Arab Journal of Physical Chemistry- audi … · Dina S. Ahmed,a Gamal A. El-Hiti,b Hassan Hashim,c Riyadh Noaman,d Ayad S. Hameeda Emad Yousif e a Department of Chemistry, College

Arab Journal of Physical Chemistry- http://aphyschem.org

Article/ D. S. Ahmed et al.

Arab Journal of Physical Chemistry © 2018/ISSN: 1658-6883 Arab J. Phys. Chem. 5 (2018) Page 1

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Physical and Morphological Properties of Poly(vinyl chloride) Films upon

Irradiation in the Presence of Tetra Schiff Bases as Photostabilizers

Dina S. Ahmed,a Gamal A. El-Hiti,*

b Hassan Hashim,

c Riyadh Noaman,

d Ayad S. Hameed

a

Emad Yousif *e

a Department of Chemistry, College of Science, Tikrit University, Tikrit , Iraq

b Cornea Research Chair, Department of Optometry, College of Applied Medical Sciences, King Saud University,

P.O. Box 10219, Riyadh 11433, Saudi Arabia

E-mail*: [email protected]; Tel: 00966114693778; Fax: 00966114693536 c Department of Physics, College of Science, Al-Nahrain University, Baghdad, Iraq

d Chemical and Petrochemical Research Center, Corporation of Research and Industrial Development, Ministry of

Industry and Minerals, Baghdad, Iraq e Department of Chemistry, College of Science, Al-Nahrain University, Baghdad 64021, Iraq

E-mail*: [email protected]

Received 26th

December 2017; Accepted 17th

April 2018

Novelty and Highlights:

1– Photo-degradation rate constant and surface morphology of PVC containing tetra Schiff

bases were determined.

2– Schiff bases were used to reduce PVC photo-degradation rate constant.

3– The scanning electron microscope indicates that the photo-degradation of irradiated

PVC containing Schiff bases was much less compared to the blank film.

Graphical Abstract:

http://aphyschem.org/




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Physical and Morphological Properties of Poly(vinyl chloride) Films upon

Irradiation in the Presence of Tetra Schiff Bases as Photostabilizers

Dina S. Ahmed,a Gamal A. El-Hiti,*

b Hassan Hashim,

c Riyadh Noaman,

d Ayad S. Hameed

a

Emad Yousif *e

a Department of Chemistry, College of Science, Tikrit University, Tikrit , Iraq

b Cornea Research Chair, Department of Optometry, College of Applied Medical Sciences, King Saud University, P.O.

Box 10219, Riyadh 11433, Saudi Arabia

E-mail*: [email protected]; Tel: 00966114693778; Fax: 00966114693536 c Department of Physics, College of Science, Al-Nahrain University, Baghdad, Iraq

d Chemical and Petrochemical Research Center, Corporation of Research and Industrial Development, Ministry of

Industry and Minerals, Baghdad, Iraq e Department of Chemistry, College of Science, Al-Nahrain University, Baghdad 64021, Iraq

E-mail*: [email protected]

Abstract: The photo-degradation rate constant and surface morphology of poly(vinyl chloride), upon irradiation with an

ultraviolet light were investigated in the presence of Schiff bases as photostabilizers. Poly(vinyl chloride) photo-degradation

rate constant was lower for the films containing Schiff bases (5.0–9.0 × 104

sec1

) compared to the blank film (12.6 × 103

sec1

). In addition, the surface morphology of the irradiated poly(vinyl chloride) containing Schiff bases, examined by scanning

electron microscopy, indicates that the surface was much smoother compared to the blank film.

Keywords: Schiff base; Poly(vinyl chloride) films; Photodegradation rate constant; Scanning electron microscopy

technique; photostabilizers; Ultraviolet absorbers.

