Development of New Methodology for Melting of Plastic: A Chemical Approach

 

Uttiya Dey, Naba Kumar Mondal*, Kousik Das, Jayanta Kumar Datta

Department of Environmental Science, The University of Burdwan, Burdwan, West Bengal, 713104.

*Corresponding Author E-mail: nabakumar_mondal@indiatimes.com

 

Present paper investigated the possible ways for the melting of plastic by chemical method. In chemical dilution method two types of solvents were used, one organic solvent namely acetone and one inorganic solvent namely perchloric acid. The best encouraging result was noted for melting of plastic by organic solvent with acetone. The solvent like perchloric acid, along with heat, can change the physical state of biscuit packet and soft drink glass. No appreciable change was recorded for microwave digestion of plastic with nitric acid and an acid mixture of nitric acid and sulphuric acid. Only in case of biscuit packet and soft drink glass, they became faded and softer than before after digestion with acid mixture. Non-parametric statistics were good fitted with mixed solvent effect rather than single solvent effect with 2% and 37% level of significance respectively.

 

 

 

INTRODUCTION:

During the past few decades the synthetic plastic materials have been excessively used. A single polymer molecule may consist of hundreds to millions of single units called the monomer. The molecule may be linear or branched and the back bone of the molecule is made up of carbon atoms (Dwb.unl.edu., 2011). Plastic is most advantageous because of its light weight, durable, resistant to water and chemical, thermally and electrically insulated (Kathiresan,  2003), these polymers are resistant to biodegradation and microbial attack because there high molecular mass, aromatic rings and unusual bonding etc. (Alexander, 1981) and they are made up of the raw materials extracted from petroleum and natural gas (Dwb.unl.edu., 2011). Their interaction in the environment generates carbon dioxides and dioxins (Huang et al., 1980; Potts et al., 1973), therefore harmful to the environment leading to pollution. However these plastics degrade in the natural environment in a very slow rate. These molecules are too large to be degraded, so they must first be depolymerized into small units. The depolymerized materials can be broken down initially by a number of physical, chemical and biological forces (Swift, 1997). Physical forces like, freezing-thawing, heating-cooling and wetting-drying can initiate mechanical breakdown of many polymers (Kamal and Huang, 1992) Chemical factors like hydrolysis(Göpferich, 1997), dissolution into different solvents like toluene, benzene and cyclobenzene(Abdulkareem and Garba, 2005).

 

Abiotic oxidation, such as auto-oxidation which reduce the molecular weight (Albertsson, 1993; Day et al., 1997), oxidation by air pollutants like ozone, SOx and NOx (Horrocks, and D’Souza, 1992) and oxidation by sunlight which strikes the surface of the polymer, being absorbed, oxidized the material (Osawa, 1992), can also initiate degradation.

 

Keeping in mind the above facts, this present study have been formulated to find out suitable methodology for melting of plastic. So that it can minimize the plastic based solid waste problem.

 

MATERIALS AND METHODS:

Nine types of commonly used plastic were considered for this study and all the samples were cut into small chips (0.2-0.5 cm).

Chemical dissolution method (Abdulkareem and Garba, 2005)

Set-1

0.25 g of each plastic samples were dipped into 10 ml of acetone and incubated for 24 hours at 60⁰C temperature. After 24 hours the samples were separated from acetone, sun dried and the final weight of the samples were measured.

Set-2:

0.25 g of each plastic sample was dipped into 10 ml of perchloric acid, incubated for 24 hours at 60⁰C temperature and after 24 hours the samples were separated from acid, sun dried and the final weight of the samples were measured. A similar experiment was done with perchloric acid but in boiling condition.

 

Table -1: Interaction results of plastic-acetone.

Sample	Temp.	Color		Form of plastic		Weight(g)		Acetone volume(ml)
		Initial	Final	Initial	Final	Initial	Final	Initial	Final
1.	Same	Transp.	White	Chips	Liquid	0.25 g	0.25g	10 ml	6.5 ml
2.	Same	Black	Black	Chips	Chips	0.25 g	0.25 g	10 ml	8.7 ml
3.	Same	Pink	Pink	Chips	Liquid	0.25 g	0.25 g	10 ml	6.7 ml
4.	Same	White	White	Chips	Chips	0.25 g	0.25 g	10 ml	8.9 ml
5.	Same	Orange	Orange	Chips	Chips	0.25 g	0.25 g	10 ml	6.9 ml
6.	Same	Yellow	Yellow	Chips	Liquid	0.25 g	0.25 g	10 ml	7.5 ml
7.	Same	White	White	Chips	Chips	0.25 g	0.25 g	10 ml	8.8 ml
8.	Same	Blue	Faded	Chips	Chips	0.25 g	0.25 g	10 m	6.2 ml
9.	Same	Blue	Faded	Chips	Liquid	0.25 g	0.25 g	10 ml	6.4 ml

