Preparation of high thermal conductive aluminum nitride/cyanate ester nanocomposite using a new macromolecular coupling agent

Novel glycidyl methacrylate–butyl acrylate–maleic anhydride (GBM) terpolymers with different molecular weights were synthesized by radical polymerization and characterized using fourier transform infrared, nuclear magnetic resonance (¹H‐NMR and ¹³ C‐NMR), and gel permeation chromatography. Each GBM terpolymer was used to modify aluminum nitride (AlN), and the modified AlN, coded as AlN(GBM), was added to 2,2′‐bis(4‐cyanatophenyl)isopropylidene (CE) resin for preparing composites. Composites based on original AlN or γ‐(2,3‐epoxypropoxy)propyltrimethoxysilane‐modified AlN (AlN(K)) were also prepared for comparison. Although GBM and γ‐(2,3‐epoxypropoxy)propyltrimethoxysilane have similar reactive groups, the results indicate that GBM shows more attractive integrated advantages, reflected by the fact that CE/AlN(GBM) composites have better thermal stability, higher thermal conductivity, and higher glass transition temperature than those of CE/AlN(K). These properties result from better dispersion of fillers, improved interfacial adhesion between fillers and CE resin, and increased cross‐linking density. This study demonstrates that the nature of the coupling agents is an important factor to develop high performance composites for cutting‐edge industries. Copyright © 2011 John Wiley & Sons, Ltd.     

Morphology and properties of cyanate ester/liquid polyurethane/silica nanocomposites

The high‐speed homogeneous shearing method was applied to prepare nanocomposites of cyanate ester (CE) with liquid polyurethane elastomer (PUR) and silica. To investigate the influence of various components on the morphology and properties of the ternary composites, the binary composites of CE/PUR and CE/silica were also involved in this article. The morphology of the cured materials of binary and ternary systems was investigated by transmission electron microscopy (TEM), and the results show that silica nanoparticles were uniformly distributed in the ternary and binary matrix. Phase separation of elastomer in composites was not observed by TEM. FTIR test and dynamic mechanical analysis (DMA) proved that chemical linking was existent between PUR and CE. Scanning electron microscopy examinations and mechanical properties tests were carried out. The results show that ternary composites displayed higher fracture toughness and impact strength compared with most of the binary systems. This suggests that the addition of PUR and nanosilica can synergistically improve the toughness of CE. DMA studies confirmed that the incorporation of silica can increase the storage modulus and T_g for CE and CE/PUR system, since there are a good adhesion and a strong hydrogen bonding between silica and polymers. The thermal property of ternary composites increases with the increase of silica nanoparticle loading. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1243–1251, 2008     

Statistical Design of Biocarbon Reinforced Sustainable Composites from Blends of Polyphthalamide (PPA) and Polyamide 4,10 (PA410)

A full factorial design with four factors (the ratio of polyphthalamide (PPA) and polyamide 4,10 (PA410) in the polymer matrix, content percent of biocarbon (BioC), the temperature at which it was pyrolyzed and the presence of a chain extender (CE)), each factor with two levels (high and low), was carried out to optimize the mechanical properties of the resulting composites. After applying a linear model, changes in tensile strength, elongation at break and impact energy were not statistically significant within the considered material space, while the ones in the flexural modulus, the tensile modulus, density and heat deflection temperature (HDT) were. The two most influential factors were the content of BioC and its pyrolysis temperature, followed by the content of PPA. The affinity of PPA with a high-temperature biocarbon and the affinity of PA410 with a lower-temperature biocarbon, appear to explain the mechanical properties of the resulting composites. The study also revealed that the addition of CE hindered the mechanical properties. By maximizing the flexural modulus, tensile modulus and HDT, while minimizing the density, the optimal composite predicted is an 80 [PPA:PA410 (25:75)] wt% polymer composite, with 20 wt% of a BioC, pyrolyzed at a calculated 823 °C.     

