case of the polymer banknote sheets. The ageing process was used to study the resistance of the sheets to the heating. (3-5) . The treatment of cellulose by ...
Comparative Study of Accelerated Ageing & Solvents’ Effects on the Printing of both Paper & Polymer Banknotes A.M.A.Nada 1, M.Y. El-Kady 2, G. Simonian 3, R.F.Basalah 4 and A.S.Goher 5. 1- Cellulose of paper depart., NRC ,Dokki, Cairo, Egypt ,2-Faculty of Science ,Ain shams Unv , Cairo ,Egypt ,3- Fac .Applied Art ,Helwan Unv .,Gza .,4-General Director, Medico-Legal Department, Ministry of Justice, Egypt, 5- Forensic Question Document Expert, Medico-Legal Department, Ministry of Justice, Alex., Egypt.
Abstract:-
Change in Lab colour values before & after washing of paper (natural) and polymer (synthetic) banknotes were measured & the E values were calculated. Change in Lab colour values of paper and polymer banknotes before & after treating with solvents (NaOH – HCl Acetone) were measured & the E values were calculated. Change in Lab colour values before & after accelerated ageing of paper and polymer banknotes (50 - 100 - 120 - 140 - 160 - 180 - 200 degrees C) were studied and the E values were calculated. Change in Lab colour values according to humidity effects (0% - 5.8% - 78.8% - 95.8%) were investigated & the E values were calculated. It was found that both the paper & polymer banknotes showed no significant changes in both Lab colour values before & after washing & in the presence of different humidity percentages. Paper banknotes were better with Na OH & Acetone treatments, & when exposed to higher temperature degrees, while polymer banknotes were better with HCl treatment. All the foresaid are presented as measurements, enlarged photos & graphs, followed by discussions & analysis.
Keywords, natural (paper) and synthetic (polymer) banknotes sheets, accelerated ageing, solvents, printing, Lab values.
Introduction:Counterfeiting is an ever present threat for universal economy. Nowadays that threat loomed even larger as improvements in the quality of color photocopiers, computer scanners and imaging software, accompanied by falls in the cost of such technologies, brought high quality counterfeits within the reach of unskilled "casual" counterfeiters. A new creative experiment appeared based on changing the traditional rag security paper to synthetic polymer substrate of polypropylene
(1)
.
There are two viewpoints, one supports the use of synthetic banknote, because it is more durable, has a clear window, (which is an effective optical security device), cleaner and more hygienic because of its nonporosity (2). The other viewpoint is conservative to the synthetic polymer, due to the fact that the natural banknotes (paper) are more effective than synthetic ones to face money counterfeit by most counterfeiting ways. So, paper banknotes are well established technology because of watermarks and security threads which are within the fibers, in addition to the printing methods and printing inks interaction with the natural banknotes sheets, due to its porosity, absorption and not adsorption as in case of the polymer banknote sheets. The ageing process was used to study the resistance of the sheets to the heating (3-5). The treatment of cellulose by modification of its structure physically as swelling, or chemically by incorporation of different functional groups or cooling with different properties, has a higher effect of the persistence of cellulose than any polymer toward ageing process (6). In addition, the thermal analysis of cellulose and its modification when exposed to ignition source, will decompose and produce among other things gaseous products and further decompose until only ash remains. Chemical modification or coating of natural polymers aims to obtain a
new material that can be reflected in their thermal decomposition (6-10). It is seen that the pyrolysis reaction follow first order kinetics (11). The aim of this study is to make a comparative Study of accelerated Ageing & Solvents’ Effects on the Printing of both Paper & Polymer Banknotes. In a previous paper entitled" Thermal Behavior of Natural and Synthetic Polymer Banknotes" the authors investigated several elements and properties of both banknotes. The conclusion was: (1) Breaking length and burst factor of polymer banknote sheet are higher than that in case of paper (natural polymer) banknote sheet. (2) Tear factor of paper (natural polymer) sheet is higher than that in case of polymer sheets. (3) Paper banknote sheet is more resistant to thermal treatment than the polymer sheet. The weight loss percentage in the initial (minor) and major decomposition temperature of the paper sheet is higher than the polymer sheet. (4) Practically the mechanical properties of the paper banknote sheet are measured after ageing from temperature 100-200ºc for different time intervals. While the mechanical properties of the polymer sheet is highly affected after heating at 80ºc and gives unregulated results. (5) Kinetic energy calculated from mechanical proprieties (breaking length) of aged paper sheets is higher than that in case of the polymer sheet.
In general, the paper banknote sheets have a higher resistance to thermal treatment than the polymer sheets.
Experimental -Two kinds of banknote sheets were used: a) Sheets of 25 Egyptian Piasters paper (natural polymer) sheets. b) Sheets of 10,000 Romanian Lei polymer (synthetic banknote) sheets. a) Change in Lab values before and after washing. Paper and polymer banknote sheets were placed in an automatic washing machine for a complete washing cycle using a commercial detergent. After washing, Lab values of several colours were measured using a spectrophotometer (Spectro Eye) from Gretag Macbeth. All data recorded were the average of several measurements before and after washing. b) Change in Lab values before and after treating with five different kinds of most widely used solvents as follows: Sodium hydroxide, Hydrochloric acid (both of different normalities), Benzene, Acetone and Ethyl Acetate. Both banknotes were placed in a sockslet and refluxed for two hours. Lab colours were measured again before and after the treatment. c) The effect of accelerated ageing on the colour and printing properties on the paper banknote sheet between 50 and 200ºC for different periods were investigated using a special oven. Accelerated ageing of the polymer sheets is carried out at 50ºC, and increasing the temperature to 80ºC deteriorated the sheet and gave unregulated value. So the thermal treatment of the paper sheets was completed to 200ºC. d ) Chang in Lab values according to humidity effects using four different humidity percentages as follows: 0% - 5.8% -78.8% and 95.8%. All data recorded were the average of several measurements. Also all samples were magnified and photographed digitally using a digital Microscope (Techkon-DMS 910).
