- Email: [email protected]
starch blends
Materials Today: Proceedings xxx (xxxx) xxx
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Study of the mechanical properties of polyvinyl alcohol/starch blends Bushra H. Musa, Nahida J. Hameed ⇑ Applied Science Department, Material Science, University of Technology, Baghdad, Iraq
a r t i c l e
i n f o
Article history: Received 9 July 2019 Received in revised form 5 September 2019 Accepted 29 September 2019 Available online xxxx Keywords: PVA Starch Tensile strength Elongation Young’s modulus Solution casting process
a b s t r a c t In this work, the solution casting technique was used to prepare polymer blend films based on Poly (vinyl alcohol)/corn starch. Tensile machine and optical microscope were used to characterize the prepared samples. The starch content with different weight ratios (25, 30, 35, 40 and 50) wt% was added to PVA. The results show that the addition of starch to PVA causes a significant decrease in the elongation and tensile strength, while Young’s modulus increased. It was also observed from optical microscope, a good image of the starch particle distribution was obtained for the blend films up to 30 wt% of starch. Extra increase in starch content of 35, 40, 50 wt% led to agglomeration and the formation of voids in the films. The PVA/starch blends were studied with the aim of its use in drug delivery applications. Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the 2nd International Conference on Materials Engineering & Science.
1. Introduction In the last 50 years, hydrogels have received a great attention because they have used in a wide variety of applications [1] such as biomedical field, which includes contact lenses, catheters, wound dressing, artificial corneas, coating for sutures, and electrode sensors [2] biomedical devices, carrier for cell immobilization, bio separation membranes [3], intelligent carrier matrices in controlled drug delivery systems, and tissue engineering process [4]. They are able to mimic tissues , they do not cause irritation , and natural extra cellular matrices because of their flexibility, depending on their chemical composition [5]. Hydrogels are three-dimensional (physically or chemically) crosslinked networks of polymer chains [2,1]. These crosslinked networks make the gel insoluble in water [2]. Hydrogels are able to swell in water or biological fluids and keep a significant fraction of water within its structure not including that dissolved in water [2]. As a result of the existence of hydrophilic functional groups, such as (–OH, –SO3H, –COOH, –CONH2) in some polymeric chains, hydrogels absorb most liquids which have water base. Therefore, they respond to the conditions of the nearby environment, such as temperature, pH or ionic strength of the swelling solutions or even to ultraviolet light. Hence, they are called as being smart materials [2].
⇑ Corresponding author.
Polyvinyl alcohol (PVA) is a thermoplastic synthetic polymer, biodegradable, non-toxic, highly hydrophilic properties, semicrystalline, excellent film forming capacity by solution casting, chemical resistance, adhesive properties, and high thermal stability. Due to the presence of these properties, their role in the material industry is increasing as a thickener in polyvinyl acetate, emulsifier, textile sizing agent, membrane material and it also used in support structure for 3D printing and vinylon fiber production [3,6,7]. Due to its poor mechanical properties, PVA can be improved by blending with other mechanically strong polymers [4]. Among many natural polymers, starch is a suitable material with good potential due to its easy availability, biodegradability, and relatively low cost. It is the major form of saved carbohydrate in plants, for example (corn, rice, potatoes, and wheat) [8]. Thermoplastic corn starch cannot be used in wide range of applications due to being humidity sensitive, lack of a water obstacle property, and inferior mechanical properties, such as film brittleness as a result of the high intermolecular forces. Generally, solution casting method is used to produce the PVA/ starch blends because it is a simple technique which provides a uniform thickness, very low haze and maximum optical purity [9]. Therefore, many efforts have been attempted to overcome these issues and improve the properties of starch biodegradable products by blending it with other renewable polymers, such as PVA for various applications [10]. Polyvinyl alcohol/starch polymer blend is one of the most common biodegradable polymer blends. However, both mechanical
E-mail address: [email protected] (N.J. Hameed). https://doi.org/10.1016/j.matpr.2019.09.161 2214-7853/Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the 2nd International Conference on Materials Engineering & Science.
