Journal of Scientifi c & Industrial Research Vo1.58, September 1999, pp 705-710

Medium Density Particle Board From Weeds

D Kalita, S R Ghosh and C N Saikia* Regional Research Laboratory (C;:SIR) , Jorhat 785006, Indi a

Received: 28 April 1999; accepted: 21 June 1999

Medium density panicle boards were prepared from three species of weeds viz. Melastoma l11alabathricul11, Eupatorium odoratlllll

and Thvsan olaell1a mClxim.a, which were co ll ected from reserve forests of Assam and Aru nac hal Pradesh. The proxi mate chemical analys i·s of the plant raw materi als was carried oul. The cellulose contents in the plant va ri ed from 52.6-59.7 percent , the ash and silica contents from 4.6-8.9 percent and 1.78-2.90 percent respectively. The effect of wood panicle sizes on strength properties of the boards was studied and boards prepared with 20 percent UF res in from particles of -10M and +20M , showed the max imull1modulus of rupture (MOR) ( 143- 152 kg/cm2), wh ile MOR had grad uall y decreased in the boards prepared wit h finer panicles . When quantity of bi nder was reduced, MOR had decreased and water absorption increased. Boards prepared with mixtures of UF and PF res ins in different propor­tions gave va ri able MOR (149-159 kg/cm2) and water absorption (22-16 percent ) properties. However, boards prepared with mi xtu res of UF and PF resi ns (50:50) showed reasonably hi gh MOR (153- 157 kg/cm'). From these results, it could be concluded that weeds could be a good source of raw materi al for particl e board industry.

Introduction In the forests, marshy lands and ri ver va ll eys of In­

dia, pl enty of a variety of weeds are grown . T hese are unwanted plants, which interfere with the growth rate of other valuable trees and a lso cult ivated crops. Some of the common weeds, abundant ly ava il able in the for­ests of N o rth Eastern reg ion are Melastoma malahathricum, Eupatorium odoratum, Saccharum sponteneul11, Phragmites karka, Lalltallo camera and Thysanolaema maxima, etc. These plants find no appro­priate commercial utilization except for their use as fue l for do mes ti c purposes, and construc tin g te mporary hutments and fences. Many of these weeds , possess sub­stanti a l amount of cellulosic bio mass but se ldom used as pulp and paper makin g raw material because of hig h s ilica contents; at the same time, proper brightness of paper cannot be obtained by conventi onal bleaching pro­cesses . However, the weeds a lone or in combin ati on with other plant materials can very we ll be used for prod uc­ing med ium density parti c le boards. These boards find appl ication in building industry'as cei ling til es, part it ion wall s, decorative 'wa ll covers and for making flash doors, show room cabine ts , shelves , furniture and fi xtures, etc . The advantages of us ing particle boards over plywood or wooden plank s are that the particle boards possess some unique properties like homogeneity, smooth sur-

* Author to whom correspondence should be addressed.

face, dimensional stability, uniform g rain density and above a ll , these boards are free from insect bites. The boards a lso to certa in extent can be rendered water proof and flame re tardant with special formu lations.

Due to recent res tricti on imposed by government on fe lling of trees, the hard board industry is facing an acute shortage of wood raw materi a ls . The abu ndant availab il ­ity of weeds, some of which are annual and some are perenni al, there is enough poss ibility of usi ng them as a lte rnative raw materi a l fo r producing low, med iu m and high density partic le boards.

The authors have carried out a laboratory scale inves­ti gation to find out the suitab ility of a few spec ies of weeds availab le in the forest o f North Eas tern reg ion , for producing medium density particle boards.

Materials and Methods The bi omass lI sed for the study reported here were

co ll ec ted from th e rese rve fores ts of As sam and Aru nachal Prades h. The three species of weeds vi z. Melastoma malahathricum, Eupatorium odoralul11 and Thysanolaema maxima were sele~ted fo r eval uation on the basis of their abundance of ava ilability in the for­ests I.

M. malahathricum is a shrub found near water courses and moist piaces in the forest. The bark is reddish brown in colour and the leaves are lanceolate to oblong .

