A Preliminary Study of Carbamoylethylated Ramie - ACS Symposium

Chapter 8

A Preliminary Study of Carbamoylethylated Ramie 1

1,3

1

2

2

C. C. L. Poon , Y. S. Szeto , W. K. Lee , W. L. Chan , and C. W. Yip Downloaded by UNIV OF MICHIGAN ANN ARBOR on March 18, 2013 | http://pubs.acs.org Publication Date: April 17, 1998 | doi: 10.1021/bk-1998-0688.ch008

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Institute of Textiles and Clothing and Department of Applied Biology and Chemical Technology, Hong Kong Polytechnic University, Hong Kong

Ramie fibres were treated with acrylamide in the presence of alkali acting as a catalyst; the add-on ranged from 0.8% to 11.0%. Both the amount of char produced during thermal degradation and the flame resistance in terms of Limiting Oxygen Index were found to have increased from 18 to 24. The properties of the resulting textile were compared with those of the intact ramie fibre, and the relationship between the yield of reaction and the application parameters temperature, catalyst concentration, and duration of the reaction - is described.

The chemical modification of cellulose and methods for modifying cotton have been studied extensively in recent decades. One method for modifying cotton, the Michael addition reaction, uses a vinyl compound to react with the cellulose chain. Frick et al. (7-2) reported that acrylamide readily reacted with cotton under basecatalysed conditions. The carbamoylethyl ether derivative of cellulose fibres prepared by this reaction has good fabric properties and modified dyeing characteristics. This carbamoylethylated cotton can be further modified; the resulting fabric can be dyed with different classes of dyestuffs that have very little or no affinity to cellulose (5). Ramie, which is also cellulosic in nature, is a bast fibre obtained from the stems of the plants Boehmeria nivea or Boehmeria tenacisseama. The fibre of ramie possesses many superior properties, which make it popular in North American and European countries - it is strong, white, lustrous, and durable (4). Nevertheless, there are few academic reports on the chemical modification of ramie as a means of further improving its properties. Based on previous work on cotton, this study aimed to determine some of the factors involved in the application of the Michael addition to the preparation of carbamoylethylated ramie. The physical and thermal properties of the treated and Corresponding author.

©1998 American Chemical Society In Cellulose Derivatives; Heinze, T., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1998.

107

108 the untreated ramie were compared. The thermal behavior of the treated samples was improved, and their textile properties, including tensile strength, were retained. Experimental

Downloaded by UNIV OF MICHIGAN ANN ARBOR on March 18, 2013 | http://pubs.acs.org Publication Date: April 17, 1998 | doi: 10.1021/bk-1998-0688.ch008

Materials. The ramie fabric used was plain weave that had been desized and scoured. The ramie fibre had 96-98% α-cellulose on dry basis with a small amount of lignin. Commercial acrylamide (97%) was used as received. Reagent grade sodium hydroxide was used as catalyst. Carbamoylethylation. Ramie fabrics weighing 5.0 grams were carbamoylethylated by immersing them in a 200 ml aqueous solution containing acrylamide and sodium hydroxide at specified temperatures and durations (Table 1). Thorough water washing was followed by Soxhlet extraction, using water as a solvent to remove the unreacted chemicals. Measurements Weight Gain. The weight gain of the fabric after carbamoylethylation was calculated using the following equation:

Weight Gain (%)=

Wf- Wi Wi

χ 100

where W and Wj are the weights of the treated and the untreated fabrics, respectively. A l l the fabrics were held at 21°C, 65% relative humidity, overnight before measurement. f

Moisture Regain. The moisture regain of sample fibres was evaluated according to the standard procedure, A S T M D2654-89a. Thermogravimetric Analysis. The thermal properties of the reacted fabrics were studied by a Mettler TA2000 thermal analysis system; scanning ranged from 100°C to 600°C at 30K/min in nitrogen atmosphere with a flow rate of 200 cm /min. The onset temperature and the residual amount were evaluated. 3

Limiting Oxygen Index. The flammability of the fabrics was determined as Limiting Oxygen Index according to the procedures stated in A S T M D2863-87. Tensile Properties. Tensile strength of the fabrics was measured by the standard strip test method (ASTM D 5035) using the Instron tensile tester. Results A n d Discussion Influence of Reaction Conditions. Figure 1 shows that increasing the acrylamide concentration under 5% sodium hydroxide was accompanied by an increase in weight

In Cellulose Derivatives; Heinze, T., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1998.


