Facile fabrication of HDPE-g-MA/nanodiamond nanocomposites via one-step reactive blending

In this letter, nanocomposites based on maleic anhydride grafted high density polyethylene (HDPE-g-MA) and amine-functionalized nanodiamond (ND) were fabricated via one-step reactive melt-blending, generating a homogeneous dispersion of ND, as evidenced by transmission electron microscope observations. Thermal analysis results suggest that addition of ND does not affect significantly thermal stability of polymer matrix in nitrogen. However, it was interestingly found that incorporating pure ND decreases the thermal oxidation degradation stability temperature, but blending amino-functionalized ND via reactive processing significantly enhances it of HDPE in air condition. Most importantly, cone tests revealed that both ND additives and reactive blending greatly reduce the heat release rate of HDPE. The results suggest that ND has a potential application as flame retardant alternative for polymers. Tensile results show that adding ND considerably enhances Young's modulus, and reactive blending leads to further improvement in Young's modulus while hardly reducing the elongation at break of HDPE

Nonisothermal crystallization behavior of polypropylene-C60 nanocomposites

The nonisothermal crystallization behavior of polypropylene (PP) and PP-fullerene (C60) nanocomposites was studied by differential scanning calorimetry (DSC). The kinetic models based on the Jeziorny, Ozawa, and Mo methods were used to analyze the nonisothermal crystallization process. The onset crystallization temperature (Tc), half-time for the crystallization (t1/2), kinetic parameter (F(T)) by the Mo method and activation energy (ΔE) estimated by the Kissinger method showed that C60 accelerates the crystallization of PP, implying a nucleating role of C60. Furthermore, due to the reduced viscosity of PP by adding 5% C60, the parameters of crystallization kinetics for the PP-5%C60 nanocomposites changed remarkably relative to that of neat PP and when lower contents of C60 were added to PP

Morphological structure and mechanical properties of epoxy/ polysulfone/cellulose nanofiber ternary nanocomposites

Despite some work on epoxy resin/cellulose nanofiber (CNF) system, it remains unclear how CNF affects microstructure and mechanical properties of epoxy/polysulfone (PSF) binary blends so far. We herein introduced CNF into the blends via a combination of solvent exchange and melt mixing. Results show that epoxy/PSF binary blends display three distinct types of phase separated structures but slightly affecting mechanical properties because of poor interfacial adhesion. However, only adding small amount of CNF can enhance impact toughness and tensile strength due to improved interfacial adhesion, probably arising from hydrogen bonding interactions between CNF surfaces and matrix polymers, and penetrating and bridging effects of CNF between different phases. For example, compared with the epoxy/PSF blends, adding 0.2 wt% of CNF can increase impact strength by ∼49%. Additionally, 0.3 wt% of CNF can increase the glass transition temperature by ∼18 °C relative to the epoxy resin

Layered cellulose nanofibers nanocomposites via layer by layer assembling

Native cellulose nanofibers with high strength ratio may create an alternative as the blade material for wind power field. In this work, cellulose nanofibers (CN) with high L/D ratio was fabricated by combined biological treatment and mechanical disintegration processes. Then, we created a high-performance cellulose layered nanocomposites via layer by layer (LBL) assembling strategy. Transmission electron microscopy (TEM) observations show that common paper pulp exhibits a nearly spherical or amorphous structure, while as-made cellulose nanofibers displays a high aspect ratio, with a length of ca. 10~100 μm and a diameter of ca. 30~100 nm. However, some relative big fibres bundles are still observed. Mechanical measurements demonstrate that the tensile strength, Young's modulus and elongation at break of layered CN nanocomposites (CNLC) reach 114MPa. 7.0GPa and 68%,respectively, while only 63MPa, 3.3 GPa and 27% for layered common paper pulp composites (PFLC). Flexural tests results show that CNLC gives a flexural strength and modulus of 263 MPa and 19 GPa, while only 114 MPa and 11 GPa for PFLC. Fracture surface observations indicate that though layered structure can be observed for both PFLC and CNLC, much thinner layer and long fibrous structure only exist in CNLC, which results in high mechanical performance

Morphology, healing and mechanical performance of nanofibrillated cellulose reinforced poly(ε-caprolactone)/epoxy composites

In this study, nanofibrillated cellulose (NFC) reinforced poly(ε-caprolactone) (PCL)/epoxy composites were fabricated by a combination method of solvent exchange and melt mixing. Effects of NFC incorporation on morphology, healing capability and mechanical properties of PCL/epoxy systems were investigated. Domain size of the separated phases was reduced and the continuity of PCL-rich phase was increased with NFC addition. Both healing efficiency and mechanical properties were improved due to the uniform distribution and bridging effect of NFC within the polymer matrix. Upon the addition of merely 0.2 wt% of NFC, the healing efficiency was increased by about 26% and simultaneously tensile strength, elongating at break and impact strength were improved by about 27%, 38% and 38%, respectively. Additionally, glass transition temperature of the epoxy phase in the composite was increased by about 12.8 °C

