Effects of Diisocyanate and Polymeric Epoxidized Chain Extenders on the Properties of Recycled Poly(Lactic Acid)

Increasing demand in the use of poly(lactic acid) (PLA) leads to a debate about using potential foodstuffs for plastic production and a moral issue when starvation problem is taken into account. One of the solutions is recycling of PLA; however, recycling results in property losses during melt processing due to low thermal stability of PLA. This study focuses on using chain extenders to offset thermal degradation of recycled PLA. The effects of a diisocyanate and a polymeric epoxidized chain extender on the properties of the recycled poly(lactic acid) were investigated. In order to mimic the recycling process, PLA was subjected to thermo-mechanical degradation using a laboratory scale compounder. Chain extender type, loading and mixing time were investigated. On-line rheology and intrinsic viscosity measurements of PLA before and after chain extension confirmed that the molecular weight increased. Dynamic mechanical analysis, rheology and tensile tests revealed that the chain extenders led to a significant increase in modulus, strength and melt-viscosity. It was found that diisocyanate had slightly higher and faster chain extension reactivity than polymeric extender. Differential scanning calorimetry results showed an increase in the crystallization temperature due to the branched and extended chain structure.     

Flammability Properties of Virgin and Recycled Polycarbonate (PC) and Acrylonitrile–Butadiene–Styrene (ABS) Recovered from End-of-Life Electronics

Acrylonitrile–Butadiene–Styrene (ABS), Polycarbonate (PC) and their alloys are widely used in automotive industry, computer and equipment housings. With increasing disposal of end-of-life electronic equipment, there is also an increased demand for recycling of these materials so that they do not pose environmental challenge as solid waste. One of the recycling approaches is mechanical recycling of these thermoplastics where recycled plastic is melt blended with virgin materials to obtain a high quality product. Besides obtaining desirable mechanical properties, such blends should also conform to fire safety standards. In this work, a series of blends were prepared using PC and ABS recovered from discarded computers and virgin materials using a twin-screw extruder. Their flammability properties were evaluated using burner flammability tests and Ohio State University (OSU) release rate tests. It was found that the extinguishing time, burning extent and weight loss appears to progressively decrease with the addition of both virgin or recycled PC to virgin or recycled ABS. It was also seen that the addition of the 70% of PC, virgin or recycled, to ABS virgin or recycled, appears to significantly decrease heat release and smoke evolution. The results of this study indicate that recycled polycarbonate can be used as an additive for virgin or recycled ABS, as a means of giving flame resistance to ABS in high-value applications. This result is significant when related to the result obtained by a separate study indicating that up to 25% of recycled material can be used without degradation of mechanical properties in the presence of 15% short glass fiber reinforcement.     

Life Cycle Assessment of Poly(Lactic Acid) (PLA): Comparison Between Chemical Recycling,Mechanical Recycling and Composting

This paper presents a life cycle assessment (LCA) comparing three forms of poly(lactic acid) (PLA) disposal: mechanical recycling, chemical recycling and composting. The LCA data was taken from lab scale experiments for composting and hydrolysis steps. Polymerization data in chemical recycling was obtained from computer simulation. Mechanical recycling data from lab scale were combined with the data from a plastics commercial mechanical recycling plant. The analysis considered two different product systems based on the input of the recycled PLA in the product system. Considering the categories: climate change, human toxicity and fossil depletion, the LCA showed that mechanical recycling presented the lowest environmental impact, followed by chemical recycling and composting. Among the forms of recycling, the most important input was the electricity consumption.     

Chemically Functionalized Plant Fibers and Carbon Nanotubes for High Compatibility and Reinforcement in Polylactic Acid (PLA) Composite

In this study, surface modification is used to improve the compatibility of Kenaf fibers (KFs) and multi-walled carbon nanotubes (MWCNTs) in a polylactic acid (PLA) matrix, as well as to enhance the mechanical properties. Through the use of a silane coupling agent, the KF is grafted with functional groups to generate a chemical bond with the PLA; the modified KF shows high compatibility in the PLA matrix. Compared to the bare PLA, the optimal KF/MWCNT/PLA composite (PC1F30-OX) shows increases of 58% in tensile strength, and 113% in impact strength. A small addition of MWCNTs (1 wt%) dramatically improves the antistatic ability by lowering the surface resistance to 3.47 GΩ. With the addition of hydrophilic KF into the PLA, the composite becomes much more environmentally friendly, and the biodegradation rate can be controlled by the amount of KF added. The addition of hydrophilic KF allowed the composite to accommodate more enzyme to hasten the biodegradation; almost complete decomposition occurred after 11 weeks.     

