Biodegradation and thermal properties of crosslinked chitosan/corn cob biocomposite films by electron beam irradiation

Thermal and biodegradation properties of chitosan (CS)/corn cob (CC) biocomposite films and their irradiation‐crosslinked were tested. The CS/CC biocomposite films after irradiation showed better thermal stability and lower weight loss in enzymatic and soil biodegradation in comparison with unirradiated CS/CC biocomposite films due to the formation of new bonds (radiation‐induced crosslinks). The surface erosion for biodegraded biocomposite films were examined by scanning electron microscope. Furthermore, the formation of new bonds in irradiated biocomposite films were analyzed by Fourier transform infrared spectroscopy. POLYM. ENG. SCI., 59:E59–E68, 2019. © 2018 Society of Plastics Engineers     

Physicochemical characterization of poly(ethylene glycol) plasticized poly(methyl vinyl ether‐co‐maleic acid) films

The influence of the poly(ethylene glycol) (PEG) plasticizer content and molecular weight on the physicochemical properties of films cast from aqueous blends of poly(methyl vinyl ether‐co‐maleic acid) (PMVE/MA) was investigated with tensile mechanical testing, thermal analysis, and attenuated total reflectance/Fourier transform infrared spectroscopy. Unplasticized films and those containing high copolymer contents were very difficult to handle and proved difficult to test. PEG with a molecular weight of 200 Da was the most efficient plasticizer. However, films cast from aqueous blends containing 10% (w/w) PMVE/MA and either PEG 1000 or PEG 10,000 when the copolymer/plasticizer ratio was 4 : 3 and those cast from aqueous blends containing 15% (w/w) PMVE/MA and either PEG 1000 or PEG 10,000 when the copolymer/plasticizer ratio was 2 : 1 possessed mechanical properties most closely mimicking those of a formulation we have used clinically in photodynamic therapy. Importantly, we found previously that films cast from aqueous blends containing 10% (w/w) PMVE/MA performed rather poorly in the clinical setting, where uptake of moisture from patients' skin led to reversion of the formulation to a thick gel. Consequently, we are now investigating films cast from aqueous blends containing 15% (w/w) PMVE/MA and either PEG 1000 or PEG 10,000, where the copolymer/plasticizer ratio is 2 : 1, as possible Food and Drug Administration approved replacements for our current formulation, which must currently be used only on a named patient basis as its plasticizer, tripropylene glycol methyl ether, is not currently available in pharmaceutical grade. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Structural changes of starch/polyvinyl alcohol biocomposite films reinforced with microcrystalline cellulose due to biodegradation in simulated aerobic compost environment

Starch/Polyvinyl alcohol (PVA) based biocomposite films reinforced with micro crystalline cellulose (MCC) (10 wt %) particles were prepared by solution casting method, incorporating glycerol as plasticizer. These biocomposite films were subjected to biodegradation at ambient temperature in a simulated aerobic compost pit. The extent of biodegradation of these films was studied in terms of weight loss. The corresponding changes in the structure of the films were observed using scanning electron microscopy, X‐Ray diffraction study, and differential scanning calorimetry. The melting point of PVA component of the biocomposite film shifted from 204 to 223°C with increase in biodegradation time and a remarkable difference was observed in their melt crystallization behavior. The unreinforced films also showed a similar trend, but the increase in the crystallinity of PVA was more pronounced in MCC reinforced films than that observed in the unreinforced ones. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Surface hydrophobization of CNF films by roll-to-roll HMDSO plasma deposition

Cellulosic films are typically sensitive towards moisture which limits their industrial applicability. In this study the films made from cellulose nanofibrils (CNF) were surface silylated with hexamethyldisiloxane (HMDSO) by roll-to-roll plasma deposition. The effects on surface hydrophobicity were clear and indisputable. Water contact angles of non-modified and plasma-deposited CNF films were 23° and 103°, respectively. As a result of surface silylation the relative polarity decreased from 46.8% to 0.6%. Surface hydrophobicity correlated well with the plasma deposition line speeds (0.5, 5, and 10 m/min) and the water vapor barrier properties. Silylation also decreased the oxygen transmission rates both at 50% and 80% relative humidity as compared to non-modified CNF films. All films were completely impermeable to olive oil and intact in contact with castor oil, toluene, and n-heptane or mixtures of them. The developed surface hydrophobization method can be exploited in strengthening the position of cellulosic films in high performance film applications.     

