Influence of wood species and particle size on mechanical and thermal properties of wood polypropylene composites

This study aims to investigate the effects of two types of wood flour; oil palm mesocarp flour (OMF) and rubberwood flour (RWF), and their particle sizes on mechanical, physical, and thermal properties of wood flour reinforced recycled polypropylene (rPP) composites. The composite materials were manufactured into panels by using a twin-screw extruder. The rPP composites based on RWF significantly showed higher flexural, tensile, and compressive properties (both strength and modulus) as well as hardness and thermal stability than those composites based on OMF for the same particle sizes. However, distribution of RWF in the rPP matrix was less homogeneous than that of the rPP/OMF composites. Furthermore, a decrease of the particle sizes of filler for the rPP/OMF or RWF composites increased the flexural, tensile, compressive, and hardness properties. Likewise, the thermal stability of both OMF and RWF composites were insignificantly affected by the particle sizes.     

Flame retarding PC/ABS resins having superior thermomechanical properties

Triphenyl phosphate (TPP) is well known to be one of the most effective flame retardants for acrylonitrile-butadiene-styrene copolymer (ABS) and its blending resins, such as polycarbonate (PC)/ABS, among various phosphorous-based compounds. However, TPP can also play a role as a plasticizer, which decreases the mechanical properties of PC/ABS resins at high temperature. Furthermore considerable amount of TPP has to be evaporated during molding process due on its much lower evaporation temperature. To overcome these shortcomings, we tried to immobilize TPP by grafting on butadiene moiety of ABS. FT-IR analysis of prepared TPP-grafted ABS (ABS-g-TPP) comparing with TPP, ABS and their blend confirmed that chemical reactions happened between TPP and ABS resins and it was attributed to the graft reaction of TPP onto butadiene moieties. Prepared ABS-g-TPP resins were blended with PC at various compositions to be prepared as testing specimens by injection molding. The physical characteristics such as mechanical properties, thermal stability, and flame retarding properties of the PC/ABS-TPP graft copolymer were analyzed through Vicat softening temperature, IZOD impact strength, transmission electron microscope, and UL94 flame retardation tests. Results showed that PC/ABS-g-TPP resin takes better thermomechanical properties than the existing PC/ABS resins at relatively low additional TPP amounts.     

Preparation and Properties of Poly(lactic Acid)/PLA-<Emphasis Type="Italic">g</Emphasis>-ABS Blends

PLA/PLA-g-ABS blends were prepared and evaluated for mechanical properties performance. Firstly, carboxylic acid functionalized ABS particles were synthesized by grafting polymethacrylic acid (PMAA) onto ABS particle surface using potassium persulfate as an initiator. The reaction was followed by FTIR analysis. The resultant carboxylated ABS was melt mixed with virgin PLA in an internal mixer to obtain PLA/PLA-g-ABS blends. The obtained PLA/PLA-g-ABS blends were subject to injection molding to obtain specimens for testing evaluation. It was found that impact resistance values significantly outperformed neat PLA by 60 %, 87 %, and 150 % for PLA/PLA-g-ABS 10 wt%, PLA/PLA-g-ABS 20 wt%, and PLA/PLA-g-ABS 30 wt%, respectively. A significant increase in impact strength was contributable to ABS rubber which exhibited even dispersion and good interfacial adhesion. The impact strength was dependent on the percent loading of PLAg-ABS; the more the PLA/PLA-g-ABS the higher the impact strength value. In a similar manner, tensile strength increases when loaded with PLA/PLA-g-ABS albeit at lesser effect. Considering the percent elongation, a massive increase in percent elongation was recorded in case of PLA/PLA-g-ABS 20 wt% and PLA/PLA-g-ABS 30 wt%, implying that these blends were extremely flexible and tough when compared to neat PLA, control, and PLA/PLA-g-ABS 10 wt%.     

Green composites. II. Environment-friendly, biodegradable composites using ramie fibers and soy protein concentrate (SPC) resin

Fully biodegradable and environment-friendly green composite specimens were made using ramie fibers and soy protein concentrate (SPC) resin. SPC was used as continuous phase resin in green composites. The SPC resin was plasticized with glycerin. Precuring and curing processes for the resin were optimized to obtain required mechanical properties. Unidirectional green composites were prepared by combining 65 % (on weight basis) ramie fibers and SPC resin. The tensile strength and Young’s modulus of these composites were significantly higher compared to those of pure SPC resin. Tensile and flexural properties of the composite in the longitudinal direction were moderate and found to be significantly higher than those of three common wood varieties. In the transverse direction, however, their properties were comparable with those of wood specimens. Scanning electron microscope (SEM) micrographs of the tensile fracture surfaces of the green composite indicated good interfacial bonding between ramie fibers and SPC resin. Theoretical values for tensile strength and Young’s modulus, calculated using simple rule of mixture were higher than the experimentally obtained values. The main reasons for this discrepancy are loss of fiber alignment, voids and fiber compression due to resin shrinking during curing.     