Please cite this article as: B. H. Musa and N. J. Hameed, Study of the mechanical properties of polyvinyl alcohol/starch blends, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.161
2
B.H. Musa, N.J. Hameed / Materials Today: Proceedings xxx (xxxx) xxx
and physical properties of the PVA/starch blended systems are considered lower than those of conventional polymers [7]. Several researchers have worked with starch-based blends and their different properties. Hameed et al. have worked on the mechanical properties of corn starch/PVA blends and effect of adding SiO2 particles on it [11]. Otey et al. have also worked on the extraction of starch from potato and blending with PVA. Other researcher have worked on crosslinking and processing similar blends [12]. In this present work, PVA/ Starch blend films were prepared by cast method, and elongation, tensile strength, and Young’s modulus were investigated. The investigation considered the effect of
corn starch as additive on the mechanical properties of PVA for use in drug delivery applications. 2. Materials and methods 2.1. Materials 1. A white powder of poly (vinyl alcohol) (PVA) with purity 99.9% having an average molecular weight of (12000–18000) was obtained from Panreac (Barcelona, Espana). 2. Corn starch with purity 99.9% was obtained from Panreac (Barcelona, Espana).
Fig. 1. Relation between stress and strain under tensile test.
Fig. 2. (a) Effect of PVA/St ratio on Tensile strength; (b) Effect of PVA/St ratio on Elongation; (c) Effect of PVA/St ratio on Young’s modulus.
Please cite this article as: B. H. Musa and N. J. Hameed, Study of the mechanical properties of polyvinyl alcohol/starch blends, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.161
B.H. Musa, N.J. Hameed / Materials Today: Proceedings xxx (xxxx) xxx
2.2. Sample preparation 2.2.1. PVA films preparation PVA was prepared by solution casting technique. 10 g of purified polyvinyl alcohol was dissolved in 100 ml of distilled water at 90 °C. During the mixing stage polymer solution was mixed by using mechanical magnetic stirrer for one hour to have good homogeneity of the mixture. This solution was then cooled gradually to room temperature, and then poured onto a glass plate to be cured for 24 h. 2.2.2. The PVA/St blend films preparation PVA/St films were prepared by solution casting technique from different weight percentage ratios of both (PVA) and starch (St) (100/0, 75/25, 70/30, 65/35,60/40, 50/50)wt/wt%. Weight of polyvinyl alcohol was dissolved in 100 ml of distilled water at 85–90 °C by stirring for one hour until a clear solution was obtained. This solution was left to cool at room temperature while stirring; after that starch was added with continuous stirring to obtain a homogeneous solution for the mixture. Finally, the prepared solution was poured on to a glass plate of dimensions 30*30 cm and left for 48 h to dry in air.
out at the University of Technology /material engineering department by tensile machine of (LARYEE-50 KN, China), and the samples were cut according to ‘‘ASTM standard Test Method for Tensile Properties of Thin Plastic Sheeting ‘‘ D882-02 to determine the elongation (%E), tensile strength (TS), and Young’s modulus (Y). The test samples are stripped of length at least 50 mm longer than the grip separation distance, the width must be not less than 5 mm or greater than 25.4 mm while the thickness is less than 1 mm. Crosshead speed used was 5 mm/ min. This test was done at room temperature. 2.3.2. Elongation The percentage of elongation (%EL) (Tensile strain at break) is determined as follows [14]:
Elongation ð%ELÞ ¼
ðLf Li Þ 100 Li
2.3.3. Young’s modulus Young’s modulus was calculated by the equation [14]: 0
2.3.1. Tensile strength Tensile strength (TS) is the capability of a material to withstand forces that stretch before failure [13]. The tensile test was carried
ð1Þ
where Li: is the final length and Lf: is the initial length.
