BAST FIBER COMPOSITION

BAST FIBER (Flax, Hemp, Jute, Kenaf) COMPOSITION:

 In general, the bast consists of a wood core surrounded by a stem.  Within the stem there are a number of fiber bundles, each containing individual fiber cells or filaments.  The filaments are made of cellulose and hemicellulose, bonded together by a matrix, which can be lignin or pectin.  The pectin surrounds the bundle thus holding them on to the stem.  The pectin is removed during the retting process.  The lignin is the connecting cement between the individual fiber cells.  Although the lignin builds the bundle, in a composite it will be the weakest link. 

 The volume density of all bast fibers is identical, and structural differences mainly are a result from the chemical content. 

                                                                                                                  Comparative Chemical Composition (%):

 

FIBROUS MATERIAL:

CELLULOSE

HEMI- CELLULOSE

LIGNIN*

FLAX

62 – 71

16 – 18

2.0 –2.5*

HEMP       67-75

16 – 18

2.9 –3.3*
JUTE

59 – 71

12 – 13

11.8–12.9*

KENAF (bast)

65

13

21.6*

                                                                                                                                                                         * The higher the lignin percentage, the lower the quality.

 

 

Comparative Mechanical/Physical Properties of Bast:

 

 FIBROUS MATERIAL

 DENSITY (g/cm3)

 LENGTH (mm)

DIAMETER (um)

 L/D RATIO

TENSILE STRENGTHS (psi)

 FIBER

BUNDLE

RANGE

 AVG

RANGE

AVG

 FLAX

1.51

1.2

10 – 65

32

10 – 25

18

1,778

51,000

KENAF (bast)

-

1.2

1.4 – 5

2.6

14 – 23

21

124

58,000

KENAF (core)

0.31

-

0.4 – 1.1

0.6

18 – 37

30

20

-

HEMP

1.48

1.2

7 – 55

25

13 – 30

18

1,087

118,000

 

 

Properties of Natural Fiber, E-Glass, Sisal and Cotton:

 

Properties

 FLAX

HEMP

JUTE

SISAL

E-GLASS

COTTON

 Density g/cm3

1.4

1.48

1.46

1.33

2.55

1.55

Tensile strength* 10E6  N/m2

800 – 1500

550 – 900

400 – 800

600-700

2400

400

 

 

With the rise of composite material there is a renewed interest for natural fibers.  Jute is the number one produced natural fiber; twice the sum of flax, kenaf, ramie and hemp.   For many reason they can compete with glass fibers.  Many automotive components are already produced in natural composites, mainly based on polyester or PP and fibers like jute, flax,  or hemp. The adoption of natural fiber composite in this industry is lead by motive of a) price b) weight reduction and c) marketing (Processing renewable resources” ) rathan than technical demands.