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.     

Man-Made and Natural Fibres as a Reinforcement in Fully Biodegradable Polymer Composites: A Concise Study

Biodegradable and ecologically friendly polymer materials attract great attention of many scientific groups in the world as they fit well in the sustainable development policy and are considered to be “a right thing to do” by the general public. Such polymers can be modified by the addition of different fillers, favorably of natural origin. In the paper we provide a comparison between composites based on two biodegradable polymers: poly(lactic acid)—biodegradable, natural stock polymer and poly(butylene succinate)—biodegradable polymer produced from fossil based materials. For each polymer we have prepared a series of composites with different fibres (natural: hemp and flax, and manmade: Cordenka) and different filler loadings. To fully characterize obtained materials thermal, mechanical and surface free energy measurements were performed, completed with morphology observations and an attempt to compare the experimental data for tensile measurements with values obtained using the modified rule of mixtures. The tensile results calculated using the modified rule of mixture for below 30% fibre loading are found to be fitting the experimental data. Composites mechanical properties and morphology were strongly affected by the type of fibre used and its loading, however thermal properties remained almost unchanged. In specific, Cordenka fibres tend to form bunches which presence greatly influences the mechanical properties but still our studies have shown clear advantage of manmade Cordenka fibres over the hemp and flax fibres when considering distribution and fibre–polymer interaction.     

Formulation and Characterization of Sodium Alginate g-Hydroxy Ethylacrylate Bio-Degradable Polymeric Beads: In Vitro Release Studies

Novel type of highly swollen beads were prepared by grafting 2-hydroxyethylacrylate onto biodegradable Sodium alginate (SA) via free-radical polymerization using potassium persulphate as an initiator and Triprolidine hydrochloride as a model drug. Evidence of grafting was obtained by fourier transform infrared spectroscopic technique. Morphological properties of the beads were studied by SEM analysis. Thermal properties and crystallinity of the beads were characterized using differential scanning calorimetry and thermogravimetric analysis and X-ray diffraction techniques, respectively. Dissolution experiments were performed to study the release profiles at 37?°C in phosphate buffer solution (pH-7.4). Effect of monomer content, crosslinking agent and drug/polymer ratio on swelling properties and release profiles were also comparatively studied. A dissolution result concludes that drug release decreases with increasing crosslinker content. The highest release (96%) was obtained for the beads prepared with 0.5?mL crosslinking agent. Equilibrium swelling degree also supports the drug release profiles confirming SA-g-HEA beads showed better release profiles compare to plain SA beads.     

Synthesis and Properties of Biodegradable Poly(vinyl alcohol)/Organo-nanoclay Bionanocomposites

Biodegradable nanocomposites comprising of biodegradable polymers and bioactive organically modified layered silicates commonly reveal extremely enhanced mechanical and various other properties when compared to those of virgin polymers. This work was undertaken with a view to preparation of polymer bionanocomposites consisting of biodegradable poly(vinyl alcohol) (PVA) and organo-nanoclay. Cloisite Na⁺ and ammonium salt of l-isoleucine amino acid was used for the preparation of the novel chiral organo-nanoclay via an intercalation reaction in an aqueous solution. PVA/organo-nanoclay bionanocomposites of various compositions were created through the solution intercalation method by ultrasound-assisted technique. The resulting novel materials were characterized by X-ray diffraction and Fourier transform infrared spectroscopy techniques. Thermogravimetric analysis (TGA) and UV/vis spectroscopy were applied to test the properties of PVA bionanocomposites. TGA indicate that the thermal stability is enhanced distinctly, without a sacrifice in optical clarity. The improvement of thermal properties was attributed to the homogeneous and good dispersion of organo-nanoclay in polymeric matrix and the strong hydrogen bonding between O?CH groups of PVA and the oxygen atoms of silicate layers or carbonyl group as well as OH group of intercalated amino acid. The morphology of the organo-nanoclay and PVA bionanocomposites was examined by scanning electron microscopy and transmission electron microscopy techniques. Uniform distribution of clay due to intimate interaction between clay and polymer appears to be the cause for improved properties.     

