Preparation and Characterization of Micro Crystalline Cellulose Fiber Reinforced Chitosan based Polymer Composites.

 

Jeba Jeevitha R.S¹*, Bella G.R², Dr. S. Avila Thanga Booshan³

¹Department of Chemistry, Nesamony Memorial Christian College Marthandam, TN India.

²Department of Chemistry, Women’s Christian College Nagercoil, TN India.

*Corresponding Author E-mail: jebajeevitha@gmail.com

Plastics are widely used in society due to low cost, light weight and excellent performance which varies from soft rubbers to  fibers stronger and stiffer than steel. On the other hand their non- biodegradability creates serious environmental problems. The utilization of packaging films from bio-based compounds has received so much attention lately due to the fact that they are readily biodegradable. The two most abundant polymers on earth like cellulose and chitosan have attracted increasing attention as a source of renewable energy and functional materials. Rice straw fiber is subjected to different treatment along with chitosan to form composites. The film samples have been characterized by FTIR and SEM, thermal properties by TGA and DTA. Reinforcement of chitosan with prepared microcrystalline cellulose from rice straw enhances the moisture resistance and strength of chitosan film.

 

 

INTRODUCTION:

Plastic materials are indispensable in our lives but they are a threat to our environment. In order to reduce the impact on environment, researchers have turned to bio polymers [1]. Cellulose is the most common organic compound and biopolymer in earth [2]. Cellulose is a crystalline polysaccharide consisting of D- glucose [3]. Cellulose has no taste, odorless, and insoluble in water and in most organic solvents [4]. Cellulose appears to be an ideal support material for many enzyme systems, being both bio sourced and biologically compatible [5]. In recent years there has been an increasing trend towards more efficient utilization of cellulosic agro- industrial residues. Wheat, corn, oats, coir, sisal and other crops are also used to produce fibers and investigating to reinforce in composite area [6]. Rice straw is one of the most abundant low cost ligino-cellulosic materials [7]. It consists of 43.30% cellulose, 26.40% hemicelluloses, 16.29% lignin, 26% ash and 2.18% waxes [8].

 

Various methods are used to remove all the hemicelluloses, lignin, ash and waxes to get fibers [9]. Fibers are widely used in polymeric materials to improve mechanical properties [10]. The composite materials have advantages like light weight, high specific stiffness and strength, easy moldable to complex forms, easy bondable, good dumping, low electrical conductivity, thermal expansion and good fatigue resistance [11].

 

Chitosan is a second abundant polymer in the earth [12]. Chitosan exhibits unique physico chemical properties like biocompatibility [13], biodegradability and film forming ability [14] which have attracted scientific and industrial interest in the fields such as biotechnology, pharmaceuticals, biomedicine, packaging etc [15]. The films are often brittle which limits their applications [16]. In this present study cellulose fiber reinforced chitosan based polymer composites were prepared and characterized.

 

EXPERIMENTAL METHOD:

Materials: Rice straw was collected from field of Kuzhithurai which is located in KK Dist, Tamil Nadu. Chitosan was purchased from India sea foods, Cochin, Kerala. Analytical grade ethanol, H₂O₂, acetic acid, toluene from S.D fine chemical was used.

Preparation of cellulose from Rice-straw (RS)

The rice straw (RS) was dried in the sunlight and pulverized with a blade grinder. The chopped rice straw was sieved through 0.8mm size screen. About 20gm of powdered rice straw was treated with 400ml of 5% HNO₃ and refluxed for 3 hrs. The treated slurry was washed with distilled water to remove the dissolved substances. The fibers obtained were again refluxed with aqueous NaOH for 2 hrs. The black slurry obtained was filtered and washed with distilled water till the solution become neutral.10ml of 30% H₂O₂ was added and maintained at 70 to 80⁰ C for 30 minutes and washed with distilled water. The fiber obtained was dried in oven at 70⁰C for 24 hrs.

 

Preparation of Chitosan Films

About 12g Chitosan was dissolved in 8% acetic acid by constant stirring and the viscous solution formed was filtered through sieve to remove undissolved impurities and the solution was degassed. The prepared chitosan solution was poured in a glass mould and dried at -4⁰C. H₂O₂ was used as curing agent. A transparent, uniform and slightly yellowish film was obtained.

 

Preparation of Chitosan/ Microcrystalline Cellulose composites (CS/MCC)

Chitosan was dissolved in 8% acetic acid and stirred for 20 min to homogenize. Different percentage (1%, 3%, and 5%) of cellulose fibers were added and stirred for 2 hrs. Added 2 to 3 drops of H₂O₂   as curing agent .The prepared composites were dried at -4⁰ C.

 

FTIR Spectroscopy

Infra red spectra were taken in a Shimadzu -FT-IR spectrometer by KBr pellet method.

 

Scanning electron microscopy

The surface morphology of prepared composites was studied using scanning electron microscopy. A narrow primary electron beam of the order of 10Kev in energy is scanned across the surface of the specimen and observed under different magnification.

 

Thermal studies

Thermal studies of the films have been performed at a heating rate of 20⁰c/min in nitrogen using universal V4-3A instrument (model SDTQ 600). Samples were heated from room temperature to 700⁰C.