109

Table 1. Experimental Conditions of Carbamoylethylation of Ramie Weight Composition of Solution Reaction Parameters Gain Temp. Duration NaOH Experiment Acrylamide °C Hrs % % Number (%> 4 2.60% 40 5 5 CAA001 4.80% 4 40 CAA002 10 5 7.40% 4 40 5 CAA003 15 6.60% 4 40 CAA004 20 5 4 0.80% 0 5 CAA005 25 4 1.00% 10 5 CAA006 25 4 4.00% 20 CAA007 5 25 4 7.00% 30 CAA008 25 5 8.40% 4 40 CAA009 25 5 5.80% 4 50 5 CAA010 25 4 4.60% 60 5 CAA011 25 2.00% 0.25 40 CAA012 5 25 3.60% 0.5 40 25 5 CAA013 4.60% 0.75 40 CAA014 5 25 1 5.00% 40 CAA015 25 5 5.60% 1.5 40 5 CAA016 25 7.00% 2 40 CAA017 5 25 8.40% 3 40 5 CAA018 25 8.80% 4 40 25 5 CAA019 8.00% 6 40 CAA020 25 5 7.00% 8.33 40 CAA021 25 5 7.20% 10 40 CAA022 5 25 0.60% 4 40 25 0.5 CAA023 3.40% 4 40 CAA024 2.5 25 8.60% 4 40 CAA025 25 5 11.00% 4 40 7.5 CAA026 25


110 gain. At lower concentration, 0-10% of acrylamide, the weight gain increased almost linearly with the increase in concentration. At higher concentrations, as the molar ratio of catalyst to acrylamide became smaller, the increase in weight gain became non-linear and less significant.


^

g Ο %

'I

10.00 9.00 8.00 7.00

-

5.00 4.00 3.00 ; 2.00 1.00 0.00 ^ 0

5

10 15 Cone, of Acrylamide (%)

20

25

Figure 1. Effect of Concentration of Acrylamide on Weight Gain of Fabric. Khalil et al. (5) reported the following reactions when starch was carbamoylethylated in a mixture of cellulose, acrylamide, sodium hydroxide, and water: CELL—OH

NaOH + CH =CH ^ I CONH

CELL—O—CH —CH I CONH

2

2

2

CELL—O—CH —CH 2

2

NaOH + H 0 • CELL—O—CH —CH 2

CONH CH =CH 2

CONH CELL—OH

+

H 0 2

2

2

+ N H (2)

2

3

COONa

2

N a

(1)

2

H

° »

CH =CH 2

+

NH

(3)

3

COONa

2

+

CH =CH COONa 2

NaOH •

CELL—O—CH —CH COONa 2

2

(4)

Khalil et al. (5) also noted that the extent of the reactions depended upon the temperature of the reaction, the concentration of the catalyst, and the duration of the reaction. Our experiments were designed to study the effect of these same three parameters on the carbamoylethylation of ramie in terms of weight gain of fabric after reaction.


Ill Figure 2 shows the effect of reaction temperature on the weight gain of fabrics treated with 25% acrylamide and 5% sodium hydroxide for 4 hours. apparent that an optimum reaction temperature of 40°C gave the maximum weight gain. In the range of 0 to 40°C, the higher the temperature employed, the the reaction rate, and the greater the weight gain.

ramie It is fabric faster

10.00 -[9.00 · ^ 8.00 £ 7.00


I

J

Ο 5.00 \ f> 4.00 3.00 2.00 r 1.00 Î 0.00 4 1

I

* λ

f

0

10

i

1

20 30 40 Reaction Temperature (°C)

1

1

50

60

Figure 2. Effect of Reaction Temperature on Weight Gain of Fabric. When the temperature was higher than 40°C, the weight gain was lower because of hydrolysis of the ether linkages of carbamoylethylated ramie (6) and the loss of beta and gamma cellulose of ramie in the presence of alkali. The activation energy of the reaction was found by plotting the logarithm value of percentage weight gain versus 1/T (Figure 3). 2.50

r •

2.00 s—\

a

8

1-50 J

Î

1.00

•

y = -5.7005X + 20.549

& 0.50 0.00 3J0

3.20

3.30

3.40

3.50

3.60

* 3.70

-0.50 1/Τ(χ10Κ) Figure 3. A Plot of In (% Weight Gain) vs 1/T.


