Anaerobic Biodegradation of Blends Based on Polyvinyl Alcohol

The presented work deals with blends composed of polyvinyl alcohol (PVA) and biopolymers (protein hydrolysate, starch, lignin). PVA does not belong to biologically inert plastics but its degradation rate (particularly under anaerobic conditions) is low. A potential solution to the issue problem lies in preparation of blends with readily degradable substrates. We studied degradation of blow-molded films made of commercial PVA and mentioned biopolymers in an aqueous anaerobic environment employing inoculation with digested activated sludge from the municipal wastewater treatment plant. Films prepared in the first experimental series were to be used for comparing biodegradation of blends modified with native or plasticized starch; in this case effect of plasticization was not proved. The degree of PVA degradation after modification with native or plasticized starch increases in a striking and practically same manner already at a starch level as low as approximately 5 wt.%. Films of the second experimental series were prepared as additionally modified with protein hydrolysate and lignin. Only lignin-modified samples exhibited a somewhat lower degree of biodegradation but regarding the measure of lignin present in blend this circumstance is not essential. Level of biodegradation with all discussed films differed only slightly—within range of experimental error.     

Extruded Cornstarch-Glycerol-Polyvinyl Alcohol Blends: Mechanical Properties, Morphology, and Biodegradability

Elongation properties of extruded cornstarch were improved by blending with glycerol. Further blending of starch-glycerol with polyvinyl alcohol (PVOH) resulted in significant improvements in both tensile strength (TS) and elongation at break. Samples of starch-glycerol without PVOH equilibrated at 50% relative humidity had a TS of 1.8 MPa and elongation of 113%, whereas those containing PVOH had a TS and elongation of 4 MPa and 150%, respectively. Dynamic mechanical analysis (DMA) of starch-glycerol-PVOH blends showed that decreases in glass transition temperatures (T _g values) were proportional to glycerol content. Scanning electron microscopy (SEM) of fractured surfaces revealed numerous cracks in starch-glycerol (80:20) samples. Cracks were absent in starch-glycerol (70:30) samples. In both blends, many starch granules were exposed at the surface. No exposed starch granules were visible in blends with added PVOH. Starch-glycerol samples incubated in compost lost up to 70% of their dry weight within 22 days. Addition of PVOH lowered both the rate and extent of biodegradation.     

Effect of Oxidized Starch on Morphology,Rheological and Tensile Properties of Low-Density Polyethylene/Linear Low-Density Polyethylene/Thermoplastic Oxidized Starch Blends

In this work, morphology, rheological and tensile properties of low-density polyethylene/linear low-density polyethylene/thermoplastic oxidized starch (LDPE/LLDPE/TPOS) blends are studied. The blends of LDPE/LLDPE (70/30, w/w) containing 0–20 wt% TPOS in the presence of 3 wt% of PE-grafted maleic anhydride (PE-g-MA) as a compatibilizer are prepared by a twin screw extruder and then converted to appropriate thin films using an extrusion film blowing machine. Scanning electron microscopic images show that there is a relative good dispersion of oxidized starch particles in PE matrices. However, as TPOS content in the blends increases, the starch particle size increases too. The rheological analyses indicate that TPOS can decrease the elasticity and viscosity of the blends. The LDPE/LLDPE/TPOS blends show power-law behavior and as the TPOS content increases the power-law exponent (n) and consistency index (K) decrease. The ultimate tensile strength and elongation at break of the final blend films reduce, when TPOS content increases from 5 to 20 wt%. However, the required mechanical properties for packaging applications are achieved when 10 wt% oxidized starch is added, according to ASTM D4635.     

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.     

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.     

