Thermal and dynamic mechanical properties of organic–inorganic hybrid composites of itaconate‐containing poly(butylene succinate) and methacrylate‐substituted polysilsesquioxane

Itaconate‐unit‐containing poly(butylene succinate) (PBSI) was synthesized by the reaction of 1,4‐butanediol, succinic acid, and itaconic acid in a molar ratio of 2.0 : 1.0 : 1.0, and the obtained PBSI was reacted with methacryl‐group‐substituted polysilsesquioxane (ME‐PSQ) in the presence of benzoyl peroxide (BPO) at 130°C to produce PBSI/ME‐PSQ hybrid composites. The thermal and dynamic mechanical properties of the PBSI/ME‐PSQ hybrid composites were investigated in comparison with those of PBSI cured at 130°C in the presence of BPO. As a result, the hybrid composites showed a much higher thermal degradation temperature and storage modulus in the rubbery state than the cured PBSI (C‐PBSI). The thermal degradation temperature and storage modulus of the hybrid composites increased with increasing ME‐PSQ content. The glass‐transition temperature, measured by dynamic mechanical analysis of the hybrid composites, somewhat increased with increasing ME‐PSQ content. However, the glass‐transition temperatures of all the hybrid composites were lower than that of C‐PBSI. Although the IR absorption peak related to C?C groups was not detected for C‐PBSI, some olefinic absorption peaks remained for all the hybrid composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Thermal and mechanical properties of photocured organic–inorganic hybrid nanocomposites of terpene‐based acrylate resin and methacrylate‐substituted polysilsesquioxane

Diacrylate compounds derived from α‐pinene and limonene (TDAs: TDA‐1 and TDA‐2) were photocured with methacryl‐substituted polysilsesquioxane (ME‐PSQ) prepared from 3‐(trimethoxysilyl)propyl methacrylate and tetramethylammonium hydroxide (TMAOH) in the TDA/ME‐PSQ weight ratio of 20 : 0, 20 : 1, 20 : 2, 20 : 3, and 20 : 4. All the photocured TDA/ME‐PSQ hybrid nanocomposites became transparent. The thermomechanical analysis of the cured TDA/ME‐PSQ revealed that the glass transition temperature (T_g) increased, the thermal expansion coefficient above T_g decreased with increasing ME‐PSQ content, and that the TDA‐1/ME‐PSQ had ca. 30°C greater T_g than the TDA‐2/ME‐PSQ with the same ME‐PSQ content. Also, the dynamic mechanical analysis revealed that the TDA‐1/ME‐PSQ had much greater storage modulus at around 150°C than the corresponding TDA‐2/ME‐PSQ. The flexural strength and modulus of the TDA/ME‐PSQ nanocomposites at 20°C had maximum at ME‐PSQ content 4.8 and 13.0 wt %, respectively. As a whole, the thermal and mechanical properties of the nanocomposites were improved by the addition of ME‐PSQ, and those of TDA‐1/ME‐PSQ nanocomposites were superior to those of TDA‐2/ME‐PSQ. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation of highly emissive,thermally stable,UV‐cured polysilsesquioxane/ZnO nanoparticle composites

A high molecular weight polysilsesquioxane (LPMSQ)/ZnO nanocomposite was prepared by blending a methacryl‐substituted polysilsesquioxane and PMMA‐coated ZnO nanoparticle (NP) followed by UV‐curing process. These LPMSQ/ZnO nanocomposites gave high thermal and mechanical stabilities originated from the rigid ladder structured siloxane backbone of LPMSQ. The polysilsesquioxane and surface‐modified ZnO nanoparticles showed excellent compatibility between MMA groups in LPMSQ‐ and PMMA‐capped ZnO nanoparticles to give well‐dispersed LPMSQ/ZnO nanocomposites. Mechanically pliant and flexible free standing films were obtained, and the photo and optical properties of these hybrid nanocomposites were examined. The high photoluminescent properties were maintained even after severe thermal treatments exceeding 400°C. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42333.     

