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Electronic Journal of Polish Agricultural Universities (EJPAU) founded by all Polish Agriculture Universities presents original papers and review articles relevant to all aspects of agricultural sciences. It is target for persons working both in science and industry,regulatory agencies or teaching in agricultural sector. Covered by IFIS Publishing (Food Science and Technology Abstracts), ELSEVIER Science - Food Science and Technology Program, CAS USA (Chemical Abstracts), CABI Publishing UK and ALPSP (Association of Learned and Professional Society Publisher - full membership). Presented in the Master List of Thomson ISI.

Volume 13
Issue 1
Topic:
ELECTRONIC
JOURNAL OF
POLISH
AGRICULTURAL
UNIVERSITIES
. , EJPAU 13(1), #08.
Available Online: http://www.ejpau.media.pl/volume13/issue1/art-08.html


 

ABSTRACT

Within this study the applicability of complete substitution of wood chips in the core layer of particleboards using straw particles of an evening primrose species (Oenothera paradoxa Hudziok) was investigated in boards resinated with UF, MUPF and PMDI resins. Conducted investigations showed that complete replacement of wood chips with straw particles from an evening primrose species in the core layer of boards, irrespective of the type of the binding agent, causes a reduction of their strength and water resistance. However, the application of an adequately high resination rate, dependent on the type of adhesive resin, makes it possible to manufacture boards meeting the requirements of a respective standard EN – 312.

Key words: .

INTRODUCTION

Wood as a renewable material seemed to be the best source of raw material for wood industry. However, a boom on the furniture market and in the construction business, particularly single family housing, and at the same time increased demand for wood as a source of biomass in the energy sector have led to its deficit and problems with supply in wood industry [16]. For this reason, it is crucial to provide rational and economical management of wood and its wood waste, as well as investigate potential application of its substitutes. Initially industrial wood waste in the form of sawdust and chips were used. In board industry also non-wood plant origin materials were also applied, such as flax shives, hemp shives, jute, cotton and bagassa stems. When searching for alternative wood substitutes both in wood-based board industry and in the energy sector, it was decided to focus on wastes of annual oil plants, legumes, and particularly cereal straw, so far used as litter or added to fodder for farm animals, or after ploughing in or burning used as a natural fertilizer. It is estimated that in the EU countries there are at present approx. 140 million tons excess straw, of which approx. 8 million tons are in Poland. Thus, new methods are being searched for to manage this material using modern industrial technologies, especially in processing of lignocellulose materials [10,11,13,14,19]. One of the presently applied methods is to use straw in heat engineering as an energy carrier. For this purpose, straw of practically all types of cereals, rapeseed, buckwheat as well as corncobs may be used. The application of straw for energy purposes requires its processing to fuel form, such as briquettes or pellets, which leads to improvement of their calorific value, uniformity of fuel structure, increased bulk density and it also facilitates the combustion process [21]. Such energy is consumed by transport, agriculture and, first of all, construction business [2]. It is of interest that at the time of state-of-the-art technologies, one of the methods to utilize straw is to build houses in the straw-bale technology, stemming from the traditional mud housing technology of the 19th century, being continued in a modern form. In this technology, after wall structures are erected from poles nailed together, wall modules are constructed, filled with ballots of pressed straw [9,17,20]. In the construction of such houses, all types of straw may be used, except for barley straw. These houses meet all currently binding housing standards and there are thousands of such houses worldwide, mainly in the USA, Canada, Sweden, Germany as well as Poland. It results from literature sources on the subject that serious competition for the energy sector in straw processing may come from board industry, particularly particleboard manufacture. In many research centres studies are conducted in order to develop such manufacturing conditions of straw boards so that their properties may be possibly closest to those of particleboards. It results from collected data that at the selection of an appropriate type and amount of a binding agent, it is possible to manufacture boards, in which wood chips may be completely or partially replaced with straw particles [1,3,4,5,6,7,8,12,15,18]. Properties of these boards meet the requirements of respective standards and may be applied in furniture industry and construction engineering. However, a serious drawback in straw processing is its seasonal supply and, thus, a lack of constant deliveries to support the production process. Straw is obtained during only 4–6 weeks within a year. As potential solutions to this problem are being searched for, the authors of this study focused on waste of annual plants which are harvested at a different time than during cereal harvest. Such plants include e.g. an evening primrose species Oenothera paradoxa Hudziok, which is harvested in September. In the literature there are no statistical data concerning the acreage under evening primrose in Poland; there are only fragmentary data from particular cultivation areas that are available. Detailed statistical data refer mainly to the whole acreage under herbaceous plants. In the last several years, however, a growing interest of cosmetic and pharmaceutical industry in the herbaceous plants, such as evening primrose, has been observed; this may probably lead to a significant increase in acreage under cultivation of this plant. From the point of view of its industrial application, an advantage of evening primrose is its considerable annual growth increment of 100–150 cm and easy cultivation, as the plant provides good yields on poor and sandy soils and is drought resistant. It is grown to produce oil from seeds, which is rich in essential unsaturated fatty acids and used with increasing frequency in herbal medicine, pharmaceutical, cosmetics as well as food industry. At the harvest of evening primrose seeds straw remains, which is treated as worthless waste with no potential application. Information provided directly by the producer shows that approx. 2.5 to 3.0 tons of straw can  be obtained from 1 ha cultivation. Harvesting of the evening primrose straw can be done with use of exactly the same farming machinery as in case of cereal harvest. Thus, the aim of this study was to investigate whether complete replacement of wood chips in the core layer of particleboard is feasible using evening primrose straw, applying resin adhesives, commonly used in board manufacture, as binding agents.

