Hybrid Composites from Waste Materials

Hybrid composites of thermoplastic biofiber reinforced with waste newspaper fiber (NF) and poplar wood flour (WF) were prepared. The weight ratio of the lignocellulosic materials to polymer was 30:70 (w:w). Polypropylene (PP) and maleic anhydride grafted polypropylene (MAPP) were also used as the polymer matrix and coupling agent, respectively. The mechanical properties, morphology and thermal properties were investigated. The obtained results showed that tensile and flexural modulus of the composites were significantly enhanced with addition of biofibers in both types (fiber and flour), as compared with pure PP. However, the increasing in WF content substantially reduced the tensile, flexural and impact modulus, but improved the thermal stability. This effect is explained by variations in fiber morphological properties and thermal degradation. Increasing fiber aspect ratio improved mechanical properties. The effect of fiber size on impact was minimal compared to the effects of fiber content. Scanning electron microscopy has shown that the composite, with coupling agent, promotes better fiber–matrix interaction. The largest improvement on the thermal stability of hybrid composites was achieved when WF was added more. In all cases, the degradation temperatures shifted to higher values after addition of MAPP. This work clearly showed that biofiber materials in both forms of fiber and flour could be effectively used as reinforcing elements in thermoplastic PP matrix.     

Mechanical Properties of Kenaf/Polypropylene Nonwoven Composites

With an industrial trend of going green, the use of natural fibers in polymer composites is growing rapidly, especially in the automotive industry. The objectives of this research are to investigate mechanical performance of kenaf/polypropylene nonwoven composites (KPNCs) in production of automotive interior parts, and to develop preliminary linear models for quantifying elastic range of the KPNCs under various loading conditions. Using polypropylene (PP) fiber as bonding fiber, the KPNCs were fabricated with 50/50 blend ratio by weight. Unlike the manufacturing method of fiber reinforced plastics, all KPNCs were produced by carding and needle-punching techniques and thermally bonded by a panel press with 3-mm thickness gauge. Mechanical properties of the KPNCs in terms of uniaxial tensile, open-hole tensile, tensile at different strain rates, flexural, and in-plane shear were measured instrumentally. It was found that sample which was processed at higher temperature (230?°C) but shorter time (60?s) had the best mechanical performance. KPNCs were relatively insensitive to the notch but sensitive to strain rates. The linear elastic finite element model of KPNCs agreed well with the experimental results in the valid strain range of 0?C0.5?% for uniaxial tensile test and 0?C1?% for flexural test.     

Biopolymers Based Green Composites: Mechanical, Thermal and Physico-chemical Characterization

Natural cellulosic fibers are one of the smartest materials for use as reinforcement in polymers possessing a number of applications. Keeping in mind the immense advantages of the natural fibers, in present work synthesis of natural cellulosic fibers reinforced polymer composites through compression molding technique have been reported. Scanning Electron microscopy (SEM), Thermo gravimetric/Differential thermal/Derivative Thermogravimetry (TGA/DTA/DTG), absorption in different solvents, moisture absorbance, water uptake and chemical resistance measurements were used as characterization techniques for evaluating the different behaviour of cellulosic natural fibers reinforced polymer composites. Effect of fiber loading on mechanical properties like tensile strength, flexural strength, compressive strength and wear resistances has also been determined. Reinforcing of the polymer matrix with natural fibers was done in the form of short fiber. Present work indicates that green composites can be successfully fabricated with useful mechanical properties. These composites may be used in secondary structural applications in automotive, housing etc.     

Development of a catalytic dehalogenation (Cl,Br) process for municipal waste plastic-derived oil

Dehalogenation is a key technology in the feedstock recycling of mixed halogenated waste plastics. In this study, two different methods were used to clarify the effectiveness of our proposed catalytic dehalogenation process using various carbon composites of iron oxides and calcium carbonate as the catalyst/sorbent. The first approach (a two-step process) was to develop a process for the thermal degradation of mixed halogenated waste plastics, and also develop dehalogenation catalysts for the catalytic dehydrochlorination of organic chlorine compounds from mixed plastic-derived oil containing polyvinyl chloride (PVC) using a fixed-bed flow-type reactor. The second approach (a single-step process) was the simultaneous degradation and dehalogenation of chlorinated (PVC) and brominated (plastic containing brominated flame retardant, HIPS–Br) mixed plastics into halogen-free liquid products. We report on a catalytic dehalogenation process for the chlorinated and brominated organic compounds formed by the pyrolysis of PVC and brominated flame retardant (HIPS–Br) mixed waste plastics [(polyethylene (PE), polypropylene (PP), and polystyrene (PS)], and also other plastics. During dehydrohalogenation, the iron- and calcium-based catalysts were transformed into their corresponding halides, which are also very active in the dehydrohalogenation of organic halogenated compounds. The halogen-free plastic-derived oil (PDO) can be used as a fuel oil or feedstock in refineries.     

