Chengdu Qingya paper is engaged in Bamboo and Bagasse pulp raw materials to produce Bamboo Jumbo rolls, Bamboo toilet paper etc control with extraordinary efficiency.
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Chengdu Qingya paper is engaged in Bamboo and Bagasse pulp raw materials to produce Bamboo Jumbo rolls, Bamboo toilet paper etc control with extraordinary efficiency.
Why does a slight change in fiber ratio lead to significant variations in paper strength?
In paper manufacturing processes, many engineers have encountered the following scenario:
• Sudden decrease in tensile strength of paper
• Instability of tear strength
• Paper pages become brittle
• Even the paper breakage rate increased
The first reaction of many people is:
Has the degree of pulping changed?
However, in large-scale production cases, it was found that one of the key factors truly influencing paper strength fluctuations is actually:
The ratio of long fibers to short fibers.
Sometimes, merely adjusting the fiber proportion by 5% to 10% can lead to significant changes in paper strength.
So here's the question:
Why does the fiber ratio have such a significant impact on paper strength?
Today, we will elucidate this issue from the perspective of the microstructure of paper sheets.
I. Long fibers: The "skeletal structure" of paper
In paper structure, long fibers act like the steel skeleton in construction.
It primarily originates from:
• Coniferous wood pulp
• Long fiber chemical pulp
Typical fiber length:
2.5 mm - 4.0 mm
Due to their longer fiber length and higher strength, long fibers interlock within the paper sheet to form a supporting structure. Their primary functions include:
• Improve paper tear strength
• Improve paper tear resistance
• Enhanced paper sheet toughness
• Provide overall structural support
Therefore, in cases requiring high-strength paper types, such as:
• kraft
• Corrugated base paper
• packing paper
A higher proportion of long-fiber pulp is typically used.
However, an excessively high proportion of long fibers may also lead to certain issues, such as:
• Poor paper sheet formation
• Decreased uniformity
• surface asperities
The reason is simple:
The fibers are too long and difficult to disperse uniformly.
II. Short fibers: The "filling structure" of paper
If long fibers serve as the framework,
Short fibers are analogous to cement and mortar in construction.
The short fibers are primarily derived from:
hardwood pulp
Typical fiber length:
0.8 mm - 1.5 mm
Although the individual strength of short fibers is lower than that of long fibers, they possess a significant advantage: abundant quantity and uniform distribution.
Therefore, short fibers can:
• Filling the gaps between long fibers
• Increase the contact area between fibers
• Improve fiber bonding strength
In production, an increase in the proportion of short fibers typically leads to:
• More uniform paper sheet formation
• Smoother surface
• Increased tensile strength
However, if the proportion of short fibers is excessively high, significant issues may also arise:
• Decreased tear strength
• Crisp paper texture
• Reduced paper sheet toughness
The reason is:
Paper sheets lack sufficient structural framework.
III. Optimal Paper Structure: Synergistic Effects of Long and Short Fibers
A paper structure with high true strength and stable performance does not rely solely on a single type of fiber. Instead, it involves:
Synergistic structure of long fibers + short fibers.
In this structure:
Long fibers are responsible for constructing the skeleton
Short fibers are responsible for filling voids while:
Short fibers can also increase the binding points between fibers.
This ultimately leads to the formation of a:
The paper web possesses both strength and dense structure.
This is also the core logic of papermaking pulp design.
IV. Typical Fiber Ratios of Different Paper Types
In actual production, different paper types have significantly varying requirements for the ratio of long to short fibers.
1 Packaging paper / kraft paper
Emphasize high intensity:
Long fiber proportion: 70% -90% Short fiber proportion:
10% - 30%
2 Cultural paper / Printing paper
Emphasize forming and printing adaptability:
Long fiber proportion: 30% -50% Short fiber proportion:
50% - 70%
3 Household Paper
Emphasize softness and water absorption:
Long fiber ratio:
40% -60% short fiber content:
40% - 60%
V. A Real Production Case
A certain packaging paper machine once experienced the following issue:
• Decreased tear strength
• Fluctuations in tensile strength
After investigation, it was found that:
The proportion of broadleaf wood pulp increased from 25% to 35%, representing only a 10% increase.
Results:
The paper tear strength decreased by approximately 15%.
This is the typical impact caused by changes in fiber proportion.
VI. A Essential Principle for Papermaking Engineers
In the paper structure:
Long fibers determine the framework, while short fibers determine the binding. The most ideal structure is:
Long fibers provide support while short fibers fill the spaces, which constitutes the core principle of paper strength formation.
epilogue
Many people think that papermaking is a simple industry.
But in reality:
Paper is a complex fiber engineering material.
The strength of each sheet of paper is essentially:
The result of countless fibers interwoven and combined with each other. One of the most critical factors among them is:
The ratio of long fibers to short fibers.
