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Properties of oil heat-treated four year-old tropical bamboo Gigantochloa Levis.

INTRODUCTION

Declining in the supply of natural resources from the forests has forced the timber industry to seek for an alternative material to replace wood. Among the top contender considered is bamboo. Bamboo being a fast growing species possesses one of the most highest strength properties of the wood materials [1], [2]. The strength of bamboo, however, decline with time. It is susceptible to fungal and insect attack [1], [3], [4]. Bamboo deteriorates rapidly if not treated with preservatives [1], [5]. The used of chemical in bamboo has long been recognized as necessary and essential if they are to consider for utilization in furniture and construction industry [1]. The used of chemical, however, is not always effective as bamboo being a monocot species is not easily treated [5].

The heat treatment process has been studied by researchers especially in the tropical regions where bamboo found in abundant [6], [7], [8], [9], [10]. This technique was found to be effective in enhancing the durability of bamboo against insects and fungi. However, the effectiveness of this process is widely depending on the system used and type of oil used as the heating medium. Oil with a high boiling point would be preferred. Several earlier studies on the heat treatment process using diesel and palm oil as a heating medium carried out by Wahab et al. [11], [9]. The diesel heat-treated bamboo was found to be effective for an indoor usage [12]. The colour and durability of woody materials especially in the juvenile stage also improved [13]. The used of heat treatment can eliminate preservatives usage in the bamboo-based industry.

This study determines changes in Gigantochloa levis that underwent the heating treatment with palm oil as its heating medium. Properties such as the physical, strength and durability of the bamboo are studied.

MATERIALS AND METHODS

Cultivated Gigantochloa levis or locally known as buluh beting used in this study. The bamboo culms harvested from cultivated clumps in villages around the Jeli district, Kelantan, Malaysia. Thirty-two (32) culms of mature age of 4-year-old harvested randomly from selected clumps. All culms used in this study possess diameters ranging from 8 to 10 cm. For practical and uniformity for sampling purposes only internodes 5, 6 and 7 used.

After harvesting, all the culms took immediately to a woodworking workshop in UMK for further process. Two sets of samples investigated. The first set consists of bamboo samples in green condition with an average moisture content of 65% and the second set consisting air-dried bamboo having a moisture content of 14%.

The heat treatment process uses a stainless steel tank with palm oil as the heating medium. The palm oil selected as it is organic in nature, readily available and possesses a high boiling point. The palm oil poured into the tank and heated up using a stove to a temperature of 80[degrees]C. The bamboo then submerged in the heated oil by placing them in a metal cage. The bamboo samples taken out from batches started with the treatment of 140[degrees]C with an interval of 30, 60 and 90 minutes of exposure duration. Later followed by treatment of 180oC and 220oC for the same length. The treatment technique developed by Wahab et al. [11], [7], [8], [15] used with slight adjustments.

Physical Studies:

The method employed in this investigation based on ISO 22157 [16]. Samples cut from culms at internodes 6 with dimensions 25 mm x 25 mm x culms wall thickness. Five (5) replicates used in this study. They weighed and dried in an oven at 103[+ or -] 2[degrees]C for 48 hours until a constant weight attained. The samples then cooled for half an hour in desiccators before re-weighing.

Basic Density:

Samples of 10 mm x 30 mm x thickness of culms wall obtained from the middle portion of internodes 6. Five replicates used in the investigation. The samples oven dried for 48 hours at 103+2[degrees]C until a constant weight attained. The basic density of bamboo obtained using the values of the bamboo oven dry weight per the green bamboo volume.

Mechanical Studies:

The shear, parallel compression to the grains strengths to grain and static bending conducted using a Universal Testing Machine. Preparation of the test samples and methods made according to ISO 22157 [16]. All testing blocks conditioned to 12% moisture content before testing. This tests performed by placing the test blocks in a conditioning chamber under controlled relative humidity of 55% and temperature at 25oC for a week.

All bamboo for testing taken from the middle portion of internodes 6. The samples tested varies in sizes depending on the type of test conducted;

1). Shear tests parallel to the grain (40 mm x 20 mm x bamboo culms wall thickness),

2). Compression parallels to the grain (40 mm (height) x 20 mm (width) x bamboo culms wall thickness),

3). Static bending (300 mm (length) x 20 mm (width) x bamboo culms wall thickness).

Durability:

Sample size of 100 mm x 10 mm x culms wall thickness and chosen from internodes 5 and 7. Durability against biodeterioration on field tests conducted based on EN 252 [17] with adjustments.

