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Abrasion Resistance of Durable Press Finish Cotton Initial Investigations & Model Compound Synthesis
Investigators:
Gary C. Lickfield ( Clemson University) Charles Q. Yang ( University of Georgia) Michael J. Drews ( Clemson University) J. Richard Aspland ( Clemson University)
Participants:
Wei Chen (graduate student, Clemson University) Ning Feng (graduate student, Clemson University) Amanda Lattam (undergraduate student, Clemson University)
Goal The combination of inadequate abrasion resistance and relatively severe tensile strength loss has been the major disadvantage for durable press finished 100% cotton fabrics. The overall objectives of this work are to: characterize the surface nature of the wear of durable press (DP) finished cotton fabric; investigate the cause and mechanism of loss in abrasion resistance of crosslinked cotton fabrics; further develop relationships between the molecular structure of crosslinking agents and their affect on the mechanical properties of crosslinked textile structures; and develop technology for improving the abrasion resistance of DP finished cotton fabrics by preventing and/or removing the crosslinks on the fabric surface.
Abstract Dihydroxyethyleneurea (DHEU) and dimethyloldihydroxyethyleneurea (DMDHEU), along with their sulfur analogs (DHET & DMDHET) based on thiourea, were synthesized and characterized by FT-IR and C-13 NMR spectroscopy. DP finished fabric produced using DMDHEU, DMDHET, and mixtures thereof were produced. Conditioned wrinkle recovery angles for each set of fabrics were similar implying similar crosslinking behavior for both reactants, as expected. EDX analysis of the DMDHET treated fabrics showed the presence of sulfur in a relatively uniform distribution across the fiber cross section. The first set of mono-methylol reactants, designed to react predominantly at the surface of a cotton fiber, has been prepared and is currently being evaluated.
Introduction Durable press finishing is widely used in the textile industry to impart wrinkle-resistance to cotton fabrics and garments. Significant loss in mechanical strength and abrasion resistance of the durable press finished fabrics have been a major concern for the industry. The increase in dimensional stability and wrinkle resistance with resin finishing of cotton has always been correlated with the lower abrasion resistance and tensile strength (1-4). In previous research, we investigated the strength loss for the cotton fabric treated with multifunctional carboxylic acids and found that the strength loss can be attributed to two factors: acid-catalyzed depolymerization of cellulose molecules and crosslinking of
National Textile Center Annual Report: November 2000 C00-C01
C00-C01 2 cellulose molecules (5). The strength of the fiber depends on how much the crosslinked chains can still be mutually displaced under tension in order to adequately resist the applied load. The rigid crosslinks that are formed with the standard formaldehyde based resins and with polycarboxylic acids, such as BTCA, obviously prevent the redistribution of stresses by preventing movement within the fiber microstructure. The crosslinking of cellulose molecules with these relatively rigid crosslinks causes stiffening of the cellulosic macromolecular network and fiber embrittlement thus reducing the mechanical strength of the treated cotton fabric. These same mechanisms are responsible for the reduced mechanical properties of the fiber surface thus leading to poorer abrasion resistance. Cuff edge abrasion or “frosting” is also a source of much consumer dissatisfaction, especially with continuous dyed cotton fabrics due to inadequate dye penetration into the yarn bundle(6). Fiber surface property modification, such as through the use of softeners, has been shown to play an important role in minimizing abrasion and frosting(6,7). This report is concerned with the initial work in this new project and is a brief summary of the work to date and focuses only on two aspects of the current project and their effect on fabric properties such as wrinkle recovery and abrasion resistance: 1) preventing the crosslinking reaction from occuring on the fiber surface by pre-reacting the reactive hydroxyl groups and 2) selectively removing the crosslinks from the surface of the fibers using enzymatic treatments after the fabric is treated with a finish agent.
Current Progress Initial work in the area investigating the removal of the crosslinks from the fiber surface has been concerned with 1) the identification of enzymatic systems which may possibly degrade the DMDHEU crosslinks with cellulose and 2) synthesis & characterization of model reactants and potential degradation products in order to monitor the degradation reaction. While there is currently no commercially available enzyme system which specifically attacks the “ether” linkage between DMDHEU and cellulose, there are several protease systems which may show some activity towards the urea linkage. The progress thus far has been to synthesize and begin characterization of model compounds. Laboratory procedures have been identified and worked up to produce the following compounds: 4,5-dihydroxyethylene urea (DHEU), the dimethyl ether of DHEU – 4,5dimethoxyethylene urea (DMEU), 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU) and the tetramethyl ether DMDMEU), shown below.