Glass-fibre reinforced composite materials based on unsaturated polyester resins

The effect of glass-fibre content on the thermal and mechanical properties of cross-linked composites based on unsaturated polyester resins have been investigated by thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical thermal analysis and by measuring the heat distortion temperature (HDT). Two different matrix resins and two different glass mats were used, and the glass-fibre contents varied. Altogether 12 composite systems were tested. The glass- transition temperature of each composite was characteristic to the matrix resin and did not depend on the glass-fibre content, as it was expected. The effect of glass-fibre content on the storage modulus and on HDT has been elucidated. It has been found that up to 12 mass% (6?vol%) glass-fibre content the HDT did not change, above this value it increased with increasing glass-fibre content for each composite, but not at the same extent. This means that matrix-fibre interaction has an important role in the performance of the composites at elevated temperatures. Storage moduli increased with increasing glass-fibre content. The temperatures detected by dynamic mechanical thermal analysis corresponding to the storage modulus of 750?MPa??calculated by Takemori??are above the glass-transition and also increased with higher glass-fibre content in accordance with the real heat-distortion temperature measurements. It may be concluded that the effect of reinforcement on the performance of the composite could be detected more reliably by HDT measurements, since it gives information on the deformation of the composites. Matrix-fibre interaction has an essential role on the performance and on the HDT of the composite materials.     

Effects of electrically inert fillers on the properties of poly(<Emphasis Type="Italic">m</Emphasis>-xylene adipamide)/multiwalled carbon nanotube composites

The effects of three types of electrically-inert fillers, calcium carbonate (CaCO₃), talc and glass fiber (GF), on electrical resistivity, crystallization behavior and dynamic mechanical properties of poly(m-xylene adipamide) (MXD6)/multiwalled carbon nanotube (MWCNT) composites are investigated. The electrical resistivity of MXD6/MWCNT composites is significantly reduced with the addition of inert fillers due to the volume-exclusion effect that leads to increased effective concentration of MWCNTs in MXD6 matrix and also due to improved MWCNT dispersion. The crystallization temperature of MXD6 increases with the addition of MWCNTs, indicating that MWCNTs can act as nucleating agent and induce crystallization of MXD6. The incorporation of inert fillers has no further effect on crystallization behavior of MXD6, but significantly improves the storage modulus of MXD6/MWCNT composite, demonstrating that CaCO₃, talc and GF filled MXD6/MWCNT composites are very promising materials with not only improved electrical property but also excellent mechanical properties.     

Effects of Electrically Inert Fillers on the Properties of Poly(m-xylene adipamide)/Multiwalled Carbon Nanotube Composites

The effects of three types of electrically-inert fillers, calcium carbonate(CaCO_3), talc and glass fiber(GF), on electrical resistivity, crystallization behavior and dynamic mechanical properties of poly(m-xylene adipamide)(MXD6)/multiwalled carbon nanotube(MWCNT) composites are investigated. The electrical resistivity of MXD6/MWCNT composites is significantly reduced with the addition of inert fillers due to the volume-exclusion effect that leads to increased effective concentration of MWCNTs in MXD6 matrix and also due to improved MWCNT dispersion. The crystallization temperature of MXD6 increases with the addition of MWCNTs, indicating that MWCNTs can act as nucleating agent and induce crystallization of MXD6. The incorporation of inert fillers has no further effect on crystallization behavior of MXD6, but significantly improves the storage modulus of MXD6/MWCNT composite, demonstrating that CaCO_3, talc and GF filled MXD6/MWCNT composites are very promising materials with not only improved electrical property but also excellent mechanical properties.     

Mechanical properties of phenol/formaldehyde resin composites reinforced by cellulose microcrystal with different aspect ratio extracted from sisal fiber

Sisal cellulose fiber (SCF) and sisal fiber cellulose microcrystal (SFCM), produced with sulfate pulping method and ball‐milling approach separately, were in‐situ polymerized and dispersed into phenol/formaldehyde (PF) resin, to manufacture SCF/PF and SFCM/PF composites via rolling and molding method and investigate the effect of SCF and SFCM on the impact, flexural, and dynamic mechanical properties of the SCF/PF and SFCM/PF composites. As a result, under the condition of same content, SFCM could preferably enhance these properties maybe resulting from the better dispersion in resin matrix than SCF. In particular, when SFCM content was 7%, the impact strength and equilibrium relaxation modulus of the SFCM/PF composite were increased by 26.5% and 37.7%, while the creep deformation was decreased by 26.5%. In addition, when SFCM content was 5%, the flexural strength, initial storage modulus and glass transition temperature of SFCM/PF composite were increased by 8.5%, 22.6%, and 13°C. Copyright © 2016 John Wiley & Sons, Ltd.     

