The Effect of Gamma and Electron Beam Irradiation on the Biodegradability of PLA Films

Biodegradation of poly(lactic) acid (PLA) has been studied extensively, but there is only limited knowledge about the effect of irradiation sterilization on its biodegradability. The aim of this work was to examine the aerobic biodegradation of gamma and electron beam irradiated PLA films along with the effects of aging (3, 6, and 9 months of storage) using a direct measurement respirometric system. Commercial PLA film was exposed to a simulated aerobic compost environment, and its mineralization was 96 % at day 85. Gamma and electron beam irradiation affected the biodegradation of the post-irradiated PLA film. Aging irradiated PLA had some potential to increase the biodegradation rate, as the average value of mineralization after 9 months of storage was higher than for the non-irradiated PLA. Comparison of the effect of storage time on the biodegradability of PLA showed a significant increase in biodegradation of the gamma irradiated PLA after 3 months (70 %) and 9 months of storage (130 %). Similarly, there was a significant difference in the biodegradation of electron beam irradiated PLA between 3 months (68 %) and 9 months of storage (120 %). Due to the priming effect, the percent mineralization of gamma irradiated and E-beam irradiated PLA after 9 months of storage was greater than 100 %. Both non-irradiated and irradiated PLA films can be considered biodegradable plastics since they showed mineralization percentage larger than 90 % of that of the positive control at the end of the test period.     

GC-MS在电子束辐照降解甲苯中的应用

用甲苯作为挥发性有机化合物的代表物质,建立了活性炭吸附-二硫化碳解吸气相色谱-质谱分析方法,对电子束辐照甲苯的静态实验和动态实验进行了定性、定量分析。实验结果表明：电子束辐照能有效地降解甲笨,其降解率随吸收剂量的增加而增大;同时,甲苯降解过程中也会生成部分有毒有害物质。该分析方法的检出限为0．02mg／L,工作曲线的线性范围为10～1000mg／L,相关系数为0．9998,活性炭吸附、解吸甲苯的加标回收率大于90％。     

电子束辐照分解甲苯的初步实验研究

进行了电子束辐照分解甲苯的静态实验研究,实验结果表明,电子束辐照能够有效地分解甲苯,在850keV、11kGy电子束的辐照下,初始质量浓度为1 000~3 000m g/m3的甲苯去除率可以达到77%以上,且甲苯去除率随吸收剂量的增加而提高。甲苯辐照分解的主要产物是苯甲醛和甲酸,此外还有少量苯、苯酚等。进一步验证了.OH在甲苯分解中的重要作用。     

Rheological and Thermal Properties of Levan from Bacillus mojavensis

Journal of Polymers and the Environment - Media composition and culture conditions for levan production by Bacillus mojavensis (BM-levan) were optimized using Plackett–Burman and Box-Behnken...     

The Use of Interfacial Blend to Increase the Adhesion Properties of Natural Rubber/Polyvinylalcohol Multilayer Using Electron Beam Irradiation

Multilayers of natural rubber (NR) and polyvinylalcohol (PVA) were processed by casting natural rubber latex (NRL) then PVA with varying layer thickness. Adhesion between NR and PVA was found to be very poor, as determined with the peel method. The films of interfacial blend were composed of NRL and PVA having different ratios as a layer between NR/PVA layer, possessing good adhesion and exhibited one mechanical phase in tensile-elongation at break tests. The result of adhesion was confirmed by thermogravimetric analysis and scanning electron microscopy study. Also, adhesion was too strong for delamination at the interface when the unit of three layers NR/blend/PVA was irradiated at 25 kGy. To probe the effect of the adhesion difference on mechanical behavior and deformation of NR/blend/PVA layers at dry and wet conditions, the peel strength was examined as a function of layer thickness and aging time. The results indicated that the interfacial blend, irradiation process and film thickness were the key parameters affecting adhesion of NR/PVA layer.     