Biodegradability and Thermal Properties of Novel Natural Rubber/Linear Low Density Polyethylene/Thermoplastic Starch Ternary Blends

This work aimed to prepare biodegradable thermoplastic elastomers based on NR/LLDPE/TPS ternary simple blends to achieve some exclusive properties, i.e., good biodegradability in terms of water absorption and weight loss after burial, together with reasonable mechanical and thermal properties. A comparative study on biodegradability and other related properties of NR/LLDPE binary and NR/LLDPE/TPS ternary blends was performed. It was found that increasing the TPS proportion decreased storage modulus and complex viscosity. In addition, the size of dispersed TPS domains in the NR/LLDPE co-continuous matrix increased with TPS proportion, while the mechanical properties in terms of 100% moduli, tensile strength, elongation at break, and hardness decreased. This might be attributed to decreased interfacial adhesion with increasing size of TPS domains. Furthermore, increasing the TPS loading in the blend reduced the temperatures for 5 or 50% mass loss (T₅ or T₅₀) and the degradation temperature (T _d ). However, the biodegradability improved, in terms of increased water absorption and weight loss after burial in soil, with the loading level of TPS.     

Effect of Curing Temperature on Mechanical Properties of Bio-phenolic/Epoxy Polymer Blends

Journal of Polymers and the Environment - Nowadays, researchers continue studies for alternative materials to replace the redundant petroleum-based products. The combination of various polymer...     

Moisture Sorption Characteristics of Microbially Produced Polysaccharide and Polyvinyl Alcohol Blends

Moisture sorption characteristics of microbial polysaccharide (Ps.C101) from Pseudomonas caryophilli and polyvinyl alcohol (PVA) blends have been carried out at 27°C for water activity from 0.1 to 0.9. The sorption data was used to fit six different sorption isotherm models proposed in literature. The model constants were determined by linear fitting of the sorption equations. The ranges of applicability of water activity for isotherm models reported in this paper lie in between 0.1 and 0.4 for Brunaur–Emmet–Teller (BET) model (monolayer), and in between 0.2 and 0.9 for other models. The value of the coefficient of determination (R² = 0.97 ± 0.02) confirms the applicability of the equations studied.     

Effect of the Fe2O3/TiO2 Nanoparticles on the Structural,Mechanical, Electrical Properties and Antibacterial Activity of the Biodegradable Chitosan/Polyvinyl Alcohol Blend for Food Packaging

Journal of Polymers and the Environment - As the request for ready-made food grows, it’s more important than ever to develop effective antimicrobial food packaging materials to assure...     

Rheology,Morphology, Crystallization Behaviors,Mechanical and Thermal Properties of Poly(lactic acid)/Polypropylene/Maleic Anhydride-Grafted Polypropylene Blends

The rheologies, morphologies, crystallization behaviors, mechanical and thermal properties of poly(lactic acid) (PLA)/polypropylene (PP) blends and PLA/PP/maleic anhydride-grafted PP (MAPP) blends were investigated. The results showed that the complex viscosities of PLA/PP blends were between those of neat PLA and neat PP, and MAPP had a thinning effect on those of the blends. PLA/PP blends exhibited the distinct phase separation morphologies due to the limited partial miscibility of the blend components. MAPP slightly improved the miscibility between PLA and PP. Both the cold crystallization of PLA component and melt crystallization of PP component were enhanced, probably because PLA and PP were reciprocal nucleating agents. The tensile strength and flexural modulus decreased, while the tensile strain at break and heat deflection temperature (HDT) increased with the increasing PP content. MAPP had the positive effects on the notched impact strength and HDT of PLA-rich blends and also increased the flexural modulus of the binary blends. The thermal stability of the blend was improved by PP, and the incorporation of MAPP further enhanced the thermal stability.     

Evaluation of the Biodegradability of Polyvinyl Alcohol/Starch Blends: A Methodological Comparison of Environmentally Friendly Materials

