Enzyme-Retted Flax Fiber and Recycled Polyethylene Composites

Municipal solid wastes generated each year contain potentially useful and recyclable materials for composites. Simultaneously, interest is high for the use of natural fibers, such as flax (Linum usitatissimum L.), in composites thus providing cost and environmental benefits. To investigate the utility of these materials, composites containing flax fibers with recycled high density polyethylene (HDPE) were created and compared with similar products made with wood pulp, glass, and carbon fibers. Flax was either enzyme- or dew-retted to observe composite property differences between diverse levels of enzyme formulations and retting techniques. Coupling agents would strengthen binding between fibers and HDPE but in this study fibers were not modified in anyway to observe mechanical property differences between natural fiber composites. Composites with flax fibers from various retting methods, i.e., dew- vs. enzyme-retting, behaved differently; dew-retted fiber composites resulted in both lower strength and percent elongation. The lowest level of enzyme-retting and the most economical process produces composites that do not appear to differ from the highest level of enzyme-retting. Flax fibers improved the modulus of elasticity over wood pulp and HDPE alone and were less dense than glass or carbon fiber composites. Likely, differences in surface properties of the various flax fibers, while poorly defined and requiring further research, caused various interactions with the resin that influenced composite properties.     

Characterization of Sorghum Bran/Recycled Low Density Polyethylene for the Manufacturing of Polymer Composites

The objective of the study was to investigate the suitability of using sorghum bran in recycled low density polyethylene (R-LDPE) composites manufacturing. In response to the disposal of environmental problematic agricultural and polymer waste, composite sheets using recycled low density polyethylene and sorghum bran of different loadings (5, 10, 15 and 20 wt%) were prepared by melt compounding and compression molding. The effects of sorghum bran loadings on the mechanical, thermal, water absorption, swelling and crystalline properties of the composites were determined. Characterization of composites was carried out using X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermo gravimetric (TGA/DTG) and mechanical analyses. It was found that increasing fiber loadings resulted to increased moduli and tensile strength while hardness was decreased. XRD indicated that fiber addition to R-LDPE did not change characteristic peak position. DSC results showed that the R-LDPE had significantly larger peak heat flow during cooling run than the blank R-LDPE, showing higher crystallization rates for R-LDPE. The results obtained confirmed that sorghum bran particles showed some potential as a good reinforcement in polymer matrix composites and indicate its thermal stability for possibly future composite applications.     

Analysis of Flax and Cotton Fiber Fabric Blends and Recycled Polyethylene Composites

Manufacturing composites with polymers and natural fibers has traditionally been performed using chopped fibers or a non-woven mat for reinforcement. Fibers from flax (Linum usitatissimum L.) are stiff and strong and can be processed into a yarn and then manufactured into a fabric for composite formation. Fabric directly impacts the composite because it contains various fiber types via fiber or yarn blending, fiber length is often longer due to requirements in yarn formation, and it controls the fiber alignment via weaving. Composites created with cotton and flax-containing commercial fabrics and recycled high-density polyethylene (HDPE) were evaluated for physical and mechanical properties. Flax fiber/recycled HDPE composites were easily prepared through compression molding using a textile preform. This method takes advantage of maintaining cotton and flax fiber lengths that are formed into a yarn (a continuous package of short fibers) and oriented in a bidirectional woven fabric. Fabrics were treated with maleic anhydride, silane, enzyme, or adding maleic anhydride grafted polyethylene (MAA-PE; MDEX 102-1, Exxelor^® VA 1840) to promote interactions between polymer and fibers. Straight and strong flax fibers present problems because they are not bound as tightly within yarns producing weaker and less elastic yarns that contain larger diameter variations. As the blend percentage and mass of flax fibers increases the fabric strength, and elongation generally decrease in value. Compared to recycled HDPE, mechanical properties of composite materials (containing biodegradable and renewable resources) demonstrated significant increases in tensile strength (1.4–3.2 times stronger) and modulus of elasticity (1.4–2.3 times larger). Additional research is needed to improve composite binding characteristics by allowing the stronger flax fibers in fabric to carry the composites load.     

