New stabilizers for PVC based on some diorganotin(IV) complexes with benzamidoleucine

Emad Yousif; Jumat Salimon; Nadia Salih; Ali Jawad; Yip-Foo Win

doi:10.1016/j.arabjc.2012.03.004

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Original Article

9 (

2_suppl

); S1394-S1401

doi:

10.1016/j.arabjc.2012.03.004

New stabilizers for PVC based on some diorganotin(IV) complexes with benzamidoleucine

Emad Yousif^{^a,⁎}, Jumat Salimon^{^b}, Nadia Salih^{^b}, Ali Jawad^{^c}, Yip-Foo Win^{^d}

a Department of Chemistry, College of Science, Al-Nahrain University, Baghdad, Iraq

b School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia

c School of Chemical Sciences, Universiti Sains Malaysia, 11800 Minden, Penang, Malaysia

d Department of Chemical Science, Faculty of Science, Universiti Tunku Abdul Rahman, Perak Campus, Jalan Universiti, Bandar Barat, 31900 Kampar, Perak, Malaysia

⁎Corresponding author. Tel.: +964 7901782816. emad_yousif@hotmail.com (Emad Yousif)

Received: 2011-12-15, Accepted: 2012-3-13, Published: 2012-11-01

Disclaimer:
This article was originally published by Elsevier and was migrated to Scientific Scholar after the change of Publisher.

Peer review under responsibility of King Saud University.

Abstract

The photostabilization of poly(vinyl chloride) (PVC) films by diorganotin(IV) complexes of the type Ph₂SnL₂, Bu₂SnL₂ and Me₂SnL₂ of the ligand benzamidoleucine complexes was investigated. The PVC films containing concentration of complexes 0.5% by weight were produced by the casting method from tetrahydrofuran (THF) solvent. The photostabilization activities of these compounds were determined by monitoring the carbonyl, polyene and hydroxyl indices with irradiation time. The changes in viscosity average molecular weight of PVC with irradiation time were also tracked (using THF as a solvent). The quantum yield of the chain scission (Φ_cs) of these complexes in PVC films was evaluated and found to range between 5.77 × 10⁻⁸ and 7.26 × 10⁻⁸. Results obtained showed that the rate of photostabilization of PVC in the presence of the additive follows the trend:

Ph₂SnL₂ > Bu₂SnL₂ > Me₂SnL₂

According to the experimental results obtained, several mechanisms were suggested depending on the structure of the additive. Among them HCl scavenging, UV absorption, peroxide decomposer and radical scavenger for photostabilizer additive mechanisms were suggested.

Keywords

Photostabilizer

PVC

Diorganotin(IV)

Benzamidoleucine

Quantum yield

HCI scavenging

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1 Introduction

Poly(vinyl chloride) is second only to polyethylene among the five kinds of general plastic materials, which was widely used in industries including architecture, electronic, chemical engineering, packaging, transportation, etc. (Andrady et al., 1998). However, low photostability of PVC leads to hydrogen chloride loss, discoloration, and finally serious corrosion phenomena, accompanied by changes of physical and chemical properties of PVC.

Poly(vinyl chloride), better known by its abbreviation PVC, is one of the most versatile plastics. It is the second largest manufactured resin by volume worldwide (Saeki and Emura, 2002); currently, its production per annum exceeds 31 million tons. Braun (2004) described the most remarkable milestones in PVC history, their importance to the development of macromolecular chemistry, and some PVC research and industrial applications, with respect to polymerization, stabilization, bulk property modification, and chemical and material recycling of PVC waste.

The low cost and the good performance of poly(vinyl chloride) products have increased the utilization of this polymer in building, mainly in exterior application, such as window profiles, cladding structure and siding (Andrady et al., 1998). However, ultimate user acceptance of the PVC products for outdoor building applications will depend on their ability to resist photodegradation over long periods of sunlight exposure (Yousif et al., 2012a).

To ensure weathering ability, the PVC resin needs to be compounded and processed properly, using suitable additives, leading to a complex material whose behavior and properties are quite different from the PVC resin by itself (Gardette et al., 1993). On the other hand, it is important to perform reliable accelerated weathering test methods. In this regard, factors that influence the degradation of PVC based materials in the service condition, like light and temperature are accelerated.

