Australian Journal of Basic and Applied Sciences
ISSN:1991-8178
Journal home page: www.ajbasweb.com
Corresponding Author: Nor Azillah Fatimah Othman, Malaysian Nuclear Agency, Radiation Processing Technology, Bangi, 43000,Kajang, Selangor, Malaysia.
Evaluation of process parameters for graft copolymerization of glycidyl methacrylate to
kenaf fiber using design of experiment method.
1,2Nor Azillah Fatimah Othman, 2Tuan Amran Tuan Abdullah, 1Nor Azwin Shukri, 1Sarala Selambakkanuand 1Siti Fatahiyah Mohamad
1Malaysian Nuclear Agency, Radiation Processing Technology, Bangi, 43000,Kajang, Selangor, Malaysia.
2Universiti Teknologi Malayia, Institute of Hydrogen Economy, Faculty of Chemical Engineering, 81310, UTM Johor Bahru, Johor, Malaysia.
A R T I C L E I N F O A B S T R A C T
Article history:
Received 15 September 2014 Accepted 5 October 2014 Available online 25 October 2014
Keywords:
Radiation induced grafting Kenaf bast fiber
Glycidyl methacrylate
Evaluation of process parameters
Background: In this study, an evaluation of experimental parameter was carried out using factorial design of experiment (DOE) method for graft co-polymerization of glycidyl methacrylate (GMA) onto kenaf bast fiber (Hibiscus Cannabis L.) under post-irradiation technique via electron beam. The kenaf fiber was treated with sodium chlorite (NaClO2) before grafting. The effect of NaClO2 concentration, GMA
concentration, Tween-20 (Tw-20, surfactant) concentration, irradiation dose, reaction time and reaction temperature were investigated by 26 fractional factorial DOE and
analyzed using Minitab 16. Objective: The effect of 6 reaction parameters in the process of grafting GMA to kenaf fiber could be screened using 2-levels fractional factorial design of experiment method. By using this method, most of the possible variations of the reaction conditions and their interactions could be included in a practical number of experiments. Results: Out of 6 parameters, it was found that irradiation dose, GMA concentration, NaClO2 concentration and temperature have
influences on the percentage of grafting. The grafted fiber was confirmed using Fourier Transformed Infra-Red Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). Conclusion: These findings can be used to optimize the process parameters of grafting kenaf-GMA copolymers and an essential knowledge for better understanding of the interaction between each process parameters.
© 2014 AENSI Publisher All rights reserved. ToCite ThisArticle: Nor Azillah Fatimah Othman, Tuan Amran Tuan Abdullah, Nor Azwin Shukri, Sarala Selambakkanu and 1Siti Fatahiyah Mohamad., Evaluation of process parameters for graft copolymerization of glycidyl methacrylate to kenaf fiber using design of experiment method. Aust. J. Basic & Appl. Sci., 8(15): 107-111, 2014
INTRODUCTION
Cellulose is one of the most abundant natural resources and easily available in low price. However, due to its nature, cellulose-based materials requires modification either by carboxymethylization (Yan, Zhang et al.,
2011), grafting (O’Connell, Birkinshaw et al., 2008) and crosslinking (Hong, Liu et al., 2009) to improve its properties. Fast formation of free radical without any toxic chemical intermediates, like initiator or catalyst offered by radiation-induced grafting make it favorable as an environmental-friendly modification method of polymeric materials with high purity. Furthermore, polymeric material is prepared at low temperature, therefore destruction of the polymer caused by heat can be avoid. Radiation induced grafting can be done simply based on the irradiation of base polymer either in the presence of monomer (post-irradiation grafting) or without monomer (pre-irradiation grafting) to create active sites(Işıkel Şanlı and Alkan Gürsel, 2011). All of these techniques can produce grafted copolymers with improved properties. Therefore, it is not possible to conclude which of them is better. Through our work, we have proven that grafting via post-irradiation technique can achieved reasonably good results with the experimental conditions used.
probable parameters combinations. The results were analyzed using MINITAB 16 statistical software to evaluate the effects as well as the statistical parameters and plots.
This study focuses mainly on the evaluation of process parameters for graft copolymerization of GMA onto kenaf fiber treated with NaClO2 using design of experiment method. The graft copolymerization were done using post-irradiation technique and the parameters selected for the study were NaClO2 concentration (for treatment of kenaf fiber), GMA concentration (monomer), Tween-20 concentration (surfactant), irradiation dose, reaction time and reaction temperature. The 26 fractional factorial design of experiment method was applied to study most of the possible variation of reaction conditions and also to examine their interactions in a practical number of experiments.
