Fiber Percentage Calculation for PC and CVC Fabrics: Easy 5 Step

Introduction

Are you searching for a fiber percentage calculation? Yes, you are in the right place. Knowing the fiber composition is crucial for a textile engineer, especially when working with blended fabrics like PC and CVC fabrics. Blended fabrics like PC (polyester-cotton) and CVC (chief value cotton) are commonly used in the textile industry.

It is much more difficult to deal with PC and CVC fabric orders without knowing their fiber percentage. Understanding the fiber composition and fiber percentage is essential for dyeing, finishing, costing, and quality control. This article aims to explain a simple method to calculate the fiber percentage for PC and CVC fabrics. Before going to the main topic, let’s learn what PC and CVC fabrics are.

• PC Fabric: PC fabric refers to polyester-cotton fabric. A blended fabric where the polyester fiber percentage is more than the cotton fiber percentage is called PC fabric. To illustrate, 65% polyester fiber + 35% cotton fiber= PC fabric
• CVC Fabric: CVC fabric refers to the chief value of cotton. A blended fabric where the cotton fiber percentage is more than the polyester fiber percentage is called CVC fabric. To cite an example: 65% Cotton fiber + 35% polyester fiber CVC fabric.

Why is it necessary to Calculate Fiber Percentage?

Fiber percentage calculation is the most important. Knowing the exact fiber ratio of a fabric helps to make various decisions. Such as:

1. Accurate fiber percentage helps to select the right dyeing process.
2. It helps to avoid extra fabric costs.
3. It also helps to reduce shrinkage percentage as well as the colorfastness properties of a fabric.
4. The exact fiber percentage helps to make the right cost.
5. Finally, it helps to fulfill the buyer’s requirements.

That’s why calculating the fiber percentage is necessary.

Formula for Calculate Fiber Percentage

• Individual fiber weight = Before treatment weight – after treatment weight
• Fiber percentage= (individual fiber weight ÷ Total fabric weight) × 100

Required Chemical for Fiber Percentage Calculation

• N-dimethylformamide- 100 ml/1gm thread
• Sulfuric Acid (70%)- 100 ml/1 gm thread

How to Dilute Sulfuric Acid from 98% to 70%

Let’s assume there is 98% sulfuric acid in the lab. If you need to dilute the sulfuric acid from 98% to 70%, you can use the following formula. Let’s prepare a solution of 500 ml.

• Required sulfuric acid= Total required solution× (Required percentage ÷ Present percentage)
• Required sulfuric acid= 500 × (70% ÷ 98%)= 357 ml
• Required water= 500 – 357= 143 ml

Fiber Percentage Calculation Step

This article shows you how to calculate the fiber percentage of a blended fabric, particularly cotton, polyester, and spandex fibers, step by step with an example.

• Step-1: Initially, identify which thread (warp or weft) contains spandex. You can do this by untwisting the thread and observing the presence of spandex threads.
• Step-2: Now, cut a fabric sample 6 inch² from the buyer supplied sample.
• Step-3: Then, weight (W₁) the fabric (6 inch² ) and note down the wight. Now, separate its warp and weft thread. Again, weigh the warp (W₂) and weft (W₃) threads separately. You must note down every weight.
• Step-4: Subsequently, the thread that contains spandex (usually the weft thread contains spandex) is stirred with N-dimethylformamide at 90⁰C for 10 minutes. Use 100 ml N-dimethylformamide per 1 gm thread. After stirring, wash the thread with distilled water. Then, filter the solution to separate the thread from the water. Finally, dry the thread to remove extra water. After drying, again weigh (W₄) the thread and note down the weight. Now, Calculate the amount of spandex from the different weights of before treatment and after treatment.  
• Step-5: Next, the residual thread is treated with 70% sulfuric acid at room temperature for 10 minutes. Use an Amount of sulfuric 100 ml per 1 gm thread.  Sulfuric acid removes the cotton. Now, wash the thread with distilled water and neutralize the acid by using soda ash (1gm/100ml). Then dry the thread. After drying, again weigh the thread and calculate the amount of cotton in the threat. The remaining weight represents the polyester content.  