Results and Discussion: Lab Colour Values: Lab is the best neutral way ISO certified to measure colours,where (c) is the Lightness (0-100%) (a) and (b) are colours co-ordinates (x,y) to determine the colours' position in the Lab colour circle.
E=
{(L1-L2)2 + (a1-a2)2 + (b1-b2)2}
The Lab values before any treatments were : L
a
b
Paper banknotes
92.58
- 0.59
-2.97
Polymer banknotes
88.43
- 10.59
17.38
a) Change in Lab values before and after washing: No significant changes occurred.
b) Change in Lab values before & after treating with solvents (Na OH – HCl – Benzene – Acetone – Ethyl Acetate) :
Romanian Banknote at Room temperature.
Effect of 0.1 N HCl on Romanian Banknote
While with the Egyptian paper banknotes, the HCL destroyed them completely.
Lightness
Effect of NaOH on the Lightness of Egyptian Banknotes 100 98 96 94 92 0
0.5
1 Normality
1.5
Effect of NaOH on Lightness of Romanian Banknotes
Lightness
105 100 95 90 85 0
0.1
0.2
0.3
0.4
0.5
0.6
Normality
Effect of 0.1 N NaOH on Egyptian Banknotes
Effect of 0.1 N NaOH on Romanian Banknotes
c) Change in Lab values before & after accelerated ageing: (50 - 100 - 120 - 140 - 160 - 180 - 200 degrees C): The Egyptian banknotes: Effect of Temprature on Colour at 100 C 0 -2.5
-2
-1.5
-1
-0.5
-1 0 -2 -3 -4 -5
Egyptian banknote at room temperature
Effect of temperature of Egyptian banknote at 100 C after 3 hours
Romanian Banknote at room temperature
Egyptian Banknote at room temperature
Lightness
Effect of temprature on Lightness at 160 C (Egyptian Banknote) 94 92 90 88 86 0
2
4
6
8
Hours
Effect of temprature on Colour at 160C (Egyptian banknote)
-2.5
-2
-1.5
-1
-0.5
Egyptian banknote at room temperature
3 2 1 0 -1 0 -2 -3 -4
Egyptian banknote at 160C temperature after 0.5 hour
Egyptian banknote at 160C temperature after 6 hour
Lightness
Effect of Temprature on Lightness at 200 C (Egyptian Banknote 94 92 90 88 86 0
0.5
1 Hours
1.5
2
Effect of Temprature on Colour at 200 C (Egyptian Banknote) 20 15 10 5 0 -3
-2
-1
-5 0
1
2
3
4
Egyptian banknote at room temperature
Egyptian banknote at 200C temperature after 0.25 hour
Egyptian banknote at 200C temperature after 1.5 hour
d) Change in Lab values according to humidity effects: (0% - 5.8% - 78.8% - 95.8%)
Lightness
Effect of 0% Humidity on Lightness in 10 days on Egyptian 93 92 91 90 0
2
4
6 Days
8
10
12
Effect of Zero % Humidity on Egyptian Banknote after one Day
Effect of Zero % Humidity on Egyptian Banknote after 10 Days
Egyptian banknote after 1 day at 5.8% Humidity
Egyptian banknote at room temperature
Egyptian banknote after 10 days at 5.8% Humidity
Egyptian banknote at room temperature
Effect of 78.8 % Humidity after one day
Egyptian banknote at room temperature
Effect of 95.8 % Humidity after one day
Effect of 95.8 % Humidity after 10 days
Effect of Humidity on Lightness 100 98 96 94 92 90 88 86 84 82 80
5.8%
78.8%
1
2
95.8%
0%
3
4
Conclusion:a) Change in Lab colour values before and after washing showed that nearly no significant changes occurred in both banknotes. b) Change in Lab colour values before and after solvents' treatments, showed that: 1) With NaOH (Normalities from 0.1 to 1 N) paper banknotes were affected slightly with a 3% increase in lightness. Whereas for the polymer banknote, the colours were completely removed first, followed by the white background, being at the end completely transparent. 2) With HCL (normality from 0.1 to 1), the paper banknote was completely destroyed. The polymer banknote was slightly darkened (about 5% decrease in lightness). 3) With Benzene, the total colour change with the Egyptian banknote after the treatment was about 5 Delta E, whereas with the polymer banknote the total colour change was more, with a figure of 7.5 Delta E. 4) With Acetone, the total colour change with the Egyptian banknote after the treatment was about 4 Delta E, whereas with the polymer banknote the total colour change was more, with a figure of 7.2 Delta E. 5) With Ethyl Acetate, the total colour change with the Egyptian banknote after the treatment was about 3.7 Delta E, whereas with the polymer banknote the total colour change was more, with a figure of 5.8 Delta E. The foresaid means that the colour changes in case of the paper banknotes were less than the polymer banknotes, with the treatments of Na OH, Benzene, Acetone and Ethyl Acetate, while it was more with the HCL.
c) Change in Lab colour values with accelerated ageing, showed that: Paper banknote starting from room temperature till 160 C was nearly not affected, at 200 C it was slightly faded (3%) and yellowished (15 – 20%).
d) Change in Lab colour values with different humidity percentages, showed that: Polymer banknotes were not affected by humidity at all, also paper banknotes were not affected at the different humidity percentages.
Summary: - Paper banknotes were better with Na OH treatment and accelerated ageing. - Polymer banknotes were better with HCL treatment. - Both were the same with washing and humidity treatment.
