Increasing Plasticizer Content Research Articles

Water vapour barrier performance of corn-zein coated polypropylene (PP) packaging films

The novel film structure of corn-zein coated on polypropylene (PP) synthetic film for packaging industry was developed to examine the feasibility of resulting coated films as an alternative water barrier performance for food packaging. The effects of coating formulation (solvent, corn-zein, plasticizer concentration and plasticizer type) on final properties of films were observed. Corn-zein is the most important protein of corn and has good film forming property. Composites structures of PP films coated with corn-zein were obtained through a simple solvent casting method. Polyethylene glycol (PEG) and glycerol (GLY) were used as plasticizer to increase film flexibility. Statistical analysis based on full factorial design was performed to observe coating formulation effects. The high water vapour barriers were obtained for films coated with coating formulation consisting of higher amounts of corn-zein plasticized by GLY. The lower glass transition temperatures (Tg) of films were obtained by plasticization of films and Tg decreased by increasing plasticizer content. The statistical analysis defined the key parameters of coating formulation that had major effects on the final properties of coated PP films as corn-zein, plasticizer concentration and plasticizer type. In conclusion, corn-zein coatings could have potential as an alternative to conventional synthetic polymers used in composite multilayer structures for food packaging applications.

Physical and Mechanical Properties of Durum Wheat (Triticum durum) Starch Films Prepared with A‐ and B‐type Granules

AbstractThe use of starch for the production of biodegradable materials has been increasing. Wheat is an important source, however, durum wheat starch and its separated granular components had not been evaluated for this purpose. The aim of this study was to evaluate the physical and mechanical properties of durum wheat starch films when prepared with a distribution of different granular‐sized starches (A‐ and B‐type). Starch was isolated, and the A and B populations of granules were separated. Films were prepared by casting. Glycerol (G) was used as a plasticizer in concentrations of 25% and 40%, respectively. Starch films were evaluated using scanning electron microscopy (SEM), mechanical properties (tensile strength, TS, elongation at break, E, elastic modulus, EM), solubility, and X‐ray diffraction (XRD). Durum wheat starch films were transparent, flexible, and, according to SEM, highly homogeneous. Films prepared with 25% G showed brittle material behavior (TS = 42–50 MPa, E = 1.4–2.7%, and EM = 31–34 MPa), whereas those prepared with 40% G had ductile material characteristics (TS = 11–17 MPa, E = 4–41%, and EM = 4–11.3 MPa). These mechanical properties of the films were significantly affected by the glycerol concentration and the starch granule type used. The film solubility was low when compared to those reported in other studies. It increased with increasing plasticizer concentration. According to the XRD, the films showed a semi‐crystalline structure.

Evaluation of the effects of glycerol and sorbitol concentration and water activity on the water barrier properties of cassava starch films through a solubility approach

The effects of glycerol and sorbitol on the water sorption isotherms and water vapor permeability ( K w ) of cassava starch films prepared by casting were investigated. K w values were determined in three ranges of relative humidity, RH, (2–33%, 33–64% and 64–90%) and the GAB model was used to fit experimental water sorption isotherms. These data were used to determine the relative influence of the diffusion coefficient of water ( D w ) and the average solubility coefficient ( β ¯ ) of water in the films on the K w value. In all cases, an increase in K w values were observed with increasing plasticizer concentration and RH. The D w , β ¯ and K w values of films prepared with glycerol were greater than those of films prepared with sorbitol. For high RH, the β ¯ values increased 6-fold for films with glycerol and 7-fold for films with sorbitol, while D w values did not change significantly. These results indicate that K w values are dependent on the solubility coefficient ( β ¯ ) of water in the film, which is not consistent with the proposal that an opening of polymer chains promoted by plasticizers leads to an increase in D w and K w .

Physicochemical characterization of starch based films

In the present study, high amylose corn starch (HACS) based films were obtained with a low temperature method consisted on reduce gelatinization temperature by an alkaline pretreatment of starch. Effects of film composition and preparation method on film properties were investigated to identify HACS film elaboration conditions to improve film properties. Rheological behavior of film-forming solutions is reported. Films were physical and chemically characterized through film solubility in water, water sorption isotherms, opacity and crystallinity of films. Film forming suspensions show pseudoplastic and thixotropic behavior. Apparent viscosity of film forming gel increases exponentially with HACS concentration and Arrhenius law adequately represents variation with temperature. Alkaline treatment time of HACS previous to gelatinization, also affects film properties. It was found that film solubility and opacity decrease while crystallinity increases although it reaches an asymptotic value after treatment time of 60 min. Above 30% of glycerol, an increase in plasticizer content conduces to a looser network, as a result film opacity and water sorption increase.