Preparation and Properties of Chitosan–PVA Fibers Produced by Wet Spinning

Chitosan fibers were prepared by wet spinning in three stages. Initially, a polymer solution of chitosan and polyvinyl alcohol (PVA) was solidified in a mixture of potassium hydroxide and ethanol. The polymers were then crosslinked with sodium tripolyphosphate (TPP) or glutaraldehyde, and finally dried in methanol or acetone. The effect of these conditions was evaluated based on scanning electron microscopy images, water-holding capacity, and swelling and mechanical properties. The miscibility of the mixture was evaluated using Fourier Transform Infrared spectroscopy and differential scanning calorimetry. The results obtained showed that chitosan fibers containing 45% (v/v) PVA and crosslinked using TPP have properties similar to those of commercial sutures prepared using other biomaterials.     

Biodegradable Polyester-Based Blend Reinforced with Curauá Fiber: Thermal,Mechanical and Biodegradation Behaviour

Biodegradable composites can be produced by the combination of biodegradable polymers (BP) as matrix and vegetal fibers as reinforcement. Composites of a commercial biodegradable polymer blend and curauá fibers (loaded at 5, 15 and 20 wt%) were prepared by melt mixing in a twin-screw extruder. Chemical treatments such as alkali treatment of the fiber and addition of maleic anhydride grafted polypropylene (MA-g-PP) as coupling agent were performed to promote polymer/fiber interfacial adhesion so that mechanical performance can be improved. The resulting composites were evaluated through hardness, melt flow index and tensile, flexural and impact strengths as well as water absorption. Thermal analysis and Fourier transform infrared spectroscopy were also employed to characterize the composites. The polymer/fiber interface was investigated through scanning electron microscopy analysis. The biodegradability of composites was evaluated by compost-soil burial test. The addition of curauá fiber promoted an increase in the mechanical strengths and composites treated with 2 wt% MA-g-PP with 20 wt% curauá fiber showed an increase of nearly 75% in tensile and 56% in flexural strengths besides an improvement in impact strength with respect to neat polymer blend. Nevertheless, treated composites showed an increase in water absorption and biodegradation tests showed that the addition of fiber retards degradation time. The retained mass of BP/20 wt% fiber composite with MA-g-PP and neat BP was 68 and 26%, respectively, after 210 days of degradation test.     

Biodegradable Composite Foams of PLA and PHBV Using Subcritical CO<Subscript>2</Subscript>

One key strategy for increasing the application potential for biodegradable plastics lies in improving the physical and mechanical characteristics, which can be attained by inducing a cellular morphology in the pure polymer with the aid of a blowing agent, as well as by blending two or more polymers with the desirable properties. This paper examines the effect that blending two biodegradable polymers has on the thermal properties and morphology of the resultant foams blown with carbon dioxide (CO₂). Polylactic acid (PLA), polyhydroxybutyrate-co-valerate (PHBV) and blends of both were foamed and characterized in terms of thermal characteristics, relative density, cell size, and foam morphology. The results indicate that although PLA and PHBV are immiscible, the presence of small quantities of PHBV (25 wt%) could lead to low density foams with finer, more uniform cells. Furthermore, the crystallinity of PHBV was found to be unaffected by the presence of PLA in the composite, which supports the immiscibility of PLA and PHBV.     

A Study of Dynamic Mechanical and Thermal Behavior 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 bentonite clay and another set of films were crosslinked with epichlorohydrin in an alkaline medium. The prepared film samples were characterized with dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). The presence of clay and crosslinking with epichlorohydrin was found to have considerable effect on the dynamic mechanical properties and thermal stability of the films. Intercomponent H-bonding between starch, Poly(vinylalcohol) and glycerol enhanced the thermal stability of the films. But incorporation of clay and crosslinking with epichlorohydrin enhanced the steric crowding and lowered the thermal stability of the films.     

