Acryl

2025.03.23

What is acrylic resin?

Acrylic resin is a general term for synthetic resins that are mainly made from acrylic acid monomers or methacrylic acid monomers. It is used for a variety of purposes because it has excellent transparency, light resistance, durability, and processability.

  • Transparency
    It has high transparency like glass and excellent light transmittance. It does not absorb UV rays easily and does not yellow even with long-term use.
  • Light resistance
    Suitable for outdoor use, it is resistant to deterioration caused by UV rays, rain and wind.
  • Impact resistance
    It is more resistant to impacts and less likely to break than glass, but it can be a little more brittle than other plastics (e.g. polycarbonate).
  • Processability
    It is a thermoplastic resin, so it can be bent and shaped by applying heat. It is also relatively easy to cut and glue.
  • Light weight
    It is lighter than glass and easier to handle.

Applications of acrylic resin

Due to their excellent properties, acrylic resins are widely used in the following applications:

  • Everyday items: signs, displays, lighting covers, furniture
  • Construction and decoration: Replacement for window glass, wall materials, interior decoration
  • Industrial parts: Auto parts, aircraft windows
  • Medical: Dental materials, dentures, transparent parts for medical devices
  • Other: Artworks, accessories, model making

Acrylic resin design

The polymerization method for acrylic resin is achieved by radical polymerization. It is a type of polymerization reaction in which free radicals generated by an initiator are used to bond monomers to form a polymer. This method is widely used, especially for the polymerization of vinyl and acrylic monomers, and plays an important role in the production of many synthetic materials such as plastics and resins. Radical polymerization proceeds in the following three stages:

Reaction mechanism of radical polymerization

  1. Initiation reaction
    Radical polymerization begins with the generation of free radicals. Typically, radicals are generated by the application of heat, light, or the decomposition of peroxides or azo compounds. These radicals react with double bonds in monomer molecules to initiate the polymerization reaction.
    For example, in the decomposition of benzoyl peroxide:

    　　　　　　　　　　　　　　 　Heat or Light
    　C6H5-C(O)-O-O-C(O)-C6H5　　　　→　　　　2C6H5CO・
  2. Growth reaction
    A radical reacts with a monomer to produce a new radical, which then reacts with another monomer to grow a polymer chain. This process proceeds as a chain reaction.
    For example, in the propagation reaction of styrene:

    　R・　+　CH2＝CHC6H5　→　R-CH2CH・C6H5
  3. Termination reaction
    A polymerization reaction is terminated by the disappearance of the radicals. There are two main types of termination reactions:
    ✓Recombination: Two radicals combine to terminate a polymer chain.
    ✓Disproportionation: Hydrogen transfer from one radical produces two polymer chains.

    　R-CH2CH・C6H5　+　R’・　→　R-CH2CHC6H5-R’

Types of radical polymerization

  1. Chain (continuous) polymerization: The most common form of radical polymerization.
    A radical initiator adds to a monomer, and the resulting active species incorporates monomers one after another, causing the polymerization to proceed.
    Example: Polymerization of styrene and methyl methacrylate.
  2. Main polymerization (bulk polymerization): Polymerization that uses only monomers as the reaction system.
    When an initiator is added and heated, the monomers themselves polymerize, producing a polymer.
    Examples: Polystyrene (PS), Polymethyl methacrylate (PMMA).
  3. Solution polymerization: A method in which a monomer is dissolved in a solvent and an initiator is added to cause a reaction.
    Since the reaction heat is absorbed by the solvent, temperature control is easy.
    Example: Polymer synthesis for paints and adhesives.
  4. Suspension polymerization: A method in which monomers are dispersed in water and polymerization is carried out while stirring.
    By using a water-insoluble initiator, the polymerization proceeds within the monomer particles.
    Examples: Polystyrene (PS), Polyvinyl chloride (PVC).
  5. Emulsion polymerization
    A surfactant is used to trap the monomers inside tiny micelles, and polymerization is then carried out using a radical initiator.
    This results in a polymer with a very small particle size, forming a polymer latex.
    Examples: synthetic rubber (SBR), acrylic resin.
  6. Living radical polymerization (controlled radical polymerization): A method that makes it possible to adjust molecular weight and molecular weight distribution by controlling the growth of radical polymerization.
    Main methods
    ・ATRP（Atom Ttransfer Radical Polymerization）
    ・RAFT（Reversible Addition-Fragmentation chain Transfer polymerization）
    ・NMP（Nitroxide-Mediated radical Polymerization）
    Example: Synthesis of block copolymers, development of high-performance materials.