Characterization of composites based on expanded polystyrene wastes and wood flour

This paper aims to evaluate the potential for the use of recycled expanded polystyrene and wood flour as materials for the development of wood plastic composites. The effects of wood flour loading and coupling agent addition on the mechanical properties and morphology of wood thermoplastic composites were examined. In addition, a methodology for the thermo-mechanical recycling of expanded polystyrene waste was developed. The results show that the mechanical properties decreased as the wood flour loading increased. On the other hand, the use of poly(styrene-co-maleic anhydride), SMA, as a coupling agent improved the compatibility between the wood flour and polystyrene matrix and the mechanical properties subsequently improved. A morphological study revealed the positive effect of the coupling agent on the interfacial bonding. The density values obtained for the composites were compared with the theoretical values and showed agreement with the rule of mixtures. Based on the findings of this work, it appears that both recycled materials can be used to manufacture composites with high mechanical properties and low density.     

Hydrothermal recycling of waste and performance of the recycled wooden particleboards

Recycling today constitutes the most environmentally friendly method of managing wood waste. A large proportion of the wood waste generated consists of used furniture and other constructed wooden items, which are composed mainly of particleboard, a material which can potentially be reused. In the current research, four different hydrothermal treatments were applied in order to recover wood particles from laboratory particleboards and use them in the production of new (recycled) ones. Quality was evaluated by determining the main properties of the original (control) and the recycled boards. Furthermore, the impact of a second recycling process on the properties of recycled particleboards was studied. With the exception of the modulus of elasticity in static bending, all of the mechanical properties of the recycled boards tested decreased in comparison with the control boards. Furthermore, the recycling process had an adverse effect on their hygroscopic properties and a beneficial effect on the formaldehyde content of the recycled boards. The results indicated that when the 1st and 2nd particleboard recycling processes were compared, it was the 2nd recycling process that caused the strongest deterioration in the quality of the recycled boards. Further research is needed in order to explain the causes of the recycled board quality falloff and also to determine the factors in the recycling process that influence the quality degradation of the recycled boards.     

Effects of Electron-Beam Irradiation and Ultraviolet Light (365 nm) on Polylactic Acid Plastic Films

Strips of Ca-I [polylactic acid (PLA) monolayer plastic films from Cargill Dow Polymers LLC, Minnetonka, MN] cut in the machine and nonmachine directions were irradiated with an electron beam using a CIRCLE III Linear Accelerator (MeV Industries S.A., Jouy-en-Josas, Cedex, France). The effects of 33-kGy irradiation on the physical properties of the Ca-I strips were studied. In addition, the effects of ultraviolet (UV) light (365-nm) illumination on the degradation of three PLA plastic films, Ch-I (PLA monolayer plastic films from Chronopol, Golden, CO), GII (PLA trilayer plastic films from Cargill Dow Polymers LLC), MN), and Ca-I (PLA monolayer plastic films from Cargill Dow Polymers LLC) were analyzed by a modified ASTM D5208-91 method. Results showed that irradiation had decreased the weight-average molecular weight (M _w), stress at break, percentage of elongation, and strain energy of Ca-I by 35.5, 26.7, 32.3, and 44.8%, respectively (P < 0.01). The shelf life of the irradiated Ca-I strips at 5°C and <20 ± 5% RH was about 6 months. The degradation rate of Ch-I, GII, and Ca-I with no UV light treatment at 55°C and 10% RH was 2512, 5618, and 3785 M _w/week, respectively. Under the UV light illumination (365 nm), the degradation rate of Ch-I, GII, and Ca-I, was 2982, 8722, and 7467 M _w/week, respectively. Hence, the degradation rate of GII and Ca-I was increased 55 and 97% by UV light (P < 0.008), respectively. This trend was not observed in Ch-I because its starting M _w (78,000 g/mol) was close to the tensile strength lost range (50,000 to 75,000 g/mol) of PLA films. To our knowledge, this is the first study to demonstrate that UV light does further enhance the degradation of PLA films.     

