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.     

Blends of Zein and Nylon-6

Blends of zein and nylon-6 (55?k) in formic acid were used to produce solution cast films and electrospun fibers. When the amount of nylon-6 was 8?% or less blends were formed that had improved tensile strength and reduced solubility. The blends were analyzed using physical property measurements, DSC and IR spectra. Using between 2 and 8?% nylon-6 provided a 33?% increase in tensile strength. Young??s modulus increased by over 50?% in this range. In general elongation was lower for all formulations. Surprisingly the cast films having 0.5?C8?% nylon-6 had improved solvent resistance to 90?% ethanol/water. Electrospun fibers were produced from formic acid solutions of zein and nylon-6 where the amount of nylon was 0, 2 and 6. Fibers produced from 27?% spinning solids had average diameters on the order of 0.5???m. Reducing the spinning solids to 21?% provide slightly smaller fibers however, the fibers had more defects.     

Blending of Epoxidised Palm Oil with Epoxy Resin: The Effect on Morphology, Thermal and Mechanical Properties

Epoxy resin prepared by the reaction of a diglycidyl ether of bisphenol A (DGEBA) and m-xylylenediamine (m-XDA) was modified with 10% wt of epoxidized palm oil (EPO). The EPO was first pre-polymerized with m-XDA at various temperatures and reaction times. The resulting product was then mixed with the epoxy resin at 40?°C and allowed to react at 120?°C for another 3?h. The fully reacted DGEBA/m-XDA/EPO blend was characterized by using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermal gravimetric analysis, tensile test, hardness indentation and dynamic mechanical analysis. The SEM study shows that different types of morphology, ranging from phase separated to miscible blends were obtained. A miscible blend was obtained when the m-XDA and EPO were reacted for more than 2?h. The results from DSC analysis show that the incorporation of EPO at 10% wt in the epoxy blend reduced the glass transition temperature (T _g). The lowered T _g and mechanical properties of the modified epoxy resins are caused by a reduction in crosslinking density and plasticizer effect.     

Properties of Poly(Vinyl Alcohol)/Chitosan Nanocomposite Films Reinforced with Oil Palm Empty Fruit Bunch Amorphous Lignocellulose Nanofibers

The objective of this study was to investigate the properties of poly(vinyl alcohol)/chitosan nanocomposite films reinforced with different concentration of amorphous LCNFs. The properties analyzed were morphological, physical, chemical, thermal, biological, and mechanical characteristics. Oil palm empty fruit bunch LCNFs obtained from multi-mechanical stages were more dominated by amorphous region than crystalline part. Varied film thickness, swelling degree, and transparency of PVA/chitosan nanocomposite films reinforced with amorphous part were produced. Aggregated LCNFs, which reinforced PVA/chitosan polymer blends, resulted in irregular, rough, and uneven external surfaces as well as protrusions. Based on XRD analysis, there were two or three imperative peaks that indicated the presence of crystalline states. The increase in LCNFs concentration above 0.5% to PVA/chitosan polymer blends led to the decrease in crystallinity index of the films. A noticeable alteration of FTIR spectra, which included wavenumber and intensity, was obviously observed along with the inclusion of amorphous LCNFs. That indicated that a good miscibility between amorphous LCNFs and PVA/chitosan polymer blend generated chemical interaction of those polymers during physical blending. Reinforcement of PVA/chitosan polymer blends with amorphous LCNFs influenced the changes of T_g (glass transition temperature), T_m (melting point temperature), and T_max (maximum degradation temperature). Three thermal phases of PVA/chitosan/LCNFs nanocomposite films were also observed, including absorbed moisture evaporation, PVA and chitosan polymer backbone structural degradation and LCNFs pyrolysis, and by-products degradation of these polymers. The addition of LCNFs 0.5% had the highest tensile strength and the addition of LCNFs above 0.5% decreased the strength. The incorporation of OPEFB LCNFs did not show anti-microbial and anti-fungal properties of the films. The addition of amorphous LCNFs 0.5% into PVA/chitosan polymer blends resulted in regular and smooth external surfaces, enhanced tensile strength, increased crystallinity index, and enhanced thermal stability of the films.     