Fabrication and properties of chemically bonded polysilsesquioxane‐polyacrylate/silica hybrid latex films with high silicon content

Polysilsesquioxane‐polyacrylate/silica hybrid latexes (PSQ‐PAS) with high silicon content were prepared by directly mixing colloidal silica with polysilsesquioxane‐polyacrylate emulsion (PSQ‐PA), which was prepared through seeded emulsion polymerization using polymethacryloxypropylsilsesquioxanes as the core and polyacrylate (PA) as the shell respectively. The chemically bonded PSQ‐PAS thin films were obtained via sol‐gel process after addition of hydrophilic cosolvent to PSQ‐PAS emulsion and subsequent drying at room temperature. The effects of silica/PSQ‐PA ratio (w/w) on the film properties of hardness, optical property and thermal stability were investigated. Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) and transmission electron microscopy (TEM) were used to characterize the chemical composition and morphology of the resultant hybrid particles. DLS and TEM results indicated that both PSQ and PSQ‐PA particles had narrow size distribution and their average diameters were about 200 and 350 nm, respectively. Pendulum durometer, UV–vis spectroscopy, and thermogravimetric analysis (TGA) were used to characterize the hardness, optical property and thermal stability of PSQ‐PAS latex films. The results showed that the PSQ‐PAS films hardness increased with the increasing ratio of silica/PSQ‐PA, whereas the transmittance decreased slightly. TGA curves demonstrated PSQ‐PAS films displayed excellent thermal stability, and the residual silicon weight exceeded 30%. POLYM. COMPOS., 36:389–396, 2015. © 2014 Society of Plastics Engineers     

Structure and properties of UHMWPE fiber/carbon fiber hybrid composites

Ultrahigh molecular weight polyethylene (UHMWPE) fiber/carbon fiber hybrid composites were prepared by inner‐laminar and interlaminar hybrid way. The mechanical properties, dynamic mechanical analysis (DMA), and morphologies of the composites were investigated and compared with each other. The results show that the hybrid way was the major factor to affect mechanical and thermal properties of hybrid composites. The resultant properties of inner‐laminar hybrid composite were better than that of interlaminar hybrid composite. The bending strength, compressive strength, and interlaminar shear strength of hybrid composites increased with an increase in carbon fiber content. The impact strength of inner‐laminar hybrid composite was the largest (423.3 kJ/m²) for the UHMWPE fiber content at 43 wt % to carbon fiber. The results show that the storage modulus (E′), dissipation factor (tan δ), and loss modulus (E″) of the inner‐laminar hybrid composite shift toward high temperature remarkably. The results also indicate that the high‐performance composite with high strength and heat resistance may be prepared by fibers' hybrid. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1880–1884, 2006     

Preparation and characterization of trilayer core–shell polysilsesquioxane–fluoroacrylate copolymer composite emulsion particles

Polysilsesquioxane–fluoroacrylate copolymer [poly(methyl methacrylate)–butyl acrylate–dodecafluoroheptyl methacrylate)] (FPSQ) composite latex particles with a trilayer core–shell morphology were manufactured by seeded emulsion polymerization, where PSQ latex particles bearing reactive methacryloxypropyl moieties were first produced by the hydrolysis‐condensation of (3‐methacryloxypropyl)trimethoxysilane, and then they were utilized as seeds, with methyl methacrylate, butyl acrylate, and dodecafluoroheptyl methacrylate as the inner and outer shell monomers. Fourier‐transform infrared spectra and ¹H‐NMR confirm the structure of the FPSQs. Transmission electron microscopy and scanning electron microscopy demonstrate that the obtained composite emulsion particles emerge with the trilayer core–shell pattern. Due to the anchoring of PSQ nanoparticles, the thermal stabilities of the FPSQ films are strengthened, and the resistance to heat is gradually improved along with the increase of the fluoroacrylate dose in the polymer matrix composite. X‐ray photoelectron spectroscopy, atomic force microscopy (AFM), and hydrophobicity investigations indicate that the fluorinated chain segments tend to concentrate at the film–air two‐phase interface. In addition, the AFM result denotes that importing more fluorine into the FPSQ hybrid material will engender greater phase separation and enrichment of the fluoroalkyl segments and a rougher morphology. Thus, the water contact angle of the FPSQ film can ultimately reach 121.4°. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44845.     