In Situ Compatibilization of Isotactic Polypropylene and High-Density Polyethylene by a Melt Cobranching Reaction

Incompatible polypropylene (PP) and polyethylene (PE) are difficult to separate in mixed recycling streams such as waste plastic packaging, which makes polyolefin mixtures unsuitable for high-quality products. In this work, based on the free radical branching reaction, a co-branching reaction of isotactic polypropylene (iPP) and high-density polyethylene (HDPE) blends was carried out in the presence of the peroxide, free radical regulator and multifunctional acrylate monomer, and a star-like long-chain branching (LCB) copolymer was obtained. The effect of in situ compatibilization on the structures and mechanical properties of iPP/HDPE was investigated, and the compatibilization mechanism was discussed. Results showed that the mechanical properties of the modified blends were largely improved, and efficient in-situ compatibilization of iPP and HDPE could be taken place in a wide process window. Moreover, the sizes of the dispersed phase in the modified blends were clearly decreased, and the interfacial thickness increased. Compared with the pure iPP/HDPE blend, the initial crystallization temperature of iPP in the modified iPP/HDPE blend was increased, and long branched chains of the LCB copolymers were physically entangled with the chemical identical homopolymers or even participated in the crystallization of iPP and HDPE. Thanks to the in situ compatibilization strategy, the compatibility of iPP/HDPE was significantly improved.

     

The Impact of Biodegradable Plastics in the Properties of Recycled Polyethylene Terephthalate

Journal of Polymers and the Environment - Since biodegradable materials are unwittingly mixed with synthetic materials, this work aimed to study the feasibility of reliably identifying some...     

Outdoor Weathering Evaluation of Carbon-Black-Filled, Biodegradable Copolyester as Substitute for Traditionally Used, Carbon-Black-Filled, Nonbiodegradable, High-Density Polyethylene Mulch Films

Carbon-black-filled, biodegradable, copolyester mulch film (Eastar®, or EA, Tennessee Eastman, Kingsport, TN) and commercial carbon-black-filled, high-density polyethylene (HDPE) mulch film were exposed for 12 weeks to commercial vegetable crop growing conditions by being placed directly on irrigated soil in the field of the University of Tennessee Alcoa Highway State Agriculture Experiment Station (Knoxville, TN) and by being placed on a plywood exposure rack as described by the American Society of Testing and Materials (ASTM) Standard Test Method 1435: Outdoor Weathering of Plastics. Mechanical properties and weather information were collected in order to evaluate the feasibility of using the newly developed biodegradable EA mulch film to replace the nonbiodegradable HDPE mulch film. Results indicate that the EA mulch film exhibited favorable tensile strength and elongation-at-break during outdoor exposure rack testing and outdoor, in-field, placed directly on the soil, exposure testing, suggesting biodegradable EA could be a substitute for the HDPE nonbiodegradable material.     

Processing and Characterization of Recycled Polypropylene and Acrylonitrile Butadiene Rubber Blends

In this paper investigation on thermoplastic elastomers (TPE) and thermoplastic vulcanizates (TPV) derived from waste polypropylene (WPP) of Municipal Solid Waste (MSW) and acrylonitrile-butadiene rubber (NBR) are reported. The WPP was segregated, cleaned, dried and melt processed with NBR at 180 °C in a Brabender Plasticorder at different blend ratios. TPV was prepared by dynamic vulcanization of the TPE with conventional sulfur accelerator curing system. The mechanical properties measured were found to decrease with increase in NBR proportion in the blend; however the dynamic vulcanization of the nitrile rubber phase enhanced the strength properties of the corresponding TPE. The crystallinity of the WPP reduced with increase in NBR ratio. The dynamic modulus decreased with nitrile rubber content in the TPE. Interestingly, the storage modulus of the TPV at higher rubber content enhanced significantly and damping characteristics increased sharply. The rheology studies reveal that the damping of the blend has been reduced with the addition of high storage modulus rubber at melt processing conditions and hence increased viscosity. The amorphous rubber content with higher storage modulus imparts higher viscosity for the polypropylene (PP) matrix at the processing temperature. The SEM study reveals that the dynamic vulcanization of the rubber phase in the blend caused a smoother and finer surface morphology.     

