Production and Properties of Liquefied Oil-palm Stem Adhesive

Arif Nuryawan

, Iwan Risnasari

, Hana Pratiwi Sihombing

and Diana Situmorang

Department of Forest Products Technology, Faculty of Forestry, Universitas Sumatera Utara, Medan, Indonesia

Faculty of Forestry, Universitas Sumatera Utara, Medan, Indonesia

Keywords: liquefaction, oil palm stem, wood adhesive

Abstract: The objective of this study was to evaluate production and properties of liquefied oil-palm stem adhesive.

Method for production of this adhesive was inspired by bio-refinery concept. In this context, vascular

bundle of oil-palm stem was liquefied through liquefaction process involving thermo-chemical reaction

using chemicals of H

, phenol, and NaOH at 90C. Properties of the adhesive were compared to

Indonesian Standard for phenol-formaldehyde (PF) resins. Results of the examinations showed color of the

liquefied adhesive was brown-blackish, specific gravity was 1.26, solid content was 86%, viscosity was 111

cP, pH was 7.8, gel time was 98 minutes, and free formaldehyde was not detected. Even though the

properties of the liquefied adhesive made of vascular bundles’ oil-palm stem were slightly differ from PF

resin, application of this adhesive as binder of wood product should be recommended because of its

feasibility as the adhesive.

1 INTRODUCTION

Plantation forest and oil-palm plantation have been

expand since the existence of natural forest become

decreasing. Plantation forest generates wood, not

only from main log but also from thinning and

pruning volumes, which be used for wood industry’s

raw material such as moulding wood, core-plywood,

particleboard, fibreboard, pulp and paper. Even

though oil-palm plantation mainly produces fruits

for manufacturing palm oil for cooking purpose,

huge amount of biomass is also being generates

regularly, such as leaves, frond, empty fruit bunch,

and trunk. These lignocelluloses materials up till

now have been still limited in utilization.

It was known that oil-palm leaves have been used

for decades only as cattle animal feed. Advanced

processing of these materials has been recommended

for health and disease prevention for humans

(Mohamed, 2014) including for their skin caring

(Yusof et al., 2016). Related to product substitution

of wood, Nuryawan & Rahmawaty (2018) reported

that particleboards made of oil-palm leaves have

unsatisfying physical and mechanical properties

therefore more treatments should be applied such as

addition more hardener, application of surface layer,

or replacement interior type adhesive into exterior’s

one.

Both frond and empty fruit bunch were also still

limited in utilization. The first was mainly used as

roughage source in pellet for ruminant feeding

(Zahari et al. 2002) and the latter has been started to

be utilized as bio-refinery feedstock (Tan et al.,

2016) to produce fine chemicals, bio-fuel, and green

polymeric materials.

Similarly, oil-palm trunk tends to be converted

into advanced materials via bio-refinery concept

rather than conventional one. Since its properties are

very different from wood, utilization in solid form is

less promising. It is very hygroscopic in the nature;

consequently, it raises dimensional instability thus

less durable. Many attempts have been done for

improving these unbeneficial properties by

employing whole stem into products, for example

laminated combination using tropical wood (Nordin

et al., 2004), engineered composite board (Wahab et

al., 2013), or resin impregnated to the stem (Rosli et

al., 2016).

Anatomically, oil-palm stem comprised of

vascular bundles embedded in parenchyma tissues

(Lim & Gan, 2005). The presence both of these parts

influences the characteristics further (Ramle et al.,

2012), hence some scientists separated between the

two prior to further processing and utilized only one

part, for instances parenchyma tissue for obtaining

sugar (glucose and xylose) (Mansor & Ahmad,

Nuryawan, A., Risnasari, I., Pratiwi Sihombing, H. and Situmorang, D.

Production and Properties of Liqueﬁed Oil-palm Stem Adhesive.