112 The activation energy, E , was calculated by the equation: A


E

A

= -R

δ In (% Weight Gain)

The activation energy of the carbamoylethylation of acrylamide on ramie cellulose was 47.40 kJmol-1. In order to develop efficient reaction conditions, the duration of reaction time was studied (Figure 4). As reaction time increased to 4 hours, weight increased significantly, obviously because of the increase in the reaction and interaction of acrylamide molecules with cellulose hydroxyl groups. 10.00 8.00 .9 6.00 f 03

Ο

J J * ψ

f> 4.00 2.00 0.00

0

2

4 6 Reaction Time (Hrs)

8

10

Figure 4. Effect of Reaction Time on Weight Gain of Fabric. As reaction time increased beyond 4 hours, weight gain decreased, probably because of the hydrolysis of acrylamide in the solution and the partial hydrolysis of ether linkages of carbamoylethylated ramie, i.e. de-etherification, as suggested by Ibrahim etal. (7) Figure 5 shows the relationship between the concentration of the catalyst used and the percentage weight gain. The higher the concentration of NaOH, the greater the weight gain, until the NaOH concentration reached 7.5%, after which gelling occurred on the surface of the fabric. The gelling is due to the extensive crosslinking of acrylamide with cellulose, as well as to self-polymerization under highly alkaline conditions (8-9). Thus, in this study the highest possible concentration of catalyst was 5.0%, offering the least significant side reactions. Moisture Regain. Figure 6 shows the relationship between the weight gain and the moisture regain of carbamoylethylated ramie. Although the increase of moisture regain was not very significant when compared to the untreated ramie, the carbamoylethylated ramie generally showed an enhancement of moisture regain.


113

Thus, the hydrophilic properties of cellulose increased with the addition of amide groups, whereas the addition of other vinyl monomers caused a hydrophobic reaction (10). 12.00


10.00 8.00 α •a ο 6.00 -g 4.00 2.00 0.00 0

2

4

6

8

Concentration of NaOH (%) Figure 5. Effect of Concentration of Sodium Hydroxide on Weight Gain of Fabric. 8.00 7

50

gr I 7.00 00

i

(2 6.50 6.00

Ο

5.50 \ 5.00

- I — 0.00

2.00

4.00

6.00

8.00

10.00

Weight Gain (%) Figure 6. Relation of Moisture Regain of Carbamoylethylated Ramie with Weight Gain. Thermal Behavior of Carbamoylethylated Ramie. The results of the thermogravimetric analysis of thermal behavior are given in Table 2. As the weight gain of the fabric increased, the onset temperature decreased. This resulted in early decomposition of the fibre and delay of the decomposition rate, so the residual amount of the treated ramie was higher than that of the untreated ramie. The addition of amide groups to the cellulose chain thus improved the thermal


114 behavior of ramie, as was reported by Shimada and Nakamura (77) for the graft copolymerization of acrylamide for cotton and for the carbamoylethylation of cotton. Evaluation of Flammability by Limiting Oxygen Index (LOI). The LOI test determines the minimum concentration of oxygen in a flowing mixture of oxygen and nitrogen that will just support a flaming combustion of the material. The limiting oxygen index, expressed as volume percentage, is calculated as follows:


100 «o/.

χ

0~

L·

—

where n% = the limiting oxygen index, 0 = volumetric flow rate of oxygen in mm /s, N = corresponding volumetric flow rate of nitrogen in mm /s. 2

3

3

2

As the weight of the fabric increased, its flammability became correspondingly higher, as shown in Table 2. These results confirm the results of the thermogravimetric analysis, which showed improved thermal stability for carbamoylethylated ramie. Table II. Thermal Behavior of Carbamoylethylated Ramie Residue Weight Onset LOI Experiment Temperature Gain Amount No. (°C) 18 Control 14.51 0 360.10

(%)

(%)

(%)