Methodology:
Water-retted kenaf bast fiber was supplied by Lembaga Kenaf dan Tembakau Negara (LKTN), Malaysia. Reagent grade chemicals such as nitric acid (for pH adjustment) and NaClO2 were obtained from Sigma Aldrich (Malaysia) Sdn. Bhd. The monomer, glycidyl methacrylate and surfactant, polyoxyethylene sorbitan monolaurate or Tween-20 was supplied by Sigma Aldrich and used as received.
2.2.1 Treatment of kenaf bast fiber:
Sodium chlorite (NaClO2) solution at predetermined concentration was prepared by dissolving sodium chlorite in distilled water and adjusted to pH4 by adding nitric acid. NaClO2 solution was placed on hot plate stirrer and heated to 70°C. Kenaf bast fiber was added to the solution and heated for 6 hours. Upon completion the kenaf was removed from the solution and washed repeatedly with distilled water and dry in oven at 60°C until constant weight.
2.2.2 Radiation graft copolymerization:
About 0.2g of the dried fiber was weight accurately, purged with nitrogen and sealed in plastic zipper bag. About 20mL GMA/Tw-20/Water solution was injected to the samples. The samples were placed on dry ice and irradiated with electron beam at voltage of 2 MeV and current 10 mA at predetermined doses. The irradiated fiber was left in temperature-controlled water bath for reaction at predetermined period of time. The grafted kenaf was removed from the emulsion and washed repeatedly with methanol to remove excess monomer and homopolymer. The weight of GMA grafted kenaf was measured after drying overnight in an oven at 40°C.
Percentage of grafting (Pg) was determined gravimetrically and calculated according to the following formula:
Pg (%) = ((W1 – W0)/W0) x 100 (1)
Where, W0 is initial weight of kenaf and W1 is weight of kenaf after grafting.
2.2.3Design of experiment:
In order to complete study of all parameters and their interactions without increasing the number of experimental runs beyond practical limitations, 2-levels ½ fractional factorial design of experiment approach is applied. The condition for each parameter is listed in Table 1. 26 fractional factorial design of experiment method was applied and 66 run of experiments were conducted with duplicates. The interactions between independent parameters were determined using the statistical software where the main effects were identified based on the P value with >95% confidence level.
Table 1: Levels for each factors
Parameter Notation Units High Low
1. GMA conc. A %(wt/wt) 5 3
2. Tween-20 conc. B %(wt/wt) 1 0.5
3. Irradiation dose C kGy 50 10
4. Temperature D °C 60 40
5. Reaction time E min 180 60
6. NaClO2 conc. F %(wt/wt) 1.0 0.1
The IR spectra of grafted fiber were obtained using Nicolet IS10 ATR-FTIR spectrometer (Thermo Scientific) in transmittance mode at frequency in the range of 4000-400 cm-1. The grafted film morphology was analyzed as a function of degree of grafting using SEM (FEI Quanta 400).
Fig. 2: Normal plot of the standardized effects AE B AF ABD AB E ABCE AD BF ACD D F BD AC A C 18 16 14 12 10 8 6 4 2 0 Te rm Standardized Effect 2.01
A GMA C onc. [% ] B Tw -20 C onc. [% ] C Irradiation Dose [kGy ] D Temperature [C ] E Time [min] F NaC lO 2 C onc.[% ] F actor Name
Pareto Chart of the Standardized Effects
(response is Pg[%], Alpha = 0.05)
Fig. 1: Pareto chart of the standardized effects
Radiation Dose (kGy)
0 10 20 30 40 50 60
P g (% ) 0 20 40 60 80 100 0.1% 0.3% 0.5% 0.7% 1.0%
GMA conc. (%)
0 1 2 3 4 5 6
P g (% ) 0 20 40 60 80 100 10 kGy 20 kGy 30 kGy 40 kGy 50 kGy
Fig. 4: Graph of irradiation dose and GMA
concentration vs percentage of grafting
GM A C o n c . [% ]
Ir ra di at io n D o se [ kG y] 5.0 4.5 4.0 3.5 3.0 50 40 30 20 10
Tw-20 Conc. [%] 0.5 Temperature [C] 40 Time [min] 60 NaClO2 Conc.[%]0.1 Hold Values > ・ ・ ・ ・ < 0 0 100 100 200 200 300 300 400 400 Pg[%]
Co n to u r Plo t of Pg[% ] vs Irradiatio n Do se [kGy], GMA Con c . [% ]
Fig. 3: Contour plot of percentage of grafting vs
irradiation dose and GMA concentration
A B
Fig. 5: SEM of (A) Untreated fiber and (B) Treated and grafted fiber
Fig. 6: FTIR Spectra of (A) Untreated fiber and (B) Treated and grafted fiber
Discussion:
Figure 1 and Figure 2 shows that out of 6 parameters, only 4 parameters give significant effect to the percentage of grafting. Irradiation dose, GMA concentration, NaClO2 concentration and temperature were found to be the most significant parameters and showed the largest effect on the result of the grafting reaction. The highest percentage of grafting was 192.28% which is relatively high compared to other research on grafting using post-irradiation technique. The best value to achieve this grafting yield was 5% monomer/1% surfactant
