Poly Vinyl Alcohol is being an environmental friendly and having very good mechanical properties, the hydrophilic property of it makes it un-usable for packaging industry as an alternative to environmental hazardous petro chemical based polymers. To increase its water resistant property an indigenous shock wave treatment is tested and it is found that the hydrophilic property reduces significantly. The Poly Vinyl Alcohol films of around 0.25 mm thickness is bombarded with 0, 50, 100 and 150 shock wave impulses, with time gap of around 15 seconds of having Mach number around 1.7 to 1.8. The shock waves are produced with the help of a shock tube which can produce shockwaves with Mach number upto 2. The water resistant property is studied by film dissolve time method and by contact angle measurement. The morphological changes due to shock loading is studied by UV-VIS, EDAX, FTIR methods and the SEM images confirm the structural changes. The reduction in hydrophilic property promises the future of PVA films as biodegradable packaging material

Raju, S.P.

Sosmashekharappa, H.M.

Thirumalesh

Electronic Sumy State University Institutional Repository

JOURNAL OF NANO- AND ELECTRONIC PHYSICS ЖУРНАЛ НАНО- ТА ЕЛЕКТРОННОЇ ФІЗИКИ Vol. 12 No 2, 02034(4pp) (2020) Том 12 № 2, 02034(4cc) (2020)   2077-6772/2020/12(2)02034(4) 02034-1  2020 Sumy State University Shock Wave Treated PVA Films as Alternative Bio Degradable Polymer  for Packaging Industry  Thirumalesh1,3,*, S.P. Raju4, H.M. Sosmashekharappa2,†  1 Department of Studies in Physics, Mangalore University, Mangalagangotri – 574 199, Karnataka, India 2 Center for Application of Radioisotopes and Radiation Technology (CARRT), Mangalore University,  Mangalagangotri – 574 199, Karnataka, India 3 Departement of Physics, R L Jalappa Institute of Technology, Doddaballapur – 561203, Karnataka, India 4Departement of Physics, Malnad College of Engineering, Hassan – 573202, Karnataka, India  (Received 15 February 2020; revised manuscript received 13 April 2020; published online 25 April 2020)  Poly Vinyl Alcohol is being an environmental friendly and having very good mechanical properties, the hydrophilic property of it makes it un-usable for packaging industry as an alternative to environmental hazardous petro chemical based polymers. To increase its water resistant property an indigenous shock wave treatment is tested and it is found that the hydrophilic property reduces significantly. The Poly Vinyl Alcohol films of around 0.25 mm thickness is bombarded with 0, 50, 100 and 150 shock wave impulses, with time gap of around 15 seconds of having Mach number around 1.7 to 1.8. The shock waves are pro-duced with the help of a shock tube which can produce shockwaves with Mach number upto 2. The water resistant property is studied by film dissolve time method and by contact angle measurement. The morpho-logical changes due to shock loading is studied by UV-VIS, EDAX, FTIR methods and the SEM images con-firm the structural changes. The reduction in hydrophilic property promises the future of PVA films as bi-odegradable packaging material.  Keywords: Shock waves, Shock wave interactions, Poly Vinyl Alcohol, PVA.  DOI: 10.21272/jnep.12(2).02034 PACS numbers: 78.90.t, 79.60.Fr                                                                   * thirumalesh.dbp@gmail.com †  carrtmu@gmail.com 1. INTRODUCTION  Shock waves [1] and blast waves are a sort of wave that carries the disruption created by sudden bursting in any medium. The immediate effect of shock waves results in an abrupt increase in pressure, enthalpy and temperature on the surface of the medium on which the wave front of the shockwave impacts [2]. Shock tubes or shock tunnels are used in production of shockwaves in the laboratory in a controlled way [3-6]. In general, a shock tube will consist of two parts. Namely, a driver section(pre-shock side), a driven section(post-shock side), and a thin diaphragm separates the two regions. The pressure in the driver section is increased with the help of a pump by compressing the driving medium. Therefore, the diaphragm breaks down and produces a shockwave in the downstream of driven section. The velocity of the shockwave generated will be more than the velocity of sound in that medium. This supersonic velocity is measured in a unit called Mach number. Mach number is the unit of speed defined as the ratio of object velocity in a medium to the ambient sound velocity. So, Mach-1 corresponds to, the sound velocity in a medium and more reflects multiples of the sound velocity. Appropriate sensors are mounted on the shock tube to assess the shockwave movement and to meas-ure strength of rupture pressure which creates the wave. The present work focuses primarily on the treatment of Poly vinyl alcohol (PVA) films by shock-wave in pursuit of increase in the hydrophobic nature.  