Rjeas Research Journal in Engineering and Applied Sciences 1(4) 219-214 Rjeas Emerging Academy Resources (2012) (ISSN: 2276-8467) www.emergingresource.org PRODUCTION OF CASSAVA STARCH-BASED ADHESIVE Akpa Jackson Gunorubon Department of Chemical/Petrochemical Engineering Rivers State University of Science and Technology, Port-Harcourt, Rivers State, Nigeria. ABSTRACT The production of adhesive from cassava root IITA variety TMS 94/0026 was performed. Applications of starch based adhesive are limited due to its unsuitable properties. Improvements in properties of adhesives produced were achieved by investigating the effects of temperature, mass (concentration) of the viscosity enhancer /stabilizer (borax) and gelatinization modifier (acidic, hydrogen chloride acid (HCl) and basic sodium hydroxide (NaOH)) and its concentration on the properties (viscosity, density and ph) of the adhesive produced. The effect of the gelatinization modifier (HCL and NaOH) on the drying time and bond strength of the adhesive was also investigated. Results obtained provide a wide range of conditions for producing starch-based adhesives for diverse applications and required properties. The adhesives produced with sodium hydroxide as its gelatinization modifier had a stronger bond and a maximum drying time of 7.20 minutes compared to a drying time of 4.16 minutes for the adhesive produced with hydrogen chloride acid. Emerging Academy Resources KEYWORDS: Adhesives, Cassava Starch, Functional Properties Improvement. INTRODUCTION Adhesives are substances that are able to make things adhere or stick together without deformation or failure through a process called adhesion (Baumann and Conner, 2003). Adhesives are categorized as either natural or synthetic. Natural adhesives include animal glues, casein glues, natural gums and resins, sodium silicates and vegetable glues. Vegetables glues are starch-based and are made from starches and dextrin (Kennedy, 1989). Starch has several advantages as a raw material in the production of adhesives, including: renewability, biodegradability, abundance, cheapness and stability in price (Agboola, et. al., 1990) and can also be used to produce such diverse products as food, paper, textiles, beverages, confectionery, pharmaceuticals, and building materials (FAO, 1983). Starch is produced from grain or root crops such as sweet potatoes, maize, wheat, rice, yam or cassava. The advantages of cassava for starch production over other grains or root crop includes: high purity level, excellent thickening characteristics, a neutral (bland) taste, desirable textural characteristics, is relatively cheap and it contains a high concentration of starch (dry-matter basis), (Masamba et. al., 2001). Cassava starch has many remarkable characteristics, including high paste viscosity, high paste clarity and high freeze-thaw stability which are advantageous to many industries. Cassava is a renewable, an almost unlimited resource and one of the most abundant substances in nature. It is one of the most important starchy root crops of the tropics used for food and industrial purposes. In Nigeria, it is consumed raw or cooked as garri, starch flour and a variety of other items (Tonukari, 2004). The cassava project of the Nigerian government aimed at increasing the utilization of cassava for industrial purposes and as a foreign exchange earner has stimulated research into the processing and conversion of cassava and its products into industrial products and as raw materials. It is in line with this initiative that this study seeks the utilization of cassava starch, a secondary product in the production of garri from cassava which is usually drained off especially in the rural areas as a raw material for the production of adhesives. The effectiveness of an adhesive is determined by its bonding capability (resistance to load shear), ease of application, reasonable setting time, resistance to moisture, aging, heat and fungal attack, non-staining and gap filling (Finn, 1990). Cassava based adhesives have the unique advantage of having smooth, clear fine texture, non-staining, more viscous, stable and neutral ph. The nonpoisonous nature makes it a desirable choice particularly for domestic and most non-structural utilization (Masamba, et. al., 2003). The major drawback in the use of starch as an adhesive is the stability of the product over time (FAO, 1983). This study will also investigate possible improvement methods of the properties of the adhesives produced by studying the effects of borax and temperature on the viscosity, density and ph of adhesive and the use of two different modifiers (HCL and NaOH) in the 219
production of the adhesive; thus provide a range of conditions for producing starch-based adhesives for diverse applications depending on the required properties and industrial applications. MATERIALS AND METHODS A TMS 94/0026 (specie of cassava) was used for the study. It was obtained from International Institute for tropical Agriculture (IITA) Onne. The experiments were performed at the Unit Operations Laboratory of the Department of Chemical/Petrochemical Engineering, Rivers State University of Science and Technology, Port-Harcourt. Starch Extraction Process Cassava starch was produced primarily by the wet milling of fresh cassava. Extraction of starch from fresh cassava roots was performed following the steps outlined in Figure 1. When cassava roots are harvested or selected for starch extraction, age and root quality are critical factors. Cassava roots need to be processed almost immediately after harvest, as the roots