Preparation and properties of APPSSQ‐like/polyimide hybrid composites

Hydrolysis and condensation proceeded to generate 3‐aminopropyl polysilsesquioxane‐like (APPSSQ‐like) particles from 3‐aminopropyl triethoxysilane. An APPSSQ‐like particle includes two domains: crosslinking Si? O? Si networks inside and 3‐aminopropyl groups outside the particle. The APPSSQ‐like/polyimide (APPSSQ‐like/PI) hybrid composites were prepared from a solution of poly(amic acid) (PAA, polyimide precursor) and APPSSQ‐like particles using N,N‐dimethylacetamide as a solvent. Scanning electron microscopy (SEM) showed that the APPSSQ particle sizes were about 100 nm, and there was no obvious phase separation between the APPSSQ‐like particles and the PI matrix in the fracture surfaces of the hybrid films. Owing to the highly crosslinked Si? O? Si networks inside the APPSSQ‐like particles, the APPSSQ‐like/PI hybrid composites possessed desired properties such as improved thermal resistance and reduced coefficients of thermal expansion (CTE). The presence of covalent bonds between the APPSSQ‐like particles and the PI molecules improved the compatibility between these two components. Thus, the tensile strength increased with the APPSSQ‐like content, and the elongation at break also slightly increased with the APPSSQ‐like content. The initial tensile and storage moduli of the APPSSQ‐like/PI hybrid composites increased with the APPSSQ‐like content, which indicates that the mechanical properties of these hybrid composites were enhanced by the incorporation of the APPSSQ‐like content in the PI matrix. Furthermore, the glass transition temperatures of these composites increased with the APPSSQ‐like content because the adhesion between the APPSSQ‐like particles and the PI molecules restricts the PI chains' mobility. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2865–2874, 2003     

Effects of acrylic‐based processing aids on processibility,rheology, thermal and structural stability,and mechanical properties of PVC/wood–sawdust composites

Methyl methacrylate and ethylacrylate (MMA‐co‐EA) and methyl methacrylate and butylacrylate (MMA‐co‐BA) copolymeric processing aids were introduced into poly(vinyl chloride) (PVC)/33.3 wt % wood–sawdust composites containing 0.6 and 2.4 phr of calcium stearate lubricant. The properties of the composites were monitored in terms of processibility, rheology, thermal and structural stability, and mechanical properties. It was found that the mixing torque, wall shear stress, and extrudate swell ratio increased with increasing processing aid content because of increased PVC entanglement. MMA‐co‐BA (PA20) was found to be more effective than MMA‐co‐EA (K120 and K130), this being associated with the flexibility of the processing aids, and the dipole–dipole interactions between sawdust particles and polymeric processing aids. The sharkskin characteristic of the composite extrudate at high extrusion rate was moderated by the presence of processing aids. Adding the acrylic‐based processing aids and lubricant into PVC/sawdust composites improved the thermal and structural stability of the composites, which were evidenced by an increase in glass transition and decomposition temperatures and a decrease in polyene sequences, respectively. The changes in the mechanical properties of the composites involved a composite homogeneity, which was varied by degree of entanglement and the presence of wood sawdust, and un‐reacted processing aids left in the composites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 782–790, 2004     

Effect of fiber orientation on viscoelastic properties of polymer matrix composites subjected to thermal cycles