Poly vinyl alcohol (PVA) is a bio-degradable and wa-ter-soluble polymer, in which the hydroxyl(OH) groups hooked up to carbon atoms of methane groups on car-bon chain backbone. Such hydroxyl groups forms the origin of bonding between hydrogen atoms and thus responsible for polymer formation[7]. PVA’s impressive chemical and physical properties are water-soluble, non-toxic, environmental friendly, good mechanical strength and strong dielectric strength etc. Also, these properties can be further enhanced or tuned by adding compatible dopants [8-11] and we can find good number of attempts in modifying PVA properties with irradia-tion methods [12-15]. Consequently, PVA has numer-ous applications in various fields. In pursuit of changes in chemical and physical properties, the analysis dis-cussed here is another approach used for processing PVA. The electrical property changes of PVA films due to shockwave impacts is studied and published else-where [16].  2. EXPERIMENTAL TECHNIQUES  2.1 PVA Films Preparation  PVA in semi crystalline powder form of 99.9% pure was obtained from SD Fine Chemicals Ltd., Mumbai, India. 4wt% PVA solution is prepared in 60 °C hot distilled water with continuous stirring for about 5-6 hours. The prepared PVA solution is distributed to 2inch diameter petri dishes and is dried under hot air oven at 50 °C for about 24-30 Hrs to get thin films of PVA samples.  2.2 Shock Tube Setup  The shock tube used for this study is designed and  THIRUMALESH, S.P. RAJU, H.M. SOMASHEKHARAPPA J. NANO- ELECTRON. PHYS. 12, 02034 (2020)   02034-2 developed in-house. This is a low pressure manually operated shock-tube type, and has the ability to generate shockwaves of Mach number upto 2. The actual photo-graph of the shock tube used is given in Fig. 1. The method of construction of the shock tube, its working, calibration and results obtained are discussed in detail and submitted for publication in a reputed journal [6]. The shock tube specifications are as follows. The driving section of the tube is around 400 mm long and the driven section is 500 mm long. The inner and outer diameter of the tube is 20mm and 38 mm respectively. The material of the tube is 316 grade stainless steel. The driving and driven sections of the tube are sepa-rated by a diaphragm which is placed in an arrange-ment having a handle to join and separate the two sections. The diaphragm can be replaced every time in this arrangement easily.     Fig. 1 – Actual photograph of the shock tube setup used in this study  2.3 Shock Wave Treatment  The petri dishes containing the PVA films are placed inside the sample holder attached to the open end of the driven section of the shock tube with a gap of around 10mm between the sample and the shock tube. A leg pump used to inflate the tires of vehicles is used to create a pressure in the driving section. A paper diaphragm of thickness 90GSM can produce shock-waves around 1.7 to 1.8 Mach numbers. The Mach number of the shock wave generated can be found by measuring the time delay between the signals plotted on the computer screen by a ‘shock tube data analyzer’ software specifically developed for this device and by knowing the distance between the sensors. This process is repeated to generate shock waves continuously by replacing the diaphragms. The time interval between the successive shockwave impacts is maintained as not more than 15 seconds. The PVA samples were bombard-ed with 0, 25, 50, 100 and 150 shock waves impacts.  2.4 Characterization  The PVA samples which are exposed to shock waves are characterized for physical and chemical property changes. The Fourier Transform Infrared Spectropho-tometer (FTIR) method was used to know the chemical composition changes over a wave number range of 4000-1500 cm  1. For optical characterization of the PVA samples, the Ultraviolet-Visible (UV-Viz) absorp-tion spectrometer analysis was carried out in the wave-length range of 200-500 nm. To know the surface mor-phology of the samples, FESEM - Field Emission Scan-ning Electron Microscopic method was used. The EDAX studies were conducted to identify the PVA sam-ples elemental composition. The contact angle meas-urement was done to study the hydrophilic nature of the samples and an indigenous test was carried out to quantify the water solubility nature for the use of PVA as a packaging material.  