Properties of Composite Panels Made from Tetra-Pak and Polyethylene Waste Material

The objective of this study was to evaluate some of the properties of experimental composite panels manufactured from waste packaging materials without using any additional binders. Particles from three types of materials, namely Tetra-Pak, food packaging films (FPEF) as recycled stretch wraps, and candy polyethylene wrappers (CPEW) were used at different ratios in the panels at a target density of 900 kg/m³. Modulus of rupture (MOR), screw holding strength and dimensional stability in the form of thickness swelling and water absorption of the panels were determined according to European (EN) standards. Based on the findings in this work it was determined that the ratio of different raw materials significantly influenced overall properties of the samples. The highest MOR value of 15.5 MPa was determined for the samples having 40 % Tetra-Pak and 60 % CPEW particles. Modulus of rupture values of the panels decreased with decreasing content of CPEW in the samples. The increased content of Tetra-Pak particles in the samples also resulted in reduction of their strength characteristics and dimensional stability. Properties of the samples considered in this work satisfied minimum requirements of typical particleboard stated in EN standards. It appears that such waste material would have potential to be used as raw material for value-added composite production using no adhesive in the panels and, therefore, such panels would possibly create significant ecological impact as green product.     

Recycled Polyethylene Composites Reinforced with Jute Fabric from Sackcloth: Part I-Preparation and Preliminary Assessment

In recent times, environmental safety has been on priority in the development of new materials leading to a recycling and reuse approach to conserve the materials resources. This has resulted in more focus on the application of natural materials such as lignocellulosic fibers. This paper presents the characterization of continuous and aligned jute fabrics obtained from new and used sacks as well as the preparation and characterization of their composites incorporated into recycled polyethylene or as isolated pieces up to 40 wt%. These environmentally friendly composites were subjected to bend test and the fracture surface analyzed by SEM. The fabric from new sacks showed greater damage tolerance than that from the used sacks. The flexural stress increased steadily with increasing used fabric content up to 30 wt%, which is explained using fractographic studies on ruptured specimens. Used jute fabric composites are found to be viable alternative materials for low strength conventional materials based on cost–performance comparison with conventional materials.     

Effect of Recycling on Material Properties of Glass-filled Polyethylene Terephthalate

Recycled plastics are considered low performance materials because their properties are expected to decrease drastically with recycling. The objective of this study was to characterize a 15 wt.% glass filled polyethylene terephthalate (rPET-15GF) using six recycle generations and four recycle ratios. Mechanical properties such as tensile strength, elastic modulus, and percent elongation to failure of the PET composite were determined for various recycle generations and recycle ratios. Results show that the mechanical properties of rPET-15GF decrease slightly per recycle generation. In contrast, thermal properties of rPET-15GF were not at all affected by the recycling process. This data demonstrates that recycled glass filled PET can be used effectively to fabricate components without significantly affecting their mechanical performance.     

Preparation and Characterization of Compatible and Degradable Thermoplastic Starch/Polyethylene Film

The degradability of the compatible thermoplastic starch/polyethylene film was investigated by weight loss percent (WLP), Fourier Transform Infrared (FT-IR) Spectroscopy, and Scanning Electron Microscope (SEM). The compatible film was prepared by using the particles of thermoplastic starch/polyethylene blends that were produced by one-step reactive extrusion. The weight of the film after degradation reduced more than 3% for 30 days and 4% for 60 days. The FTIR results revealed that both starch and polyethylene in the film exhibited varying degrees of degradation. SEM photographs of the films after degradation showed that starch particles in the film disintegrated into smaller particles or separated out of the film surface. Degradation studies demonstrated that the compatible thermoplastic starch/polyethylene film had increased degradability at the given degradable environment. The information implies that this film could be utilized as a degradable plastic.     

Potential Use of Recycled PET in Comparison with Liquid Crystalline Polyester as a Dual Functional Additive for Enhancing Heat Stability and Reinforcement for High Density Polyethylene Composite Fibers

The recycle poly(ethylene terephthalate) (rPET) used as an alternative reinforcing material for in situ microfibrillar-reinforced composite, compared with liquid crystalline polymer (LCP), was investigated. The PE-LCP and PE-rPET composites were prepared as fiber using hot drawing process. The effects of draw ratios and compatibilizer (styrene-ethylene butylene-styrene-grafted maleic anhydride, SEBS-g-MA) loading on morphology, tensile properties, thermal stability and dynamic mechanical characteristics of the LCP- and rPET-composite systems were studied. In as-spun samples containing compatibilizer, the fibrillation of LCP domains was observed whereas rPET domains appeared as droplets. After drawing, good fibrillation of LCP and rPET domains is remarkably observed especially in the composite fibers with compatibilizer loading. The mechanical properties of the composite fibers were strongly depended on the fibrillation of the dispersed phases which directly related the levels of draw ratio and compatibilizer loading. The mechanical properties enhanced by SEBS-g-MA were more pronounced in the rPET than LCP systems. The presence of rPET in the composite fibers alone or with the compatibilizer clearly improved the thermal resistance of PE whereas no significant change in thermal stability for the LCP-containing composite fibers with and without compatibilizer loading. The results from dynamic mechanical analysis revealed that an improvement in dynamic mechanical properties of the composite fibers could be achieved by drawing with optimum draw ratio together with optimum compatibilizer dosage. All obtained results suggested the high potential of rPET minor blend-component as a good reinforcing and thermal resistant materials for the thermoplastic composite fiber, in replacing the more expensive LCP.     