O H N
O N H
HO
OH DHEU
H N
O
O N H
H3CO
OCH3 DMEU
HOCH2
N
HO
N CH2OH OH
H3COCH2
N
H3 CO
DMDHEU
N CH OCH
DMDMEU
The DHEU was produced as the condensation product from the reaction of urea and glyoxal, under slightly acidic conditions, as shown in the following reaction:
National Textile Center Annual Report: November 2000 C00-C01
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urea
glyoxal
4,5-dihydroxyethyleneurea
DMDHEU was synthesized from DHEU according to the following reaction:
DHEU
Formaldehyde
DMDHEU
DMEU and DMDMEU were synthesized by the reactions shown below.
The following reagent grade chemicals were obtained from Aldrich: urea (99%), thiourea (99%), glyoxal (40 wt.%), formaldehyde (37 wt.% aqueous solution), and sodium bicarbonate. HPLC grade methanol and ethanol were obtained from Fisher Scientific. All chemicals were used as received. A 6% w/w sodium bicarbonate solution and a 0.1 N hydrochloric acid solution, prepared using deionized water, were used to adjust the pH of the reaction mixtures. Urea was slowly added to an aqueous solution of glyoxal under nitrogen purge, the pH of the reaction mixture was adjusted to a pH of approximately 5.5, the reaction heated to 50° C and allowed to stir for 24 hours. The reaction was cooled to room temperature, neutralized and rotary evaporated to near dryness yielding crude DHEU. A portion of this DHEU was added to an aqueous formaldehyde solution, the pH adjusted to 8.2-8.5, the reaction mixture was heated to approximately 50° C and allowed to stir for 24 hours. The reaction was allowed to cool to room temperature, neutralized and rotary evaporated to near dryness. Thiourea was used in place of urea is to prepare the sulfur labeled reactants DHET and DMDHET. The dimethyl ether derivative of DHEU, DMEU, and the tetramethyl ether derivative of DMDHEU, DMDMEU, were synthesized by refluxing overnight with a 5-10 ten molar excess of methanol which was acidified using 0.1 N hydrochloric acid to a pH of approximately 2-3. The reaction mixture was cooled and neutralized prior to drying in order to minimize the reverse reaction.
National Textile Center Annual Report: November 2000 C00-C01
C00-C01 4 FT-IR spectra were generated using the Nicolet Magna 550 FT-IR equipped with a Nic Plan IR Microscope. Proton decoupled carbon-13 (75 MHz) NMR spectra were obtained on samples dissolved in D2O. As these compounds form the basis set to be used in developing the HPLC analysis protocol, no attempt was made to purify the compounds prior to NMR and IR analysis. FT-IR spectra obtained for each of the reaction products were consistent with the formation of the target compound and indicated that each consisted of a mixture. FT-NMR spectral results agreed with the FT-IR that the products obtained in each synthesis reaction were mixtures with the compound of interest present in the greatest quantity. The table below lists the chemical shift for each different type of carbon in each product. The results for DHEU, DMDHEU, DMEU, and DMDMEU are in agreement with previously reported NMR data (8,9). The chemical shifts observed for the sulfur labeled compounds, DHET and DMDHET (shown below), are as predicted for these sulfur substituted structures. S H N
S N H
HO
HOCH2 N
OH
N CH2 OH
HO
DHET
OH
DMDHET
Table I. Carbon-13 Che mical Shifts (ppm) of Mode l Compound s Compound Carbony l CHOH NHCH2 OH NHCH2 OCH3
DHEU DHET 165.1 184.4 85.9 88.8 -
DMDHEU 160.9 86 66.6 -
DMDHE T 184.2 88.8 69.6 -
DMEU DMDM EU 165.2 160.9 75.4
NHCH2OCH3 CHOCH3
-
-
-
-
90.9
57.9 90.5
CHOCH 3
-
-
-
-
56.2
56.1
Reversed-phase High Performance Liquid Chromatography characterization of these product mixtures, based on the work of Kottes Andrews et al.(10) and Beck et al. (11), will be utilized to evaluate and monitor the degradation of the DMEU and DMDMEU model compounds with selected enzyme systems. The sulfur substituted DP reactants were synthesized to serve as identifiable "atomic tags" through which to characterize the distribution of crosslinking reagent both within the fabric and, specifically, within the fiber. Thus, the next set of experiments were designed to ascertain the minimum level of sulfur labeled reactant necessary for EDX analysis.