3. RESULTS AND DISCUSSION  3.1 UV-Vis Absorption Spectrum Studies  From the UV-Vis spectral analysis (Fig. 2), it is ob-served that, the wavelength corresponding to the max-imum absorption shifting towards longer wavelength side as the number of shock waves impact increases from zero to 150 numbers. This could be observed in the careful study of the readings corresponding to the spectrum in the marked region. This clearly exhibit as the higher delocalization in electron confinements of the PVA samples in response to shockwaves. This ten-dency is checked by examining the wavelengths refer-ring to the maximum absorbance value for different curves. This reorganization of PVA molecules increases the delocalization of polymer bonds due to the shock waves. The improvement in delocalization decreases the energy difference between the occupied uppermost molecular orbital and the unoccupied lowermost anti-bonding orbital [17].    Fig. 2 – UV – Vis spectra of shock treated and untreated PVA samples  Therefore, the energy required to jump between these levels becomes less and thus the wavelength of absorption becomes longer. Therefore, the absorption shift to longer wavelengths as the delocalisation in the PVA molecules rises.   3.2 FTIR Studies   Changes in the main peaks of FTIR spectra (Fig. 3), suggest the effective changes in PVA functional groups by shockwaves.  In the FTIR spectra it is observed that, the peak corresponding to the O-H group situated at 3300 cm-1 is reduced after shockwave treatment when compared with the pure samples. The decrease in Hy-drogen bonding signifies that, the molecules of PVA becoming less polar [17]. This implies that, the solubili-ty of these molecules becomes less in a polar solvent like water.   SHOCKWAVE TREATED PVA FILMS AS ALTERNATIVE… J. NANO- ELECTRON. PHYS. 12, 02034 (2020)   02034-3   Fig. 3  FTIR spectra of shock wave treated PVA films  This directly supports the claim of less water solu-bility of PVA films after treating with shockwaves. Decrease in the width of important Corban related peaks present at 2900 and 1700 for C-H asymmetric stretching and CO stretching respectively on compari-son with treated and untreated samples clearly con-firms the carbonization of the samples due to shock-waves effect.  3.3 FESEM and EDAX Studies  SEM images (Fig. 4) for treated samples (B & D) comparing with untreated sample (A) clearly show that the surface of them is sensitive towards shock waves.  EDAX spectra given in the same Figure corresponding to A, B & C clearly shows the modification in the sam-ples surface chemistry with respect to the variation in the elemental composition. Shockwaves interaction with PVA breaks the long polymers molecules and contributes towards the cross-link between them. Such break-up and cross-linking of molecules results in an improvement in carbon content per unit volume. The increase in the carbon concentra-tion peak for the shockwave treated samples in the EDAX spectra is a strong evidence of this observation.    Fig. 4  SEM images and EDAX spectra of untreated and shock-wave treated samples  3.4 Water Solubility Test  An indigenous technique was used to test the ob-servation received with the FTIR and UV-Vis spectral studies about the hydrophobic or less water solubility of PVA after shock wave treatment. The test was per-formed for PVA samples of 0.4 mm thick films of same number of shock wave treatments.  The sample films were folded to conical shape and placed in a glass fun-nel which is kept on a conical flask (Fig. 5).  A stop clock was turned ON when 1ml of water is poured into it. The time taken for the water to drop into the conical flask after dissolving through the PVA films was rec-orded.  As to support the expectation, the time taken by the water drop to dissolve through the shock wave treated sample was more compared to untreated PVA sample. The test was repeated with the same number of shocks for two more samples and the similar results    Fig. 5 – Water solubility test for PVA films  were found. The average water dissolve time recorded is given in Table 1. Thus, the tabulated values support-ed the claim that, the PVA samples were become less water soluble after shock-waves treatment.    