Selection of radical polymerization monomers

There are various types of acrylic resin monomers, each with different characteristics.
We will introduce the main types and major manufacturers.

Major types of radical polymerization monomers

  1. Methacrylate Esters
    ・Methyl methacrylate（MMA）：It has a high transparency and Light resistance and is a major component of acrylic resin.
    ・Ethyl Methacrylate（EMA）：More flexible than MMA. Used in paints and adhesives.
    ・Butyl Methacrylate（BMA）：Highly flexible. Used in paint and coating applications.
    ・Hydroxyethyl Methacrylate（HEMA）：Provides hydrophilicity.
    ・Hydroxypropyl Methacrylate（HPMA）：It has similar properties to HEMA and is widely used in the medical and paint industries.
  2. Acrylate Esters
    ・Methyl acrylate（MA）：More reactive than MMA. Used in paints and adhesives.
    ・Ethyl Acrylate（EA）：Used as an additive to increase flexibility.
    ・Butyl Acrylate（BA）：Has low temperature flexibility. Used for paints, adhesives and elastomers.
    ・2-Ethylhexyl acrylate（2-EHA）：Has the effect of increasing flexibility and is used in paints and adhesives.
  3. Special acrylic monomer
    ・Glycidyl Methacrylate（GMA）：It has epoxy groups, which improve adhesion and chemical resistance.
    ・Carboxyethyl Acrylate（CEA）：It is polar and highly hydrophilic.
    ・N-Butylmethacrylamide（BMAA）：Has high heat resistance.

Major radical polymerization monomer suppliers

Japanese supplier

  • Mitsubishi Chemical（MMA, EMA, BMA, etc.）
  • Sumitomo chemical（Acrylic esters, special acrylates）
  • Kuraray（HEMA, GMA, etc.）
  • Showa Denko (Resonac) (MMA, special acrylate)
  • Asahi Kasei (MMA, BA, etc.)
  • Osaka Organic Chemical Industry (acrylic esters, etc.)
  • Shin-Nakamura Chemical Industry (acrylic esters, etc.)

Overseas suppliers

  • BASF（Germany）（MMA, BA, 2-EHA, etc.）
  • Evonik (Germany) (HEMA, HPMA, GMA, etc.)
  • Arkema (France) (MMA, specialty acrylates)
  • Dow (USA) (Acrylate ester type)
  • Mitsubishi Chemical America (MMA)

Selection of radical polymerization initiator

Radical polymerization initiators are classified according to their ease of decomposition and applicable temperature.
・Peroxide-based compounds (BPO, DCP) are versatile and are particularly effective when using thermal decomposition.

・Azo compound-based compounds (AIBN, ACHN) decompose at relatively low temperatures and promote stable polymerization reactions.

・Photoinitiators (BEE, TPO) are used for UV-curing resins.

・Major manufacturers include NOF, AkzoNobel, Arkema, Nouryon, BASF, etc.


1. Peroxides
　 Peroxides are common initiators that generate radicals through thermal or photolytic decomposition.

InitiatorDecomposition temperature（℃）ApplicationSupplier
Benzoyl peroxide（BPO）60-80Acrylic resin, polyester resinNOF、AkzoNobel, Arkema
Dicumyl peroxide（DCP）120-150Cross-linked polyethylene, rubberNouryon, NOF
Lauroyl peroxide（LPO）60-80Vinyl monomer polymerizationAkzoNobel, NOF
Methyl ethyl ketone peroxide（MEKP）60-80Unsaturated polyester resinArkema, NOF


2. Azo Initiators
　 Azo compounds decompose by releasing nitrogen gas, generating stable radicals.

InitiatorDecomposition temperature（℃）ApplicationSupplier
Azobisisobutyronitrile（AIBN）60-80Acrylic polymerization, latex polymerizationFUJIFILM Wako, NOF, DuPont
Azobiscyclohexanecarbonitrile（ACHN）100-120High temperature polymerizationNOF, FUJIFILM Wako
Azobisdimethylvaleronitrile（ABVN）50-80Low temperature polymerizationNOF, AkzoNobel