Basic properties of grain by-products and their viability in polypropylene composites

The objective was to study the potential of grain by-products (husk) of grains such as wheat (Triticum aestivum L; German name is Weizen) and rice (Oryza sativa) as reinforcements for thermoplastics as an alternative to or in combination with wood fibres. Prior to composites preparation, the chemical components of fibres such as cellulose, hemi-cellulose, lignin, starch, protein and fat were measured and the surface chemistry and functionality of grain by-products were studied using EDX and FT-IR. Structural constituents (cellulose, starch) were found in wheat husk (W) equal 42%, in rice husk 50% and in soft wood 42%, respectively. Thermal degradation characteristics, the bulk density, water absorption and the solubility index were also investigated. Wheat husk (W) and rice husk were found thermally stable at temperatures as low as 178 °C and 208 °C, respectively. The particle morphology and particle size were investigated using microscopy. Water absorption properties of the fibres were studied to evaluate the viability of these fibres as reinforcements. Polypropylene composites were fabricated using a high speed mixer and an ensuing injection moulding process with 40 wt% fibre. The tensile and Charpy impact strength of the resulting composites were investigated. The tensile elongation at break was found to 75% for wheat husk (W) composites and 23% for rice husk composites better than soft wood composites. Rice husk composites showed 13% better Charpy impact strength than soft wood composites. Due to coupling agent, tensile strength of composites found to improve 25% for soft wood, 35% for wheat husk (W) and 45% for rice husk.     

Effect of coir fiber content and compatibilizer on the properties of unidirectional coir fiber/polypropylene composites

The main objective of this research was to study the effect of fiber content variation and stearic acid (SA) treatment on the fundamental properties of unidirectional coir fiber (CF) reinforced polypropylene (PP) composites. Several percentages of filler contents were used (10–40 wt %) in order to gain insights into the effect of filler content on the properties of the composites. Coir/PP composites were fabricated by compression molding, and the properties of composites were studied by physico-mechanical and thermal properties. The results from mechanical properties such as tensile strength (TS), tensile modulus (TM) and impact strength (IS) of the CF/PP composites were found to be increased with increasing fiber content, reached an optimum and thereafter decreased with further increase in fiber content. Treatment of the coir with SA as the coupling agent enhanced the mechanical properties, crystallization temperature and crystallinity of virgin PP and water desorption of the resulting composites, resulting from the improved adhesion between the CF and PP matrix. Scanning electron micrographs (SEM) of the tensile fractured samples showed improved adhesion between fiber and matrix upon treatment with SA. Interfacial shear strength (IFSS) of the composites was measured by single fiber fragmentation test (SFFT).     

Effect of nanoclay and magnesium hydroxide on some properties of HDPE/wheat straw composites

Since natural fiber/polymer composites are increasingly used, the development of safe and environmental friendly flame retarding bio-based composites is of great importance. But this issue must maintain the mechanical performance of these composites. To study these objectives, four levels of magnesium hydroxide Mg(OH)₂ of (0, 10, 20, 30 phc) and two levels of nanoclay (0, 3 phc) were considered and incorporated into HDPE/wheat straw composites. Maleic anhydride grafted polyethylene (PE-g-MA) was also used as a compatibilizer at constant content. The samples were prepared by melt compounding and injection molding processes, respectively. The some properties of samples including burning rate and mechanical properties (tensile and impact strengths) were tested based on the ASTM standard. The results showed that the burning rate of samples decreased with increasing the nanoclay and Mg(OH)₂ content. The tensile and impact strengths showed a marginal reduction by adding Mg(OH)₂ from 10 phc to 30 phc and the tensile modulus and impact strength revealed an increase by increasing the amount of nanoclay up to 3 phc. Generally, these results confirmed that the fire retarding and mechanical properties of HDPE/wheat straw composites could be significantly improved with an appropriate combination of the nanoclay and Mg(OH)₂ in the composites.     