A nano-TiO2/regenerated cellulose biohybrid enabled simultaneous improvements in strength and toughness for solid epoxy resins

The intrinsic brittleness has significantly restricted practical applications of epoxy resins. Existing toughening strategies often lead to degraded mechanical strength. Hence, it has been attractive but a huge challenge to design high-performance sustainable additives that can simultaneously improve strength and toughness of epoxy resins. Here, we report the synthesis of a nano-TiO2/regenerate cellulose (RC) biohybrid via a facile microwave method for strengthening and toughening a soft epoxy resin system (modulus below 1 GPa). Our results show that with 10 phr nano-TiO2/RC, the resultant epoxy composite exhibits simultaneous enhancements in tensile strength and impact toughness, ca. 38% and 40% higher than corresponding values of virgin epoxy resin because of improved interfacial compatibility. Moreover, the addition of as-designed nano-TiO2/RC can enhance thermostability of epoxy resin. It has a slightly negative effect on the curing reaction but does not change the curing mechanism of epoxy resins. This study provides a facile, efficient and green method for preparing bifunctional additive for creating strong and tough epoxy composites, which are expected to find wider applications in industries

Converting industrial alkali lignin to biobased functional additives for improving fire behavior and smoke suppression of polybutylene succinate

The inherent flammability of biodegradable polybutylene succinate (PBS) extremely restricts the growing applications as packaging and construction materials; meanwhile, only a minority of industrial alkali lignin has been effectively utilized until now. To address these two challenges, herein we have converted alkali lignin into one biobased additive for PBS by chemically modified lignin with phosphorus, nitrogen, and the zinc(II) ions. Cone calorimetry results show that addition of 10 wt % modified lignin (PNZn-lignin) reduces the peak heat release rate and total heat release of PBS strikingly by 50 and 67%, respectively. Moreover, the total smoke production is decreased noticeably by 50%. Observations of char residues indicate that adding PNZn-lignin leads to a compact, intact, and thick char layer that is responsible for such enhanced properties. This work offers a new strategy for reducing the flammability and smoke release of PBS, promoting high-value-added utilization of industrial lignin, and designing biobased advanced polymeric materials

Fabrication of exfoliated graphene-based polypropylene nanocomposites with enhanced mechanical and thermal properties

Abstract: Despite the great potential of graphene as the nanofiller, to achieve homogeneous dispersion remains the key challenge for effectively reinforcing the polymer. Here, we report an eco-friendly strategy for fabricating the polymer nanocomposites with well-dispersed graphene sheets in the polymer matrix via first coating graphene using polypropylene (PP) latex and then melt-blending the coated graphene with PP matrix. A ∼75% increase in yield strength and a ∼74% increase in the Young's modulus of PP are achieved by addition of only 0.42 vol% of graphene due to the effective external load transfer. The glass transition temperature of PP is enhanced by ∼2.5 °C by incorporating only 0.041 vol% graphene. The thermal oxidative stability of PP is also remarkably improved with the addition of graphene, for example, compared with neat PP, the initial degradation temperature is enhanced by 26 °C at only 0.42 vol% of graphene loading

Compatibilization of polypropylene/corn starch plasticized with diethanol amine

In the presented paper, diethanol amine is employed to plasticize corn starch, and plasticized starch is incorporated into polypropylene to create semibio-based composites with the aid of compatibilizer, maleic anhydride-grafted PP (PPMA). Compared with PP/starch blend, the presence of diethanol amine changes the morphology and increases the plasticity of starch due to the reduction effect of intermolecular hydrogen bonding interactions. Adding PPMA could reduce the dispersed size of starch granules in the polymer matrix due to in situ reactive compatibilization. Addition of 30 wt% PPMA decreases the starch granules size from ~10 μm to ~5 μm, and increases the tensile strength from 16 MPa for PP/plasticized starch to 30 MPa, increased by 87.5%. Thus, as-created bio-composites with improved mechanical properties will find many potential applications such as packaging

Thermal degradation and flame retardancy properties of ABS/lignin: effects of lignin content and reactive compatibilization

Effects of alkali lignin incorporation and in situ reactive compatibilization on the thermal stability and flame retardancy of ABS were investigated. Morphology observations show that lignin can form submicron dispersed phases in ABS matrix regardless of compatibilization. Thermal analyses show that lignin will cause a slight thermal instability of ABS due to its relatively lower thermal stability, and compatibilization reaction has little effluence on that. However, lignin can slow the degradation process and increase the char residue of ABS with increasing lignin loading, and the compatibilization does not markedly affect them. Cone calorimeter tests demonstrate that lignin can significantly reduce the heat release rate, and slow the combustion process of ABS, e.g., 20 wt% lignin causing a 32% reduction in peak heat release rate (PHRR). The compatibilization can further reduce the flammability of ABS due to the improved char layer. The char residue analyses indicate that the formation of protective char layer of lignin is primarily responsible for the enhanced flame retardancy