Almost all synthetic polymers require stabilization against the adverse effect.With the development of synthetic resins it became necessary to look for ways and means to prevent, or at least reduce, the damage caused by environmental parameters such as light, air and heat. This can be achieved through addition of special chemicals, light stabilizers or UV stabilizers, that have to be adjusted to the nature of the resin and the specific application considered. The photostabilization of polymers may be achieved in many ways. The following stabilizing systems have been developed, which depend on the action of stabilizer: (a) light screeners, (b) UV absorbers, (c) excited state quenchers, (d) peroxide decomposers and (e) free radical scavengers, of these it is generally believed that types (c–e) are the most effective. Most of the stabilizers are believed to be multifunctional in their mode of operation. This view is complicated by the fact that mechanisms involved in photo-oxidation in turn depend on the polymer structure and other variables, such as manufacturing, operation, processing and conditions (Harper et al., 1974).

As part of our on-going research in the photostabilization of poly(vinyl chloride), the photostabilization of PVC was studied using diorganotin(IV) complexes with benzamidoleucine as a ligand.

2 Experimental

2.1

2.1 Materials

The following complexes were all prepared by the method described previously. (Farina et al., 2009; Yousif, 2012b).

2.2

2.2 Synthesis of benzamidoleucine

One gram of leucine was dissolved in 25 ml of 5% NaOH solution in a conical flask. To this mixture benzoyl chloride (2.25 mL) was added in five portions in (0.49 ml increments) and shaken vigorously until all the chloride has reacted. Acidified with diluted hydrochloric acid the crude product was washed with cold ether. Finally, the desired product was recrystallized from ethanol.

2.3

2.3 Preparation of complexes

Complexes were synthesized by dissolving the free ligand (2 mmol) in hot toluene and adding the diorganotin salts (1 m mol) to the solution. The solution was refluxed for 6 h with magnetic stirrer and then cooled and filtered. The filtrate was reduced under vacuum to a small volume and solid was precipitated by addition of petroleum ether then filtered, dried at 60 °C and recrystallized from ethanol.

Ph₂SnL₂	C1
Bu₂SnL₂	C2
Me₂SnL₂	C3

3 Experimental techniques

3.1

3.1 Film preparation

Commercial poly(vinyl chloride) supplied by Petkim company (Turkey) was re-precipitated from THF solution by alcohol several times and finally dried under vacuum at room temperature for 24 h. Fixed concentrations of poly(vinyl chloride) solution (5 g/100 ml) in tetrahydrofuran were used to prepare polymer films with 30 μm thickness (measured by a micrometer type 2610 A, Germany). The prepared complexes (0.5% concentrations) were added to the films starting at 0 concentrations (blank). The films were prepared by evaporation technique at room temperature for 24 h. To remove the possible residual tetrahydrofuran solvent, film samples were further dried at room temperature for three hours under reduced pressure. The films were fixed on stands especially used for irradiation. The stand is provided with an aluminum plate (0.6 mm in thickness) supplied by Q-panel company.

4 Irradiation experiments

4.1

4.1 Accelerated testing technique

Accelerated weatherometer Q.U.V. tester (Q. panel, company, USA), was used for irradiation of polymer films. The accelerated weathering tester contains stainless steel plate, which has two holes in the front side and a third one behind. Each side contains a lamp (type Fluorescent Ultraviolet Lights) 40 Watt each. These lamps are of the type UV-B 313 giving spectrum range between 290–360 nm with a maximum at wavelength 313 nm. The polymer film samples were vertically fixed parallel to the lamps to make sure that the UV incident radiation is perpendicular on the samples. The irradiated samples were rotated manually from time to time to ensure that the intensity of light incident on all samples is the same.

5 Photodegradation measuring methods

5.1

5.1 Measuring the photodegradation rate of polymer films using infrared spectrophotometry

The degree of photodegradation of polymer film samples was followed by monitoring FTIR spectra in the range 4000–400 cm⁻¹ using FTIR 8300 Shimadzu Spectrophotometer. The position of carbonyl absorption is specified at 1722 cm⁻¹, polyene group at 1602 cm⁻¹ and the hydroxyl group at 3500 cm⁻¹. The progress of photodegradation during different irradiation times was followed by observing the changes in carbonyl and polyene peaks. Then carbonyl (I_co), polyene (I_po) and hydroxyl (I_OH) indices were calculated by comparison of the FTIR absorption peak at 1722, 1602 and 3500 cm⁻¹ with reference peak at 1328 cm⁻¹ attributed to oscissoring and bending of CH₂ group_, respectively. This method is called band index method (Rasheed et al., 2009).

