Effect of Aluminum Trihydroxide on Thermal Properties Medium Density Fiberboard (Essay Sample)

Effect of Aluminum Trihydroxide on Thermal Properties Medium Density Fiberboard (MDF) Prepared By Kenaf Fiber and Hybrid of Kenaf and EFB Fibers
Name of Student
Undergraduate Course –Chemistry
Name of Professor
Institution Affiliation
Department of
Date Submitted
Discussion and Results
Deferential scanning calorimetric (DSC)
Specimen ATH

Glass Transition Temperature(Tg),ºC

Control Kenaf-MDF

86.17

Kenaf-MDF + 5% ATH

88.78

Kenaf-MDF + 10% ATH

91.41

Kenaf-MDF + 15% ATH

86.53

The thermal properties of medium- density fiberboard (MDF) consists of Kenaf fibre and palm-based pre-polyurethane (Pre-pu) as a green binder. The Kenaf used was in the range of 300 to 500 μm mixed with Aluminium tri hydroxide (ATH) that was varied at 5, 10, and 15 wt% of the total resin mass. It was added into the pre-PU matrix at a ratio of 70:30 of the EFB to pre-PU.
From the Table above the glass transition for control, kenaf-MDF was recorded as 86.17 (Tg), ºC. However, when 5% wt% ATH was added to Kenaf- MDF the glass transition temperature increased marginally to 88.78(Tg), ºC. Further increase of Aluminium tri hydroxide (ATH) to 10 wt% increased the glass transition temperature to 91.41(Tg),ºC. However, when ATH of 15% ATH were added to Kenaf- MDF the glass transition temperature dropped to 86.53(Tg), ºC. Most probably the main reason for this drop is due to nonaparticle (NPs) agglomeration. The agglomerated nonaparticle possibly decreased the polymeric network strength when 15% ATH was added to the sample of Kenaf- MDF +ATH as a result may have led to the decrease of Tg and the tensile characterization of the sample (Chang Dae, 2007, p.12) When FR levels increased to 15% probably the crystallinity of the network may have increased leading to decreased Tg (Kalika et al. 1990).
The results showed that as 5% wt% ATH loading was added to Kenaf-MDF, the glass transition temperature increased. This was due to change in mechanical properties in the Kenaf- MDF which ultimately improved both impact strength and flexural properties of Kenaf- MDF (Bruce, 2007, p.57). At 5 % wt% loading of ATH and 10 % wt% ATH the glass transition temperature increased, however when 15% wt% ATH was added to the material components there was significant drop. When the sample containing kenaf-MDF undergoes physical transformation at different loading levels of ATH, at 5% and 10% heat get absorbed through an endothermic transition, more heat will be required for reaching glass transition temperature (Scheffer & Eslyn, 1961, p.26). The variation in glass transition temperatures can be attributed to different levels of stiffness effects from kenaf fibre which even causes the sample of Kenaf- MDF to experience higher glass transition temperature as compared to the previous test involving EFB-MDF.Kenaf is lignocelluloses materials comprising of various properties of cellulose, lignin, hemicelluloses, inorganic matter and extractives. It is because kenaf has much stronger material components (Scheffer & Eslyn, 1961, p.33). Besides, kenaf has proved to be excellent composites due to its low density, abrasion, and high specific mechanical properties (Mossello, Harun & Risalatih, 2010, p.2119). The kenaf fiber is covered by hemicelluloses, pectin, waxy substances, lignin and the natural oils.
Research findings have established that Kenaf is highly hydrophilic in nature, has superior flexural modulus, and it’s characterized by higher levels of stiffness for the composites (Chen et al., 2011,p. 2952 ). Kenaf MDF has higher glass transition temperature explained by the higher concentration of OH that exists in cellulose that brings the differences in temperature. (Jawaid & Abdul Khalil, 2011,p. 2317). The OH Generally, the addition of Kenaf produces larger properties of enhancement; this is due to the ability of the fiber to offer better wetting, and crystallization behavior and low melt viscosity. When the Al (OH) 3 components react with the cellulose part of the fibre, it changes its fine structure that consequently increases the compatibility of the non-polar polymer. The modulus increases due to kenaf have a significantly higher modulus of about ~70 GPa as a result of high cellulose content. The fibers act as nucleating agent (Horrocks, 2001, p.45).
2- Thermogravemertic Analysis (TGA)
Table (1) TGA results for the control Kenaf-MDF and ATH-filled KF-MDF with 5, 10 and 15 wt% of ATH
Content%

