resin bond diamond wheels 36 inch

Properties of resin binder are introduced

Resin binders are used to bond loose abrasives, solidify into a certain shape, and after heating and cementing, they have a certain degree of hardness, strength and grinding performance. The resin binders are composed of binders (resins) and various fillers.

The physical and mechanical properties of the binder are greatly influenced by the type and amount of filler.

Therefore, the type and amount of filler must be chosen reasonably.

Resin bond should have the following properties: good bonding performance, strength of the bond should be high, hardness should be appropriate;

Good heat resistance can improve the grinding efficiency and reduce the surface roughness of the workpiece.

Good economy and environmental protection.

The resin that makes resin abrasive tool commonly is man-made phenolic resin, epoxy resin, polysulfone resin, polyamide.

For the special requirement of quartz grinding tool, mainly phenolic resin, some other resin is added.

Such as phenolic - epoxy resin, phenolic - polyamide.

Phenolic resin

The main raw materials for production are phenol, dimethylphenol, polyphenol, formaldehyde, furfural and other aldehyde, catalyst, such as hydrochloric acid, sulfuric acid, oxalic acid, sodium hydroxide, potassium hydroxide, ammonia, magnesium oxide and so on.

The production process of phenolic resin is as follows:

The polymerization of phenol and aldehyde can be carried out under pressure, atmospheric pressure and decompression.

Usually in acidic or alkaline medium to conduct the normal pressure lock reaction.

Phenolic resin is divided into thermoplastic phenolic resin and thermosetting phenolic resin.

Thermoplastic decentralization refers to a density of 1.18~1.32g/cm3.

Softening point is 85 ~ 110 ℃.

Free phenol mass fraction is 3.5%~7%, white or light yellow translucent solid powder at room temperature, easy to absorb water in the air.

Tree powder does not add hardener, can dissolve in alcohol, butanol, acetone and other solvents.

Under the effect of hardener, the resin can be changed into thermosetting by heating.

The softening point of thermoplastic phenolic resin makes its abrasives have high tensile strength.

The degree of softening point has no obvious influence on the hardness of abrasive tool, but it has great influence on the feasibility of manufacturing process of abrasive tool.

Low softening point (85 ℃), the tree powder is used adhesion, easy to agglomerate, easy cause forming materials agglomerate, inconvenience to manufacture.

If the softening point is too high, the forming material plasticity is poor and affects the forming strength of the abrasive tool, especially the thin section grinding wheel.

Most of the sebaceous powder grain belongs to F240 and finer grain, the sebaceous powder grain is too fine and easy to agglomerate, and the forming material is not easy to mix if the grain is too coarse, which affects the hardness and strength of the abrasive tool.

Tree powder easily absorbs water in the air and becomes hard, which brings inconvenience to production and affects the strength and hardness of the grinding tool.

The experiment shows that the hardness of the abrasive test block increased from 0.176% to 4.23%, and the strength decreased by 20%.

Hard thermoplastic phenolic resin (solid) agent is methenamine, and water generated CH2O, formaldehyde and linear resin first in neighboring contrapuntal effect generated hydroxyl methyl of benzene rings, after further polycondensation generated wangzhuang structure, inadequate for the amount of curing agent, resin is not completely, impact strength and hardness of the abrasive, join the amount is too much, redundant curing agent is not combined with tree powder, in the process of hardening of the decomposition of volatile, make the increase in the number of stomata grinding tool, reduce abrasive hardness and strength.

Thermosetting phenolic resin solution is a yellowish to dark brown viscous liquid at room temperature, with density of 1.16 ~ 1.20g /cm3, viscosity of 60~200s (no. 4 cup method), soluble in ethanol, acetone and furfural, and soluble in water after heating.

Its chemistry performance is not stable, room temperature storage, can slowly to polycondensation reaction, viscosity, in 110 ~ 120 ℃ for 2 h, the loss of liquidity, a elastic or brittle material.

Heated to above 230 ℃, the resin liquid start carbonization, the higher the temperature, the deeper the degree of carbonization, when up to 500 ℃, were completely destroyed.