National Textile Center Annual Report: November 2000 C00-C01
C00-C01 5 A bleached mercerized 100% cotton print cloth (Style 400M, Testfabrics, Inc.) was treated using a conventional pad dry cure procedure. The pad bath contained: 6% reactant, 0.1% Triton X100, and 5% catalyst KR solution (Omnova Solutions). After padding to approximately 100% wet pickup, the fabrics were dried at 70°C for 5 minutes and then cured at 160°C for 3 minutes on pin frames. The cured fabrics were washed once with deionized water and dried. Five different pad bath reactant solutions were prepared, by weight, using the normal and sulfur labeled reactants: 100% DMDHEU, 75:25, 50:50, 25 :75 DMDHEU:DMDHET and 100% DMDHET. The wrinkle recovery angles were measured (AATCC Test Method 66-1996) after conditioning for a minimum of 24 hours under standard conditions of 70°F and 65% RH. The WRA results are presented in the following table. Table 1. Average wrinkle recovery angles (w+f) of crosslinked cotton fabric prepared with DMDHEU (U), DMDHUT (T), and mixtures thereof. U/T Ratio 100/0 75/25 50/50 25/75 0/100 Untreated Control WRA (W+F)±(2-5) 288 280 283 278 265 174 The DMDHEU synthesized for this work provided a reasonably high value for the WRA as compared to the untreated control. As the percentage of sulfur labeled reactant was increased in the pad bath reactant mix, the WRA for the fabrics was found to decrease. Even though the values obtained for the 75:25, 50:50 and 25:75 DMDHEU:DMDHET mixtures arenot statistically different, they all are lower than that for 100% DMDHEU. The WRA obtained for fabric prepared using 100% DMDHET is significantly less than both the 100% DMDHEU and the mixtures. Warp and fill yarns were extracted from the treated fabrics, embedded with collodion and microtomed to prepare cross-sections for SEM & EDX analysis. These samples were sputter coated with either carbon or gold. A Hitachi S3500N scanning electron microscope was used to examine the cross section of fiber and obtain EDX spectra. The figure on the following page contains the EDX spectrum for fiber in the warp yarn extracted from the fabric treated with 100% DMDHET. Inset in this figure is a SEM photomicrograph for the same fiber with the EDX line spectra for carbon, nitrogen, oxygen and sulfur superimposed indicating the amount of each element detected across the fiber. The level of sulfur detected using the 100% DMDHET as the crosslinking reagent appears to be more than adequate in identifying the presence of reagent in the fiber. It is unfortunate that carbon coating must be used for both SEM and EDX analysis as the EDX peak for gold overlaps that for sulfur.
National Textile Center Annual Report: November 2000 C00-C01
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The second part of this investigation is to characterize the effect of pre-reacting the reactive hydroxyl groups at the fiber surface on wrinkle and abrasion resistance. This will prevent the formation of crosslinks at the fiber surface during subsequent treatment with durable press finishing reagent. Initial efforts on this portion of the project have focused on identifying monofunctional N-methylol reactants which should not penetrate into the fiber and thus only react with available cellulose hydroxyl groups near the surface. In additon, as the use of softening agents has been shown to increase both the tear strength and abrasion resistance of crosslinked cellulosic textiles, the first group of compounds to be investigated are reactive softening agents based on N-methylol fatty acids amides. Treatment of cotton cellulose with these monofunctional N-methylol reactants should serve to block the surface of cellulosic fiber from reaction with a crosslinking reagent such as DMDHEU, preventing crosslinking at the fiber surface. Also, the depth of penetration of the monofunctional reactant into the fiber will be investigated using a series of compounds with increasing alkyl chain length. The first reactant to be synthesized was N-(hydroxymethyl)dodecanamide. This was produced according to the following reaction: O C11 H 23 CNH 2 Lauramide
O +
HCH
Formaldehyde
O C11 H23 CNHCH 2 OH N-methylollauramide
National Textile Center Annual Report: November 2000 C00-C01
C00-C01 7 Aqueous formaldehyde was slowly added to a solution of lauramide in methanol, in the presence of base, heated to reflux for 2 hours and allowed to cool. The product purified obtained by recrystallization from 95% ethanol(12). The IR spectra of lauramide and the recrystallized N(hydroxymethyl)lauramide are presented in the figure below. The product spectrum shows the expected changes in the 1450–1650 cm-1 and 2900–3500 cm-1 spectral regions due to conversion of a primary amide to a secondary amide with the addition of a hydroxyl group.