Young s Modulus ðY Þ ¼
2.3. Mechanical properties
3
FLi A 0DL
ð2Þ
where F: is the force exerted on a sample;DL: is the change in length of the sample; Ao: is the original cross-sectional area of the sample and Li: is the original sample length [14].
Fig 3. Optical microscope micrographs of (PVA/Starch) blend films.
Please cite this article as: B. H. Musa and N. J. Hameed, Study of the mechanical properties of polyvinyl alcohol/starch blends, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.161
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Table 1 Tensile properties of PVA/starch blend films. Samples PVA (75% (70% (65% (60% (50%
PVA/25% PVA/30% PVA/35% PVA/40% PVA/50%
% w/w solids St) St) St) St) St)
blend blend blend blend blend
10%
Tensile strength (MPa)
Young’s Modulus(MPa)
(Elongation) (%)
60.5 60.08 53.98 51.98 42.64 35.97
16.7 32.99 23.68 34.76 30.76 37.87
153.99 5.48 4.046 2.65 2.36 1.14
2.3.4. Optical microscope The morphology of PVA, PVA /St blend films was investigated by using an optical microscope of MEIJI TECHNO CO., LTD, model: MT9430 made in Japan with magnification 10X.
sion between the two components. As a result, the tensile strength decreases [14,17]. Table 1 shows mechanical properties (elongation (% E), tensile strength (TS) and Young’s modulus (Y) of PVA/St blend films under tension tests.
3. Results and discussion
4. Conclusions
Fig. 1 indicates depicts the relation between stress and strain under tensile test. It was shown that the tensile strength and elongation decreased with increase in corn starch contents. However, Young’s modulus increased with increase of starch contents. Fig. 2(a) shows the addition of starch to PVA causing a decrease in tensile strength due to the decrease in hydrogen bonding density in the polymer and hard segment contents. This result was in agreement with (Hameed& Abd-alrhman 2018) [11]. Also, the cross sectional area of the PVA decreased with the increase of corn starch content and this effect can be attributed to the amorphous nature of starch that raised the brittleness, which led to reduction in the tensile strength of the film. This work was similar to (Tang et al., 2008) [15]. The results proved that the highest tensile strength value of the films was (60.08 MPa) at 75/25 wt/wt% of the PVA/starch blend. In Fig. 2(b) it can be observed that the elongation at break decreases with increase of the starch, while the PVA concentration had the maximum percentage of elongation value (153.99%) compared with other blends. This is because PVA experiences a great plastic deformation, while the PVA/ starch films undergo slighter plastic deformation. This was related to the stress exerted cannot be transferred equally to the PVA matrix. So, the stress which was exerted will be concentrated on the voids which are full of the starch particles and also the agglomerated starch particles. These results were similar to (Guohua et al. 2006) who found that the percentage of elongation decreased with a starch content increase [16]. It can be seen from Fig. 2(c), the Young modulus increased with increasing starch amount. The highest modulus of elasticity was found at 50/50 wt/wt% of PVA/ corn starch blend with the value of 37.87 MPa. The enhancement of modulus of elasticity was related to stiff starch particles that are embedded in the PVA matrix and the variation in the feature of the polymer compound (Kocsis & Fakirov, 2009) [17]. These results also were in agreement with prior work by (Yee et al. 2011) [18]. Nevertheless, it shows that the Young’s modulus decreases in samples of 30 and 40 wt% of starch content. Young’s modulus is inversely proportional withelongation. In Fig. 3, it is observed from the optical microscope that a smooth surface of the PVA matrix and a regular distribution of the starch particles were achieved in the blend film with (0, 25, 30 wt%) of the starch. Extra increase in starch content led to agglomeration then it caused formation of voids in the polymer matrix. These voids and agglomeration led to poor interfacial adhe-
The results revealed that the addition of starch to plastic PVA phase led to: 1. A significant decrease in elongation and tensile strength, while Young’s modulus was increased due to the brittle nature of starch. 2. It was also observed from optical microscope, that a good image of the starch particle distribution was obtained for the blend films up to 30 wt% of starch. However, agglomerates can be seen in the blend films with 35, 40, 50 wt% of starch content. 3. PVA/starch blends were studied to be used in drug delivery applications.