The tested bamboo stakes buried upright completely in the ground. They installed 200 mm apart within and between rows and were distributed randomly based on randomized complete-block design. The tests monitored for 12 months. The stakes installed during the dry season. The site is located in UMK Nursery with hot and humid climate throughout the year with an average daily temperature vary from 21[degrees]C to 32[degrees]C and average rainfall of about 2540 mm. Assessment on the bamboo samples based on the percentage of weight loss of each stake.

RESULTS AND DISCUSSION

Gigantochloa levis culms abled to be treated using palm oil at high temperature with no evident of the defects. The color appearance of tested the bamboo treated varied considerably from light yellowish brown to dark brown.

The results on moisture content and basic density tabulated in Tables 1 and 2. The final moisture content ranged 4.6 to 6.6% and 4.4 to 7.6% for green and air-dried bamboo respectively. There was a change range from 91.2 to 93.9% in moisture content in the green bamboo and 38.7 to 62.7 % in the air-dried bamboo. The analysis of variance (ANOVA) (showed in Table 7) showed differences in moisture content between the treatment temperature and duration. Significant differences observed in the heat-treated bamboo for the moisture content between green, air-dried bamboo, and durations of treatment [12]. The green bamboo experiences higher loss in moisture compared to the air-dried bamboo. These may be due to ease of moisture flow out from the bamboo. The air-dried bamboo culms have undergone a drying process which may cause low moisture gradient, and more energy needs absorbed.

No. of replicates = 5

Increases in the basic densities occurred between 5.4 to 17.3% for the green bamboo, and 3.4 to 23.9% in the air-dried bamboo by the heat treatment process. The additional increases in density might be due to some of the oil that able to penetrate the cell wall and influence the total weight of the sample [13]. The significant difference observed in the basic density values when the bamboo exposed at different treatment temperatures and durations (see Table 7).

The mechanical properties of bamboo before and after treatments tabulated in Tables 3, 4 and 5. The MOE changed from 7.5 to 32.3 % for green and 6.3 to 25.8 % for air-dried bamboo in the bending strength. The MOR reduced between 3.9 to 23.3 % for green and 4.0 to 16.9 % for air-dried bamboo.

ANOVA for bending strength shown in Table 7. Statistical analysis conducted on the treated bamboo shows that the strengths for both MOR and MOE significantly affected by treatment duration and bamboo condition at P < 0.05. Air-dried bamboo exhibits a small loss in MOE and MOR while green culms show a higher loss in MOE and MOR when subjected to higher and longer duration of the treatment.

The compression strength is reduced in the ranged between 1.1 to 4.3 % in green bamboo while for air-dried between 2.1 to 37.2 % (Table 5). The shear strength reduced in the ranged between 9.8 to 22.8 % for green and between 11.4 to 25.0% for air-dried. Both conditions show the same percentage loss. These reductions in strength after undergoing the heat treatment process showed slight better that that bamboo treated with preservatives [1]. Wahab [1] found that bamboo Gigantochloa scortechinii experienced the strength reduction between 12 to 42% after undergoing preservatives treatment.

Bamboos in natural forms possess low durability. Placed in contact with soils bamboo deteriorate rapidly due to the action of a mixed population of soil microorganisms. The bamboos treated with preservatives may still be colonized by fungi and termites although decay and the attack rates may be slower.

The results of the ground contact test on heat treated bamboo samples for a 12 months duration showed in Table 6. The fresh bamboo and rubber wood experienced weight loss of 38.7% and 46.2% respectively after undergoing a 12 months ground contact tests. The average weight losses of the heat treated bamboo vary from 13.6 - 31.3% depending on treatment temperatures and duration. Similar observation made by Wahab et al., [7], [8] in their study on durability of heat treated Gigantochloa scortechinii

Treatment duration of 90 min at 220oC produced bamboo that was more durable against fungi and termites attacked during the ground contact tests, but the bamboo too brittle as they experience high strength loss [7] [9]. This might due to changes in the chemical content of the bamboo during the heat treatment process [14]. These followed by 220oC at 60 min and 180oC at 90 min.

Conclusions:

The bamboo heat-treated at 180[degrees]C for the duration of 60 min shows an overall quality in both the physical and mechanical studies undertaken. The bamboo also exhibited high durability when tested in the 12 months ground contact tests. Dried bamboos possess better quality in term of properties compared to green bamboo after undergoing heat treatment process. The initial condition of the bamboo, as well as temperatures and duration of the heat treatment process, influence their properties after treatment. An oil-curing process greatly enhanced the durability of the bamboo. The reduction in strength of the bamboo after undergoing oil-curing process is acceptable and comparable to that bamboo treated with preservatives.

