A Comparative Study of Physical Behaviour and Biodegradation of Metalized and Non-Metalized Polypropylene Films
1Department of Chemical Engineering, University of karachi, Karachi, 75270 Pakistan
2Institute of Environmental Studies, University of karachi, Karachi, 75270 Pakistan
3Pakistan Council of Scientific and Industrial Research (PCSIR), Karachi, Pakistan
Corresponding author Email:neelamsaleem131@yahoo.com
DOI:http://dx.doi.org/10.12944/CWE.14.2.11
The goal of this study was to analyze the physical properties of metalized and non metalized cast PolyPropylene (CPP) plastic films with respect to its degradation and environmental pollution. The PP films of 20 microns were produced by standard cast film extrusion process i.e. metalized PP films coated by aluminium and others without any coating. The samples were manufactured at an industry which produces food grade plastics made by a cast co-extrusion process. Physical properties like Tensile strength, Oxygen transmission rate and water vapour transmission rate measured as per ASTM standard. Results show that non-metallized film has a range of WVTR 6-8g/m2/day and OTR range 2300-2500cc/m²/atm/day. However, metalized PP film shows about 50% to 80%improvement in the OTR and WVTR. It has been proven that metallization with aluminium has improved the physical properties but affect the rate of degradation.
In the current study, the extent of degradation of plastic by fungal colonization(Aspergillus and Pencilliumspp) was measured by the structure investigation using FTIR spectroscopy, results indicate fewer changes in the peak after exposed to the fungi in synthetic media. The spectrum peak in the control on non-metalized film observes at 37736 cm-1, 38913 cm-1and 6742 cm-1, which are absent after degradation. Similarly in metalized plastic peaks at 3779.8 cm-1, 3771.1 cm-1, 2357.2 cm-1and 2007.2 cm-1were disappeared after degradation. This variation in peaks indicates fungi use the plastic as the source of carbon. These samples were tested for their degradation properties with respect to the physical properties. Both samples took for 30 days of degradation. It is found that non-metalized films degraded effectively in the mean period of time.Copy the following to cite this article:
Ishteyaq S, Neelam A, Hany O, Mahmood S. J. A Comparative Study of Physical Behaviour and Biodegradation of Metalized and Non-Metalized Polypropylene Films. Curr World Environ 2019; 14 (2). DOI:http://dx.doi.org/10.12944/CWE.14.2.11
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Ishteyaq S, Neelam A, Hany O, Mahmood S. J. A Comparative Study of Physical Behaviour and Biodegradation of Metalized and Non-Metalized Polypropylene Films. Curr World Environ 2019; 14 (2). Available from:https://bit.ly/2m2dEHy
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Article Publishing History
Received: | 2019-02-13 |
---|---|
Accepted: | 2019-04-30 |
Reviewed by: | HOSSEIN MOHAMMAD HOSSEINI |
Second Review by: | Guangming Li |
Final Approval by: | Dr. Gopal Krishan |
Introduction
The basic purpose of packaging is to provide protection from the environmental condition by maintaining the quality of food items from the manufacturing industry to normal consumers. The most important physical property in flexible packaging materials is water vapour and oxygen gas transfer rate.1The transfer rate depends on the type of the plastic, gas molecules quantity, the interacting time between gas and plastic.2因此,包装材料是特殊的障碍on the high demand for the packaging of oxygen-sensitive food items. Whereas other properties like tensile strength, optical properties, thickness, gloss, printability, transparency, international and local food legislation.3目前塑料manufa来满足这种需求cturing industries use additives, multilayers formation by using different polymers only few can be utilized due to crystal structure. The co-extrusion technique is mostly used for manufacturing of multilayer plastic films based on polypropylene(PP), High-density polyethylene (HDPE), Low-density polyethylene (LDPE), Polyethylene terephthalate(PET)etc. with suitable oxygen barrier material like Ethylene Vinyl alcohol ( EVOH). However traditionally low-cost aluminium coating with (Cast polypropylene) CPP, PET has been used as a good barrier just by increasing few micrometre thicknesses by a metallization process.4But aluminium will restrict gas and water if the thickness of plastic sheet above 25.4μm.5Whereas, it may produce small hole or stress if manufactured in less thickness. Incorporation of aluminium into a film by lamination process better option but costly as compared to co-extrusion.
