Compatible Blends of Zein and Polyvinylpyrrolidone

Blends of zein and polyvinylpyrrolidone (PVP) were compared based on their tensile properties, thermal properties and morphology. Zein was blended with polyvinylpyrrolidone of varying molecular weights (10, 55, and 1,300 kDa) and films were cast from ethanol solutions. Films cast using the higher molecular weight polymers showed an improvement in tensile strength, up to a 24% increase, compared to control. Differential scanning calorimetry data for the blends showed single T_m and T_g values of an intermediate value between those of zein and PVP control samples. Field emission scanning electron microscopy images show no obvious inhomogeneities, and confocal fluorescence microscopy showed no decreased uniformity in the PVP/zein films compared to control. Electrospun fibers of the zein/PVP blends were also obtained. These findings suggest that zein and polyvinylpyrrolidone combine to form a compatible blend, the first such blend of zein with a synthetic polymer.     

Non-isothermal Crystallization Behaviors of Polyvinyl alcohol/Hydroxyethyl Cellulose Blend Films

In this work, polyvinyl alcohol/hydroxyethyl cellulose (PVA/HEC) blend films were fabricated by solution casting and the crystalline morphology as well as non-isothermal crystallization kinetics of the blends was investigated detailedly with polarized optical microscopy, X-ray diffraction and differential scanning calorimetry. With fixed cooling rate, the crystallization time for PVA/HEC was less than that for neat PVA. The crystallization peak temperature of PVA/HEC decreased first and then increased with the increase of HEC. With higher cooling rate, the crystallinity and crystallization time decreased. It worth noting that large spherocrystal with a size of 35 μm was observed by polarized optical microscopy for PVA/HEC blends for the first time.     

Biodegradable Blends with Potential Use in Packaging: A Comparison of PLA/Chitosan and PLA/Cellulose Acetate Films

Poly(lactic acid) (PLA) is a biodegradable polymer that exhibits high elastic modulus, high mechanical strength, and feasible processability. However, high cost and fragility hinder the application of PLA in food packaging. Therefore, this study aimed to develop flexible PLA/acetate and PLA/chitosan films with improved thermal and mechanical properties without the addition of a plasticizer and additive to yield extruder compositions with melt temperatures above those of acetate and chitosan. PLA blends with 10, 20, and 30 wt% of chitosan or cellulose acetate were processed in a twin-screw extruder, and grain pellets were then pressed to form films. PLA/acetate films showed an increase of 30 °C in initial degradation temperature and an increase of 3.9 % in elongation at break. On the other hand, PLA/chitosan films showed improvements in mechanical properties as an increase of 4.7 % in elongation at break. PLA/chitosan film which presented the greatest increase in elongation at break proved to be the best candidate for application in packaging.     

The Investigation of the Toughening Mechanism of PHBV/PBAT with a Novel Hyperbranched Ethylenediamine Triazine Polymer Based Modifier: The Formation of the Transition Layer and the Microcrosslinking Structure

A new type of designed hyperbranched ethylenediamine trazine polymer (HBETP) is successfully synthesized and characterized based upon NMR and GPC. The prepared HBETP is used to modify the poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV)/poly(butylene adipate-co-terephthalate) (PBAT) blends. The effect of HBETP on the microstructure, mechanical properties and thermal properties of the blends is studied. The results indicate that upon addition of 1.0 wt% of HBETP, the impact strength of the PHBV/PBAT blends is increased by 47.1%; ?T_g of the blends decreases from 53.2 to 49.9 °C. These results, together with the morphology analysis of the fractured surface of the blends, conclude the formation of the transition layer between PHBV and PBAT. Also, the XRD result shows that the addition of HBETP can limit the growth of the PHBV crystals and causes the decrease of both the crystallinity and the grain crystalline size. The DSC result demonstrates that the addition of HBETP mainly affects the crystallization of the HB-HV binary eutectic region within PHBV. The mechanism of PHBV/PBAT toughening is due to the formation of the strong physical hydrogen bonding and the chemical micro-crosslinking between HBETP and PHBV/PBAT, which is proposed based on XPS characterization.     