REFERENCES

[1] Wahab, R., 1998. Effect of selected preservatives on the durability of Gigantochloa scortechinii. A Ph.D. dissertation, University of London.

[2] Azmy, H.J., Mohamed, J.B. Hall, Othman Sulaiman, Razak Wahab, Wan Rashidah Wan A.B. Kadir, 2007. Quality management of the bamboo resource and its contribution to environmental conservation in Malaysia. Management of Environmental Quality: An International Journal. Vol. 18, No. 6, 2007. Pp 643-656. DOI 10.1108/1477830710826685.

[3] Liese, W., 1985. Bamboos: Biology, silvics, properties, utilization. Schriftenreihe der GTZ, 180.

[4] Wahab, R.W., S. Mahmud, K. Izyan A.S. Mohammed, R. Shafiqur, W.S. Hashim, 2015. Comparative Distribution of Chemicals in Treated Gigantochloa Scortechinii through Soaking, Vacuum Pressure, and High-Pressure Sap-Displacement. Current Research Journal of Biological Sciences 7(1): 6-10. ISSN: 2041-0778.

[5] Liese, W., 1986. Characterization and Utilization of Bamboo. In Proceeding of the Congress Group 5.04, Production and Utilization of Bamboo and Related Species, XVIII IUFRO World Congress Ljubljana, Yugoslavia, 7-21 Sep.1986. Kyoto University, Kyoto, Japan.

[6] Leithoff, H., R.D. Peek, 2001. Heat treatment of bamboo. Paper presented at the International Research Group on Wood Preservation (IRG), Nara, Japan, 20-25.

[7] Wahab, R., W.S. Hashim, S. Mahmud, M. Janshah, 2004a. Strength and durability of bamboo treated through an oil-curing process. Journal of Biological Science, 4(5): 658-663. Asian Network for Scientific Information 2004.

[8] Wahab, R., W.S. Hashim, S. Mahmud, M. Janshah, 2004b. The performance of an oil-cured tropical bamboo species Gigantochloa scortechinii in a six months ground contacts tests. Journal of Borneo Science, 16: 25-32.

[9] Wahab, R., M. Aminuddin, W.S. Hashim, S. Othman, 2005. Effect of heat treatment using palm oil on properties and durability of Semantan bamboo. Journal of Bamboo and Rattan, 4(3): 211-220 (10). International Network for Bamboo and Rattan.

[10] Wahab, R., Izyan, S. Mahmud, M.R. Sukhairi, S. Othman, A.T. Tamer, 2012. Changes in Strength and Chemical Contents of Oil Heat Treated 15-Year-Old Cultivated Acacia Hybrid. International Journal of Chemistry, 4(4): 90-100. ISSN: 1916-9701. Canadian Center of Science and Education. DOI: 10.5539/ijc.v4n2p90.

[11] Wahab, R., W.S. Hashim, M. Tarmizi, S. Othman and M. Azmy, 2002. Heat treatment technique for enhancing the resilience of bamboo. Paper presented at the Workshop on R&D and Bamboo Products Processing held at the Centre of Craft Development Kuala Pilah, Negeri Sembilan, 19.

[12]Wahab, R., K. Izyan, A.T. Tamer, S. Othman, M. Mahmud Sudin, 2011. Chemical, colour and strength changes of hot oil treatment process on 15-year-old cultivated Acacia hybrid. Current Research Journal of Biological Sciences, 3(6): 559-569. ISSN: 2041-0778.

[13] Anonymous, 2004. International Standard Organization (ISO) 22157: Bamboo - Determination of Physical and Strength Properties.

[14] Anonymous, 1989. European Standard (EN) 252: Field test method for determining the relative protective effectiveness of a wood preservative in ground contact.

[15] Izran, K., R. Wahab, A. Zaidon, F. Abood, A.R. Norhisham, 2012. The effects of oil boiling treatment on physical properties of Bambusa vulgaris var. Striata (Buluh Gading). PERTANIKA Journal of Tropical Science 35(4): 833-844. ISSN: 1511-3701.

[16] Rafidah, S., A. Zaidon, W.S. Hashim R. Wahab, A. Hanim, 2010. Effect of heat oil treatment on physical properties of Semantan bamboo (Gigantochloa scortechinii Gamble). Journal of Modern Applied Science, 4(2): 107-113. ISSN 1812-5654. Asian Network for Scientific Information.

[17] Izyan, K., R. Wahab, S. Othman, M. Aminuddin, R.A. Hanim, A.T. Tamer, H. Affendy, 2010. Enhancing colour appearances of cultivated 15 year-old Acacia hybrid through oil heat treatment process. International Journal of Biology, 2(2): 199-209. ISSN: 1916-9671. Canadian Center of Science and Education.

