Evaluation of photodegradation in LDPE/modified starch blends

Ferreira, Flávia Gonçalves Domingues; Lima, Maria Alice G.A.; Almeida, Yêda Medeiros Bastos de; Vinhas, Glória Maria

doi:10.1590/s0104-14282009000400011

Cited by 12 publications

(7 citation statements)

References 18 publications

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“…As it can be observed, after 24 h irradiation elongation at break decreased significantly, reaching a reduction of around 95%. Ferreira et al [32] stressed that the reduction of elongation at break is a typical behavior of semi-crystalline polymer exposed to radiation that induces reactions with chains breakage, resulting in a more fragile material. Fragility of irradiated samples is in accordance with defects observed by SEM (Figs.…”

Section: Mechanical Propertiesmentioning

confidence: 99%

Oxidative Degradation of Thermoplastic Starch Induced by UV Radiation

Quispe¹,

López²,

Villar³

2019

Journal of Renewable Materials

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Among biopolymers, thermoplastic starch (TPS) is a good candidate to obtain biomaterials because of its natural origin, biodegradable character, and processability. Exposure to ultraviolet (UV) radiation causes significant degradation of starch-based materials, inducing photooxidative reactions which result in breaking of polymer chains, production of free radical, and reduction of molar mass. These changes produce a deterioration of TPS mechanical properties, leading to useless materials after an unpredictable time. In this work, changes induced on TPS by UV radiation, analyzing structural properties and mechanical behavior, are studied. TPS was obtained through thermo-mechanical processing of native corn starch in the presence of water (45 % w/w) and glycerol (30 % w/w) as plasticizers. Films were obtained by thermocompression and, before testing, specimens were conditioned to reduce material fragility. Photodegradation process was performed by exposing TPS to 264 h UV radiation in a weathering test chamber. Specimen's weight loss was determined gravimetrically. Chemical changes were studied by Fourier Transform Infrared Spectroscopy (FTIR) and morphological modifications were analyzed by Scanning Electron Microscopy (SEM). Reduction of weight average molar mass was measured by Static Light Scattering (SLS). Changes in mechanical properties were studied from tensile tests. After 96 h exposure, TPS specimens presented a weight reduction of 4-6%, mainly attributed to plasticizers lost by evaporation. SEM observations showed that UV radiation induced morphological changes on TPS, evidenced by an increment of specimens cracking. By FTIR, it was detected the presence of an additional band located at 1726 cm -1 in samples submitted to UV radiation, attributed to the formation of -C=O groups. Weight average molar mass of native starch was in the order of 107 g mol -1 . TPS exposure to UV radiation decreased significantly its molar mass, confirming molecular degradation of the biopolymer. When TPS was exposed during 48 h, it was detected a considerable decrease in elongation at break values (~ 85%), indicating that TPS flexibility was reduced. On the other hand, after 48 h exposure, TPS elastic modulus was 55 times higher than those of the unexposed specimens, evidencing an increase in material rigidity. TPS maximum tensile strength was also increased by UV light, with an increment of ~ 400% after 48 h exposure. Results revealed that starch-based materials can be degraded by exposure to UV radiation, modifying their microstructure and mechanical performance.

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Section: Mechanical Propertiesmentioning

confidence: 99%

Oxidative Degradation of Thermoplastic Starch Induced by UV Radiation

Quispe¹,

López²,

Villar³

2019

Journal of Renewable Materials

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“…Griffin introduced an idea of incorporating biodegradable starch into nondegradable plastics such as PE, polypropylene (PP), poly(ethylene terephthalate) (PET), and polystyrene (PS) 2. In recent years, several efforts have been made to incorporate starch into thermoplastic 3–7. Starch is polysaccharide‐based materials, which is renewable and biodegradable.…”

Section: Introductionmentioning

confidence: 99%

Effect of the electron beam irradiation on the properties of epoxidized natural rubber (ENR 50) compatibilized linear low‐density polyethylene/soya powder blends