Lignocellulosic Fiber-Reinforced Keratin Polymer Composites

Short fiber reinforced polymer composites were prepared from lignocellulose fibers and feather keratin polymer (FKP). The FKP matrix was prepared from the reactive processing of poultry feather keratin, glycerol, water, and sodium sulfite. Lignocellulose fibers of varying source, length, and mass fraction were used and it was found that positive reinforcement of FKP was affected by all three. Positive reinforcement was defined as an increase in elastic modulus when normalized by FKP with the same amount of glycerol but no fibers. Positive reinforcement was only able to occur for modulus but not stress at break indicating that the composites were of high physical properties only under small deformations. At large deformations, fiber pull-out was observed in the composites using scanning electron microscopy. The most likely origin of this behavior appeared to be from weak fiber–polymer interactions dominated by friction and rationalized by a force balance across the fiber–polymer interface. High fiber loadings were shown to be reinforcing because of the formation of a network of lignocellulose fibers. The addition of lignocellulose fibers increased the thermal stability of the material.     

Lightweight Polypropylene Composites Reinforced by Long Switchgrass Stems

Switchgrass (SG) stems with lengths up to 10 cm have been used as reinforcement to make lightweight composites with polypropylene (PP) webs. The long SG stems, with simple cut or split and without chemical treatment, were used directly in the composites. Utilizing SG stems for composites not only increases the values of SG but also provides a green, sustainable and biodegradable material for the composites industry. Lightweight composites are preferred, especially for automotive applications due to the potential saving in energy. In this research, the effects of manufacturing parameters on the properties of composites have been studied. Although the tensile properties of SG stem are significantly worse than jute fiber, SG stem with low bulk density is found to better reinforce the lightweight composites. Compared with the jute-PP composites of the same density (0.47 g/cm³), composites reinforced by the split SG stems have 56% higher flexural strength, 19% higher modulus of elasticity, 15% higher impact resistance, 63% higher Young’s modulus, 52% lower tensile strength, and similar sound absorption property. The SG-PP composites with optimized properties have the potential to be used for industrial applications such as the support layers in automotive interiors, office panels and ceiling tiles.     

PLA Based Biopolymer Reinforced with Natural Fibre: A Review

In recent years renewed interest on the development of biopolymers, based on constituents obtained from natural resources is gaining much attention. Natural fibres such as kenaf, hemp, flax, jute, bamboo, elephant grass and sisal based polymer with thermoplastic and thermoset matrices offer reductions in weight, cost and carbon dioxide emission, less reliance on foreign oil resources and recyclability. Reinforced biopolymer with natural fibres is the future of “green composites” addressing many sustainability issues. Among the available biopolymer, PLA (polylactide) is the only natural resource polymer produced at a large scale of over 140,000 tonnes per year. Natural fibre reinforced PLA based biocomposites are widely investigated by the polymer scientists in the last decade to compete with non renewable petroleum based products. The type of fibre used plays an important role in fibre/matrix adhesion and thereby affects the mechanical performance of the biocomposites. The aim of this review is to investigate the effects of processing methods, fibre length, fibre orientation, fibre-volume fraction, and fibre-surface treatment on the fibre/matrix adhesion and mechanical properties of natural-fibre-reinforced PLA composites. Although much work has been performed to engineer the design of such superior biocomposites, the information is scattered in nature. A comprehensive review on the major technical considerations undertaken to prepare such biocomposites over the last decade is investigated to address the feasibility of wide scale industrial acceptance to such biocomposites. A brief review on the available natural fibres and biopolymer is also given for a comparative study.     

