Mechanical and antibacterial properties of modified nano‐ZnO/high‐density polyethylene composite films with a low doped content of nano‐ZnO

Nano‐ZnO/high‐density polyethylene (HDPE) composite films were prepared via melt blending and a hot compression‐molding process. The properties, including ultraviolet absorption, mechanical and antibacterial properties of the films, and plasticizing behavior of the composites, were investigated. The results show that the absorbance in the ultraviolet region of the HDPE films was enhanced after the addition of modified nano‐ZnO to the HDPE matrix. Also, we found that improvement in the HDPE films of the tensile strength and elongation at break was achieved by the incorporation of modified ZnO nanoparticles up to 0.5 wt % in contrast with the original nano‐ZnO/HDPE composite films. Antibacterial testing was carried out via plate counting, and the results indicate that the HDPE films doped with modified ZnO nanoparticles showed favorable antibacterial activity, especially for Staphylococcus aureus. However, the low doped content of modified nano‐ZnO in the HDPE matrix made the balance torque of the composites increase slightly. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Porous poly(L‐lactic acid)/poly(ethylene glycol) blend films

Poly(L ‐lactic acid) (PLLA: M_w = 19.4 × 10⁴)/poly(ethylene glycol) (PEG: M_w = 400) blend films were formed by use of a solvent‐cast technique. The properties and structures of these blend films were investigated. The Young's modulus of the PLLA decreased from 1220 to 417 MPa with the addition of PEG 5 wt %, but the elongation at break increased from 19 to 126%. The melting point of PLLA linearly decreased with increases in the PEG content (i.e., pure PLLA: 172.5°C, PLLA/PEG = 60/40 wt %: 159.6°C). The PEG 20 wt % blend film had a porous structure. The pore diameter was 3–5 μm. The alkali hydrolysis rate of this blend film was accelerated due to its porous structure. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 965–970, 2004     

Impact of the starch source on the physicochemical properties and biodegradability of different starch‐based films

Concern about environmental issues has motivated research into the development of biodegradable packaging from renewable sources. Natural polymers such as starch constitute a good alternative for diminishing the use of nonbiodegradable and nonrenewable components in the packaging industry. However, depending on the botanical source, films with different properties are formed. The aim of this study was to evaluate the film‐forming capacity of different starch sources (cassava, corn, potato, and wheat) by casting with starch contents from 2 to 6%. Principal component analysis methodology was used to evaluate the correlation between the formulations and their physicochemical and mechanical properties. It was not possible to produce continuous films based on potato starch, probably because of its very low amylose content (10%). The corn‐, cassava‐, and wheat‐starch‐based films were characterized by their thicknesses (0.06–0.22 mm), moisture contents (19–26%), water solubilities (13.7–26.5%), water‐vapor permeabilities (WVPs; 0.19–0.48 g mm h^?1 m^?2 kPa^?1), wettabilities (35–106°), biodegradabilities in soil, and thermal and mechanical properties (tensile strength = 1.9–6.7 MPa, elongation = 41–166%, and Young's modulus = 8–127 MPa). The wheat starch films presented higher WVPs and lower mechanical properties. The cassava starch films presented lower wettabilities and good mechanical properties; this suggested that their use in packaging for products, such as fruits and vegetables, with higher water activities could be feasible. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46564.     

Thermal and mechanical characterization of films based on poly(vinyl alcohol) and β‐lactoglobulin blends

In this study, we investigated the possibility of creating easy to handle films based on poly(vinyl alcohol) (PVA) and β‐lactoglobulin (βlg) blends using the casting method. Four different variables were studied to obtain these films: different proportions of PVA and βlg, different pHs (10, 7, 5.5, and 2.5), several molecular masses of PVA (130,000, 13,000–23,000, and 2000 g/mol), and the denaturation of βlg. The first objective was to obtain films, and the second was to characterize them by differential scanning calorimetry, thermogravimetric analysis, and mechanical testing. Significant variations in behavior were found, and the variables studied modified the blends in different ways. In particular, better results were achieved when the βlg proportion was less than 30 wt %, and when a pH of 2.5 was used in conjunction with a high molecular mass (130,000 g/mol) of PVA. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41745.     

