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.     

Preliminary Study of Non-woven Composite: Effect of Needle Punching and Kenaf Fiber Loadings on Non-woven Thermoplastic Composites Prepared From Kenaf and Polypropylene Fiber

Non-woven composites were produced using kenaf (bast) fiber and polypropylene (PP) fiber. The effects of needle punching process, number of needle and kenaf fiber loadings on the properties of non-woven composite were studied. The aspect ratio of kenaf fiber was also measured in this study. The aspect ratio of most of kenaf fiber used was in the range of 200–400. The results indicated that the mechanical strength of the non-woven composite was significantly influenced by the percentage of kenaf fiber. This may due to the evenly mixed kenaf and PP fibers during carding process prior to the mechanical interlocking by needle punching process. The tensile strength, modulus and toughness were enhanced with the incorporation of carded and needle punched fibers. The number of needle used in needle punching process had a significant effect on the strength of the composite. This was evident in SEM micrograph where composite prepared from carded to needle punched non-woven web showed better wettability as compared to composite prepared from carded non-woven web only. However, no significant difference was observed in water absorption and thickness swelling tests for composites prepared with different number of needles.     

Fabrication Mechanical Properties of Unidirectional Jute/PP Composites Using Jute Yarns by Film Stacking Method

This paper mainly focuses on the fabrication process of long fibre reinforced unidirectional thermoplastic composites made using both natural (untreated) treated jute yarns. Jute yarns were wound in layers onto a metallic frame. Polypropylene films were inserted between these layers and compression moulded to fabricate unidirectional jute/PP composite specimens. Static mechanical properties were evaluated from tensile three point bending tests. Pre- post-failure examination were carried out on the test specimens using optical scanning electron microscopy to analyse the test results and investigate the correlations between their impregnation state, processing conditions, mechanical performances and fracture morphologies. For the unidirectional jute/PP film-stacked composites, the results indicated that the processing condition at the moulding temperature of 160°C and moulding pressure of 2.0 MPa for 15 min was ideally suited to obtain optimized properties. Improved wettability of resin melts due to complete matrix fusion at this processing condition facilitated thorough impregnation with minimum microstructural imperfections (microvoids) being generated. Jute/PP composites that contained treated jute yarns have shown superiority in tensile bending properties. Jute yarns polished or coated with PVA/PP (polyvinyl alcohol/polypropylene) must have contributed positively to fibre/matrix interfacial interactions leading to matrix to fibre effective stress transfer, thereby improving their reinforcing effects. Tensile strength and modulus of PP resin increased by approximately 285% and 388%, respectively, due to 50 wt% reinforcement by natural jute yarns. Further improvements in strength and modulus were achieved by approximately 14% and 10%, respectively, when treated yarns were used . The maximum bending stress modulus of jute/PP composites containing untreated yarns were approximately 190% and 460% higher than those of the virgin PP materials, and bending properties were improved by further 11% and 23%, respectively, due to coating treatments on the yarn surface.     

Mechanical Properties of Poly (Lactic Acid)/Hemp Fiber Composites Prepared with a Novel Method

This research dealt with a novel method of fabricating green composites with biodegradable poly (lactic acid) (PLA) and natural hemp fiber. The new preparation method was that hemp fibers were firstly blending-spun with a small amount of PLA fibers to form compound fiber pellets, and then the traditional twin-screw extruding and injection-molding method were applied for preparing the composites containing 10–40 wt% hemp fibers with PLA pellets and compound fiber pellets. This method was very effective to control the feeding and dispersing of fibers uniformly in the matrix thus much powerful for improving the mechanical properties. The tensile strength and modulus were improved by 39 and 92 %, respectively without a significant decrease in elongation at break, and the corresponding flexural strength and modulus of composites were also improved by 62 and 90 %, respectively, when the hemp fiber content was 40 wt%. The impact strength of composite with 20 wt% hemp fiber was improved nearly 68 % compared with the neat PLA. The application of the silane coupling agent promoted further the mechanical properties of composites attributed to the improvement of interaction between fiber and resin matrix.     