0.80

357.90

16.43

19

CAA013

3.60

357.20

15.07

20

CAA011

4.60

341.10

17.08

21

CAA002

4.80

336.30

18.22

21

CAA022

7.20

337.70

19.41

22

CAA009

8.40

336.80

22.86

22

CAA019

8.80

330.30

21.19

22

CAA026

11.00

325.40

30.04

24

CAA005

During the pyrolytic degradation of carbamoylethylated ramie, the amide group will decompose to ammonia. The released ammonia, which is an energy-poor fuel, exhibits flame retardant effects by several modes (72-75). The flame inhibitory action is a result of the concentration dilution of the released volatile combustible material from the decomposed cellulose, i.e. the levoglucosan, during the combustion. Tensile Properties of Carbamoylethylated Ramie Fabrics. Tensile strength of the fabrics was measured by standard method A S T M D 5035. The breaking strength of carbamoylethylated fabrics gradually decreased with increasing weight gain. The


115 strength loss ranged from 0 to a maximum of 23% (Figure 7). This result was similar to that of the carbamoylethylated cotton (14).

Ο


•fi

100.00 ^ 90.00 80.00 4 70.00 60.00 50.00 - 40.00 30.00 20.00 10.00 ι 0.00 0.00

• •

1

2.00

4.00 6.00 Weight Gain (%)

8.00

10.00

Figure 7. Strength Retention of Carbamoylethylated Ramie. The loss of tensile strength is due to the addition of amide groups, which are bulkier than the hydroxyl groups, thus reducing the extent of hydrogen bonding between cellulose chains. Nevertheless, the loss of strength is not very significant, as amide groups can also form hydrogen bonds between cellulose chains. Conclusions The application of Michael addition was useful in modifying ramie fibre by using the all-in exhaustion method. The best yield of the reaction between ramie cellulose and acrylamide was obtained at 40°C, a 4-hour reaction, in the presence of 5% NaOH. The carbamoylethylated ramie had better hydrophilicity and thermal properties without significant loss of fabric strength after the reaction. Acknowledgment The authors thank The Hong Kong Polytechnic University for the financial support of this project. References 1. 2. 3. 4.

Frick, J.W.; Reeves, W.A.; Guthrie, J.D. Text. Res. J. 1957, 27, No.2, pp.92-99. Frick, J.W.; Reeves, W.A.; Guthrie, J.D. Text. Res. J. 1957, 27, No.4, pp.294299. Abou-zeid, N.Y.; Anwar, W.; Hebeish, A . Cell. Chem. Technol. 1981, 15, pp.321-330. How, Y.L.; Cheng, K.P.; Lau, M.P. Textile Asia 1991, 22, No.5, pp.74-78.


116 5. 6. 7. 8. 9. Downloaded by UNIV OF MICHIGAN ANN ARBOR on March 18, 2013 | http://pubs.acs.org Publication Date: April 17, 1998 | doi: 10.1021/bk-1998-0688.ch008

10. 11. 12. 13. 14.

Khalil, M.I.; Bayazeed, Α.; Farag, S.; Hebeish, A. Starch/Stärke 1987, 39, No.9, pp.311-318. Feit, B.A.; Zilkha, H. J. Org. Chem. 1963, 28, p.406. Ibrahim, N.A.; Haggag, K.; Abo-Shosha, M . H . Am. Dyestuff Reptr. 1988, 77, No.7, pp.34-42. Thomas, W . M . and Wang, D.W. In Encyclopedia of Polymer Science and Engineering, Herman F. Mark. Ed., 2nd Edition, John Wiley & Sons: New York, 1985, p.185. Kurenkov, V.F. and Myagchenkov, V . A . In Polymeric Materials Encyclopedia, Joseph C. Salamone. Ed., CRC Press, Inc., 1996, Vol.1, pp.47-54. Hebeish, Α.; Guthrie, J.T. The Chemistry and Technology of Cellulosic Copolymers, Springer-Verlag, Berlin-Heidelberg-New York, 1981, p.295. Machiko Shimada and Yoshio Nakamura In Inititation ofpolymerization, ACS symposium series 212, Frederick E. Bailey, Jr. Ed., Bailey, March/April, 1982, pp.237-248. Miller, D.R.; Evans, R.L.; Skinner, G.B. Comb. Flame 1963, 7, pp.137-142. Haynes, B.S.; Jander, H.; Mätzing, H.; Wagner, H.G. 19th Symp. (Intl.) on Combustion, The Combustion Institute, 1982, pp.1379-1385. Grant, J.N.; Greathouse, L.H.; Reid, J.D.; Weaver, J.W. Text. Res. J 1955, 25, N o . l , pp.76-83.


A Preliminary Study of Carbamoylethylated Ramie - ACS Symposium

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