Liaoning Xinda Talc Group Co., Ltd. -- Cao Xinyu

In the previous chapter, we analyzed that magnesite impurities are the fundamental cause of abrasion generated by talc from the perspectives of mineral structure, hardness and paragenetic characteristics. In this chapter, combined with measured data from Liaoning Xinda Talc Group, we quantitatively analyze the variation law of abrasion value of talc powder with different grades, and unpack the structure-activity relationship among the three factors: talc content, magnesite proportion and abrasion value.

1. Definition and General Standards of Abrasion Value in the Paper Industry

In the papermaking field, abrasion value refers to the mass of abrasion caused by filler suspension on a test substrate under standard conditions, measured in mg. It serves as the core indicator for judging the "abrasive aggressiveness" of fillers and directly determines the service life of forming fabrics.

Per general industrial standards, qualified talc powder for papermaking must have an abrasion value below 10 mg. This threshold is an engineering standard formulated backward based on the operating conditions of high-speed paper machines and equipment service life.

2. Measured Abrasion Value Results of Talc Powder in Three Grades

The research team classified talc samples from Haicheng into high, medium and low grades by talc content. All indicators and abrasion performance are shown as follows:

 High-Grade Talc (Talc Content: 92%~95%, Magnesite Content: 3%~5%)Produced by the combined purification process of flotation and electrostatic separation, with brightness ranging from 87 to 90 and residue on 325-mesh sieve ≤0.5%.Measured abrasion value: 6~10 mg, fully complying with the standard for premium-grade papermaking talc.

Field application data: When used on high-speed paper machines, the continuous service life of forming fabrics can reach 60 to 90 days.Medium-Grade Talc (Talc Content: 78%~88%, Magnesite Conten（8%~15%)Manufactured via single flotation or hand sorting plus crushing processes, with brightness ranging from 82 to 86.Measured abrasion value: 15~25 mg, exceeding the industrial qualified threshold of 10 mg.Field application data: The abrasion rate of forming fabrics rises by 40%~60% compared with that of high-grade talc.

Low-Grade Talc (Talc Content: 60%~72%, Magnesite Content: 18%~30%)Only subjected to simple crushing and classification, and mixed with small amounts of impurities including dolomite and quartz, with brightness ranging from 75 to 80.Measured abrasion value: 30~45 mg, featuring extremely strong abrasiveness.Field application suggestion: Not recommended for use as papermaking filler, as it will drastically shorten equipment service life.

The overall data shows an obvious rule: the higher the talc content and the fewer magnesite impurities, the lower the abrasion value, presenting a strong negative correlation between the two (correlation coefficient R²＞0.90).

3. Three Core Mechanisms Through Which Grade Affects Abrasion Value

 Concentration Effect of Hard ParticlesAccording to the abrasive wear theory, abrasion loss is positively correlated with the quantity of hard particles. As hard abrasive grains, magnesite continuously scours forming fabrics in high-speed flowing pulp. The higher the magnesite content, the more particles participating in abrasion and the greater the cumulative abrasion loss.

Synergistic Amplification Effect of Soft and Hard ParticlesFlaky talc particles can form a lubricating buffer layer to weaken the abrasive effect of magnesite. When the magnesite proportion exceeds the critical value of 10%~12%, the lubricating effect of talc is greatly diluted, and the abrasion value surges sharply instead of rising linearly. Meanwhile, angular magnesite particles cause stress concentration, further amplifying abrasion efficiency.

 Additional Influence of Particle SizeHard magnesite is difficult to crush, so low-grade talc often retains coarse particles of 20~30 μm; in contrast, high-grade talc boasts uniform particle size distribution (D90 controlled at 10~15 μm). Large-sized hard particles contribute far more to equipment abrasion than their own mass proportion.

Brief summary: The combined effects of magnesite content, particle morphology and particle size ultimately determine the abrasion level of talc powder.

Preview of Next Chapter: How high-abrasion fillers damage forming fabrics, paper cutters and pulp refining equipment step by step, with practical industrial selection and control suggestions attached.