Key Words: Disperse dye, Poly Lactic Acid, Fabric, elongation, tensile strength
Introduction and statement of the problem
The polymerization of lactic acid yields polylactic acid. As such, the raw material used in the manufacture of polylactic acid is lactic acid. Lactic acid is a naturally occurring substance that is produced by living things during metabolism. The use of polylactic acid in the production of fibers for various applications in the textile industry can be traced back to a very useful discovery a few decades ago. The production of biodegradable surgical sutures using polylactic acid set the path clear for more applications of polylactic acid (Ren 98). The good thermoplastic and mechanical properties of polylactic acid fibers enabled its use in a wide array of applications.
Although the initial use of polylactic acid fibers was in non-woven materials, the desire for environmental conservation inspired the blend of cotton and polylactic acid fibers currently used in making various clothes. Fabric material to be worn requires to be very alluring and aesthetically pleasing, otherwise they may not fetch the intended value in the market. To this end, it is important to understand the performance of the fabric in different conditions. More precisely, it is important to understand the interaction of the fabric and different dyes (Deopura 123). There is no sufficient literature and scientific data on the optimum conditions required for the optimum of dyes on fabrics made of polylactic acid in order to attain the vibrant colors that are commercially required.
Even more importantly, the effect of the dyes on the rheological and mechanical polylactic acid. The use of this polymer in the manufacture of textiles depends on knowledge on the effect dyeing has on them (Yu 53). Dyeing is done under different conditions. As such, the effect of dyeing on the mechanical and rheological properties of polylactic acid can only be done in the broader context of the conditions the polymer is subjected to during dyeing. Different conditions of the dyeing process have different effects on the structural, mechanical and rheological properties of polylactic acid. This proposal will explore the effect of dyes on the rheological and mechanical polylactic acid by looking at the dyeing conditions to which the polymer is subjected.
Hypothesis
This proposal will test the following null hypothesis: -
Dyeing has no significant effect on the mechanical and rheological properties of polylactic acid.
Material and methods
The experimental part of the proposal will use fabric from a double knit pullover with a density of 159 grams per every cubic centimeter of the fabric. Before the experiment, the fabric will be soaked in AATCC for scouring. This is the standard reference detergent used for scouring fabrics before experiments. These materials will be purchased from NatureWorks LLC. The elongation and the tensile strength of the fabrics will be measures using an instron tensile tester. This important for the calculation of losses in elongation and tensile strength after the experiment. The experiment will be performed devoid additional auxiliary chemicals. This is with an exception of a buffer solution meant to adjust the pH in order to eliminate external interferences when evaluating dyeability. In order to adjust the pH of the dye baths to be used, acetic acid and sodium acetate at a pH of 4 and 5, monopotassium phosphate and sodium hydroxide at a pH of 6 and 8 and disodium hydrogen phosphate and monosodium phosphate at a pH of 7 (Sin, Abdul & Wan 123).
The fabrics to be used in the experiment will be weighed to exactly five grams. The fabrics will be dyed using 3 % PROSperse Disperse Dyes. Six variants of the dye will be used. They will be selected based on their pH sensitivity, chemical constitutions, popularity and energy levels. They include Disperse Yellow 218, Disperse Orange 25, Disperse Violet 33, Disperse Red 325, Disperse Red 60, Disperse Blue 26. The dyeing process will commence at room temperatures; 25oC. These temperatures will then be ramped to 135oC at a rate of two degrees for every minute over a period of ninety minutes. In order to increase the accuracy of the results, the procedure will be carried out simultaneously in two parallel canisters and the average found for the final results (Thomas, Visakh, and Aji 56).
The dye baths will be maintained at 75oC, 95oC, 115oC and 135oC. At the end of the dyeing cycle, the samples will be rinsed in cold water in order to rid them of the excess dye. In order to dry them, a centrifuge will be used at 25oC. After the samples are dry, they will be analyzed for K/S value and shade depth. This will be done at the wavelength where there is maximum absorption of the dye. (Belgacem & Alessandro 87). This will be done using a spectrophotometer. The readings will be carried out in three different areas at the same wavelength and an average found. This will be done from the posterior of the fabric in order to ensure consistency of results. The yarns of the fabric will be tested for elongation and tensile strength using an instron tensile tester.
Anticipated results and findings
The K/S value is expected to increase with every increase in temperature. This is applicable for the six variants of the dye used in the experiment because of increased dye exhaustion experienced at high temperatures. This shows that increased temperatures open up the structure of the fibers hence allowing more surface to be accessible to dye as evidenced by dye exhaustion. It is also expected that poly lactic acid fibers will experience significant losses in their elongation and tensile strength at high dyeing temperatures. The loss of strength in poly lactic acid is due to hydrolysis of the poly lactic acid. There is considerable degradation of poly lactic acid when wet heat is applied of poly lactic acid fibers as compared to when dry heat is used even at higher temperatures.
Expected significance and broader impacts
The knowledge of the effects of dyeing on the mechanical and rheological properties of poly lactic acid, as espoused earlier is important in the textile industry. The findings that wet heat causes the degradation of poly lactic acid fibers is important in the laundering process of the fabrics (Zollinger & Iqbal 63). This finding is also important in the development of better dyeing conditions.The knowledge here will inspire the next generation of fabrics made from poly lactic acid. The end-product characteristics of the samples will help determine the optimum dyeing temperatures in order to preserve the tensile strength and other mechanical properties of poly lactic acid. It is important for manufacturers to produce strong fabrics. The effects of dyeing are determinants of this and as such, this study will help the textile industry.
Works cited
Belgacem, Mohamed N, and Alessandro Gandini. Monomers, Polymers and Composites from Renewable Resources. Oxford: Elsevier, 2008. Internet resource.
Deopura, B L. Polyesters and Polyamides. Cambridge, England: Woodhead Publishing in association with the Textile Institute, 2008. Print.
Ren, Jie. Biodegradable Poly (lactic Acid): Synthesis, Modification, Processing and Applications. Beijing: Tsinghua University Press, 2011. Internet resource.
Sin, Lee T, Abdul R. Rahmat, and Wan A. W. A. Rahman. Polylactic Acid: Pla Biopolymer Technology and Applications. Oxford: William Archer, 2012. Internet resource.
Thomas, Sabu, P M. Visakh, and Aji P. Mathew. Advances in Natural Polymers: Composites and Nanocomposites. Dordrecht: Springer, 2011. Internet resource.
Yu, Long. Biodegradable Polymer Blends and Composites from Renewable Resources. Hoboken: John Wiley & Sons, 2009. Internet resource.
Zollinger, Heinrich, and A Iqbal. Color Chemistry. Weinheim: Wiley-VCH, 2001. Print.