Acknowledgements The authors are grateful to the Department of Applied Sciences for the support and to MuaedFaikabd al Majed for his efforts. References [1] E.M. Ahmed, J. Adv. Res. 6 (2015) 105–121. [2] N.M. Ranjha, J. Pharmacy Altern. Med. 2 (2013) 30–41. [3] H. Hristov, P. Vasileva, M. Nedialkova, Preparation and characterization of PVA/ PEG/BORON hybrid materials, Nanoscience & Nanotechnology, 12. (Eds), E. Balabanova, E. Mileva, Sofia, 2012, pp. 47–51. [4] M. Abu Ghalia, Y. Dahman, J. Polym. Res. 22 (2015) 1–9. [5] M.D. Figueroa-Pizanoa, I. Vélaz, F.J. Peñas, P. Zavala-Rivera, A.J. Rosas-Durazo, A.D. Maldonado-Arce, M.E. Martínez-Barbosa, Carbohydr. Polym. 195 (2018) 476–485. [6] A.K. Sonker, K. Rathore, R.K. Nagarale, J. Polym. Environ. 26 (2018) 1782–1794. [7] L.d. Sol González-Forte1, O.R. Pardini1, J. Amalvy, J. Compos. Biodegradable Polymers 4 (2016) 2–10. [8] X. Tang, S. Alavi, Carbohydr. Polym. 85 (2011) 7–16. [9] A.M. Grumezescu, A. Holban, Food Packaging and Preservation, Academic Press, 2017, p. 246. [10] Y.H. Yun, Y.N. Youn, S.D. Yoon, J.U. Lee, Ceramic Process. Res. 13 (2012) 59–64. [11] N.J. Hameed, A.S. Abd-alrhman, Iraqi J. Phys. 16 (2018) 153–171. [12] S.D. Sadhu, A. Soni, S.I.G. Varmani, M. Garg, Int. J. Pharm. Sci. Invention 3 (2014) 33–37. [13] S.S. Shafik, K.J. Majeed, M.I. Kamil, Int. J. Mater. Sci. Applications 3 (2014) 25– 28. [14] F.E.F. Silva, M.C.B. Di-Medeiros, K.A. Batista, K.F. Fernandes, J. Mater. 1 (2013) 1–6. [15] S. Tang, P. Zou, H. Xiong, H. Tang, Carbohydr. Polym. 72 (2008) 521–526. [16] Z. Guohua, L. Ya, F. Cuilan, Z. Min, Z. Caiqiong, C. Zongdao, Polym. Degrad. Stab. 91 (2006) 703–711. [17] J.K. Kocsis, S. Fakirov, Nano- and Micro – Mechanics of Polymer Blends and Composites, Carl Hanser Verlag, Munich, 2009. [18] T.W. Yee, L.J. Choy, W.A.W. Abdul Rahman, J. Compos. Mater. 45 (2011) 1201– 1207.