MATERIALS AND METHODS

Boards were manufactured using pine chips and evening primrose straw particles, whose fractional composition determined by means of screen analysis is shown in Fig. 1.

Fig. 1. Fractional composition of wood chips and evening primrose particles in the core layer of particleboards

Resin adhesives commonly used in the production of chip boards were applied as binding agents, i.e. urea-formaldehyde (UF), melamine-urea-phenol-formaldehyde (MUPF) and isocyanate (PMDI) resins. Their characteristics are given in Table 1.

Table. 1. Properties of resin adhesives used in experiments

Type of test

Unit

Properties of resin

UF

MUPF

PMDI

Density

g/cm3

1.316

1.298

-

Viscosity

mPaˇs

748

516

250

Apparent dry matter content

%

72

63.5

100

Miscibility with water

-

1.6

1.0

-

Gel time at 100ºC

s

90

83

-

pH

-

8.00

9.35

-

Acid value

mg/kg

-

-

1218

NCO group content

%

-

-

30.9

In order to determine physico-mechanical properties of boards with the core layer from evening primrose straw particles (in relation to chip boards), three-layer boards with the 1:2 mass fraction of outer layers to the core layer and a density of 700 kg/m3, thickness of 19 mm were manufactured on a semi-commercial scale, applying the following parameters:

Manufactured boards were tested in terms of their physical and mechanical properties according to respective standards:

RESULTS AND DISCUSSION

Testing results of mechanical properties of boards with the core layer of wood chips as well as evening primrose particles, depending on resination rate and the type of binding agent applied, are given in Table 2. It results from the presented data that, irrespective of the type of the lignocellulose material and adhesive resin, the strength of manufactured boards increases with an increase in resination rate. The smallest changes in respective values were recorded when measuring bending strength and modulus of elasticity, particularly in case of particleboards resinated with UF. An increased bending strength and modulus of elasticity in these boards, at a maximum resination rate (12%) was as little as 6–9%, while in boards with added evening primrose straw it was over 13%. At the identical amount of MUPF resin, an increase in MOR and MOE values was approx. 15% for boards with the core layer of both wood chips and evening primrose particles. In case of PMDI an increase in resination rate from 5% to 8% resulted in a 20% increase in rigidity of particleboards, while in boards with a proportion of straw it was by only 10%. A lack of a distinct dependence between the type of raw material and binding agents and values of MOR and MOE results from the fact that manufactured boards were of layer structure, in which the core to a considerable degree determines bending strength of boards and their modulus of elasticity. An increase in resination rate of particleboards to a considerable degree affects internal bond of boards. The biggest increment in this value was observed for particleboards resinated with 12% MUPF resin (by approx. 130%). For the other resins, at an identical resination rate, an increase in IB was 50% for UF and 40% for PMDI. In case of boards with an addition of evening primrose particles resinated with MUPF and UF this strength property increased by 70% and 75%, respectively, and it was by only 15% for PMDI.

