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.     

Effects of Waste Paper Sludge on the Physico-Mechanical Properties of High Density Polyethylene/Wood Flour Composites

The objective of this work was to determine some physical and mechanical properties of the high density polyethylene (HDPE) composites reinforced with various mixtures of the paper sludge and the wood flour, and to evaluate the coupling agent performance. The waste sludge materials originating from two different sources including paper making waste water treatment sludge (PS) and ink-eliminated sludge (IES) were characterized in terms of physico-chemical properties. In the experiment, four levels of paper sludge (20, 30, 40 and 60 wt%), three levels of wood flour (20, 40 and 60 wt%), and two levels of coupling agent (MAPE) content (2 and 3 wt%) were used. The flexural properties of the composites were positively affected by the addition of the sludge. Especially, tensile modulus improved with the increase of paper sludge content. With the addition of MAPE, flexural properties improved considerably compared with control specimens (without any coupling agent). The results showed that the water absorption (WA) and thickness swelling (TS) values of the samples decreased considerably with increasing sludge content in the composite, while they increased with increasing wood flour content. It is to be noted that with incorporation of MAPE in the composite formulation, the compatibility between the wood flour and HDPE was enhanced through esterification, which reduced the WA and TS and improved the mechanical properties. Composites made with IES exhibited superior physico-mechanical properties compared with the PS filled composites. Overall results suggest that the waste paper sludge materials were capable of serving as feasible reinforcing fillers for thermoplastic polymer composites.     

Effect of Nano-SiO<Subscript>2</Subscript> and Bark Flour Content on the Physical and Mechanical Properties of Wood–Plastic Composites

The aim of this study is to evaluate the impact of nano-SiO₂ and bark flour (BF) on the natural fiber–plastic composites engineering properties made from high density polyethylene (HDPE) and beech wood flour (WF). For this purpose, WF and BF in 60 mesh size and weight ratio of (50, 0 %), (30, 20 %), (10, 40 %) and (0, 50 %) respectively were mixed with HDPE. In order to increase the interfacial adhesion between the filler and the matrix, the maleic anhydride grafted polyethylene was constantly used at 3 wt% for all formulations as a coupling agent. The nano-SiO₂ particles with weight ratio of 0, 1, 2, and 4 % were also utilized to enhance the composites properties. The materials were mixed in an internal mixer (HAAKE) and then the bark and/or wood–plastic composite samples were made utilizing an injection molding machine. The physical tests including water absorption and thickness swelling, and mechanical tests including bending characteristics and un-notched impact strength were carried out on the samples based on ASTM standard. The results indicated that as the BF content increased in the composite, mechanical and physical properties were reduced, but the given properties were increased with the addition of nano-SiO₂. The addition of nano-SiO₂ had a negative impact on the physical properties, but when it was up to 2 %, it increased the impact strength.     

Effect of Lignocellulosic Type on Long-Term Hygroscopic Behavior of Natural Filler/HDPE Composites

Natural filler/high density polyethylene (HDPE) injection-molded composites of flour from different lignocellulosic sources were prepared, and their long-term water absorption and thickness swelling were studied. Filler samples from wheat straw, hybrid Euro-American poplar, and loblolly pine were mixed with the matrix at 35 wt% lignocellulosics content and either zero or 2% maleic anhydride grafted polyethylene (MAPE) as compatibilizer. Results indicated water absorption of all the composites followed the kinetics of a Fickian diffusion process. The water diffusion coefficient of the composites was clearly dependent upon the lignocellulosic type. The wheat straw composites showed the highest and the pine composites exhibited the lowest water absorption coefficients. The highest thickness swelling took place in the wheat straw composites, followed by the poplar and pine composites, respectively. Adding MAPE to the composites decreased the water diffusion coefficient and thickness swelling by improving the adhesion between natural filler and the HDPE.     

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.     