Films of chitosan and N‐carboxymethylchitosan. Part II: effect of plasticizers on their physiochemical properties

Chitosan (Ch) and N‐carboxymethylchitosan (N‐CMCh) films were prepared by the casting method at concentrations of 1% and 2% of polymer, with or without plasticizer: polyethylene glycol (PEG‐400) and glycerol (G), at 15% (w/w). The influence of composition on mechanical properties, water vapour transmission rate (WVTR), water saturation, and aqueous dissolution of the films was analysed. The thermal stability of the mixture (polymer:plasticizer, 1:1) was evaluated by thermogravimetric analysis (TGA). In general, all the properties were affected by the plasticizers. The plasticized films showed lower strength and a higher percentage of elongation (%E), in the following order: G > PEG‐400 > unplasticized film. The total WVTR increased with Ch concentration, with a different WVTR profile for Ch and N‐CMCh. While the PEG‐400 addition did not significantly modify the WVTR profile of films, the glycerol enhanced the transport of water vapour through both polymers. The plasticizer addition increased the time of water film saturation, in the following order: G > PEG‐400 > unplasticized film; this was more pronounced in the N‐CMCh films, probably due to the formation of hydrogen bonds. The solubility of the films was also affected by their composition. Copyright © 2006 Society of Chemical Industry     

Properties and weldability of plasticized polylactic acid films

The objectives of the presented work were to investigate films based on polylactic acid (PLA) and polyethylene glycol (PEG) in order to improve ductility and weldability of PLA films. The effect of plasticizer amount on the thermal, rheological, and mechanical properties of PLA plasticized films was investigated. The PEG content does affect the glass transition and the cold crystallization temperature of PLA in blends, while the melting temperature was not affected by the addition of PEG. The complex viscosity of the neat PLA granules and of plasticized films showed strong temperature and angular velocity dependence. The Young's modulus and tensile strength of plasticized films were improved with increasing plasticizer concentration, while the elongation at break stays rather constant. Plasticized PLA films were furthermore heat welded. These investigations showed that plasticized PLA films can be welded by heat welding. The obtained weld strength is strongly depending on the PEG amount as well as on selected welding parameters. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40394.     

Use of compatible blends to fabricate carbon black composite vapor detectors

The aim of this work was the development of materials to be used in the field of gas sensing for the detection of organic vapors. Conductive sensors were prepared with carbon black filled blends of poly(vinyl chloride) and diol‐terminated poly(?‐caprolactone), an oligomeric plasticizer. For comparison, blends with di(2‐ethylhexyl)phthalate, a traditional low‐molecular‐weight plasticizer, were also prepared. All sensors were tested upon exposure to different organic vapors. In general, the plasticizer content affected the response rates of the sensors, and a linear variation of the relative resistance with the analyte concentration was observed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1816–1821, 2004     

Investigation of eco-friendly chemical treatments of apple pomace for producing high quality molded pulp biocomposite

Eco-friendly chemical treatments using citric acid (CA) and sodium bicarbonate were employed to remove pectin, hemicellulose, and extractives from apple pomace (AP) for improving AP fiber quality and maximizing its utilization in producing biocomposite boards with newspaper (NP) fibers (AP:NP ratio of 2:1) using molded pulp technique. CA treatment was further optimized at different pH and temperature and cellulose nanofiber (CNF, 0.15, 0.3% w/w pulp solids) was used as reinforcement agent to enhance mechanical property and water resistance of biocomposite boards. CA treatment improved AP fiber strength and cellulose content. AP treated by CA at pH 2.5 and 75°C with 0.15% CNF reinforcement produced AP/NP biocomposite board with high flexural strength, and dimension stability, and low density. Thermal analysis verified increased cellulose content, crystallinity, and thermal stability of CA treated AP fibers. This study provided new insight to improve fiber functionality and utilize AP for developing sustainable packaging.     

Construction of Chlorine Labeled ZnO–Chitosan Loaded Cellulose Nanofibrils Film with Quick Antibacterial Performance and Prominent UV Stability

In this study, novel “green” and highly stable biocidal materials composed of cellulose nanofibrils (CNF) and ZnO–chitosan (ZnO–CS) hybrids are constructed by combing vacuum filtration and heat‐press processing without the use of any organic solvent. CNF/ZnO–CS films are soaked in a 10% sodium hypochlorite aqueous solution to endow antibacterial activity. The chlorinated CNF/ZnO–CS samples and chlorinated CNF/ZnO‐CS (CNF/ZnO‐CS‐Cl) possess quick antimicrobial activity against Staphylococcus aureus and Escherichia coli within 30 min of contact compared with CNF and CNF/ZnO–CS controls. The addition of ZnO endows the films with remarkable UV light stability. After exposure to a UV chamber for 24 h, the chlorine loadings on the prepared samples decrease to 0.13%, where 76% of the chlorine loss can be regained after rechlorination. Furthermore, cytotoxicity evaluations reveal the feasibility of the films for in vitro applications. The prepared rechargeable CNF/ZnO–CS–Cl films will have many promising antibacterial applications.     