 

Table-2: Interaction result of plastic-perchloric acid

Sample	Weight(g)		Color  of  sample		Form  Of  Sample		Volume  of  PCA		Colour  of  PCA
	Initial	Final	Initial	Final	Initial	Final	Initial	Final	Initial	Final
1.	0.25 g	0.25 g	Transp.	Transp.	Chips	Chips	10 ml	8.7 ml	Transp.	Transp.
2.	0.25 g	0.25 g	Black	Black	Chips	Chips	10 ml	8.9 ml	Transp.	Transp.
3.	0.25 g	0.25 g	Pink	Pink	Chips	Chips	10 ml	8.3 ml	Transp.	Transp.
4.	0.25 g	0.21 g	White (red print)	Print faded	Chips	Chips	10 ml	8.8 ml	Transp.	Brown
5.	0.25 g	0.25 g	Bright orange	Faded	Chips	Chips	10 ml	7.9 ml	Transp.	Yellow
6.	0.25 g	0.25 g	Yellow	Yellow	Chips	Chips	10 ml	8.3 ml	Transp.	Transp.
7.	0.25 g	0.25 g	White	White	Chips	Chips	10 ml	8.8 ml	Transp.	Transp.
8.	0.25 g	0.20 g	Blue	Faded	Chips	Chips	10 ml	7.8 ml	Transp.	Bluish
9.	0.25 g	0.25 g	Blue	Faded	Chips	Chips	10 ml	7.7 ml	Transp.	Pale

 

Table-3: Result of plastic-perchloric acid interaction with heat.

Sample	Weight(g)		Color  of  sample		Form  of sample		Volume  of  PCA		Color  of  PCA
	Initial	Final	Initial	Final	Initial	Final	Initial	Final	Initial	Final
1.	0.25 g	0.25 g	Transp.	Transp.	Chips	Became smaller	10 ml	8.9 ml	Transp.	Transp.
2.	0.25 g	0.25 g	Black	Black	Chips	Chips	10 ml	8.8 ml	Transp.	Transp.
3.	0.25 g	0.25 g	Pink	Pink	Chips	Became smaller	10 ml	9.1 ml	Transp.	Transp.
4.	0.25 g	0.23 g	White with red print	Print became faded	Chips	Chips	10 ml	8.8 ml	Transp.	Pale
5.	0.25 g	0.22 g	Orange	Faded	Chips	Became smaller and softer	10 ml	8.2 ml	Transp.	Deep brown
6.	0.25 g	0.25 g	Yellow	yellow	Chips	Became smaller	10 ml	8.4 ml	Transp.	Transp.
7.	0.25 g	0.25 g	White	White	Chips	Became smaller and clumped	10 ml	8.3 ml	Transp.	Transp.
8.	0.25 g	-------	Blue	Brown	Chips	Dissolved & formed a jelly like material	10 ml	--------	Transp.	Deep brown
9.	0.25 g	0.25 g	Blue	Faded	Chips	Became smaller	10 ml	7.9 ml	Transp.	Pink

 

Table-4: Result of acid mixture digestion.

Sample	Weight(g)		Color  of  sample		Form  of sample		Volume  of  acid  mixture(ml)		Color  of   HNO3
	Initial	Final	Initial	Final	Initial	Final	Initial	Final	Initial	Final
1.	0.25 g	0.25 g	Transp.	Transp.	Chips	Chips	25	23.7	Light yellow	Light yellow
2.	0.25 g	0.25 g	Black	Black	Chips	Chips	25	22.9	Light yellow	Deep yellow
3.	0.25 g	0.25 g	Pink	Pink	Chips	Chips	25	23.8	Light yellow	Light yellow
4.	0.25 g	0.25 g	White with red print	print became faded	Chips	Chips	25	24	Light yellow	Reddish
5.	0.25 g	0.25 g	Orange	Orange	Chips	Chips	25	23.5	Light yellow	Light yellow
6.	0.25 g	0.25 g	Yellow	Yellow	Chips	Chips	25	24.1	Light yellow	Light yellow
7.	0.25 g	0.25 g	White	White	Chips	Chips	25	23.3	Light yellow	Light yellow
8.	0.25 g	0.25 g	Blue	Faded	Chips	Become soft	25	23.6	Light yellow	Light blue
9.	0.25 g	0.25 g	Blue	Faded	Chips	Become soft	25	23.9	Light yellow	Light blue

 

Microwave digestion method (Sakurai et al., 2006)

0.25 g of each sample was digested with 25 ml of nitric acid and an acid mixture of nitric acid and sulfuric acid (4:1) at 300 watt for 10 minutes. After digestion the samples were separated from acid, sun dried and the final weight of the samples were measured.