Compatibilizing effects of polypropylene-g-itaconic acid on the polypropylene composites

We prepared long carbon fiber (LCF)-reinforced thermoplastic composites using a compatibilizer of itaconic acid grafted polypropylene (PP-g-IA). We confirmed the structure of PP-g-IA and investigated the compatibilizing effects of PPg- IA on LCF/polypropylene composites. The tensile strength, tensile moduli, flexural strength, and flexural moduli of the composites increased with increasing PP-g-IA content in the thermoplastic composites. Using single pull-out analyzing system, we found PP-g-IA improved interfacial strength between the carbon fiber and PP matrix. The thermal properties of the composites were measured by thermogravimetric analysis (TGA). We could observe that LCF enhanced the mechanical properties and thermal decomposition temperature of the polypropylene (PP) composites, compared with neat PP. The fractured surfaces of PP/PP-g-IA/LCF composites showed that PP-g-IA was effective for improving the interfacial adhesion between LCF and PP matrix.     

Structure and performance of fibers prepared from liquefied wood in phenol

The fibers from liquefied wood in phenol (WPFs) were spun by adding hexamethylenetetramine as synthetics and cured by soaking in solution containing hydrochloric acid and formaldehyde as main components. The chemical structure of WPFs remarkably changed from that of liquefied wood was identified by FT-IR spectrometer. WPFs with the average diameter of 27∼42 μm, tensile strength of 230∼356 MPa, and modulus of 15∼31 GPa were obtained using spinning speed of 0.72 μm min⁻¹, hydrochloric acid concentration of 18.5 %, heating rate of 10 °C h⁻¹, and curing time of 4 h. These WPFs showed a high thermal stability and a complex thermal decomposition process by TG(thermogravimetric) analysis. It was also found that the two obvious weight loss temperatures of WPFs were 510°C and 748°C.     

Green composites. I. physical properties of ramie fibers for environment-friendly green composites

The surface topography, tensile properties, and thermal properties of ramie fibers were investigated as reinforcement for fully biodegradable and environmental-friendly ‘green’ composites. SEM micrographs of a longitudinal and cross-sectional view of a single ramie fiber showed a fibrillar structure and rough surface with irregular cross-section, which is considered to provide good interfacial adhesion with polymer resin in composites. An average tensile strength, Young’s modulus, and fracture strain of ramie fibers were measured to be 627 MPa, 31.8 GPa, and 2.7 %, respectively. The specific tensile properties of the ramie fiber calculated per unit density were found to be comparable to those of E-glass fibers. Ramie fibers exhibited good thermal stability after aging up to 160°C with no decrease in tensile strength or Young’s modulus. However, at temperatures higher than 160°C the tensile strength decreased significantly and its fracture behavior was also affected. The moisture content of the ramie fiber was 9.9%. These properties make ramie fibers suitable as reinforcement for ‘green’ composites. Also, the green composites can be fabricated at temperatures up to 160°C without reducing the fiber properties.     

Effect of PTMEG on the mechanical and flame retardance behaviour of novolac phenolic based CFRP

The objective of this work was to study the effect of addition of Poly tetramethylene ether glycol (PTMEG) on the mechanical and flame retardance behaviour of novolac phenolic/carbon fiber composites (NPCC). The miscibility of PTMEG and novolac phenolic resin was studied using DSC. Both modified and unmodified novolac phenolic resins were characterised for chemical structure using FTIR. The 8 wt% PTMEG/NPCC yielded 39 % increase in impact strength compared to that of unmodified NPCC. Void content of the composites were measured. Both NPCC and PTMEG blended NPCC were tested for tensile strength (UTS), flexural strength (FS), inter laminar shear strength (ILSS) and impact strength. Also morphological studies were carried out using SEM. The UTS, FS, ILSS and impact strength of the modified NPCC showed better results at 8 wt% of PTMEG without any compromise on the flame retardancy. The fracture surface examination showed good adhesion between the fiber and the matrix in the modified NPCC.     

Properties of medium-density particleboard from saline Athel wood

The Athel tree, Tamarix aphylla (L), can potentially be used as a biomass crop to help manage saline subsurface drainage water in arid land irrigated agriculture. In this study, Athel wood was used to manufacture medium-density particleboard with an aim of developing new applications for the saline wood. The research investigated the effects of different types of adhesives, particle sizes, bark content (BC), resin content (RC), and hot water pretreatment on the mechanical and water resistance properties of the Athel-derived, medium-density particleboards. The measured mechanical properties included tensile strength (TS), modulus of rupture (MOR), modulus of elasticity (MOE), and internal bond strength (IB) of the finished particleboards. Water absorption and thickness swell were used to evaluate the water resistance. Polymeric methane diphenyl diisocyanate (PMDI) resin made particleboard of better mechanical properties and water resistance than urea formaldehyde (UF). The medium size (20–40 mesh) particles gave the best mechanical properties and water resistance than of the particleboard when evaluated against the smaller size (40–60 mesh) and larger size (10–20 mesh) particles. The mechanical properties of particleboard were improved as the resin content of the UF-board increased from 7 to 16%, but deteriorated as the bark content increased from 0 to 16.2%. The particleboard made from the wood particles that had undergone hot water pretreatment had poor mechanical properties and water resistance compared with the particleboard made from the untreated particles. Saline Athel wood is an appropriate material for manufacturing particleboards.     