Use of zeolite films to improve the selectivity of reactive gas sensors

Semiconductor (Pd-doped SnO₂) gas sensors covered with zeolitic films (MFI or LTA) have been developed and used for gas phase sensing of different species (methane, propane, and ethanol) at different humidity levels. The dynamic responses obtained with these sensors were compared with the response of a reference sensor without a zeolitic layer. The results clearly indicate that a suitable zeolite layer strongly reduces, and in some cases suppresses, the response of the sensor to paraffins, thereby increasing the sensor selectivity to the alcohol, while the reference sensor could not discriminate between these molecules. This clearly shows the potential of zeolite-based sensors to achieve a higher selectivity/sensitivity in gas sensing applications.     

Toward faster degradation for natural fiber reinforced poly(lactic acid) biocomposites by enhancing the hydrolysis-induced surface erosion

The poor and uncontrollable biodegradability of poly(lactic acid) (PLA)-based materials is one of the fundamental limitations for widening their applications. To regulate the degradation of PLA/ramie fiber biocomposites, the hydrophilicity of the composites was modified to attract more water attack by introducing water-soluble poly(ethylene glycol) (PEG). Analyses by characterization of sample size, weight loss and microstructure offered intensive information on the degradation behavior of PLA biocomposites. It was revealed that PEG indeed significantly enhanced the surface erosion process and thus facilitated the degradation rate. The biocomposite bar containing 15 wt% PEG completed degradation within 50 days, while only ~50 wt% mass lost for the control biocomposite sample without PEG. Morphological observation confirmed that PEG accelerated the penetration of outside water from the surface to the center driven by the diffusion-in process, which subsequently boosted the hydrolytic action of the PLA backbone ester groups. Our results indicated that the PEG induced water penetration governed the overall degradation kinetics. As a strong response to the degradation, the stiffness of the biocomposite bars suffered from drastic decrease while T _g varied in a climbing trend within the early stage. Microscopic examination of degradation solution formed during hydrolytic degradation of the PLA biocomposites suggested oligomers or lactic acid monomers were released to the solutions. It was of great interest to observe PEG dissolved in the alkaline solution speeded the ramie fibers breaking down to tiny fragments and cellulose macromolecules which further regenerated into cellulose aggregates in various fantastic appearances like coral-like leaves and pine needles. Our success in regulating the degradation of PLA biocomposites also provides an instructive approach for other PLA based materials.

Effect of BaTiO3 on the sensing properties of PVDF composite-based capacitive humidity sensors

Capacitive humidity sensors consisting of materials such as polymers, ceramics, and piezoelectrics are widely used to monitor relative humidity levels. The effect of barium titanate (BaTiO₃) nanoparticles on the humidity sensing properties, dielectric response, thermal stability, and hydrophilicity of the polyvinylidene fluoride (PVDF)-BaTiO₃ composite films is investigated. Hydrophilicity and surface morphology of the PVDF-BaTiO₃ composite films are modified for the development of a good humidity sensor. The nanocomposite solutions are prepared by mixing an optimized concentration (2.5 wt%) of PVDF with different concentrations (0.5, 1, and 2 wt%) of BaTiO₃ nanoparticles. X-ray diffraction, thermogravimetric analysis, field emission scanning electron microscopy, and contact angle measurements are used to characterize the structure, morphology, thermal stability, and hydrophilicity of the spin-coated sensing films. The dielectric study of PVDF-BaTiO₃ composite film shows that as the concentration of BaTiO₃ particles increase, the dielectric constant of the composite films increases as well. PVDF-BaTiO₃ (2.5 wt%-1 wt%) based capacitive sensors show stable capacitive response and low hysteresis as compared to the other concentrations of the PVDF-BaTiO₃ composites. The maximum hysteresis of the capacitive PVDF-BaTiO₃ (2.5 wt%- 1 wt%) humidity sensor is found to be ~2.5%. The response and recovery times of the PVDF-BaTiO₃ (2.5 wt%-1 wt%) based capacitive sensors are determined as 40 s and 25 s, respectively, which are significantly lower than those reported for the other PVDF composite based sensors.     