Polyvinyl alcohol (PVA) and starch are both biodegradable polymers. These two polymers can be prepared as biodegradable plastics that are emerging as one of the environmental friendly materials available now. In this study, after reacting with sodium trimetaphosphate (STMP), modified corn starch was blended with PVA in different ratios by a barbender. Test samples were prepared for mechanical and thermal properties measurements. The surface roughness and morphology of fractured surface of the samples were observed by an atomic force microscopy (AFM) and scanning electron microscope (SEM) measurements. Aqueous degradation by enzyme, water absorption and biodegradability behavior were evaluated for the degradability. The biodegradability of these materials was followed by bio-reactivity kinetics models. Results showed that the addition of modified starch could enhance its water uptake. With an addition of 20 wt% of modified starch, the blend had a maximum weight loss during enzymatic degradation. It was found that the degradability was enhanced with the addition of the starch. Analyzing the results of the biodegradability based on the kinetic models, the growth rate of the microorganism was found to be increasing with the increase of the content of starch in the PVA/starch blends in the first order reaction fashion. In our biodegradability analysis, i.e., based on the China national standards (CNS) 14432 regulations, we estimated the decomposition behavior based on the mentioned first order reaction. We found that the PVA/starch blends would take 32.47, 16.20 and 12.47 years to degrade by 70% as their starch content 0, 20 and 40 wt%, respectively.     

Mechanical and Thermal Properties of Biocomposites Based on Polyethylene from Renewable Resources Modified with Ionic Liquids

Journal of Polymers and the Environment - Biocomposites based on polyethylene from renewable resources derived from sugar cane as raw material were modified with phosphonium ionic liquids....     

Effects of Compatibilizer and Thermoplastic Starch (TPS) Concentration on Morphological,Rheological, Tensile,Thermal and Moisture Sorption Properties of Plasticized Polylactic Acid/TPS Blends

The blends of polylactic acid plasticized with acetyl tributyl citrate (P-PLA) and thermoplastic wheat starch (TPS) were prepared by a co-rotating twin screw extruder and the effect of maleic anhydride grafted PLA (PLA-g-MA) content as reactive compatibilizer on blends compatibility through morphological, rheological and tensile properties of the blends was investigated. Considerable improvement in properties of P-PLA/TPS (70/30 w/w) blend with incorporating the optimum PLA-g-MA content of 4 phr was achieved as this blend exhibited better morphological and rheological properties with an increase by 158 and 276% in tensile strength and elongation at break, respectively, compared to the uncompatibilized blend. Also the thermal stability and moisture sorption properties of the blends as effected by TPS content were studied. Decreasing in thermal stability and increasing in equilibrium moisture content of the blends were observed with progressively increasing of TPS content. For prediction the moisture sorption behaviour of blends with various TPS contents at different relative humidity, the moisture sorption isotherm data were modeled by GAB (Guggenheim–Anderson–de Boer) model.     

Mechanical Properties and Morphology of Polypropylene/Poly(ethylene-co-octene) Blends

The polypropylene (PP)/poly(ethylene-co-octene) (POE) blends was prepared by means of a twin screw extruder in a range of temperature from 185 to 195 °C. The mechanical properties including tensile, flexural and impact of the PP/POE blends were measured at room temperature to identify the effect of the POE content on the mechanical properties. It was found that the Young’s modulus, tensile strength and tensile elongation at break decreased nonlinearly with increasing the POE weight fraction. While the V-notched and unnotched impact fracture strength increased nonlinearly with an increase of the POE weight fraction. The flexural modulus and strength decreased roughly linearly with increasing the POE weight fraction. Furthermore, the impact fracture surface of the blends was observed by using a scanning electronic microscope and the toughening mechanisms were discussed.     

Effect of Nanoscale SiO<Subscript>2</Subscript> and TiO<Subscript>2</Subscript> as the Fillers on the Mechanical Properties and Aging Behavior of Linear Low-Density Polyethylene/Low-Density Polyethylene Blends