Crystallinity, thermal properties, morphology and conductivity of quaternary plasticized PEO‐based polymer electrolytes

AbstractQuaternary plasticized solid polymer electrolyte (SPE) films composed of poly(ethylene oxide), LiClO4, Li1.3Al0.3Ti1.7(PO4)3, and either ethylene carbonate or propylene carbonate as plasticizer (over a range of 10–40 wt%) were prepared by a solution‐cast technique. X‐ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) indicated that components such as LiClO4 and Li1.3Al0.3Ti1.7(PO4)3 and the plasticizers exerted important effects on the plasticized quaternary SPE systems. XRD analysis revealed the influence from each component on the crystalline phase. DSC results demonstrated the greater flexibility of the polymer chains, which favored ionic conduction. SEM examination revealed the smooth and homogeneous surface morphology of the plasticized polymer electrolyte films. EIS suggested that the temperature dependence of the films' ionic conductivity obeyed the Vogel–Tamman–Fulcher (VTF) relation, and that the segmental movement of the polymer chains was closely related to ionic conduction with increasing temperature. The pre‐exponential factor and pseudo activation energy both increased with increasing plasticizer content and were maximized at 40 wt% plasticizer content. The charge transport in all polymer electrolyte films was predominantly reliant on lithium ions. All transference numbers were less than 0.5. Copyright © 2006 Society of Chemical Industry

Effect of various polyols and polyol contents on physical and mechanical properties of potato starch-based films

The present study investigated effects of plasticizer (glycerol, xylitol and sorbitol) and relative humidity on physical and mechanical properties of potato starch-based edible films. Films were obtained from solutions containing gelatinized starch, polyol and water by casting and evaporating water at 35°C. Water content of films increased with increasing relative humidity and plasticizer content. Water vapor permeability of films increased with increasing plasticizer content and storage relative humidity. Young’s modulus decreased with increasing polyol content with a concurrent increase in elasticity of films. Both increased polyol and water content increased elongation at break with a decreased tensile strength. Glass transition temperatures decreased as a result of plasticization as polyol and/or water content increased. Effects of plasticizers on physical and mechanical properties of films were largest for glycerol and smallest for sorbitol. High contents of xylitol and sorbitol resulted in changes in physical and mechanical properties of films probably due to phase separation and crystallization.

Plasticization of semicrystalline poly( l-lactide) with poly(propylene glycol)

Plasticization of semicrystalline poly( l-lactide) (PLA) with a new plasticizer – poly(propylene glycol) (PPG) is described. PLA was plasticized with PPG with nominal M w of 425 g/mol (PPG4) and 1000 g/mol (PPG1) and crystallized. The plasticization decreased T g, which was reflected in a lower yield stress and improved elongation at break. The crystallization in the blends was accompanied by a phase separation facilitated by an increase of plasticizer concentration in the amorphous phase and by annealing of blends at crystallization temperature. The ultimate properties of the blends with high plasticizer contents correlated with the acceleration of spherulite growth rate that reflected accumulation of plasticizer in front of growing spherulites causing weakness of interspherulitic boundaries. In PLA/PPG1 blends the phase separation was the most intense leading to the formation of PPG1 droplets, which facilitated plastic deformation of the blends that enabled to achieve the elongation at break of about 90–100% for 10 and 12.5 wt% PPG1 content in spite of relatively high T g of PLA rich phase of the respective blends, 46.1–47.6 °C. Poly(ethylene glycol) (PEG), long known as a plasticizer for PLA, with nominal M w of 600 g/mol, was also used to plasticize PLA for comparison.

