CHAPTER II

Adhesives are known as a substance that is capable of joining surfaces permanently. This is process which involves dissimilar bodies that are being held in intimate contact such that mechanical force or work can be transferred across the interface. In addition to this, every materials should have an adhesive that purposely work effectively. The usual household materials are leather, wood, plastics, rubber, metal, fabric, and glass (Dan, 2021).

Sap is mostly liquid and there are other elements to be added for it to become so thick and sticky. Sap is rich with both minerals and carbohydrates in the form of sugar compounds which are carried throughout the tree (Lacoma, 2017). Tree sap and tree resin are usually mistaken but they are not the same with its consistency. Maple syrup are come from maple trees in the form of sap that drips into a container hung from a tap hammered into the tree. Deciduous trees do not produce resin but they produce sap. Sap is way more watery than the resin which is thick and slightly amber in color. Pine, cedar and Douglas fir are classified as coniferous tress which produce both sap and tree resin (Miller, 2018). Cherries produce delicious and nutritious fruits that are used as an ingredients in all aspects of cooking. Carpenters use the wood trees to build furniture, dishes and even toys. However, cherry tree has bark that is very thin, making it easy to draw sap from the wood. Unlike the case with maple trees, a lot of people have no idea on how to use cherry trees sap. This cherry sap provides information on the health and life of the tree and it has many different uses (Taylor, 2017). Boiling down plant sap, it becomes a sticky tar-like or waxy substance. This substance is often used for waterproofing and gluing things (Dykes, 2019). This is in its strong contrast in making contemporary high-strength glues that involves the complex and expensive routes. With the new glue that taking bio-based particles sourced from plants sap and then completed by quite literally instructing to just add water to the glue has obvious green and cost-effective credentials (O'Brien, 2020). Depending on the availability of cheap sources of our products like these fruit plant sap as glue or adhesive can help for the economic stability of the nation. Products, specifically the sap from star apple extract are expectedly the supply part of country’s economic problem in the future (Mecua, 2016).

Testing the strength of glue, there are few things that are need to do. First is to understand how glue works. It works by the two principles that are adhesion and cohesion. Adhesion which define as the ability of glue to stick to the surface of the material and cohesion is the ability of glue to stick itself. To test the strength of the glue is to have a good adhesion and cohesion. Glue fills with tiny molecular gaps in a material then hardens or set to its material itself (Nicholson, 2017). Humidity is a factor that may affect pressure sensitive adhesion performance. The purpose of this heat and humidity test method is to estimate the resistance of adhesive-bonded joints to thermal and hydrolytic degradation. It is primarily for wood-to-wood joints but it can be also applied to joints of wood to other materials. Effects of chemicals such as fire retardants, preservatives, and extractives in the wood upon joint degradation resistance can be estimated. This method does not account for the effects of stress, the other principal degrading factor, nor does it account for cyclic or variable temperature or moisture levels (Chang, 2019).

The resin that produced by pine tree and birch tree has also been tested for their shear strength or ability to fulfill a shearing force at varying temperature. Adding charcoal to pure pine and birch resin was found to increase the adhesive abilities of the resin until a certain threshold of force was applied. Boiling method of resin also produced this effect of adhesive consistency (Poulis, 2017). Based on the study about comparing the adhesive strength of pine resin to commercial glues, the potential of pine resin to be used as an eco-friendly and non-toxic alternatives to commercial glues is suitable for casual usages. For consumers that are seeking to use a natural and eco-friendly adhesive, pine resin may be the solution (Yau, 2019).

The aim of this study, the preparation and optimization of natural glues based on Laricio pine resin, was to prepare and optimize glues especially consisting of natural components. The primary component was the Laricio pine resin which are able to add different additives varying their nature and quantity. The additives used and mentioned in the study are charcoal for the melting process, activated carbon which is used to purify liquids and gases and carbon nanotubes that is used in very low percentages in the presence of an adequate solvent, such as ethyl alcohol, make it possible to obtain a glue that is easy to apply, with an excellent adhesive capacity. The evaluation of the adhesive capacity of the glues was carried out by cutting, tensile and flexural tests on prepared wooden specimens. The optimization of the systems continued to identify and select suitable solvents, in order to improve dispersion and solubility of the phases and to obtain glues in the fluid phase at room temperature. The best results were obtained with ethyl alcohol that represents a solvent with a limited environmental impact (De Luca, 2018). The study indicates that pine resin has a greater adhesive strength than the 50:50 pitch/beeswax mixture and the glue gun, but lower than that of the fish glue and Elmer’s glue. The research result is to have a 50:50 mixture of the plant sap combination as an eco-adhesive (Yau, 2019). Appropriate mixing equipment is important in creating a strong and durable adhesive. Glues are emulsions that made by mixing polymers into a solvent, such as water. The appropriate level of agitation is important to ensure the emulsion mixes adequately. Otherwise, the glue may settle once it is bottled, rendering it ineffective. It may require an even more high-speed option, like a high-pressure homogenizer or colloid mill. This combination utilizes the shearing, agitation, and high pressure to emulsify adhesives together (Loeschen, 2019).

There are studies that prove that a jackfruit sap has the ability to become glue for it has a substance which is required to form adhesive. It is called the latex. After eating lanzones, the skin will just be thrown in the garbage and see it everywhere near the streets that make our environment unpleasant. The purpose for conducting this study is to help recycling the lanzones peel by making glue from its sap. Because the sap that is extremely sticky that can be a good characteristic of a glue. Aside from that, it can help to keep the environment clean and it can also help students who used glue for school crafts. Commercial glues nowadays become more expensive and most students cannot afford it (Gomez, Samaco, Lendio, 2019). The center of the jackfruit which is very sticky and it is runny white stuff is something like a liquid latex. Before to start cutting the fruit, make sure to cover the knife and hands with olive oil since it is very sticky. It is better to cover your hands in the juice of the seeds and their sheaths during the removal. This will keep the latex from sticking to our hands and knife (Sentenac, 2018). This plant contains sap which has a component that to the white wood glue called latex. Encourage to use an additive ingredient in making a glue because of its extremely sticky and therefore it also utilized as an effective adhesive. Mango and jackfruit sap can be extracted which submerge the sap of mango in one small cup and mixture of 2 sup of sap of jackfruit within a duration of 1 day which it will dispense in creating glue. (Mary Limpiada, 2019)The significance of the effect of using combined amount of ratio of jackfruit and rubber tree latex as an alternative adhesive. The researcher recommends using 1:2 mixture for commercial adhesive purposes which can stand to be the highest pressure among all the sealants tested and is enough on handling the rigors of regular use (Carpo, 2019).