Please cite this article as: B. H. Musa and N. J. Hameed, Study of the mechanical properties of polyvinyl alcohol/starch blends, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.161
Contents lists available at ScienceDirect
Materials Today: Proceedings journal homepage: www.elsevier.com/locate/matpr
Study of the mechanical properties of polyvinyl alcohol/starch blends Bushra H. Musa, Nahida J. Hameed ⇑ Applied Science Department, Material Science, University of Technology, Baghdad, Iraq
a r t i c l e
i n f o
Article history: Received 9 July 2019 Received in revised form 5 September 2019 Accepted 29 September 2019 Available online xxxx Keywords: PVA Starch Tensile strength Elongation Young’s modulus Solution casting process
a b s t r a c t In this work, the solution casting technique was used to prepare polymer blend films based on Poly (vinyl alcohol)/corn starch. Tensile machine and optical microscope were used to characterize the prepared samples. The starch content with different weight ratios (25, 30, 35, 40 and 50) wt% was added to PVA. The results show that the addition of starch to PVA causes a significant decrease in the elongation and tensile strength, while Young’s modulus increased. It was also observed from optical microscope, a good image of the starch particle distribution was obtained for the blend films up to 30 wt% of starch. Extra increase in starch content of 35, 40, 50 wt% led to agglomeration and the formation of voids in the films. The PVA/starch blends were studied with the aim of its use in drug delivery applications. Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the 2nd International Conference on Materials Engineering & Science.
1. Introduction In the last 50 years, hydrogels have received a great attention because they have used in a wide variety of applications [1] such as biomedical field, which includes contact lenses, catheters, wound dressing, artificial corneas, coating for sutures, and electrode sensors [2] biomedical devices, carrier for cell immobilization, bio separation membranes [3], intelligent carrier matrices in controlled drug delivery systems, and tissue engineering process [4]. They are able to mimic tissues , they do not cause irritation , and natural extra cellular matrices because of their flexibility, depending on their chemical composition [5]. Hydrogels are three-dimensional (physically or chemically) crosslinked networks of polymer chains [2,1]. These crosslinked networks make the gel insoluble in water [2]. Hydrogels are able to swell in water or biological fluids and keep a significant fraction of water within its structure not including that dissolved in water [2]. As a result of the existence of hydrophilic functional groups, such as (–OH, –SO3H, –COOH, –CONH2) in some polymeric chains, hydrogels absorb most liquids which have water base. Therefore, they respond to the conditions of the nearby environment, such as temperature, pH or ionic strength of the swelling solutions or even to ultraviolet light. Hence, they are called as being smart materials [2].
⇑ Corresponding author.
Polyvinyl alcohol (PVA) is a thermoplastic synthetic polymer, biodegradable, non-toxic, highly hydrophilic properties, semicrystalline, excellent film forming capacity by solution casting, chemical resistance, adhesive properties, and high thermal stability. Due to the presence of these properties, their role in the material industry is increasing as a thickener in polyvinyl acetate, emulsifier, textile sizing agent, membrane material and it also used in support structure for 3D printing and vinylon fiber production [3,6,7]. Due to its poor mechanical properties, PVA can be improved by blending with other mechanically strong polymers [4]. Among many natural polymers, starch is a suitable material with good potential due to its easy availability, biodegradability, and relatively low cost. It is the major form of saved carbohydrate in plants, for example (corn, rice, potatoes, and wheat) [8]. Thermoplastic corn starch cannot be used in wide range of applications due to being humidity sensitive, lack of a water obstacle property, and inferior mechanical properties, such as film brittleness as a result of the high intermolecular forces. Generally, solution casting method is used to produce the PVA/ starch blends because it is a simple technique which provides a uniform thickness, very low haze and maximum optical purity [9]. Therefore, many efforts have been attempted to overcome these issues and improve the properties of starch biodegradable products by blending it with other renewable polymers, such as PVA for various applications [10]. Polyvinyl alcohol/starch polymer blend is one of the most common biodegradable polymer blends. However, both mechanical
E-mail address: [email protected] (N.J. Hameed). https://doi.org/10.1016/j.matpr.2019.09.161 2214-7853/Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the 2nd International Conference on Materials Engineering & Science.