Thermal and mechanical properties of poly(lactic Acid) and poly(ethylene/butylene Succinate) blends

In this study, blends of poly (lactic acid) (PLA) with poly(ethylene/butylene succinate) (Bionolle) have been investigated for their thermal and mechanical properties as a function of the concentration of Bionolle. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and tensile tests were used to characterize the blends. From the results of the DMA and DSC, it was found that this blend system was not miscible within the compositions studied. DSC results showed that adding Bionolle aids in crystallization of PLA. It was observed that increasing the Bionolle concentration led to a slight increase in the strain-at-break of the blends but a decrease in the Young’s modulus and ultimate tensile strength. Biaxially oriented films showed an increase in tensile strength, modulus, and strain-at-break.     

Miscibility Studies of Polysaccharide Xanthan Gum/PVP Blend

Miscibility characteristics of Xanthan gum and Poly (vinyl pyrrolidone) (PVP) in common solvent water were studied by viscometry, ultrasonic velocity and density techniques at 30 and 50 °C. Blend films of Xanthan gum/PVP were prepared by solution casting method and characterized by scanning electron microscopic (SEM) and differential scanning calorimeter (DSC) techniques. Using the viscosity data, interaction parameters of Chee’s (μ) and Sun’s (α) were computed to determine their miscibility. The values obtained revealed that blends were miscible when PVP content is up to 70% in blend at 30 °C. Xanthan gum/poly (vinyl pyrrolidone) blends showed miscibility in all composition at 50 °C. The results were then confirmed by ultrasonic velocity, density, and DSC techniques. Compatibility in the above compositions may be due to the formation of hydrogen bonding between the carbonyl group in PVP and hydroxyl group in Xanthan gum. Further, the results revealed that change in temperature had significant effect on the miscibility of Xanthan gum/Poly (vinyl pyrrolidone) blends.     

Thermoplastic Blends from Albumin and Zein: Plastic Formation and Mechanical Properties Including Modeling

The use of proteins in blending with traditional polymers in the formation of thermoplastics can produce plastics with properties that are superior to traditional petroleum-based plastics. We investigated the physical and thermal properties of albumin and zein thermoplastic blends plasticized with glycerol and mixed with varying amounts of low-density polyethylene (LDPE). Several mechanical models were utilized to determine how tensile properties will be altered when varying amounts of protein/LDPE were added into the thermoplastic blend. When analyzed for thermal properties, we found that as the amount of LDPE in the thermoplastic blend increased, the resulting plastic possessed thermal properties that were more similar to pure LDPE plastics. In terms of mechanical properties, comparison between the experimental data and model predictions points to a synergistic effect between albumin and LDPE that leads to higher modulus, while a potential lack of compatibility between zein and LDPE leads to a plastic with lower modulus. Based on our results, the use of albumin and zein proteins when blended with LDPE in the production of thermoplastics has potential use in the areas of medical and food packaging applications.     

Biodegradable Poly(butylene succinate) and Poly(butylene adipate-co-terephthalate) Blends: Reactive Extrusion and Performance Evaluation

Two biodegradable polyesters, poly(butylene adipate-co-terephthalate) (PBAT) and poly(butylene succinate) (PBS) were melt-compounded in a twin screw extruder to fabricate a novel PBS/PBAT blend. The compatibility of the blend was attributed to the transesterification reaction that was confirmed by Fourier transform infrared spectroscopy. The Gibbs free energy equation was applied to explain the miscibility of the resulting blend. Dynamic mechanical analysis of the blends exhibits an intermediate tanδ peak compared to the individual components which suggests that the blend achieved compatibility. One of the key findings is that the tensile strength of the optimized blend is higher than each of the blended partner. Rheological properties revealed a strong shear-thinning tendency of the blend by the addition of PBAT into PBS. The phase morphology of the blends was observed through scanning electron microscopy, which revealed that phase separation occurred in the blends. The spherulite growth in the blends was highly influenced by the crystallization temperature and composition. In addition, the presence of a dispersed amorphous phase was found to be a hindrance to the spherulite growth, which was confirmed by polarizing optical microscopy. Furthermore, the increased crystallization ability of PBAT in the blend systems gives the blend a balanced thermal resistance property.     