Preparation and properties of POSS grafted polypropylene by reactive blending

The octavinyl polyhedral oligomeric silsesquioxane (POSS) grafted polypropylene (PP) was first prepared by reactive blending. The structure and properties of physical blending and reactive blending composites of PP/POSS were investigated by wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA). WAXD analysis shows that the POSS in the reactive blending composites has better compatibility with PP than in the physical blending composites. The β-form crystalline hence disappears even the non-reactive POSS can act as an effective β-nucleating agents. DSC analysis shows the reactive blending composites have higher crystalline temperature while POSS in the physical blending composites have little effect on the crystalline temperature. The modulus of reactive blending composites increases in the presence of POSS, while that of the physical blending composites decreases with increasing POSS content.     

Structure and properties of composites of highly crystalline cellulose with polypropylene: Effects of polypropylene molecular weight

Composite of highly crystalline fibrous cellulose (CE) and polypropylene (PP) of different molecular weights () was prepared via melting-mixing, maleic anhydride grafted polypropylene (MAPP) was used as a compatibilizer. And the effects of molecular weight of PP on the properties of the composites were investigated. Through the studying of mechanical properties, dynamic mechanical properties, melting and crystallization behaviors, thermo-oxidative properties, water absorption behaviors, and the morphology of the composites, it was found that PP with higher molecular weight revealed stronger interfacial interaction with cellulose in the composites. Compared with the lower molecular weight, the composites derived from higher molecular weight of PP exhibited stronger tensile strength at the same cellulose content.     

PROPERTIES OF THERMO-MOLDED GLUTEN/GLYCEROL/SILICA COMPOSITES

Environmentally friendly thermosetting composites were successfully prepared by conventional blending wheat gluten as matrix,glycerol as plasticizer and silica as filler followed by thermo-molding of the mixture at 120℃.The strong interfacial interaction between silica particles and gluten proteins leaded to an increase in storage modulus and a decrease in loss factor as revealed by dynamic mechanical analysis.The moisture absorption and elongation at break decrease while Young's modulus and tensile stre...     

Effect of AlN content on the performance of brominated epoxy resin for printed circuit board substrate

Polymer matrix composites, based on brominated epoxy, a type of material widely used in printed circuit boards (PCBs), as matrix and AlN particle as filler were prepared. The influences of AlN content on the mechanical, thermal, and electrical properties of the composites were investigated by uniaxial tensile test, TMA, thermal conductivity measurement, DMA, and dielectric properties measurement. It was found that the properties of composites monotonically varied with AlN content except that maximum tensile strength and strain of composites corresponded to a filler content of 10 wt %. The results of DMA also showed the AlN reinforcement was more pronounced above T_g, and the peak area of tan δ versus T curves decreased with AlN content, which implied the damping capacity of the composite gradually decreased. The increase in T_g and decrease in damping were probably due to strong interaction between the AlN and epoxy matrix inhibiting the mobility of the epoxy chain. In addition, different theoretical models reported in the literature were used to predict the E, CTE, k, and D_k, and compared with the experimental data. Finally, suitable models were recommended in the present materials system. For the significant improvement of performance of epoxy, we can conclude that these composite materials may be promising for PCB substrate. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1662–1674, 2007     

Thermodynamic properties of liquid Au-Cu-Sn alloys determined from electromotive force measurements

A thermally conductive linear low-density polyethylene (LLDPE) composite with aluminum nitride (AlN) as filler was prepared in a heat press molding. Differential scanning calorimeter results indicated that the AlN filler decreases the degree of crystallinity of LLDPE, and has no obvious influence on the melting temperature of LLDPE. Experimental results demonstrated that the LLDPE composites display a high thermal conductivity of 1.25 W/m K and improved thermal stability at 70 wt% AlN content as compared to pure LLDPE. The dielectric constant and dissipation factor increased with AlN content, however, they still remained at relatively low levels, i.e., <5 in wider frequency range from 10 to 10⁶ Hz. The surface treatment of AlN particles had a beneficial effect on improving the thermal conductivity and dielectric constant, whereas, the dissipation factor was less affected. Additionally, the obtained AlN/LLDPE composites have possessed rather low dielectric constant and high electrical insulation, which is suitable for substrate and packaging materials.     