Fibers in polymer composites can be designed in various orientations for their usage in service life. Various fiber orientated polymer composites, which are used in aeroplane and aerospace applications, are frequently subjected to thermal cycles because of the changes in body temperatures at a range of −60 to 150°C during flights. It is an important subject to investigate the visco‐elastic properties of the thermal cycled polymer composite materials which have various fiber orientations during service life. Continuous fiber reinforced composites with a various fiber orientations are subjected to 1,000 thermal cycles between the temperatures of 0 and 100°C. Dynamic mechanic thermal analysis (DMTA) experiments are carried out by TA Q800 type equipment. The changes in glass transition temperature (T_g), storage modulus (E′), loss modulus (E′′) and loss factor (tan δ) are inspected as a function of thermal cycles for different fiber orientations. It was observed that thermal and dynamic mechanical properties of the polymer composites were remarkably changed by thermal cycles. It was also determined that the composites with [45°/−45°]_s fiber orientation presented the lowest dynamic mechanical properties. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Cellulose acetate/polysilsesquioxane composites: Thermal properties and morphological characterization by electron spectroscopy imaging

Cellulose acetate (CA) composites using two types of silane coupling agents (methyltrimethoxysilane and phenyltriethoxysilane) were prepared through two methodologies: direct reaction between CA and the specific monomer and reaction of CA with oligomers, which were produced by prehydrolysis of the same monomers. The thermal behavior and morphology of the materials were studied. The composites showed thermal stability similar to pure CA, increase of residue content at 790°C and reduction in the glass transition temperature. Complementary microscopy techniques were applied to investigate the distribution of polysilsesquioxane in the CA matrix. Silicon mapping images showed the presence of domains with higher polysilsesquioxane concentration than the matrix and also the presence of silicon‐rich nanodomains dispersed throughout the matrix. Based on mapping characterization, a schematic representation of the CA/polysilsesquioxane composite morphology was proposed. The organosilane type and architecture influenced the thermal behavior and the morphology of these materials. The results suggest that the silane coupling agents could be used to produce CA films with a range of properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation and thermal energy storage properties of poly(n‐butyl methacrylate)/fatty acids composites as form‐stable phase change materials

This work is focused on the preparation, characterization, and determination of thermal energy storage properties of poly(n‐butyl methacrylate) (PnBMA)/fatty acid composites as form‐stable phase change material (PCM). In the composite materials, the fatty acids act as latent heat storage material whereas PnBMA serves as supporting material, which prevents the leakage of the melted fatty acids. The maximum encapsulation ratio for all fatty acids was found to be 40 wt%. The composites that do not allow PCM leakage in melted state were identified as form‐stable PCMs. The compatibility of fatty acids with PnBMA is investigated by optical microscopy (OM) and Fourier Transform Infrared (FT‐IR) spectroscopy. Thermal properties and thermal reliability of the form‐stable composite PCMs were determined using differential scanning calorimetry (DSC). DSC analysis revealed that the form‐stable composite PCMs had melting temperatures between 29.62°C and 53.73°C and latent heat values between 67.23 J/g and 87.34 J/g. Thermal stability of the composite PCMs was studied by thermal gravimetric (TG) analysis and the results indicated that the form‐stable PCMs had good thermal stability. In addition, thermal cycling test showed that the composite PCMs had good thermal reliability with respect to the changes in their thermal properties after accelerated 5,000 thermal cycling. On the basis of all results, it was also concluded that the prepared form‐stable composite PCMs had important potential for many thermal energy storage applications such as solar space heating of buildings by using wallboard, plasterboard or floors integrated with PCM. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers     

The influence of post‐cure on properties of carbon/phenolic resin cured composites and their final carbon/carbon composites

Two‐dimensional (2D) carbon/carbon (C/C) composites were prepared with phenol‐formaldehyde resin and graphite fabric. After curing, polymer composites were post‐cured in air at 160°C and 230°C for several hours and then all polymer composites were carbonized up to 1500°C. The effect of post‐cure on the microstructure and fracture behavior of the resultant carbon/carbon composites was studied. The post‐cure process was characterized by weight loss. This process promoted the crosslinking and condensation reactions and led to the formation of long‐chain, cross‐linked polymeric structures in the matrix. The post‐cured composites had a greater density than the unpost‐cured composite. This study indicates that a longer post‐curing time and higher post‐curing temperature would limit the shrinkage for the post‐cured composites during carbonization. The improvement in linear shrinkage was 22% to 44%. This process also limited the formation of open pores and decreased the weight loss of the resultant C/C composites. The resultant C/C composites developed from post‐cured composites had a greater flexural strength by 7 to 26% over that developed from unpost‐cured composite.     