Thermally Stable Pyrolytic Biocarbon as an Effective and Sustainable Reinforcing Filler for Polyamide Bio-composites Fabrication

Natural fibers are limited in their use as reinforcement to commodity polymers. They cannot be used to reinforce engineering polymers due to their low thermal stability at high processing temperatures. This study presents an approach to successfully reinforce polyamides using a derivative of natural fibers as reinforcement without the effects of thermal degradation during melt processing. Biocarbon from miscanthus fibers was used to reinforce polyamide 6 up to 40 wt%. At 40 wt% filler content, the tensile and flexural strengths increased by 19.6 and 47% respectively in comparison to the neat polyamide. The moduli were also increased by 31.5 and 63.7% respectively. A maximum increase in impact strength of 43.7% was achieved at 20 wt% biocarbon loading. The morphology of the tensile fractured samples showed stretched polyamide ligaments attached to the biocarbon particles, indicating the presence of interaction between filler and matrix. Interestingly, more bonded interfaces were observed between the polyamide and biocarbon particles with increasing biocarbon content possibly stemming from increased biocarbon surfaces with functional groups. These composites show great potential to substitute in part or whole, some particulate filled polyamides currently used in the automotive industry.     

Fiber from DDGS and Corn Grain as Alternative Fillers in Polymer Composites with High Density Polyethylene from Bio-based and Petroleum Sources

The steady increase in production of corn based ethanol fuel has dramatically increased the supply of its major co-product known as distiller’s dried grain with solubles (DDGS). Large amount of DDGS and corn flour are used as an animal feed. The elusieve process can separate DDGS or corn flour into two fractions: DDGS fraction with enhanced protein and oil content or corn flour fraction with high starch content, and hull fiber. This study investigated the feasibility of using fiber from DDGS and corn grain as alternative fillers to wood fiber in high density polyethylene (HDPE) composites made with two different sources of polymers. Two fiber loading rates of 30 and 50% were evaluated for fiber from DDGS, corn, and oak wood (control) to assess changes in various physical and mechanical properties of the composite materials. Two HDPE polymers, a bio-based HDPE made from sugarcane (Braskem), and a petroleum based HDPE (Marlex) were also compared as substrates. The biobased polymer composites with DDGS and corn fibers showed significantly lower water absorption than the Marlex composite samples. The Braskem composite with 30% DDGS fiber loading showed the highest impact resistance (80 J/m) among all the samples. The flexural properties showed no significant difference between the two HDPE composites.     

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.     

Processing Stability and Biodegradation of Polylactic Acid (PLA) Composites Reinforced with Cotton Linters or Maple Hardwood Fibres

Polylactic acid (PLA) composites comprising up to 25 wt% cotton linter (CL) or up to 50 % maple wood fibre (WF) were prepared by compounding and injection moulding. A reduction of crystallinity in the PLA matrix was observed as a result of the thermal processing method. These PLACL and PLAWF composites provided excellent improvements in both stiffness (with increases in tensile and flexural modulus) and toughness (increases in notched impact strength) properties over the neat PLA resin, while the tensile and flexural strengths of the composites were generally unchanged, while the strain at break values were reduced in comparison to the neat PLA. DMA results indicated incorporating these fibres caused the mechanical loss factor (tan δ) to decrease, suggesting better damping capabilities were achieved with the composites. SEM analysis of the impact fractured surfaces of the PLACL composites showed debonding-cavitation at the matrix-fibre interface while the PLAWF composites showed good wetting along its matrix-fibre interface. The composting of these composites up to 90 days showed that the degradation onset time was increased when increasing the fibre loadings, but the maximum degree of degradation and the maximum daily rates of degradation were decreased compared to neat PLA. On a weight basis of fibre loading, the PLACL composites had a quicker onset of biodegradation, a higher maximum daily rate of biodegradation and, overall, a higher degree of biodegradation at 90 days than the PLAWF composites, possibly due to the quicker thermal hydrolysis observed in the PLA matrix of the PLACL composites during processing and composting.     