15 10 5 0 -5 99 95 90 80 70 60 50 40 30 20 10 5 1 Standardized Effect P e rc e n t
A GMA C onc. [% ] B Tw -20 C onc. [% ] C Irradiation Dose [kGy ] D Temperature [C ] E Time [min] F NaC lO 2 C onc.[% ] F actor Name
Not Significant Significant Effect Type ACD BF BD AD AC F D C A
Normal Plot of the Standardized Effects
(response is Pg[%], Alpha = 0.05)
A
concentration with 50kGy irradiation dose and 60°C temperature for 3 hours. Meanwhile the lowest percentage of grafting was 5.5% with the parameters condition of 3% monomer/1% surfactant concentration, 10kGy irradiation dose and 40°C temperature for 3 hours. The condition for sodium chlorite treatment is 1.0% NaClO2 concentration respectively. This treatment is important to remove phenolic compound especially lignin for the enhancement of percentage of grafting (Mohamed, Tamada et al.,2013). This process also changes the properties of kenaf from hydrophobic to hydrophilic which helps the monomer to penetrate easily for grafting reaction.
The model equation related to the level of parameters and percentage of grafting obtained from the experiment is shown in the equation below by substituting the regression coefficients. Please take note that the other effects that are not significant are not included in the model equation. The interactions between parameters give clear idea of the process. For example, it can predicted that although concentration of Tween-20 itself does not contributes any main effects towards the process, but the interaction between Tween-20 concentration and temperature is contributing significant effect to the percentage of grafting.
𝑷𝒈 % = 45.975 + 13.318 𝐶 + 38.113 𝐴 + 7391 𝐹 + 6.587𝐷 + 12.719 𝐴 ∗ 𝐶 + 7.920 𝐵 ∗ 𝐷 +
4.962 𝐵 ∗ 𝐹 + 4.862 𝐴 ∗ 𝐷 + 4.982[𝐴 ∗ 𝐶 ∗ 𝐷] (2)
Contour plot of the two most significant parameters that contribute to the results shown in Figure 3 suggests that the results are not optimized yet and need further improvement for optimization. A large number of work on radiation-induced graft copolymerization (Chauhan, Guleria et al.,2005, Kang, Jeun et al.,2007, Seko, Ninh et al.,2010, Wojnárovits, Földváry et al.,2010, Nasef and Güven,2012, Madrid, Nuesca et al.,2013, Mohamed, Tamada et al.,2013, Sharif, Mohamad et al.,2013) reported that percentage of grafting increase with the increasing of irradiation dose as shown in Figure 4. This is mainly due to the formation of more free radicals at higher irradiation doses which increasing the accessibility of monomer towards the active sites (Nasef and Güven,2012). Madrid, Nuesca et al. (2013) also evidenced the same phenomena where the percentage of grafting of GMA onto water hyacinth increase with the increase of irradiation dose(Madrid, Nuesca et al.,2013). The scanning electron microscopy images of grafted material in Fig. 5(B) show a smooth surface and the evidence of thick coating of GMA on the fiber. Raw kenaf in Fig. 5(A) is characterized with a rough, dirty surface and glued together because it is coated with non-cellulose compound. Fig. 6 shows the FTIR spectra of raw kenaf fiber, NaClO2 treated kenaf and GMA grafted kenaf. As shown in the spectrum of GMA grafted kenaf fiber, the absorption bands at 1724 cm–1 and 1300–1100cm–1 region correspond to COO and C–O–C stretching of acrylate group. This is confirms that the agreement between this work and our previous work (Sharif, Mohamad et al.,2013) is satisfactory.
Conclusion:
The effect of 6 process parameters in the grafting of GMA onto kenaf bast fiber could be evaluated by using design of experiment 2-levels fractional factorial method. Irradiation dose, GMA concentration, NaClO2 concentration and temperature were found the most significant parameters and within the range of these variations, the highest percentage of grafting achieved is 192%. Further investigations need to be conducted for the optimization of the process parameter using response surface method (RSM).
ACKNOWLEGEMENT
The authors wish to thank to Malaysian Ministry of Science and Technology (MOSTI) for granting Science Fund under the vote number of 03-03-01-SF0214.
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