Biodegradable Films Based on Blends of Gelatin and Poly (Vinyl Alcohol): Effect of PVA Type or Concentration on Some Physical Properties of Films

The aim of this work was to develop biodegradable films based on blends of gelatin and poly (vinyl alcohol) (PVA), without a plasticizer. Firstly, the effect of five types of PVA with different degree of hydrolysis (DH) on the physical properties of films elaborated with blends containing 23.1% PVA was studied. One PVA type was then chosen for the study of the effect of the PVA concentration on the mechanical properties, color, opacity, gloss, and water solubility of the films. The five types of PVA studied allowed for films with different characteristics, but with no direct relationship with the DH of the PVA. Therefore, the PVA Celvol^®418 with a DH = 91.8% was chosen for the second part, because they produced films with greater tensile strength. The PVA concentration affected all studied properties of films. These results could be explained by the results of the DSC and FTIR analyses, which showed that some interactions between the gelatin and the PVA occurred depending on the PVA concentration, affecting the crystallinity of the films.     

Characterization of Environmentally Friendly Polymers by Inverse Gas Chromatography: I Amylopectin

Amylopectin, as a potato starch based polymer, with a molecular weight of six million gram/mol was characterized using the Inverse Gas Chromatography Method (IGC). DSC method was also used to measure the glass and melting temperatures. Both DSC and IGC agreed well on a T_g of 105°C and T_m of 160–166°C. Nineteen solutes (solvents) were injected onto a chromatographic column containing amylopectin. These solutes revealed the interaction of alkanes with AP, and the wettability and water intake of AP. Alkanes showed exothermic values of interaction parameters which were increased as the temperature increased and as the number of carbons in the alkane series decreased. Retention diagrams of these solutes in a temperature range of 80–200°C revealed two zones, crystalline and amorphous. T_g and T_m were measured using these zones which complimented the DSC values. The two zones were used to calculate the degree of crystallinity below the melting temperature which ranged from 85% at 104°C to 0% at 161°C. The dispersive component of the surface energy of amylopectin was measured using alkanes which ranged from 25.35 mJ/m² at 80°C to 8.47 mJ/m² at 200°C. This is attributed to the weak crystalline surface of AP at 80°C and when the surface melted at 160°C the surface energy decreased due to the thermal expansion of the surface.     

Mechanical and Barrier Properties of Biodegradable Films Made from Chitosan and Poly (Lactic Acid) Blends

Biodegradable film blends of chitosan with poly(lactic acid) (PLA) were prepared by solution mixing and film casting. The main goal of these blends is to improve the water vapor barrier of chitosan by blending it with a hydrophobic biodegradable polymer from renewable resources. Mechanical properties of obtained films were assessed by tensile test. Thermal properties, water barrier properties, and water sensitivity were studied by differential scanning calorimeter analysis, water vapor permeability measurements, and surface-angle contact tests, respectively. The incorporation of PLA to chitosan improved the water barrier properties and decreased the water sensitivity of chitosan film. However, the tensile strength and elastic modulus of chitosan decreased with the addition of PLA. Mechanical and thermal properties revealed that chitosan and PLA blends are incompatible, consistent with the results of Fourier transform infrared (FTIR) analysis that showed the absence of specific interaction between chitosan and PLA.     