Sam

Ismail

Ahmad

et al. 2011

J of Applied Polymer Sci

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Linear low-density polyethylene/soya powder blends were prepared by using an internal mixer at 150 C. The soya powder content ranged from 5 to 40 wt %. Epoxidized natural rubber with 50 mol % epoxidation (ENR 50) was added as a compatibilizer. The blends were irradiated by electron beam (EB) at a constant dose of 30 kGy. The changes in gel fraction, tensile properties, morphological and thermal properties of the samples were investigated. The gel content increased after EB irradiation. However, the increment of gel content was hindered by increasing soya powder content. The tensile strength and Young's modulus of the blends were increased by EB whereas the elongation at break decreased. The tensile frac-ture surface also support the reduction of elongation at break by EB irradiation. Further analysis on the irradiated blends using Fourier transform infrared spectra indicated an increase of oxygenated product after undergoing EB irradiation. The differential scanning calorimetry result indicated that the melting temperature of the blends decreased after EB irradiation whereas the crystallinity increased. EB irradiation also enhanced the thermal stability of the blends as indicated by thermogravimetric analysis. V C 2011 Wiley Periodicals, Inc. J Appl Polym Sci 124: 5220-5228, 2012

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“…A reduction in elongation has also been observed in many photodegraded materials. 65,66 Ferreira et al 67 emphasized that elongation reduction is typical behavior of semicrystalline polymers exposed to radiation, since it induces reactions with chain breaks, resulting in a more fragile material. The lower elongation of the films can also be explained by the reduction of the water content over time, as explained in the mass loss, as water also acts as a plasticizer.…”

Section: Mass Lossmentioning

confidence: 99%

“…8 Cui et al 60 considered the increase in rigidity as a consequence of post-induced UV-A crosslinking. According to Ferreira et al, 67 crosslinking reactions between the chains might occur together with cleavage reactions due to photochemical degradation, promoting some stability in the mechanical properties.…”

Section: Mass Lossmentioning

confidence: 99%

Development and characterization of starch‐based films added ora‐pro‐nobis mucilage and study of biodegradation and photodegradation

Oliveira

Silva

et al. 2022

J of Applied Polymer Sci

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Ora‐pro‐nobis mucilage (MOPN) was incorporated into starch films to improve their mechanical, chemical, and retrogradation properties. Films were made in four MOPN content (0%, 10%, 20%, and 30%) by casting. Films with added MOPN presented antioxidant capacity varying from 3.9% to 23.3%. Chemical cross‐links between starch and MOPN were observed in Fourier transform infrared spectroscopy (FTIR) spectrum, resulting in a reinforced network with the greater young modulus (0.02 Pa, control‐film, to 2.20 Pa, 30%‐MOPN), higher tensile strength (1.34 Pa, control‐film, to 4.38 Pa, 30%‐MOPN), and reduction in elongation (250.32%, control‐film, to 6.55%, 30%‐MOPN). Water vapor permeability did not differ statistically between films. In assays photodegradation, higher MOPN content exhibited less shrinkage of films over time and more loss mass in films during 28 days. FTIR spectrum showed that the films increased crystalline regions during storage, which resulted in stronger aggregation between aligned helices. In addition, water molecules were released which allowed a better alignment of the starch chains. Starch‐based films added MOPN can alternatively be used as active biodegradable packaging since it is able to form cohesive, flexible films and with antioxidant action. Furthermore, MOPN, especially 30% addition, reduces drastic changes in mechanical properties over time.

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Evaluation of photodegradation in LDPE/modified starch blends

Cited by 12 publications

References 18 publications

Oxidative Degradation of Thermoplastic Starch Induced by UV Radiation

Oxidative Degradation of Thermoplastic Starch Induced by UV Radiation

Effect of the electron beam irradiation on the properties of epoxidized natural rubber (ENR 50) compatibilized linear low‐density polyethylene/soya powder blends

Development and characterization of starch‐based films added ora‐pro‐nobis mucilage and study of biodegradation and photodegradation

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