to introduce nanomaterials into the CAB matrix to obtain special functions. Commonly used nanomaterials include nanosilver (AgNPs), nanotitanium dioxide (TiO₂), carbon nanotubes (CNTs) and graphene. Studies have shown that the addition of 1-5% nanosilver particles can give CAB long-lasting antibacterial properties, while having little effect on the transparency and mechanical properties of the material. Similarly, CAB films doped with nano-TiO₂ exhibit excellent UV shielding properties and self-cleaning properties, making them suitable for outdoor protective coatings. The key to nanocomposite modification is to achieve uniform dispersion and stable existence of nanoparticles in the matrix, which usually requires surface modification of nanoparticles or the use of dispersing aids.

In practical applications, the above modification technologies are often used in combination to obtain synergistic effects. For example, a multifunctional CAB coating can be prepared by first constructing a cross-linked network through UV curing and then adding nanosilver particles to impart antibacterial properties. The flexible combination of modification technologies provides almost unlimited possibilities for the performance design of CAB.

Application fields of CAB and cellulose esters

Cellulose acetate butyrate (CAB) and its related cellulose esters play an irreplaceable role in many industrial fields due to their unique combination of properties. From daily consumer goods to high-tech products, these renewable materials can be found everywhere. This section will discuss in detail the specific uses and technical advantages of CAB and other cellulose esters in various application fields, and show the broad application prospects of such materials.

The coating and ink industry is one of the most important application fields of CAB. In this field, CAB is mainly used as a film-forming resin and performance modifier, and its advantages are reflected in many aspects15:

Excellent leveling and anti-sagging properties: CAB can effectively control the rheological properties of the coating, ensuring good construction performance and preventing sagging when coating on vertical surfaces

Fast solvent release: The solubility characteristics of CAB enable it to quickly form a stable coating film during solvent evaporation, shortening the drying time

High transparency and gloss: CAB-based coatings can form a highly decorative surface effect

Excellent weather resistance: CAB coatings have good UV resistance and will not turn yellow or powder after long-term outdoor use

It is particularly worth mentioning that CAB occupies an important position in automotive coatings. From primer to topcoat to clearcoat, CAB can be added to each layer of coating to improve performance. Studies have shown that pearlescent coatings with the addition of CAB can produce a unique angular color effect, greatly enhancing the luxury of the car's appearance. UV-cured modified CAB coatings are widely used in high-end electronic products, musical instruments and other fields. Their hardness can reach 4H, and they have excellent wear resistance and gloss retention.

CAB materials are also widely used in the plastics and packaging fields. In this field, CAB can be used as the main matrix resin or as a modified additive for other plastics:

 Tool handles and eyeglass frames: take advantage of CAB's good feel, impact resistance and easy processing

Packaging film: take advantage of CAB's high transparency and moderate air permeability, especially suitable for fresh fruit and vegetable preservation packaging

Cosmetic containers: CAB's excellent surface gloss and chemical resistance make it an ideal choice for high-end cosmetic packaging

Thermoformed sheets: CAB sheets can be vacuum formed into products of various complex shapes

Compared with petroleum-based plastics, the advantages of CAB products are their renewability and biodegradability, which is in line with the sustainable development trend of the modern packaging industry. At the same time, the moisture permeability and air permeability of CAB can be precisely controlled by adjusting the acetyl/butyryl ratio to meet the packaging needs of different products.

It is worth noting that green modification technology has become a research hotspot in recent years. The application of water-based CAB dispersions, bio-based plasticizers, and the development of solvent-free modification processes have made CAB materials more environmentally friendly and sustainable6. These advances are in line with the global sustainable development strategy and will further promote the application of CAB in the field of high-end environmentally friendly materials.

In short, as an important member of the cellulose ester family, CAB has shown broad application prospects in both traditional and emerging fields due to its adjustable structure and performance. Through molecular design and process innovation, this type of renewable material will continue to provide important solutions for sustainable development.