DOI: 10.5220/0010137100002775

In Proceedings of the 1st International MIPAnet Conference on Science and Mathematics (IMC-SciMath 2019), pages 107-111

ISBN: 978-989-758-556-2

107

1990) and producing starch for making wood

adhesive (Salleh et al., 2015) even though the yield

was very limited and depended on position on the

stem; bottom, middle, or upper part. Conversely

only limited reports employed vascular bundles for

raw materials, such as making composite plastics

using matrix of polyethylene (Lubis et al., 2009) and

producing oriented strand board (OSB) in laboratory

scale (Nuryawan, 2010).

Therefore in this research, utilization of

vascular bundles obtained from oil-palm stem was

investigated which was inspired by bio-refinery

concept. In this context, vascular bundle was

liquefied through liquefaction process involving

thermo-chemical reaction and resulting in various

bio-copolymers such as coatings, various polymers,

carbon fibres, foams, including adhesives (Ugovšek

et al., 2011). Liquefaction is one method for

converting whole biomass into liquids (Jiang et al.

2018). This work is reasonable because vascular

bundle is one of lignocelluloses material having

nature equal to wood with lignin content up to 22 %

(Chew & Bhatia, 2008; Nuryawan et al., 2012). In

addition, in the recent publication (Jiang et al.,

2018), both virgin and waste lignocelluloses

materials have been succeed to be turned into wood

adhesives.

Because this work is the initial report on

utilization of vascular bundles as raw material for

making wood adhesives based on bio-refinery

concept, this study then discussed the preparation,

processing as well as the characteristics of resulting

liquefied adhesive.

2 MATERIALS AND METHODS

2.1 Preparation of the Materials

It was reported that machining and sawing properties

of oil-palm stem was difficult and the quality of

finished material was rough because of presence of

silica (Lim & Gan, 2005). Therefore, in this

experiment converting oil-palm stem was carried out

using planer machine. This machine was capable to

alter solid form into particle size in short time.

Resulted particles then were immersed in the water

for 8 hours for separating between vascular bundles

and parenchyma. The vascular bundle will be

remained in the sieve as residue and the parenchyma

will be passed the sieve as filtrate. Resulted vascular

bundles were air-dried, grinded into 20-60 mesh in

size and oven-dried (103+2)C for 24 hours.

2.2 Production of liquefied adhesive

100 g oven-dry vascular bundle with moisture

content (MC) 5% was placed into beaker glass. 25

ml H

98% (5% phenol weight) was added and

stirred gently for 30 minutes. The mixture then was

conditioned in sealed beaker glass. After 24 hours,

500 ml liquid phenol (hereafter melted in 60C) was

added into the mixture and then stirred gently until

appear homogenous. Sodium hydroxide (NaOH)

40% was added until the pH 8, then formalin 37%

was added with ratio phenol and formaldehyde of

1:1.2. The mixture then was filtered using filter

paper and the extract was heated at 90C in the

water bath for 2 hours. The extract then was kept in

glass bottle prior to applying.

2.3 Determination of Basic Properties

of the Liquefied Adhesive

Determination and evaluation of basic properties of

resulted liquefied adhesive were carried out

according to Indonesian Standard SNI 06-4567-1998

for phenol-formaldehyde (PF) resin. The properties

consisted of performance, specific gravity, solid

content, viscosity, pH, gel time, and free

formaldehyde.

Performance of liquefied adhesive was observed

either using naked eye or microscope, consisted of

clarity, color, and presence of dust. Clarity of the

adhesive was performed by visual observation either

using naked eye or microscope. Sample of the

adhesive was poured onto a petri dish or a glass slide

in order to form film layer. Observation of color and

presence of peculiar objects such as granules or dust

particles was carried out accurately using certain

magnification.

Specific gravity (SG) was measured using

gravimetric method using picnometer and analytical

balance. An empty and oven-dry picnometer was

weighed (W1), distilled water-filled picnometer was

weight (W2), and dextrin’s adhesive-filled

picnometer was also weighed (W3). The specific

gravity was determined as in Equation (1).

