Latest results and overview

Work Package 5: Utilisation of kenaf for industrial products and energy.

S.J.J. Lipsdepartment Fibre & Paper technology

Athens 26 February 2007

Content

• Overview– fibre decortication (separation)– fibre quality– insulation mats– kenaf core absorbers– kenaf fibre/PP composites

• Extra tests of kenaf mats under high humidity

• SEM pictures of kenaf

Market and techno-economic feasibility study

• Separation only worthwhile if both fractions can be sold.

• Application of separated kenaf bast fibre in insulation.

• Application of kenaf core as absorber.

Affected kenaf stems

Unaffected FAIR project

Affected BIOKENAF project

Fibre decortication

• Easy Separation no extra retting necessary

• Still 11% of core particles present in the fibre fraction

Tensile fracture of a kenaf fibres

Material Tensile strength (MPa)

St.dev n

Kenaf FAIR retted 556 – 682 FAIR green decorticated 276 - 435 CETA fibres 343 - 486 Uni Catania fibres 425 41 3 Uni Nova fibres 374 69 3 Uni Nova fibres retted 462 88 5 Flax 500-880 Hemp 400-750 Jute 351-468 Sisal 650

Tensile fracture of a kenaf fibre bundle

Insulation mats

Info website 0.038ISOVERSonepanel

Info website NEN-EN 12667

0.036ROCKWOOLSpouwplaat 433

Info website ISO 8302/91

0.039KEFIISOLKENAF

Biokenaf measurements NEN-EN 12667

0.041ISOVLASISOVLAS PL

Biokenaf measurements NEN-EN 12667

0.043KEFIKenaf

RemarksThermal conductivity

[W.m-1.K-1]

CompanySample

Coefficient of thermal conductivity

Insulation mats

• Kenaf mats showed 10-15% lower than given values for mineral mats

• With less core particles left in the fibres lower values comparable to the measured flax mats are expected.

Moisture absorption of natural fibres

5.0

7.0

9.0

11.0

13.0

15.0

17.0

19.0

21.0

0 20 40 60 80 100 120 140 160

time (h)

wa

ter

(%)

kenaf CETA green decorticated

kenaf CETA warm water retted

kenaf FAIR warm water retted

flax green decorticated

flax dew-retted

jute yarn

sisal fibres from yarn

Moisture uptake of insulation mats under semi- aerobic conditions

0%

20%

40%

60%

80%

100%

120%

0 1000 2000 3000 4000

hours

moi

stur

e up

take

(%

)

flax 100% RHflax 94% RHflax 85% RHkenaf 100% RHkenaf 94% RHkenaf 85% RH

Moisture absorption insulation mats under aerobic humid conditions

0%

10%

20%

30%

40%

50%

60%

70%

0 500 1000 1500 2000 2500

hours

wei

ght g

ain

(%)

kenaf 1kenaf 2flax 3flax 4

90% RH 94% RH

Moisture desorption of locally wetted insulation mats at 23 oC and 30% Relative Humidity

0%

5%

10%

15%

20%

25%

30%

35%

0 5 10 15 20 25

hours

mo

istu

re c

on

ten

t (%

)

kenaf 1

kenaf 2

flax 3

flax 4

Moisture absorption insulation mats under aerobic humid conditions

Moisture absorption of fibre mats

• Kenaf mats show no visible microbial degradation at 94% RH and 23 0C and have a low moisture uptake.

• Flax mats with fire retardants show high water uptake in humid air and microbial degradation.

• After wetting kenaf mats show faster evaporation than flax mats with fire retardants.

• Use of fire retardants with kenaf mats will also increase moisture uptake

Moisture absorption of fibre mats

• Use of fire retardants with kenaf mats will also increase moisture uptake.

• Good ventilation is a prerequisite

Conclusions - fibres

• Easy fibre extraction

• weakened fibres - 60% of maximum

• Weakened fibres can be used insulation mats

Fibre Quality

• To ensure sustainable kenaf fibre business

• a broader range of possible applications must be developed by improving the quality of the fibres.

• Higher quality fibres might be achieved by studying and developing new retting and extraction processes.

