**5.2.2 Modification with benzoyl chloride**

Wood flour was dipped in solution of 5% of NaOH and benzoyl chloride for 15 minutes. Ethanol solution was used to remove of extra benzoyl chloride for one hour. Finally the fiber was washed with distilled water and dried in oven at 80° C for 24 hours.

### **5.2.3 Modification with acrylic acid**

Wood flour (which was treated with NaOH) was immersed to acrylic acid solution at 50° C for half an hour and was then washed and dried similar to previous steps.

#### **5.2.4 Modification with silane**

The silane used was Triethoxy vinyl silane. 1% of the respective silane was prepared by mixing with an ethanol/water mixture in the ratio 60/40 and was allowed to stand for 1 h. The pH of the solution was maintained between 3.5- 4 with the addition of acetic acid. Wood flour dipped in this solution and was allowed to stand for 1.5 h. The ethanol/water mixture was drained out and the washing and drying steps were repeated as mentioned in previous treatments.

#### **5.3 Processing of the composites**

The modified and unmodified wood flour was dried at 103±2 °C to constant weight before mixing process. PP and the modified and unmodified wood flour were blended in a batch mixer (Haake Buchler) at 190°C and 60 rpm for 8 min. In all cases, the weight ratio of fiber and polymer was 40:60 (Table 2). From the compounds which had been granulated, specimens were injection molded into ASTM standard by an injection molder at a molding temperature of 190°C and injection pressure was 3 Mpa.

#### **5.4 Measurements**

#### **5.4.1 Thermo-mechanical test**

Dynamic mechanical thermal analysis (DMTA) was carried out by using Triton instrument, Model Tritic 2000 made by UK in triple-point bending mode. The dimension of each sample

Thermoplastic Matrix Reinforced with Natural Fibers: A Study on Interfacial Behavior 241

increased due to formation of ester band from the reaction between OH group and bezoyl chloride. The intensity peak for aromatic ring at 1508.2 cm-1 is decreased after surface modification due to removal of lignin. A strong peak at 1730 cm-1 in the FTIR spectrum indicates the presence of acetyl group in the fiber. The intensity peak at 1037.6 cm-1 is increased after silane absorbance, which is an overlap of si-o-si band and c-o stretching of fiber (Lu & Drazel, 2010). In the presence of moisture, hydrolysable alkoxy group leads to the formation of silanols. The silanol then reacts with the hydroxyl group of the fiber, forming stable covalent

Results for the adhesion factor as an evaluation parameter for fillers-polymer interactions

bonds to the cell wall that are chemisorbed onto the fiber surface (Agrawal et al., 2000).

versus temperature is presented in Fig. 17 for different chemical modification.

Fig. 17. Adhesion factor versus temperature for the treated WPCs.

Fig. 16. FTIR spectra of the chemical treated wood flour.

**6.2 Adhesion factor** 

was 5×1×2 cm. The range of testing temperature was from -50 to 150°C and the experiments were performed at 1 Hz frequency and heating rate of 2C/min. During testing DMTA parameters of storage modulus and loss factor were recorded as function of temperature. Then based on equation (4) data analyzed for determining A factor.


\*PP: Polypropylene, W:Wood Flour, U:Unmodified, A:Alkline, B:Benzoylation, C:Acrylication, S:Silane, M:PP-g-Ma

Table 2. Composition of the Studied WPCs.

#### **5.4.2 Mechanical test**

Tensile strength tests of the specimens were carried out according to ASTM D-638 by Instron 6025 model from UK at crosshead speed of 5 mm/min. For each test and type of the composite, five specimens were tested and the average values are reported.

#### **5.4.3 Fourier Transform Infrared Spectroscopy (FTIR)**

The infrared spectra of raw and treated wood flour were recorded on a Bomem, 150-MB series model Spectrophotometer to characterize the chemical change upon treatment of the wood flour with chemical components.

#### **5.4.4 Scanning Electron Microscopy (SEM)**

The morphology of the wood modified-PP composites and interfacial bonding between the filler and the PP matrix was examined using a scanning electron microscope (JXA-840) supplied by JEOL Company Limited, Japan. The samples were viewed perpendicular to the fractured surfaces.