Natural Weathering of Polypropylene and Waste Tire Dust (PP/WTD) Blends

Three series of polypropylene and waste tire dust (PP/WTD) blends using three different WTD sizes were prepared, compression-molded and cut into dumbbells. The specimens were exposed to natural weathering in the northern part of Malaysia for a period of 6 months. The results show that at the same blend composition, blends with fine WTD size exhibit higher mechanical properties than that of blends with coarse WTD after exposure to natural weathering. Regardless of WTD size, the retention of tensile strength and elongation at break, E_b increases with the increase in WTD content. From the exposed surface morphology, it is apparent that the blends with fine WTD and WTD-rich blends were able to withstand weathering better than blends with coarse WTD and PP-rich blends. The DSC thermograms suggest that the overall drop in melting temperature (T_m) of the exposed blends decreases as the WTD content increases.     

Thermal,Rheological, Mechanical and Morphological Behavior of High Density Polyethylene and Carboxymethyl Cellulose Blend

In this study water soluble sodium carboxymethyl cellulose (CMC) was blended with high density polyethylene (HDPE) by peroxide-initiated melt compounding technique. The compatibility of the blended polymers were carried out by silane crosslinking agent. A series of blends were prepared by varying the CMC contents up to a maximum of 50 phr. The physical properties of non-crosslinked and crosslinked blends were investigated in detail. FTIR analysis of crosslinked blend confirmed the presence of Si–O–Si and Si–O–C absorption peaks at 1050 and 1159 cm^?1. Thermal stability of crosslinked blends improved as compared to its non-crosslinked congener. Rheological study of crosslinked blends illustrated high complex viscosity and dynamic shear storage modulus. The tensile strength of virgin polyethylene was 8.1 MPa whereas the maximum tensile strength of 19.6 MPa was observed in crosslinked blend. Similarly lower deformation was observed in crosslinked blends under static load. Scanning electron microscopy of crosslinked formulations also showed strong adhesion between the polymers interface. The compatibility of HDPE and CMC is attributed to both free radical and condensation reactions.     

Biodegradation of Polylactide and Gelatinized Starch Blend Films Under Controlled Soil Burial Conditions

The biodegradability of polylactide (PLA) and gelatinized starches (GS) blend films in the presence of compatibilizer was investigated under controlled soil burial conditions. Various contents (0–40 wt%) of corn and tapioca starches were added as fillers; whereas, different amounts of methylenediphenyl diisocyanate (MDI) (0–2.5 wt%) and 10 wt% based on PLA content of polyethylene glycol 400 (PEG400) were used as a compatibilizer and a plasticizer, respectively. The biodegradation process was followed by measuring changes in the physical appearance, weight loss, morphological studies, and tensile properties of the blend films. The results showed that the presence of small amount of MDI significantly increased the tensile properties of the blends compared with the uncompatibilized blends. This is attributed to an improvement of the interfacial interaction between PLA and GS phases, as evidenced by the morphological results. For soil burial testing, PLA/GS films with lower levels (1.25 wt%) of MDI had less degradation; in contrast, at high level of MDI, their changes of physical appearance and weight loss tended to increase. These effects are in agreement with their water absorption results. Furthermore, biodegradation rates of the films were enhanced with increasing starch contents, while mechanical performances were decreased.     

Environmental Degradation of Blends of Atactic Poly[(R,S)-3-hydroxybutyrate] with Natural PHBV in Baltic Sea Water and Compost with Activated Sludge

Degradation of atactic poly[(R,S)-3-hydroxybutyrate] (a-PHB) binary blends with natural poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV, 12 mol% of 3HV units), has been investigated and compared with plain PHBV in the compost containing activated sludge and under marine exposure conditions in the dynamic water of the Baltic Sea. Characteristic parameters of compost and the Baltic Sea water were monitored during the incubation period (6 weeks) and their influence on the degree of biodegradation is discussed. After specified degradation times of the experiments the weight loss of the samples, surface changes, changes in molecular weight and polydispersity as well as changes of the composition and thermo-mechanical properties of the blends have been evaluated. Macroscopic observations of the samples were accompanied by investigations using optical microscopy, size-exclusion chromatography (SEC), nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC) and tensile testing. The degree of degradation of blends of a-PHB with PHBV depends on the blend composition and environmental conditions. In both environments studied the weight loss of plain PHBV was more significant than changes the molecular weight. In both environments only enzymatic degradation of the blends, which proceeds via surface erosion mechanisms, was observed during the incubation period.     