Study of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/Bamboo Pulp Fiber Composites: Effects of Nucleation Agent and Compatibilizer

In this study, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/bamboo pulp fiber (BPF) composites were prepared by melt compounding and injection molding. The crystallization ability, tensile strength and modulus, flexural strength and modulus, and impact strength were found substantially increased by the addition of BPF. Tensile and flexural elongations were also moderately increased at low fiber contents (<20%). BPF demonstrated not only higher strength and modulus, but also higher failure strain than the PHBV8 matrix. Boron nitride (BN) was also investigated as a nucleation agent for PHBV8 and maleic anhydride grafted PHBV8 (MA-PHBV8) as a compatibilizer for the composite system. BN was found to increase the overall properties of the neat polymer and the composites due to refined crystalline structures. MA-PHBV8 improved polymer/fiber interactions and therefore resulted in increased strength and modulus. However, the toughness of the composites was substantially reduced due to the hindrance to fiber pullout, a major energy dissipation source during the composite deformation.     

Effect of Fiber Surface Treatments on Thermo-Mechanical Behavior of Poly(Lactic Acid)/Phormium Tenax Composites

In the present study, Phormium Tenax fiber reinforced PLA composites were processed by injection molding and twin screw compounding with a fiber content ranging from 10 to 30 wt%. Three surface treatment methods have been used to improve the Phormium Tenax fiber-matrix interfacial bonding that are as follows: (1) aqueous alkaline solution, (2) silane coupling agent, and (3) a combination of alkaline and silane treatment. The mechanical, thermal and morphological properties of the resulting composites were investigated. The results have shown that the moduli of surface treated fiber reinforced composites are lower than the ones obtained for untreated composites (as a consequence of the decrease in fiber modulus caused by the chemical treatments) and no significant increase in strength was observed for any of the composites compared to neat PLA. SEM micrographs of composite fractured surfaces confirmed an improvement in the interfacial strength, which was insufficient nonetheless to significantly enhance the mechanical behavior of the resulting composites. Results from thermogravimetric analysis and differential scanning calorimetry suggest that surface treatment of Phormium affects the ability of PLA to cold crystallize, and the thermal stability of the composites at the different fiber contents was reduced with introduction of alkali and silane treated Phormium fibers.     

Mechanical Recycling of PLA Filled with a High Level of Cellulose Fibres

Composites consisting of 30 vol% PLA and 70 vol% cellulose fibres were prepared with compression moulding. In the first part of the study, the recyclability of this composite material was investigated by grinding the material and using the recyclate obtained as a filler for PLA. Thus, the recyclate was compounded with PLA in loadings ranging from 20 to 50 wt%. The composites obtained were characterised by tensile tests, Charpy impact tests, DMTA, and SEM. Tests showed that the recyclate had a relatively good reinforcing effect. Stress at break increased from about 50 to 77 MPa and the modulus increased from 3.6 to 8.5 GPa. In the second part of the study, the ability to mechanically recycle the composites obtained was evaluated by repeated processing. Composite with two loadings of the recyclate (20 wt% and 50 %) was injection moulded repeatedly, six times. Tests showed that the composite material with 20 wt% recyclate could withstand six cycles relatively well, while the composite with the higher load degraded much more quickly. For the composites with 50 wt% recyclate, signs of polymer degradation could be seen already after reprocessing the composite once.     

Natural Fiber Reinforced Poly(vinyl chloride) Composites: Effect of Fiber Type and Impact Modifier

Poly(vinyl chloride) (PVC) and natural fiber composites were prepared by melt compounding and compression molding. The influence of fiber type (i.e., bagasse, rice straw, rice husk, and pine fiber) and loading level of styrene-ethylene-butylene-styrene (SEBS) block copolymer on composite properties was investigated. Mechanical analysis showed that storage modulus and tensile strength increased with fiber loading at the 30% level for all composites, but there was little difference in both properties among the composites from various fiber types. The use of SEBS decreased storage moduli, but enhanced tensile strength of the composites. The addition of fiber impaired impact strength of the composites, and the use of SEBS led to little change of the property for most of the composites. The addition of fiber to PVC matrix increased glass transition temperature (T_g), but lowered degradation temperature (T_d) and thermal activation energy (E_a). After being immersed in water for four weeks, PVC/rice husk composites presented relatively smaller water absorption (WA) and thickness swelling (TS) rate compared with other composites. The results of the study demonstrate that PVC composites filled with agricultural fibers had properties comparable with those of PVC/wood composite.     