Effect of acrylic copolymer dispersants bearing epoxy groups on rheological and dielectric properties of carbon black‐filled epoxy system

In this article, the use of copolymeric dispersants with an acrylic backbone and epoxy side groups for formulating carbon black (CB)‐epoxy composites are described. Six epoxy‐containing acrylic copolymer dispersants were prepared from hexyl methacrylate (HMA), poly(ethylene glycol) ethyl ether methacrylate (PEGMA), and glycidyl methacrylate via a group transfer polymerization technique. The epoxy‐containing acrylic copolymer of the highest concentration of PEGMA showed a desirable passivation effect on CB, and was found to lower the viscosity of the CB‐epoxy paste, leading to the well‐cured composite after heat treatment. The thick composite film prepared by employing the [CB/acrylic dispersant/epoxy] paste was built up on a Cu plate by a screen printing process followed by thermal curing. The dielectric properties of the 3.1 vol % CB‐filled epoxy film showed us high dielectric constant (Dk 4900) and rather low dissipation factor (Df 29%) at 1 MHz. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Morphology,thermal, and mechanical properties of vinylester resin nanocomposites with various organo‐modified montmorillonites

New nanocomposites based on a vinylester resin (VER) and the organo‐montmorillonites (ODA‐M, BHL‐M, DEM‐M, BHLV‐M) modified with octadecylammonium, bis(2‐hydroxyethyl)lauryl ammonium, diethyl[2‐(methacryloyloxyl)ethyl]ammonium, and bis(2‐hydroxyethyl)lauryl(vinylbenzyl)‐ammonium chlorides, respectively, were prepared by dispersing the organoclays in VER, and subsequent crosslinking at finally 120°C. X‐ray diffraction studies and morphological studies using transmission electron microscopy revealed that exfoliation occurs for the VER/ODA‐M and BHL‐M composites, intercalation occurs for the VER/BHLV‐M composite, and neither intercalation nor exfoliation occur for the VER/DEM‐M and unmodified montmorillonite composites. On the whole, although the enhancement in flexural modulus was observed for the exfoliated ODA‐M and BHL‐M composites, the flexural strength was rather lowered. Dynamic viscoelastic measurement revealed that the ODA‐M, BHL‐M, and BHLV‐M nanocomposites have significantly higher storage modulus at the rubbery state than the other composites. Polym. Eng. Sci. 44:2041–2046, 2004. © 2004 Society of Plastics Engineers.     

Silicone‐Organic Resin Hybrid Matrix Composites

Summary: Glass fabric reinforced hybrid matrix composites of a toughened silicone resin and a vinyl ester resin were fabricated and their properties investigated. The hybrid composites consisted of multi‐layers of fiber reinforced silicone resins and vinyl ester resins. The toughened silicone resin, a crosslinkable phenylsilsesquioxane resin with high thermal and thermal oxidation resistance but relatively low T_g, was chosen to be the outer layers. The vinyl ester resin, with better strength, toughness and a much higher T_g than the toughened silicone resin, was used as the inner layers. A co‐cure process proved to establish a strong interface between the two in a hybrid composite. The hybrid composites had better flammability properties and much lower short term moisture absorption than the vinyl ester composites. The strength and modulus retention of the hybrid composites at elevated temperatures was higher than the composites using any single resin as the matrix. For example, when tested at 150 °C the flexural modulus and strength values of a twelve layer composite, with eight inner vinyl ester resin layers and four silicone outer layers, were almost an order of magnitude higher than the composite using the silicone resin alone, and were significantly higher than the one using vinyl ester resin alone. The room temperature short beam shear strength of the hybrid composites was also higher. DMA revealed that the inter‐diffusion of reactive components between the two resins was probably responsible for this synergistic effect, resulting in an α transition temperature of 182 °C for the hybrid composite, higher than that of either the silicone resin (85 °C) or the vinyl ester resin (162 °C).