706 J SCI IND RES VOL.58 SEPTEMBER 1999

Table I - Proxi mate chemical analysis of weed species. fibre lengths and diameters

Propel1ies

Solubil it ies. %

Cold water

Hot water

1% NaOH

Alcohol -benzene( 1:2)

Cellulose. %

Pentosan. %

Lignin . %

Ash. %

Silica. %

Fibre length* , mm Fibre diameter*. ~m

M. malabathricum

16.6

20.4

32.6

5.2

52.6

18.6

22.4

7.3

1.78

1.78±1.35 12.21±2.36

E. odoralUlIl T. maxima

12.8 10.3

16.2 12.8

27.5 35.2

3.6 8.8

58.3 59.7

21.3 25.0

26.8 24.5

8.9 4.6

1.96 2.90

1.56±1.1O 1.86±0.62 12.28±2.48 11.43±2.08

* Mean values ± standard deviation : Five observations per mean.

Table 2 - Characteristic properties of particle boards made from M. malabalhr;cum with particles of different sizes

Particle Thickness Density Moisture MOR Water Total size content absorption volumetric

swelling

mm g/cmJ % kg/cm! % %

(W) 7.2 0. 82 7.4 106 24 38

(Xl 7.1 0.85 7.6 124 31 21

(Y) 7.1 0.86 7. 1 143 20 II

(Z ) 7.0 0.88 7.4 139 26 12

Condit ions of board formation : UP resi n 20 'Y() on OD material . temperature 1 55±5"C, pressure 35±5 kglcm2 , ti me 10 min.

E. adarattlm is a coarse straggling shrub and is an obnoxious weed in the plains and foothills, interfering with the natural regenerat ion of timber trees.

So also, T. maxima is a tall reed like perennial grass found in shady slopes in forests, especially on damp, steep banks along ravines and water courses through out the country.

The plant materials after collection were cleaned by spraying water and dried in air and then cut manually into 2-2.5 cm length chips. The chips with 10-12 per­cent moi sture were passed through a Wiley mill to con-

vert them to finer particle sizes . The particles thus ob­tained were screened through British Standard Sieves (BSS) of different sizes and boards were made from particles that retained on 4 BS sieve (+4 M) (W), passed through 4 BS sieve but retained on 10 BS sieve (- 4 M + 10M) (X), passed through lOBS sieve but retained on 20 BS sieve (-10M +20 M) (Y) and that passed through 20 BS sieve (-20 M) (Z).

The urea formaldehyde (UF) resin alone or in combi­nation with phenol formaldehyde (PF) res in was used as binder for ligno-ceHulosic materials . The UF resin was

KALITA et at : MEDIUM DENSITY PARTICLE BOARD 707

Table 3 - Characteristic properties of particle boards made from E. odoratulII with particles of different sizes

Particle Thickness Density Moisture MOR Water Total size content absorption volumetric swelling

mm glcmJ % kglcm2 % %

(W) 7.8 0.83 9.4 116 28 36

(X) 7.3 0.84 7.6 133 30 28

(Y) 7.2 0.86 7.3 149 22 21

(Z) 7.4 0.89 7.6 141 24 24

Conditions of board formation : Same as given in footnote in Table 2.

Table 4 - Characteristic properties of particle boards made from T. maxima with particle of different sizes

Particle Thickness Density Moisture MOR Water Total size content absorption volumetric

swelling

mm glcmJ % kglcm2 % %

(W) 7.7 0.84 7.4 28 123 21

(X) 7.5 0.86 7.8 30 136 22

(Y) 7.2 0.84 6.2 24 152 16

(Z) 7.2 0.87 7.2 29 146 18

Conditions of board formation: Same as given in footnote in Table 2.

milky white in appearance (pH 7.5-S) with specific grav­ity 1.19-1.21 , viscosity 30-34 Cp having 50-52 percent solid contents. So also PF resin with specific gravity 1.15-I.IS, viscosity 23.5-25.2 Cp, having total solid contents 5S-62 percent was used.

All other chemicals used are commercial grade.

Proximate Chemical Analysis The proximate chemical analyses of the weeds

were carried out to find out the diferent constituents of the plant biomass. The air-dried chips were powdered in a Wiley mill and the powder that passed through 40 BS sieve and retained on 60 BS sieve were analysed adopt­ing TAPPI standard methods2 and the results are pre­sented in Table I.