Please cite this article as: B. H. Musa and N. J. Hameed, Study of the mechanical properties of polyvinyl alcohol/starch blends, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.161
2
B.H. Musa, N.J. Hameed / Materials Today: Proceedings xxx (xxxx) xxx
and physical properties of the PVA/starch blended systems are considered lower than those of conventional polymers [7]. Several researchers have worked with starch-based blends and their different properties. Hameed et al. have worked on the mechanical properties of corn starch/PVA blends and effect of adding SiO2 particles on it [11]. Otey et al. have also worked on the extraction of starch from potato and blending with PVA. Other researcher have worked on crosslinking and processing similar blends [12]. In this present work, PVA/ Starch blend films were prepared by cast method, and elongation, tensile strength, and Young’s modulus were investigated. The investigation considered the effect of
corn starch as additive on the mechanical properties of PVA for use in drug delivery applications. 2. Materials and methods 2.1. Materials 1. A white powder of poly (vinyl alcohol) (PVA) with purity 99.9% having an average molecular weight of (12000–18000) was obtained from Panreac (Barcelona, Espana). 2. Corn starch with purity 99.9% was obtained from Panreac (Barcelona, Espana).
Fig. 1. Relation between stress and strain under tensile test.
Fig. 2. (a) Effect of PVA/St ratio on Tensile strength; (b) Effect of PVA/St ratio on Elongation; (c) Effect of PVA/St ratio on Young’s modulus.
Please cite this article as: B. H. Musa and N. J. Hameed, Study of the mechanical properties of polyvinyl alcohol/starch blends, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.161
B.H. Musa, N.J. Hameed / Materials Today: Proceedings xxx (xxxx) xxx
2.2. Sample preparation 2.2.1. PVA films preparation PVA was prepared by solution casting technique. 10 g of purified polyvinyl alcohol was dissolved in 100 ml of distilled water at 90 °C. During the mixing stage polymer solution was mixed by using mechanical magnetic stirrer for one hour to have good homogeneity of the mixture. This solution was then cooled gradually to room temperature, and then poured onto a glass plate to be cured for 24 h. 2.2.2. The PVA/St blend films preparation PVA/St films were prepared by solution casting technique from different weight percentage ratios of both (PVA) and starch (St) (100/0, 75/25, 70/30, 65/35,60/40, 50/50)wt/wt%. Weight of polyvinyl alcohol was dissolved in 100 ml of distilled water at 85–90 °C by stirring for one hour until a clear solution was obtained. This solution was left to cool at room temperature while stirring; after that starch was added with continuous stirring to obtain a homogeneous solution for the mixture. Finally, the prepared solution was poured on to a glass plate of dimensions 30*30 cm and left for 48 h to dry in air.
out at the University of Technology /material engineering department by tensile machine of (LARYEE-50 KN, China), and the samples were cut according to ‘‘ASTM standard Test Method for Tensile Properties of Thin Plastic Sheeting ‘‘ D882-02 to determine the elongation (%E), tensile strength (TS), and Young’s modulus (Y). The test samples are stripped of length at least 50 mm longer than the grip separation distance, the width must be not less than 5 mm or greater than 25.4 mm while the thickness is less than 1 mm. Crosshead speed used was 5 mm/ min. This test was done at room temperature. 2.3.2. Elongation The percentage of elongation (%EL) (Tensile strain at break) is determined as follows [14]:
Elongation ð%ELÞ ¼
ðLf Li Þ 100 Li
2.3.3. Young’s modulus Young’s modulus was calculated by the equation [14]: 0
2.3.1. Tensile strength Tensile strength (TS) is the capability of a material to withstand forces that stretch before failure [13]. The tensile test was carried
ð1Þ
where Li: is the final length and Lf: is the initial length.
Young s Modulus ðY Þ ¼
2.3. Mechanical properties
3
FLi A 0DL
ð2Þ
where F: is the force exerted on a sample;DL: is the change in length of the sample; Ao: is the original cross-sectional area of the sample and Li: is the original sample length [14].
Fig 3. Optical microscope micrographs of (PVA/Starch) blend films.