Warpage and mechanical properties of film insert molded parts with composite substrate

Mechanical properties of chopped carbon fiber (CF) reinforced PC/ABS composites were investigated. Tensile strength and elastic modulus of the composites were enhanced with increasing CF contents. On the contrary, impact strength of the composite was decreased with increasing CF fraction. Film insert molding was introduced in order to improve impact strength. Film insert molded composite specimens have higher impact strength than conventional injection molded composite specimens because inserted film acted as a cushion to absorb the impact energy. Large warpage which was observed after molding and known as a disadvantage of the film insert molded part can be prevented by controlling the amount of filled CFs. Therefore, fiber reinforcement and film insert molding can be applied simultaneously to reduce warpage of the film insert molded part and enhance impact strength of the CF reinforced composite.     

The simultaneous introduction of low and high molecular weight of biodegradable Poly(diethylene glycol adipate)s to Plasticize and Toughen Polylactide

Plasticization and toughness of polylactide (PLA) are of interesting due to its poor machinability and brittleness. Here, low and high macromolecular weight of Poly(diethylene glycol adipate)s (L-PDEGA and H-PDEGA) were used to plasticize and toughen PLA simultaneously. The results showed that the mechanical properties of PLA remained almost unchanged when only 5 wt% L-PDEGA was added. However, H-PDEGA were effective in lowering the glass transition temperatures as well as in increasing the elongation at break and the impact strength. Compared with neat PLA, the crystallinity of PLA increased with increasing H-PDEGA content. When 20 wt% H-PDEGA was added, the impact strength and the elongation at break increased from 3.1 kJ/m² and 5.6 % of neat PLA to 68.3 kJ/m² to 272.4 %, respectively. Additionally, morphological study revealed that the fracture behavior of PLA had been changed from brittle to ductile after H-PDEGA incorporated. The results of rheological analysis showed that the storage modulus and complex viscosity in the melt state of the blends were decreased compared with that of neat PLA.     

Mechanical behavior of composites reinforced with fibers caroa

Composites were prepared with 13, 23 30 and 40 % fiber and evaluated the mechanical performance in tensile, flexural and impact. The mechanical properties of these composites were also evaluated function of time at 110 °C thermal exposure. Caroa fibers were characterized by techniques such as thermal gravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was found that the best mechanical properties were achieved for composites containing 23 to 30 % fiber. The incorporation of 23 % fiber caroa increased both the modulus of elasticity in the tensile test as the flexural strength and impact, the composite with 30 % fiber caroa showed higher tensile strength. The results show that the tensile and flexural strength of the composite decreased with time of thermal exposure. The thermal aging at 110 °C caused a decrease in tensile properties of the composites.     

Mechanical anisotropy in unidirectional glass fabric reinforced oligomeric siloxane modified polyester composites

In this study, the effect of incorporation of oligomeric siloxane into unsaturated polyester on mechanical behavior of unidirectional glass fiber/polyester composites has been investigated by means of tensile, flexural and short beam shear tests. The amount of oligomeric siloxane added into unsaturated polyester was in the range 1?C3 % by weight of the glass fabrics. Mechanical tests were conducted at different angles (0 °, 45 °, and 90 °) with respect to fiber direction. The higher siloxane content exhibited a tendency to have greater tensile, flexural and interlaminar shear strength values in machine direction, bias direction and cross direction. From Scanning electron microscopy images, the presence of polyester particles on the unidirectional glass fiber surface confirmed better adhesion.     

Hybrid effect in the mechanical properties of jute/rockwool hybrid fibres reinforced phenol formaldehyde composites