Stiff Biodegradable Polylactide Composites with Ultrafine Cellulose Filler

Polylactide (PLA) composites with 10–30 wt% of commercial fine grain filler of native cellulose were prepared by melt-mixing, and examined. The composite films had esthetic appearance, glossy surface, creamy color and density close to that of neat PLA. Good dispersion of the filler in PLA matrix was achieved. The composites were stiffer than neat PLA; in the glassy region the storage modulus increased by approx. 30 %. The tensile strength of the composite materials in the temperature range from 25 to 45 °C was similar to that of neat PLA. No marked decrease in molar mass of PLA in the composites occurred during processing in comparison to neat PLA. Moreover, thermogravimetry experiments demonstrated good thermal stability of the composites; 5 % weight loss occurred well above 300 °C.     

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.     

Processing and Characterization of Short-Fiber Reinforced Jute/Poly Butylene Succinate Biodegradable Composites: The Effect of Weld-Line

Fabrication of complex injection molded parts often involves the use of multiple gates. In such situations, polymer melts from different gates meld to form the molded part (weld line). This paper reports on the fabrication and characterization of the mechanical and morphological properties of short fiber reinforced jute/poly butylene succinate (PBS) biodegradable composites. The effect of a dual gated mold in the fabrication of welded specimens was a key focus of the investigation. It was observed that incorporation of jute fiber (10 wt%) conferred drastic changes on the stress–strain properties of the matrix as the elongation at break (EB), dropped from 160% in the matrix to just 10% in the composite. The tensile strength of the composite was lower than that of the matrix. However, it is noteworthy that the tensile modulus of the composite increased. Bending test also revealed that both bending strength and modulus increased with the incorporation of jute. Morphological studies of the tensile fracture surface using SEM revealed two types of failure mode. Ductile failure was indicated by plastic deformation at the initiation of fracture followed by brittle failure. The good interfacial bonding indicated between jute and PBS was attributed to positive interaction between the two polar polymers. A comparison of the non-weld and weld-line samples revealed that the weld-line composites have better mechanical integrity than the corresponding polymer matrix with weld line. The results also revealed that elongation at break and toughness are most sensitive to the presence of the weld-line whereas flexural properties are least sensitive.     

Feather Fiber Reinforced Light-Weight Composites with Good Acoustic Properties

Three to four billion pounds of chicken feathers are wasted in the United States annually. These feathers pose an environmental challenge. In order to find a commercial application of these otherwise wasted feathers, composites have been prepared from feathers. Flexural, impact resistance, and sound dampening properties of composites from chicken feather fiber (FF) and High Density Polyethylene/Polypropylene (HDPE/PP) fiber have been investigated and compared with pulverized chicken quill-HDPE/PP, and jute-HDPE/PP composites. Sound dampening by FF composites was 125% higher than jute and similar to quill although mechanical properties were inferior to the latter two. In ground form, FF and jute composite properties were similar except for 34% higher modulus of jute; under the same formulation and processing conditions, ground FF composites had nearly 50% lower mechanical properties compared with ground quill composites. It was found that voids and density of composites have effect on mechanical and sound dampening properties; however, no direct relationship was found between mechanical properties and sound dampening.     