It is also very important to mention here that aluminium coated plastic materials are not recyclable and hence causes excess wastage.6The key objective of the sustainable food packaging system is to maintain excellent quality of the packaged items, safe handling, minimizing post-harvested based loses and wastages. In developing countries like Pakistan about 25 to 50% food losses occurs due to improper food processing and packaging problems.7However it is also proven that chemicals from packaging also migrate to the food items after some time of packing, the main hazards of these types of migrations on food safety has several questions if quantity of these migrated chemicals in food items greater than the specified standard, which can be minimized after adding some additives or metallic coating. The monitoring of migration is an important aspect of food quality.8
Plastic film with new intelligent technologies is one of the fastest growing forms of packaging with a number of benefits. At that minute, it is seen as an environmental burden, emission of Greenhouse gases (GHS) and wasting resources. The high hydrophobic level and the high molecular weight of Plastic makes it non-biodegradable and lethal of marine biota and vector of harmful algae and bacteria species transportation in floating water bodies.16,17By natural cycle degradation of PP is slow it is initiated by both biotic and abiotic factors of the environment. On the molecular symmetric continuous chain of methylene and absence of functional groups make it poor to microbial attachment thus resistant to biodegradation.18The aim of the present research is to investigate and understand the physical properties of metalized and non- metalized PP film used in packaging industries with its potential effects on the environment.
Material and Method
Preparation of Polypropylene(PP) Samples
In this study, the PPmgranules purchased from Chemicals suppliers Ltd. with densities 0.9g/cc and melt flow index 8g/10min were used. Six samples of metalized and non-metalized types of PP films were manufactured by Cast extrusion process as shown in the process flow diagram Fig 5. According to which PP granules additives enter through hoppers into the extruder (Ext-01) of Filmax701 model, Mitsubishi, then melted (temperature 210 to 285oC) PP granules introduces into the die Plug (D-0001). The finished plastic cools with chill roller machines (15 to 22oC). Finally, Corona treatments were used to increase the surface tension. After that PP Film moves to wind section where the extruded film converted into film rolls. Similarly, metalized CPP films were produced by using Vacuum metalized (Model No: K5000)by adding a thin film of aluminium to PP films. The thickness of non metalized (20microns) and metalized PP films(60 microns) were measured by automatic gauge meter during the production. Physical test of Manufactured Polypropylene Plastic Film:
To analyze the biodegradation properties of metalized and non metalized PP films some physical test of the sample were performed as per American standard testing methods (ASTM)
First of all tensile and elongation test of both types of PP films were conducted by the universal tensile tester (AG-X Shimasdzu, Autograph, Japan) according to ASTM D- 882 methods, the PP films were conditioned for 48 hours at 25oC about 50% relative humidity(RH).The samples were cut in specific shape and strips(100 x 10 mm)then tensile strength measured in both directions i.e. in the machine(md) and transverse direction(td) , since they can vary considerably from one direction to another, theMeasurement was based on six replicate of each sample.
Similarly, barrier properties in terms of water vapour transmission rate (WVTR) and oxygen transmission rate(OTR) of the sample were tested in accordance with American standard testing method. The PP samples tested for WVTR at 80 to 90% relative humidity (RH) and 20-25oC by means of a special type of permeability cups as per ISO 2528 and as mentioned by Lopez-de-Dicastillo.23These cups were filled specifically with silica gel then sealed with the sample pp films. However, the cups were stored in desiccators to maintain the required humidity. The cups were weighed and the increase in weight versus time was used to calculate WVTR. These values were then divided by water vapour gradient and multiplied by sample thickness to obtain the exact value.
Similarly, the oxygen transmission rate (OTR) of the non-metallized and metalized PP films was measured at 23°C with 50 to 55% RH. First of all PPfilm samples were clamped in a diffusion chamber of the OTR analyzer. Pure oxygen (99.9%)was introduced into the upper half of the chamber whereas nitrogen(99.999 % zero grade N2) carrier gas flows through the lower half. The oxygen transmission rate of both types of PP films was displayed as (cc/m2/atm/day).