Modification of Thermo-Mechanical Properties of Recycled PET by Vinyl Acetate (VAc) Monomer Grafting Using Gamma Irradiation

Vinyl acetate (VAc) monomer of different percentage was grafted onto the recycled polyethylene terephthalate (r-PET) films using gamma irradiation. The properties of these modified films were characterized by Fourier transform infrared spectroscopy (FTIR), mechanical properties testing (Tensile strength, Elongation at break), dynamic mechanical analysis (DMA) and thermo-gravimetric analysis (TGA). The Tensile Strength (TS) of the modified PET film increased by 132.25?% to the highest value of 50.12 MPa at 15% VAc monomer concentration at 3 kGy gamma dose, while the elongation at break (EB) decreased by 31.83?%. FTIR was used to investigate the molecular interaction of the modified films. TGA revealed that curve of the modified PET film shifted toward higher temperature region by 95?°C, which is very close to that of PET film made from virgin flakes. The results indicate that modified PET films of better mechanical and thermal properties were successfully prepared using VAc monomer grafting by gamma irradiation technique.     

Improving the Rheological and Mechanical Properties of Recycled PET Modified by Macromolecular Chain Extenders Synthesized by Controlled Radical Polymerization

In this work, a series of reactive copolymers of glycidyl methacrylate (G), styrene (S) and acrylonitrile (AN), were synthesized through reversible addition-fragmentation chain transfer polymerization and evaluated as macromolecular chain extenders in reactive extrusion of recycled poly(ethylene terephthalate) (rPET). The results obtained indicate that the addition of the reactive copolymers as chain extenders modifies the chain conformation in rPET causing low crystallization rate and low crystallinity. The physical and rheological properties (melt flow and intrinsic viscosity) of chain-extended rPET improved, rendering better processability. rPET modified with polymeric chain extenders shows improved rheological properties (complex viscosity, storage and loss modulus) and also displays higher elongation at break and impact properties as the GMA content in the chain extenders increase.     

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.     

Thermal and Rheological Properties of Commercial-Grade Poly(Lactic Acid)s

Poly(lactic acid) is the subject of considerable commercial development by a variety of organizations around the world. In this work, the thermal and rheological properties of two commercial-grade poly(lactic acid)s (PLAs) are investigated. A comparison of the commercial samples to a series of well-defined linear and star architecture PLAs provides considerable insight into their flow properties. Such insights are valuable in deciding processing strategies for these newly emerging, commercially significant, biodegradable plastics. Both a branched and linear grade of PLA are investigated. The crystallization kinetics of the branched polymer are inferred to be faster than the linear analog. Longer relaxation times in the terminal region for the branched material compared to the linear material manifests itself as a higher zero shear rate viscosity. However, the branched material shear thins more strongly, resulting in a lower value of viscosity at high shear rates. Comparison of the linear viscoelastic spectra of the branched material with the spectra for star PLAs suggests that the branched architecture is characterized by a span molecular weight of approximately 63,000 g/mol. The present study conclusively demonstrates that a wide spectrum of flow properties are available through simple architectural modification of PLA, thus allowing the utilization of this important degradable thermoplastic in a variety of processing operations.     

Mechanical and Thermal Properties of PLLA/PCL Modified Clay Nanocomposites

Poly(l-lactic acid) (PLLA)/poly(caprolactone) (PCL) and two types of organoclay (OMMT) including a fatty amide and ocatdecylamine montmorillonite (FA-MMT and ODA-MMT) were employed to produce polymer nanocomposites by melt blending. Materials were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), elemental analysis, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Mechanical properties were also investigated for these nanocomposites. The nanocomposites showed increasing mechanical properties and thermal stability. XRD results indicated that the materials formed nanocomposites. SEM morphology showed that increasing content of OMMT reduced the domain size of phase separated particles. TEM outcomes have confirmed the intercalated type of nanocomposite. Additionally, a solution casting process has been used to prepare these nanocomposites and characterized to compare these results with the above process.     

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.     

Properties of Biocomposite Films From PLA and Thermally Treated Wood Modified with Silver Nanoparticles Using Leaf Extracts of Oriental Sweetgum

Journal of Polymers and the Environment - The technological, thermal, and antimicrobial properties of biocomposite films produced from polylactic acid (PLA) and thermally treated wood flour with in...     

Melt Strength and Rheological Properties of Biodegradable Poly(Lactic Aacid) Modified via Alkyl Radical-Based Reactive Extrusion Processes

Poly(lactic acid) (PLA) has been modified using twin-screw reactive extrusion to improve its melt properties and crystallinity. In this work lauroyl peroxide was used as an alkyl free radical source, abstracting hydrogen atoms from the PLA backbone leading to branching and chain extension reactions. Once the linear viscoelastic region was determined for these polymers, changes in dynamic rheology (dynamic viscosity real and loss modulus) were measured. Gel permeation chromatography showed that the molecular weight and polydispersity increased to a maximum with the addition of 1.00 and 0.50?wt% peroxide, respectively. Low temperature ?? transitions in dynamical mechanical thermal traces gave further evidence that branching had also occurred. G?ttfert Rheotens measurements showed a three fold increase in melt strength due to both increased chain length and branching. Thermal analysis showed the level of crystallisation had decreased also possibly due to branching. Reductions in crystallinity and improved melt strength are known to be critical for film and foam formation.     