Physical Properties of Gelatin Films Plasticized by Blends of Glycerol and Sorbitol

The addition of plasticizers increases the flexibility and workability of films based on biopolymers. However, the use of some plasticizers cause undesirable results, such as the migration of these additives out the film or crystallization during shelf life. Thus, the aim of this study was to evaluate the effect of blends with different ratios of sorbitol and glycerol, at 2 plasticizer concentrations, on mechanical, viscoelastic, and water vapor barrier properties of films based on gelatin. The films were prepared with 2 g gelatin/100 mL of water and with 25 or 55 g plasticizer/100 g gelatin. The ratio, glycerol to sorbitol, was studied as 0:100, 20:80, 40:60, 60:40, 80:20, and 100:0. The increase of plasticizer concentration from 25 to 55 g plasticizer/100 g gelatin caused an increase of flexibility and reduction of resistance and water vapor barrier as expected. In relation to the effect of the mixture, the increase in the proportion of glycerol caused a reduction of the puncture force, tensile strength, modulus of elasticity, and an increase of the puncture deformation, elongation at break, and water vapor permeability due to the higher plasticizing effect of glycerol. This behavior was explained in terms of molecular weight of the plasticizers, which demonstrated that the studied properties could be considered as functions of the number of molecules of plasticizers in the films.

Conductivity studies of plasticized PEO-Lithium chlorate–FIC filler composite polymer electrolytes

A new report of the synthesis of (PEO/plasticizer)LiClO4–Li1.3Al0.3Ti1.7(PO4)3 polymer electrolyte films prepared by the solution-cast technique is represented in this work. DSC trace revealed that Tg decreased with the increase of plasticizer content in the polymer electrolyte films. SEM morphology showed that the surface morphology of films was relatively smooth and homogeneous. Conductivity studies by EIS measurement indicated that the temperature dependence of ionic conductivity of films followed Vogel–Tamman–Fulcher (VTF) equation. The pre-exponential factor (A) and the pseudo activation energy (Ea) increased with the increase of plasticizer content in the polymer electrolyte films. At the 40 wt.% plasticizer content, A and Ea respectively had a maximum.

Influence of plasticizers on the water sorption isotherms and water vapor permeability of chicken feather keratin films

Biodegradable films from many protein sources have in recent decades attracted a lot of attention for their potential use in food protection because they have several advantages over synthetic films, including those related to the environment. The effects of type and concentration of plasticizers on microstructure, sorption isotherms and water vapor permeability (WVP) of films obtained from chicken feather keratin (CFK) were investigated. Keratins were extracted with an aqueous solutions of urea, 2-mercaptoethanol and surfactant. The protein was dosed and the maximum concentration achieved was 12 g/100 ml. The protein concentration in the keratin film solution was standardized at 7 g/100 ml for the preparation of the films by casting. The results showed that increasing the plasticizer concentration caused a decrease in barrier properties and favored water adsorption by the polymeric network, increasing the moisture content of the films. The monolayer moisture content was 8.76 times higher for films made with glycerol than films made without plasticizer and 12 times higher than films plasticized with PEG 4000. The same behavior was observed for the water solubility coefficient, which increased with increasing plasticizer concentration.

“Green” Nanocomposites from Cellulose Acetate Bioplastic and Clay: Effect of Eco-Friendly Triethyl Citrate Plasticizer

"Green" nanocomposites have been successfully fabricated from cellulose acetate (CA) powder, eco-friendly triethyl citrate (TEC) plasticizer and organically modified clay. The effect of the amount of plasticizer varying from 15 to 40 wt % on the performance of the nanocomposites has been evaluated. The morphologies of these nanocomposites were evaluated through X-ray diffraction (XRD), atomic force microscopy (AFM), and transmission electron microscopy (TEM) studies. The mechanical properties of nanocomposites are correlated with the XRD and TEM observations. Cellulosic plastic-based nanocomposites with 20 wt % TEC plasticizer and 5 wt % organoclay showed better intercalation and an exfoliated structure than the counterpart having 30/40 wt % plasticizers. The tensile strength, modulus and thermal stability of cellulosic plastic reinforced with organoclay showed a decreasing trend with an increase of plasticizer content from 20 to 40 wt %. The nano-reinforcement at the lower volume fractions (phi < or = 0.02) reduced the water vapor permeability of cellulosic plastic by 2 times and the relative permeability better fits with larger platelet aspect ratios (alpha = 150).

Relationship between plasticizer content and tensile bond strength of soft denture liners to a denture base resin.