Figure 1: FTIR result of Non-metalized PP with control (Red) and treated with fungi ( Blue) spectrum. Click here to view Figure |
Figure 2: FTIR analysis result of metalized (red spectrum control) and metallized film (purple spectrum) after treated with fungi. Click here to view Figure |
Degradation Test
The samples of metalized and non metalized PP films were further analyzed for their biodegradation properties. The samples were washed aseptically with alcohol and poured into sterile Sabouraud Dextrose Agar and consortium ofAspergillus sppandPenculliumspprespectively. The plates were incubated at 28°C for one week. After incubation, the plastic with fungus growth transfer into the minimal media (MgSo4.7H2O (1gm/L), FeSO4(0.002g/L), NaCl (0.2g/l), K2HPO41O.5 g/l), KH2PO4(0.08 gm/l), NH4NO3(2.0 g/l) and Agar (0.7%) containing no source of carbon accept plastic.19
Figure 3: SEM photomicrographs of metalized cpp film exposed byAspergillus sppandPencilliumsppat(a)500x (b)1000X (c)7000x (d)10,000x (e)15000x respectively after 30 days of incubation Click here to view Figure |
Figure 4: SEM photomicrographs of Non-metalized cpp film exposed byAspergillus sppandPencilliumsppat(a)500x (b)1000X (c)7000x (d)10,000x (e)15000x respectively after 30 days of incubation Click here to view Figure |
After the interval of 02 months the weight of plastic measured by the gravimetric method by using ASTM D6003-96.14Change in the chemical structure of the plastic film was recorded by using Fourier Transform infrared (FT-IR)(Thermo Scientific Nicolet TM iS10), from a wave number of 400–4000 cm-
Scanning Electron Microscopy (SEM)
The PP film after incubation period with fungal stains was removed and dried in Petri plate for 24 hours. The sample was coated with 300°A gold and analysis under a high-resolution electron microscope (Jsm-6380 A, Japan).
Figure 5: Mean strum test result of metalized and non metalized film Click here to view Figure |
Strum Test
Strum test (OECD 301B: ASTM D5209) was used for the evaluation of biodegradability of polymer material. The sterile piece of film was added to 300 mL basal salt medium as the only carbon source. Spore suspension ofAspergillus nigerandPenicilliumspp were used for the degradation of polyethene. Control bottles were prepared without any plastic. degradation test was performed at room temperature for the duration of four weeks. Before set the system Ba (OH)2filtered and stored in the airtight bottles to prevent atmospheric contamination of CO2absorption in the system. Evolution of carbon dioxide, which was trapped in absorption bottle containing 0.01M, Ba(OH)2was monitored every week, The amount of CO2evolved during the test duration was measured by the gravimetric method. As BaCO3is insoluble in water and formed precipitates as it is shown in Eq. 1.
Ba(OH)2 +CO2→ BaCO3+ H2O
Results and Discussion
Material Characteristics
包装材料的屏障性质是responsible for product quality deterioration, the detailed understanding of the characteristics of coated films is great practical and commercial importance. Generally, polypropylene film has a good barrier to moisture vapours and low barrier to oxygen transmission. But by manufacturing the CPP films with standard PP granules after metalized coating shows better results in terms of OTR barrier as well as other properties. Results are based on the six samples of each metalized and non-metalized cast polypropylene film. From data are given in Table 1 substantial differences between the barrier properties of the investigated coated and uncoated cast, PP films were estimated. To make the polymer more stable in terms of barrier properties a thin layer of metal i.e. Aluminum (Al), aluminium oxide (AlOx), silicon oxide (SiOx), or magnesium oxide (MgOx)is used [20]. Table 1 includes the properties of non-metalized and metalized cast polypropylene film with aluminium coating. Results show that cast polypropylene film without metallization has high WVTR which is not acceptable for some food packaging industry. But after metalization with aluminium PP films results proved to be better.
Table 1: Comparative study of the Tensile and Barrier Properties of the Non metalized and Metalized PP Films
Non-Metallized |
Metallized |
|||||||||
samples |
Thickness (micron) |
Oxygen transmission rate (cc/m2/day) |
Water vapor transmission rate(g/m2/day) |
Tensile strength (N/mm2) |
Thickness (micron) |
Oxygen transmission rate (cc/m2/day) |
Water vapor transmission rate(g/m2/day) |
Tensile strength (N/mm2) |
||
1 |
20 |
2500 |
6 |
MD |
53 |
60 |
90 |
0.7 |
MD |
50 |
TD |
25 |
TD |
25 |
|||||||
2 |
20 |
2500 |
6 |
MD |
52 |
60 |
98 |
0.72 |
MD |
51 |
TD |
26 |
TD |
26 |
|||||||
3 |
20 |
2490 |
6.1 |
MD |
54 |
60 |
95 |
0.68 |
MD |
50 |
TD |
22 |
TD |
24 |
|||||||
4 |
20 |
2450 |
6 |
MD |
52 |
60 |
91 |
0.70 |
MD |
49 |
TD |
23 |
TD |
24 |
|||||||
5 |
20 |
2480 |
6.2 |
MD |
55 |
60 |
98 |
0.71 |
MD |
51 |
TD |
24 |
TD |
26 |
|||||||
6 |
20 |
2500 |
6 |
MD |
55 |
60 |
100 |
0.71 |
MD |
50 |
