Kapok Fiber

Kapok fiber is a natural cellulose fiber with the characteristics of ultra-fine, light weight, mildew and moth-proof, acid and alkali resistance and warmth retention, which meets the consumer's demand for health, nature and environmental protection. Alfa Chemistry offers kapok fiber products to meet your specific needs.

Kapok Fiber

Introduction

Kapok fiber is the fruit fiber of several plants in the Kapok family of Malvaceae, belonging to the single cell fiber, which is attached to the inner wall of Kapok capsule shell, and is developed and grown from the inner wall cells. Kapok fiber is generally about 8-32 mm long, about 20-45 μm in diameter, and has three colors: white, yellow and yellow-brown. It is the thinnest, lightest, most hollow and warmest fiber material among natural ecological fibers, and is widely used in various home textile products, buoyancy materials, heat insulation and sound absorption materials.

Physical Performance

Kapok fiber is cylindrical in the longitudinal direction, with a smooth surface, no twists and good luster. The fiber is thicker in the middle section, thinner at the tip, and closed at both ends. The cells are full of air, with a hollowness of up to 80%-90%. It is easy to fold and flatten in the longitudinal direction.
The cross-section of kapok fiber is round or oval. When the cross-section cells are not broken, they are air sac-like. After breaking, the fibers are flat and ribbon-like. There is no secondary cell wall cellulose deposition process similar to cotton fiber. The cell wall thickness is only 0.5-2 μm, which is almost transparent. There is more wax on the surface, which is relatively smooth, not easy to absorb water, and not easy to tangle. Kapok fiber has a unique thin wall and large hollow structure.

The basic physical performance of kapok fiber are shown in the following table.

Performance	Kapok Fiber
Length	8-32 mm
Linear density	0.9-1.2 dtex
Density	0.29 g/cm³
Breaking strength	0.8-1.4 cN/dtex
Elongation at break	1.5-3.0%
Initial modulus	48.7-114.5 cN/dtex
Moisture regain	10-10.73%
Torsional stiffness	71.5×10^-4 cN·cm²/tex²
Compression modulus	43.63 kPa
Refractive index	1.718

Chemical Performance

Acid and alkali resistance. Kapok fiber has good acid and alkali resistance. At room temperature, dilute acid and NaOH solution will not affect it. Under different dissolution conditions, kapok fiber was placed in different acidic and alkaline solvents respectively. The dissolution of the fiber after a certain period of time is shown in the table below.

Reagent	Dissolution Temperature	Dissolution Time	Result
5% NaOH	Room temperature	20 min	Insoluble
60% H₂SO₄	50 ℃	15 min	Partially dissolved
75% H₂SO₄	30 ℃	10 min	Completely dissolved
20% HCl	Room temperature	15 min	Insoluble
30% HCl	100 ℃	20 min	Partially dissolved
53% HNO₃	Room temperature	30 min	Insoluble
65% HNO₃	100 ℃	15 min	Completely dissolved
CH₃COOH	Room temperature	15 min	Insoluble
80% HCOOH	Room temperature	20 min	Insoluble

Dyeability. Kapok fiber has a low dyeing rate and is usually dyed with direct dyes. This is because kapok fibers contain a large amount of lignin and non-cellulose substances, which are entangled with cellulose macromolecules and the influence of intermolecular forces hinders the activity of some hydroxyl groups on cellulose. The dye molecules cannot smoothly enter the fiber, resulting in poor color fastness of the fabric.
Warmth retention. Kapok fiber has excellent thermal insulation performance. On the one hand, the fiber is highly hollow and filled with a lot of air, which can easily form a static air layer. Since the specific heat capacity and thermal conductivity of static air are both lower than those of dry fiber, the fiber conduction thermal resistance is high. On the other hand, the fiber porosity is as high as 102%, the yarn body is fluffy, and the ultrafine fiber can easily enter the fabric gap, making the inter-fiber pores smaller and reducing the heat dissipation. Both will increase the warmth retention of kapok fiber.
Antibacterial property. The main reasons for the antibacterial property of kapok fiber are two-fold. From the perspective of fiber structure, kapok fiber has thin walls, high hollowness, and large specific surface area. The internal gaps of the fiber are rich in oxygen, which hinders the reproduction of anaerobic bacteria on the fiber surface. From the perspective of fiber chemical composition, the flavonoids and triterpenes contained in the fiber have good resistance to bacteria.

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