Please cite this article as: B. H. Musa and N. J. Hameed, Study of the mechanical properties of polyvinyl alcohol/starch blends, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.161
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B.H. Musa, N.J. Hameed / Materials Today: Proceedings xxx (xxxx) xxx
Table 1 Tensile properties of PVA/starch blend films. Samples PVA (75% (70% (65% (60% (50%
PVA/25% PVA/30% PVA/35% PVA/40% PVA/50%
% w/w solids St) St) St) St) St)
blend blend blend blend blend
10%
Tensile strength (MPa)
Young’s Modulus(MPa)
(Elongation) (%)
60.5 60.08 53.98 51.98 42.64 35.97
16.7 32.99 23.68 34.76 30.76 37.87
153.99 5.48 4.046 2.65 2.36 1.14
2.3.4. Optical microscope The morphology of PVA, PVA /St blend films was investigated by using an optical microscope of MEIJI TECHNO CO., LTD, model: MT9430 made in Japan with magnification 10X.
sion between the two components. As a result, the tensile strength decreases [14,17]. Table 1 shows mechanical properties (elongation (% E), tensile strength (TS) and Young’s modulus (Y) of PVA/St blend films under tension tests.
3. Results and discussion
4. Conclusions
Fig. 1 indicates depicts the relation between stress and strain under tensile test. It was shown that the tensile strength and elongation decreased with increase in corn starch contents. However, Young’s modulus increased with increase of starch contents. Fig. 2(a) shows the addition of starch to PVA causing a decrease in tensile strength due to the decrease in hydrogen bonding density in the polymer and hard segment contents. This result was in agreement with (Hameed& Abd-alrhman 2018) [11]. Also, the cross sectional area of the PVA decreased with the increase of corn starch content and this effect can be attributed to the amorphous nature of starch that raised the brittleness, which led to reduction in the tensile strength of the film. This work was similar to (Tang et al., 2008) [15]. The results proved that the highest tensile strength value of the films was (60.08 MPa) at 75/25 wt/wt% of the PVA/starch blend. In Fig. 2(b) it can be observed that the elongation at break decreases with increase of the starch, while the PVA concentration had the maximum percentage of elongation value (153.99%) compared with other blends. This is because PVA experiences a great plastic deformation, while the PVA/ starch films undergo slighter plastic deformation. This was related to the stress exerted cannot be transferred equally to the PVA matrix. So, the stress which was exerted will be concentrated on the voids which are full of the starch particles and also the agglomerated starch particles. These results were similar to (Guohua et al. 2006) who found that the percentage of elongation decreased with a starch content increase [16]. It can be seen from Fig. 2(c), the Young modulus increased with increasing starch amount. The highest modulus of elasticity was found at 50/50 wt/wt% of PVA/ corn starch blend with the value of 37.87 MPa. The enhancement of modulus of elasticity was related to stiff starch particles that are embedded in the PVA matrix and the variation in the feature of the polymer compound (Kocsis & Fakirov, 2009) [17]. These results also were in agreement with prior work by (Yee et al. 2011) [18]. Nevertheless, it shows that the Young’s modulus decreases in samples of 30 and 40 wt% of starch content. Young’s modulus is inversely proportional withelongation. In Fig. 3, it is observed from the optical microscope that a smooth surface of the PVA matrix and a regular distribution of the starch particles were achieved in the blend film with (0, 25, 30 wt%) of the starch. Extra increase in starch content led to agglomeration then it caused formation of voids in the polymer matrix. These voids and agglomeration led to poor interfacial adhe-
The results revealed that the addition of starch to plastic PVA phase led to: 1. A significant decrease in elongation and tensile strength, while Young’s modulus was increased due to the brittle nature of starch. 2. It was also observed from optical microscope, that a good image of the starch particle distribution was obtained for the blend films up to 30 wt% of starch. However, agglomerates can be seen in the blend films with 35, 40, 50 wt% of starch content. 3. PVA/starch blends were studied to be used in drug delivery applications.
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Please cite this article as: B. H. Musa and N. J. Hameed, Study of the mechanical properties of polyvinyl alcohol/starch blends, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.161