Introduction

Schiff bases have various unique characteristics such as

nonlinear optical properties due to the presence of the

C=N moiety [1]. Polymeric materials containing C=N

unit within the main chain are known as

polyazomethines. Polyazomethines have a good thermal

resistance [2] and can be used as semiconductors [3],

liquid crystals [4], fibres forming [5],

electroluminescence materials [6] and biological agents

[7].

Polyvinyl chloride (PVC) is a very common plastic that

produced in huge quantities. PVC polymeric materials

are used in the production of agricultural films,

packaging materials, pipes, toys, construction materials,

slippers [8,9]. However, harsh conditions such as high

temperature and ultraviolet (UV) light can lead to photo-

degradation of PVC leading to the production of

hydrogen chloride (HCl) which is a potential

environmental hazard [10,11]. Long-term exposure to

PVC to UV light can also lead to transparency loss and

short service live [12]. Moreover, high-level exposure of

PVC to blue light could lead to loss of colour and

brittleness [13]. Therefore, many efforts have been made

to protect PVC materials against photodegradation using

various photostabilizers as additives in low

concentration [14–18] and in particular Schiff bases

[19–21].

As part of our own interest in polymeric materials [22–

28], we began investigating the physical and

morphological properties of PVC films containing tetra

Schiff bases as photostabilizers upon UV irradiation for

long period (300 h). The photo-degradation rate constant

(Kd) was calculated and the surface morphology of PVC

films was examined by the use of scanning electron

microscopy (SEM).





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Experimental

Schiff Bases 13

Schiff bases 13 (Figure 1) were prepared using a

literature procedure [21] from the reaction of biphenyl-

3,3′,4,4′-tetraamine and excess aryl aldehydes (4 mole

equivalents) and their spectral and elemental data were

consistent with the reported ones [21].

Figure 1. Tetra Schiff bases 1‒3.

Films Preparation and Light Exposure

A well-stirred mixture of PVC and tetrahydrofuran

(THF; 1:20 by weight) was cast onto glass plates and

dried at 25 C (24 h) under reduced pressure. PVC films

(40 µm thickness) containing 1‒3 (0.5% by weight)

were similarly produced. The thickness of the films was

measured using a Digital Caliper Vernier (Kevelaer,

Germany). The films were irradiated using UV light

(290–360 nm; max = 313 nm) for 300 h and QUV tester

(Philips, Saarbrücken, Germany) was used for the

measurements.

Photodegradation Rate Constant (kd) of PVC Films

A Shimadzu Spectrophotometer (Shimadzu, Kyoto,

Japan) was used to detect the changes in PVC films

during irradiation. Equation 3, derived from Equations 1

and 2, was used to calculate PVC photodecomposition

rate constant (kd).

𝑙𝑛(𝑎 − 𝑥) = 𝑙𝑛𝑎 − 𝑘𝑑 𝑡 (1)

𝑎 − 𝑥 = 𝐴0 − 𝐴∞ − 𝐴0 + 𝐴𝑡 = 𝐴𝑡 − 𝐴 (2)

𝑙𝑛(𝐴𝑡 − 𝐴∞) = 𝑙𝑛(𝐴0 − 𝐴) − 𝑘𝑑 𝑡 (3)

where, 𝑥 = 𝐴0 − 𝐴𝑡, a = PVC concentration before

irradiation, x = change in PVC concentration at time t

during irradiation, A0 = the absorption intensity of the

PVC at t0, A∞ = the absorption intensity at t and At = the

absorption intensity after irradiation time t. The plot of

𝑙𝑛(𝐴𝑡 − 𝐴∞) versus t gives straight a line with a slope

equal kd. The photodecomposition of PVC follows a first

order kinetics [29].

Surface Morphology of PVC Films

The surface roughness and morphology of PVC films

upon irradiation (300 h) were examined using Inspect

S50 microscope (FEI Company, Czech Republic) in

which accelerating voltage was 15 kV.