Influence of Hygrothermal Ageing on the Physico-Mechanical Properties of Alkali Treated Industrial Hemp Fibre Reinforced Polylactic Acid Composites

30 wt% aligned untreated long hemp fibre/polylactic acid (AUL) and aligned alkali treated long hemp fibre/polylactic acid (AAL) composites were produced by film stacking and subjected to hygrothermal ageing environment along with neat polylactic acid (PLA). Hygrothermal ageing was carried out by immersing samples in distilled water at 25 and 50 °C over a period of 3 months. It was found that both neat PLA and composites followed Fickian diffusion. Higher temperature generally increased the Diffusion coefficient, D of neat PLA and composites, as well as shortening the saturation time. Neat PLA had the lowest D value followed by AAL composites and then AUL composites. After hygrothermal ageing, tensile and flexural strength, Young’s and flexural modulus and K _Ic were found to decrease and impact strength was found to increase for both AUL and AAL composites. AUL composites had greater overall reduction in mechanical properties than that for AAL composites after hygrothermal ageing. Crystallinity contents of the hygrothermal aged composites support the results of the deterioration of mechanical properties upon exposure to hygrothermal ageing environment.     

Effects of Temperature and Relative Humidity on Polylactic Acid Plastic Degradation

Three high molecular weight (120,000 to 200,000 g mol^–1) polylactic acid (PLA) plastic films from Chronopol (Ch-I) and Cargill Dow Polymers (GII and Ca-I) were analyzed for their degradation under various temperature and relative humidity (RH) conditions. Two sets of plastic films, each containing 11 samples, were randomly hung in a temperature/humidity-controlled chamber by means of plastic-coated paper clips. The tested conditions were 28, 40, and 55°C at 50 and 100% RH, respectively, and 55°C at 10% RH. The three tested PLA films started to lose their tensile properties when their weight-average molecular weight (M _w) was in the range of 50,000 to 75,000 g mol^–1. The average degradation rate of Ch-I, GII, and Ca-I was 28,931, 27,361, and 63,025 M _w/week, respectively. Hence, GII had a faster degradation rate than Ch-I and Ca-I under all tested conditions. The degradation rate of PLA plastics was enhanced by the increase in temperature and relative humidity. This trend was observed in all three PLA plastics (Ca-I, GII, and Ch-I). Of the three tested films, Ch-I was the first to lose its mechanical properties, whereas Ca-I demonstrated the slowest loss, with mechanical properties under all tested conditions.     

The Effect of Masterbatch Addition on the Mechanical, Thermal, Optical and Surface Properties of Poly(lactic acid)

There has been considerable interest in the use of the biodegradable polymer poly(lactic acid) (PLA) as a replacement for petroleum derived polymers due to ease of processability and its high mechanical strength. Other material properties have however limited its wider application. These include its brittle properties, low impact strength and yellow tint. In an attempt to overcome these drawbacks, PLA was blended with four commercially available additives, commonly known as masterbatches. The effect of the addition of 1.5 wt% of the four masterbatches on the mechanical, thermal, optical and surface properties of the polymer was evaluated. All four masterbatches had a slight negative effect on the tensile strength of PLA (3–5% reduction). There was a four fold increase in impact resistance however with the addition of one of the masterbatches. Differential scanning calorimetry demonstrated that this increase corresponded to a decrease in the polymer crystallinity. However there was an associated increase in polymer haze with the addition of this masterbatch. The clarity of PLA was improved through the addition of an optical brightener masterbatch, but the impact resistance remained low. The glass transition and melting temperatures of PLA were not affected by the addition of the masterbatches, and no change was observed in surface energy. Some delay in PLA degradation, in a PBS degradation medium at 50 °C, was observed due to blending with these masterbatches.     

Development of composite materials by mechanochemical treatment of post-consumer plastic waste

Improvement of mechanical properties of recycled mixed plastic waste is one of the fundamental goals in any recycling process. However, polymer immiscibility makes the development of any effective reprocessing method difficult. In this work, a polymer milling process with liquid CO2 was applied to polymeric mixed waste, obtaining a powder material which was successfully utilized as a matrix for a new composite material. Developed materials have interesting mechanical properties and material performance can easily be improved. Investigations on selected mixtures of PP and PE clearly showed evidence of chemical compatibilization.     