Cotton Fibre-reinforced Thermosets Versus Ramie Composites: A Comparative Study using Petrochemical- and Agro-based Resins

Natural fibres offer an interesting alternative to petrochemical products. Reclaimed cotton is mainly used as a low cost fibre to “fill” composites used as interior parts in the automotive industry. Mechanical requirements of such composites are low and the potential of the cotton-fibre to reinforce plastics is not used adequately. This paper gives background information and discusses the use of the cotton fibres in composites compared to ramie fibres. In this study the fibre strength was tested with a Dia-Stron device, fineness was tested with Fibreshape. A roller card is well suited to process fibres to a multi layer web. Cotton and ramie fibres were embedded in epoxy resin and a bio-based resin PTP^®. The composites were tested for impact and tensile properties. The results show that mechanical properties of the composites are strongly influenced by fibre properties. The data and results demonstrate the important role force-elongation characteristics of fibre play in optimising the properties of natural fibre composites. Cotton with its morphological and mechanical properties can play a more crucial role to optimise products with a view to improve the impact properties.     

Storage stability of injection-molded starch-zein plastics under dry and humid conditions

Corn starch and zein mixtures (4 : 1 dry weight) were extruded and injection-molded in the presence of plasticizers (glycerol and water). Tensile strength and percentage elongation of the molded plastics were measured before and after 1 week of storage under a dry or humid condition (11 or 93% RH). With 10–12% glycerol and 6–8% water, injection-molded plastics had relatively good tensile properties (20- to 25-MPa tensile strength and 3.5–4.7% elongation). But while exposed to dry conditions (11% RH), the molded plastics lost weight (0.5–1.5% in 7 days) and became very brittle, with significant decreases in tensile strength and elongation. Partial replacement (5–10%) of starch with a maltodextrin (average DE 5) reduced the glass transition and melting temperatures of the starch-zein mixture as well as the dry storage stability. Using potato starch instead of corn starch significantly improved the dry storage stability of the injection-molded starch-zein plastics (18- vs 11-MPa tensile strength). Anionic corn starches with a maleate or succinate group (DS<0.01) produced injection-molded plastics with improved tensile properties and storage stability. Plastics prepared from the starch maleate and zein mixture retained the strength during 1 week of dry storage without a significant change (26-MPa tensile strength and 3.7% elongation after 1 week of storage).Paper presented at the Bio/Environmentally Degradable Polymer Society—Second National Meeting, August 19–21, 1993, Chicago, Illinois.Journal paper No. J-15561 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa, Project No. 2863.     

Study on the conversion of waste plastics/petroleum resid mixtures to transportation fuels

Catalytic coprocessing of model and waste plastics with light Arabian crude oil residue was investigated using NiMo/Al₂O₃, ZSM-5, FCC, and hydrocracking catalysts. Reaction systems that were studied included low density polyethylene (LDPE), high density polyethylene (HDPE), polystyrene (PS), and polypropylene (PP). A series of single (plastic/catalyst) and binary (plastic/resid/catalyst) reactions were carried out in a 25-cm³ micro autoclave reactor under different conditions of weight and type of catalyst, duration, pressure, and temperature. The optimum conditions selected for our work were: 1% catalyst by weight of total feedstock weight, 60min reaction time, 8.3Mpa of H₂, and 430°C. The product distribution for the binary system using plastic and petroleum residue provided some encouraging results. High yields of liquid fuels in the boiling range of 100°–480°C and gases were obtained along with a small amount of heavy oils and insoluble material such as gums and coke. In general, this study helps to demonstrate the technical feasibility of upgrading both waste plastics and petroleum resid, as well as an alternative approach to feedstock recycling.     

Soda-Treated Sisal/Polypropylene Composites

Treated sisal fibers were used as reinforcement of polypropylene (PP) composites, with maleic anhydride-grafted PP (MAPP) as coupling agent. The composites were made by melting processing of PP with the fiber in a heated roller followed by multiple extrusions in a single-screw extruder. Injection molded specimens were produced for the characterization of the material. In order to improve the adhesion between fiber and matrix and to eliminate odorous substances, sisal fibers were treated with boiling water and with NaOH solutions at 3 and 10 wt.%. The mechanical properties of the composites were assessed by tensile, bend and impact tests. Additionally, the morphology of the composites and the adhesion at he fiber–matrix interface were analyzed by SEM. The fiber treatment led to very light and odorless materials, with yields of 95, 74 and 62 wt.% for treatments with hot water, 3 and 10 wt.% soda solution respectively. Fiber treatment caused an appreciable change in fiber characteristics, yet the mechanical properties under tensile and flexural tests were not influenced by that treatment. Only the impact strength increased in the composites with alkali-treated sisal fibers.     