TD |
25 |
TD |
25 |
Biodegradebilty Results
Synthetic polymeric materials have been widely used because of low density, cheap in cost and good possibility. To make the polymer more stable in the environmental condition a thin layer of metal i.e Al is used.20However, the biodegradability is considerably less, and the materials easily accumulate in the environment. Polypropylene (PP) is one of such synthetic polymeric constituents and is known as a non-biodegradable one. Generally, large molecule such as PP cannot easily enter into cells of microorganisms. Therefore, PP is hard to be metabolized in microorganisms.9-10The microorganism once attached to the surface on the plastic used it as the sole source of carbon, leading to the formation of a low molecular fragment of polymer i.e. oligomer or monomers.12The biodegradation of plastics by bacteria and fungi proceeds differently under different conditions according to their properties. The different factors that rule biodegradation are a type of organism, polymer characteristics.11Our result is somehow is the same in case of metalized and non-metalized pp film, FTIR results show very few changes in the peak after exposed to the fungi in mineral media. The spectrum peak in the control of non-metalized film observe at 37736 cm-1, 38913 cm-1and 6742 cm-1, which are absent after degradation with fungi consortium namelyAspergillussppandPencilliumspp.Similarly in metalized plastic peaks at 3779.8 cm-1, 3771.1 cm-1, 2357.2 cm-1and 2007.2 cm-1were disappear after degradation with fungal species. Peak shifted is also recorded in the region of 1500-1000 cm-1(Fig-1 and Fig 2). The results indicated the far acceptable degradation of the metalized film as compare to un-metalized, but somehow it can be due to the removal of metallization layer on pp film. The shift of peaks and new peak formation in the spectrum is the sign of degradation which is due to the enzymes produced by microorganism once it's attached to the surface and used the subtract as a source of their food.Aspergillussppwere reported as the degrading agent of Polyethylene film, the rate of degradation reported as 26% in 6 months.12Khanet al。,13proved that the degradation of Polyurethane film (PU)up to 90% byAspergillustubingensis.He observed the changes in the spectrum at 3321 cm-1作为hydrogen bond (NH), which is absent in control. He reported these changes as a sign of degradation and formation of new products in degradation. Similarly, weak band generate at the shoulder of band 2954.8 cm-1in the sample spectrum which is also absent in control.
Scanning electron microscopy (SEM) images of film samples after degradation test revealed the significate surface degradation and structural changes of Metalized and non metalized PP film at a resolution of 500x to 15000x. In the present work Incubated Film colonized by fungi shows important morphological changes i.e formation of cavities and erosions (fig 4 & 5). The observed rough and erosion Surface by fungal is the primary reason of mass loss. SEM photographs of control polyethene did not show any disruption on the surface. These results show thatAspergillussppandPencilliumspp could utilized metalized and non metalized film and promote their growth mechanism. The Cracks and holes appeared in film after degradation is due to the dispersion of fungal mycelium and penetration of hyphae (Khanet al.,2017)。pretr微生物和性质的性质eatment is the important factor of degradation. According to the Griffin 1980, growth of fungi cause cracking, bursting and swelling of plastic as fungi penetrate on the polymer.
Conclusion
PP plastic is mostly used for packaging of material possibly separating the product from the external environment. From the above-mentioned results and discussion we can assess that:
The film with aluminium metallization has excellent barrier properties than non-metalized.
得出的结论是,使用聚丙烯薄膜with aluminium coating for the better shelf life of food products.
It is also concluded that specified grades of polypropylene and additives have also some impact on the properties of the film. Therefore it is better to use mentioned polypropylene grades and additives.
From an environmental point of view, they are persistent in nature and not easily biodegradable. Therefore, in this era of innovation technology design material should be manufacture as must be resistant during their use and must biodegrade at the end of their useful life.
Acknowledgements
The author would like to express their gratitude to thePakistan Council of Scientific and Industrial Research, Karachi, Pakistan
References
- F. Tihminlioglu, I. Atik, B. Ozen, WVTR and OTR Value for Polypropylene Film”.EC Nutrition5.2 (2016): 10891099,Journal of Food Engineering, 96, 342.
- Yahya Ibrahim Mohamed Khalifa. “Effect of the Printing Remedies and Lamination Techniques on Barrier Properties. (2010)Journal of NutritionVol 2,
- Sidwell, J. AFood Contact Polymeric Materials. Vol. 6, No. 1. Report 61。(1992). Rapra Technology, England.