Bamboo–Fiber Filled High Density Polyethylene Composites: Effect of Coupling Treatment and Nanoclay

High density polyethylene (HDPE)/bamboo composites with different nanoclay and maleated polyethylene (MAPE) contents were fabricated by melt compounding. The compounding characteristics, clay dispersion, HDPE crystallization, and mechanical properties of the composites were studied. The equilibrium torque during compounding decreased with use of clay masterbatch and increased with the addition of MAPE. The X-ray diffraction (XRD) data showed that the clay was exfoliated only when 1% clay was added to pure HDPE without MAPE. For HDPE/bamboo systems, MAPE was necessary to achieve clay exfoliation. For pure HDPE system, both dynamic and static bending moduli increased, while impact strength decreased with increased clay loading. For the HDPE/bamboo fiber composites, tensile strength, bending modulus and strength were improved with the use of MAPE. The use of the clay in the system led to reduced mechanical properties. Techniques such as pre-coating fibers with clay–MAPE mixture are needed to enhance the synergetic effect of the clay and bamboo fiber on the composite properties in the future study.     

Mechanical,Morphological and Dynamic Mechanical Analysis of Pineapple Leaf/Washingtonia Trunk Fibres Based Biophenolic Hybrid Composites

In this article, flexural, impact and dynamic mechanical properties of the Pineapple leaf fibres (PALF) and Washingtonia trunk fibres (GW) based bio-phenolic hybrid composites were examined. The pure and hybrid composites were fabricated using the hand lay-up technique with an overall fibre weight ratio of 50% in which GW and PALF were maintained in the fibre weight ratios of 50:50, 30:70, and 70:30 denoted as 1G1P, 3G7P, and 7G3P, respectively. Hybrid composites displayed better flexural strength, flexural modulus and impact strength than the GW composites and better viscoelastic properties than the PALF composites. Results revealed that 1G1P hybrid composites exhibited 25% and 12% improvements in flexural strength and modulus compared to the GW composites. 3P7K composites showed a twofold increase in impact strength than GW composites. The storage modulus of the pure and hybrid composites declined rapidly beyond the glass transition temperature. Furthermore, it was observed that the values of storage modulus for all the composites at 150 °C were similar regardless of the composite configuration. The Peak of loss modulus was found to increase in the following order: GW?>?7G3P?>?3G7P?>?1G1P?>?PALF. Furthermore, the temperature at the peak tan delta was improved, and a reduction in the tan delta peak was observed for hybrid composites compared to the pure composites. Finally, the PALF and GW hybrid combinations can be suitable for use in various applications such as textiles, machinery part production industries, medicine, automobiles, etc.

     

New Multi-Scale Hybrid System Based on Maple Wood Flour and Nano Crystalline Cellulose: Morphological,Mechanical and Physical Study

In the first part of this work, composites based on polypropylene (PP) and maple wood flour (MF) were prepared by melt compounding using twin-screw extrusion followed by compression molding. The morphological and mechanical properties of the composites were analyzed for three samples: PP, MF/PP and MF/PP containing maleic anhydride grafted polypropylene (MAPP) as coupling agent. The results showed that MF/PP composites have improved mechanical properties, especially tensile modulus (+33 %), with only 8 % increase in density. The addition of MAPP further improved the mechanical properties, in particular tensile modulus (up to 51 %), which could be related to better fiber/matrix adhesion. In the second step, nano crystalline cellulose (NCC) was added to all samples to produce NCC-MF/PP hybrid composites. From the mechanical analysis performed, the hybrid composites with MAPP have improved properties, especially tensile (+53 %) and flexural (+40 %) moduli. These results confirmed that multi-scale hybrid NCC-MF composites can substantially improve the mechanical properties of polyolefins with limited increase in density (14 %) leading to high specific properties.     

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.     