Linear low-density polyethylene (LLDPE) was blended with low-density polyethylene (LDPE) at a fixed ratio (80 wt LLDPE and 20 wt %LDPE) and filled with nanoparticles of SiO₂ and TiO₂ at a ratio up to wt 5%, so as to develop the polymeric composites suitable to preparing the agricultural micro-irrigation pipes having good environmental adaptability. These compounds were blended using calcium stearate, polyethylene wax, and titanate coupling agent as the auxiliary dispersants, and ethylene-vinyl acetate copolymer (EVA) as the toughness improver. The LLDPE/LDPE composites filled with the nanoparticles were extruded and injected to prepare the composites specimens for the performance evaluations and micro-irrigation pipe field test. The mechanical properties, thermostability, and processibility of the injected composites were investigated. The effect of heating in an oven and irradiating by ultraviolet on the mechanical properties of the composites was explored. The environmental adaptability of the micro-irrigation pipes made of the filled LLDPE/LDPE composites was evaluated making use of long-term outdoor field test in northwest China where the arid and harsh natural conditions are of great concerns. It was found that the LLDPE/LDPE blend with the LLDPE mass fraction fixed as 80% showed balanced mechanical and thermal properties and flexibility, and was suitable to be used as the basic resin matrix. The incorporation of nano-TiO₂ contributed to effectively improving the resistance to heating and ultraviolet irradiation of the composites. The composite made from 91% basic resin matrix, 6% EVA, and 3% mixed nano-SiO₂ and TiO₂, showed balanced comprehensive properties. The micro-irrigation pipes made of this filled LLDPE/LDPE composite had good environmental adaptability and service behavior in a three-year field test and were suitable to be used in arid area.     

The Effect of Nanoclays on the Properties of PLLA-modified Polymers Part 1: Mechanical and Thermal Properties

Organically modified montmorillonite clays were incorporated at a 5% loading level into film grade of poly-L-lactic acid (PLLA) using a variety of masterbatches based on either semi-crystalline or amorphous poly-(lactic acid), as well as biodegradable aromatic aliphatic polyester. The PLLA masterbatches and compounded formulations were prepared using a twin screw compounding extruder, while the films were prepared using a single screw cast film extruder. The thermal and mechanical properties of the films were examined in order to determine the effect of the clay and different carriers on the polymer–clay interactions. In the optimal case, when a PLLA-based masterbatch was used, the tensile modulus increased by 30%, elongation increased by 40%, and the cold crystallization temperature decreased by 15 °C, compared to neat PLLA. The properties improvement of PLLA films containing nano clays demonstrated the possibility to extend the range of biodegradable film applications, especially in the field of packaging.     

Molding Method, Thermal and Mechanical Properties of Jute/PLA Injection Molding

Natural composites have been important materials system due to preservation of earth environments. Natural fibers such as jute, hemp, bagasse and so on are very good candidate of natural composites as reinforcements. On the other hand regarding matrix parts thermosetting polymer and thermoplastic polymer deriver form petrochemical products are not environmental friendly material, even if thermoplastic polymer can be recycled. In order to create fully environmental friendly material (FEFM) biodegradable polymer which can be deriver from natural resources is needed. Therefore poly(lactic acid) (PLA) polymer is very good material for the FEFM. In this paper jute fiber filled PLA resin (jute/PLA) composites was fabricated by injection moldings and mechanical properties were measured. It is believable that industries will have much attention to FEFM, so that injection molding was adopted to fabricate the composites. Long fiber pellet fabricated by pultrusion technique was adopted to prepare jute/PLA pellet. Because it is able to fabricate composite pellets with relative long length fibers for injection molding process, where, jute yarns were continuously pulled and coated with PLA resin. Here two kinds of PLA materials were used including the one with mold releasing agent and the other without it. After pass through a heated die whereby PLA resin impregnates into the jute yarns and sufficient cooling, the impregnated jute yarns were cut into pellets. Then jute/PLA pellets were fed into injection machine to make dumbbell shape specimens. In current study, the effects of temperature of PLA melting temperature i.e. impregnation temperature and the kinds of PLA were focused to get optimum molding condition. The volume fractions of jute fiber in pellet were measured by several measuring method including image analyzing, density measurement and dissolution methods. Additionally, thermal and mechanical properties were investigated. It is found that 250° is much suitable for jute/PLA long fiber pultrusion process because of its less heat degradation of jute, better impregnation, acceptable mechanical property and higher production efficiency. Additionally the jute fibers seem much effective to increase deflection temperature under load, tensile modulus and Izod strength.