Synergistic Effect of Oil Palm Based Pozzolanic Materials/Oil Palm Waste on Polyester Hybrid Composite

This research work aims to investigate the synergistic effect of pozzolanic materials such as oil palm ash (OPA) and oil palm empty fruit bunch (OPEFB) on the developed hybrid polymer composites. The OPEFB and OPA fillers of different particle sizes (250, 150, and 75 µm) were mixed at OPEFB:OPA ratios of (0:100; 20:80; 40:60; 60:40; 80:20 and 100:0) and incorporated into an unsaturated polyester resin. Furthermore, both mechanical and morphological properties of the composites were analyzed and it was found that tensile, flexural, and impact properties were significantly improved at OPEFB:OPA of 75 µm particle size hybridization of the polymer. The increase of OPEFB to OPA filler ratio up to 80:20 significantly improved the tensile properties of the composites while 40:60 ratio of 75 µm gave the optimum filler ratio to obtain the highest flexural and impact properties of the composites among all studied samples. Scanning electron micrograph images showed strong particle dispersion of the embedded fillers with resin which explained the excellent mechanical strength enhancement of the composite.     

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.     

Utilization of Sunflower Stalk in Manufacture of Thermoplastic Composite

Dimensional stability and mechanical performance of polypropylene thermoplastic composites filled with sunflower stalk (SS) flour at 30, 40, 50, and 60 wt% contents of the SS flour were investigated. The thickness swelling and water absorption of the specimens increased with increasing SS flour content. The modulus in the flexural and tensile improved with increasing SS flour content while the tensile and flexural strengths of the specimens decreased. The use of maleic anhydride polypropylene (3 wt%) had a positive effect on the dimensional stability and mechanical properties of the polypropylene thermoplastic composites filled with SS flour. The melting temperature of polypropylene decreased with increasing content of the SS flour. The degree of crystallinity of filled polypropylene composites between fibre loading of 0–30 % by weight was higher than that of unfilled polypropylene composites. However, further increment in the filler content decreased the degree of crystallinity. The obtained results showed that SS flour could be potentially suitable raw material in the manufacture of polypropylene composites.     

Effect of Hydrothermal Aging on Injection Molded Short Jute Fiber Reinforced Poly(Lactic Acid) (PLA) Composites

This work focused on the durability of short jute fiber reinforced poly(lactic acid) (PLA) composites in distilled water at different temperatures (23, 37.8 and 60 °C). Morphological, thermal and mechanical properties (tensile, flexural, and impact) of jute/PLA composites were investigated before and after aging. Different from traditional synthetic fiber reinforced polymer composites, the stability of jute/PLA composites in water was significantly influenced by hydrothermal temperature. The mechanical properties of the composites and molecular weight of PLA matrix declined quickly at 60 °C, however, this process was quite slower at temperatures of 23 and 37.8 °C. Impact properties of the composites were hardly decreased, but the tensile and flexural properties suffered a drop though to various degrees with three degradation stages at 23 and 37.8 °C. The poor interface of composites and the degradation of PLA matrix were the main damage mechanism induced by hydrothermal aging. Furthermore, considering the hydrolysis of PLA matrix, the cleavage of PLA molecular chain in different aging time was quantitatively investigated for the first time to illustrate hydrolysis degree of PLA matrix at different aging time.     

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.     

Performance of Cow Dung Reinforced Biodegradable Poly(Lactic Acid) Biocomposites for Structural Applications

In this work, performance of cow dung (CD) reinforced poly(lactic acid) (PLA) biocomposites was investigated for the potential use in load bearing application. CD of average 4 mm size was blended with PLA at different CD ratios (0–50 wt%) and their effects on the biocomposite properties were studied. The results showed an improvement in the flexural properties, while the tensile and impact strength dropped by 20 and 28% with the addition of 50% CD. The decline in the tensile and impact strength was due to micro-cracking and voids formation at higher CD content. Also, the incorporation of CD slightly decreased the thermal stability of the biocomposite. However, dynamic mechanical properties of the biocomposites generally improved. SEM analysis of tensile and impact fractured surfaces indicated that the CD had a reasonable adhesion with matrix. Moreover, the SEM micrographs of soil burial studies showed an accelerated degradation of higher CD wt% biocomposites.     