Fabrics will be treated with the synthesized N-methylol fatty acid amides and either DMDHEU or DMDHET. The treatments will be carried out both simultaneously and sequentially. Wrinkle recovery and abrasion resistance will be used to assess the changes in fabric physical properties. Cross-sections and EDX will be used to characterize the changes in sulfur distribution at the fiber surface. By reducing the extent of crosslinking on the fabric surface without afecting the crosslinking in the fabric bulk, it is believed that the abrasion resistance of the DP finished fabric can be significantly improved without sacrificing the fabric wrinkle resistance. The removal of crosslinks from the fiber surface, such as may be accomplished using enzymatic degradation of the crosslink, may also lead to the formation of a sheath-core type morphology. In addition to improvingt abraqsion resistance, this would produce a more reactive fiber surface on which additional surface modification chemistry could be performed. References: 1. Grant, J. N., Andrew, F. R., Weiss, L. C., Hassenboehler, C. B., Abrasion and Tensile Properties of Crosslinked Cotton Fabrics, Textile Res. J., 38, 217 (1968). 2. Meyer, U., Mueller, K., and Zollinger, H., Comparison of Textile Mechanical Properties of Cotton in Crosslinking with Dimethylolethyleneurea and Formaldehyde, Textile Res. J., 45, 813 (1975). 3. Murphy, A. L., Margavio, M. F., and Welch, C. M., All-Cotton Durable Press Fabrics of High Strength from Slack-Mercerize, Partially Restretched Yarn, Textile Res. J., 41, 22-31 (1971).
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C00-C01 8 4. Welch, C.M., Improved strength and flex abrasion resistance in durable press finishing with BTCA, Textile Chemist and Colorist, 29, 21 (1997) . 5. Kang, I., Yang, C. Q., Wei, W., and Lickfield, G. C., The Mechanical Strength of the Cotton Fabrics Crosslinked by Polycarboxylic Acids: Part I. Acid Degradation and Crosslinking of Cellulose, Textile Res. J., 68, 856 (1998). 6. Farias, Leonard T., Aspects of Wet Processing Which Affect Color Retention and Crease Edge Abrasion in Wrinkle Resistant Cotton Slacks, Book of Papers, AATCC 1999 International Conference and Exhibition, Oct. 12 – 15, Charlotte, NC, pp. 325 – 327. 7. Turner, John D., Improving the DP Appearance of Cotton Fabrics with Additives and Aminofunctional Silicones, Textile Chemist and Colorist, 20(5), 36 (1988). 8. Beck, Keith R,; Springer, Karen “13C-NMR Analysis of Durable Press Finishing Agents” Textile Chemist & Colorist 20 (12), 29 (1988). 9. Hermanns, K,; Meyer, B.; and Kottes Andrews, B.A. “13C NMR Indentification of Cyclic Ethyleneureas Important in Cellulosic Textile Finishing” Ind. Eng. Chem. Prod. Res. Dev. 25, 469 (1986). 10. Beck, K. R.; Leibowitz, B. J.; Ladisch, Michael R. “Separation of Methylol Derivatives of Imidazolidines, Urea and Carbamates by Liquid Chromatography” Journal of Chromatography 190, 226 (1980). 11. Kottes Andrews, B. A. “Use of Reversed-phase High Performance Liquid Chromatography in Characterizations of Reactants in Durable-Press Finishing of Cotton Fabrics” Journal of Chromatography 288, 101 (1984). 12. 12. Peterson, R. C., Brownell, H. R.“Some Reactions of N-Hydroxymethyldodecanamide, Journal of Organic Chemistry, 25,1960,843-845.
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