THIRUMALESH, S.P. RAJU, H.M. SOMASHEKHARAPPA J. NANO- ELECTRON. PHYS. 12, 02034 (2020)   02034-4 Table 1 – Water solubility test values for various shock treat-ed PVA films  Number of Shock treatment Time taken by 1 ml water to dissolve through PVA films in seconds  0 (pristine PVA) 102 50 shocks 537 100 shocks 483 150 shocks 499  3.5 Contact Angle Measurement  Contact angle of water for pristine PVA and shock treated PVA samples were measured in order to inves-tigate the hydrophilic or hydrophobic nature of the surfaces of the materials. The material wettability is known to be high for low water contact angles ( 90°) and low wettability for high contact angles ( 90°) [11, 18]. Low water contact angles, in other words, may mean higher hydrophilic nature and high contact an-gles may mean higher hydrophobic nature of material surfaces.  In good agreement with the previous results, the neat PVA had a very low water contact angle of 24.8° [11]. Whereas, there is a remarkable increased water contact angle for the shock treated PVA films. The hydrophilic level of shock treated films was slightly modified as the number of shock wave impacts increas-es, as shown in Table 2. The contact angle measure-ment photographs for untreated samples and shock wave treated samples are given in Fig. 6.  Table 2 – Water contact angle values for various shock treat-ed PVA films  Number of Shock treatment Water contact angle 0 (pristine PVA) 24.8 50 shocks 110.5 100 shocks 95.4 150 shocks 100.7       Fig. 6 – Contact angle measurement photographs of the un-treated and shock treated PVA films  4. CONCLUSIONS  It is evidenced from the above studies that an in-crease in water contact angle by 85° and large increase in the water solubility time, in comparison with that of pure PVA films. Thus, the shock treated samples shift-ed from hydrophilic nature to the hydrophobic. This improvement for PVA films could be associated with the decreased hydroxyl groups in the PVA and increase in carbon content as evidenced by FTIR and EDAX studies. This remarkable shift from hydrophilic to hy-drophobic nature of shock treated PVA films promises the future of PVA for the biodegradable environmental friendly polymer as packaging material.  ACKNOWLEDGEMENT  Authors are very much grateful to SLN EduTech – Manufacturer of educational instruments and software, Bangalore, India, for their technical support in shock tube construction. Also, thankful to the coordinator, DST-PURSE for providing FESEM and other facilities and Center for Nano and Soft matter Science (CeNS) Bangalore, for providing contact angle measurement facility. REFERENCES  1. W. Payman, W.C.F. Shepperd, Proc. Roy. Soc. A186, 293 (1946). 2. C.S. Kumar, K. Takayama, K.P.J. Reddy, Shock waves made simple (Wiley India: 2014). 3. R.J. Stalker, AIAA Journal 5 No 12, 2160 (1967). 4. R. Morgan, Free piston driven expansion tubes: A Hand-book of Shock waves, 603 (Ed. G. Ben-Dor) (Academic Press: New York: 2001).  5. K.P.J. Reddy, N. Sharath, Curr. Sci. 104 No 2, 172 (2013)  6. Thirumalesh, S.P. Raju, K Swaroop, H.M. So-mashekharappa, Engg. Reports (2020). 7. B.P. Balaji, M.V. Madhu, A.K. Sharma, V.V. Rao, Ionics 13, 441 (2007). 8. M. Abdul-Aziz, Physica B: Condens. Matter. 406 No 6-7, 1300 (2011). 9. K.G. Vijaya, R. Chandramani, J. Appl. Sci. Res. 4 No 11, 1603 (2008). 10. R.F. Bhajantri, V. Ravindrachary, A. Harisha, Vin-cent Crasta, Suresh P. Nayak, Boja Poojary, Polymer 47, 3591 (2006). 11. Z.W. Abdullah, Y. Dong, Front. Mater. 6, 58 (2019). 12. A. Harisha, V. Ravindrachary, R.F. Bhajantri, Ismayil, Ganesh Sanjeev, Boja Poojary, Dhanadeep Dutta, P.K. Pujarid, Polym. Degrad. Stabil. 93, 1554 (2008). 13. T. Sheelaa, R.F. Bhajantria, V. Ravindrachary, S.G. Rathod, P.K. Pujari, B. Poojary, R. Somashekard, Radiat. Phys. Chem. 103, 45 (2014). 14. Shreedatta H, Ravindrachary V, Praveena SD, Gu-ruswamy B, Sagar RN, Sanjeev G, AIP Conf. Proc. 1942, 110043 (2018). 15. B.K. Mahantesha, V. Ravindrachary, R. Padmakumari et al, J. Phys: Conf. Ser. 1172, 012030 (2019). 16. Thirumalesh, S.P. Raju, Swaroop K., H.M. So-mashekharappa, Mater. Res. Express 7, 015344 (2020). 17. W. Kemp, Organic Spectroscopy (Palgrave: London: 1991). 18. S G Deshmukh, V. Kheraj, K.J. Karande, A.K. Panchal, R.S. Deshmukh, Mater. Res. Express 6, 084013 (2019). 