2. Other initiators
　 There are also special initiators available for specific applications.

InitiatorDecomposition temperature（℃）ApplicationSupplier
Pyrocarbonate（TPC）80-150PVC, polyethyleneArkema, NOF
Hydroperoxides（TBHP）100-150Radical polymerization, oxidation catalystArkema, NOF
Benzoin Ethyl Ether（BEE）UVPhotoinitiator (UV curable resin)BASF, IGM Resins
Ethylphenyl(2,4,6-trimethylbenzoyl)phosphine oxide（TPO）UV
350～420 nm		UV-curable adhesives, 3D printing, UV-curable resins (coatings and paints)IGM, BASF, Lambson, Tianjin Jiuri

Major radical polymerization initiator suppliers

Japanese supplier
・NOF (Nippon Oil & Fats): Major supplier of peroxides and azo compounds
・FUJIFILM Wako (formerly Wako Pure Chemicals): Research chemicals
・ADEKA: Special initiators
・Sumitomo Chemical: For functional polymers

Overseas suppliers
・AkzoNobel (Netherlands): One of the world’s largest peroxide manufacturers
・Arkema (France): A leading company in organic peroxides
・Nouryon (Netherlands) (formerly AkzoNobel Specialty Chemicals): Supplier of peroxides and azo compounds
・BASF (Germany): Photoinitiators, functional monomers

Acrylic resin manufacturing method

Continuous Solution Polymerization

This method involves polymerizing monomers (such as MMA) in an organic solvent to obtain polymers in solution form, which is suitable for applications such as paints and adhesives.

＜Process＞

  1. Mix monomer (MMA) and solvent and add initiator (AIBN, etc.)
  2. Supply to a continuous reactor (tube reactor, etc.) and maintain temperature at 80-120°C
  3. The reaction proceeds and polymer is produced (solution state)
  4. The solvent is evaporated or diluted to produce the final product

Continuous Suspension Polymerization

The monomer is dispersed as droplets in water and polymerized to produce granular (bead-like) acrylic resin, which is used as an injection molding material, etc.

＜Process＞

  1. Monomer (MMA), suspending agent (PVA, etc.), and initiator (benzoyl peroxide) are dispersed in water
  2. The mixture is heated to 80-90°C in a continuous stirring reactor (CSTR, etc.) to initiate polymerization
  3. The grown polymer particles are filtered, dried, and washed
  4. The resulting granular polymer is pelletized and supplied for injection molding

Continuous Emulsion Polymerization

This method involves polymerization in an aqueous emulsion (aqueous dispersion system using an emulsifier), and is suitable for applications such as acrylic paints, coatings, and adhesives.

＜Process＞

  1. Monomer (e.g. MMA), water, emulsifier (surfactant), and initiator are mixed
  2. The polymerization is started by heating in a continuous flow reactor (e.g. tube reactor)
  3. Nano-sized polymer particles are generated and dispersed as an emulsion
  4. The product can be used as is or concentrated.

Continuous Gas-Phase Polymerization

This is a method of polymerizing monomers in the gas phase to obtain powdered acrylic resin, and is a special manufacturing process for obtaining high-purity acrylic powder.

＜Process＞

  1. Monomer (MMA) is supplied into the gas phase
  2. Radical initiator is added and the reaction temperature is controlled (150-200°C)
  3. Polymerized polymer is precipitated as a fine powder
  4. Filtered and dried, and supplied as the final product

Batch Bulk Polymerization

The batch method is a method of forming material into sheets or blocks using a metal mold (cast mold).

＜Process＞

  1. Mix monomer (MMA) and initiator (benzoyl peroxide, BPO, etc.)
  2. Remove air bubbles by degassing (vacuum degassing)
  3. Pour into a cast mold
  4. Heat and polymerize in a polymerization furnace (60-100°C) for several hours to several days
  5. Slowly cool to remove internal stress (annealing)

Continuous bulk polymerization (cast method)

This is a method of polymerization that proceeds continuously rather than batchwise. It is suitable for mass production of large acrylic sheets (cast plates).

＜Process＞

  1. Mix monomer (MMA) and initiator
  2. Degassing process
  3. Pour between two glass plates and shape into a sheet
  4. Polymerize in a continuous heating furnace (heating steps are adjusted stepwise)
  5. Cool and perform stress relief process (annealing)
  6. Finishing (cutting and polishing)

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