Extraction of fibres and detennination of fibre dimen­sions

For extraction of fibres,the chips of weed materials were sulphate cooked in a 10 L stainless steel rotary digester with 16 per cent total chemicals (NaOH:Na

2S

=3: I) for 3 h at 16Q±2°C at a material to liquor ratio 1:5. The well digested pulps that obtained were washed thor­oughly with distilled water and then air dried. Dimen­sions of fibres were determined under a Dokuval photo­microscope (lEOL, Japan) at magnifications (100 X). The length and diameter of the fibres are included in Table I. .

Determination of Modulus of Rupture (MOR) To determine the MOR, first of all , the maximum load

in kg for breaking the sample under test was found out. For this purpose, samples of 30 cm length, 5 cm width,

708 J SCI IND RES VOL.58 SEPTEMBER 1999

l' able 5 - Characteri stic properties of particle boards made with di fferent quantities of UF resin as binder

Sample Resin Thick ness content

% mm

5

10

15

20

7.2

7. 1

7. 1

7.0

7. 1

7.2

7.2

7. 1

7.1

7.2

7.0

7.0

Density

g/cm'

0.8 1

0.83

0.85

0.86

0.83

0.84

0.86

0.84

0.85

0.87

0.83

0.88

Moisture co ntent

%

10.2

9.8

10.0

8.8

9.1

8.6

7.2

7. 1

7.5

7.3

7.1

7.0

A - M. malabalhricum. B - E. odorallllll . C - T. ma.xima..

Panic le size (Y)

and 1.5 c m th ickness were ta ke n. The MOR was the n

calcu la ted and expressed in kg/c m2 by fo llow ing the for­m ula]

3 P L R -- -----

w he re, P- max imum load in kg, L- length o f span, b­

w idth of speci me n in em and d- depth o f spec imen in

c m .

Preparation of particle boards The wood part icles of standard s ize were mi xed me­

c hanically wi th required quantities of resi n . The resin

m ixed part ic les were the n a ir dri ed to bring the moi sture

contents to 5-7 pe rcent. The res in-mixed and dri ed pa r­

ticles, we re spread uniformly o ve r a mould to form mat­

tress as per th ic kness requ ire ment o f the fini shed board

and then compressed in a hydraulic pressat 155±5 °c in 35±5 kg/cm2 pressure for 7 .5-10 min . The boards thus

formed were taken out and kept in stake under pressure

for 3-4 days . Af te r th is pe riod, the boards were s ide trimmed and their c haracte ri stic prope rties were evalu-

MOR Water Total absorp-tion volumetri c

swell ing kg/cm2 % %

106 32 26

110 36 25

96 3 1 29

118 28 24

126 26 20

129 29 2 1

136 2 1 19

142 20 2 1

145 18 18

149 17 14

146 18 15

152 16 13

ated as pe r standard spec ification for m edium de ns ity

parti c le boards4.

To study the effect of wood particle s izes o n stre ngth

p rope rties, the boards were pre pa red w ith partic les of

di ffe rent s izes by u sing fi xed quantity of UF res in as

binde r. Tables2,3.4 g ive the c haracte ristic p ro perti es of

boards prepared w ith parti c les of different s izes o f M. malabathricum, E. odoratum and T maxima respec ti vely

w ith 20 pe rcent UF res in o n OD m ate ri al basis . The data

reported are averages of three expe rime nta l readings.

Boards were a lso m ade by vary ing the q ua ntities of

UF res in as binder under optimum conditions of heat

and p ressure as ind ica ted above to see the effect on

MOR (kg/cm2), wate r a bsorp ti on (%) of the boards. For

th is study, particles of size ( Y ) were taken. The characteristic properties of the boards are eva I uated and tabulated in Table 5, Agai n, sets of experiments were also carried out for producing boards with mixtures of UF and PF res ins in different propor­tions, The characteri stic properties of the boards prepared are given in Table 6.

KALITA et af : MEDIUM DENSITY PARTICLE BOARD 709

Table 6 - Characteristic properties of particle boards made with different proportions of UF and PF resins

Sample Resin Thickness Density content

UF:PF mm g/cml

A 100:0 7.1 0.82

B 7.2 0.84

C 7.1 0.83

A 75 :25 7.2 0.81

B 7.8 0.86

C 7.5 0.82

A 50:50 7.6 0.83 B 7.2 0.85

C 7.3 0.83

A 25:75 7.1 0.84 B 7.3 0.81 C 7.6 0.83

A 0:100 7.4 0.87 B 7.6 0.86 C 7.8 0.84

A - M. malabathriculI1, B - E. odoratull1, C - T maxima. Particle size (Y)

Results and Discussion The proximate chemical analyses of the three weeds

viz. M. malabathricum., E. odoratum and T maxima are shown in Table I. The plant biomass contains 52-59 per­cent cellulose, 22-26 .8 percent lignin and 18-25 percent per:tosan , wi th high ash contents varying from 4 .6-8.9 percent. In respect of cellulose contents (52.6-59.7 per­cent) and fibre lengths ( 1.78- 1.86 mm) and diameters (I I .43-12.28 ~m) , the weeds are comparable to that of bamboos. The other properties except ash and s ilica (1.78-2.90 per cent) are comparable to those of other convention al plant materials6

.