Physico-chemical properties of lignin–alginate based films in the presence of different plasticizers

A lignin–alginate blended film was prepared in the presence of three different plasticizers, viz. glycerol, epichlorohydrin (EPC) and poly(ethylene glycol) (PEG) and the effect of each plasticizer was studied on physico-chemical properties of the blended film. Lignin extracted from Acacia wood by alkali extraction process was blended with alginate to obtain lignin–alginate film in the presence of different plasticizers. A film plasticized with glycerol displayed higher solubility and swelling percentage as compared to EPC and PEG plasticized films. The highest tensile strength was observed for film plasticized with PEG, and none of the plasticizers made any significant change on the bursting strength of the film. Incorporation of lignin considerably improved the light barrier properties of the films. Fourier transform infrared spectroscopy study of films suggested the existence of hydrogen bonding between lignin–alginate in the presence of plasticizers. In addition, EPC plasticized film displayed highest thermal stability, as confirmed by thermogravimetric analysis. Further studies demonstrated that plasticizers significantly affected the physico-chemical properties of the blended films. In conclusion, lignin–alginate film plasticized with EPC presented better physico-mechanical and light barrier properties which could be used in packaging and coating applications.     

Properties of linear poly(lactic acid)/polyethylene glycol blends

Poly(lactic acid) (PLA) has great potentials to be processed into films for packaging applications. However, film production is difficult to carry out due to the brittleness and low melt strength of PLA. In this investigation, linear PLA (L‐PLA) was plasticized with poly(ethylene glycol) (PEG) having MW of 1000 g mol^?1 in various PEG concentrations (0, 5, 10, 15, and 20 wt%). In relation to plasticizer content, the impact resistance and crystallinity of L‐PLA was increased, whereas a decrease in glass transition temperature and lower stiffness was observed. Nevertheless, the phase separation has been found in samples which contained PEG greater than 10 wt%. The dynamic and shear rheological studies showed that the plasticized PLA possessed lower viscosity and more pronounced elastic properties than that of pure PLA. Both storage and loss moduli decreased with PEG loading at all frequencies while storage modulus exhibited weak frequency dependence with increasing PEG content. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

HDPE-AA-SSS预辐照接枝膜的表征及其湿敏性能的研究

采用预辐照法将亲水性单体丙烯酸(AA)和对苯乙烯磺酸钠(SSS)接枝到疏水性高密度聚乙烯(HDPE)薄膜上,制备出新型的接枝膜湿敏元件.通过扫描电镜观测了辐照接枝前和接枝后HDPE膜的表面形貌,并通过红外光谱表征了膜的结构,同时测定了接枝膜湿敏元件的湿敏性能.实验结果表明,制备的接枝膜湿敏元件具有良好的湿敏特性,响应和恢复时间短.它具有较好的稳定性,能在高湿、高温环境下使用.实验结果也表明了接枝HDPE膜具有良好的湿敏性能.     

Combination of polymeric substrates and metal–polymer nanocomposites for optical humidity sensors

This paper reports a combination of self-supported, 80-μm-thick polymeric substrates of poly(dimethyl siloxane), poly(methyl methacrylate), poly(vinyl alcohol) (PVA), and poly(N-vinylpyridine) (PVP) and nanocomposites, silver nanoparticle (nAg)/0.1% PVP (S1) and nAg/0.1% PVA (S2), for use in optical-transmission-type humidity sensors. Composites are synthesized by a chemical reduction method at optimum conditions, giving particle sizes of 5–10 nm and 10–20 nm, respectively, for nAg/0.1% PVP and nAg/0.1% PVA. Composite formation is confirmed using Fourier transform infrared spectroscopy (FTIR). The role of polymers in obtaining a smaller Ag particle size is studied using ultraviolet–visible spectroscopy and transmission electron microscopy. The nanocomposite is coated onto substrates either on a single side or on both sides by dip coating. The humidity response of nAg/0.1% PVP-0.1% PVP- nAg/0.1% PVP (S1-PVP-S1) sensors, measured using the direct optical transmission method, exhibits an enhancement in sensitivity [0.88 ± 0.04 (/% RH)] for the humidity range 6–94% RH and response (6 s) and recovery (8 s) times compared to nAg/0.1% PVP-PVP S1-PVP sensors and a linear response (R² ≥ 0.99). An attempt is made to explain the sensing process with the help of FTIR spectra in dry and humid environments. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47035.     