T1

Weight
Loss%

T2

Weight
Loss%

T3

Weight
Loss%

Total Weight
Loss%

0

181

8

263

20

324

48

76

5

190

7

271

19

325

40

66

10

192

5

286

17

348

38

60

15

195

4

289

14

352

37

55

The table above when thermogravimetric analysis (TGA) of Kenaf-MDF treated with fire retardants, ATH (Aluminum tri hydroxide) was studied. The results indicated that ATH changed the reaction of thermal decomposition Kenaf-MDF. The Aluminium tri hydroxide changed the pyrolysis of the particular bonds in the substrate. The results shows that when fire retardants were added to progressively from 5%, 10% and 15% weight, ATH changed the reaction of thermal decomposition of Kenaf-MDF(medium density fireboard). The process was characterized by increase in the amount of char residuals as well as the amount of volatile and combustible vapors during the reaction process. The thermal decomposition of the test results showed significant improvement when Kenaf- MDF was used. At first the degradation took place at slightly lower temperatures at T1 1810 C for control and weight Loss% of 8. Adding 5%, ATH T1 moved to 190 and Loss% of 7. Continued increase in loading of ATH resulted in T1 Weight Loss% decreasing with every additional 5% loading of FR. The weight loss was observed to reduce significantly in the subsequent ATH loading.
The thermal decomposition of the test results followed three different patterns of thermogravimetric regions. The first phase is characterized by small peak as a result of loss of absorbed water in the Kenaf- MDF + ATH. This first weight loss was slightly at lower temperature of about (30 °C - 124 °C) (Xiao et al., 2001, p.225). The second stage is characterized by high loss of weight and within temperature range (125 °C - 405 °C) and consequently leading to formation of volatile combustible compounds. Alternatively it is the stage of cellulose degradation. The final Thermogravemertic degradation process is that of lignin and it takes place within the temperature range of (378 °C - 492 °C). The stage is characterized by formation of char as well as emission of gaseous like carbon dioxide, vapors and carbon monoxide (Ndazi et al., 2007, p.932). It could also be observed that the presence of fire retardant increased the resistance between Kenaf-MDF (particle boards) thermal degradation processes
(Ann-Christine & Sigbritt, 2003, p.1301). The ATH was capable of altering the pyrolysis route as well as increasing the amount of char produced. In the test experiments aluminum tri hydroxide reduced significantly the rate of weight loss and subsequently lowered the temperature at which the delta (highest peak temperature) on the occurrence of volatile formation (Laoutid et al., 2008, p.58)
According to Ndazi at al. (2007, p. 929) at higher temperatures, the long chains in the polymer undergo molecular scission changing both physical and chemical properties in the chains. The result of the degradation process leads to loss of molecular weights, color changes, reduced ductility and embrittlement. When polyurethane is heated at high temperatures, it breaks down due to the process of thermal degradation producing particulates like gases and vapors (Scheffer & Eslyn, 196, p.487). During the thermal degradation of polyurethanes potentially hazardous chemicals, substances may be released in the form of smoke. However, the degradation process was slowed down by the presence of retardants on the polyurethanes.
According to Ndazi (2007, p.926) the thermal degradation of polymers is as a result of chemical reactions in its component parts. The degradation process takes place because of cellulose and hemicellusoe undergoing oxidative reaction with increase in temperature leading to the production of gases. The lignin part is thermally stable therefore contributes more to formation of char as opposed to cellulose and hemicelluloses. Persistent increase in char formation will eventually lead to reduction in formation of flammable gases and provides an insulating effect to the polymer over further thermal...