Synthesis and Characterization of Low Volatile Content Polyurethane Dispersion from Depolymerised Polyethylene Terphthalate

In the past few decades, governments and international agencies have been placing more emphasis on the improvement of production technique, working conditions and reduction of the toxic emission to the atmosphere. In this context aqueous polyurethane dispersion was synthesized from depolymerised polyethylene terphthalate (PET) waste. 1,4-Butanediol was used in PET depolymerisation. Polyurethane dispersion films were characterized using differential scanning calorimeter, Fourier transform infrared spectroscopy, gel permeable chromatography, etc. Incorporation of PET waste in polyurethane dispersion was an added advantage in waste management and produced better quality polyurethane dispersion.     

Effects of Saturated Acids on Physical Properties of UPE Resins Prepared from Recycled PET Products

In this study, effects of saturated acids on physical properties, including hardness, impact strength, flexural properties and thermal properties, of unsaturated polyester or UPE resins prepared from recycled PET bottles and fabrics were investigated. PET was depolymerized by glycolysis reaction with the excess propylene glycol in the presence of zinc acetate as a catalyst. UPE resins were then synthesized by polyesterification of these glycolyzed products with maleic anhydride as an unsaturated diacid as well as succinic acid and adipic acid as a saturated diacid. With the addition of styrene monomer, UPEs were subsequently casted into specimens by crosslinking reaction using methyl ethyl ketone peroxide and cobalt octoate as an initiator and a catalyst, respectively. Physical properties of the cured specimens were then studied. The results showed that, when a saturated acid was incorporated, the hardness of the cured UPE resins decreased due to the decreasing amount of crosslinks. The extended distance between crosslinking sites on molecular chains facilitated load distribution, resulting in the significant improvement of impact strength. The flexural strength was also improved when the small amount of saturated acid was used. The onset thermal degradation temperatures and the glass transition temperatures of the prepared UPE resins were almost unchanged.     

Effects of Natural and Artificial Weathering on the Physical Properties of Recycled Poly(ethylene terephthalate)

In accelerated weathering tests, specimens are exposed to higher radiation intensity, temperature and humidity than is likely under natural weathering in order to achieve rapid degradation of the polymer in a convenient short time. In the current work, a correlation between the two environments is attempted so that a prediction of lifetimes in the natural environment can be achieved. During aging, surface flaws are created due to the chain scission process. This is initiated by the absorption of ultra-violet light and directly affects visual appearance and impact strength. After natural weathering, the material shows only plastic deformation in an impact test. However, after artificial weathering to 5000 h of UV exposure, there is a decrease of 85% in impact strength. Colour change occurs at a high rate in the early stages of UV exposure. Beyond 2000 h of exposure, the colour change approaches a steady state and a correlation between the changes under natural and artificial weathering becomes apparent for a potential prediction of lifetimes. From the analysis including the specular component (SCI), taking surface roughening into account, 1 year under natural weathering was found to be equivalent to 25 days under accelerated weathering.     

Influence of Filler Particle Size on Physical Properties and Biodegradation of Biocomposites Based on Low-Density Polyethylene and Lignocellulosic Fillers

This study examined biocomposites based on low-density polyethylene (LDPE) and lignocellulosic fillers [wood flour (WF) and oil flax straw (FS)] selecting four size fractions of each lignocellulosic material as fillers for the composites. The primary aim was to evaluate the influence of fraction size on the composites’ basic properties; to accomplish this, the composites’ mechanical properties, thermal oxidation, thermophysical characteristics, and water absorption capacity were examined. Then microphotographs of the samples were created and length-to-diameter (L/D) ratio of the fillers was calculated, finding that the L/D ratio increased with increasing particle size. The particle size influenced the oxidative degradation and water absorption processes in composites with oil flax but not in those with WF. Biodegradation tests performed on the recovered soil found that the loss of mass in composites based on LDPE and FS was higher than in the same composites with WF. Moreover, at the initial stage of composting, the biodegradation rate correlated with the size of filler particles (i.e., the larger the particles, the higher the degradation rate of the biocomposite).     