Water retention of animal bedding materials

0,000,501,001,502,002,503,003,504,004,50

C250 C2500

Speed Of Centrifuging (rpm)

WR

V (

g w

ate

r /

g d

rie

d

ma

teri

al)

Wheat Straw Flax Core Hemp CoreKenaf Core Large Kenaf Core Medium Kenaf Core FineWood Shavings

Water retention kenaf pith

2.0

6.0

10.0

14.0

18.0

22.0

0 5 10 15 20Time of soaking (Hours)

WR

V (

g w

ate

r /

g d

ry m

att

er)

Flax Core Hemp Core Kenaf Core FineKenaf Core Medium Kenaf Core Large Wood ShavingsWheat Straw Kenaf Pith

Structure of kenaf stem (Everglades 41)

Structure of kenaf stem (Everglades 41)

Bast structure of kenaf (Everglades 41)

Transverse section of a Kenaf core particle

Transverse section of a Kenaf core particle

Transverse section of a Kenaf core particle

Parenchymatic tissue in Kenaf core particles

Parenchymatic tissue in Kenaf core particles

Pith cells

Pith cells

Conclusions - water absorption kenaf core

• Large core fraction is the best water absorber of all the tested materials.

• Kenaf core medium and fine absorb – somewhat less than wheat straw and core of

hemp and flax– more than wood shavings

• Kenaf pith is a very good absorber.

Oil absorption kenaf core and other materials

0

1

2

3

4

5

6

7K

en

af

Pit

h

Str

aw

Wo

od

Sh

av

ing

s

Fla

x C

ore

K C

Fin

e

He

mp

Co

re

K C

La

rge

K C

Me

diu

m

Ch

em

So

rb

Oil Absorption

Different letters mean significant differencesa

b c

e e e

f

d

c

g/g

Oil absorption of milled kenaf core and milled other materials

0

5

10

15

20

25

30

Ke

na

f P

ith

K C

La

rge

Fla

x C

ore

Wo

od

Sh

av

ing

s

Str

aw

He

mp

Co

re

K C

Fin

e

K C

Me

diu

m

Oil Absorption

d

a

b b d d

Different letters mean significant differences

cb

Oil absorption of milled kenaf core and milled other materials

0

1

2

3

4

5

6K

C L

arg

e

Fla

x C

ore

Wo

od

Sh

av

ing

s

Str

aw

He

mp

Co

re

K C

Fin

e

K C

Me

diu

m

Oil Absorption

d

b b

d d

Different letters mean significant differences

cb

Oil absorption of kenaf fibre mats (K.E.F.I.)

0

5

10

15

20

25

30

0 100 200 300 400 500

density (kg/m3)

ab

so

rpti

on

(g

/g)

kenaf mat theory kenaf mat flax mat flax mat theory

Conclusions – oil absorbtion

• Kenaf core as received shows low level of oil. The level is comparable to that found by Ghalambor

• Kenaf core is not a better oil absorber than the other tested organic materials

• Extra milling increases the oil absorption capacity

Conclusions – oil absorbtion

• Kenaf pith absorbs 200% more oil than kenaf core

• Milled kenaf core absorbs 500% more oil than not milled kenaf core. This is comparable to the ratio found by Ghalambor

• Kenaf /polyester mats show high absorption capacity for oil. They can be pressed out and re-used at least six times without loosing their absorption capacity.

Producing Kenaf-Polypropylene composite

Moulded test pieces

matrix

Strength properties of kenaf fibres/ PP compounds

Material Flexural Modulus

[GPa]

Flexural Strength [MPa]

Strain [%]

Charpy impact [kJ/m2]

CETA 3.3 (0.2) 53 (1) 3.6 (0.1) 12 (1) CETA +MAPP 3.2 (0.1) 71 (1) 4.1 (0.1) 12 (2) UniNova +MAPP* 3.1 (0.2) 70 (1) 4.2 (0.1) 13 (2) *warm water retted

Strength properties of kenaf fibres/ PP compounds

Material

Flexural Modulus [GPa]

Flexural Strength [MPa]

Strain [%]

Charpy impact [kJ /m2]

CETA* 3.3 53 3.6 12 CETA +MAPP 3.2 71 4.1 12 UniNova +MAPP 3.1 70 4.2 13 FAIR unretted 4.0 53 3.1 11 FAIR retted 4.1 55 3.2 12 Jute 3.2 69 4.8 18 Hemp 2.7 - 3 59 - 67 4.8 – 5.3 13 - 19

*fibres produced by CETA and extracted by KEFI

Conclusions Kenaf/PP compounding

• The tested kenaf fibres can compete with other natural fibres on flexural strength properties, but not on impact strength.

• Retted kenaf fibres harvested in autumn did not give stronger composites than CETA/KEFI fibres

• Quality of the fibres in relation to harvest time and extraction method must be further investigated

Conclusions - general

• Technically numerous application are possible.

• Competitiveness with other materials or quality aspects limits the number of applications.

• Higher quality fibres might be achieved by studying and developing new retting and extraction processes.