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Eur. J. Wood Prod. (2011) 69:27–36 DOI 10.1007/s00107-009-0394-1 O R I G I N A L S · O R I G I N A L A R B E I T E N Physical and mechanical properties of oriented strand lumber made from an Asian bamboo (Dendrocalamus asper Backer) Pannipa Malanit · Marius C. Barbu · Arno Frühwald Received: 17 March 2009 / Published online: 7 January 2010 © Springer-Verlag 2010 Abstract The study was conducted to determine the Physikalische und mechanische Eigenschaften physical and mechanical properties as follows: modulus von Furnierstreifenholz (OSL) aus einer asiatischen of rupture, modulus of elasticity, internal bond, thickness Bambusart (Dendrocalamus asper Backer) swelling and water absorption of oriented strand lumber (OSL) made from the Asian bamboo Dendrocalamus asper Zusammenfassung Ziel der Studie war die Bestimmung Backer. Thirty-six lab boards were produced from these folgender physikalischer und mechanischer Eigenschaften bamboo strands with two manufacturing parameters vary- von Furnierstreifenholz (Oriented Strand Lumber -OSL) aus ing, i.e., four resin types (MF, MUPF, PF, and pMDI) and der asiatischen Bambusart Dendrocalamus asper Backer: three levels of resin content (7, 10, and 13%). The results Biegefestigkeit, Elastizitätsmodul, Querzugfestigkeit, Di- indicate that OSL made from bamboo strands exhibits ckenquellung und Wasseraufnahme. Im Technikum wurden superior strength properties compared to the commercial 36 Platten aus Bambusflachspänen (Strands) hergestellt, products made from wood for the building sector. The resin wobei zwei der Herstellungsparameter, d. h. Bindemittel- type has a significant effect on board properties. More- typ und -anteil, variiert wurden. Verwendet wurden vier over, all properties of the board improve generally with verschiedene Bindemittel (MF, MUPF, PF und pMDI) in increasing resin content. With regard to the internal bond, jeweils drei verschiedenen Beleimgraden (7, 10, 13%). Die bamboo-based OSL shows less strength than wood-based Ergebnisse zeigen, dass OSL aus Bambusstrands bessere boards. The best results were obtained by using 13% pMDI Festigkeitseigenschaften aufweist als aus Holz gefertigte, content at 750 kg/m3 density. kommerziell erhältliche Produkte für den Baubereich. Der Bindemitteltyp hat einen signifikanten Einfluss auf die Plat- teneigenschaften. Generell verbessern sich die untersuchten Eigenschaften mit der Erhöhung des Bindemittelanteils. Die Querzugfestigkeit von OSL aus Bambus ist geringer als die von holzbasierten Platten. Die besten Eigenschaften wurden mit dem Einsatz von 13% pMDI bei einer Rohdichte von P. Malanit () 750 kg/m3 erzielt. Walailak University, School of Engineering and Resources, 80160 Nakorn Sri Thammarat, Thailand e-mail: mpannipa@wu.ac.th 1 Introduction M. C. Barbu “Transilvania” University Brasov, Over the past decade, the demand for wood composites as Faculty for Wood Industry, building material has continuously increased. At the same Brasov, Romania time, the quantity and quality of wood resources, from the A. Frühwald forest, as a raw material for this application have been de- University of Hamburg, Department of Wood Science, clining. Consequently, the search for alternative or substitute Leuschnerstr. 91, 21031 Hamburg, Germany materials in place of wood has come into focus. 1 3
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28 Eur. J. Wood Prod. (2011) 69:27–36 Bamboo (Bambusoideae sp.) is a non-wood lignocel- were analyzed. The product properties were compared with lulosic material that has received increasing attention as standard requirements and commercial products like OSB. alternative raw material for use in the manufacture of paper and wood composites in the late 20th century. The main advantages of bamboo are its fast growing nature and 2 Materials and methods better mechanical properties when compared to other wood species. It has traditionally been used for housing construc- 2.1 Materials tion, furniture manufacture and articles for daily life in Asian and Latin American countries. In recent years, bam- Three-year-old bamboo culms from bamboo plantations boo has gained greater interest as substitute material in place located in Nakorn Sri Thammarat, South of Thailand were of wood because of the global shortage of forest resources. used as raw material for the prototype bamboo-boards. During recent years, several researches have contributed These bamboos have an average culm length of 19 m, and to understand the bamboo properties and improve pro- a culm-wall thickness in the range of 6–27 mm. The average cessing technologies for wider use. Numerous researches specific gravity at 12% MC is 0.7. have evaluated the properties of bamboo-based composites, Four exterior adhesives were used in this research: especially engineering composite products, and regarded melamine-formaldehyde (MF), melamine urea phenol the effective use of bamboo for various products such as formaldehyde (MUPF), phenol formaldehyde (PF), and plywood (Chen 1985), oriented strand board (OSB) (Lee isocyanate (pMDI). The MF resin (13H560) was supplied et al. 1996, 1997; Sumardi et al. 2007, 2008), waferboard by Dynea. The MUPF resin (KML 534) was obtained from (Zhang 2001), zephyr board (Nugroho and Ando 2000) and BASF. The PF resin (Bakelite 1279 HW) was supplied by laminated bamboo lumber (Nugroho and Ando 2001). They Hexion Specialty Chemicals. The pMDI resin (Suprasec® showed that bamboo is able to provide high quality engi- 5025) was provided by Huntsman. Their properties are neering composite products. Therefore, bamboo could be presented in Table 1. proposed as an alternative material for the manufacture of structural composite lumber (SCL) such as oriented strand 2.2 Strand processing lumber (OSL). OSL is a wood-strand