Preparation and Characterization of Gamma Irradiated Sugar Containing Starch/Poly (Vinyl Alcohol)-Based Blend Films

Blends based on different ratios of starch (35–20%) and plasticizer (sugar; 0–15%) keeping the amount of poly(vinyl alcohol) (PVA) constant, were prepared in the form of thin films by casting solutions. The effects of gamma-irradiation on thermal, mechanical, and morphological properties were investigated. The studies of mechanical properties showed improved tensile strength (TS) (9.61 MPa) and elongation at break (EB) (409%) of the starch-PVA-sugar blend film containing 10% sugar. The mechanical testing of the irradiated film (irradiated at 200 Krad radiation dose) showed higher TS but lower EB than that of the non-radiated film. FTIR spectroscopy studies supported the molecular interactions among starch, PVA, and sugar in the blend films, that was improved by irradiation. Thermal properties of the film were also improved due to irradiation and confirmed by thermo-mechanical analysis (TMA), differential thermo-gravimetric analysis (DTG), differential thermal analysis (DTA), and thermo-gravimetric analysis (TGA). Surface of the films were examined by scanning electron microscope (SEM) image that supported the evidence of crosslinking obtained after gamma irradiation on the film. The water up-take and degradation test in soil of the film were also evaluated. In this study, sugar acted as a good plasticizing agent in starch/PVA blend films, which was significantly improved by gamma radiation and the prepared starch-PVA-sugar blend film could be used as biodegradable packaging materials.     

Novel Polymeric Materials from Biological Oils

A variety of novel polymeric materials ranging from elastomers to tough, rigid plastics have been prepared by the cationic copolymerization of regular soybean oil, low-saturation soybean oil, or conjugated low-saturation soybean oil with various alkene commonomers. Using appropriate compositions and reaction conditions, 70–100% of the soybean oil is covalently incorporated into the cross-linked polymer networks, contributing significantly to cross-linking during copolymerization. The resulting thermosets exhibit thermophysical and mechanical properties that are competitive with those of their petroleum-based counterparts. In addition, good damping and shape memory properties have been obtained by controlling the degree of cross-linking and the rigidity of the polymer backbone. New materials with similar characteristics have also been produced from other biological oils, including tung, and fish oils using the same technique. The new, more valuable properties of these bioplastics suggest numerous promising applications of these novel polymeric materials.     

Preparation and Optimization of Starch/Poly Vinyl Alcohol/ZnO Nanocomposite Films Applicable for Food Packaging

Pollution and destruction of the environment due to the accumulation of non-degradable plastics are some of the most important concerns in the world. A significant amount of this waste is related to the polymers used in food packaging. Therefore, experts in the food industry have been looking for suitable biodegradable alternatives to synthetic polymers. Preparing biocompatible and biodegradable films based on starch is a good choice. In this study, various factors affecting films of starch/polyvinyl alcohol (PVA)/containing ZnO nanoparticles such as the amount of starch, PVA, glycerol, and ZnO were evaluated by response surface methodology (RSM). Film formation by solvent casting method, mechanical properties, swelling, solubility, and water vapor permeability (WVP) were selected as responses of RSM. The results showed that hydrogen bonding interactions between polyvinyl alcohol and starch improved the film formation. The effect of glycerol and PVA content on the mechanical strength was contrary to each other. As the amount of PVA increased, the tensile strength first decreased and then increased. The value of WVP was for all Runs from 0 to 6.77?×?10^??8 g m^??1 s^??1 Pa^??1. Finally, films with high film formation, maximum tensile strength, and high elongation at break, minimum solubility, permeability, and swelling were optimized.

     

Biodegradable Polyesters and Polyamides From Difunctionalized Lauric and Coconut Fatty Acids

In this work, a major fatty acid from coconut oil was used as starting material in preparing biodegradable polymers. Thus, polyesters and polyamides from varying proportions of monomers, hydroxy- and amino- derivatives of lauric acid were synthesized. Initially, the derivatives were prepared by regioselective chlorination of lauric acid, in the presence of ferrous ions in strong acid medium. Subsequent hydroxylation and amination procedures yielded the hydroxy- and amino- derivatives of lauric acid. These monomers were polymerized in a reaction tube by simple polycondensation method at 220–230 °C for 6–8 h without catalyst. Molecular weight determination using –COOH by end group titration and gel permeation chromatography (GPC) gave an average molar mass of 3,000–5,000 g mol⁻¹ with n = 15–25 monomer units. Thermal properties such as glass transition (T_g) and decomposition (T_d) temperatures were obtained using differential scanning calorimetry (DSC). The same processes of synthesis and determinations above were applied to coconut fatty acids, derived from saponification of coconut oil, and resulted to very similar conclusions. A quick biodegradation assay against fungus Aspergillus niger UPCC 4219 showed that the polymers prepared are more biodegradable than conventional plastics such as polypropylene, poly(ethyleneterepthalate) and poly(tetrafluoroethylene) but not as biodegradable as cellulosic (newsprint) paper.     

