Home    Company News    Do you really know about adhesives? A comprehensive introduction to adhesive knowledge（4）

Do you really know about adhesives? A comprehensive introduction to adhesive knowledge（4）

Hits: 771 img

Functions of Softeners

Softeners are essential components of SBS. Their functions include adjusting hardness, fluidity, and reducing costs. Oil - filled SBS makes compounding and processing easier. The most commonly used softener is naphthenic oil. Aromatic oils are deeply colored, toxic, and thus cannot be used. Paraffin oils cannot improve physical properties and may even cause blooming. The domestic Kelamayi KN series of environmentally friendly naphthenic oils (such as KN4010, etc.) are of high quality.

Types of Softeners

According to hydrocarbon composition, they are divided into three categories: paraffin - based, naphthenic - based, and aromatic - based.

Characteristics of Softeners

  1. Paraffin - based rubber oil: It has good oxidation and light stability, but relatively poor emulsification, compatibility, and low - temperature properties.
  2. Naphthenic - based rubber oil: It combines the advantages of paraffin - based and aromatic - based oils. It has moderate emulsification and compatibility, is pollution - free and non - toxic, and has a relatively wide range of applications.
  3. Aromatic - based rubber oil: It has good compatibility, a large filling amount, and a low price. The resulting rubber products have high strength. However, it is deeply colored, highly toxic, and causes significant environmental pollution.

Definition of Plasticizers

Plasticizers are substances that lower the glass transition temperature and melting temperature of high - molecular compounds, improve the brittleness of the adhesive layer, and enhance the melting fluidity.

Functions of Plasticizers

  1. Shield the active groups of high - molecular compounds, weaken the intermolecular forces, and thus reduce the interaction between molecules.
  2. Increase the heat resistance, extensibility, and cold resistance of high - molecular compounds, and reduce their cohesive strength, elastic modulus, and heat resistance.

Selection of Plasticizers

  1. Polarity: The polarity affects the compatibility between the plasticizer and the main material, following the same principle as the action of solvents.
  2. Persistence: Loss due to exudation, migration, and volatilization affects the physical and mechanical properties of the adhesive. Select plasticizers with high boiling points or high molecular weights.
  3. Molecular weight and state: The higher the molecular weight, the better the bonding strength.

Commonly Used Plasticizers

Phthalates, phosphates, adipates, sebacates, etc.

Definition of Fillers

Fillers are solid materials in adhesives that do not react with the matrix but can change its properties and reduce costs.

Commonly Used Fillers are Divided into Organic Fillers and Inorganic Fillers

  • Organic fillers: They improve the brittleness of the resin, have high hygroscopicity, and low heat resistance.
  • Inorganic fillers: They increase the relative density and brittleness of the adhesive, but improve its heat resistance, medium - resistant properties, and shrinkage.

Selection of Fillers

  1. It should be inactive and not react with other components of the adhesive.
  2. It should have good dispersibility and good wettability with the base material.
  3. It should be free of moisture, harmful substances, and oils, and have no hygroscopicity.
  4. The particles should be uniform and non - toxic.
  5. It should have a wide source, be easy to process, and have a low price.
  6. The density of the filler should not differ too much from that of the base material.
  7. The dosage should be appropriate.

Commonly Used Fillers

Silicon dioxide, calcium carbonate, magnesium carbonate, aluminum powder, phenolic resin, etc.

Coupling Agents

Coupling agents are compounds that can generate a certain binding force with both polar and non - polar substances simultaneously. They are characterized by having both polar and non - polar parts in their molecules. Commonly used coupling agents include organic chromium coupling agents, organosilicon coupling agents, and titanate coupling agents. In adhesives, silane coupling agents are commonly used.

Functions of Coupling Agents

  1. Increase the intermolecular forces within the main resin itself and improve the cohesive strength of the adhesive.
  2. Enhance the bond between the resin and the adherend, playing a certain bridging role. Different coupling agents have different reactive groups, and different reactive groups have different effects on the bonding performance.

Initiators

Initiators are substances that can decompose to generate free radicals under certain conditions. Generally, initiators are added to compounds containing unsaturated bonds. Commonly used initiators include benzoyl peroxide, cyclohexanone peroxide, cumene peroxide, azobisisobutyronitrile, etc.

Accelerators (Catalysts)

Accelerators are substances that can lower the decomposition temperature of initiators or accelerate the reaction between curing agents and resin rubbers.

Anti - aging Agents

Anti - aging agents are substances that can delay the aging of high - molecular compounds. For adhesives used under high temperatures and exposure to sunlight, which are prone to aging and deterioration, anti - aging agents are added during adhesive formulation.

Thickeners

Thickeners are substances that increase the viscosity of adhesives with low viscosity.

Polymerization Inhibitors and Stabilizers

Polymerization inhibitors and stabilizers are substances (such as hydroquinone) that prevent or delay the self - cross - linking of polymers and monomers containing unsaturated bonds during storage.

Previous: Do you really know about adhesives? A comprehensive introduction to adhesive knowledge（3）

Next: Can refrigeration extend the shelf life of the adhesive?

Recommend

    Online QQ Service, Click here

    QQ Service

    What's App