Natural Weathering of Kenaf Bast Fibre-Filled Poly(Butylene Succinate) Composites: Effect of Fibre Loading and Compatibiliser Addition

Natural weathering was performed on poly(butylene succinate) (PBS) and its kenaf bast fibre (KBF) filled composites by exposing the specimens to a tropical climate for a period of 6 months (max–min temperature: 31.5–23.9 °C; relative humidity: 78.9%). The aim of this study was to investigate the effects of KBF loading and the addition of maleated PBS compatibiliser (PBSgMA) on the performance of the composites under natural weathering. As expected, the flexural properties of both the uncompatibilised and compatibilised composites dropped with increasing exposure time. The weathered specimens were also assessed by colour change analysis, FTIR spectroscopy analysis and SEM examination. The total colour change, ΔE _ab , of both the uncompatibilised and compatibilised composites increased with weathering time. FTIR spectroscopy analysis confirmed the presence of oxidation products such as hydroxyl, carbonyl and vinyl species in the weathered uncompatibilised and compatibilised composites. SEM examination revealed the presence of surface defects such as cracking, tiny holes and degraded fibre, which explain the poor performance of the composites upon weathering.     

Recycled Natural Fiber Polypropylene Composites: Water Absorption/Desorption Kinetics and Dimensional Stability

Detailed analysis of the effects of recycling process on long-term water absorption, thickness swelling and water desorption behavior of natural fiber polypropylene composites is reported. Composite materials containing polypropylene and wood flour, rice hulls or bagasse fibers were produced at constant fiber loading and were exposed to a simulated recycling process consisting of up to five times grinding and reprocessing under controlled conditions. A wide range of analytical methods including water absorption/desorption tests, thickness swelling tests, density measurement, scanning electron microscopy, image analysis, contact angle, fiber length analysis and Fourier transform infrared spectroscopy was employed to understand the hygroscopic behavior of the recycled composites. Water absorption and thickness swelling behaviors were modeled using existing predictive models. Results indicated that generally the recycled composites had considerably lower water absorption and thickness swellings as compared with the original composites which were attributed to changes in physical and chemical properties of the composites induced by the recycling process.     

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.     

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.     

Degradation Kinetics of Biodegradable Fiber Composites

In a composite, fast degradable fibers determine the degradation of the slowly degradable matrix. Such biodegradable composites consisting of degummed hemp fibers and a polyester amide matrix were produced with fiber mass fractions between 0 and 0.48. The hot-pressed plates, 1-mm thick, were incubated in a standard soil. The degradation kinetics was quantified by the measurement of CO₂ production. Furthermore, after termination of experiment, the carbon balance was uncovered. The results were fitted to an exponential law taking into account the degradation of fibers. The increased amount of pores realized by high fiber contents induces pronounced degradation. The degradation is fully characterized by the time constant , which is correlated to the fiber mass fraction. The model allows to predict the degradation kinetics of composites with a few well-defined experiments.     

Man-Made and Natural Fibres as a Reinforcement in Fully Biodegradable Polymer Composites: A Concise Study

Biodegradable and ecologically friendly polymer materials attract great attention of many scientific groups in the world as they fit well in the sustainable development policy and are considered to be “a right thing to do” by the general public. Such polymers can be modified by the addition of different fillers, favorably of natural origin. In the paper we provide a comparison between composites based on two biodegradable polymers: poly(lactic acid)—biodegradable, natural stock polymer and poly(butylene succinate)—biodegradable polymer produced from fossil based materials. For each polymer we have prepared a series of composites with different fibres (natural: hemp and flax, and manmade: Cordenka) and different filler loadings. To fully characterize obtained materials thermal, mechanical and surface free energy measurements were performed, completed with morphology observations and an attempt to compare the experimental data for tensile measurements with values obtained using the modified rule of mixtures. The tensile results calculated using the modified rule of mixture for below 30% fibre loading are found to be fitting the experimental data. Composites mechanical properties and morphology were strongly affected by the type of fibre used and its loading, however thermal properties remained almost unchanged. In specific, Cordenka fibres tend to form bunches which presence greatly influences the mechanical properties but still our studies have shown clear advantage of manmade Cordenka fibres over the hemp and flax fibres when considering distribution and fibre–polymer interaction.     