This research work was concerned with the evaluation of the effect of fibre content on the mechanical properties of composites. Composites were fabricated using jute/phenol formaldehyde (PF), rockwool/PF, and jute/rockwool hybrid PF with varying fibre loadings. Jute and rockwool fibre reinforced PF composites were fabricated with varying fibre loadings (16, 25, 34, 42, 50, and 60 vol.%). The jute/rockwool hybrid PF composites were manufactured at various ratios of jute/rockwool fibres such as 1:0, 0.92:0.08, 0.82:0.18, 0.70:0.30, 0.54:0.46, 0.28:0.72, and 0:1. Total fibre content of the hybrid composites was 42 vol.%. The results showed that tensile strength of the composite increased with increasing fibre content up to 42 vol.% over which it decreased for jute and rockwool fibre reinforced PF composites. Flexural strength of the composite was noted to peak at a fibre loading of 42 vol.% for jute/PF composites, and 34 vol.% for rockwool/PF composites. Impact strength of jute/PF composites increased with increasing fibre loading but that of rockwool/PF composites decreased at higher (>34 vol.%) fibre loadings. Tensile, flexural, and impact strengths of jute/PF composites were found to be higher than those of rockwool/PF composites. The maximum hardness values were obtained 42 vol.% for jute/PF composite, and 34 vol.% for rockwool/PF composite. Further increase in fibre loading adversely affected the hardness of both composites. For jute/rockwool hybrid PF composites, tensile and impact strengths decreased with increasing rockwool fibre loading. The maximum flexural strength of jute/rockwool hybrid PF composites was obtained at a 0.82:0.18 jute/rockwool fibre ratio while maximum hardness was observed at a 0.28:0.72 jute/rockwool fibre ratio. The fractured surfaces of the composites were analysed using scanning electron microscope in order to have an insight into the failure mechanism and fibre/matrix interface adhesion.     

Thermo-mechanical and morphological properties of short natural fiber reinforced poly (lactic acid) biocomposite: Effect of fiber treatment

Untreated oil palm empty fruit bunch (REFB), alkali treated EFB (AEFB), ultrasound treated EFB (UEFB) and simultaneous ultrasound-alkali treated EFB (UAEFB) short fibers were incorporated in poly(lactic acid) (PLA) for fabricating bio-composites. The REFB fiber-PLA (REPC) and treated EFB (TEFB) fiber-PLA (TEPC) composites were prepared and characterized. Glass transition temperature, crystal melting temperature, decomposition temperature, melt flow index, density and mechanical properties (tensile strength, tensile modulus and impact strength) of TEPC are found to be higher than those of REPC. The observed crystallization temperature of TEPC is lower than that of REPC. Among all samples, TEPC prepared from UAEFB fiber shows better performances than other samples fabricated by REFB and AEFB fibers. Scanning electron microscopy, Fourier transform infrared spectroscopy and XRD analyses well support all the observed results.     

Influence of natural clinoptilolite nanoparticles on thermal stability,scratch resistance and adherence properties of Acrylonitrile butadiene styrene (ABS)

In order to improve thermal stability of Acrylonitrile-butadiene-styrene (ABS) polymer, ABS/natural clinoptilolite (Clino) nanocomposite was produced using solvent/non-solvent method. The influence of natural clinoptilolite nanoparticles on scratch resistance and adherence properties of ABS coating on steel coupons was investigated. In order to study the scratch resistance and adherence properties, thin (20 µm) coatings of ABS and ABS/Clino nanocomposites, were prepared by solution casting method. The formation of ABS/Clino nanocomposite was characterized using FTIR spectroscopy, X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM). Results showed that there is a strong interaction such as hydrogen bonding between ABS and clinoptilolite nanoparticles. The thermal stability of the nanocomposite was examined using thermogravimetric analysis (TGA). TGA results showed an increase in the thermal degradation temperature of the nanocomposite. TGA results indicated that the thermal stability of ABS increases by increasing the Clino content of nanocomposite up to 5 % w/w. Scratch resistance and adherence properties of ABS/Clino nanocomposite coatings were also evaluated. Results showed that the scratch resistance and adherence strength of ABS/Clino nanocomposite coatings are higher than that of pure ABS coatings.     

Enhancement of the mechanical properties of glass/polyester composites via matrix modification glass/polyester composite siloxane matrix modification

Enhancement of the mechanical and vibrational properties of glass/polyester composites was aimed via matrix modification technique. To achieve this, unsaturated polyester was modified by incorporation of oligomeric siloxane in the concentration range of 1–3 wt%. Modified matrix composites reinforced with woven roving glass fabric were compared with untreated glass/polyester in terms of mechanical and interlaminar properties by conducting tensile, flexure, and short-beam shear tests. It was found that after incorporation of 3 % oligomeric siloxane into the polyester matrix, the tensile, flexural, and interlaminar shear strength (ILSS) values of the resulting composite increased by 16, 15, and 75 %, respectively. The increases in ILSS as well as in tensile and flexural properties were considered to be an indication of better fiber/matrix interaction as confirmed by SEM fractography images. Furthermore, the effect of oligomeric siloxane incorporation on the vibrational properties of the composites was investigated by experimental modal testing and the natural frequencies of the composites were found to increase with increasing siloxane concentration.