 

Tensile strength

Tensile strength was measured with an Instron 3365 instrument. Eight samples 1cm×10cm were cut from each film. Tensile strength was calculated by dividing the maximum force by cross sectional area.

 

RESULTS AND DISCUSSION:

FTIR 

FTIR spectrum of chitosan film shows a strong peak at 3510-3350cm^-1 due to O-H group and N-H stretching vibration. A bending vibration of N-H is observed at 1575cm^-1. A peak at 1654cm^-1 is of amide group and the one at 2922cm^-1 is of C-H vibration. The broad peaks at 1028cm^-1 and 1077cm^-1 and the peak at1153.4 and 898.4cm^-1 correspond to saccharide structure of chitosan. Asymmetric stretching of c-o-c is obtained at 1153cm^-1.The other peaks at 2922cm^-1 and 2871cm^-1 can be assigned to C-H stretching and CH₃ symmetric deformation.

 

The FTIR spectrum of cellulose from rice straw shows a strong band around 3423cm^-1 due to stretching of O-H group, a weak band at 2853.48cm^-1 which attributed to the C-H stretching, band at 1636cm^-1due to the absorbed water molecule, a band at 1425cm-1 which attributed to the CH₂ bending and a strong band at 1059cm^-1 due to the stretching of C-O-C of the pyranose skeletal.

 

In the chitosan- 5%cellulose (CS/5MCC) composite a broad peak observed at 3438cm^-1 is due to hydrogen bonded, O-H stretching at 3400cm^-1 and the NH₂ asymmetric stretching, at 3200cm^-1. The shift in the peak confirms the intermolecular hydrogen bonding and the strong polymerization of cellulose-rice straw. A peak at 2854cm^-1 refers to aliphatic C-H stretching.

 

 

(a)

 

 

 

(b)

 

 

(c)

Fig.1. FTIR of (a) Chitosan film (b) Prepared cellulose (c) Reinforced chitosan film (CS/5MCC)

 

 

 

 

The peak at 1639cm^-1 is due to amide (1) band and H₂O in amorphous region. C-H and N-H vibration shows a peak at 1425cm^-1. Moreover, the N-H bending vibrations (1575cm-1) were not observed in the spectra of CS/RSC composite. The band shifted to higher frequency. When two components are mixed, the physical blending verses chemical interactions are affected by changes in the characteristic spectra peaks.

 

Scanning Electron Microscope

The morphology of pure chitosan and reinforced chitosan film (CS/5MCC) are reported. The pure chitosan film reveals that the film is non porous and the texture is without fibers. An agglomeration is seen in chitosan film. The reinforced composite has branch like structure. On adding cellulose fiber with chitosan the porosity also increases. The cellulose fiber become thicker and also the fibers in the inner layers are clearly visible.

 

 

(a)

 

(b)

Fig.2. SEM of (a) CS film (b) CS/5MCCcomposite

 

Thermal studies

TGA thermograms and char yields of chitosan film and cellulose reinforced chitosan composite were shown in figure.3. In the case of pure chitosan two weights losses were observed. The weight loss at 10-150°C is due to the moisture vaporization. The weight loss at 180-380°C is due to the degradation of chitosan molecule.

 

 

(a)

 

 

(b)

Fig.3 TGA curve for (a) Chitosan film (b) CS/5MCC film

 

In TGA curve of reinforced chitosan (CS/5MCC) composite film the weight losses at 70 to 180°C is responsible for loss of moisture contents. The composite film (11.4%) has lower percentage of water content compared to chitosan film (12.6%). The weight loss at 200-400°C is due to dehydration of the saccharide rings and depolymerization. The second degradation temperature of chitosan is 42.3% but the composite shows higher percentage (50.5%). Addition of cellulose to the chitosan improves the thermal stability. The char yield of composites at about10.9%. 

 

Tensile strength

The tensile strength of CS film and CS based composites were tested in dry states and the results were shown in the figure below. The result shows that there is a small increase of tensile strength until 3% cellulose content and there after gets doubled for 5% chitosan composites. On comparing the pure film with composite film the tensile of CS/5MCC (50.5%) was greater than the other films. This result proved that the reinforced chitosan film act as reinforcing fillers of chitosan matrix to improve the tensile strength of chitosan film.

 

Fig.4. Tensile strength of chitosan film and different percentage of micro crystalline cellulose fibers added to chitosan

CONCLUSION:

The main aim of the above study was to prepare and characterize microcrystalline cellulose reinforced chitosan based polymer composites. RS being the low density fiber and treatments on RS improve the property. The cost of obtained composites was expected to be significantly reduced by adding a cheap lingo-cellulosic waste product. The composite with chitosan can be regarded as a successful light weight engineering material. The prepared composites were confirmed by FTIR, SEM, Thermal studies and Tensile. From the studies the stability of composites compared to chitosan alone was high.

 

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Received on 06.06.2015         Modified on 17.06.2015

Accepted on 25.06.2015         © AJRC All right reserved

Asian J. Research Chem. 8(7): July- 2015 ; Page 453-458