Study on the effect of particle sizes on the strength properties of the boards as eva lu ated (Tables 2, 3 and 4) has shown that boards made from particle of size (Y), have the maximum MOR (143-152 kg/cm2), minimum total volumetric swelli ng ( 11-2 I percent) and water ab­sorption (24-29 percent) in 24 h. The MOR gradually decreases in case of boards made with finer particles. The boards made with varying quantities of resin (5-20 percent on 0 Dmaterial) exhibit gradual increase of MOR (96- 152 kg/cm2) v. ith increase in density (0.8 1-

Moisture MOR Water Total content absorpt ion volumetric

swelling % kg/cm2 % %

8.8 139 24 22 8.6 136 28 20 8.0 141 21 20

8.3 149 22 20 8.0 153 18 21 8.1 151 20 18

8.0 153 21 18 7 .8 157 20 16 7.6 156 21 17

8.2 158 18 18 8.0 162 16 18 7.6 159 17 17

7.6 168 16 16 7.4 169 14 14 7.4 173 13 12

0.88 g/cm3) with the increase in the quantity (%) of resin.

So also, it is seen that water absorption (32-1 6 percent) and total volumetric swelling (29-13 percent) decrease with increase in densities of the boards . However, the maximum values of MOR are exhibited by boards pre­pared with 20 percent UP resi n contents (146- I 52 kg/ cm2) with comparatively less water absorption ( 18- 16 percent) and total volumetric swelling (15-\3 percent).

In Table 6, the properties of boards made by using mixtures ofUF and PF resin are shown. The boards with PF as binder exhibit the highest values of MOR ( 168-173 kg/cm2) with 13-16 percent water absorption in 24 h. The use of PF resin as binder can be recommended when over :::11 cost factor is not considered. Ho\vever, boards prepared with 50:50 (UF:PF) resin conten t are found to possess MOR (153- 157 kg/cm2) with less wa­ter absorpt ion (20-21 percent) in compari son to the boards made with UF resin alone .

Conclusion From the above study, it may be concluded that the

forest weeds, viz . Melastoma malabathricum, Eupato-

710 J SCI IND RES VOL.58 SEPTEMBER 1999

rium odoratum and Thysanolaema maxima, can be uti­lized for producing medium density particle boards. This study has optimized the requirements of wood particle sizes, amount of the binders to be used, pressure and temperature conditions to obtain single layered board as per Indian Standards Specifications.

Acknowledgements

The authors express their sincere gratitude to the Di­rector, Regional Research Laboratory, Jorhat, Assam for his permission to publish this paper. The authors also like to acknowledge Indian Council of Forestry Research and Edu(;ation, Dehradun, for financial assistance under 'Research Grant Fund".

References Wealth of India, Vol. III, VI and X, Publications & Information Directorate, Council of Scientific and Industrial Research, Dr. K S Krishnan Marg, New Delhi, 1962.

2 TAPPI Standard and Suggested Methods (Technical Association of Pulp and Paper Industry), TAPPI Press, Atlanta, New York, 1980.

3 Indian Standard IS : 2380-1977 : Metlwds of test f or wood par­ticle boards alld boards from otherliglloceLluLosic materials (I n­dian Standards Institution, Manak Bhavan, New Delhi) 1978.

4 Indian Standard IS : 3087-1985 : Specification for wood particle boards (medium density ) for general purposes (Indian standards Institution, Manak Bhavan, Bahadur Shah Zafar Marg, New Delhi) 1986.

5. Saikia C N, Chali ha, B P,lyenger M S & Lo<ilh S B , J Illst Ellgr 51(10), pt CH 3 (1971) 87-89.

6 Ali F & Saikia C N , J Sci Ind Res, 56 (1997) 618-626.