UV‐Printable and Flexible Humidity Sensors Based on Conducting/Insulating Semi‐Interpenetrated Polymer Networks

Humidity sensors are of great interest in many fields because humidity plays a crucial role in several processes. Nevertheless, their application is often limited by the expensive fabrication and the stiffness of the substrates usually employed. In this work, novel UV‐curable and flexible humidity sensors based on semi‐interpenetrated polymer networks are fabricated. They can be prepared either as self‐standing sensors or applied on different bendable substrates. The fabrication consists of a simultaneous UV‐curing of an insulating network (acrylic or epoxy) and photopolymerization of conducting polypyrrole (PPy). The detection mechanism involves proton transfer on the PPy chains that can be macroscopically observed by electrical impedance variations. These devices show promising humidity‐sensing properties from 20 to 97% of relative humidity with a maximum response of about 180%. The dynamic sensing investigation proves that the recovery process can be tailored playing on the glass transition temperature and wettability of the films. The remarkable sensing capabilities of these sensors make them a valid alternative in many applications where printability and flexibility are required along with simple fabrication method consisting of one‐step synthesis.     

Effects of vanillin and plasticizer on properties of chitosan‐methyl cellulose based film

Chitosan‐methyl cellulose based films which incorporatate vanillin as an antimicrobial agent and polyethylene glycol 400 (PEG) as a plasticizer were developed in this study. The effects of vanillin and plasticizer concentration on mechanical, barrier, optical, and thermal properties of chitosan‐methyl cellulose film were evaluated. When the vanillin concentration was increased at a given PEG level, film flexibility decreased while tensile strength increased slightly. Vanillin increased the barrier to oxygen but not water vapor. Increasing vanillin content resulted in less transparency and a more yellowish tint. The bulky nature of vanillin reduced film crystallization. When PEG concentration was increased at a given vanillin level, it resulted in greater film flexibility but reduced film strength. Water vapor permeability (WVP) and oxygen permeability (OP) increased with increase in PEG content. PEG contributed less to the opacity, yellowness, and crystallization of the film than did vanillin. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Plasticization of poly(lactide) with poly(ethylene glycol): Low weight plasticizer vs triblock copolymers. Effect on free volume and barrier properties

In order to make poly(lactide) (PLA) suitable for food packaging applications, its toughness must be improved. In this work, the plasticization effectiveness of a low-molecular-weight plasticizer and a triblock copolymer are analyzed. For this purpose, PLA is blended with poly(ethylene glycol) (PEG) and poly(lactide-ethylene glycol-lactide) (LA-EG-LA) triblock copolymer. The obtained results show that copolymers are more effective, reducing the glass transition temperature of PLA. Although PLA/PEG blends have been widely studied in the literature, the barrier character has not been analyzed, which is of paramount importance for packaging applications. Therefore, the permeability to carbon dioxide, oxygen, and water vapor of PLA/PEG blends has been characterized observing an increase with the incorporation of PEG, which is the expected behavior. However, the incorporation of LA-EG-LA copolymers leads to permeability values that are slightly higher, similar, or even lower than PLA. Furthermore, the free volume of the samples has been analyzed in order to gain a deeper insight on the factors affecting the transport properties. Overall, this works aims to provide a better understanding towards the design of biodegradable packaging with improved properties that could be also extended to other biodegradable polymers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48868.     

Production and characterization of films containing poly(hydroxybutyrate) (PHB) blended with esterified alginate (ALG‐e) and poly(ethylene glycol) (PEG)

Alternative materials have long been studied and developed to replace conventional skin dressings with the emergence of new biopolymers and development of polymeric film fabrication techniques. As a new material for polymeric dressings, films of poly(hydroxybutyrate) (PHB) blended with esterified alginate (ALG‐e) and poly(ethyleneglycol) was studied. The esterification of sodium alginate (ALG‐e) generated a material with some amphiphilic characteristics and increased compatibility with the PHB. PEG was added as plasticizer in PHB/ALG‐e films was also tested, since PEG is often used in blends with PHB to improve flexibility and reduce hydrophobicity. At the amounts studied, it was found that both PEG and ALG‐e increase the degree of crystallinity, but a decrease was observed in the hydrophobic nature of PHB films. At the maximum concentration of ALG‐e and PEG used an increase in water vapor permeability and a decrease in tensile strength was reached due to the synergistic effect caused by better homogenization of PEG and ALG‐e in the PHB matrix. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44362.