Compatibilization Improves Performance of Biodegradable Biopolymer Composites Without Affecting UV Weathering Characteristics

With growing interest in the use of eco-friendly composite materials, biodegradable polymers and composites from renewable resources are gaining popularity for use in commercial applications. However, the long-term performance of these composites and the effect of compatibilization on their weathering characteristics are unknown. In this study, five types of biodegradable biopolymer/wood fiber (WF) composites were compatibilized with maleic anhydride (MA), and the effect of accelerated UV weathering on their performance was evaluated against composites without MA and neat biopolymers. The composite samples were prepared with 30 wt% wood fiber and one of the five biodegradable biobased polymer: poly(lactic) acid (PLA), polyhydroxybutyrate (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), Bioflex (PLA blend), or Solanyl (starch based). Neat and composite samples were UV weathered for 2000 h (hours), and characterized for morphological, physical, thermal, and mechanical properties before and after weathering. Compared to composites without MA, composites containing MA grafted polymers exhibited improved properties due to increased interfacial adhesion between the fiber and matrix. Upon accelerated weathering, thermal and mechanical properties of 70% of the samples substantially decreased. Surfaces of all the samples were roughened, and drastic color changes were observed. Water absorption of all the samples increased after weathering exposure. Even though the compatibilization is shown to improve composite properties before weathering, it did not affect weathering of samples, as there were no considerable differences in properties exhibited by the composites with MA and without MA after weathering. The results suggest that compatibilization improves properties of biodegradable biobased composites without affecting its UV degradation properties.     

Aromatic Copolyester-based Nano-biocomposites: Elaboration, Structural Characterization and Properties

Biodegradable polymers are one of the most promising ways to replace non-degradable polymers. But, to be a real alternative to classical synthetic polymers and find applications, biopolymer (biodegradable polymer) properties have to be enhanced. Nano-biocomposites, which are obtained by incorporation of nanofillers into a biomatrix, are an interesting way to achieve these improvements. Modified and unmodified montmorillonites have been introduced into a biodegradable aromatic copolyester, poly(butylene adipate-co-terephthalate) (PBAT). Structural characterization, thermal and mechanical tests have been carried out to understand better the relations between the nanofillers structuring and the final nano-biocomposite properties. Main results show that clay incorporation and the obtained intercalated structures improve PBAT properties (enhanced thermal stability, increased stiffness) and thus may increase the attractiveness of this biopolymer.     

Suspension Polymerization of Poly(l-lactide-co-p-dioxanone) in Supercritical Carbon Dioxide

Biodegradable copolymers of l-lactide(l-LA) and p-dioxanone(PDO) were synthesized in supercritical carbon dioxide (scCO₂) with stannous octoate as the ring-opening catalyst and a fluorocarbon polymer surfactant as an stabilizer. Fine powderous products were achieved when more than 90% (w/w) l-LA was fed. Scanning electron micrographic images and laser diffraction particle size analysis of the products showed the mean diameter of particles greatly increased as the content of PDO increased. The obtained polymers had the number-average molecular weights ranging from 15,000 to 26,000 g mol⁻¹ (polydispersity index ranging from 1.3 to 2.1) according to the gel permeation chromatography measurements. The polymer structure was characterized by NMR spectroscopy, indicating the formation of copolymers. Thermal properties of the obtained polymers investigated using differential scanning calorimetry showed that the morphology of products was directly relevant to the crystallinity of the copolymers. The polymerization of l-LA and PDO copolymers in scCO₂ is also proposed as a novel production technique for high-purity, biodegradable polymers.     