The purpose of this study was to determine the influence of plasticizer content on the tensile bond strength of heat-cured acrylic soft denture liners to a denture base resin. Differences among materials were significant, except for 100 wt% Dibutyl Sebacate (DBS) and 80 wt% DBS of tensile bond strength. The bond strength of all materials to the denture base increased with an increase in thermal cycles significantly except for 40 wt% DBS. The tensile bond strength of soft denture liners to the denture base resin significantly decreased with an increase of plasticizer contents. Differences were found among the difference plasticizer contents in failure types between the denture base resin and soft denture liners. The results suggest that the tensile bond strengths of heat-cured acrylic soft denture liners to the denture base resin were lower with an increase in plasticizer content.

Whey protein isolate coating on LDPE film as a novel oxygen barrier in the composite structure

AbstractTo examine the feasibility of whey protein isolate (WPI) coating as an alternative oxygen barrier for food packaging, heat‐denatured aqueous solutions of WPI with various levels of glycerol as a plasticizer were applied on corona‐discharge‐treated low‐density polyethylene (LDPE) films. The resulting WPI‐coated LDPE films showed good appearance, flexibility and adhesion between the coating and the base film, when an appropriate amount of plasticizer was added to the coating formulations. WPI‐coated LDPE films showed significant decrease in oxygen permeability (OP) at low to intermediate relative humidity, with an Arrhenius behaviour and an activation energy of 50.26 kJ/mol. The OP of the coated films increased significantly with increasing relative humidity, showing an exponential function. Although the coated films showed a tendency to have less oxygen barrier and more glossy surfaces with increasing plasticizer content, differences in the OP and gloss values were not significant. Haze index and colour of the coated films were also little influenced by WPI coating and plasticizer content. The results suggest that whey protein isolate coating could work successfully as an oxygen barrier and have potential for replacing synthetic plastic oxygen‐barrier layers in many laminated food packaging structures. Copyright © 2004 John Wiley &amp; Sons, Ltd.

Thermal and mechanical properties of plasticized poly(L‐lactic acid)

AbstractAcetyl tri‐n‐butyl citrate (ATBC) and poly(ethyleneglycol)s (PEGs) with different molecular weights (from 400 to 10000) were used in this study to plasticize poly(L‐lactic acid) (PLA). The thermal and mechanical properties of the plasticized polymer are reported. Both ATBC and PEG are effective in lowering the glass transition (Tg) of PLA up to a given concentration, where the plasticizer reaches its solubility limit in the polymer (50 wt % in the case of ATBC; 15–30 wt %, depending on molecular weight, in the case of PEG). The range of applicability of PEGs as PLA plasticizers is given in terms of PEG molecular weight and concentration. The mechanical properties of plasticized PLA change with increasing plasticizer concentration. In all PLA/plasticizer systems investigated, when the blend Tg approaches room temperature, a stepwise change in the mechanical properties of the system is observed. The elongation at break drastically increases, whereas tensile strength and modulus decrease. This behavior occurs at a plasticizer concentration that depends on the Tg‐depressing efficiency of the plasticizer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1731–1738, 2003

Plane stress fracture toughness of physically aged plasticized PETG as assessed by the essential work of fracture (EWF) method

The plane stress fracture toughness of amorphous copolyester (PETG) sheets plasticized by various amount of neopentylglycol dibenzoate (NPGDB in 0, 5, 10 and 20wt%) was studied in as-received (AR) and rejuvenated (RJ) states by adopting the essential work of fracture (EWF) method. EWF tests were performed on deeply double-edge notched tensile loaded (DDEN-T) specimens at various deformation rates (2,10 and 100 mm/min) at room temperature. It was established that physical aging strongly affected the EWF terms. The specific yielding-related EWF increased with increasing deformation rate and decreased with increasing plasticizer content. The specific non-essential work and its necking-related constituent, which changed parallel to each other, remained constant up to 10wt% NPGDB content and decreased afterwards. The plastic zone in the DDEN-T specimens was formed by cold drawing which is governed by the entanglement structure. This was demonstrated by the shape recovery of the plastic zone in the broken DDEN-T specimens after heating them above the Tg of the related PETG compound.