Mechanical Properties of Microcrystalline Cellulose (MCC) Filled Engineering Thermoplastic Composites

In this study, engineering thermoplastic composites were prepared from microcrystalline cellulose (MCC)-filled nylon 6. MCC were added to nylon 6 using melt mixing to produce compounded pellets. The MCC-filled nylon 6 composites with varying concentrations of MCC (from 2.5 to 30 wt%) were prepared by injection molding. The tensile and flexural properties of the nylon 6 composites were increased significantly with the addition of MCC. The maximum strength and modulus of elasticity for the nylon 6 composites were achieved at a MCC weight fraction of 20 %. The Izod impact strength of composites decreased with the incorporation of MCC without any surface treatments and coupling agent. This observation is quite expected for filled polymer systems and has been commonly observed. There was a strong correlation between density and tensile (r = 0.94) and flexural modulus of elasticity (r = 0.9). MCC filled composites manufactured by injection method had highly uniform density distribution through their thickness. The higher mechanical results with lower density demonstrate that MCC can be used as a sufficient reinforcing material for low cost, eco-friendly composites in the automotive industry especially for under-the-hood applications (engine covers, intake manifolds and radiator end tanks) as well as in other applications such as the building and construction industries, packaging, consumer products etc.     

Cellulose Fiber/Bentonite Clay/Biodegradable Thermoplastic Composites

Adding cellulose fiber reinforcement can improve mechanical properties of biodegradable plastics, but fiber must be well dispersed to achieve any benefit. The approach to dispersing fiber in this study was to use aqueous gels of sodium bentonite clay. These clay-fiber gels were combined with powdered compostable thermoplastics and calcium carbonate filler. The composite was dried, twin-screw extruded, and injection molded to make thin parts for tensile testing. An experimental design was used to determine the effect of fiber concentration, fiber length, and clay concentration. Polybutylene adipate/terephthalate copolymer (PBAT) and 70/30 polylactic acid (PLA)/PBAT blend were the biodegradable plastics studied. The composite strength decreased compared to the thermoplastics (13 vs. 19 MPa for PBAT, 27 vs. 38 MPa for the PLA/PBAT blend). The composite elongation to break decreased compared to the thermoplastics (170% vs. 831% for PBAT, 4.9% vs. 8.7% for the PLA/PBAT blend). The modulus increased for the composites compared to the thermoplastic standards (149 vs. 61 MPa for PBAT, 1328 vs. 965 MPa for the PLA/PBAT blend). All composite samples had good water resistance.     

Injection Molded Wheat Straw and Corn Stem Filled Polypropylene Composites

Environmentally friendly composite materials can be prepared using wood fibers and/or various types of agro-derived fibers as reinforcements. In this study, agro-residues such as wheat straw and corn stem filled polypropylene were prepared and their suitability was investigated as a reinforcing filler in thermoplastics and as an alternative to the wood flour filled plastics. Effect of compounding techniques, compatibilizer and fungal treatment of agro-residues on the mechanical properties of the composites were evaluated. It was found that high shear compounding of wheat straw fibers exhibited similar properties to that produced by the milled wheat straw. This may be due to the extensive fiber breakage occurred during the high shear compounding that results in a similar aspect ratio to that of milled straw. Compatibilizer is needed for improving the strength properties of the agro-residue filled PP composites. Fungal treatment of milled wheat straw did not show much improvement in the strength properties of the composites. Comparison of mechanical properties of the agro-residue filled PP with that of the wood flour and the old newsprint filled PP showed the suitability of the agro-residues as alternative filler for thermoplastics.     

Sustainable Use of Coffee Husks For Reinforcing Polyethylene Composites

The utilization of the coffee husk fiber (CHF) from the coffee industry as a reinforcing filler in the preparation of a cost-effective thermoplastic based composite was explored in this study. The chemical composition and thermal properties of the CHF were investigated and compared with those of wood fiber (WF). CHF proved to be mainly composed of cellulose, hemicellulose and lignin, and exhibited similar thermal behavior to WF. High density polyethylene (HDPE) composites with CHF loadings of from 40 to 70% were prepared using melt processing and extrusion. The processing properties, mechanical behavior, water absorption and thermal performance of these composites were investigated. The effect of maleated polyethylene (MAPE) used as a coupling agent on the composite was explored. The experimental results showed that increasing the CHF loading in the HDPE matrix resulted in an increase in the modulus and thermal properties of the composites, but resulted in poor water resistance. The addition of a 4% MAPE significantly improved the interfacial behavior of the hydrophilic lignocellulosic fiber and the hydrophobic polymer matrix.