Preparation and Properties of Green Composites Based on Tapioca Starch and Differently Recycled Paper Cellulose Fibers

Green composites obtained from biodegradable renewable resources have gained much attention due to environmental problems resulting from conventionally synthetic plastics and a global increasing demand for alternatives to fossil resources. In this work we used different cellulose fibers from used office paper and newspaper as reinforcement for thermoplastic starch (TPS) in order to improve their poor mechanical, thermal and water resistance properties. These composites were prepared by using tapioca starch plasticized by glycerol (30 % wt/wt of glycerol to starch) as matrix reinforced by the extracted cellulose fibers with the contents ranging from 0 to 8 % (wt/wt of fibers to matrix). Properties of composites were determined by mechanical tensile tests, differential scanning calorimetry, thermogravimetric analysis, water absorption measurements, scanning electron microscopy, and soil burial tests. The results showed that the introduction of either office paper or newspaper cellulose fibers caused the improvement of tensile strength and elastic modulus, thermal stability, and water resistance for composites when compared to the non-reinforced TPS. Scanning electron microscopy showed a good adhesion between matrix and fibers. Moreover, the composites biological degraded completely after 8 weeks but required a longer time compared to the non-reinforced TPS. The results indicated that these green composites could be utilized as commodity plastics being strong, inexpensive, plentiful and recyclable.     

Utilization of Porous Carbons Derived from Coconut Shell and Wood in Natural Rubber

The porous carbons derived from cellulose are renewable and environmentally friendly. Coconut shell and wood derived porous carbons were characterized with elemental analysis, ash content, X-ray diffraction, infrared absorbance, particle size, surface area, and pore volume. The results were compared with carbon black. Uniaxial deformation of natural rubber (NR) composites indicate the composites reinforced with the porous carbon from coconut shell have higher tensile moduli at the same elongation ratio than the composites reinforced with wood carbon. 40 % coconut shell composite showed a fivefold increase in tensile modulus compared to NR. Polymer–filler interactions were studied with frequency dependent shear modulus, swelling experiments and dynamic strain sweep experiments. Both linear and non-linear viscoelastic properties indicate the polymer–filler interactions are similar between coconut shell carbon and wood carbon reinforced composites. The swelling experiments, however, showed that the polymer–filler interaction is greater in the composites reinforced with coconut shell instead of wood carbon.     

Lignin-based Carbon Fibers: Effect of Synthetic Polymer Blending on Fiber Properties

Carbon fibers have been produced from hardwood lignin/synthetic polymer blend fibers. Hardwood kraft lignin was thermally blended with two recyclable polymers, poly(ethylene terephthalate) (PET) and polypropylene (PP). Both systems were easily spun into fibers. A thermostabilization step was utilized prior to carbonization to prevent fusion of individual fibers. For the lignin-based carbon fibers, careful control of heating rate was required. However, PET–lignin blend fibers can be thermostabilized under higher heating rates than the corresponding homofibers. Carbon fiber yield decreased with increasing incorporation of synthetic plastic. However, carbon fiber yield obtained for a 25% plastic blend fiber was still higher than that generally reported for petroleum pitch. Blend composition also affected surface morphology of the carbon fibers. Immiscible lignin–PP fibers resulted in a hollow and/or porous carbon fiber; whereas carbon fiber produced from miscible lignin–PET fibers have a smooth surface. Synthetic polymer blending also affected the mechanical properties of the fibers, especially MOE; lignin-based carbon fiber properties improved upon blending with PET.     

Fungal-modification of Natural Fibers: A Novel Method of Treating Natural Fibers for Composite Reinforcement

Growing interest in green products has provided fresh impetus to the research in the field of renewable materials. Plant fibers are not only renewable but also light in weight and low in cost. Polymer composites manufactured using them find applications in diverse fields such as automobiles, housing, and furniture. However, their hydrophilic nature and inadequate adhesion with matrix limits their use in high performance applications. In this study, a novel method for improving adhesion characteristics of natural fibers has been developed. This method is carried out by treating hemp fibers with a fungus: Ophiostoma ulmi, obtained from elm tree infected with Dutch elm disease. Treated fibers showed improved acid–base characteristics and resistance to moisture. Improved acid–base interactions between fiber and resin are expected to improve the interfacial adhesion, whereas improved moisture resistance would benefit the durability of the composites. Finally, composites were prepared using untreated/treated fibers and unsaturated polyester resin. Composites with treated fibers showed slightly better mechanical properties, which is most probably due to improved interfacial adhesion.     

