Valorisation of macroalgae industrial by-product as filler in thermoplastic polymer composites

Poly(lactic acid) composites filled with algae industrial by-product were prepared using melt-mixing process at filler weight fractions of 20, 30 and 40 wt%. Algae by-products were after the extraction of alginate (AW) and mixed with diatomaceous earth (DE). The composition and morphology of both fillers were analysed. Composites’ mechanical properties and thermal degradation were investigated as a function of filler type and content. The addition of DE-filler at 40 wt% resulted in the increase of Young’s modulus by 20% compared to the neat PLA. The presence of small DE particles improved stress distribution and led to stronger composites as compared with AW-filled. Cold crystallization of PLA was induced by small algae particles. Thermal degradation of all composites started at lower temperatures compared with neat PLA. A glow-wire test was carried out to evaluate the effect of inorganic matter on the ignition of the material.     

Thermo-mechanical characterization of Manicaria Saccifera natural fabric reinforced poly-lactic acid composite lamina

The development and thermo-mechanical characterization of a novel green composite lamina, made of PolyLactic Acid (PLA) reinforced with a natural fabric extracted from Manicaria Saccifera palm, are presented. The composite was characterized by thermal-analysis (TGA), tensile, flexural, and izod impact tests, and scanning electronic microscopy (SEM). TGA analysis showed that the degradation process of the composite started earlier than that of neat PLA due to the lower thermal stability of the fabric. The mechanical tests showed that PLA properties were improved. The tensile strength, elastic modulus and impact resistance were improved by 26%, 51% and 56% respectively. Good dispersion and mechanical interlocking of PLA into the fabric were seen by SEM explaining the improvements of the mechanical properties of the composite. In summary, the good tensile properties and the excellent energy absorption capabilities of the MF/PLA composite lamina show great potential of Manicaria fabric as reinforcement in green composites.     

Thermo-mechanical properties enhancement of bio-polyamides (PA10.10 and PA6.10) by using rice husk ash and nanoclay

Composites consisting of fully (PA10.10) and partially (PA6.10) bio-based polyamides and 10–20 wt.% rice husk ash (RHA) was prepared by melt compounding. The mechanical analysis data showed that RHA induced significant improvement in Young’s modulus, a slight reduction in the tensile strength and a large decrease in the deformation at break. Pukanszky’s model was used to evaluate the filler–matrix interactions. The two PAs exhibited similar filler–matrix load transfer with RHA and better performance than polylactic acid (PLA). The addition of modified clay (Cloisite 30B) to the systems with 10 wt.% of RHA gave the best mechanical properties and filler–matrix interactions, notwithstanding the matrix used. Finally, DMT analyses demonstrated that the addition of RHA caused an increase in the heat deflection temperature (HDT) compared to the neat PA matrices. Furthermore, the simultaneous presence of RHA and clay provided the best results.     

Mechanical, thermal and electrical properties of aluminum nitride/polyetherimide composites

The mechanical, thermal and electrical properties of modified AlN/polyetherimide (PEI) composites were investigated. It revealed that the surface of AlN modified by silane could effectively increase the adhesion with matrix, which was beneficial for AlN to reinforce the polyetherimide matrix. After silane modification, the AlN showed good dispersion and wetibility in the polyetherimide matrix and imparted excellent mechanical, electrical and thermal properties. The tensile strength, modulus, electrical and thermal stability were improved with the increasing of AlN content. The tensile strength of AlN/PEI composites increased by 27% when 12.6 vol.% AlN was added to neat polyetherimide. The thermal conductivity of the 57.4 vol.% AlN/PEI composites increased three times compared with neat polyetherimide. Test results indicate that the silane grafted AlN incorporated into the polyetehetimide matrix effectively enhance the thermal stability, thermal conductivity and mechanical properties of the polyetherimide composites.     