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.     

Reutilization of thermostable polyester wastes by means of agglomeration with phenolic resins

We report on the possibility of obtaining organic polymeric matrixes allowing the development of new high performance fire-resistant products by recycling downsized thermostable waste materials. Phenolic resins have been used as binders for recycled waste. Furthermore, considering that reinforced plastic triturations have superior properties (chemical, mechanical, water resistance, etc.) to wood agglomerates, significant advantages over conventional materials are anticipated. In summary, we propose a viable solution to some of the known problems caused by the consumption of wood and to the needs of strengthened plastic processing engineering. Using resins as a binder, several fire-resistant prototypes were prepared from polyester waste, and their mechanical properties, thermal stability, and fire-resistant properties were analyzed.     

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

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

Life cycle assessment of integrated recycling schemes for plastic containers and packaging with consideration of resin composition

Many life cycle assessment studies have evaluated and compared the environmental performance of various technologies for recycling plastic containers and packaging in Japan and other countries. However, no studies have evaluated the combination of recycling technologies in consideration of the resin composition in terms of the quantity of each recycled product so as to maximize their environmental potential. In this study, 27 scenarios of recycling schemes for household waste plastic containers and packaging are developed through integrating a conventional recycling scheme with additional recycling schemes. The conventional recycling scheme involves municipal curbside collection and either the material recycling or feedstock recycling of waste plastics. The additional recycling schemes are feedstock recycling in steel works of the residue from conventional material recycling processes, and corporate voluntary collection and independent material recycling of specific types of plastic trays. Life cycle assessment based on the modeling of recycling processes considering the resin composition in terms of the quantity of each recycled product is applied to evaluate and compare these scenarios from the viewpoints of fossil resource consumption and CO₂ emission. The results show that the environmental loads are reduced in all scenarios including the additional recycling schemes compared with the conventional recycling scheme. However, the independent plastic tray recycling scheme exhibits lower additional environmental savings when the residue recycling scheme is integrated with the conventional material recycling scheme. This is because both additional recycling schemes aim to utilize polystyrene and polyethylene terephthalate, which would otherwise be incinerated as residue from material recycling processes. The evaluation of the environmental loads of plastic recycling with consideration of the resin composition in terms of the quantity of each recycled product makes it possible to investigate recycling schemes that integrate different technologies to maximize their environmental potential.     

Water Absorption Kinetics and Hygrothermal Aging of Poly(lactic acid) Containing Halloysite Nanoclay and Maleated Rubber

Poly(lactic acid)/halloysite nanoclay composites (PLA/HNC) containing maleic anhydride grafted styrene-ethylene/butylene-styrene (SEBS-g-MAH) were produced using melt compounding followed by compression molding. The effects of hygrothermal aging on the thermal properties and functional groups changes of the HNC reinforced PLA (with and without SEBS-g-MAH) at three different temperatures (i.e., 30, 40 and 50 °C) were analyzed using differential scanning calorimetry and Fourier transform infrared spectroscopy techniques. The diffusion coefficient (D) of PLA was decreased by the incorporation of HNC and SEBS-g-MAH. The activation energy of water diffusion (E _a ) of PLA/HNC/SEBS-g-MAH nanocomposites was higher than that of pure PLA. The glass transition temperature (T _g ), cold-crystallization temperature (T _cc ) and melting temperature (T _m ) of the PLA sample were shifted to lower temperature and the effect was more pronounced at 50 °C. The carbonyl index values of all PLA samples increased after immersed in 40 and 50 °C, which is due to the formation of higher amount of carboxyl groups during the hydrolysis process.     