Bioabsorbable Soy Protein Plastic Composites: Effect of Polyphosphate Fillers on Biodegradability

The use of biodegradable polymers made from renewable agricultural products such as soy protein isolate has been limited by the tendency of these materials to absorb moisture. A straightforward approach for controlling the inherent water absorbency of the biodegradable polymers involves blending special bioabsorbable polyphosphate fillers, biodegradable soy protein isolate, plasticizer, and adhesion promoter in a high-shear mixer followed by compression molding. The procedure yields a relatively water-resistant, biodegradable soy protein polymer composite, as previously reported. The aim of the present study is to determine the biodegradability of the new polyphosphate filler/soy protein plastic composites by monitoring the carbon dioxide released over a period of 120 days. The results suggest that the composites biodegrade satisfactorily, with the fillers having no significant effect on the depolymerization and mineralization of the soy protein plastic, processes that would otherwise result in nonbiodegradable composites. Further, the results indicate that the biodegradation and useful service life of these biocomposites may be controlled by changing the filler concentration, making the biocomposites useful in applications in which the control of water resistance and biodegradation is critical.     

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

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

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.     

Biodegradable Soy-Based Plastics: Opportunities and Challenges

Today's plastics are designed with little consideration for their ultimate disposability or the effect of the resources (feedstocks) used in making them. This has resulted in mounting worldwide concerns over the environmental consequences of such materials when they enter the mainstream after their intended uses. This led to the concept of designing and engineering new biodegradable materials–materials that have the performance characteristics of today's materials but that undergo biodegradation along with other organic waste to soil humic materials. Hence, the production of biodegradable materials from annually renewable agricultural feedstocks has attracted attention in recent years. Agricultural materials such as starches and proteins are biodegradable and environmentally friendly. Soybean is a good candidate for manufacturing a large number of chemicals, including biodegradable plastics, as it is abundantly available and cheap. Soy protein concentrate, isolate, or flakes could be compounded with synthetic biodegradable plastics such as polycaprolactone or poly (lactic acid) to make molded products or edible films or shopping bags and make the environment cleaner and greener.     

Mechanical, Thermal and Water Absorption Properties of Kenaf-Fiber-Based Polypropylene and Poly(Butylene Succinate) Composites

The use of composites made from non-biodegradable conventional plastic materials (e.g., polypropylene, PP) is creating global environmental concern. Biodegradable plastics such as poly(butylene succinate) (PBS) are sought after to reduce plastic waste accumulation. Unfortunately, these types of plastics are very costly; therefore, natural lignocellulosic fibers are incorporated to reduce the cost. Kenaf fibers are also incorporated into PP and PBS for reinforcing purposes and they have low densities, high specific properties and renewable sourcing. However without good compatibilization, the interfacial adhesion between the matrix and the fibers is poor due to differences in polarity between the two materials. Maleic anhydride-grafted compatibilizers may be introduced into the system to improve the matrix-fiber interactions. The overall mechanical, thermal and water absorption properties of PP and PBS composites prepared with 30 vol.% short kenaf fibers (KFs) using a twin-screw extruder were being investigated in this study. The flexural properties for both types of composites were enhanced by the addition of compatibilizer, with improvements of 56 and 16 % in flexural strength for the PP/KF and PBS/KF composites, respectively. Good matrix-fiber adhesion was also observed by scanning electron microscopy. However, the thermal stability of the PBS/KF composites was lower than that of the PP/KF composites. This result was confirmed by both DSC and TGA thermal analysis tests. The water absorption at equilibrium of a PBS composite filled with KFs is inherently lower than of a PP/KF composite because the water molecules more readily penetrate the PP composites through existing voids between the fibers and the matrix. Based on this research, it can be concluded that PBS/KF composites are good candidates for replacing PP/KF composites in applications whereby biodegradability is essential and no extreme thermal and moisture exposures are required.