Preparation of high performance composites based on aluminum nitride/poly(ether-ether-ketone) and their properties

Novel high performance aluminum nitride (AlN)/poly(ether-ether-ketone) (PEEK) composites containing 0-50 wt.% fractions of AlN were prepared by solution blending method followed by hot pressing to evaluate their density, melting temperature, crystallization, thermal stability, morphological behavior and Vickers hardness by using different characterization techniques. Differential scanning calorimetry results indicated that the AlN particles are very effective nucleating agent, which results in increase in melting point, hot crystallization temperature and crystallinity of composites as the AlN content increases. Thermogravimetric analysis showed enhanced thermal stability of the composites with respect to PEEK. Density and X-ray diffraction techniques showed that crystallinity of the composites increases as the wt.% of AlN content increases in polymer matrix. Scanning electron microscopy revealed that AlN particles were well dispersed with no porosity in composites. Vickers hardness of the samples increased from 24 kg/mm² for the pure PEEK to 35 kg/mm² for AlN/PEEK composites.     

Preparation and properties of graphene oxide nanosheets/cyanate ester resin composites

Graphene oxide nanosheets (GONSs)/cyanate ester (CE) resin composites were prepared via a solution intercalation method. The structures of the GONSs and the composites were studied using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The mechanical and tribological properties of the composites were investigated. In addition, the thermal behavior of the composites was characterized by thermogravimetric analysis (TGA). Results show that the GONSs/CE resin composites were successfully prepared. The addition of GONSs is beneficial to improve the mechanical and tribological properties of the composites. Moreover, the composites exhibit better thermal stability in comparison with the CE resin matrix.     

MECHANICAL PROPERTIES OF SMC WHISKER REINFORCED HIGH DENSITY POLYETHYLENE COMPOSITES

A new type of SiO_2-MgO-CaO (SMC) whisker was used to modify high density polyethylene (HDPE).The melting behavior and crystallinity were investigated by differential scanning calorimetry (DSC).The dispersion of whiskers and interfacial adhesion in the prepared HDPE/SMC whisker composites were investigated by scanning electron microscopy (SEM).The mechanical properties were evaluated by mechanical tests and dynamic mechanical analysis (DMA).DSC data indicated that the melting temperature and the crystall...     

Carbon nanotube reinforced biobased poly(urethane urea) covalent adaptable network composite

A solvent-free approach was developed to incorporate carbon nanotube (CNT) into castor oil derived poly(urethane urea) (PPU) covalent adaptable network (CAN) based on dynamic piperidine-urea bonds to fabricate CNT reinforced PPU composites. The approach includes two steps i.e., pre-polymerization of castor with isophorone diisocyanate in flask and subsequent chain-extension with 1,3-bis(4-piperidinyl)propane (PIP) in the presence of CNT in an internal mixer. The effect on CNT content of the morphology, mechanical property, stress relaxation, and reprocessability of the PPU/CNT composites was investigated in detail. The results demonstrated that CNT dispersed well in the PPU networks due to the applied strong shear force which facilitated the dispersion of CNT in the PPU matrix before cross-linking. The well-dispersed CNT reinforced the mechanical properties of PPU significantly and the Young's modulus (E) of the composites were enhanced significantly when the content of CNT was ≥6 wt% due to the formation of CNT network in the PPU matrix. When the content of CNT was 10 wt%, the E of PPU-10%CNT was 927.59 ± 149.05 MPa, which was improved by ~60% compared to PPU. The reprocessability of the PPU network was remained although the stress relaxation rate was reduced with incorporation and increasing content of CNT. In addition, the PPU/CNT composites could be degraded chemically to recycle CNT through reaction of the dynamic piperidine-urea bonds with additional PIP.     

Mechanical and viscoelastic properties of chitin fiber reinforced poly(ε-caprolactone)

Poly(ε-caprolactone)/chitin fiber (PCL-CF) composites as potential bone substitutes were prepared using a simple melt-processing method. The results from differential scanning calorimetry and dynamic mechanical thermal analysis (DMTA) showed that there was interaction between PCL and CF. Static mechanical testing showed that tensile strength, Young’s modulus and flexural strength were increased by the addition of CF. The measurements from DMTA and an advanced rheometric expansion system showed that both the storage modulus and loss modulus were enhanced by CF. The PCL-CF composite with CF of 45% by mass had the best properties among all the tested composites.     