Effect of Hexadecyl Lactate as Plasticizer on the Properties of Poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactide) Films for Food Packaging Applications

In this study, poly(l-lactide) (PLA) films were fabricated by melt processing and the plasticizing effect of hexadecyl lactate (HL) (0, 5, 7.5, 10, and 12.5 wt% on PLA were investigated by scanning electron microscopy (SEM), differential scanning calorimetry, thermogravimetric analysis, tensile, transparency, and water vapor permeability tests. The SEM analysis revealed that PLA with 10 wt% HL appeared uniform with extra small bumps, confirmed the interaction between PLA and HL. The thermal analysis revealed a glass transition temperature of 57.4 °C for neat PLA film, but the addition of HL elicited a decrease in the temperature of the peak (43.8 °C). The incorporation of plasticizer into PLA resulted in the increase of elongation at break, as well as the decrease of tensile strength and tensile modulus. Even though a decrease in transparency was recorded, the PLA/HL blend films appeared transparent by visually observation. The water vapor permeability of PLA/HL blend films increased with the increase of HL. The PLA/HL blend films could effectively extend the shelf-life of fresh-cut pears as the commercial low density polyethylene films. The results indicated that the properties of PLA films can be modified with the addition of HL and PLA/HL blend films could serve as an alternative as food packaging materials to reduce environmental problems associated with synthetic packaging films.     

Environmentally Friendly Oil-Modified Polyesters as Polymeric Plasticizers for Poly(vinyl chloride)

Oil-modified polyesters were synthesized to serve as polymeric plasticizers for PVC. A total of four polymeric plasticizers with different average molecular weights were prepared. Characterizations were done using Fourier-transformed infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, and gel permeation chromatography. Some of the tests conducted on PVC films include thermal stability test using thermogravimetric analyser, determination of glass transition temperature (T_g), plasticizer migration and leaching resistance test, morphology study of plasticized PVC films using field emission scanning microscope, toxicity test, and tensile test. Owing to the plasticizing effect of the palm oil-based compound, T_g of the plasticized PVC has decreased to an average of 65 °C at 20 wt% loading. The polymeric plasticizer is also able to contribute positively to the thermal stability and mechanical properties of the PVC films. Some of the advantages of incorporating polymeric plasticizer with high molecular weight includes lower rate of leaching from plastic, and improved tensile strength and elongation at break. Besides, thermal stability of the plastic studied using Kissinger’s and Flynn–Wall–Ozawa’s approaches shows that PVC blended with high molecular weight oil-modified polyester is more thermally stable, evidenced by the increase in the activation energy of decomposition, E_d. Toxicity test using brine shrimp egg shows encouraging results, where the oil-based plasticizer is considerably less toxic compared to some of the commercial plasticizers.     

A Biobased Blend of Cellulose Diacetate with Starch

Two bio-based polymers, cellulose diacetate (CDA) and starch, were used to prepare blends with reasonable properties and low cost. Due to the poor processing properties, starch was modified in the presence of glycerol and epoxidized soybean oil (ESO), and CDA was plasticized by triacetin (TA) and ESO, respectively. The morphologies of the blends with different amounts of modified starch (MST) were studied by scanning electron microscope (SEM), and the physical properties of the blends, including thermal stability, mechanical property, water and moisture resistance, were investigated. The equilibrium moisture absorption rates of the blends containing 30 and 50 wt% MST at 100 % of relative humidity(RH) were 9.4 and 15.0 %, respectively. SEM and DMA results demonstrated that CDA and MST had a certain extent of compatibility. Due to the partial plasticization of starch, the tensile strength of the blends was nearly not affected by the amount of MST. Even if 50 wt% MST was added, the tensile strength of the blend was as high as 24.7 MPa. The obtained blend containing 30 wt% MST can keep good mechanical properties at 50 % RH, and its tensile strength and elongation at break are 30.2 MPa and 3.6 %, respectively. All the results show that the CDA/MST blends have a potential as an environmental friendly material.     

Biodegradation of LDPE/Modified Starch Blends Sterilized with Gamma Radiation

Blends of LDPE/modified starch were prepared, sterilized by gamma radiation and investigated with respect to their microbial degradation by a mixture of fungal strains in liquid medium after 90 days, was analyzed by carbon dioxide (CO₂) production (Sturm test). Biodegradation of blends was evaluated by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction; mechanical testing, scanning electron microscopy (SEM). The biodegradation of LDPE/modified starch blends was attributed to microbiological attack, with alterations in the chemical structure of the blend with an increase in the carbonyl and vinyl indices and the appearance of new crystalline symmetry generating a crystalline domain not existing before in the blend and decrease in the mechanical properties.     