 

Statistical interpretation:

Data were statistically analyzed by non-parametric statistics, χ² by using SPSS 16 software package.

 

RESULTS:

Chemical dissolution of plastic

After dipping the plastic into acetone no sample showed significant weight change. The different varieties of plastic showed different volume of acetone after 24 hours. One significant observation was found for plastic tea cups which are available in the market in different colors and transparent also. In this study four varieties of tea cup were considered like transparent, pink, yellow, and blue in color. After dipping this plastic materials into acetone medium, immediately all these varieties of plastic changes their physical nature from hard to liquid plastic like chewing gum (Abdulkareem and Garba, 2005) (Fig.1),  without any changes in color of the solvent except blue color Pepsi glass which showed almost white in color after 5 to 10 minutes (Table-1) and the solvent turned blue. The results of perchloric acid test revealed that only four varieties of plastic material change their color with respect to original color (Table-2). But other plastic does not showed any color change after 24 hours. Again, it was found that only two varieties of plastic, namely white carry bag with red print and the biscuit packet change their weight after 24 hours of incubation (Table-2). In boiling condition no variety of plastic showed weight change except the white carry bag with red print and the orange chips packet where 8% and 12% weight change were recorded (Table-3). On the other hand  no weight change has been recorded for the biscuit packet  after boiling with PCA because of technical problem.

 

Fig: Change of physical state of plastic cups, from hard to liquid plastic after dipping into acetone.

 

Microwave digestion

The result of microwave digestion indicates that there is no neat change of physical state change of all plastics. But digestion with acid mixture, a little color change was recorded for the white carry bag with red print. The soft drink glass became soft after digestion with acid mixture (Table-4).

DISCUSSION:

Chemical dissolution of plastic

The interaction effects of organic solvent acetone with different variety of plastic showed different amount of solvent adsorption due to varietal variability. The plastic cups became soft like chewing gum after interaction with acetone (Abdulkareem and garba, 2005). This can reduce the huge solid waste problem and from the liquid state of plastic it can be recycled. Four varieties of plastic namely white carry bag with red print, orange chips packet, biscuit packet and blue soft drink glass, change their color after interaction with PCA, this is due to their compositional pattern, the color became dissolved into the PCA. The white carry bag with red print and the biscuit packet also showed weight change, the cause of this is probably the presence of some soluble compounds which release after interaction with PCA and subsequently volatilized. In boiling condition also the white carry bag with red print and the chips packet showed weight change because of the same cause. The weight of the biscuit packet cannot be taken because after boiling with PCA the sample melted and mixed with the solvent and form a deep brown color, jelly like substance from which the dissolved plastic cannot be separated by WATTMAN-41. The output of the entire experiment was calculated on the basis of non-parametric statistics and it was found that the data are good fitted for mixed effect rather than single solvent effect with 2% and 37% level of significance for perchloric acid and heat and nitric acid and sulphuric acid respectively.

 

Microwave digestion

Microwave digestion of plastic with inorganic acid indicates that the plastic are not inorganic acid sensitive.

 

CONCLUSION:

From this particular study, it may be concluded that the organic solvent like acetone is the best for melting the plastic cups from solid state to soft semi-solid state. But other variety of plastic did not show any remarkable change of their physical characteristics. The solvent like PCA can change the physical state of biscuit packet and soft drink glass from harder to softer state. Boiling with PCA make the biscuit packets dissolved in to the solvent. From the microwave digestion study it was found that none of the composition are suitable for degrading any variety of plastic except white carry bag with red print and soft drink glass. When digesting with the mixture of HNO₃ and H₂SO₄ , the biscuit packet showed the color change i.e., the red print on it became faded and the solution became reddish. Similar observation was noted for soft drink glass. Again from non-parametric statistics it was found that the data are good fitted for mixed effect rather than single effect with 2% and 37% level of significance respectively.

 

ACKNOWLEDGEMENT:

Authors express their sincere thanks and like to extend their gratitude to all the helping hands whose active participation helps to execute this research work.

 

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Received on 25.01.2012         Modified on 12.02.2012

Accepted on 22.02.2012         © AJRC All right reserved