Effects of Modified Starch and Different Molecular Weight Polyvinyl Alcohols on Biodegradable Characteristics of Polyvinyl Alcohol/Starch Blends

The common biodegradable properties of polymer make them an excellent pair for blending, and the water solubility of polyvinyl alcohol (PVA) makes it easy to mix evenly with the starch. In this study, PVAs with different molecular weights were blended with various compositions of cross-linked starch (CLS) to explore the effects of molecular weight of PVA on the biodegradable characteristics of the PVA/starch blends. Comparing the biodegradability of all the various PVA/starch blends, a PVA was singled out from the PVA/starch blends of higher biodegradability. Further, the chosen PVA was then blended with the acid-modified starch (AMS) to systematically investigate the effects of the modified processing of starch on the biodegradable characteristics of the PVA/starch blends. Differential scanning calorimetry (DSC) analysis of PVA and PVA/starch specimens reveal that the T_m values of PVA/starch specimens reduce gradually as their CLS or AMS contents increase. After the CLS is blended in PVAs of different molecular weights, the tensile strength (??_f) and elongation at break (??_f) values of (P₁₀₀S₀)G₂₀M₁ specimen increase and simultaneously reduce, respectively, as their molecular weights of PVA increase from about 80,000 (PVA_BF-17) to 120,000 (PVA_BF-26). The ??_f and ??_f values of the PVA/modified-starch blends decrease with an increase in the modified starch contents. The ??_f values of the PVA/AMS specimens decrease with an increase in the concentrations of hydrochloric acid. Comparing the ??_f values of the PVA/CLS specimens with those of the PVA/AMS specimens, the ??_f values of the PVA/CLS specimens are better than those of the PVA/AMS specimens. On the contrary, the ??_f values of the PVA/AMS specimens are better than those of the PVA/CLS specimens. According to the biodegradability of all the PVA/starch blends, PVA with higher molecular weights displays higher biodegradability. The biodegradability of the PVA/modified-starch blends increase as the modified starch contents of the PVA/modified-starch blends increase. As evidenced by the results of the biodegradability test, the biodegradability of the PVA/modified-starch blends, therein PVA is blended with 1N AMS, shows better biodegradability. The result of bio-reaction kinetics experiment can evaluate the decomposition tendency of the PVA/starch blends up to any biodegradable rate under ambient environment. Using the kinetic model of the first order reaction, it is estimated that 16.20?years and 12.47?years will be needed for the PVA_BF-17/starch blends, containing 20 and 40% of CLS respectively, to be degraded up to 70% under ambient environment. In addition, it is 1.68?years for the PVA_BF-26 blends with the 40% 2N AMS under decomposition environment while it is 1.94?years for the 40% 1N AMS. Overall, the decomposition potential of PVA/AMS specimens is better than PVA/CLS specimens. Furthermore, the 1N(26P₆₀AS₄₀)₁₀₀G₂₀M₁ specimen is coincidence the biodegradable material criteria of Environmental Protection Administration (EPA) of Taiwan.     

Effect of Ionizing Radiation on the Morphological,Thermal and Mechanical Properties of Polyvinyl Alcohol/Polyethylene Glycol Blends

Blends of water—soluble polymers based on Poly vinyl alcohol (PVA) and Polyethylene glycol (PEG) have been prepared by the solution casting technique. The effect of various doses of γ-radiation on the structural properties of PVA/PEG polymer blends with all its compositions has been investigated. From the visual observation of all the blend compositions, it was found that, the best compatibility of the blend is up to 40% PVA/60%PEG. The structure–Property behavior of all the prepared blends before and after γ-irradiation was investigated by IR Spectroscopy, thermogravimetric analysis (TGA), mechanical properties and Scanning electron microscope (SEM). The gel content and the swelling behavior of the PVA/PEG blends were investigated. It was found that the gel content increases with increasing irradiation dose and PVA concentration in the blend. Swelling percent increased as the composition of PEG increased in the blend. The results obtained by FTIR analysis and SEM confirm the existence of possible interaction between PVA and PEG homopolymers. TGA of PVA/PEG blend, before and after γ-irradiation, showed that the unirradiated and irradiated PVA/PEG blends are more stable against thermal decomposition than pure PVA. Improvement in tensile mechanical properties of PVA/PEG blends was occurred.     