     

Investigation of electrical,mechanical, and thermal properties of functionalized multiwalled carbon nanotubes‐reduced graphene Oxide/PMMA hybrid nanocomposites

Electrical, mechanical, and thermal properties of the poly(methyl methacrylate) (PMMA) composites containing functionalized multiwalled carbon nanotubes (f‐MWCNTs) and reduced graphene oxide (rGO) hybrid nanofillers have been investigated. The observed electrical percolation threshold of FHC is 0.8 wt% with maximum conductivity of 1.21 × 10^?3 S/cm at 4 wt% of f‐MWCNTs. The electrical transport mechanism and magneto resistance studied of hybrid composites have also been investigated. Progressive addition of f‐MWCNTs in rGO/PMMA composite results increase in mechanical (tensile strength and Young's modulus) and thermal (thermal stability) properties of f‐MWCNTs‐rGO/PMMA hybrid nanocomposites (FHC). The increased mechanical properties are due to the efficient load transfer from PMMA matrix to f‐MWCNTs and rGO through better chemical interaction. The strong interaction between PMMA and f‐MWCNTs‐rGO in FHC is the main cause for improved thermal stability. POLYM. ENG. SCI., 59:1075–1083, 2019. © 2019 Society of Plastics Engineers     

Study of polyarylene ether nitrile terminated with phthalonitrile/hybrid Fe3O4 nanospheres composites by orthogonal experiments

A novel series of composites of polyarylene ether nitrile terminated with phthalonitrile (PEN‐t‐Ph) filled with hybrid Fe3O4 nanospheres (h‐Fe₃O₄) was prepared via in situ composition. Based on the cross‐linking interactions between the phthalonitrile at the end of PEN‐t‐Ph molecular chains and the phthalonitrile on the surface of h‐Fe₃O₄ particles to form phthalocyanine ring, it was shown that the PEN‐t‐Ph/h‐Fe₃O₄ system had superior interfacial compatibility and the h‐Fe₃O₄ particles were locked in the matrix resin. These results had been confirmed by scanning electron microscope analysis. By orthogonal experiments and statistic analysis, the optimal conditions of cure temperature, type of h‐Fe₃O₄ and content of h‐Fe₃O₄ had been determined. Meanwhile, the results of range analysis and variance analysis indicated that the cure temperature had great effects on the thermal properties. Thermal studies revealed that the glass transition temperature of PEN‐t‐Ph/h‐Fe₃O₄ cured at 320°C was 214.7°C, increased by about 40°C compared to the PEN‐t‐Ph/h‐Fe₃O₄ without heat treatment, and the temperature corresponding to the weight loss of 5 wt % was increased by about 20°C. Mechanical measurements indicated that PEN‐t‐Ph/h‐Fe₃O₄ cured at 320°C possesses excellent mechanical properties with tensile strength of 93.33 MPa and tensile modulus of 2414.05 MPa, 9.91 MPa, 355.76 MPa higher than pure PEN‐t‐Ph film cured at 320°C, and 13.26 MPa, 397.90 MPa higher than PEN‐t‐Ph/h‐Fe₃O₄ without heat treatment. Most importantly, the presence of h‐Fe₃O₄ particles endows PEN‐t‐Ph/h‐Fe₃O₄ system with good magnetic property. Thus, PEN‐t‐Ph/h‐Fe₃O₄ cured at 320°C may have potential applications in field of magnetic materials. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40418.     