(1)

I_{s} = \frac{A_{s}}{A_{r}}

As = Absorbance of peak under study.
Ar = Absorbance of reference peak.
Is = Index of group under study.

Actual absorbance, the difference between the absorbance of top peak and base line (a Top Peak – a base line) is calculated using the base line method.

5.2

5.2 B. Determination of average molecular weight ${\overline{M}}_{v})$ using viscometry method

The viscosity property was used to determine the average molecular weight of polymer at room temperature, using the Mark–Houwink relation (Mark, 2007).

(2)

[η] = K {\overline{M}}_{v}^{α}

[η] = the intrinsic viscosity.

K, α = are constants depend upon the polymer–solvent system at a particular temperature.

The intrinsic viscosity of a polymer solution was measured with an Ostwald U-tube viscometer. Solutions were made by dissolving the polymer in a solvent (g/100 ml) and the flow times of polymer solution and pure solvent are t and t₀ respectively. Specific viscosity (η_sp) was calculated as follows:

(3)

η_{re} = \frac{t}{t_{0}}

η_re = Relative viscosity.

(4)

η_{sp} = η_{re} - 1

The single–point measurements were converted to intrinsic viscosities by relation 2.

(5)

[η] = (\sqrt{2} / c) {(η_{sp} - \ln η_{re})}^{1 / 2}

C = Concentration of polymer solution (g/100 ml).

By applying Eq. (5), the molecular weight of degraded and the virgin polymer can be calculated. Molecular weights of PVC with and without additives were calculated from intrinsic viscosities measured in THF solution using the following equation:

(6)

[η] = 1.38 \times 10^{- 4} {Mv}^{0.77}

The quantum yield of main chain scission (ф_cs) (Nakajima et al., 1990) was calculated from viscosity measurement using the following relation 7.

(7)

ϕ_{cs} = (CA / {\overline{M}}_{v, 0}) [{([η_{0}] / [η])}^{1 / α} - 1] / I_{0} t

where: C = concentration; A = Avogadro's number;

({\overline{M}}_{v,o})

= the initial viscosity-average molecular weight; [η_o] = intrinsic viscosity of PVC before irradiation; I_o = incident intensity and t = irradiation time in second.

6 Results and discussion

The diorganotin(IV) complexes were used as additives for the photostabilization of PVC films. In order to study the photochemical activity of these additives for the photostabilization of PVC films, the carbonyl and polyene indices were monitored with irradiation time using IR spectrophotometry. The irradiation of PVC films with UV light of wavelength, λ = 313 nm led to a clear change in the FTIR spectrum, as shown in Fig. 1. Appearance of bands in 1772 cm⁻¹ and 1724 cm⁻¹, were attributed to the formation of carbonyl groups related to chloroketone and to aliphatic ketone, respectively. A third band was observed at 1604 cm⁻¹, related to polyene group. The hydroxyl band appeared at 3500 cm⁻¹ was annotated to the hydroxyl group (Andrady and Searle, 1989).

Change in IR spectrum of PVC film (blank) (30 μm) in the presence of C2 complex. A at zero time and B after 250 h.

The absorption of the carbonyl, polyene and hydroxyl groups was used to follow the extent of polymer degradation during irradiation. This absorption was calculated as carbonyl index (I_co), polyene index (I_po) and hydroxyl index (I_OH). It is reasonable to assume that the growth of carbonyl index is a measure of the extent of degradation. However, in Fig. 2, the I_co of C3, C2 and C1 showed a lower growth rate with irradiation time with respect to the PVC blank film without additives. Since the growth of carbonyl index with irradiation time is lower than PVC blank, as seen in Fig. 2, it is suitable to conclude that these additives might be considered as photostabilizers of PVC polymer. Efficient photostabilizer shows a longer induction period. Therefore, C1 is the most active photostabilizer, followed by C2 and C3 which is the least active. Just like carbonyl, polyene compounds are also produced during photodegradation of PVC. Therefore, polyene index (I_po) could also be monitored with irradiation time in the presence and absence of these additives. Results are shown in Fig. 3.

Relationship between carbonyl index and irradiation time for PVC films (30 μm thickness) containing different additives. Concentration of additives is fixed at 0.5% by weight.

Relationship between polyene index and irradiation time for PVC films (30 μm thickness). Containing different additives, concentration of additives is fixed at 0.5% by weight.