Time-Dependent Mechanical Properties of Polymeric Coatings Used in Rupturable Pulsatile Release Dosage Forms

The mechanical properties of polymer films used in pharmaceutical coatings of pulsatile drug delivery systems were evaluated in the dry and the wet state by a newly developed puncture test, which allowed the time-dependent measurement of the mechanical properties on the same film specimen. Force, puncture strength, energy at break, modulus, and strain were investigated as a function of water exposure time with respect to the type of polymer and the type and concentration of plasticizer and pore former (hydroxypropyl methylcellulose, HPMC). Eudragit® RS films were very flexible, had a high strain, and broke upon puncture with only small cracks. In contrast, ethylcellulose films were more brittle with a lower strain and showed complete film rupture. Increased amounts of the hydrophilic pore former, HPMC, resulted in a reduced puncture strength and in an increase in water uptake and weight loss of the films. The puncture strength decreased with increasing plasticizer concentration and was lower with the lipophilic dibutyl sebacate than with the hydrophilic triethyl citrate.

Thermal, electrical and mechanical properties of plasticized polymer electrolytes based on PEO/P(VDF-HFP) blends

The polymer electrolytes composed of a blend of poly(ethylene oxide) (PEO) and poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) as a host polymer, mixture of ethylene carbonate (EC) and propylene carbonate (PC) as a plasticizer, and LiClO 4 as a salt were prepared by a solution casting technique. SEM micrographs show that P(VDF-HFP) is very compatible with PEO. The ionic conductivity of the electrolytes increases with increasing plasticizer content, while the mechanical properties become obviously worse. By addition of a certain content of PEO in P(VDF-HFP) matrix, a good compromise between high ionic conductivity and mechanical stability can be obtained.

Effect of plasticizer on the dynamic surface tension and the free volume of Eudragit systems.

The purpose of the present study was to determine the changes of dynamic surface tension of aqueous Eudragit dispersions quantitatively and compare these data with the free volume of the free films formed from several dispersions of different dibutyl sebacate (DBS) concentrations. Eudragit L 30D and Eudragit RL 30D aqueous colloidal polymer dispersions and their cast free films were examined. The concentration of DBS varied in the dispersions from 0 to 20%. The dynamic surface tension of the dispersions were measured by the Du Nouy ring method while the free volume of cast films were determined by positron annihilation spectroscopy. The obtained results show that dynamic surface tension measurements indicate the white point (WP) of Eudragit dispersions by a significant standard deviation increase. This may suggest the applicability of dynamic surface tension measurements for the determination of the WP of polymeric dispersions. A decrease in the WP temperature of Eudragit dispersions with an increasing plasticizer concentration was observed up to the DBS concentration of 10% w/w. Above this concentration neither the WP of the polymer dispersion nor the free volume of the free films of the polymer were changed remarkably.

PLASTICIZER EFFECT ON THE GLASS TRANSITION TEMPERATURE OF BETA–LACTOGLOBULIN FILMS

The effect of plasticizer on betalactoglobulin (.Lg) film glass transition temperature (Tg) was investigated toelucidate the plasticization mechanism. The Tg of film containing polyethylene glycol 400 (PEG 400) as a plasticizer couldnot be observed because an icemelting peak occurred during heating. Films plasticized by propylene glycol (PG), glycerol(Gly), and PEG 200 possessed similar film Tg values, related to the plasticizer waterbinding properties. However, sorbitol(Sor) and sucrose (Suc) produced higher film Tg values due to their larger MW and solidstate plasticizer behavior. Lubricationof .Lg molecules by plasticizer domains external to the .Lg is suggested as a film plasticization mechanism because noshift in film Tg was observed with increasing plasticizer content. The size, shape, and physical state of plasticizer were thekey factors affecting film properties, consistent with previous results on mechanical and oxygen permeability (OP) properties.

Effect of plasticizer on thermodynamic properties of nylons: Model, phenomenology, and proposed experiments

Motivated by experiments showing decreasing tensile modulus of nylons with increasing plasticizer content, a model involving the disruption of nylon hydrogen bonding by addition of plasticizer is proposed. This leads to proposed further experiments and suggests a complementary phenomenological analysis that involves the bulk modulus. The surface energy as a function of plasticizer concentration is then incorporated into the phenomenology. The importance of varying the temperature in the proposed thermodynamic measurements is stressed.