(1) Razak Wahab, (1) Mohd Sukhairi Mat Rasat, (1) Mazlan Mohammad, (2) Hashim W. Samsi, (2) Mohd Tamizi Mustafa and (1) Muhammad Iqbal Ahmad

(1) Universiti Malaysia Kelantan (UMK), Campus Jeli, 17600 Kelantan, Malaysia

(2) Forest Research Institute Malaysia, 52109 Kepong, Selangor, Malaysia.

Address For Correspondence:

Razak Wahab, Universiti Malaysia Kelantan (UMK), Campus Jeli, 17600 Kelantan, Malaysia E-mail: razak@umk.edu.my

Received 12 January 2016; Accepted 28 February 2016; Available online 10 April 2016
Table 1: Moisture contents (MC) heat treated bamboo at
140[degrees]C, 180[degrees]C and 220[degrees]C of green
moreover, air-dried Gigantochloa levis.

                          Green bamboo    % changed
Temperature                               from fresh
& duration               Before   After     bamboo

Control                   73.1      --        --
140[degrees]C, 30 min     75.0     6.6       91.2
140[degrees]C, 60 min     75.8     6.6       91.3
140[degrees]C, 90 min     76.7     6.3       91.3
180[degrees]C, 30 min     71.6     6.2       91.6
180[degrees]C, 60 min     75.9     5.9       92.5
180[degrees]C, 90 min     76.1     5.7       92.5
220[degrees]C, 30 min     76.7     5.6       92.7
220[degrees]C, 60 min     77.2     5.3       93.1
220[degrees]C, 90 min     74.8     4.6       93.9

                           Air-dried
                             bamboo         % changed
Temperature                                 from air-
& duration               Before   After    dried bamboo

Control                   13.1      --          --
140[degrees]C, 30 min     13.0     7.6         38.7
140[degrees]C, 60 min     12.4     7.7         40.0
140[degrees]C, 90 min     12.9     7.2         44.2
180[degrees]C, 30 min     13.3     5.7         57.1
180[degrees]C, 60 min     13.1     5.6         57.3
180[degrees]C, 90 min     13.1     5.5         58.0
220[degrees]C, 30 min     12.2     5.0         59.0
220[degrees]C, 60 min     13.4     5.1         61.9
220[degrees]C, 90 min     11.8     4.4         62.7

Table 2: Basic density (BD) of heat treated bamboo of
green and air-dried Gigantochloa levis.

                          Green bambo      % changed
Temperature                               from fresh
& duration               Before   After     bamboo

Control                   685      --         --
140[degrees]C, 30 min     665      701       5.4
140[degrees]C, 60 min     677      703       5.4
140[degrees]C, 90 min     668      711       6.8
180[degrees]C, 30 min     663      706       6.5
180[degrees]C, 60 min     668      712       6.6
180[degrees]C, 90 min     675      728       7.9
220[degrees]C, 30 min     702      771       9.8
220[degrees]C, 60 min     671      775       15.1
220[degrees]C, 90 min     664      779       17.3

                           Air-dried
                             bamboo
Temperature                                % changed from
& duration               Before   After   air-dried bamboo

Control                   707      --            --
140[degrees]C, 30 min     679      719          3.4
140[degrees]C, 60 min     680      703          5.0
140[degrees]C, 90 min     669      728          8.8
180[degrees]C, 30 min     686      763          11.2
180[degrees]C, 60 min     683      770          12.7
180[degrees]C, 90 min     608      687          13.0
220[degrees]C, 30 min     681      778          14.2
220[degrees]C, 60 min     609      707          16.1
220[degrees]C, 90 min     603      747          23.9

No. of replicates = 5

Table 3: Modulus of elasticity (MOE) bending strength on
heat treated Gigantochloa levis.

                                 Basic density
                                 (g/[cm.sup.2])

Temp.           Duration   Green    Air-dried
([degrees]C)     (min)     bamboo    bamboo

Control            --       685        707
140                30       665        679
140                60       677        680
140                90       668        669
180                30       663        686
180                60       668        683
180                90       675        608
220                30       702        681
220                60       671        609
220                90       664        603

                                MOE (MPa)

Temp.           Green       %      Air-dried      %
([degrees]C)    bamboo   changed    bamboo     changed

Control         17159      --        18752       --
140             15864      7.5       17573       6.3
140             15467      9.9       17254       8.1
140             14905     13.1       17143       8.6
180             14505     15.7       17014       9.2
180             13951     18.7       17020       9.2
180             13114     23.6       17002       9.3
220             11902     30.6       16918       9.8
220             13594     20.8       16703      10.9
220             11622     32.3       13918      25.8

No. of replicates = 5

Table 4: Modulus of rupture (MOR) bending strength on
heat treated Gigantochloa levis.

