1. Overview of Maleic Anhydride
Maleic anhydride is a highly reactive unsaturated cyclic anhydride that plays a central role in modern resin and polymer chemistry. Unlike saturated acid anhydrides, maleic anhydride combines anhydride functionality with carbon–carbon unsaturation, which allows it to participate in both esterification and addition reactions.
In industrial practice, maleic anhydride is not simply used to build molecular weight. Instead, it is deliberately introduced to control resin architecture, reactivity and polarity, making it an essential building block in unsaturated polyester resins, alkyd resins and polymer modification systems.
For manufacturers, the selection of maleic anhydride directly influences curing behavior, crosslink density, adhesion performance and chemical resistance of the final product. As a result, consistent quality and predictable reactivity are critical for stable downstream processing.
SNOWHITE CHEMICAL CO., LTD supplies maleic anhydride for industrial applications, focusing on consistent quality, stable reactivity and reliable supply to support continuous production.
Basic Chemical Information
Chemical Name: Maleic Anhydride
Molecular Formula: C₂H₂(CO)₂O
Molecular Weight: 98.06 g/mol
CAS No.: 108-31-6
HS Code: 29171400
Appearance: White to light yellow solid flakes or briquettes
UN No.: 2215
Maleic anhydride is classified as a regulated chemical for transportation. SNOWHITE CHEMICAL CO., LTD provides complete export documentation to support safe and compliant international shipments.
1.1 Physical & Chemical Characteristics
Maleic anhydride exhibits a combination of physical and chemical properties that make it uniquely suited for controlled industrial reactions.
Key characteristics include:
- High electrophilic reactivity due to the anhydride ring
- Presence of a reactive C=C double bond, enabling copolymerization and grafting
- Strong polarity, improving interaction with polar substrates and additives
- Low molecular weight, allowing efficient incorporation into polymer backbones
- Predictable melting behavior, facilitating solid handling and melt processing
From a processing perspective, maleic anhydride reacts readily with alcohols, glycols and amines, forming esters or amide structures while retaining unsaturation when required. This dual-reactivity
1.2 Functional Behavior & Reaction Mechanism
The functional behavior of maleic anhydride is primarily governed by its cyclic anhydride structure and conjugated double bond.
Esterification Mechanism
During esterification with polyols, maleic anhydride opens its anhydride ring to form mono- or di-ester structures. This reaction introduces:
- Reactive ester linkages
- Residual unsaturation for further crosslinking
- Increased polarity within the polymer chain
In unsaturated polyester resin systems, this unsaturation later participates in free-radical crosslinking reactions, forming a three-dimensional network structure after curing.
Copolymerization and Grafting Behavior
Maleic anhydride can also undergo copolymerization or grafting reactions with polymers such as polyethylene, polypropylene and styrenic systems. In these cases, maleic anhydride acts as a functional modifier, introducing polar groups into otherwise non-polar polymer backbones.
This modification improves:
Interfacial adhesion
Compatibility between polymer blends
Dispersion of fillers and reinforcements
1.2.1 Practical Advantages in Industrial Formulations
From a formulation and production standpoint, the functional behavior of maleic anhydride translates into several practical advantages:
- Controlled curing speed: Unsaturation allows formulators to fine-tune gel time and curing profile
- Improved adhesion: Increased polarity enhances bonding to glass fiber, metals and mineral fillers
- Better mechanical properties: Optimized crosslink density improves strength and toughness
- Enhanced chemical resistance: Ester structures improve resistance to solvents and chemicals
- Improved compatibility: Helps bridge polar and non-polar components in composite systems
This is why maleic anhydride is often preferred over saturated anhydrides when both reactivity and performance optimization are required.
2. Major Applications of Maleic Anhydride
2.1 Unsaturated Polyester Resins (UPR)
In unsaturated polyester resin (UPR) production, maleic anhydride serves as the primary source of unsaturation within the polymer backbone.
By reacting with glycols, maleic anhydride introduces double bonds that later participate in crosslinking with styrene or other reactive diluents. This crosslinked network structure is responsible for:
- High mechanical strength
- Dimensional stability
- Good thermal and chemical resistance
Proper control of maleic anhydride content allows resin manufacturers to balance processability, curing speed and final performance.
2.2 Alkyd Resins & Surface Coatings
In alkyd resin production, maleic anhydride is used to:
- Modify resin structure
- Improve drying speed
- Enhance hardness and adhesion
These properties are important for industrial coatings, protective paints and metal surface treatments.
2.3 Polymer Modification & Copolymers
In polymer modification, maleic anhydride is widely used as a compatibilizing agent rather than a simple monomer.
When grafted onto polymer chains, maleic anhydride introduces reactive polar sites that improve interaction with fillers, fibers or other polymers. This is especially important in:
- Glass-fiber reinforced plastics
- Polymer blends
- Composite materials
As a result, products show improved mechanical integrity and reduced phase separation.
2.4 Chemical Intermediates
Maleic anhydride serves as an intermediate in the production of:
- Fumaric acid
- Malic acid
- Lubricant additives
- Agricultural and specialty chemicals
Stable quality and consistent reactivity are critical for these downstream processes.
3. Quality Control & Handling Considerations
Maleic anhydride requires careful quality control and handling due to its reactive nature. SNOWHITE CHEMICAL CO., LTD focuses on:
- Consistent purity and low impurity levels
- Controlled solid form and particle size
- Stable batch-to-batch performance
- Clear handling and storage guidance
Proper storage and moisture control help maintain product performance during transportation and use.
4. Packaging & Storage
4.1 Packaging Options
25 kg bags
500 kg or 1000 kg jumbo bags
Customized packaging upon request
4.2 Storage Recommendations
Store in a cool, dry and well-ventilated area
Avoid moisture and direct heat
Keep containers tightly sealed
Under recommended conditions, maleic anhydride maintains stable quality during storage.
5. Supply & Technical Support from SNOWHITE CHEMICAL CO., LTD
SNOWHITE CHEMICAL CO., LTD provides reliable supply and technical support for maleic anhydride, including:
Stable production and export capacity
Consistent quality control systems
COA, SDS and transport documentation
Technical support for application and handling
With experience supplying global resin and chemical manufacturers, SNOWHITE CHEMICAL CO., LTD is recognized as a dependable supplier of maleic anhydride.