Hydroxyl species were produced during photodegradation of PVC. Therefore, hydroxyl index (I_OH) was monitored with irradiation time for PVC and with additives. From Fig. 4, C3, C2 and C1 showed a lower growth rate of hydroxyl index with irradiation time compared to PVC film without modification.

Relationship between hydroxyl index and irradiation time for PVC films (30 μm thickness). Containing different additives, concentration of additives is fixed at 0.5% by weight.

7 Variation of PVC molecular weight during photolysis in the presence of diorganotin(IV) complexes

Analysis of the relative changes in viscosity average molecular weight ${\overline{M}}_{v})$ , has been shown to provide a versatile test for random chain scission. Fig. 5 shows the plot of ${\overline{M}}_{v})$ , versus irradiation time for PVC film with and without 0.5% (w/w) of the selected additives, with an absorbed light intensity of 1.052 × 10⁻⁸ ein dm⁻³ s⁻¹ ${\overline{M}}_{v})$ , is measured using Eq. (4) with THF as a solvent at 25 ^oC .

Changes in the viscosity-average molecular weight ( M ‾ v ) during irradiation of PVC films (30 μm) (blank) and with 0.5 wt.% of additives.

It is worth mentioning that traces of the films with additives are not soluble in THF indicating that cross-linking or branching in the PVC chain does occur during the course of photolysis (Rabek and Ranby, 1975). For better support of this view, the number of average chain scissions (average number cut per single chain) (S) (Shyichuk and White, 2000) was calculated using relation 8:

(8)

S = ({\overline{M}}_{v, 0} / {\overline{M}}_{v, t}) - 1

where

{\overline{M}}_{v,o}

and

{\overline{M}}_{v,t}

are viscosity average molecular weight at initial (0) and t irradiation times respectively. The plot of S versus time is shown in Fig. 6. The curve indicates an increase in the degree of branching such as that might arise from cross-linking occurrence. It is observed that an insoluble material was formed during irradiation which provided additional evidence to the idea that cross-linking does occur.

Changes in the main chain scission (S) during irradiation of PVC films (30 μm) (blank) and with 0.5 wt.% of additives.

For randomly distributed weak bond links, which break rapidly in the initial stages of photodegradation, the degree of deterioration α is given as:

(9)

α = \frac{m \cdot s}{{\overline{M}}_{v}}

where m is the initial molecular weight.

The plot of α as a function of irradiation time is shown in Fig. 7.

Changes in the degree of deterioration (α) during irradiation of PVC films (30 μm) (blank) and with 0.5 wt.% of additives.

The values of α of the irradiated samples are higher when additives are absent and lower in the presence of additives compared to the corresponding values of the additive free PVC. In the initial stages of photodegradation of PVC, the value of α increases rapidly with time, these indicators indicate a random breaking of bonds in the polymer chain. Another way of degradation reaction characterization is the measurement of the quantum yield of the chain scission (Φ_cs). The quantum yield for chain scission was calculated for PVC films with and without 0.5% (wt/wt) of additive mentioned above using relation 5. The Φ_cs values for complexes are tabulated in Table 1.

Table 1 Quantum yield (Φcs) for the chain scission for PVC films (30 μm) thickness with and without 0.5 (wt/wt) additive after 250 h. irradiation time.

Additive (0.5%wt)	Quantum yield of main chain scission (Φ_cs)
PVC + C1	5.77E-08
PVC + C2	6.26E-08
PVC + C3	7.26E-08
PVC(blank)	8.56E-05

The Φ_cs values for PVC films in the presence of additive are less than that of additive free PVC (blank), which increase in the order:

It is well established that the quantum yield (Φ_cs.) increases with increasing temperature (Jellinek, 1978) around the glass transition temperature, (Tg) of the amorphous polymer, and around the melting temperature of crystalline polymers. In the study presented in this work, the photolysis of PVC film is carried out at a temperature of 35–45 °C well below the glass transition temperature (Tg of PVC = 80 °C). Therefore, the Φ_cs dependency on temperature is not expected to be observed.

