Composition And Formulation Of Rubber Pressure Sensitive Adhesive

Rubber is the main component. It gives the pressure sensitive adhesive enough cohesive strength. The tackifier can make the pressure sensitive adhesive have certain adhesion. The softener is used to reduce the bulk viscosity of the pressure sensitive adhesive and improve the initial viscosity at low temperature.

Rubber type pressure sensitive adhesive can be made into solvent, water emulsion and solvent free (mainly calendering type). Solvent based rubber pressure sensitive adhesive is still used more and more importantly.

Actually used as rubber elastomers are natural rubber and some synthetic rubber, such as natural rubber, styrene butadiene rubber, polyisobutylene, butyl rubber, cis 1, 4- polyisoprene rubber, butadiene rubber, and their reclaimed rubber, as well as natural rubber latex, styrene butadiene latex and so on.

Natural rubber has high average molecular weight and crystallinity, and its cohesive strength is large. The pressure sensitive adhesive prepared has good adhesion.

Natural rubber has low glass pition temperature and good elasticity in wide temperature range (-70~1300C). Therefore, the pressure sensitive adhesive is soft, elastic, low temperature, natural rubber is small, easy to mix with non-polar tacky resin. The pressure sensitive adhesive has low surface energy, easy to wet the solid surface, and therefore initial viscosity and adhesion are good. It is the most ideal elastomer for rubber pressure sensitive adhesive.

Because natural rubber molecules contain a large number of unsaturated double bonds, their weathering resistance is poor, and their resistance to oil and organic solvents is poor.

The compatibility of styrene butadiene rubber with tackifier is not as good as that of natural rubber, and its adhesive property is not as good as natural rubber. It has good aging resistance, low water absorbency, low oil resistance, oil resistance, plasticizer and low price. Therefore, it is often used in combination with natural rubber to prepare pressure sensitive adhesive with good water resistance, aging resistance and oil resistance.

Ding Ji rubber preserves the advantages of polyisohexenes, but double bonds are added to the molecules, which can be crosslinked by sulfuration.

In addition, halogenated butyl rubber and partially vulcanized butyl rubber can also be used to prepare pressure sensitive adhesives. However, because of their high viscosity, adhesive force and cohesive force, it is difficult to achieve a high level of balance. Therefore, they can not be used for general pressure sensitive adhesive, and can only be used for manufacturing metal pressure protection and anti-corrosion products.

When the tackifier and the rubber are used properly, the tackifier can be well dispersed in the rubber phase. At this time, the initial adhesion force reaches the maximum value and the performance is optimal. If the resin dosage is too large, a sharp phase change will take place, so that the resin will be pformed into a continuous phase while the rubber phase pformation will be dispersed phase. The adhesive layer will lose its initial adhesive force (the adhesion between the adhesive and the adhesive material after the adhesion (0.2~10S or 5~10min) will decrease).

The viewpoint of two phase morphology can not fully prove the essence of the change of initial adhesive force with the increase of viscosity to the amount of lipid. It is explained from the point of view of viscoelasticity of polymers. No matter whether phase separation occurs, the viscosity of rubber phase is the main reason for the increase of initial viscosity due to the dissolution of resin.

With the increase of resin usage, the viscosity of the system decreases and the initial adhesive force increases.

The lower the softening point of the resin is, the smaller the minimum viscosity is, and the higher the initial viscosity is, the greater the amount of resin needed to reach a minimum viscosity.

The addition of tacky resin reduces the elastic modulus of the pressure sensitive adhesive, changes the viscoelasticity, increases the viscosity, and increases the initial adhesive force, which is a scientific and more thorough explanation of the essence of the viscosity increasing effect.

The effect of tackifier mainly refers to the effect of the tackifier on the pressure sensitive adhesive properties of the adhesive, namely initial adhesion, 1800C peel strength and adhesion, and the balance between them.

The better the three physical properties, the better the tackifier effect.

As the amount of softener increases, the initial adhesive force first increases and then decreases, so that the holding force decreases significantly and the 1800C peel strength decreases.

Commonly used softeners are oils, including mineral oils and vegetable oils, such as pformer oil, Vaseline, naphthenic oil, lanolin, stearic acid, (sesame oil), glycerin, liquid paraffin, etc.

Mineral oil has good softening effect and low price. Naphthenic oil has better comprehensive properties and uses more liquid rubber and resin, such as low molecular weight polyisobutylene, polybutene, liquid polyisoprene, depolymerization rubber, liquid terpene resin, liquid ancient Malone resin, etc.

Because the relative molecular mass is larger than that of the oil, its softening effect is relatively small, but it has a certain viscosity increasing effect.

Synthetic plasticizers, such as dibutyl phthalate, octyl phthalate two, and Trimethylphenol phosphate, have good compatibility with rubber, and their softening effect is obvious, and they are colorless and pparent. They are especially suitable for producing light color pparent pressure sensitive adhesive products.

Commonly used antioxidants are 264, antioxidant D, antioxidant MB UV absorber and so on.

It is important to note that some antioxidants are polluting (such as antioxidant D), and some antioxidants are vulcanized (MB). The dosage of antioxidants is generally 0.5~2.0.

Using pigments and fillers can generally increase cohesive force of pressure sensitive adhesives more or less, but at the same time reduce initial adhesion and peel force. The choice of pigments and fillers must pay attention to particle size, shape, water content, acid-base and the effect of specific surface on pressure-sensitive adhesive.