Shock Wave Treated PVA Films as Alternative Bio Degradable Polymer for Packaging Industry

SocioEconomic Challenges Journal (Sumy State University)

JOURNAL OF NANO- AND ELECTRONIC PHYSICS ЖУРНАЛ НАНО- ТА ЕЛЕКТРОННОЇ ФІЗИКИ 
Vol. 12 No 2, 02034(4pp) (2020) Том 12 № 2, 02034(4cc) (2020) 
 
 
2077-6772/2020/12(2)02034(4) 02034-1  2020 Sumy State University 
Shock Wave Treated PVA Films as Alternative Bio Degradable Polymer  
for Packaging Industry 
 
Thirumalesh1,3,*, S.P. Raju4, H.M. Sosmashekharappa2,† 
 
1 Department of Studies in Physics, Mangalore University, Mangalagangotri – 574 199, Karnataka, India 
2 Center for Application of Radioisotopes and Radiation Technology (CARRT), Mangalore University,  
Mangalagangotri – 574 199, Karnataka, India 
3 Departement of Physics, R L Jalappa Institute of Technology, Doddaballapur – 561203, Karnataka, India 
4Departement of Physics, Malnad College of Engineering, Hassan – 573202, Karnataka, India 
 
(Received 15 February 2020; revised manuscript received 13 April 2020; published online 25 April 2020) 
 
Poly Vinyl Alcohol is being an environmental friendly and having very good mechanical properties, the 
hydrophilic property of it makes it un-usable for packaging industry as an alternative to environmental 
hazardous petro chemical based polymers. To increase its water resistant property an indigenous shock 
wave treatment is tested and it is found that the hydrophilic property reduces significantly. The Poly Vinyl 
Alcohol films of around 0.25 mm thickness is bombarded with 0, 50, 100 and 150 shock wave impulses, 
with time gap of around 15 seconds of having Mach number around 1.7 to 1.8. The shock waves are pro-
duced with the help of a shock tube which can produce shockwaves with Mach number upto 2. The water 
resistant property is studied by film dissolve time method and by contact angle measurement. The morpho-
logical changes due to shock loading is studied by UV-VIS, EDAX, FTIR methods and the SEM images con-
firm the structural changes. The reduction in hydrophilic property promises the future of PVA films as bi-
odegradable packaging material. 
 
Keywords: Shock waves, Shock wave interactions, Poly Vinyl Alcohol, PVA. 
 
DOI: 10.21272/jnep.12(2).02034 PACS numbers: 78.90.t, 79.60.Fr 
 
 
                                                                