Table. 2. Properties of boards with the core layer from wood chips and with particles of evening primrose, depending on the amount and type of binding agent

Kind of materials

Z*
%

MOR

MOE

IB

N/mm2

UF

MUPF

PMDI

UF

MUPF

PMDI

UF

MUPF

PMDI

pine particles

5

20.6

2880

1.00

   

1.4**

   

145

   

0.02

6

16.2

14.0

22.1

2920

2750

3360

0.46

0.40

1.13

2.01

1.50

1.81

187

262

170

0.03

0.03

0.05

7

22.2

3430

1.20

   

2.01

   

98

   

0.06

8

16.3

16.7

22.2

3070

2940

3480

0.52

0.73

1.40

1.12

2.13

0.79

203

296

177

0.04

0.06

0.05

10

16.7

16.8

3100

2860

0.59

0.85

2.61

0.76

 

108

53

 

0.04

0.08

 

12

17.2

18.3

3190

2940

0.69

0.92

0.75

1.70

 

89

190

 

0.02

0.07

 

evening primrosewaste

5

17.4

2710

0.75

   

1.23

   

132

   

0.03

6

14.3

13.9

18.6

2660

2370

2800

0.29

0.36

0.79

0.59

1.08

1.69

79

123

150

0.01

0.02

0.06

7

18.8

2880

0.80

   

1.12

   

168

   

0.06

8

15.2

14.05

19.0

2710

2370

2960

0.34

0.51

0.90

2.03

1.41

1.40

159

200

174

0.03

0.09

0.05

10

15.7

14.3

2720

2280

0.41

0.57

0.79

0.95

 

145

128

 

0.05

0.04

 

12

16.6

16.0

2750

2430

0.51

0.61

1.31

1.50

 

96

192

 

0.01

0.05

 
*Z – resination rate of core layer of board, ** – standard deviation

When analyzing collected results it was found that strength of boards with the core layer made from evening primrose straw particles for a given resination rate was lower than for chip boards. It was estimated that at the highest resination rates, internal bond of chip boards was by 25% higher for UF and 35% for MUPF and PMDI resins, while bending strength was by 15% higher for MUPF and PMDI, and it was slightly higher, i.e. by only 3.5%, for UF. These differences, particularly in case of internal bond, are probably caused by the less porous surface of evening primrose straw than that of wood chips, which hinders the penetration of adhesive resin inside the straw particles. As a consequence, binding of the core layer, which is to a considerable degree responsible for board strength, is weaker. However, it may be stated that boards with the core layer with added evening primrose straw particles, even at the lowest resination rate (6%) for UF resin, fully meet the requirements of the respective standard EN 312 for general purpose boards used under dry conditions (type P1). In order to meet the requirements for boards to be used in interior design, including furniture (type P2), it is necessary to increase the amount of UF resin to 8%. When applying higher resination rates it is also possible to manufacture boards capable of bearing loads of type P4 (resination rates of 8–10%), or even type P6 (12% resination rate), used under dry conditions. Boards with the core layer made from wood chips and an only 8% resination rate with MUPF exhibited properties required for boards P5 (boards bearing loads to be used under humid conditions), while in order to obtain similar results in case of boards with an addition of evening primrose straw it is necessary to increase their resination rate to 12%. Chip boards manufactured with a 6% proportion of PMDI resin exhibited strength comparable to that of boards with enhanced load bearing capacity under humid conditions (type P7), whereas boards containing particles of evening primrose straw even at a maximum resination rate (8%) with PMDI exhibited strength corresponding to boards P5.

The basis for the evaluation of water resistance of manufactured boards depending on the amount and type of adhesive resin was their swelling in thickness and absorbability after 24 h soaking in water and internal bond after the boiling test (test V-100). It results from data contained in Table 3 that water resistance of tested boards to a significant degree depends on the type of the lignocellulose material used in their manufacture, as well as the type and amount of the binding agent.