锰锌铁氧体/SiO_2复合磁性材料的制备和表征

以正硅酸乙酯(TEOS)作为包覆材料,对锰锌铁氧体纳米颗粒进行SiO2包覆,制备出锰锌铁氧体/SiO_2复合磁性材料。利用FTIR,XRD,SEM等技术对其进行了表征,并研究了其对模拟亚甲基蓝废水的吸附脱色效果。实验结果表明:当SiO_2质量分数为40%1时,采用先将锰锌铁氧体在柠檬酸溶液中搅拌分散3 h后,加人氨水调节溶液pH,再继续搅拌分散3 h的分段分散方法制备的复合磁性材料对亚甲基蓝废水的处理效果更好,处理亚甲基蓝质量浓度为50 mg/L、COD为160 mg/L的废水,废水脱色率为97.2%,COD去除率为19.3%。表征结果显示:复合磁性材料锰锌铁氧体/SiO_2为球形颗粒,平均粒径为100 nm;SiO_2包覆前后锰锌铁氧体的晶型均为尖晶石型结构,在复合磁性材料中SiO_2以无定型的形态存在。     

Mechanical and Physical Properties of Green Biocomposite Based on Medium Density Fiberboard Sanding Powder/Polyethylene/Nanoclay

Medium density fiberboard (MDF) sanding powder is an industrial waste that has not been yet used as a raw material to produce composites. In this study, the influence of nanoclay particles on the flexural and impact strengths and the withdrawal strength of green biocomposites (based on MDF sanding powder/polyethylene/nanoclay) were investigated. For this aim, medium density fiberboard sanding dust and polyethylene were used as the lignocellulosic and thermoplastic material, respectively. In addition, maleic anhydride grafted polyethylene was used in three weight percentages (0, 3 and 6 %) as a coupling agent and compatibilizer, and Cloisite^®15A was used in four weight percentages (0, 2, 4 and 6 %). To prepare samples, wood-plastic granules were produced by using a twin-screw extruder followed by the hot pressing method. The mechanical and physical properties were measured according to the CEN/TS15534:2007 and ASTM-D256 technical specifications. The results showed that the coupling agent improved the mechanical and physical properties of biocomposites; however, its effect might be affected by the nanoclay particles. Furthermore, the ultrastructure of the biocomposites was surveyed with SEM.     

Hybridized Biocomposites from Agro-Wastes: Mechanical,Physical and Thermal Characterization

Agricultural wastes, oil palm trunk (OPT) veneer and oil palm empty fruit bunch (EFB) mat were used for the preparation of hybridized plywood using 250 and 450 g/m² of urea formaldehyde (UF) as gluing agent. The mechanical (flexural strength, flexural modulus, screw withdrawal, shear strength), physical (density, water absorption, thickness swelling and delamination) and thermal (TGA) properties of the biocomposites were studied. Images taken with a scanning electron micrograph (SEM) indicated an improvement in the fiber–matrix bonding for the laminated panel glued with 450 g/m² of UF.     

Physical Morphology and Quantitative Characterization of Chemical Changes of Weathered PVC/Pine Composites

This study investigated weathering effects on polyvinyl chloride (PVC) based wood plastic composites (WPC), with a focus on the color and structure that is attributed to the material composition. It is directed towards quantifying the main chemical modifications, such as carbonyl and vinyl groups which are formed during weathering. These composites were subjected to three weathering regimes: exterior, accelerated xenon-arc, and accelerated UVA. The change in color was monitored using colorimetry. Fourier transform infrared spectroscopy was used to identify and quantify the chemical modifications (carbonyl formation and vinyl propagation) due to weathering. Additionally, scanning electron microscopy was employed to observe the physical morphological changes that occurred. The results showed that exterior and accelerated xenon-arc and UVA weathering regimes increased the degree of lightness, total color change, carbonyl concentration, and wood loss on the surfaces of the weathered composites. The increased carbonyl concentration during weathering implied that degradation had occurred by oxidation process. Also, oxidation and lignin (from the wood) degradation influenced the color (lightness) of PVC based WPC upon weathering.