- Lange, J. and Wyser, Recent innovations in barrier technologies for plastic packaging: A review. (2003).Packaging Technology and Science。16:149 - 158。
CrossRef - Robertson, G.L. (2006).Food Packaging: Principles and Practice。CRC Press, Boca Raton, FL.
- Mokwenak. k., tang j. Ethylene Vinyl Alcohol: A Review of Barrier properties for Packaging Shelf Stable Foods (2010),Journal of food, vol 1.
- Opara U. L. and Asanda M. A review on the role of packaging in securing food system: Adding value to food products and reducing losses and waste. (2013).African Journal of Agricultural ResearchVol. 8(22), pp. 2621-2630: 13 June 2013.
- Kanishka Bhunia, Shyam S. Sablani, Juming Tang, and Barbara Rasco, Migration of Chemical Compounds from Packaging Polymers during Microwave, Conventional Heat Treatment, and Storage, Vol.12,2013, pp 524-545. _ ComprehensiveReviewsinFoodScienceandFoodSafety
CrossRef - Yamada-Onodera K, Mukumoto H, Katsuyaya Y, Saiganji A, Tani Y. Degradation of polyethene by a fungus, Penicilliumsimplicissimum YK. Polym Degrad Stab 2003;72(3):441e52
- Kensuke Miyazaki a, Takayuki Arai a, Kazuto Shibata a, Minoru Terano b, Hisayuki Nakatani, Study on biodegradation mechanism of novel oxo-biodegradable polypropylenes in an aqueous medium, Polymer Degradation and Stability 97 (2012) 2177e2184
CrossRef - Singh B, Sharma N, Mechanistic implications of plastic degradation, Polymer Degradation and Stability(2007)Polymer Degradation and Stability, 93, 561-584
CrossRef - Deepika S and Jaya Madhuri R, Biodegradation of low-density polyethene by microorganisms from garbage soil,(2015) Journal of Experimental Biology and Agricultural Sciences, Vol .3(1)16-21
- Khan.S, Nadir.S, Zia ullah shah, Shah .AA, Karunarathna S.C, Xu .J, Khan A, muniar S and Hasan .F (2017) Biodegradation of polyester polyurethane by Aspergillustubingenis, Environmnetal pollution 1-12
CrossRef - Raaman N., N. Rajitha, A. Jayshree and R. Jegadeesh, Biodegradation of plastic by Aspergillus spp. isolated from polythene polluted sites around Chennai,(2012) J. Acad. Indus. Res. Vol. 1(6)
- ASTM D3985-05(2010)e1: Standard Test Method for Oxygen Gas Transmission Rate Through Plastic Film and Sheeting Using a Coulometric Sensor, ASTM International, West Conshohocken, PA, (2010).
- Mincer TJ, Zettler ER, Amaral-Zettler LA (2016) Biofilms on plastic debris and their influence on marine nutrient cycling, productivity, and hazardous chemical mobility. In: Takada H, Karapanagioti HK (eds) Hazardous chemicals associated with plastics in the marine environment, The handbook of environmental chemistry. Springer. doi:10.1007/698_2016_12
CrossRef - Krupp RL, Jewell JW (1992) Biodegradability of modified plastic films in controlled biological environments。Environ Sci Tech26:193–198
CrossRef - Sudhakar M, Doble M, Sriyutha Murthy P, Venkatesan R (2008) Marine microbe-mediated biodegradation of low- and high-density polyethene.Int Biodeter Biodegr61:203–213
CrossRef - Pramila.R and Ramesh K.V (2011) Biodegradation of low-density Polyethylene (LDPE) by fungi isolated from marine water- A SEM analysis.Journal of Microbial researchVol 5(28),5013-5018
CrossRef - Manuela Lamberti& Felix Escher (2007) Aluminium Foil as a Food Packaging Material in Comparison with Other Materials, Food Reviews International, 23:4, 407-433, DOI: 10.1080/87559120701593830
CrossRef - Khan S, Nadir S, Shah ZU, Shah AA, Karunarathna SC, Xu J, Khan A, Munir S, Hasan F ( 2017) Biodegradation of polyester polyurethane by Aspergillustubingensis. Environ Pollut.,1-12
CrossRef - Griffin G.J.L.(1980)Synthetic polymers and the living environment, PureAppl Chem, 52, pp. 399-407.
CrossRef - López-de-Dicastillo, C., Gómez-Estaca, J., Catalá, R., Gavara, R., Hernández-Muñoz, P.(2012).Active antioxidant packaging ï¬lms: Development and effect on lipid stability of brined sardines.Food Chemistry,131: 1376–1384.
CrossRef