are highly perishable and enzymatic processes accelerate deterioration within 1-2 days. Ten (10) kg cassava were peeled, washed and grated to finer particles. The starch was then extracted from the grated pulp by sieving while the fiber was retained. The fiber retained was washed repeatedly for at least three (3) to four (4) times with distilled water on the screen. The starch extracted was allowed to sediment after which the fiber was decanted off and the starch is rewashed with distilled water to remove the remaining fiber. The starch was then dried in an oven at a temperature of (45 o C) for six (6) hours to reduce the amount of moisture content and finally dried under a brilliant sunshine for four (4) hours. The powdery starch was then stored in an air tight container to prevent contamination and moisture. Figure 1: Flow chart for production of cassava starch Procedure for Production of Adhesives The adhesive was prepared following the procedure presented in Figure 2. Measured quantity of prepared dried starch was put into a beaker; known volume of 0.01 molar concentration of HCL (gelatinization enhancer) was added and stirred continuously while heating in a heating mantle maintained at a specified temperature. Known mass (concentration) of a viscosity enhancer (Borax) was added in piecemeal and stirred continuously until mixture becomes sticky. Product was allowed to cool. Add Gelatinization Enhancer (NaOH/HCL) Dried cassava starch Stir Continuously Heat in a heating mantle at desired temperature Add Viscosity Enhancer (Borax) Stir continuously until mixture becomes sticky Allow product (Adhesive) to cool Figure 2: Flow chart for the preparation of Adhesive Determination of Optimum Process Condition and Process Optimization To determine optimum process conditions, process was conducted at known/constant volumes and concentration of the gelatinization enhancer hydrogen chloride acid (HCL) at varying temperatures and mass (concentration) of the viscosity enhancer (borax). The effect of gelatinization modifier on the quality of adhesive produced was studied using sodium hydroxide (NaOH) instead of hydrogen chloride acid (HCL) as the gelatinization modifier. Procedure for the production of adhesive was repeated at varying concentrations of sodium hydroxide (NaOH) and borax (sodium tetraborate Na 2 B 4 O 7.10H 2 O) and at the optimum temperature for process as determined from in this study. The adhesives produced using hydrogen chloride acid (HCL) and sodium hydroxide (NaOH) as gelatinization modifiers were applied on pieces of paper, allowed to air dry and the drying time measured. The bond strengths of the adhesives were also determined according to ASTM method F-904. 220
Determination of Properties of Adhesive The quality of adhesive produced was ascertained by determining the following properties of all variations of the adhesive produced after cooling to room temperature of 30 o C. The ph value of all samples produced was determined using a digital ph meter, density was determined according to ASTM method D-792 while the viscosity of the adhesives was determined using a Brookfield Dv-1+ viscometer with spindle #1LY at a speed of 60 rev, per min (60 rpm). DISCUSSION OF RESULTS The results of the quality of adhesive and the effects of temperature, concentration of the viscosity enhancer/ stabilizer (Borax) and gelatinization modifier (Hydrochloric acid or Sodium hydroxide) on the quality of adhesive produced (the effect on the properties such as viscosity, density and ph) are presented and discussed as follows: Effects of Temperature on Properties of Adhesive The effects of temperature on the viscosity, density and ph of adhesive at varying concentrations of the viscosity enhancer (borax) are shown in Figures 3, 4 and 5 respectively. The viscosity of a liquid, gas or fluid is its resistance to flow; as the temperature of the liquid, gas or fluid increases, it become lighter and flows easier; that is its resistance to flow is reduced, hence the viscosities are expected to decrease with temperature. This trend the experiment predicted as shown in Fig. 3 where the viscosity of the adhesive reduces as temperature at which the adhesive is produced increases at all borax concentrations investigated. Similar results were obtained in the works of Bascom and Cottington, 1976) The density of the adhesive is its mass per unit volume. Increasing the temperature at which the adhesive is produced causes the adhesive to swell (Yamamoto et. al., 2006), resulting in an increase in the volume of the adhesive, it also causes a reduction in the water content, resulting in a reduction in mass (Bhambure and Mallick, 2012). Hence the influence of temperature on the density of the adhesive is a balance between these two dynamics. The results in Figure 4 show these dynamics resulting in very minimal increase in density with temperatures depending on which has the greater influence. The temperature at which the adhesive is produced has a marginal effect on the ph of the adhesive produced. At high concentrations, 0.4g and 0.5g borax, the ph of the adhesive produced is virtually constant with increase in temperature. At lower concentrations, 0.2 and 0.3, there is a gradual reduction in the ph with increase in temperature. This trend is show in Figure 5. Effects of Borax on Properties of Adhesive The effect of concentration of the borax (viscosity enhancer) on the viscosity, density and ph of adhesive at varying temperatures of the is shown in Figure 6, 7 and 8 respectively. 221