8 Suggested mechanisms of photostabilization of PVC by diorganotin(IV) complexes

Depending on the overall results obtained, the efficiency of diorganotin(IV) complexes as stabilizer for PVC films can be arranged according to the change in the carbonyl, polyene and hydroxyl concentration as a reference for comparison as shown in Figs. 2–4 , as follows: $C 1 > C 2 > C 3$ Sn carboxylates stabilize PVC by two mechanisms, depending on the metal. Strongly basic carboxylates, which have little or no Lewis acidity, are mostly HCl scavengers, Scheme 1. Metals such as Sn, Zn, Cd and Cu which are stronger Lewis acids and form covalent carboxylates, not only scavenge HCl, but also substitute carboxylate for the allylic chlorine atoms. These stabilizers provide very good long-term stability and are usually referred to as secondary stabilizers, Scheme 1. Similar mechanism was suggested by Yousif et al. (2009) for photostabilizing of PVC using 2-thioacetic acid -5-phenyl-1,3,4-oxadiazole complexes.

Suggested mechanism of photostabilization of complexes as HCl scavengers.

IR spectroscopy has shown that metal carboxylates associate with PVC molecules at the surface of primary particles and are, consequently, very effective in the substitution of allylic chlorine. In this mechanism, the stabilizer is classified as a primary stabilizer. It has been postulated that metal stabilizers associate with chlorine atoms at the surface of PVC primary particles which explains their high efficiency in PVC stabilization (Yousif et al., 2011a), Scheme 2.

Suggested mechanism of photostabilization of complexes as primary stabilizers.

Metal chelate complexes generally known as photostabilizers for PVC through both peroxide decomposer and excited state quencher. Therefore, it is expected that these complexes act as peroxide decomposer through the following proposed mechanism, Scheme 3. This mechanism is in agreement with that reported by Adil et al., 2011.

Suggested mechanism of photostabilization of complexes as peroxide decomposer.

These metal chelate complexes also function as radical scavengers through energy transfer and by forming un-reactive charge transfer complexes between the metal chelate and excited state of the chromophore (POO^.) and stabilize through resonating structures as shown in Scheme 4. This mechanism is adopted by Yousif et al., 2011b.

Suggested mechanism of photostabilization of carboxylate complexes as radical scavengers through energy transfer and formation of unreactive charge transfer and stabilization through resonating structure.

The ring of benzene in this compound plays an important role in the mechanism of stabilizing process by acting as UV absorber. The UV light absorption by these additives containing benzene ring dissipates the UV energy to harmless heat energy, Scheme 5. Furthermore this ring plays a role in resonating structure conjugation of radical in peroxide decomposer which supports this compound as a photostabilizer (Yousif et al., 2010).

Suggested mechanism of photostabilization of benzene ring as UV absorber.

9 Conclusions

In the work described in this paper, the photostabilization of poly(vinyl chloride) films using diorganotin(IV) complexes was studied. These additives behave successfully as photostabilizer for PVC films. The additives take the following order in photostabilization activity according to their decrease in carbonyl, polyene and hydroxyl indices for PVC films. $C 1 > C 2 > C 3 .$ These additives stabilize the PVC films through HCl scavenging, UV absorption or screening, peroxide decomposer and radical scavenger mechanisms. The tin complexes were found to be more efficient in photostabilization process according to the photostability and mechanisms mentioned above. These mechanisms support the idea of using tin complexes as commercial stabilizer for PVC.

Acknowledgements

E. Yousif is grateful to Universiti Kebangsaan Malaysia for funding (“Code UKM-GUP-NBT-08-27-113), and Department of Chemistry, College of Science, AL-Nahrain University.

References

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Show Sections

[1] Adil H., Yousif E., Salimon J., . New Stabilizers For PVC Based On Benzothiazole Complexes. Germany: LAMBERT Academic Publishing; 2011.

[2] Andrady A., Hamid S., Hu X., Torikai A., . Effects of increased solar ultraviolet radiation on materials. J. Photochem. Photobiol. B. 1998;46:96-103.
[Google Scholar]

[3] Andrady A., Searle N., . Photodegradation of rigid PVC formulations. II. Spectral sensitivity to light-induced yellowing by polychromatic light. J. Appl. Polym. Sci.. 1989;37:2789-2802.
[Google Scholar]

[4] Braun D., . Poly(vinyl chloride) on the way from the 19th century to the 21st century. J. Polym. Sci. A Polym. Chem.. 2004;42:578-586.
[Google Scholar]

[5] Farina Y., Adil H., Ahmed A., Graisa A., Yousif E., . Synthesis, Structural and Fungicidal Studies of Some Diorganotin(IV) with Benzamidoleucine. Aust. J. Basic Appl. Sci.. 2009;3(3):1670-1673.
[Google Scholar]

[6] Gardette J., Gaumet S.J.L., Philippart J., . Influence of the experimental conditions on the photooxidation of poly(vinyl chloride) J. Appl. Polym. Sci.. 1993;48(11):1885-1895.
[Google Scholar]

[7] Harper D., McKellar N., Turner P., . Photostabilizing effect of Ni(II) chelates in polymers II. Effect of diamagnetic chelates on polypropylene phosphorescence. J. Appl. Polym. Sci.. 1974;311:2802-2805.
[Google Scholar]

[8] Jellinek H., . Aspects of Degradation and Stabilization of Polyolefines. Amsterdam: Elsevier; 1978.