* thirumalesh.dbp@gmail.com 
†  carrtmu@gmail.com 
1. INTRODUCTION 
 
Shock waves [1] and blast waves are a sort of wave 
that carries the disruption created by sudden bursting 
in any medium. The immediate effect of shock waves 
results in an abrupt increase in pressure, enthalpy and 
temperature on the surface of the medium on which the 
wave front of the shockwave impacts [2]. Shock tubes 
or shock tunnels are used in production of shockwaves 
in the laboratory in a controlled way [3-6]. In general, a 
shock tube will consist of two parts. Namely, a driver 
section(pre-shock side), a driven section(post-shock 
side), and a thin diaphragm separates the two regions. 
The pressure in the driver section is increased with the 
help of a pump by compressing the driving medium. 
Therefore, the diaphragm breaks down and produces a 
shockwave in the downstream of driven section. The 
velocity of the shockwave generated will be more than 
the velocity of sound in that medium. This supersonic 
velocity is measured in a unit called Mach number. 
Mach number is the unit of speed defined as the ratio 
of object velocity in a medium to the ambient sound 
velocity. So, Mach-1 corresponds to, the sound velocity 
in a medium and more reflects multiples of the sound 
velocity. Appropriate sensors are mounted on the shock 
tube to assess the shockwave movement and to meas-
ure strength of rupture pressure which creates the 
wave. The present work focuses primarily on the 
treatment of Poly vinyl alcohol (PVA) films by shock-
wave in pursuit of increase in the hydrophobic nature.  
Poly vinyl alcohol (PVA) is a bio-degradable and wa-
ter-soluble polymer, in which the hydroxyl(OH) groups 
hooked up to carbon atoms of methane groups on car-
bon chain backbone. Such hydroxyl groups forms the 
origin of bonding between hydrogen atoms and thus 
responsible for polymer formation[7]. PVA’s impressive 
chemical and physical properties are water-soluble, 
non-toxic, environmental friendly, good mechanical 
strength and strong dielectric strength etc. Also, these 
properties can be further enhanced or tuned by adding 
compatible dopants [8-11] and we can find good number 
of attempts in modifying PVA properties with irradia-
tion methods [12-15]. Consequently, PVA has numer-
ous applications in various fields. In pursuit of changes 
in chemical and physical properties, the analysis dis-
cussed here is another approach used for processing 
PVA. The electrical property changes of PVA films due 
to shockwave impacts is studied and published else-
where [16]. 
 
2. EXPERIMENTAL TECHNIQUES 
 
2.1 PVA Films Preparation 
 
PVA in semi crystalline powder form of 99.9% pure 
was obtained from SD Fine Chemicals Ltd., Mumbai, 
India. 4wt% PVA solution is prepared in 60 °C hot 
distilled water with continuous stirring for about 5-6 
hours. The prepared PVA solution is distributed to 
2inch diameter petri dishes and is dried under hot air 
oven at 50 °C for about 24-30 Hrs to get thin films of 
PVA samples. 
 
2.2 Shock Tube Setup 
 
The shock tube used for this study is designed and 
 THIRUMALESH, S.P. RAJU, H.M. SOMASHEKHARAPPA J. NANO- ELECTRON. PHYS. 12, 02034 (2020) 
 
 
02034-2 
developed in-house. This is a low pressure manually 
operated shock-tube type, and has the ability to generate 
shockwaves of Mach number upto 2. The actual photo-
graph of the shock tube used is given in Fig. 1. The 
method of construction of the shock tube, its working, 
calibration and results obtained are discussed in detail 
and submitted for publication in a reputed journal [6]. 
The shock tube specifications are as follows. The 
driving section of the tube is around 400 mm long and 
the driven section is 500 mm long. The inner and outer 
diameter of the tube is 20mm and 38 mm respectively. 
The material of the tube is 316 grade stainless steel. 
The driving and driven sections of the tube are sepa-
rated by a diaphragm which is placed in an arrange-
ment having a handle to join and separate the two 
sections. The diaphragm can be replaced every time in 
this arrangement easily.  
 
 
 
Fig. 1 – Actual photograph of the shock tube setup used in 
this study 
 
2.3 Shock Wave Treatment 
 
The petri dishes containing the PVA films are 
placed inside the sample holder attached to the open 
end of the driven section of the shock tube with a gap of 
around 10mm between the sample and the shock tube. 
A leg pump used to inflate the tires of vehicles is used 
to create a pressure in the driving section. A paper 
diaphragm of thickness 90GSM can produce shock-
waves around 1.7 to 1.8 Mach numbers. The Mach 
number of the shock wave generated can be found by 
measuring the time delay between the signals plotted 
on the computer screen by a ‘shock tube data analyzer’ 
software specifically developed for this device and by 
knowing the distance between the sensors. This process 
is repeated to generate shock waves continuously by 
replacing the diaphragms. The time interval between 
the successive shockwave impacts is maintained as not 
more than 15 seconds. The PVA samples were bombard-
ed with 0, 25, 50, 100 and 150 shock waves impacts. 
 