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...     

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.     

Thermoplastic Starch and Mica Clay Composites as Biodegradable Mulching Films

Journal of Polymers and the Environment - Multifunctional horticultural mulches satisfy different agronomic needs: control weeds and insects, reduction of water evaporation and soil erosion, as...     

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.     

Biodegradable Composites Containing Chicken Feathers as Matrix and Jute Fibers as Reinforcement

This research demonstrates that chicken feathers can be used as matrix to develop completely biodegradable composites with properties similar to that of composites having polypropylene (PP) as matrix. Feathers are ubiquitous and inexpensive but have limited industrial applications. Feathers have been preferably used for composite applications due to their low density and presence of hollow structures that facilitate sound absorption. However, previous approaches on using feathers for composites have used the whole feather or the feather fractions as reinforcement with synthetic polymers as matrix resulting in partially degradable composites. In addition, the hydrophilicity of the feathers and hydrophobicity of the synthetic matrix results in poor compatibility and therefore less than optimum properties. Although it has been shown that feathers can be made thermoplastic and suitable to develop films and other thermoplastics, there are no reports on using feathers as matrix for composites. In this research, chicken feathers were used as matrix and jute fibers as reinforcement to develop completely biodegradable composites. Tensile, flexural and acoustic properties of the feather-jute composites were compared to PP-jute composites. Utilizing feathers as matrix could enable us to develop low cost 100 % biodegradable composites containing feathers or other biopolymers as the reinforcement.     

Biodegradable Green Glove Containing Ascorbic Acid from Maleated Epoxidized Natural Rubber/Poly(vinyl alcohol) Blend: Preparation and Physical Properties

Journal of Polymers and the Environment - The objective of this work was to prepare a maleate epoxidized natural rubber (MENR) and poly(vinyl alcohol) (PVA) (MENR/PVA) blend in the presence of...     

Rheological, Mechanical and Thermal Behaviour of Wood Polymer Composites Based on Recycled Polypropylene

The aim of this paper was to investigate the effect of recycled polypropylene (PP) on the rheological, mechanical and thermal properties of wood flour polypropylene composites. Beforehand, the influence of wood flour treated with a coupling agent on the rheological behaviour had been looked at. By analysing moduli and viscosity curves and studying the thermal and mechanical properties of samples with 10% filler it was possible to see that the recycled PP that was added change in either its physical properties or its rheology. In the other wood plastic composites (WPC) studied, slight changes in the rheology behaviour were observed. However, the same processing parameters may be used with and without recycled PP. Recycled PP is appropriate for these kinds of composites to maintain the optimal rheological properties that make it easier to process the material by extrusion. Furthermore, it is also possible to maintain the thermal and mechanical properties in comparison with the behaviour of virgin PP/wood flour composites.     

Compatibilization Improves Performance of Biodegradable Biopolymer Composites Without Affecting UV Weathering Characteristics

With growing interest in the use of eco-friendly composite materials, biodegradable polymers and composites from renewable resources are gaining popularity for use in commercial applications. However, the long-term performance of these composites and the effect of compatibilization on their weathering characteristics are unknown. In this study, five types of biodegradable biopolymer/wood fiber (WF) composites were compatibilized with maleic anhydride (MA), and the effect of accelerated UV weathering on their performance was evaluated against composites without MA and neat biopolymers. The composite samples were prepared with 30 wt% wood fiber and one of the five biodegradable biobased polymer: poly(lactic) acid (PLA), polyhydroxybutyrate (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), Bioflex (PLA blend), or Solanyl (starch based). Neat and composite samples were UV weathered for 2000 h (hours), and characterized for morphological, physical, thermal, and mechanical properties before and after weathering. Compared to composites without MA, composites containing MA grafted polymers exhibited improved properties due to increased interfacial adhesion between the fiber and matrix. Upon accelerated weathering, thermal and mechanical properties of 70% of the samples substantially decreased. Surfaces of all the samples were roughened, and drastic color changes were observed. Water absorption of all the samples increased after weathering exposure. Even though the compatibilization is shown to improve composite properties before weathering, it did not affect weathering of samples, as there were no considerable differences in properties exhibited by the composites with MA and without MA after weathering. The results suggest that compatibilization improves properties of biodegradable biobased composites without affecting its UV degradation properties.     