Manufacture and characterisation of thermoplastic composites made from PLA/hemp co-wrapped hybrid yarn prepregs

PLA/hemp co-wrapped hybrid yarns were produced by wrapping PLA filaments around a core composed of a 400 twists/m and 25 tex hemp yarn (Cannabis sativa L) and 18 tex PLA filaments. The hemp content varied between 10 and 45 mass%, and the PLA wrapping density around the core was 150 and 250 turns/m. Composites were fabricated by compression moulding of 0/90 bidirectional prepregs, and characterised regarding porosity, mechanical strength and thermal properties by dynamic mechanical thermal analysis (DMTA) and differential scanning calorimetry (DSC). Mechanical tests showed that the tensile and flexural strengths of the composites markedly increased with the fibre content, reaching 59.3 and 124.2 MPa when reinforced with 45 mass% fibre, which is approximately 2 and 3.3 times higher compared to neat PLA. Impact strength of the composites decreased initially up to 10 mass% fibre; while higher fibre loading (up to 45 mass%) caused an increase in impact strength up to 26.3 kJ/m², an improvement of about 2 times higher compared to neat PLA. The composites made from the hybrid yarn with a wrapping density of 250 turns/m showed improvements in mechanical properties, due to the lower porosity. The fractured surfaces were investigated by scanning electron microscopy to study the fibre/matrix interface.     

改性椰纤维增强聚乳酸复合材料力学性能

目的添加适量椰纤维(CF)改善聚乳酸(PLA)的力学性能,以适应产品的包装。方法采用熔融共混法制备不同CF含量的CF/PLA复合材料。通过力学性能测试、扫描电子显微镜观察和动态热力学性能测试,探讨添加不同含量的碱洗CF对复合材料力学性能的影响。结果与纯PLA相比,复合材料的拉伸强度降低,冲击强度增大,储能模量增大,玻璃化转变温度降低。当碱洗CF质量分数为3%时,复合材料的冲击强度比纯PLA增加了24%。结论添加CF有利于提高复合材料的力学性能,碱液浸泡更有利于改善CF和PLA基体的界面相容性。     

PLA/algae composites: Morphology and mechanical properties

Bio-composites with poly(lactic) acid as matrix and various algae (red, brown and green) as filler were prepared via melt mixing. Algae initial size (below 50 μm and between 200 and 400 μm) and concentration (from 2 to 40 wt%) were varied. First, algae morphology, composition and surface properties are analysed for each algae type. Second, an example of algae particle size decrease during processing is given. Finally, tensile properties of composites are analysed. The surface of algae flakes was covered with inorganic salts affecting filler–matrix interactions. The Young’s modulus of composites increased at 40 wt% load of algae as compared with neat PLA although the strain at break and tensile strength decreased. In most cases the influence of algae type was minor. Larger flakes led to better mechanical properties compared to the smaller ones.     

Improvement on the properties of polylactic acid (PLA) using bamboo charcoal particles

Bamboo charcoal (BC) derived from bamboo plants is one kind of well recognized multi-functional materials which has been used in various applications such as medical, cosmetic, food processing and health-related products. In this paper, BC particle is used as reinforcement for polylactic acid (PLA) to enhance its mechanical, thermal and optical properties. The comparison on tensile, flexural and impact properties of BC particle reinforced PLA composites (BC/PLA composites) with the content ranging from 2.5 to 10 wt.% is conducted. Experimental results indicated that the maximum tensile strength, flexural strength and ductility index (DI) of BC/PLA composites increased by 43%, 99% and 52%, respectively as compared with those of neat PLA. This phenomenon was attributed to the uniform distribution of high aspect ratio and surface area of BC particles. Further increasing the BC content to 7.5 wt.% would decrease the glass transition temperature of BC/PLA composites. The mechanical properties of BC/PLA composites were reduced as compared with a neat PLA sample when they were exposed to compost degradation. However, less reduction in these properties was found when they were subject to UV irradiation. UV–Vis spectrometer analysis supported the results of UV irradiation. Fracture surfaces of tensile test samples with and without compost degradation or UV irradiation were analysed by using scanning electron microscopy (SEM). SEM images revealed that there was a good BC particle dispersion in the composites through extrusion and injection moulding processes if the particle content was below 7.5 wt.%.     

Comparison of the thermal,dynamic mechanical and morphological properties of PLA-Lignin & PLA-Tannin particulate green composites

The study of Lignin and Tannin as filler materials in PLA-based polymeric systems has been uncommon in literature. Composites of PLA-Lignin with 5, 10, 15 wt% Lignin and PLA-Tannin with 5, 10, 15 wt% Tannin were fabricated using injection moulding. SEM morphology reveals Lignin forms droplet like dispersions within the PLA matrix in contrast to Tannin. The particle size of Lignin within the matrix is also 10–150 times smaller than Tannin. Isothermal frequency sweeps on the composites show that storage modulus of PLA-Tannin composites starts to degrade at 15 wt% filler concentration and damping rises. PLA-Lignin composites do not show such degradation in storage modulus. The tensile strength of both PLA-Lignin and PLA-Tannin composites falls with increase in filler content. Lignin has a more inhibitory effect on PLA crystallization than Tannin. The onset of thermal degradation of PLA-Lignin and PLA-Tannin composites occurs at slightly lower temperatures than pure PLA.     