[9] Mark J., . Physical properties of polymers handbook. New York: Springer; 2007.

[10] Nakajima N., Sadeghi M., Kyu T., . Photodegradation of poly(methyl methacrylate) by monochromatic light: quantum yield, effect of wavelengths, and light intensity. J. Appl. Polym. Sci.. 1990;41:889-1363.
[Google Scholar]

[11] Rabek J., Ranby B., . Photodegradation, photooxidation and photostabilization of Polymers. New York: John Wiley; 1975.

[12] Rasheed R., Mansoor H., Yousif E., Hameed A., Farina A., Graisa A., . Photostabilizing of PVC films by 2-(aryl)-5-[4-(aryloxy)-phenyl]-1,3,4-oxadiazole compounds. Eur. J. Sci. Res.. 2009;30(3):464-477.
[Google Scholar]

[13] Saeki Y., Emura T., . Technical progresses for PVC production. Prog. Polym. Sci.. 2002;27:2055-2131.
[Google Scholar]

[14] Shyichuk A., White J., . Analysis of chain-scission and crosslinking rates in the photo-oxidation of polystyrene. J. Appl. Polym. Sci.. 2000;77(13):3015-3023.
[Google Scholar]

[15] Yousif E., Aliwi S., Ameer, Ukal J., . Improved photostability of PVC films in the presence of 2-thioacetic acid -5-phenyl-1,3,4-oxadiazole complexes. Turkish J. Chem.. 2009;33:399-410.
[Google Scholar]

[16] Yousif E., Hameed A., Rasheed R., Mansoor H., Farina Y., Graisa A., Salih N., Salimon J., . Synthesis and Photostability Study of Some Modified Poly(vinyl chloride) Containing Pendant Benzothiazole and Benzimidozole Ring. Int. J. Chem.. 2010;2(1):65-80.
[Google Scholar]

[17] Yousif E., Salimon J., Salih N., Ahmed A., . Improvement of the photostabilization of PMMA films in the presence 2N-salicylidene-5-(substituted)-1,3,4-thiadiazole. J. King Saud University (Science). 2012;24:11-17.
[Google Scholar]

[18] Yousif E., Salih N., Salimon J., . Improvement of the photostabilization of PVC films in the presence of thioacetic acid benzothiazole complexes. The Malaysian J. Analy. Sci.. 2011;15(1):81-92.
[Google Scholar]

[19] Yousif E., Salih N., Salimon J., . Improvement of the Photostabilization of PVC Films in the Presence of 2N-Salicylidene-5-(Substituted)-1,3,4-Thiadiazole. J. Appl. Poly. Sci.. 2011;120:2207-2214.
[Google Scholar]

[20] Yousif E., . Synthesis, spectroscopic studies and fungicidal activity of some diorganotin(IV) with 2-[(phenylcarbonyl)amino]propanoate. J. King Saud University (Science). 2012;24:167-170.
[Google Scholar]

New stabilizers for PVC based on some diorganotin(IV) complexes with benzamidoleucine

Abstract

Keywords

Photostabilizer

PVC

Diorganotin(IV)

Benzamidoleucine

Quantum yield

HCI scavenging

1 Introduction

2 Experimental

2.1 Materials

2.2 Synthesis of benzamidoleucine

2.3 Preparation of complexes

3 Experimental techniques

3.1 Film preparation

4 Irradiation experiments

4.1 Accelerated testing technique

5 Photodegradation measuring methods

5.1 Measuring the photodegradation rate of polymer films using infrared spectrophotometry

5.2 B. Determination of average molecular weight M ‾ v ) using viscometry method

6 Results and discussion

7 Variation of PVC molecular weight during photolysis in the presence of diorganotin(IV) complexes

8 Suggested mechanisms of photostabilization of PVC by diorganotin(IV) complexes

9 Conclusions

Acknowledgements

References

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5.2 B. Determination of average molecular weight ${\overline{M}}_{v})$ using viscometry method