Study of silane treatment on poly‐lactic acid(PLA)/sepiolite nanocomposite thin films

Poly‐lactic acid (PLA) nanocomposite film was prepared with untreated and silane treated sepiolite through solution casting method. Sepiolite is found to be promising nano inorganic filler used to prepare biodegradable PLA nanocomposite films. The effect of sepiolite loading on the thermal, mechanical, gas permeability, and water vapor permeability (WVP) properties of the films was investigated. X‐ray diffraction analysis revealed the crystallinity index and well dispersed sepiolite in PLA/sepiolite thin films. By modifying sepiolite, depending on the nanoclay content, the mechanical properties of films were enhanced. PLA/sepiolite films exhibited improved gas barrier and WVP properties compared to neat PLA. The scanning electron microscope results demonstrated that there is a good interface interaction between sepiolite and PLA. The surface treatment of sepiolite increased the adhesion of the PLA matrix to the sepiolite nanoclay which yielded better mechanical properties of the films as compared to pure PLA. It was observed after 1.5% wt sepiolite, nano‐filler tended to agglomerate, therefore mechanical and barrier properties of films decreased. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41428.     

Effects of co‐plasticization of acetyl tributyl citrate and glycerol on the properties of starch/PVA films

Starch/polyvinyl alcohol (PVA) nanocomposite films by film blowing process were successfully obtained. Starch (1700 g), PVA (300 g), and organically modified montmorillonite (OMMT, 200 g) were blended and plasticized with acetyl tributyl citrate (ATBC) and glycerol (GLY) at weight ratios of 0/100, 5/95, 10/90, 15/85, 20/80, and 25/75. The structural, morphology, barrier, mechanical, and thermal properties of the films, as well as molecular interactions in the nanocomposites were analyzed. The 3.98 nm d‐spacing was the highest in starch/PVA nanocomposite films plasticized with ATBC/GLY ratio of 10/90. The film with ATBC/GLY (5/95) had the lowest WVP (3.01 × 10^?10 g m^?1 s^?1 Pa^?1). The longitudinal tensile strength (TS) of starch/PVA nanocomposite films gradually increased from 4.46 to 6.81 MPa with the increase of ATBC/GLY ratios. The T_g steadily increased from 49.2°C to 55.2°C and the ΔH of the nanocomposite films decreased from 81.77 to 51.43 J/g at the presence of ATBC. The addition of ATBC into GLY plasticized starch/PVA/OMMT system enhanced the intermolecular interaction in the nanocomposites. This study proved that ATBC was an excellent compatibilizer in the preparation of starch/PVA/OMMT nanocomposite films. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42544.     

Effect of blend composition and structure on biodegradation of starch/ecoflex‐filled polyethylene films

A method to blend starches and polyethylene, and thus improve the environmental footprint, was investigated. Unlike traditional methods that utilize compatibilizers or rely on reactive extrusion to achieve the desired material compatibility, a high amylose starch, such as Gelose 80, was mixed with native starch, converted to thermoplastic starch, and compounded with Ecoflex and polyethylene. Films showed good integrity and were evaluated for mechanical properties, anaerobic biodegradability, and structure changes both before and after anaerobic sludge digestion. Mechanical properties were sufficient that these films might be utilized in a number of applications but were not recommended as a sustainable solution. Biodegradation was below the theoretical maximum, was not a linear function of the amount of biodegradable materials incorporated in the films, and was depressed further as the proportion of polyethylene increased due to an encapsulation effect. Structural evaluation showed the components of the blends remained as separate phases and the structure of the Gelose 80 was reminiscent of interphase material. Biodegradation yield appeared to be principally driven by connectivity of the starches within the films to the anaerobic sludge digestion environment. Recommendations for additional studies were given. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Photobiodegradation of low‐density polyethylene/banana starch films

The effects of the starch content, photosensitizer content, and compatibilizer on the photobiodegradability of low‐density polyethylene (LDPE) and banana starch polymer blend films were investigated. The compatibilizer and photosensitizer used in the films were PE‐graft‐maleic anhydride (PE‐g‐MA) and benzophenone, respectively. Dried banana starch at 0–20% (w/w) of LDPE, benzophenone at 0–1% (w/w) of LDPE, and PE‐g‐MA at 10% (w/w) of banana starch were added to LDPE. The photodegradation of the blend films was performed with outdoor exposure. The progress of the photodegradation was followed by determining the carbonyl index derived from Fourier transform IR measurements and the changes in tensile properties. Biodegradation of the blend films was investigated by a soil burial test. The biodegradation process was followed by measuring the changes in the physical appearance, weight loss, and tensile properties of the films. The results showed that both photo‐ and biodegradation rates increased with increasing amounts of banana starch, whereas the tensile properties of the films decreased. The blends with higher amounts of benzophenone showed higher rates of photodegradation, although their biodegradation rates were reduced with an increase in benzophenone content. The addition of PE‐g‐MA into polymer blends led to an increase in the tensile properties whereas the photobiodegradation was slightly decreased compared to the films without PE‐g‐MA. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2725–2736, 2006     