𝑆𝐺 









(1)

Solid content (SC) was measured using

gravimetric method using ceramic crucibles,

convection oven and analytical balance. Weigh of

initial sample in the crucible about 2 grams (W1)

was dried in the oven at (103+2)C for 24 h until

constant weight (W2). The solid content was

determined as in Equation (2).

IMC-SciMath 2019 - The International MIPAnet Conference on Science and Mathematics (IMC-SciMath)

108

𝑆𝐶 









𝑥 100% (2)

Viscosity was measured using a viscometer with

appropriate spindle. Sample of liquefied adhesive

was placed in a 100 ml beaker glass, and

measurement was conducted in room temperature

(25C) using spindle with velocity in rpm (rotary per

minute).

Electronic pH meter was used to determine the

acidity of liquefied adhesive sample. Sample was

placed in a 100 ml beaker glass, and measurement

was conducted when the sensitive electrode was

soaked into the sample.

Gel time is defined as a period for gelatinization

or altering liquid adhesive into solid phase. In other

word, gel time is time needed for pre-polymer

liquefied adhesive becomes solidifying or curing. In

some cases, i.e formaldehyde based adhesive,

determination of gel time uses aid of hardener or

catalyst such as ammonium chloride (NH

Cl) for

urea-formaldehyde (UF) resin and NaOH for PF in

order to make curing. In this experiment, liquefied

adhesive does not require specific condition like

acidic or alkaline. Therefore simple method for

determining gel time was applied. About 10 grams

liquefied adhesive was placed in the reaction tube,

then subsequently it was positioned under 2 cm in a

boiling water bath. Calculation of time was finished

when the sample in the reaction tube was altered into

hardened.

Free formaldehyde was determined by weighing

adhesive sample 20 g (W). The sample then was

mixed with 50 ml distilled water in the Erlenmeyer.

Both indicators of methyl red and blue were added

2-3 drops into the mixture and subsequently it was

neutralized using either hydrochloric acid (0.1N

HCl) or sodium hydroxide (1N NaOH). Afterwards

the mixture was added 10 ml NH

OH 10 wt% and

10 ml NaOH. Erlenmeyer then was covered, shake,

and placed in water bath at 30C for 30 minutes.

Titration using HCl was done until the colour altered

from green into blue-grey and then red-purple (V

Using the same procedure, blank solution was made

without addition of adhesive sample (V

). Free

formaldehyde (FF) then was calculated using

Equation (3).

𝐹𝐹 







 .



𝑥 100% (3)

3 RESULTS AND DISCUSSIONS

Production of liquefied adhesive made of oven dry

particles (MC 5%) of vascular bundles of oil-palm

stem without considering position on the stem

resulted yield 21% with very high viscosity. This

value was lower compare to previous work of

Esteves et al. (2019) who made liquefied adhesive

using bark and branches of eucalyptus tree. They

have been obtained yield of 62% and 48%,

respectively. This was probably because of different

solvent used. In converting parts of eucalyptus,

mixture of glycerol and ethylene glycol was used as

solvent while in this work phenol was used.

This type of adhesive is suitable only for making

bond-line by spreading technique such as for

plywood making. However, for spraying application

likewise for particleboard or fibreboard production,

it is impossible. The viscosity was too high thus the

adhesive could not through-out nozzle of spray gun.

Therefore, solvent for lowering the viscosity was

needed. In this study, we used commercial thinner

for lowering the viscosity of liquefied adhesive since

water as polar solvent was not capable to dissolve

the liquefied adhesive.