its resistance to flow (viscosity). Similar trends of increase in viscosity with increased mass of borax were reported in the works of Kurt and Mengelogla, (2008). Borax has been reported to increase the water holding of adhesives and give the adhesive higher molecular weight (Jin et. al., 2010). Therefore an increase in the amount of borax will increase the density of the adhesive produced. Results in Figure 7 show very minimal increase in density with increase in the quantity of borax used. Similar trends were observed in adhesives used by Keskin et. al., (2009). The ph is the negative logarithm to base 10 of the concentration of a solution. Therefore an increase in the mass (concentration) of the solution causes an increase in the ph of the solution. This trend is shown in Figure 8 where the ph of the adhesive produced increases with increase in the mass (concentration) of the borax added to the adhesive at all temperature investigated. Effect of Gelatinization Modifier The gelatinization modifier used in the production of adhesive can either be an acidic or basic type. The effect of a basic gelatinization modifier (NaOH) was investigated. In the investigations with the acidic (HCL) modifier, the adhesive produced at 80 o C was found to have the properties that compare favorably with the commercial adhesives. Hence this temperature was used in the production of adhesives at different concentrations of the modifier; hence its effect on the properties of the adhesive was investigated. The effect the viscosity enhancer (NaOH) on the viscosity, density and ph of the adhesives produced at 80 o C and various concentrations of borax are shown in Figure 9, 10 and 11 respectively. Borax is used as a thickener and gives the required viscosity and structure to adhesives (Atar and Peter, 2010). Results from Figure 6 shows that as the mass of borax in the adhesive was increased, the adhesive became thicker, flowed slower, hence an increase in 222
in density. However as the amount of borax, the thickening agent is increased, the adhesive becomes thicker with higher molecular weight; this effect dominates resulting in an increase in density of the adhesive produced with 0.4g of borax as shown in Figure 9. Sodium hydroxide has been reported to have a neutralizing effect on adhesives (Li et. al., 2004). Therefore the use of a base modifier will make the adhesive produced more basic, hence the ph of the adhesive will increase. These trends are shown in Figure 10. Drying Time and Bond Strength Adhesives produced with HCL had a drying time of 4.04-4.16 minutes while those produced with NaOH had a drying time of 7.1-7.20 minutes. The adhesives produced with NaOH had stronger bond after tagging than adhesives produced with HCL. CONCLUSION An alternative use of cassava starch has been successfully achieved through its use in the production of an adhesive. Possible improvements of the properties of the adhesives produced have been presented by studying the effects of the temperature, mass (concentration) of borax and the gelatinization modifier (HCL or NaOH) used in the production process on the viscosity, density and ph of adhesive. The effect of the gelatinization modifier (HCL and NaOH) on the drying time and bond strength of the adhesive was also investigated. These results provide a wide range of conditions for producing starch-based adhesives for diverse applications depending on the required properties and industrial applications. The amounts of aqueous sodium hydroxide added in producing an adhesive has been reported by Paridah and Masgrave, (2006) to greatly influence the viscosity of the resulting adhesive. Addition of sodium hydroxide also makes the adhesive thinner (Kurt and Mengelogla, 2008). The overall effect is that as the concentration of the modifier (sodium hydroxide NaOH) is increased the adhesive produced become watery, is less jelly-like, lighter, will flow faster and its resistance to flow will decrease; hence the viscosity of the adhesive increases with increase in the concentration of the modifier (NaOH) as shown in Figure 8. Similar trends were reported in the works of Keskin et. al., (2010). The use of borax with small amounts of sodium hydroxide has been reported by Toker et. al., (2009) to change the polymer in an adhesive to a more highly branched chain having higher molecular weight and higher water holdout capability. For the adhesive produced with 0.2g borax, the density decreases with increase in the concentration of the modifier while, for that produced with 0.4g borax the density increased with increase in the concentration of the modifier. Increasing the concentration of the modifier makes the adhesive lighter, hence decrease REFERENCES Agboola, S. O., Akinbgala and Oguntimein, G. B., (1990), Processing of cassava starch for adhesive production, Starch/Starke 42, 12-15. Atar, M. and Peker, H. (2010), Effects of impregnation with boron compound on the surface adhesion strength of varnishes used for wood, African Journal of Environmental Science and Technology vol.4(9), 603-609 Baumann, M. G. D., Conner, A. H. (2003), Ch. 22, Carbohydrate Polymers as Adhesives, Handbook of Adhesive Technology, 2nd ed., A. Pizzi and K.L. Mittal, Marcel Dekker, New York. Bascom, W. D. and Cottington, R. L., (1976), Effect of Temperature on the Adhesive fracture Behaviour of an Elastomer-Epoxy Resin, Journal of Adhesion (7), 4, 333-346 Bhambure, S. and Mallick, P., (2012), Effects of Temperature Variation on stresses in Adhesive joints between magnesium and steel, SAE world congress & Exhibition April 2012 Detroit MI, USA 223
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