based composite with a primar- Strands were made from bamboo culms in the green state ily orientation along the length of the member. The thick- with a culm-wall thickness above 12.5 mm, as presented ness of the strand should not exceed 0.635 mm and the av- in Fig. 1a. The nodes were removed before stranding. No erage length should be between 75 and 150 times that of attempt was made to remove the epidermis of the bamboo the least dimension (ICBO 2002). OSL is a concept that culms. The culms were crosscut into 140 mm long segments utilizes similar technologies and processes to that of OSB. and subsequently sliced into half, as presented in Fig. 1b. OSB is primarily used in panel applications, such as roofing Stranding was carried out on a CAE 6/36 laboratory disc and sheathing, while OSL is developed for the use as struc- flaker. Machine conditions were set as follows: counter- tural member including beams and columns. It is the newest knife angle of 60 degrees, knife projection of 0.736 mm product of the SCL family, and markets are still under de- and scoring-knife distance of 140 mm, respectively. Target velopment. Strength properties make it a highly competitive strand dimensions were 140 mm long, 0.7 mm thick, and alternative to traditional lumber and will become an impor- 12.5–20 mm wide, as presented in Fig. 1c. Strands were tant forest based product in the future (Bowyer et al. 2003). then screened via a Gilson Screen (Model TM-4) on The objective of this research was to determine the suit- a 12.5 mm screen-opening size. Strands that passed through ability of a wide spread Asian bamboo type, Dendrocala- the 12.5 mm screen-opening size in the classifier and mus asper Backer as a raw material for the manufacture of remained in the pan were considered as fine fractions, as OSL. Its physical and mechanical properties with respect to presented in Fig. 1d. Then all strands were dried in a 70°C the two processing parameters (resin type and resin content) rotary dryer to a moisture content of less than 2%. Table 1 Some properties of the used resins Properties Resin types Tabelle 1 Einige Eigen- MF MUPF PF pMDI schaften der eingesetzten (Prefere 13H560) (BASF KML 534) (Bakelite 1279HW) (Suprasec® 5025) Bindemittel Appearance Pale liquid Pale brown liquid Red brown liquid Liquid brown Solids content (%) 62.5 64 ± 1 48 – pH at 20◦C 9.73 9.3–9.8 8.5–10.5 – Viscosity (mPa s) 100–150 150–400 650–700 180–240 1 3
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Eur. J. Wood Prod. (2011) 69:27–36 29 time following the suggestions of the glue supplier, as presented in Table 2. 2.4 Board properties testing The lab boards were machined into test specimens and placed in a conditioning room maintained at 65% RH and 20°C for 4 weeks until constant weight was attained. Thirty-six specimens for each parameter combination were determined as follows: • Thickness swelling (TS) and water absorption (WA) with the dimensions of 50 × 50 mm2 were immersed in water at 20°C for 24 h in accordance with EN 300 (1997) and ASTM D 1037-97 (1997) respectively. • Three-point static bending tests for modulus of rupture Fig. 1 Bamboo type Dendrocalamus asper: a culm cross section, (MOR) and modulus of elasticity (MOE) with the dimen- b internodes with epidermis, c flaked strands, d graded and dried sions of 50 × 322 mm2 were performed in accordance strands with ASTM D 5456-99 (1999) using a 50 kN FRANK Abb. 1 Bambus Dendrocalamus asper a Querschnitt durch den universal testing machine; Halm, b Internodien mit Epidermis, c Mittels Messerringzerspa- ner hergestellte Flachsp¨ane (Strands), d Sortierte und getrocknete • Internal bond (IB) with the dimensions 50 × mm2 was Strands measured in accordance with EN 300 (1997). Effects of resin type and resin content on the properties of the boards were evaluated by analysis of variance at the 0.01 2.3 Board manufacturing level of significance. Duncan’s Range tests were conducted to determine significant differences between mean values. Bamboo-based OSL with target density of 750 kg/m3 were manufactured using laboratory equipment based on four resin types and three levels of resin content. Each resin 3 Results and discussion was mixed following the supplier’s suggestion and spread onto the strand using an in-house-made paddle-type blender The average values of the physical and mechanical proper- with a drum diameter of 62 cm, 100 cm length at 45 rpm ties of the bamboo-based OSL are summarized in Table 3. for 20 min. To ensure uniform glue distribution, the optimal The analysis of variance result and Duncan’s Range compar- conditions of rotation rate, retention time in the blender and ison for the physical and mechanical data of bamboo-based amount of furnish for one-glue application were determined OSL is illustrated in Table 4. by pretests. The glued strands were spread by hand into a forming-box with the dimensions of 800 × 300 mm2 3.1 Physical properties and oriented parallel in one direction. After forming, mats were transferred to a single-opening hydraulic lab hot press The physical properties of bamboo-based OSL were inves- (60 × 80 cm2 Siempelkamp press) and pressed into boards tigated as specific gravity, thickness swelling and water ab- at a nominal thickness of 16 mm. In this study, 36 boards sorption. They were compared with the commercial product were produced by employing a pressing temperature and (OSB/3 ISO/EN). These values are graphically presented in Table 2 Pressing conditions used in this study for each Resin type Hardener Mat moisture Pressing Pressing time resin content (%) temperature (◦C) (s/mm) Tabelle 2 Verwendete Press- parameter je Beleimtyp MF 3% Ammonium 9 210 12 nitrate MUPF 3% Ammonium 9 190 16 nitrate PF 6% Potassium 14 190 12 carbonate pMDI − 6 220 10 1 3
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