Effects of diammonium phosphate on the flammability and mechanical properties of bio-composites

The flammability, thermal stability and mechanical properties of natural fiber-reinforced thermoplastic bio-composites were measured using a horizontal burning test, thermogravimetric analyzer, and universal testing machine, respectively. The composites were fabricated from film resins (Polylactic-acid, PLA and Polypropylene, PP) and natural fibers (coconut filter and jute fiber) by a hot press machine. To improve the flame retardancy of the bio-composites, various diammonium phosphates (DAP) were treated into the fibers. In general, the results indicate that increasing the percentage of DAP used to treat the fibers effectively improves the flame resistant, weight loss rate, and flexural modulus but decreases the flexural and tensile strengths of the bio-composites. Bio-composites with DAP-treated fibers showed a greater flexural modulus than those with untreated fibers, and the flexural modulus was even greater than that of neat polymers (PLA and PP). Also, increasing the percentage of DAP for treatment of the fibers in the composites decreases the temperature required for 5% weight loss and the decomposition rate, but increases the char residual at 500 °C. The best linear burning rate and weight loss rate were observed for fiber treatment with 5% DAP. The compressive and wear properties of these bio-composites were also studied.     

Bio‐Inspired,Self‐Toughening Polymers Enabled by Plasticizer‐Releasing Microcapsules

A new concept for the design of self‐toughening thermoplastic polymers is presented. The approach involves the incorporation of plasticizer‐filled microcapsules (MCs) in an intrinsically rigid and brittle matrix polymer. The intriguing adaptability that this simple tactic enables is demonstrated with composites composed of a poly(lactic acid) (PLA) matrix and 5–20% w/w poly(urea‐formaldehyde) (PUF) MCs that contained hexyl acetate as plasticizer. At low strain (<1.5%), the glassy PLA/MC composites remain rigid, although the intact MCs reduce the Young's modulus and tensile strength by up to 50%. While the neat PLA shows brittle failure at a strain of around 2.5%, the composites yield in this regime, because the MCs rupture and release their plasticizing cargo. This effect leads up to 25‐fold increase of the elongation at break and 20‐fold increase of the toughness vis‐à‐vis the neat PLA, while the impact on modulus and ultimate stress is much smaller. Ballistic impact tests show that the self‐toughening mechanism also works at much higher strain rates than applied in tensile tests and the operating mechanism is corroborated through systematic thermomechanical studies that involved dynamic mechanical testing and thermal analysis.     

Development and Characterization of the Midrib of Coconut Palm Leaf Reinforced Polyester Composite

In this paper, midrib of coconut palm leaves (MCL) was investigated for the purpose of development of natural fiber reinforced polymer matrix composites. A new natural fiber composite as MCL/polyester is developed by the hand lay-up method, and the material and mechanical properties of the fiber, matrix and composite materials were evaluated. The effect of fiber content on the tensile, flexural, impact, compressive strength and heat distortion temperature (HDT) was investigated. It was found that the MCL fiber had the maximum tensile strength, tensile modulus flexural strength, flexural modulus and Izod impact strength of 177.5MPa, 14.85GPa, 316.04MPa and 23.54GPa, 8.23KJ/m² respectively. Reinforcement of MCL enhanced the mechanical properties of pure polyester, including that of tensile strength (by 26%), tensile modulus (by 356%), flexural strength (by 41.81%), flexural modulus (by 169%) and Izod impact strength (by 23 times), but the compressive strength was adversely affected. HDT decreased due to fiber loading, but increased with weight fraction of fiber content. Moreover, the experimental results were compared with theoretical model (Rule of mixture) and other natural fiber /polyester composites.     

Fabrication and characterization of fully biodegradable natural fiber-reinforced poly(lactic acid) composites

Polymer composites were fabricated with poly(lactic acid) (PLA) and cellulosic natural fibers combining the wet-laid fiber sheet forming method with the film stacking composite-making process. The natural fibers studied included hardwood high yield pulp, softwood high yield pulp, and bleached kraft softwood pulp fibers. Composite mechanical and thermal properties were characterized. The incorporation of pulp fibers significantly increased the composite storage moduli and elasticity, promoted the cold crystallization and recrystallization of PLA, and dramatically improved composite tensile moduli and strengths. The highest composite tensile strength achieved was 121 MPa, nearly one fold higher than that of the neat PLA. The overall fiber efficiency factors for composite tensile strengths derived from the micromechanics models were found to be much higher than that of conventional random short fiber-reinforced composites, suggesting the fiber–fiber bond also positively contributed to the composites’ strengths.     