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....     

Rheology,Morphology and Thermal Properties of a PLA/PHB/Clay Blend Nanocomposite: The Influence of Process Parameters

Journal of Polymers and the Environment - The effect of process parameters on the final properties of a poly-lactic acid (PLA) and polyhydroxybutyrate (PHB) polymer blend filled with nanoclays was...     

Study on the Physico-mechanical Properties of Photo-cured Chitosan Films with Oligomer and Acrylate Monomer

Chitosan films were prepared from dried prawn shell via chitin and then tensile properties like tensile strength (TS) and elongation at break (Eb) of the films were evaluated. Six formulations were developed using methyl methacylate (MMA) monomer and aliphatic urethane diacrylate oligomer (M-1200) in methanol along with photoinitator (Darocur-1664). Then the films were soaked in the formulations and irradiated under UV radiation at different doses for the improvement of physico-mechanical properties of chitosan films. The cured films were characterized by measuring TS, Eb, polymer loading (PL), water absorption and gel content properties. The formulation containing 43% MMA and 15% oligomer in methanol solution showed the best performance at 20th UV pass for 4 min soaking time.     

Organically Modified Nanoclay and Aluminum Hydroxide Incorporated Bionanocomposites towards Enhancement of Physico-mechanical and Thermal Properties of Lignocellulosic Structural Reinforcement

A range of bio-nanocomposites were prepared by incorporation of organo modified montmorillonite nanoclay (OMMT) with or without use of aluminum hydroxide (Al(OH)₃) within polylactic acid (PLA) solution. Furthermore, the solution was employed for modification of ligno-cellulosic (jute) fabric structural reinforcements. The successful incorporation of nanofillers within the host polymer, polylactic acid (PLA) was confirmed by Fourier-transform infrared spectroscopy (FT-IR). Water uptake and swelling behaviour studies revealed that the water uptake and swelling ratio of bio-composites reduced significantly as compared to pristine jute fabric, whereas upon incorporation of OMMT and Al(OH)₃, the water barrier properties reduced even further in the developed bio-nanocomposites. The flexural strength of the bio-nanocomposites also showed improved mechanical and dimensional stability. Synergistic effects of OMMT and Al(OH)₃ were observed in enhancing the aforementioned physico-mechanical properties. Scanning electron microscopy (SEM) studies revealed microstructural details of developed samples. Similarly, the thermo-gravimetric analysis and linear burning rate studies of Al(OH)₃ treated bio-nanocomposite materials revealed enhanced thermal resistance and reduced flammability respectively compared to both pristine woven jute fabric and fabrics treated with PLA alone or those without Al(OH)₃. From the above results it can safely be said that the bio-nanocomposite material can be a prospective candidate for development of flame retardant biopackaging.     

A Comparison of Modified and Unmodified Cellulose Nanofiber Reinforced Polylactic Acid (PLA) Prepared by Twin Screw Extrusion

The goal of this work was to evaluate the effect of chemical modification of cellulose nanofibers (CNF) on the properties of polylactic acid (PLA) nanocomposites. Acetylated nanofibers (ACNF), with degree of substitution 1.07, were isolated from acetylated kenaf fibers by mechanical treatments. Acetylated nanofibers showed more hydrophobic properties compared to non-acetylated ones. The results showed that both crystallinity and thermal stability of acetylated nanofibers were lower than non-acetylated ones. The nanocomposites were prepared by premixing two PLA master batches, one with a high concentration of ACNF and the second with CNF. These were diluted to final concentrations (5?wt%) during the extrusion. The morphology studies of PLA and its nanocomposites showed nanofiber aggregates in both materials. The results showed that the tensile and dynamic mechanical properties were enhanced for both acetylated and non-acetylated nanocomposites compared to the neat PLA matrix while no significant improvement was observed for the acetylated nanocomposites compared to non-acetylated ones. However, the storage modulus increased slightly for acetylated nanocomposites compared to non-acetylated ones.