Table. 3. Water resistance of boards with the core layer made from wood chips and with particles of evening primrose, depending on the amount and type of binding agent

Kind of materials

Z
%

Swelling in thickness after 24 h

Absorbability
after 24 h

V-100

%

N/mm2

UF

MUPF

PMDI

UF

MUPF

PMDI

UF

MUPF

PMDI

pine particles

5

19.5

71.3

0.48

   

0.31**

   

3.02

   

0.04

6

25.8

21.9

17.2

84.7

94.1

69.8

0.01

0.52

2.30

1.57

0.60

4.12

3.52

2.60

 

0.002

0.04

7

16.1

68.0

0.56

   

0.23

   

1.99

   

0.03

8

21.6

15.8

15.2

76.6

75.7

67.0

0.16

0.62

2.45

0.65

0.21

3.25

5.37

5.23

 

0.03

0.05

10

20.8

15.1

75.4

72.2

0.20

1.31

0.84

 

1.98

3.58

   

0.03

 

12

17.1

15.6

67.7

69.3

0.23

2.01

1.13

 

3.45

7.27

   

0.05

 

evening primrose waste

5

7.5

38.0

0.05

   

1.11

   

4.74

   

0.03

6

39.3

30.7

7.5

101.8

89.8

37.1

0.01

0.06

1.76

1.65

0.70

3.68

4.23

3.71

 

0.002

0.01

7

6.9

34.0

0.08

   

0.98

   

5.45

   

0.05

8

34.0

23.8

6.6

87.5

74.5

29.0

0.03

0.09

1.58

1.94

1.23

4.10

8.20

2.31

 

0.02

0.02

10

25.5

20.1

77.6

70.6

0.05

2.00

0.93

 

2.35

8.84

   

0.01

 

12

19.5

14.9

-

59.9

59.6

0.09

163

1.05

 

6.02

10.18

   

0.02

 
*Z – resination rate of core layer of board, ** – standard deviation

It was shown that chip boards resinated with PMDI exhibited a much higher water resistance defined by their swelling in thickness and internal bond after the boiling tests than boards with a proportion of evening primrose straw. These differences were particularly evident in case of values of the V-100. Chip boards already at a 6% resination rate had values of this test at the level of boards P7, while in case of boards with the core layer containing particles of evening primrose, in order to obtain values characteristic of e.g. board P3 (boards not bearing loads to be used under humid conditions) it was necessary to increase resination rate to 7%. A similar trend was observed for boards resinated with MUPF. Chip boards at an 8% resination rate had values in the V-100 tests required for board P5, while at a proportion of resin of 10–12% it was equivalent even to P7. The maximum strength of boards with particles of evening primrose, which could be obtained at the highest resination rate for this resin (12%), corresponded to boards type P3. In turn, swelling in thickness and absorbability of manufactured boards exhibited different trends. The application of evening primrose straw in the core layer of boards resinated with PMDI resulted in a decrease in values of swelling in thickness and absorbability by 60% and 45%. This is caused by a particularly low weight by volume of evening primrose straw, which results in a situation when – in comparison to chip board – during compression of the pressed cake free spaces are reduced, which to a considerable degree reduces water penetration. Such an increase in cohesion in boards with a proportion of straw particles explains also the low value of the V-100 test, since at the resination of straw particles and wood chips with the same amount of resin, in case of straw a smaller total area of glue line is obtained, which as a consequence reduces strength of boards. A certain role is also played by the different surface structure of evening primrose straw in comparison to wood chips, as it has been mentioned earlier. Swelling in thicknesses and absorbability of boards with the core layer made from evening primrose straw resinated with condensation resins at lower resination rates (6–10%) were higher than in boards made from wood chips only; however, when applying a 12% resination rate these differences were not so evident and the obtained values were comparable. However, we need to stress the fact that swelling in thickness of boards resinated with MUPF, irrespective of resination rate and the type of the raw material, considerably differed from the value of 13% required by the standard EN 312 for boards P3. This was probably caused by the fact that at the manufacture of these boards hydrophobic agents were not applied.

Hygienic standard of boards manufactured only from wood chips as well as those containing particles of evening primrose, resinated with UF and MUPF, was determined by measuring the content of formaldehyde with the perforation test (Fig. 2 and 3). As it could have been expected, an increase in the amount of both types of adhesives in boards, irrespective of the composition of the core layer, results in an increase in formaldehyde content; however, the presence of evening primrose straw in boards effectively reduces its level.

Fig. 2. Formaldehyde content in boards manufactured from evening primrose and wood chips depending on resination rate of UF resin

Fig. 2. Formaldehyde content in boards manufactured from evening primrose and wood chips depending on resination rate of MUPF resin

CONCLUSIONS

Conducted analyses showed that complete replacement of wood chips with particles of evening primrose straw in the core layer of boards, irrespective of the type of applied binding agent, results in a decrease of their strength and water resistance. However, the application of an adequately high resination rate, depending on the type of adhesive resin, makes it possible to manufacture boards meting the requirements of the respective standard EN 312, i.e.:


REFERENCES

  1. Boquillon N., Elbez G., Schönfeld U., 2004. Properties of wheat straw particleboards bonded with different types of resin. J. Wood Sci. 50(3), 230–235.