Recycling Ability of Biodegradable Matrices and Their Cellulose-Reinforced Composites in a Plastic Recycling Stream

The effect of multiple injection-moulding reprocessing of three biodegradable matrices on their mechanical properties, melt flow rate, molecular weight, phase transition temperatures and degradation temperature is presented. It has been found that, with successive reprocessing, tensile, flexural and impact strength decreased. Drop in mechanical properties has been assigned to degradation of the matrices, as corroborated by melt flow and molecular weight analysis. Although reprocessing did not significantly affect the glass transition, it diminished the melting point and degradation temperature of polymers. Results indicate that neat PLLA can be recycled for up to five times without suffering a drastic loss in mechanical and thermal properties. The aliphatic polyester Mater-Bi TF01U/095R can be recycled for up to 10 times, whilst starch-based Mater-Bi YI014U/C wastes should be destined to composting, since its recyclability is very poor. The effect of reprocessing on composites reinforced with chemithermomechanical pulp (CTMP) followed the tendencies observed for the neat matrices. Whilst CTMP-fibres behave mainly as filler in PLLA composites, reinforced thermoplastic starch-based composites presented enhanced mechanical properties and recyclability.     

The Shape Memory Properties of Biodegradable Chitosan/Poly(l-lactide) Composites

The shape memory behavior of PLLA (poly(l-lactide)) and chitosan/PLLA composites was studied. PLLA and chitosan were compounded to fabricate novel materials which may have biodegradability and biocompatibility. Chitosan does not significantly affect the glass and melting transition temperature of the PLLA. Both the pure PLLA and chitosan/PLLA composites showed shape memory effect arising from the viscoelastic properties of PLLA comprised of semi crystalline structures. The shape recovery ratio of the chitosan/PLLA composites decreased significantly with increasing chitosan contents due to the incompatibility between PLLA and chitosan. Phase separation structures of the composites were observed by using atomic force microscopy. To obtain good shape memory effect, the chitosan content should be below 15 wt%.     

Characterization of Biodegradable Polymer Blends of Acetylated and Hydroxypropylated Sago Starch and Natural Rubber

Development of biodegradable polymers from absolute environmental friendly materials has attracted increasing research interest due to public awareness of waste disposal problems caused by low degradable conventional plastics. In this study, the potential of incorporating natural rubber latex (NRL) into chemically modified sago starch for the making biodegradable polymer blends was assessed. Native sago starch was acetylated and hydroxypropylated before gelatinization in preparing starch thermoplastic using glycerol. They were than casted with NRL into biopolymer films according to the ratios of 100.00/0.00, 99.75/1.25, 98.50/2.50, 95.00/5.00, 90.00/10.00 and 80.00/20.00 wt/wt, via solution spreading technique. Water absorption, thermal, mechanical, morphological and biodegradable properties of the product films were evaluated by differential scanning calorimetry (DSC), universal testing machine (UTM), scanning electron microscopy (SEM) and fourier transform infrared spectroscopy. Results showed that acetylation promoted the incorporating behavior of NRL in sago starch by demonstrating a good adhesion characteristic and giving a uniform, homogenous micro-structured surface under SEM observation. However, the thin biopolymer films did not exhibit any remarkable trend in their DSC thermal profile and UTM mechanical properties. The occurrence of NRL suppressed water adsorption capacity and delayed the biodegradability of the biopolymer films in the natural environment. Despite the depletion in water adsorption capacity, all of the product films degraded 50 % within 12 weeks. This study concluded that biopolymers with desirable properties could be formulated by choosing an appropriate casting ratio of the sago starch to NRL with suitable chemical substitution modes.     

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.