Mechanical and thermal properties of chicken feather fiber/PLA green composites

Chicken feather fiber (CFF)/reinforced poly(lactic acid) (PLA) composites were processed using a twin-screw extruder and an injection molder. The tensile moduli of CFF/PLA composites with different CFF content (2, 5, 8 and 10 wt%) were found to be higher than that of pure PLA, and a maximum value of 4.2 GPa (16%↑) was attained with 5 wt% of CFF without causing any substantial weight increment. The morphology, evaluated by scanning electron microscopy (SEM), indicated that an uniform dispersion of CFF in the PLA matrix existed. The mechanical and thermal properties of pure PLA and CFF/PLA composites were compared using dynamic mechanical analysis (DMA), thermomechanical analysis (TMA) and thermogravimetric analysis (TGA). DMA results revealed that the storage modulus of the composites increased with respect to the pure polymer, whereas the mechanical loss factor (tan δ) decreased. The results of TGA experiments indicated that the addition of CFF enhanced the thermal stability of the composites as compared to pure PLA. The outcome obtained from this study is believed to assist the development of environmentally-friendly composites from biodegradable polymers, especially for converting agricultural waste – chicken feather into useful products.     

MFC-structured biodegradable poly(l-lactide)/poly(butylene adipate-co-terephatalate) blends with improved mechanical and barrier properties

Both polylactide (PLA) and poly(butylene adipate-co-terephthalate) (PBAT) are biodegradable polymers. They are thermoplastics which can be processed using conventional polymer processing methods. In this study, microfibrillar-reinforced composites (MFC) based on PLA/PBAT (PLA/Ecoflex^®) blends in different weight ratios were prepared under industry-relevant conditions by melt extrusion followed by continuous cold drawing of the extrudates. Strip-like specimens (films) and plates (laminates) of the drawn blends were prepared by compression molding (CM) at processing temperature above the melting temperature (T _m) of PBAT, but below T _m of PLA. SEM and WAXS observations show that the extruded blend components are isotropic, but become highly oriented after drawing, and they are converted into MFC-structured polymer–polymer composites after CM. An effect of PLA microfibrils on the non-isothermal crystallization of the Ecoflex during cooling from the melt, associated with the formation of crystalline regions of the matrix around the fibrils, was observed. Depending on the blend composition, the compression-molded samples possess a 3- to 7-time higher tensile strength as well as a 15–30 higher modulus than the neat Ecoflex. In addition, the MFC-structured plates exhibited superior barrier properties compared to the neat Ecoflex, e.g., the oxygen permeability decreased by up to 5 times.     

The effects of Clay on fire performance and thermal mechanical properties of woven glass fibre reinforced polyamide 6 nanocomposites

The effects of small amount of organically modified Clay (Clay) in polyamide 6 (PA6) on fire performance and thermal mechanical properties of Clay/PA6/woven glass fibres (GF) laminates are investigated by cone calorimeter test, dynamic mechanical thermal analysis (DMTA), and heat distort temperature (HDT) measurement. The mechanical properties, such as tensile and flexural properties of Clay/PA6 composites and Clay/PA6/GF laminates were also measured. Up to 3 wt.% Clay in a Clay/PA6/GF laminate with fibre volume fraction of 30 vol.% delayed the ignition time and peak heat release rate (PHRR) time by 55% and 118%, respectively, even though the value of the PHRR or the HDT was not significantly affected. 2 wt.% Clay increased flexural modulus and strength of the Clay/PA6/GF laminate by 10% and 16%, respectively, but more Clay did not increase the mechanical properties accordingly. Small amount of Clay does not affect glass fibre dominated properties, such as HDT, but do affect matrix dominated properties, and significantly affect the fire performance in terms of delaying ignition time and PHRR time. Optimization of laminate making process could benefit from additions of more Clay, therefore further improve fire performance and enhance mechanical properties.     