Construction, Characterization and Biological Activity of Chiral and Thermally Stable Nanostructured Poly(Ester-Imide)s as Tyrosine-Containing Pseudo-Poly(Amino Acid)s

In this paper we studied the synthesis of biodegradable optically active poly(ester-imide)s containing different amino acid residues in the main chain. These pseudo-poly(amino acid)s were synthesized by polycondensation of N,N′-(pyromellitoyl)-bis-l-tyrosine dimethyl ester as a diphenolic monomer and two chiral trimellitic anhydride-derived diacid monomers containing s-valine and l-methionine. The direct polycondensation reaction of these diacids with aromatic diol was carried out in a system of tosyl chloride (TsCl), pyridine (Py) and N,N′-dimethylformamide (DMF) as a condensing agent. The structures and morphology of these polymers were studied by FT-IR, ¹H-NMR, powder X-ray diffraction, field emission scanning electron microscopy (FE-SEM), specific rotation, elemental and thermogravimetric analysis (TGA) techniques. TGA profiles indicate that the resulting PEIs have a good thermal stability. Morphology probes showed these polymers were noncrystalline and nanostructured polymers. The monomers and prepared polymers were buried under the soil to study the sensitivity of the monomers and the obtained polymers to microbial degradation. The high microbial population and prominent dehydrogenase activity in the soil containing polymers showed that the synthesized polymers are biologically active and microbiologically biodegradable. Wheat seedling growth in the soil buried with synthetic polymers not only confirmed non-toxicity of polymers but also showed possibility of phyto-remediation in polymer-contaminated soils.     

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.     

Rheological Behavior Under Shear and Non-Isothermal Elongational Flow of Biodegradable Polymers for Foam Extrusion

The production of many items, in particular for food packaging applications, is based on foam extrusion and thermoforming. These operations require the use of polymers which can grant some specific rheological properties, both under shear and elongational flow. In this work, the behavior of some biodegradable polymers [Mater-Bi^® and poly(lactic acid)] under shear and non-isothermal elongational flow was investigated and compared with a traditional, non-biodegradable polymer, in order to assess their suitability for industrial-scale foam extrusion and thermoforming. The rheological characterization evidenced the differences between the different biodegradable polymers and the reference polystyrene (PS), as well as the effect of humidity on their main rheological properties. This can be of great interest in helping to find an optimum solution in replacing PS for the production of food packaging items.     

Water vapor permeability of biodegradable polymers

The water vapor transmission rates (WVTR) of several biodegradable polymers were evaluated to determine their suitability as water-resistant coatings and to understand WVTR better in terms of polymer structure. Values of WVTR at 25‡C ranged from 13 to 2900 g/m² /day and increased in the order PHBV PLA (cryst.) PLA (amorph.) PCL Bionolle BAK 1095 CAP CA. Values of WVTR were positively correlated with higher polymer solubility parameters, lower crystallinities, and higher free volumes. Although the WVTR of biodegradable polymers are much higher than those of good barrier materials such as low-density polyethylene, they are sufficient for short-term (hours to days) protection of polysaccharide-based materials against water. Product names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable.     

Biomass Carbon Ratio of Polymer Composites Measured by Accelerator Mass Spectrometry

The evaluation method of biomass carbon ratio of polymer composite samples including organic and inorganic carbons individually was investigated. Biodegradable plastics and biobased plastics can have their mechanical properties improved by combining with inorganic fillers. Polymer composites consisting of biodegradable plastics and carbonate were prepared by two different methods. Poly(lactic acid) (PLA) composite was prepared by synthesis from l-lactide with catalyst and calcium carbonate (CaCO₃) powders from lime. Poly(butylene succinate) (PBS) composite was prepared by hot-pressing the mixture of PBS powder and CaCO₃ powders from oyster shells. The mechanical properties of composite samples were investigated by a tensile test and a compression test using an Instron type mechanical tester. Tensile test with a dumbbell shape specimen was performed for PBS composite samples and compression test with a column shape specimen for PLA composite samples. Strength, elastic modulus and fracture strain were obtained from the above tests. Biomass carbon ratio is regulated in the American Standards for Testing and Materials (ASTM). In ASTM standards on biomass carbon ratio, it is required that carbon atoms from carbonates, such as CaCO₃, are omitted. Biomass carbon ratio was evaluated by ratio of ¹⁴C to ¹²C in the samples using Accelerator Mass Spectrometry (AMS). The effect of pretreatment, such as oxidation temperature and reaction by acid, on results of biomass carbon ratio was investigated. Mechanical properties decrease with increasing CaCO₃ content. The possibility of an evaluation method of biomass carbon ratio of materials including organic and inorganic carbons was shown.