Development of continuous process enabling nanofibrillation of pulp and melt compounding

Microfibrillated cellulose (MFC), a mechanically fibrillated pulp mostly consisting of nanofibrils, is a very attractive material because of its high elastic modulus and strength. Although much research has been done on composites of MFC and polypropylene (PP), it has been difficult to produce such composites at an industrial level because of the difficulties in using MFC in such composites are not only connected to the polarity (that can be improved with compatibilizers), but also with the challenge to make a homogeneous blend of the components, and also the low temperature stability of cellulose that could cause problems during processing. We developed a new processing method which enables continuous microfibrillation of pulp and its melt compounding with PP. Never-dried kraft pulp and powdered PP were used as raw materials to obtain MFC by kneading via a twin-screw extruder. Scanning electron microscopy showed nano to submicron wide fibers entangled in the powdered PP. MFC did not aggregate during the melt compounding process, during which the water content was evaporated. Maleic anhydride polypropylene (MAPP) was used as a compatibilizer to reinforce interfacial adhesion between the polar hydroxyl groups of MFC and non-polar PP. We investigated the effect of MAPP content on the mechanical properties of the composite, which were drastically improved by MAPP addition. Needle-leaf unbleached kraft pulp (NUKP)-derived MFC composites had better mechanical properties than needle-leaf bleached kraft pulp (NBKP)-derived MFC composites. Injection molded NUKP-derived MFC composites had good mechanical and thermal properties. The tensile modulus of 50 wt% MFC composite was two times, and the tensile strength 1.5 times higher than that of neat PP. The heat distortion temperature of 50 wt% MFC content composite under 1.82 MPa flexural load was increased by 53 °C, from 69 to 122 °C. This newly developed continuous process using powder resin has the potential for application at an industrial level.     

Rheology,crystallization behavior,and mechanical properties of poly(butylene succinate-co-terephthalate)/cellulose nanocrystal composites

A series of biodegradable poly (butylene succinate-co-terephthalate) (PBST) with different aromatic units content was synthesized and then melt blended by adding cellulose nanocrystals (CNCs) to manufacture the full organic composites. A network-like structure of CNCs in PBST matrix was evaluated by rheometer. The storage modulus and complex viscosity at low frequency region were significantly enhanced with increasing CNC content. Meanwhile, the decreasing $\tan \delta$ and flow index were attributed to the excellent interaction between PBST and CNCs. When PBST has a content of the aromatic unit exceeds 30 mol%, the crystallization temperatures increased with increasing CNC contents. On the other hand, when PBST has 30 mol% content of the aromatic unit, the cold crystallization temperatures decreased with increasing CNC contents. These above observation in crystallization properties suggested that the CNC make a role of heterogeneous nucleation in PBST matrix. The result of mechanical properties evaluated by dynamic mechanical analysis showed a good reinforcement effect of the addition of stiff CNC. The PBST/CNC composites were suitable for cell growth and might have a potential as biomedical materials, which is confirmed by MTT assay.     

Mechanical, thermal, and moisture absorption properties of nano-clay reinforced nano-cellulose biocomposites

In this research, fully environment-friendly, sustainable and biodegradable ‘green’ composites were fabricated. A novel material comprised of microfibrillated cellulose and laponite clay with different inorganic/organic ratios (m/m) was prepared. The composites were characterized by tensile, bending and water absorption tests as well as dynamic mechanical analysis. The morphologies of these nanocomposites were evaluated through scanning electron microscopy. Results showed considerable improvement of mechanical properties; specifically in elastic modulus, tensile strength and flexural modulus with the addition of nanoclay up to 7.5 wt% nano-clay. The modulus of elasticity increased significantly by about 26 % at 5 wt% nanocaly. The flexural modulus increased by about 90 % at 7.5 wt% nanoclay. However, with an increased load of clay in the nanocomposite, the mechanical properties decreased due to the agglomeration of excessive nanoclay. The storage modulus was significantly increased at high temperature with increasing the load of nanoclay.