Thermal,Rheological, Mechanical and Morphological Behavior of High Density Polyethylene and Carboxymethyl Cellulose Blend

In this study water soluble sodium carboxymethyl cellulose (CMC) was blended with high density polyethylene (HDPE) by peroxide-initiated melt compounding technique. The compatibility of the blended polymers were carried out by silane crosslinking agent. A series of blends were prepared by varying the CMC contents up to a maximum of 50 phr. The physical properties of non-crosslinked and crosslinked blends were investigated in detail. FTIR analysis of crosslinked blend confirmed the presence of Si–O–Si and Si–O–C absorption peaks at 1050 and 1159 cm^?1. Thermal stability of crosslinked blends improved as compared to its non-crosslinked congener. Rheological study of crosslinked blends illustrated high complex viscosity and dynamic shear storage modulus. The tensile strength of virgin polyethylene was 8.1 MPa whereas the maximum tensile strength of 19.6 MPa was observed in crosslinked blend. Similarly lower deformation was observed in crosslinked blends under static load. Scanning electron microscopy of crosslinked formulations also showed strong adhesion between the polymers interface. The compatibility of HDPE and CMC is attributed to both free radical and condensation reactions.     

New Non-food-Based Composites of Acorn Nutlet and Polycaprolactone: Preparation and Characterization Evaluation

Two dissimilar renewable resource-based thermoplastic acorn nutlet (TPAN) materials were prepared via twin-screw extrusion with the aid of glycerol or monoethanolamine as plasticizers, and then two TPAN/polycaprolactone (PCL) composites with different plasticized systems were prepared. Mechanical test showed that glycerol-based composites had excellent tensile properties, and at a PCL content of 50 wt%, their tensile strength and elongation at break reached 14.4 MPa and 1,361 %, respectively. The micro-morphologic investigation of liquid-nitrogen brittle fracture surface indicated certain interface adhesion between glycerol-based thermoplastic acorn nutlet (GTPAN) and PCL. Dynamic mechanical thermal analysis , differential scanning calorimetry and thermogravimetric analysis demonstrated that the weight ratios of TPAN in composites significantly affected the crystallinity, glass transition temperature (T_g), melting temperature (T_m) and thermal stability of composites. Soil burial degradation analysis displayed that all composites had excellent biodegradability. These results demonstrated that GTPAN/PCL composites had superior mechanical and biodegradable properties, enough to partially replace the conventional thermoplastic plastics.     

Preparation and Characterization of PVC Matrix Composites with Biochemical Sludge

Biochemical sludge (BS), generated in the waste water treatment of paper mills, was pretreated by enzyme hydrolysis. The effect and action mechanism of the enzymatic treatment on the properties of polyvinyl chloride (PVC) matrix composites with BS were discussed. Results showed that when the filler content was 30 wt%, the tensile strength of the PVC composites filled with BS and its modified products which were pretreated by laccase, cellulase and hemicellulase can be increased by 38.64, 67.4, 63.5 and 66.3% than the PVC composite filled with calcium carbonate. When the dosage of filler was 40 wt%, the elastic modulus of PVC composites filled with BS and its above three modified products decreased by 53.3, 52.3, 50.0 and 46.3%, respectively. Meanwhile, the thermal stability of PVC composites can also be improved at the temperature of over 340 °C. It can be concluded that the enzyme pretreatment can improve the application performance of BS usage in PVC matrix composites.     

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.     

Green Composites of Poly (Lactic Acid) and Sugarcane Bagasse Residues from Bio-refinery Processes

Twin-screw extrusion was used to prepare the composites consisting of PLA and three types of sugarcane bagasse residues (up to 30 wt%) derived from different steps of a biorefinery process. Each residue had different composition, particle size and surface reactivity due to chemical and biological (enzyme, microbes) treatments that the biomass was subjected to. The effects of different residue characteristics on properties, crystallization behaviors and morphologies of PLA composites were investigated. Besides, a small amount (2 wt%) of coupling agent, Desmodur^® VKS 20 (DVKS), was used to improve the interfacial bonding between PLA and bagasse residues. The results indicated that in the presence of 2 % DVKS, PLA composite with pretreated residue exhibited the maximum strength properties (98.94 % tensile strength and 93.91 % flexural strength of neat PLA), while PLA composite with fermentation residue exhibited the minimum strength properties (88.98 % tensile strength and 81.91 % flexural strength of neat PLA).