Results and discussion

Photodegradation Rate (kd) of PVC Films using UV

Spectrophotometer

The PVC films containing 1–3 (0.5% by weight) were

irradiated with a UV light (λmax = 313 nm) for up to 300

h. A change in colour takes place on irradiation which is

an indication of PVC photodecomposition. The plot of

𝑙𝑛(𝐴𝑡 − 𝐴∞) against irradiation time (t) shows a first

order kinetics. The plot gives a straight line with a slope

that is equal to the PVC decomposition rate constant

(kd). Figures 25 show the change observed in 𝑙𝑛(𝐴𝑡 −𝐴∞) against irradiation time (t) for PVC films in the

absence and presence of additives. The kd was calculated

in each case and reported in Table 1.

It was clear from Figures 2–5 and Table 1 that kd is

sensitive to the presence of Schiff bases 1–3. The PVC

photodecomposition rate constant was highest (12.6 ×

103

sec1

) for PVC (blank) and much lower for PVC

containing Schiff bases. The efficiency of photo-

stabilizers follows the order of 1 2 3.

Table 1 kd for PVC films on UV irradiation (300 h).

PVC film Kd (sec‒1

)

PVC (control) 12.6 × 10‒3

PVC + 1 5.0 × 10‒4

PVC + 2 8.0 × 10‒4

PVC + 3 9.0 × 10‒4

Schiff base 1 was the most efficient photostabilizer in

which kd was lowest (5.0 × 104

sec1

). Schiff base 1

acted as a better PVC photo-stabilizer, compared to

other additives via a proton transfer and intersystem

conversion due to the presence of hydroxyl group at the

ortho-position of the aryl moieties [30,31].





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Figure 2. Changes in 𝑙𝑛(𝐴𝑡 − 𝐴∞) versus irradiation time for

PVC (blank).

Figure 3. The change of 𝑙𝑛(𝐴𝑡 − 𝐴∞) versus irradiation time

for PVC + 1.

Surface Morphology of PVC by SEM

Long-term irradiation of PVC films always leads to roughness,

irregularity and defects within the surface [21,32,33]. To study

the effect of additives on the surface morphology of PVC upon

irradiation, the PVC films were irradiated and the surface

morphology was inspected using SEM. The SEM images for

PVC (blank) and those contain Schiff bases 1–3 after

irradiation are shown in Figures 6–9.

Figure 6‒9 show cracks and roughness within the PVC films

after irradiation. The cracks, nodes and roughness within PVC

surface were very noticeable in the case of the PVC (blank)

compared to the films that contain the additives. Such dramatic

changes in the PVC surface in the absence of additives could

be due to the evaluation of HCl or crosslink and chain scission

that lead to the formation of ripples [34,35].

Clearly, the use of photostabilizers 1–3 provides some

protection for PVC against irradiation [36].


PVC + 2.


PVC + 3.

Conclusions

Schiff bases acted as photo-stabilizers to protect PVC

against UV irradiation. The photo-degradation rate

constant (Kd) was high for PVC (blank) in comparison to

those obtained when Schiff bases were used. In addition,

SEM images demonstrated that the cracks and roughness

were minimal in the presence of Schiff bases compared

to the PVC (blank) after irradiation. Schiff base 1 was

found to the most efficient PVC photostabilizers

compared to the others.





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Figure 6. SEM images of PVC (blank) after irradiation (300

h).

Figure 7. SEM images of PVC + 1 after irradiation (300 h).



Acknowledgements

The project was supported by King Saud University, the

Deanship of Scientific Research, Research Chairs, and

Al-Nahrain and Tikrit Universities.





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Documents

Arab Journal of Physical Chemistry- audi … · Dina S. Ahmed,a Gamal A. El-Hiti,*b Hassan Hashim,c Riyadh Noaman,d Ayad S. Hameeda Emad Yousif *e a Department of Chemistry, College

Arab Journal of Physical Chemistry- audi … · Dina S. Ahmed,a Gamal A. El-Hiti,b Hassan Hashim,c Riyadh Noaman,d Ayad S. Hameeda Emad Yousif e a Department of Chemistry, College