Thermal Stability and Degradation of Chitosan Modified by Acetophenone

N-(Methylphenylmethylidenyl) chitosan (MPMC) polymer was synthesized by chemical modification of chitosan. The chemical structure of the modified polymer was characterized by IR, ¹H NMR and elemental analysis. Thermogravimetric reveals that the thermal stability of chitosan polymer is greater than MPMC polymer. The activation energies of thermal degradation of chitosan and MPMC polymers determined using Arrhenius relationship. Thermal degradation of MPMC polymer was studied and the products of degradation were identified by GC–MS technique. It seems that the mechanism of degradation of MPMC polymer is characterized by elimination of low-molecular weight radicals. Combination or recombination of H^· or OH⁻ with these radicals and random scission mechanism along the backbone chain are the main source of the degradation products.     

Biodegradation by Composting of Surface Modified Starch and PVA Blended Films

Several starch/PVA/glycerol polymer blends were prepared by a solution casting technique and examined for biodegradation by composting over 45 days. Within this time frame, the starch and glycerol components were fully degraded, leaving the PVA component essentially intact. The lowest PVA content film (20%) was selected as a polymer with enough PVA to impart important physical characteristics, but also enough starch to be considered biodegradable. The film characteristics were further improved by surface modification with chitosan. This modification did not interfere with the biodegradation of the starch component. Furthermore, there was slight evidence that PVA biodegradation had been initiated in composted, surface modified starch/PVA blends.     

Investigation on the Influence of EVA Content on the Mechanical and Thermal Characteristics of Poly(lactic acid) Blends

Poly(lactic acid) (PLA) has gained considerable attention nowadays as a biocompatible polymer owing to its advantage of being prepared from renewable resources. PLA exhibits excellent tensile strength, fabricability, thermal plasticity and biocompatibility properties comparable to many petroleum based plastics. However, low heat distortion temperature, brittleness and slow crystallization rate limit the practical applications of PLA. In order to address these limitations, an attempt has been made in the current work to prepare binary blends of PLA with ethylene vinyl acetate (EVA) at different compositions via melt mixing technique. Systematic investigation on the mechanical properties, thermal degradation and crystallization behavior for PLA-EVA blends was carried out. The impact strength of binary blends of PLA–EVA was found to increase significantly by 176% for 15 wt% of EVA compared to virgin PLA. This is due to the strong interfacial adhesion among PLA and EVA resulting in brittle to ductile transition. Scanning electron microscopy analysis for impact fractured surfaces of binary blends of PLA implied the toughening effect of PLA by EVA. Thermogravimetry analysis results revealed that the activation energy of PLA–EVA blends decreased with increase in EVA content in the PLA matrix. While, differential scanning calorimetry results obtained for PLA–EVA blends revealed the improvement in crystallinity when compared with neat PLA. The effect of EVA on non-isothermal melt crystallization kinetics of PLA was also examined via DSC at various heating rates. Decreasing trend in the t_1/2 values indicated the faster rate of crystallization mechanism after addition of EVA in the PLA matrix.     

A Composting Study of Membrane-Like Polyvinyl Alcohol Based Resins and Nanocomposites

This study presents the effect of biodegradation, in a composting medium, on properties of membrane-like crosslinked and noncrosslinked polyvinyl alcohol (PVA) and nanocomposites. The composting was carried out for 120 days and the biodegradation of these materials was characterized using various techniques. The changes in the PVA resin and nanocomposite surface topography and microstructure during composting were also characterized. The results from the analyses suggest biodegradation of PVA based materials in compost medium was mainly by enzymes secreted by fungi. The results also indicate that the enzymes degraded the amorphous regions of the specimens first and that the PVA crystallinity played an important role in its biodegradation. The surface roughness of the specimens was seen to increase with composting time as the microbial colonies grew which in turn facilitated further microorganism growth. All specimens broke into small pieces between 90 and 120 days of composting as a result of deep biodegradation. Glyoxal and malonic acid crosslinking decreased the PVA biodegradation rate slightly. Addition of highly crystalline microfibrillated cellulose and naturally occurring halloysite nanotubes in PVA based nanocomposites also decreased the biodegradation rate. The three factors: PVA crystallinity, crosslinking and additives, may be utilized effectively to extend the life of these materials in real life applications.     

