CHARACTERIZATION OF BIOCOMPOSITES FROM POLYLACTIC ACID AND CELLULOSE OF OIL PALM EMPTY FRUIT BUNCH

Biocomposites are polymers reinforced with natural fibers, such as cellulose. This research aims to synthesize cellulose from Oil Palm Empty Fruit Bunch (OPEFB) and biocomposites from PLA and cellulose. In this study, cellulose was obtained through alkalization, hydrolysis, and bleaching of OPEFB. Biocomposites production was carried out by mixing PLA and cellulose using the extrusion method. In the extrusion method, PLA and cellulose of OPEFB were mixed using an extruder above the melting point of PLA of 170°C. The output product of an extruder was then pressed using a compression moulding machine to form biocomposites. The tensile strength of biocomposites had a smaller value than pure PLA, whereas the modulus young of biocomposites with 5% by weight of cellulose had a higher value than pure PLA. The decrease in the mechanical properties of biocomposites was caused by poor adhesion between PLA and cellulose. The water absorption of biocomposites was greater than pure PLA, which was influenced by cellulose's characteristics as hydrophilic and PLA is hydrophobic. Also, the higher water absorption in biocomposites accelerated the weight loss of biodegradability.


INTRODUCTION
In recent years, composites have rapid development due to the demand for applications in the construction, automotive, aerospace, and packaging industry [1][2][3].
Composite consists of polymers as matrix and fillers. The characteristic of polymers is lightweight material [1] compared to glass or metal. Also, polymers are easily shaped according to the desired design and size.
However, polymers and fillers that cannot degrade naturally by microbes in the soil will cause pollution and damage to the environment. Therefore, biocomposites are developed because its advantages are environmentally friendly and biodegradable.
Polylactic acid (PLA) is one of the biopolymers that are widely used and developed. PLA has advantages of excellent biodegradability, processability, and biocompatibility [4]. PLA can be used as a raw material to produce plastic bags, laminated films, overwrap films, disposable glasses and plates, drug delivery systems, suture, and scaffold [5].
The addition of filler into the PLA matrix is interesting because it can increase the biodegradation rate [6]. One type of filler commonly used is cellulose. Cellulose can be obtained from oil palm empty fruit bunch (OPEFB). The cellulose of OPEFB is about 42.7-65% by weight. Cellulose from OPEFB as a filler is also a solution to increase the value of waste produced by palm oil industries. The characteristics of OPEFB are cheap, low density, high strength, and biodegradable [7].
Several studies on the addition of cellulose to PLA polymers have been done.  The cellulose of OPEFB was filtered, washed until pH neutral, and dried. OPEFB was ground and sieved again using a 325 mesh sieve.

Production of Biocomposites
The production process of PLAcellulose biocomposites using the extrusion method. PLA and cellulose were mixed using a magnetic stirrer. Afterwards, the mixture of PLA and cellulose was extruded. The composition variation of cellulose of OPEFB were 0%, 5%, and 10% by weight. The screw temperature of the extruder was 170°C. The output of the extruder was pelleted. The pellets were then pressed using compression moulding with the pressure of 10 MPa and temperature of 170˚C [11].

Fourier Transform Infrared Spectroscopy
The production of cellulose of OPEFB through a series of processes via chemical and physical route, including alkalization using NaOH, hydrolysis using water at high temperature, and bleaching using NaOCl.
The aim of a series of processes is to breakdown lignin bonds. The FTIR results in

Water Absorption
The water absorption of biocomposites increases with the addition of cellulose. The results of the water absorption analysis of biocomposites are shown in Figure 3.  The water absorption is related to the diffusion water rate into the biocomposites the high water absorption in biocomposites due to cellulose's hydrophilic characteristic.
Cellulose has many hydroxyl groups which interact with water molecules. Besides, cellulose on the matrix's surface will absorb more water than cellulose in the matrix. Water molecules can saturate on the biocomposites surface and penetrate through a hole, resulting in high water absorption quickly.

Biodegradability
The amount of cellulose influences the weight loss of biodegradability in biocomposite. Surface erosion indicates the level of biodegradation that occurs in biocomposites [17].