Poly(methyl methacrylate)‐grafted cellulose nanocrystals: One‐step synthesis,nanocomposite preparation,and characterization

Cellulose nanocrystals (CNCs) are ideal reinforcing agents for polymer nanocomposites because they are lightweight and nano‐sized with a large aspect ratio and high elastic modulus. To overcome the poor compatibility of hydrophilic CNCs in non‐polar composite matrices, we grafted poly(methyl methacrylate) (PMMA) from the surface of CNCs using an aqueous, one‐pot, free radical polymerization method with ceric ammonium nitrate as the initiator. The hybrid nanoparticles were characterized by CP/MAS NMR, X‐ray photoelectron spectroscopy, infrared spectroscopy, contact angle, thermogravimetric analysis, X‐ray diffraction, and atomic force microscopy. Spectroscopy demonstrates that 0.11 g/g (11 wt %) PMMA is grafted from the CNC surface, giving PMMA‐g‐CNCs, which are similar in size and crystallinity to unmodified CNCs but have an onset of thermal degradation 45 °C lower. Nanocomposites were prepared by compounding unmodified CNCs and PMMA‐g‐CNCs (0.0025–0.02 g/g (0.25–2 wt %) loading) with PMMA using melt mixing and wet ball milling. CNCs improved the performance of melt‐mixed nanocomposites at 0.02 g/g (2 wt %) loading compared to the PMMA control, while lower loadings of CNCs and all loadings of PMMA‐g‐CNCs did not. The difference in Young's modulus between unmodified CNC and polymer‐grafted CNC composites was generally insignificant. Overall, ball‐milled composites had inferior mechanical and rheological properties compared to melt‐mixed composites. Scanning electron microscopy showed aggregation in the samples with CNCs, but more pronounced aggregation with PMMA‐g‐CNCs. Despite improving interfacial compatibility between the nanoparticles and the matrix, the effect of PMMA‐g‐CNC aggregation and decreased thermal stability dominated the composite performance.     

Water absorption behavior of PALF/GF hybrid polyester composites

The water absorption characteristics of pineapple leaf fiber (PALF)/glass fiber (GF) hybrid polyester(PER) composites, and chemically modified PALF/polyester composites were evaluated by immersion in distilled water at 28, 60, and 90°C. The diffusion properties of the intimately mixed (IM) and the layered hybrid composite GPG (Glass skin and PALF core) of different PALF/GF ratio at the three temperatures were compared in order to identify the environmental ageing mechanism at different temperatures. The effect of temperature on the kinetics and thermodynamics of diffusion were also examined. The water uptake of both IM and GPG hybrid composites was decreased with increase in glass fiber content; the lowest water uptake was observed for 0.46 V_f GF hybrid composite. Among the chemically modified composites, vinyl tri 2‐methoxy ethoxy silane treated composites showed the lowest water uptake. Finally, parameters like diffusion, sorption, and permeability coefficients were determined. It was observed that equilibrium water uptake is dependent on the nature of the composite and temperature. Experimental results were also compared with theoretical predictions. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Flammability and thermomechanical properties of dianhydride‐modified polybenzoxazine composites reinforced with carbon fiber

Composites based on carbon fiber (CF) and benzoxazine (BA‐a) modified with PMDA were investigated. The flammability of the carbon fiber composites was examined by limiting oxygen index (LOI) and UL‐94 vertical tests. The LOI values increased from 26.0 for the CF/poly(BA‐a) composite to 49.5 for the CF‐reinforced BA‐a/PMDA composites as thin as 1.0 mm and the CF‐reinforced BA‐a/PMDA composites were also achieved the maximum V‐0 fire resistant classification. Moreover, the incorporation of the PMDA into poly(BA‐a) matrix significantly enhanced the T_g and the storage modulus (E') values of the CF‐reinforced BA‐a/PMDA composites rather than those of the CF/poly(BA‐a). The T_g values and storage moduli of the obtained CF‐reinforced BA‐a/PMDA composites were found to have relatively high value up to 237°C and 46 GPa, respectively. The CF‐reinforced BA‐a/PMDA composites exhibited relatively high degradation temperature up to 498°C and substantial enhancement in char yield with a value of up to 82%, which are somewhat higher compared to those of the CF/poly(BA‐a) composite, i.e., 405°C and 75.7%, respectively. Therefore, due to the improvement in flame retardant, mechanical and thermal properties, the obtained CF‐reinforced BA‐a/PMDA composites exhibited high potential applications in advanced composite materials that required mechanical integrity and self‐extinguishing property. POLYM. COMPOS., 34:2067–2075, 2013. © 2013 Society of Plastics Engineers