The Properties of PLA/Oxidized Soybean Oil Polymer Blends

Novel polymer blends based on completely renewable polymers were reported. Polymer blends based on polylactic acid (PLA) and oxidized and hydroxylated soya bean oil polymers were prepared. Plasticization and mechanical strength effect of the soya bean oil polymers on the PLA were observed. Fracture surface analysis of the polymer blends was carried out by using scanning electron microscopy. The PLA blends showed more amorphous morphologies compared to pure PLA. The blends had better elongation at break in view of the stress–strain measurement. Blend of PLA with the hydroxylated polymeric soya bean oil indicated the slightly antibacterial properties.     

Biodegradation of Poly(ε-caprolactone) (PCL) Film by <Emphasis Type="Italic">Alcaligenes faecalis</Emphasis>

The biodegradation behavior of PCL film with high molecular weight (80,000 Da) in presence of bacterium Alcaligenes faecalis and the analysis of degraded polymer film have been carried out. Thin Films of PCL were prepared by means of solution casting method and the bacterial degradation behavior was carried in basal medium, in presence of bacteria with time variation after UV treatment. It was observed that after UV treatment the degradation of polymer film was increased and the degradation rate followed a three steps degradation mechanism. The degraded polymer film was analyzed by means of Differential Scanning Calorimeter (DSC), Thermo Gravimetric Analyzer (TGA) and Fourier Transform Infrared Spectroscope (FTIR). DSC results revealed that at the initial stages of the degradation up to 15–20 days, the bacterium preferentially degrades the amorphous parts of the polymer film over the crystalline zone. Thermo gravimetric analysis highlighted the low temperature stability of degraded films with extent of degradation. FTIR results showed the chain scission mechanism of the polymer chains and also supported the preferential degradation of amorphous phase over crystalline phase in the initial stages of the degradation.     

Effect of Crystalline and Amorphous Structures on Biodegradability of Poly(Tetramethylene Succinate)

The effect of orientation in the amorphous and crystalline regions on the biodegradability of PTMS [poly(tetramethylene succinate)] was studied using the amorphous orientation function, birefringence, and crystallinity. The crystalline and amorphous intrinsic lateral sonic moduli, E _t,c ⁰ and E _t,am ⁰ , were 2.61 × 10³ and 0.41 × 10³ MPa, respectively. Using the data on birefringence, crystalline and amorphous orientation function (f and f _am), crystallinity, and sonic modulus of the oriented PTMS fibers, the intrinsic birefringence of the crystalline ( _c ⁰ ) and amorphous ( _am ⁰ ) regions were evaluated to be 0.0561 and 0.0634, respectively. The biodegradabilities of oriented PTMS films were reduced as the elongation increased, i.e., the amorphous orientation increased. At low elongation (100 and 150%), however, biodegradabilities remained unchanged when the degradation test was performed in activated sludge, which was attributed to the amorphous orientation occurring even at 100% elongation, though the amorphous orientation direction was perpendicular to the fiber axis.     