2.4 Characterization 
 
The PVA samples which are exposed to shock waves 
are characterized for physical and chemical property 
changes. The Fourier Transform Infrared Spectropho-
tometer (FTIR) method was used to know the chemical 
composition changes over a wave number range of 
4000-1500 cm  1. For optical characterization of the 
PVA samples, the Ultraviolet-Visible (UV-Viz) absorp-
tion spectrometer analysis was carried out in the wave-
length range of 200-500 nm. To know the surface mor-
phology of the samples, FESEM - Field Emission Scan-
ning Electron Microscopic method was used. The EDAX 
studies were conducted to identify the PVA sam-
ples elemental composition. The contact angle meas-
urement was done to study the hydrophilic nature of 
the samples and an indigenous test was carried out to 
quantify the water solubility nature for the use of PVA 
as a packaging material. 
 
3. RESULTS AND DISCUSSION 
 
3.1 UV-Vis Absorption Spectrum Studies 
 
From the UV-Vis spectral analysis (Fig. 2), it is ob-
served that, the wavelength corresponding to the max-
imum absorption shifting towards longer wavelength 
side as the number of shock waves impact increases 
from zero to 150 numbers. This could be observed in 
the careful study of the readings corresponding to the 
spectrum in the marked region. This clearly exhibit as 
the higher delocalization in electron confinements of 
the PVA samples in response to shockwaves. This ten-
dency is checked by examining the wavelengths refer-
ring to the maximum absorbance value for different 
curves. This reorganization of PVA molecules increases 
the delocalization of polymer bonds due to the shock 
waves. The improvement in delocalization decreases 
the energy difference between the occupied uppermost 
molecular orbital and the unoccupied lowermost anti-
bonding orbital [17]. 
 
 
 
Fig. 2 – UV – Vis spectra of shock treated and untreated PVA 
samples 
 
Therefore, the energy required to jump between 
these levels becomes less and thus the wavelength of 
absorption becomes longer. Therefore, the absorption 
shift to longer wavelengths as the delocalisation in the 
PVA molecules rises.  
 
3.2 FTIR Studies  
 
Changes in the main peaks of FTIR spectra (Fig. 3), 
suggest the effective changes in PVA functional groups 
by shockwaves.  In the FTIR spectra it is observed that, 
the peak corresponding to the O-H group situated at 
3300 cm-1 is reduced after shockwave treatment when 
compared with the pure samples. The decrease in Hy-
drogen bonding signifies that, the molecules of PVA 
becoming less polar [17]. This implies that, the solubili-
ty of these molecules becomes less in a polar solvent 
like water. 
 
 SHOCKWAVE TREATED PVA FILMS AS ALTERNATIVE… J. NANO- ELECTRON. PHYS. 12, 02034 (2020) 
 
 
02034-3 
 
 
Fig. 3  FTIR spectra of shock wave treated PVA films 
 
This directly supports the claim of less water solu-
bility of PVA films after treating with shockwaves. 
Decrease in the width of important Corban related 
peaks present at 2900 and 1700 for C-H asymmetric 
stretching and CO stretching respectively on compari-
son with treated and untreated samples clearly con-
firms the carbonization of the samples due to shock-
waves effect. 
 
3.3 FESEM and EDAX Studies 
 
SEM images (Fig. 4) for treated samples (B & D) 
comparing with untreated sample (A) clearly show that 
the surface of them is sensitive towards shock waves.  
EDAX spectra given in the same Figure corresponding 
to A, B & C clearly shows the modification in the sam-
ples surface chemistry with respect to the variation in 
the elemental composition. 
Shockwaves interaction with PVA breaks the long 
polymers molecules and contributes towards the cross-
link between them. Such break-up and cross-linking of 
molecules results in an improvement in carbon content 
per unit volume. The increase in the carbon concentra-
tion peak for the shockwave treated samples in the 
EDAX spectra is a strong evidence of this observation. 
 