The viscosity of the resin solution is 100-500s (cup method), which is often used as a binding agent. The viscosity is in the range of 30-200s, and the resin solution is often used as a lubricant for tree cosmetics.

The suitable viscosity can obtain the suitable plasticity of the binding agent.

If the viscosity is too low, the forming material has high fluidity, poor plasticity, easy to stick, and the mechanical strength of the abrasive blank is low.

If the viscosity is too high, the forming material is too hard and not easy to be mixed.

It is proved that the viscosity of resin liquid in cup method is 100~500s, the quality is stable and the effect on the hardness of abrasive tool is little.

Thermosetting resin under 180 ℃ temperature, condensation after hardening quality become a solid mass.

The hardness and strength of cerumen abrasive tools are lower when the solid content is low.

The resin liquid binder made of ammonia as catalyst has high bonding strength and good fire resistance.

The bond strength and fire resistance of resin binder made by sodium hydroxide as catalyst are poor.

After curing, phenolic resin bond has high fire resistance and good mechanical properties. However, phenolic hydroxyl and methylene in the structure are easy to be oxidized, so that the heat resistance and oxidation resistance are affected. The presence of methylene makes the bond after curing appear brittle and other weaknesses.

Modification of phenolic resin is adding additives to alter some properties of the resin.

The modified resins include phenol-acetal resins, phenol-epoxy resins, boron phenolic resins and organosilicon modified phenolic resins.

Epoxy resin

A linear polymer formed by the interaction of a polymer containing an epoxy group, or a compound in the reaction that produces an epoxy group, with some of the components containing a reactive hydroxyl group.

There are three types of epoxy resin: glycidyl epoxy resin, epoxidated olefin and new epoxy resin.

The common epoxy resin in China is e-type epoxy resin, which is dialdehyde A type epoxy resin formed by epoxy chloropropane and dialdehyde A (diphenol propane) monomers under the action of alkaline catalyst (NO2OH).

The number of epoxy groups in epoxy resin is an important index.

Epoxy resin pressure is light yellow to amber transparent liquid or solid, soluble in acetone, work overtime, xylene and other organic solution, it is a linear structure, its not fixed, only add hardener make its linear structure/couplet net or shape structure, formation of insoluble substance, with excellent performance, curing performance depends on the type and dosage of curing agent.

Hardener is an important component of epoxy resin bond.

Hardener can be divided into heating hardener and room temperature hardener according to the required temperature.

According to the type of chemical structure, it can be divided into amine hardener, acid anhydride hardener, resin hardener and imidazole hardener.

According to the form of hardener, it can be divided into liquid hardener and solid hardener.

Resins, including polyamide resin, phenolic resin;

Anhydride, including maleic anhydride, phthalic anhydride, phthalic anhydride;

Imidazole, including benzimidazole, 2-ethyl-4 methyl imidazole.

Epoxy adhesives have the following characteristics

1 Strong bonding ability

May bond the metal and the cent metal.

The abrasives with epoxy resin as the binding agent have higher strength than those with phenolic resin.

2 Little shrinkage

Its shrinkage rate is small (about 2%), add a filling agent, its shrinkage rate is only 0.25% ~ 0.25%, small linear expansion coefficient (60 x 10-6 ℃ - 1).

Suitable for manufacturing fine grit and high density grinding tools.

3 Excellent chemical stability

Resistant to organic solvents and chemical reagents.

4 Heat resistance is poor

Epoxy resin abrasive grinding contact zone in the instantaneous temperature can reach 800 ~ 800 ℃, epoxy resin under the effect of grinding heat, prone to coking, lose's ability to keep abrasive, grinding grain early fall off, increase the abrasive wear and tear.

Under the same process conditions, the abrasion of epoxy resin abrasive tool is 3~5 times higher than that of phenolic resin abrasive tool, and the price is expensive. Epoxy resin abrasive tool is not widely used in the manufacturing of abrasive tool, and the common term is honing wheel, fine size polishing wheel, grinding wheel of rotor groove, high-speed abrasive disc and other special abrasive tools.

In addition, the quality of grinding tools can be improved by mixing phenolic - epoxy modified resin with phenolic resin.