Photodegradation of Poly(lactic acid) Stereocomplex by UV-Irradiation

Neat poly(l-lactic acid) (PLLA) and poly(d-lactic acid) (PDLA) films and PLLA/PDLA blend films were prepared by solution casting, and their photodegradation by UV-irradiation was investigated using wide-angle X-ray scattering (WAXS), gel permeation chromatography, differential scanning calorimetry, tensile testing, and polarized optical microscopy. The PLLA/PDLA blend film was more photodegradation-resistant than the neat PLLA and PDLA films when photodegradation was monitored by molecular weight, melting temperature, and WAXS crystalline peak positions. This indicates that the chains in both amorphous and crystalline regions of the PLLA/PDLA blend film were photo-cleavage-resistant compared to those of the neat PLLA and PDLA films. The changes in melting temperature and WAXS crystalline peak positions before and after photodegradation respectively indicated the increased crystalline lattice disorder and the decreased crystalline lattice sizes of the neat PLLA and PDLA films, whereas these changes were insignificant for the blend films. Photodegradation caused no significant change in tensile properties, with the exception of significant decreases in the tensile strength and elongation at break of PLLA/PDLA blend film. However, the tensile strength and elongation at break of the PLLA/PDLA blend film retained higher values compared to those of the neat PLLA and PDLA films during photodegradation. In spite of the slower photodegradation of the PLLA/PDLA blend film traced by M _n, T _m, and WAXS crystalline peak positions than that of neat PLLA and PDLA films, the rapid decrease in tensile strength and elongation at break of the former than that of the latter should be due to the highly-ordered structural difference between them, i.e., the three dimensional dry gel of the former and the spherulites of the latter.     

Enhanced Mineralization of PLA Meltblown Materials Due to Plasticization

Polylactic acid (PLA) is one of the important biodegradable polymers. It is widely used in many industrial applications such as films and fibers. Its biodegradability is based on data derived mostly from composting processes. For a broad application of the PLA material in personal care products, an understanding of anaerobic biodegradability is essential because soiled personal care products are usually disposed of in sanitary landfills, where biodegradability mechanisms are predominately in anaerobic conditions. Extensive laboratory results are acquired to elucidate the effects of the temperature on the PLA anaerobic sludge biodegradation. When the temperature is higher than PLA glass transition temperature (T_g), anaerobic degradation is accelerated. A plausible mechanism to explain this observation is that amorphous part of the polymer is easily accessible by microorganisms. When the degrading temperature is below PLA glass transition temperature, sample mineralization under anaerobic conditions is apparently slowed. The mechanisms elucidated by T_g modification can be utilized to control the rate of PLA biodegradation for sustainable waste management.     

Characterization of Biodegradable Composite Films Prepared from Blends of Poly(Vinyl Alcohol), Cornstarch,and Lignocellulosic Fiber

Several composite blends of poly(vinyl alcohol) (PVA) and lignocellulosic fibers were prepared and characterized. Cohesive and flexible cast films were obtained by blending lignocellulosic fibers derived from orange waste and PVA with or without cornstarch. Films were evaluated for their thermal stability, water permeability and biodegradation properties. Thermogravimetric analysis (TGA) indicated the suitability of formulations for melt processing, and for application as mulch films in fields at much higher temperatures. Composite films were permeable to water, but at the same time able to maintain consistency and composition upon drying. Chemical crosslinking of starch, fiber and PVA, all hydroxyl functionalized polymers, by hexamethoxymethylmelamine (HMMM) improved water resistance in films. Films generally biodegraded within 30 days in soil, achieving between 50–80% mineralization. Both starch and lignocellulosic fiber degraded much more rapidly than PVA. Interestingly, addition of fiber to formulations enhanced the PVA degradation.     

Influence of Polyol Plasticizers on the Properties of Polyvinyl Alcohol Films Fabricated by Melt Processing

In this work, high-alcoholysis polyvinyl alcohol (PVA) films were fabricated by melt processing and the plasticizing effect of compound polyol plasticizers on PVA were investigated with X-ray diffraction (XRD), differential scanning calorimetry (DSC), rheological measurements, mechanical tests etc. Hydrogen bonding interactions occurred between PVA and plasticizer. With the increase of plasticizer, the flowability of PVA was improved and reached the maximum value at the plasticizer of 20%. Glass transition temperature (T _g) and melting point (T _m) decreased with the increase of plasticizer content. For the heterogeneous nucleation effect of plasticizer, new polymorph of PVA formed. The viscosity was sensitive to the shear rates. The incorporation of plasticizers into PVA resulted in the increase of elongation at break and impact strength, as well as the decrease of tensile strength.