 
 
Fig. 4  SEM images and EDAX spectra of untreated and shock-wave treated samples 
 
3.4 Water Solubility Test 
 
An indigenous technique was used to test the ob-
servation received with the FTIR and UV-Vis spectral 
studies about the hydrophobic or less water solubility 
of PVA after shock wave treatment. The test was per-
formed for PVA samples of 0.4 mm thick films of same 
number of shock wave treatments.  The sample films 
were folded to conical shape and placed in a glass fun-
nel which is kept on a conical flask (Fig. 5).  A stop 
clock was turned ON when 1ml of water is poured into 
it. The time taken for the water to drop into the conical 
flask after dissolving through the PVA films was rec-
orded.  As to support the expectation, the time taken by 
the water drop to dissolve through the shock wave 
treated sample was more compared to untreated PVA 
sample. The test was repeated with the same number 
of shocks for two more samples and the similar results  
 
 
Fig. 5 – Water solubility test for PVA films 
 
were found. The average water dissolve time recorded 
is given in Table 1. Thus, the tabulated values support-
ed the claim that, the PVA samples were become less 
water soluble after shock-waves treatment. 
 
 
 THIRUMALESH, S.P. RAJU, H.M. SOMASHEKHARAPPA J. NANO- ELECTRON. PHYS. 12, 02034 (2020) 
 
 
02034-4 
Table 1 – Water solubility test values for various shock treat-
ed PVA films 
 
Number of 
Shock treatment 
Time taken by 1 ml water to 
dissolve through PVA films in 
seconds  
0 (pristine PVA) 102 
50 shocks 537 
100 shocks 483 
150 shocks 499 
 
3.5 Contact Angle Measurement 
 
Contact angle of water for pristine PVA and shock 
treated PVA samples were measured in order to inves-
tigate the hydrophilic or hydrophobic nature of the 
surfaces of the materials. The material wettability is 
known to be high for low water contact angles ( 90°) 
and low wettability for high contact angles ( 90°) 
[11, 18]. Low water contact angles, in other words, may 
mean higher hydrophilic nature and high contact an-
gles may mean higher hydrophobic nature of material 
surfaces.  
In good agreement with the previous results, the 
neat PVA had a very low water contact angle of 24.8° 
[11]. Whereas, there is a remarkable increased water 
contact angle for the shock treated PVA films. The 
hydrophilic level of shock treated films was slightly 
modified as the number of shock wave impacts increas-
es, as shown in Table 2. The contact angle measure-
ment photographs for untreated samples and shock 
wave treated samples are given in Fig. 6. 
 
Table 2 – Water contact angle values for various shock treat-
ed PVA films 
 
Number of Shock 
treatment 
Water contact angle 
0 (pristine PVA) 24.8 
50 shocks 110.5 
100 shocks 95.4 
150 shocks 100.7 
 
  
  
 
Fig. 6 – Contact angle measurement photographs of the un-
treated and shock treated PVA films 
 
4. CONCLUSIONS 
 
It is evidenced from the above studies that an in-
crease in water contact angle by 85° and large increase 
in the water solubility time, in comparison with that of 
pure PVA films. Thus, the shock treated samples shift-
ed from hydrophilic nature to the hydrophobic. This 
improvement for PVA films could be associated with 
the decreased hydroxyl groups in the PVA and increase 
in carbon content as evidenced by FTIR and EDAX 
studies. This remarkable shift from hydrophilic to hy-
drophobic nature of shock treated PVA films promises 
the future of PVA for the biodegradable environmental 
friendly polymer as packaging material. 
 
ACKNOWLEDGEMENT 
 
Authors are very much grateful to SLN EduTech – 
Manufacturer of educational instruments and software, 
Bangalore, India, for their technical support in shock 
tube construction. Also, thankful to the coordinator, 
DST-PURSE for providing FESEM and other facilities 
and Center for Nano and Soft matter Science (CeNS) 
Bangalore, for providing contact angle measurement 
facility.
 
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Shock Wave Treated PVA Films as Alternative Bio Degradable Polymer for Packaging Industry

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