                                 Basic density
                                 (g/[cm.sup.]2)

                Duration   Green    Air-dried
Temperature      (min)     bamboo    bamboo
([degrees]C)

Control            0        685        707
140                30       665        679
140                60       677        680
140                90       668        669
180                30       663        686
180                60       668        683
180                90       675        608
220                30       702        681
220                60       671        609
220                90       664        603

                               MOR (MPa)

                Green      %      Air-dried     %
Temperature     bamboo   change    bamboo     change
([degrees]C)

Control          180       --        752        --
140              173      3.9        722       4.0
140              170      5.6        693       7.5
140              175      8.3        693       7.8
180              164      8.9        689       8.4
180              163      9.4        682       9.3
180              157      12.8       678       9.8
220              153      15.0       669       11.0
220              151      16.1       631       16.1
220              138      23.3       625       16.9

No. of replicates = 5

Table 5: Compression and shear strengths on heat treated
Gigantochloa levis.

                                          Compression parallels
Temperature                               to grain
([degrees]C)
and duration             Green   % changed   Air-dried   % changed

Control                  53.7       --         62.1         0.0
140[degrees]C, 30 min    53.1       1.1        60.8         2.1
140[degrees]C, 60 min    52.9       1.5        60.6         2.4
140[degrees]C, 90 min    52.7       1.9        58.6         5.6
180[degrees]C, 30 min    52.6       2.0        49.4        20.5
180[degrees]C, 60 min    52.2       2.8        46.7        24.8
180[degrees]C, 90 min    52.1       3.0        45.1        27.4
220[degrees]C, 30 min    52.0       3.2        40.6        34.6
220[degrees]C, 60 min    51.8       3.5        39.9        35.7
220[degrees]C, 90 min    51.4       4.3        39.0        37.2

Temperature                               Shear // to grain
([degrees]C)
and duration             Green   % changed   Air-dried   % changed

Control                   9.2       --          8.8         --
140[degrees]C, 30 min     8.3       9.8         7.8        11.4
140[degrees]C, 60 min     8.2      10.9         7.7        12.5
140[degrees]C, 90 min     8.1      12.0         7.7        12.5
180[degrees]C, 30 min     8.0      13.0         7.1        19.3
180[degrees]C, 60 min     7.9      14.1         7.1        19.3
180[degrees]C, 90 min     7.7      15.2         6.8        22.7
220[degrees]C, 30 min     7.5      18.5         6.7        23.9
220[degrees]C, 60 min     7.2      21.7         6.7        23.9
220[degrees]C, 90 min     7.1      22.8         6.6        25.0

No. of replicates = 5

Table 6: Weight loss (%) of heat treated Gigantochloa
levis after 12 months of ground contact tests.

Temp.             Duration   Initial wt.   Final wt.    Weight
([degrees]C)       (min)        (gm)         (gm)      loss (%)

Rubber wood          --         10.6          6.5        38.7
Control bamboo       --          9.3          5.0        46.2
140                  30          6.7          4.6        31.3
140                  60          6.8          4.9        27.9
140                  90          6.8          5.0        26.5
180                  30          7.4          5.8        21.6
180                  60          7.0          5.9        15.7
180                  90          6.1          5.2        14.8
220                  30          7.5          6.4        14.7
220                  60          6.2          5.3        14.5
220                  90          6.6          5.7        13.6

No. of replicates = 5

Table 7: ANOVA for moisture content, basic density, MOR and
MOE of heat treated Gigantochloa levis at 140[degrees]C,
180[degrees]C and 220[degrees]C for 30, 60 and 90 min.

Source of                      F- value and
variation                      statistical significance

                     Treatment      Bamboo
                     duration      condition

Moisture content      17.6 *        10.4 *
Basic density         60.4 *        0.1 ns
MOR                   29.7 *        112.4 *
MOE                    6.2 *         6.5 *

ns is not significant; * significant at P < 0.05; ** highly
significant at P < 0.01;

Note: Bamboo condition is referred to bamboo at green or
air-dried condition; Treatment duration is referred to
exposure period of 30, 60 or 90 minutes with temperature at
140[degrees]C, 180[degrees]C or 220[degrees]C
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Author:Wahab, Razak; Rasat, Mohd Sukhairi Mat; Mohammad, Mazlan; Samsi, Hashim W.; Mustafa, Mohd Tamizi; Ah
Publication:Advances in Environmental Biology
Article Type:Report
Date:Feb 1, 2016
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