Laboratory antimicrobial activity of cinnamaldehyde and pomegranate‐based polycaprolactone films

Polycaprolactone (PCL) was incorporated separately with cinnamaldehyde (CNMA), pomegranate methanolic extract (PME), freeze dried arils of pomegranate (FDAP), and seed flour of pomegranate (SF) to form antimicrobial films to be used for active food packaging. PCL–CNMA films completely inactivated growth of the artificially inoculated Escherichia coli and Staphylococcus aureus, whether at 5% or 10% concentrations (wt/wt of polymer), at all studied temperatures (4, 20, and 37 °C). PCL–PME films (10% wt/wt of polymer) delayed the growth of E. coli and S. aureus for up to 7 and 6 days, respectively, at 37 °C. Two‐day delays in the growth of both bacteria were achieved with FDAP and SF films (10% wt/wt of polymer) at 20 °C. The release of CNMA was slower than the release of PME during film processing, as measured by Fourier transform infrared spectroscopy. Thus, CNMA and pomegranate‐based films perhaps should be planned further for use in controlled release food packaging. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45347.     

Thermal oxidation of self‐degradable composite films based on low‐density polyethylene

The effect of the structure of composite extrusion films based on a mechanical blend of low‐density polyethylene and poly(hydroxybutyrate) on the service characteristics and the kinetics of thermooxidative destruction was investigated. The aggregate state of the polymers affected the value of the boundary surface in the blend films. An increase in the latter affected the conformation states of both polymers in the blends. In this case, the strength decreased, the steam permeability increased, and the thermooxidative destruction of the polyethylene matrix during the beginning stages was accelerated. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1392–1396, 2004     

Effect of starch predrying on the mechanical properties of starch/poly(ε‐caprolactone) composites

This study describes the effect of predrying sago starch, a tropical starch, on the resultant mechanical properties of starch/poly(ε‐caprolactone) composite materials. Sago starch was dried to less than a 1% moisture level in a vacuum oven and dispersed into a polycaprolactone matrix with an internal mixer at 90°C. The mechanical properties of the composite were studied according to methods of the Association for Standards, Testing, and Measurement, whereas the morphology was monitored with scanning electron microscopy. The properties were compared with a composite obtained with native starch containing 12% moisture. The results indicated that predrying the starch led to a lower property drop rate in the composite as the starch content increased. The elastic modulus, tensile strength, and elongation at break were higher than those obtained when starch was used without predrying. The morphology observed during scanning electron microscopy studies was used to explain the observed trends in the mechanical properties. In this way, a relatively simple and cost‐effective method was devised to increase the starch loading in the polycaprolactone matrix to obtain properties within the useful range of mechanical properties. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 877–884, 2003     

Effects of the moisture and fiber content on the mechanical properties of biodegradable polymer–sisal fiber biocomposites

The matrix of the composites that were used in this work was a commercial blend based on starch and cellulose derivatives. The biodegradable polymer was reinforced by short‐sisal fibers with a range in fiber content of 5–15 wt %. The effects of humidity on the diffusion coefficients, equilibrium moisture content, and mechanical properties were studied. Equations obtained from microscopic mass balances for diffusion in solids were used to predict the absorbed humidity in both components (the sisal fibers and biodegradable polymer) and in the composites as a function of time. Different model predictions of the composite diffusion coefficients as a function of the filler concentration were also examined, and they were found to be in agreement with the experimental results. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 4007–4016, 2004     

Preparation and characterization of isotactic polypropylene/high‐density polyethylene/carbon black conductive films with strain‐sensing behavior