Basic properties of this adhesive was summarized

in Table 1 as follow:

Table 1. Properties of Liquefied Adhesive Made of Oil-

Palm Stem

Properties Resul

Standar

Colo

Brown-

lackish

Red-

lackish

Specific

ravit

1.26 1.165-1.200

Solid content

(%)

86 40-45

Viscosity (cP) 111 130-300

H7.8 10-13

Gel time

(minutes)

98 >30

Free

formaldehyde

(%)

ot detecte

3.1 Performance

According to Indonesian Standard SNI 06-4567-

1998 for PF adhesive, the colour should be red-

blackish but resulted liquefied adhesive showed

brown-blackish. Either peculiar granule or dust has

not been found in this adhesive. The brown colour

indeed originated from lignin content from oil-palm

particle. Works of Risnasari & Ruhendi (2006) and

Production and Properties of Liqueﬁed Oil-palm Stem Adhesive

109

Widiyanto (2011) in making liquefied adhesive

made from wood (teak, keruing and agathis) and

mixture of rubber wood and bamboo, respectively,

resulted in black colour. Lignin content in wood may

vary among species of woody plants, some of them

could reach 30% (Campbell & Sederoff, 1996) but

only around 20% within vascular bundles of oil-

palm stem (Nuryawan et al., 2012).

3.2 Specific Gravity

Specific gravity (SG) of resulted liquefied adhesive

was 1.26. This value was little out of range within

the standard (1.165-1.200) although previous works

on liquefied adhesive exhibited either higher or

lower values, for instances 1.23-1.25 (Risnasari &

Ruhendi, 2006) and 1.153 (Widiyanto, 2011)

depended on the raw materials used. Higher value

of SG was more than one (>1) means the liquefied

adhesive sinks down within water.

3.3 Solid Content

Solid content was percent solid after evaporation of

liquid and volatile materials. Liquefied adhesive in

this work showed 86%. This value was higher than

that of standard with required only 40-45%.

However, comparing with other adhesives such as

isocyanate, this value was still lower. Isocyanate has

98-99% solid and indeed it derived from petroleum

based (Nuryawan & Alamsyah, 2019).

3.4 Viscosity

It was impossible for measuring viscosity of this

liquefied adhesive because of too viscous. Therefore

an attempt for lowering the viscosity by mixing with

commercial thinner was carried out with ratio of

liquefied adhesive and thinner about 1:0.8.

Generally, application of solvent for making

liquefied adhesive, so called solvolytic, has been

done in the early stage of liquefaction. But in this

work, both in the early and final stages, addition of

solvent was carried out. The final viscosity of

liquefied adhesive was 111.23 cP close to the range

of standard which required 130-300 cP. This

viscosity enabled spraying application for producing

particleboard or fiberboard.

3.5 pH

The acidity of liquefied adhesive tends to alkaline

about 7.8. This condition was influenced by addition

of NaOH at the final stage of liquefaction. This

condition was also beneficial to substrate or adherent

for surface cleaning (via dissolve the existing

contaminant) and to wood structure for swelling;

thus it enhanced the penetration of adhesive used

(Risnasari & Ruhendi, 2006).

3.6 Gel Time

As the gel time increase, the life use of the adhesive

is longer. Liquefied adhesive in this experiment

needed 98 minutes for hardening or curing. This

value is in accordance with the standard which

required more than 30 minutes. Addition of liquefied

adhesive into commercial resin adhesive lengthen

the gel time (Kunaver et al., 2010).

3.7 Free Formaldehyde

In this experiment, free formaldehyde was not

detected. After HCl titration, there was no colour

alter which indicated there was no free

formaldehyde.

4 CONCLUSIONS

Liquefied adhesive made of vascular bundle of oil-

palm stem has been successfully synthesis.

Properties of this adhesive generally fulfilled the

standard excluding the viscosity. This study was the

first attempt lowering viscosity after synthesis by

mixed with commercial solvent (thinner) for proper

spraying in order to produce particleboard or

fibreboard.

ACKNOWLEDGEMENTS

This research was financially supported by

Directorate of Higher Education (DIKTI),

Ministry of Research, Technology and

Higher Education of the Republic of Indonesia,

under The 1

year of Fundamental Research Scheme

of financial year of 2019-2021 to AN.

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