The hardness and strength of resin abrasive are the core indicators to measure its performance, which directly affect the processing efficiency and product quality. Its performance is affected by the comprehensive influence of many factors such as raw material characteristics, manufacturing process, environmental conditions, etc.
As a binder, the molecular structure and curing characteristics of resin are the basis for determining the performance of abrasives. Phenolic resin is widely used due to its high bonding strength and good heat resistance, but the free phenol content must be strictly controlled. Too high a content will cause the resin to crack after hardening and reduce the strength. Although epoxy resin has excellent mechanical properties, it is easy to carbonize during high-temperature grinding, and the wear amount is 3-5 times higher than that of phenolic resin. Therefore, it is more suitable for special abrasives such as honing wheels.
The physical properties of abrasives directly affect the mechanical properties of resin abrasives. Corundum abrasives are suitable for high-strength abrasives due to their high hardness and good wear resistance; while SC abrasives are more brittle and need to be combined with more resin to maintain strength. In terms of particle size, fine-grained abrasives require higher bonding dosage (the bonding dosage increases with the increase in particle size), otherwise the strength is easily reduced due to the excessively fine bonding agent bridge. Mixed particle size design can improve strength by optimizing abrasive grading, but it is necessary to avoid uneven distribution of binder due to excessive particle size differences.
The amount and distribution of binder directly affect the bonding strength between abrasive particles. Although excessive binder can improve hardness, it will increase the porosity of the abrasive tool and reduce wear resistance; insufficient amount will not form an effective binder bridge, resulting in insufficient strength. The binder particle size needs to match the abrasive. Too fine will easily agglomerate, and too coarse will cause uneven distribution. For example, the particle size of phenolic resin powder needs to be controlled at 240 mesh, with a fine proportion of more than 80% to ensure full contact of the hardener.
Molding density affects hardness and strength by changing the compactness of the abrasive tool. High molding density can reduce the spacing between abrasive particles and make the binder bridge thicker, thereby improving strength. However, it is necessary to balance the pressing pressure and resin fluidity. Excessive pressing may cause abrasive breakage or resin extrusion. In actual production, performance optimization can be achieved by adjusting the combination of molding density and binder amount (such as high density with less binder, low density with more binder).
Curing temperature, time and heating rate are key process parameters for controlling the performance of resin abrasive. Too high temperature will cause the resin to decompose and carbonize, while too low temperature will cause incomplete curing. For example, the maximum curing temperature of powdered phenolic resin molds is 180-190℃, which needs to be kept warm for less than 7 hours. The heating rate needs to be dynamically adjusted according to the hardness, particle size and specifications of the mold. Fine-grained and high-hardness molds need to be heated slowly to avoid concentrated discharge of volatiles and foaming.
Resin abrasive is sensitive to environmental humidity. High humidity will hinder the curing reaction of the resin and reduce the initial strength. Phenolic resin powder is easy to absorb moisture and agglomerate. When the humidity increases from 0.9% to 1.2%, the pressing strength of the molding material decreases significantly. The humidity of the resin powder (≤0.5%) and the viscosity of the resin liquid (40-200s cup method) need to be controlled during storage to avoid resin aging or performance fluctuations due to long storage time.
The crosslinking density and hardness of the resin can be adjusted by adding curing agents such as urotropine and vulcanizing agents. For example, the amount of hexamethylenetetramine needs to be controlled at 7.5%-10% of the resin mass. Excessive use will cause residual ammonia and form pores. Modification technologies such as rubber modification can reduce the hardness of the resin and improve its toughness, but attention should be paid to the compatibility of the modifier and the resin to avoid strength loss due to poor interface bonding.
The hardness and strength of resin abrasive are the result of the combined effects of material properties, process parameters and environmental conditions. By optimizing the resin type, particle size distribution, binder dosage and distribution, molding process and hardening system, combined with additives and modification technologies, precise control of performance can be achieved to meet the needs of different processing scenarios.