Novel conductive films with a unique strain (ε)‐sensing behavior and based on a blend of isotactic polypropylene (iPP), high‐density polyethylene (HDPE), and carbon black (CB) were fabricated by an extrusion casting method. The morphology and ε‐sensing behavior of the films were investigated. Scanning electron microscope images showed that the oriented lamellae with a growing direction perpendicular to the extrusion direction were obtained in the HDPE phase and were accompanied by a cocontinuous structure of the iPP phase and HDPE/CB phase. The conductive percolation threshold (m_c) and resistivity–ε behavior of the thin films are affected by the drawing ratio during the process of film preparation. The m_c and electrical resistance of the iPP/HDPE/CB composite films increased with the drawing ratio. The gauge factor of the films within the elastic region decreased with increasing drawing ratio. Furthermore, the result of iPP/(HDPE/CB) 40/60 with a high drawing ratio shows that a reversible conductivity was obtained during the cyclic tensile testing (ε = 10%), but an irreversible conductivity makes the film fail during use at the applied ε values of up to 15%. This makes them good piezoresistive candidates for ε‐sensing materials. Moreover, a simple structural model was proposed to describe the reversible and irreversible phenomena in the electrical resistance behavior of the iPP/HDPE/CB films under tensile loading. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40686.     

Study on poly(butylene adipate‐co‐terephthalate)/starch composites with polymeric methylenediphenyl diisocyanate

To lower the cost of poly(butylene adipate‐co‐terephthalate) or PBAT, starch was used as a filler in this study. To increase tensile strength of PBAT/starch composites, polymeric methylenediphenyl diisocyanate (pMDI) was used as a compatibilizer. PBAT was melt‐mixed with starch in a kneader, and then the mixtures were compression‐molded. The effects of starch and pMDI content on the tensile strength and elongation at break of PBAT/starch composites were examined. The morphology and biodegradability of the composites in soil were also studied. The tensile strength of PBAT and PBAT/starch composites increases with increasing content of pMDI. The increase of weight average molecular weight of PBAT and improved interaction between PBAT and starch were observed with increasing content of pMDI. The weight average molecular weights of buried PBAT and the composites in soil significantly decrease. Especially, the reduction of the weight average molecular weight of PBAT/starch (70/30) composite is the most significant. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41884.     

Physical and antimicrobial properties of quinoa flour‐based films incorporated with essential oil

Films of quinoa flour (Chenopodium quinoa, W) incorporated with oregano (Origanum vulgare L.) and thyme (Thymus vulgaris L.) essential oils (EOs) at 0.5%, 1%, and 2% p/p were prepared to examine their physical and mechanical properties and antimicrobial activity against Escherichia coli and Staphylococcus aureus. The type of EO was not significant for the physical and barrier parameters of the films. The increase in the EOs concentration led to an increase in the elongation at break, but decrease in the tensile strength, Young's modulus, solubility and water vapor permeability. Films containing 1% and 2% EOs exhibited an inhibitory effect on the growth of S. aureus and E. coli. However, S. aureus was more sensitive to both EOs and the oregano was more efficient in the inactivation to both microorganisms. The incorporation of EOs as natural antibacterial agents may lead to their potential application as active packaging materials to increase food safety. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43311.     

Blends of poly(d,l‐lactide) with polyhedral oligomeric silsesquioxanes‐based biodegradable polyester: Synthesis,morphology, miscibility,and mechanical property

A highly branched hybrid copolymer based on polyhedral oligomeric silsesquioxane (POSS) was designed to improve the brittleness of poly(d,l‐lactide) (PDLLA). The toughening material was synthesized using POSS‐OH as the core, which initiated the ring‐opening polymerization of ε‐caprolactone and d,l‐lactide sequentially to form the highly branched POSS‐g‐poly (ε‐caprolactone)‐b‐poly(d,l‐lactide) (POSS‐g‐PCL‐b‐PLA) copolymer with eight PCL‐b‐PLA arms. The POSS‐g‐PCL‐b‐PLA copolymer had a very good dispersion in the PDLLA matrix with the size of microdomains smaller than 1 µm when added at a low content below 10 wt %. In related to the nano‐scale size of microdomains in the blends, the crystallinity of PCL blocks was significantly suppressed. Thus, the addition of POSS‐g‐PCL‐b‐PLA is very effective to improve the roughness of the matrix polymer when added at a low content. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40776.     