Let’s clarify the concept with an example:

• Total weight of the fabric (W₁) =1.75 gm
• Weight of warp thread (W₂) and weft thread(W₃)   is 1.15 gm and 0.6 gm respectively.
• Initially, let’s work with weft thread.
• Stirred the weft thread with N-dimethyl formamide (as weft thread contains spandex) at 90⁰ C for 10 min and dryer.
• Weight of weft thread (W₄) after treatment with N-dimethylformamide is 0.55 gm
• Amount of spandex= Before treatment(W₃)  – after treatment (W₄) = 0.6 – 0.55= 0.05 gm
• Percentage of the spandex= (0.05×100) ÷ 1.75= 2.86% or about 3%
• Now, the remaining weft thread (W₄) is again treated with 70% sulfuric acid. After 10 minutes, rinse the thread with distilled water and neutralize the acid by using soda ash. Now dry the weft thread. The cotton part dissolves in sulfuric acid. The remaining part is polyester. After drying, weigh the weft thread again and find the weight of the weft thread (W₅)  is 0.45 gm. So, the amount of the polyester is 0.45 gm as cotton dissolves in acid.
• Percentage of polyester fiber in weft thread= (0.45×100)÷1.75= 25.71%
• Amount of cotton fiber in weft thread= Before treatment(W₄)  – after treatment(W₅)  = 0.55 – 0.45= 0.1 gm
• Percentage of the cotton thread in weft thread= (0.1×100)÷ 1.75= 5.71%
• Now, let’s work with warp thread.
• Warp thread is treated with 70% sulfuric acid at room temperature for 10 min. As a result, the cotton part will dissolve in the acid. After treating, rinse the warp thread with distilled water and neutralize by using soda ash. Now dry the warp thread. After drying weigh the warp thread and find weight of the warp thread (W₆) is 0.1 gm. This is the weight of polyester thread. Because the cotton part totally dissolves in acid.
• So, Percentage of polyester in warp thread= (0.1×100) ÷1.75= 5.71%
•  Amount of cotton thread= before treatment (W₂) – after treatment (W₆) = 1.15-0.1=1.05
• Percentage of cotton fiber= (1.05×100) ÷1.75= 60%
• Total percentage of cotton = weft + warp= 5.71% + 60%= 65.71% or about 66%
• Total percentage of polyester= Weft + Warp= 25.71% + 5.71%= 31.42% or about 31%
• Finally, it is clear that the fabric was CVC fabric and contained 66% cotton fiber, 31% polyester fiber, and 3% spandex.

N.B.: Same way, you can calculate fiber percentage from PC fabric. But remember always dry the fabric before weighing to avoid moisture errors and use precise lab electric balance.

FAQs

1. what is the difference between PC and CVC fabric?

The basic difference between PC and CVC fabric is that PC (polyester-cotton) fabric contains more polyester than cotton, while CVC (Chief value of cotton) fabric contains higher amount of cotton fiber than polyester. To cite an example:  PC Fabric (60% polyester 40% cotton), CVC fabric ( 60% cotton 40% polyester)

2. Why is fiber percentage calculation important?

Calculation of fiber percentage is crucial because accurate fiber percentage calculation ensures the quality of the produce as well as the correct processing methods. Additionally, fiber affects dyeing, cost, hand feel of fabric, shrinkage percentage, and overall performance of the fabric. So, it is important to know fiber percentage calculation to calculate accurately.

3. How can I identify whether the warp or weft contains spandex?

Good question, you can identify easily. Initially, you can untwist the yarn and closely observe its elasticity. Behavior of spandex like rubber. In most cases, the weft yarn contains spandex. But it is recommended visual and physical inspection.

 Conclusion

Calculating fiber percentage in PC and CVC fabrics is explained simply in this article. It is essential for quality control and the dyeing process. It is also crucial for cost calculation. This article is based on my practical experience. If you have any questions about fiber percentage calculation, let me know in the comments box.

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