Novel Biodegradable Cast Film from Carbon Dioxide Based Copolymer and Poly(Lactic Acid)

Poly(lactic acid) (PLA) and poly(propylene carbonate) (PPC) blends with different levels of chain extender were prepared and cast into films. The effect of chain extender on the mechanical, thermal and barrier properties of the films were investigated. With the inclusion of the chain extender, the compatibility and interfacial adhesion between the two polymer phases were significantly improved by a mean of forming a PLA–chain extender–PPC copolymer. Reactions between the chain extender, PLA and PPC were observed through FTIR study. SEM study also confirmed the improved compatibility and interfacial adhesion. The elongation at break of the compatibilized film with optimal amount of chain extender showed dramatic increase by up to 1940 %. DSC studies revealed that chain extender hindered the crystallization of the film which explained the decrease in both water and oxygen barrier when adding chain extender. PLA was found to be able to enhance both oxygen and water barrier of the blend as compared to neat PPC, while in the case of the blend with chain extender, oxygen and water barrier properties exhibited reduction at the beginning. However, when increasing chain extender concentration, these two barrier performance exhibited an upward trend. It was found that PLA/PPC blend showed much better oxygen barrier property than both parent polymers, which can be ascribed to the acceleration effect of PPC on the crystallization of PLA.     

A Study of Physicomechanical and Morphological Properties of Starch/Poly(vinylalcohol) Based Films

Starch/Poly(vinylalcohol) blends in two different ratios (60:40 and 50:50) were prepared with glycerol as a plasticizer. Films were cast by a solution casting method. One set of films were filled with 10 wt% of unmodified bentonite clay and another set of films were crosslinked with epichlorohydrin in an alkaline medium. The prepared film samples were subjected to X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), mechanical characterization and scanning electron microscope (SEM). Significant changes in the tensile properties were observed depending on the different chemical constituents of the films. The presence of clay and crosslinking with epichlorohydrin were both found to have considerable effect on the morphology and mechanical property of the films. The SEM investigations, XRD analysis and FTIR studies revealed the interaction between the various chemical components of the films.     

Physical properties and biodegradability of blends containing poly(ε-caprolactone) and tropical starches

In order to assess feasibility of tropical starches (sago and cassava starches) as biodegradable plastic materials, blending with poly(-caprolactone) (PCL), a biodegradable polymer, was carried out. It was confirmed that the physical properties (tensile strength and elongation) of PCL/sago and PCL/cassava blends were similar to those of PCL/corn blend, suggesting that sago and cassava starches can also be blended with PCL for production of biodegradable plastic. However, the properties of all PCL/starch blends were still low compared with those of polyethylene. Enzymatic degradability evaluation showed that lipase degradation of PCL and-amylase degradation of starch increased as the starch content in the blend increased. Burial test of the blends for 1, 3, and 5 months was carried out and the rate of degradation of the PCL/sago blend was confirmed to be slower than those of PCL/corn and PCL/cassava blends. Observation of the film blends structure by scanning electron microscope revealed that the starch was dispersed in a PCL continuous phase. Furthermore, changes in the film surface before and after enyzme treatments were observed.     

Novel Tough Crystalline Blends of Polylactide with Ethylene Glycol Derivative of POSS

Blending of polylactide (PLA) with low stereoregularity and polyhedral oligomeric silsesquioxane grafted with arms of poly(ethylene glycol) methyl ether, acting as a plasticizer, allowed us previously to obtain a novel stable elastomeric-like material. The present contribution focuses on the properties of semi-crystalline PLA plasticized with this compound. Melt blends of PLA with 5–15 wt% of the plasticizer, were compression molded, quenched and annealed, which enabled cold-crystallization. The glass transition temperature of the blends and their drawability depended on their crystallinity and plasticizer content. The best ductility was reached at the plasticizer content of 15 wt%; the achieved strain at break was 6.5 (650%) and 1.3 (130%), for the quenched and annealed material, respectively. The latter value exceeded 20 times the strain at break of neat crystalline PLA. The tensile toughness of the annealed 15 wt% blend was 12 times larger than that of crystalline PLA. Moreover, annealing of 15 wt% blend improved its yield strength by 40%. Despite the two peaks of the loss modulus, indicating the two glass transitions in this blend, no heterogeneities were found by scanning electron microscopy, indicating that the plasticizer enriched phase formed instead of distinct inclusions of the plasticizer.