Starch, Poly(lactic acid), and Poly(vinyl alcohol) Blends

Research on biodegradable materials has been stimulated due to concern regarding the persistence of plastic wastes. Blending starch with poly(lactic acid) (PLA) is one of the most promising efforts because starch is an abundant and cheap biopolymer and PLA is biodegradable with good mechanical properties. Poly(vinyl alcohol) (PVOH) contains unhydrolytic residual groups of poly(vinyl acetate) and also has good compatibility with starch. It was added to a starch and PLA blend (50:50, w/w) to enhance compatibility and improve mechanical properties. PVOH (M_W 6,000) at 10%, 20%, 30%, 40%, 50% (by weight) based on the total weight of starch and PLA, and 30% PVOH at various molecular weights (M_W 6,000, 25,000, 78,000, and 125,000 dalton) were added to starch/PLA blends. PVOH interacted with starch. At proportions greater than 30%, PVOH form a continuous phase with starch. Tensile strength of the starch/PLA blends increased as PVOH concentration increased up to 40% and decreased as PVOH molecular weight increased. The increasing molecular weight of PVOH slightly affected water absorption, but increasing PVOH concentration to 40% or 50% increased water absorption. Effects of moisture content on the starch/PLA/PVOH blend also were explored. The blend containing gelatinized starch had higher tensile strength. However, gelatinized starch also resulted in increased water absorption.     

Effect of Compatibilizing Agent on the Properties of Highly Crystalline Composites Based on Poly(lactic acid) and Wood Flour and/or Mica

This article contains a concept of the mechanical properties improvement of the highly crystalline poly(lactic acid) (PLA) and filled composites. PLA as a semi-crystalline thermoplastic polymer was plasticized with poly(ethylene glycol) and filled with 30 vol% of organic and/or inorganic filler. The degree of crytallinity was intentionally increased by annealing. The filler/polymer matrix interphase was modified with the addition of 4, 4′-Methylenediphenyl diisocyanate (MDI). The effect of compatibilizing as well as plasticizing agent on the thermal and mechanical properties, the water-absorption behaviour and crystallization characteristics were studied. The results indicated that high content of filler and crystallites have a strong influence on the composite′s mechanical properties despite of the plasticizer content, showing a high Young modulus. The MDI seems to react in preference easy with plasticizing agent and then alternatively with filler due to the low functionality of commercial PLA grade.     

Influence of Processing Additives on the Degradation of Melt-Pressed Films of Poly(ε-Caprolactone) and Poly(Lactic Acid)

Melt-pressed films of polycaprolactone (PCL) and poly(lactic acid) (PLA) with processing additives, CaCO₃, SiO₂, and erucamide, were subjected to pure fungal cultures Aspergillus fumigatus and Penicillium simplicissimum and to composting. The PCL films showed a rapid weight loss with a minor reduction in the molecular weight after 45 days in A. fumigatus. The addition of SiO₂ to PCL increased the rate of (bio)erosion in A. fumigatus and in compost. The use of a slip additive, erucamide, was shown to modify the properties of the film surface without decreasing the rate of bio(erosion). Both the rate of weight loss and the rate of molecular weight reduction of PCL increased with decreasing film thickness. The addition of CaCO₃ to PLA significantly reduced the thermal degradation during processing, but it also reduced the rate of the subsequent (bio)degradation in the pure fungal cultures. PLA without additives and PLA containing SiO₂ exhibited the fastest (bio)degradation, followed by PLA with CaCO₃. The degradation of the PLA films was initially governed by chemical hydrolysis, followed by an acceleration of the weight change and of the molecular weight reduction. PLA film subjected to composting exhibits a rapid decrease in molecular weight, which then remains unchanged during the measurement period, probably because of crystallization.     

Influence of RFID tags on recyclability of plastic packaging

The use of Radio Frequency IDentification Technology (RFID) in the packaging sector is an important logistical improvement regarding the advantages offered by this technology in comparison with barcodes. Nevertheless, the presence of these devices in plastic packaging, and consequently in plastic waste, can cause several problems in the recycling plants due to the materials included in these devices.In this study, the mentioned recycling constraints have been experimentally identified in a pilot scale recycling study consisting in three recycling tests with an increasing presence of RFID tags. Differences in each test were evaluated. Furthermore, the quality of the recycled material of each test was studied through the injection and testing of tests probes.The results of the pilot scale recycling tests did not show a decrease in the quality of the recycled plastic due to the presence of RFID tags. Nevertheless, several operational problems during the recycling process were observed such as the obstruction of the screens, which lessened the process yield and created process interruptions, as well as the loss of extruded plastic during the process.These recycling constraints cannot be directly extrapolated to the industrial plants due to the different working scales. Nevertheless, technological solutions are proposed in order to avoid these recycling constraints if they appear.