Mechanisms and impact of fiber–matrix compatibilization techniques on the material characterization of PHBV/oak wood flour engineered biobased composites

Fully biobased composite materials were fabricated using a natural, lignocellulosic filler, namely oak wood flour (OWF), as particle reinforcement in a biosynthesized microbial polyester matrix derived from poly(β-hydroxybutyrate)-co-poly(β-hydroxyvalerate) (PHBV) via an extrusion injection molding process. The mechanisms and effects of processing, filler volume percent (vol%), a silane coupling agent, and a maleic anhydride (MA) grafting technique on polymer and composite morphologies and tensile mechanical properties were investigated and substantiated through calorimetry testing, scanning electron microscopy, and micromechanical modeling of initial composite stiffness. The addition of 46 vol% silane-treated OWF improved the tensile modulus of neat PHBV by 165%. Similarly, the tensile modulus of MA-grafted PHBV increased 170% over that of neat PHBV with a 28 vol% addition of untreated OWF. Incorporation of OWF reduced the overall degree of crystallinity of the matrix phase and induced embrittlement in the composites, which led to reductions in ultimate tensile stress and strain for both treated and untreated specimens. Deviations from the Halpin–Tsai/Tsai–Pagano micromechanical model for composite stiffness in the silane and MA compatibilized specimens are attributed to the inability of the model both to incorporate improved dispersion and wettability due to fiber–matrix modifications and to account for changes in neat PHBV and MA-grafted PHBV polymer morphology induced by the OWF.     

Mechanical and thermal characterization of epoxy composites reinforced with random and quasi-unidirectional untreated Phormium tenax leaf fibers

The present work investigates tensile and flexural behavior of untreated New Zealand flax (Phormium tenax) fiber reinforced epoxy composites. Two series of laminates were produced using the same reinforcement content (20 wt%), arranged either as short fibers or quasi-unidirectional ones. Composites reinforced using quasi-unidirectional fibers showed higher modulus and strength both in tensile and flexural loading, when compared to neat epoxy resin. Short fiber composites, although still superior to epoxy resin both for tensile and flexural moduli, proved inferior in strength, especially as concerns tensile strength. These results have been supported by scanning electron microscopy (SEM), which allowed characterizing fiber–matrix interface, and by acoustic emission (AE) analysis, which enabled investigating failure mechanisms. In addition, thermal behavior of both untreated phormium fibers and composites has been studied by thermogravimetric analysis (TGA), revealing the thermal stability of composites to be higher than for phormium fibers and epoxy matrix alone.     

Enhancement of tensile and thermal properties of epoxy nanocomposites through chemical hybridization of carbon nanotubes and alumina

This paper presents the properties of epoxy nanocomposites, prepared using a synthesized hybrid carbon nanotube–alumina (CNT–Al₂O₃) filler, via chemical vapour deposition and a physically mixed CNT–Al₂O₃ filler, at various filler loadings (i.e., 1–5%). The tensile and thermal properties of both nanocomposites were investigated at different weight percentages of filler loading. The CNT–Al₂O₃ hybrid epoxy composites showed higher tensile and thermal properties than the CNT–Al₂O₃ physically mixed epoxy composites. This increase was associated with the homogenous dispersion of CNT–Al₂O₃ particle filler; as observed under a field emission scanning electron microscope. It was demonstrated that the CNT–Al₂O₃ hybrid epoxy composites are capable of increasing tensile strength by up to 30%, giving a tensile modulus of 39%, thermal conductivity of 20%, and a glass transition temperature value of 25%, when compared to a neat epoxy composite.     

“Green” composites from recycled cellulose and poly(lactic acid): Physico-mechanical and morphological properties evaluation

“Green”/biobased composites were prepared from poly(lactic acid) (PLA) and recycled cellulose fibers (from newsprint) by extrusion followed by injection molding processing. The physico-mechanical and morphological properties of the composites were investigated as a function of varying amounts of cellulose fibers. Compared to the neat resin, the tensile and flexural moduli of the composites were significantly higher. This is due to higher modulus of the reinforcement added to the PLA matrix. Dynamic mechanical analysis (DMA) results also confirmed that the storage modulus of PLA increased on reinforcements with cellulose fibers indicating the stress transfers from the matrix resin to cellulose fiber. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) showed that the presence of cellulose fibers did not significantly affect the crystallinity, or the thermal decomposition of PLA matrix up to 30 wt% cellulose fiber content. Overall it was concluded that recycled cellulose fibers from newsprint could be a potential reinforcement for the high performance biodegradable polymer composites.