Biodegradation of poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) by a novel P3/4HB depolymerase purified from Agrobacterium sp. DSGZ

A poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) (P3/4HB)‐degrading strain, Agrobacterium sp. DSGZ, was isolated from sewage by poly(3‐hydroxybutyrate) (PHB) mineral agar plates. A novel P3/4HB depolymerase with a molecular weight of 34 kDa was purified through a novel single‐step affinity chromatography method from the culture supernatant of the strain by using P3/4HB powder as a substrate. The purified depolymerase showed optimum activity at pH 7.0 and 50°C, and was stable at the pH range of 6.0 to 9.0 and temperature below 50°C. Enzyme activity was strongly inhibited by phenylmethylsulfonyl fluoride (PMSF), ethylenediaminetetraacetic acid (EDTA), hydrophobic reagents, and some metal ions. The depolymerase degraded poly(3‐hydroxybutyrate) (PHB), poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV), P3/4HB, and polycaprolactone (PCL), instead of polylactic acid (PLA) or poly(butylene succinate) (PBS). Meanwhile, the depolymerase showed high hydrolytic activity against short‐chain length esters, such as butyrate acid ester and caprylic acid ester. The main degradation products of the depolymerase were identified as hydroxybutyrate monomers and dimers, and the monomers were identified as 3‐hydroxybutyrate (3HB) monomers and 4‐hydroxybutyrate (4HB) monomers. The preparation procedure, crystallinity, and 4HB composition of the P3/4HB copolymer showed evident effect on degradation behavior, and change in crystallinity was the main factor affecting degradation. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42805.     

Moisture‐sorption characteristics of starch/low‐density polyethylene films

Moisture‐sorption characteristics of starch/low‐density polyethylene (LDPE) blends were carried out at 27°C for water activity (a_w) from 0.1 to 0.9. The sorption data were used to fit six different sorption isotherm models proposed in the literature. The model constants were determined by linear fitting of the sorption equations. The ranges of applicability of water activity for the isotherm models reported in the article lies between 0.1 and 0.4 (monomolecular layer) for the BET model and between 0.3 and 0.9 (multimolecular and capillary condensation layers) for other models. The value of the coefficient of determination (R² = 0.97 ± 0.02) confirms the linear fitting of the equations studied. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1193–1202, 2002; DOI 10.1002/app.10417     

Radiation‐assisted morphology modification of LDPE/TPS blends: A study on starch degradation‐processing‐morphology correlation

Potato starch was radiolytically degraded to different extents by irradiating with Co‐60 gamma radiation in wide dose range. The degraded starch was plasticized using glycerol and water to obtain radiation processed thermoplastic starch (RTPS). Blends of different RTPS and low density polyethylene (LDPE) were prepared by internal melt mixing. Characterization of blends using differential scanning calorimetry, thermogravimetric analysis, X‐ray diffraction, Fourier transformed infrared spectroscopy, scanning electron microscope, melt flow, contact angle, and soil burial studies indicated changes in the blend morphology and biodegradation behavior with the increase in the dose imparted to the starch fraction. Molecular weight of starch decreased substantially in the dose range of the study. The melt viscosity of LDPE/RTPS blend decreased whereas crystallinity of LDPE phase increased with the incorporation of RTPS. No significant change in the carbonyl index and thermal stability of the blends was observed in the dose range studied; therefore, the observed changes in the physical and thermal properties of the blends were attributed primarily to the kinetic factors affecting crystallization and time‐dependent phase separation process. Biodegradability of blends varied with the radiation dose imparted to starch component of blend, suggesting better encapsulation of RTPS by LDPE chains. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

环氧改性聚酰胺对淀粉基生物降解复合膜性能的影响

将环氧改性聚酰胺(EPA)与热塑性玉米淀粉复合后采用浇铸法制备出新型增强生物降解复合膜,研究了EPA对复合膜结晶性能、交联程度、力学性能以及生物降解性能的影响。结果表明,玉米淀粉与EPA、烷基烯酮二聚体及丙三醇复合后,结晶程度明显下降。当EPA质量分数为21 62%时,复合膜的交联度高达45 77%,且复合膜残留物中非EPA成分的质量分数也达到24 15%;复合膜的干态拉伸强度和断裂伸长率分别可以高于12 0MPa和45 0%,湿态拉伸强度和断裂伸长率则分别可以达到5 40MPa和30 0%以上。EPA的添加降低了复合膜的生物降解性能。