  2. Dermanowski S., 2003. Rośliny na cele energetyczne [Plants for energy purposes]. Biul. Inform. OBRPD w Czarnej Wodzie, 1–2, 27–32 [in Polish].

  3. Dukarska D., Dziurka D., Łęcka J., Mirski R., 2006. The effect of amounts of rape straw added to chips on properties of particle boards depending on the type of bonding agent. EJPAU, Wood Technol. 9(3) #12, www.ejpau.media.pl.

  4. Dziurka D., Mirski R., Łęcka J., 2005. Properties of boards manufactured from rape straw depending on the type of the binding agent. EJPAU, Wood Technol. 8(3) #5, www.ejpau.media.pl.

  5. Grigoriou A.H., 1998. Straw as alternative raw material for the surface layers of particleboards. Holzforsch. u. Holzverwert. 50(2), 32–34.

  6. Grigoriou A.H., 2000. Straw-wood composites bonded with various adhesive systems. Wood Sci. Technol. 34: 355–365.

  7. Girgoriou A.H., Passialis C., Voulgaridis E., 2000. Experimental particleboards from Kenaf plantations grown in Greece. Holz a. Roh Werkst. 58, 309–314.

  8. Guler C., Ozen R., 2004. Some properties of particleboards made from cotton stalks (Gossypium hirsitum L.). Holz a. Roh Werkst. 62, 40–43.

  9. Goodhew S., Griffiths R., Woolley T., 2004. An investigation of the moisture content in the walls of a straw–bale building. Build. and Environm. 39(12), 1443–1451.

  10. Hiziroglu S., Jarusombuti S., Fueangvivat V., Bauchongkol P., Soontonbura W., Darapak T., 2005. Properties of bamboo-rice straw-eucalyptus composite panels. Forest Prod. J. 55(12), 221–225.

  11. Mengeloglu F, Karakus K., 2008. Thermal degradation, mechanical properties and morphology of wheat straw flour filled recycled thermoplastic composites. Sensors Basel 8(1), 500–519.

  12. Mo X.Q., Cheng E., Wang D., Sun S., 2003. Physical properties of medium-density wheat straw particleboard using different adhesives. Ind. Crops and Prod. 18, 47-53.

  13. Munawar S.-S., Umemura K., Kawai S., 2008. Manufacture of oriented board using mild steam treatment of plant fiber bundles. J. Wood Sci. 54(5), 369–376.

  14. Nicewicz D., Pawlicki J., Starecki A., Sosińska K., Zado A., 2000. Ocena przydatności krajowych gatunków słom zbożowych do wytwarzania płyt wiórowych [Assessment of suitability of straw from native cereal species in manufacture of particleboards]. 14th Scientific Conference of the Faculty of Wood Technology, Warsaw University of Life Sciences "Wood – Material of All Ages", Warszawa 13–15.11.2000, 185–192 [in Polish].

  15. Pawlicki J., Nicewicz D., Sosińska K., Zado A., 2001. Straw-wood boards. Ann. Warsaw Agricult. Univ. For. and Wood Technol. Special number I, 152–155.

  16. Ratajczak E., 2008. Drewno źródłem materiałów i energii [Wood as a source of materials and energy]. Gospodarka Materiałowa i Logistyka 7, 11–16 [in Polish].

  17. Straub J, Schumacher C., 2003. Monitoring the hydrothermal performance of straw bale walls, URL: www.ecobuildnetwork.org/strawbale.htm.

  18. Yang H.-S., Kim D.-J., Kim H.-J., 2003. Rice straw-wood particle composite for sound absorbing wooden construction materials. Biores. Technol. 86, 117–121.

  19. Yang H.-S., Kim D.-J., Lee Y.-K., Kim H.-J., Jeon J.-Y., Kang C.-W., 2004. Possibility of using waste tire composites reinforced with rice straw as construction materials. Bioresource Technol. 95(1), 61–65.

  20. www.biobudownictwo.org

  21. www.pl.scanbio.pl

Accepted for print: 16.02.2010



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