Synthesis and mechanical properties of unsaturated polyester based nanocomposites

Two classes of nanocomposites were synthesized using an unsaturated polyester resin as the matrix and sodium montmorillonite as well as an organically modified montmorillonite as the reinforcing agents. X‐ray diffraction pattern of the composites showed that the interlayer spacing of the modified montmorillonite expanded from 1.25 nm to 4.5 nm, indicating intercalation. Glass transition values of these composites increased from 72°C, in the unfilled unsaturated polyester, to 86°C in the composite with 10% organically modified montmorillonite. From Scanning Electron Microscopy, it is seen that the degree of intercalation/exfoliation of the modified montmorillonite is higher than in the unmodified one. The mechanical properties also supported these findings, since in general, the tensile modulus, tensile strength, flexural modulus, flexural strength and impact strength of the composites with modified montmorillonite were higher than the corresponding properties of the composites with unmodified montmorillonite. The tensile modulus, tensile strength, flexural modulus and flexural strength values showed a maximum, whereas the impact strength exhibited a minimum at approximately 3–5 wt% modified montmorillonite content. These results imply that the level of exfoliation may also exhibit a maximum with respect to the modified montmorillonite content. The level of improvement in the mechanical properties was substantial. Adding only 3 wt% organically modified clay improved the flexural modulus of unsaturated polyester by 35%. The tensile modulus of unsaturated polyester was also improved by 17% at 5 wt% of organically modified clay loading.     

Reinforcement on the mechanical‐, thermal‐, and water‐resistance properties of the wood flour/chitosan/poly(vinyl chloride) composites by physical and chemical modification

In this study, we aimed to physically and chemically modify wood flour (WF)/chitosan (CS) mixtures to reinforce the mechanical‐, thermal‐, and water‐resistance properties of WF/CS/poly(vinyl chloride) (PVC) composites with a three‐step modification process. This was a vacuum‐pressure treatment of sodium montmorillonite, inner intercalation replacement of organically modified montmorillonite, and surface grafting of glycidyl methacrylate (GMA). The untreated and modified mixtures were characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy–energy‐dispersive spectroscopy, thermogravimetric analysis, and contact angle measurement. Meanwhile, the mechanical strengths and water absorption of WF/CS/PVC were estimated. The results indicate that the samples had a better performance after they were modified by montmorillonite (MMT) + GMA than when they were modified by only MMT. MMT and GMA showed a very synergistic enhancement to the mechanical‐, thermal‐, and water‐resistance properties of the WF/CS/PVC composites. Specifically, the maximum flexural and tensile strengths were increased by 10.59 and 12.28%, respectively. The maximum water absorption rate was decreased by 61.99%, and the maximum degradation temperature was delayed to the higher value from 314.3 and 374.9°C in the untreated sample to 388.8 and 412.8°C. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40757.     

Thermal and mechanical properties of melt processed intercalated poly(methyl methacrylate)–organoclay nanocomposites over a wide range of filler loading

BACKGROUND: Poly(methyl methacrylate) (PMMA)–organoclay nanocomposites with octadecylammonium ion‐modified montmorillonite, prepared via melt processing, over a wide range of filler loading (2–16 wt%) were investigated in detail. These hybrids were characterized for their dispersion structure, and thermal and mechanical properties, such as tensile modulus (E), break stress (σ_brk), percent break strain (ε_brk) and ductility (J), using wide‐angle X‐ray diffraction, transmission electron microscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and tensile and impact tests. RESULTS: Intercalated nanocomposites were formed even in the presence of 16 wt% clay (high loading) in PMMA matrix. PMMA intercalated into the galleries of the organically modified clay, with a change in d‐spacing in the range 11–16 Å. TGA results showed improved thermal stability of the nanocomposites. The glass transition temperature (T_g) of the nanocomposites, from DSC measurements, was 2–3 °C higher than that of PMMA. The ultimate tensile strength and impact strength decreased with increasing clay fraction. Tensile modulus for the nanocomposites increased by a significant amount (113%) at the highest level of clay fraction (16 wt%) studied. CONCLUSION: We show for the first time the formation of intercalated PMMA nanocomposites with alkylammonium‐modified clays at high clay loadings (>15 wt%). Tensile modulus increases linearly with clay fraction, and the enhancement in modulus is significant. A linear correlation between tensile strength and strain‐at‐break is shown. Thermal properties are not affected appreciably. Organoclay can be dispersed well even at high clay fractions to form nanocomposites with superior bulk properties of practical interest. Copyright © 2007 Society of Chemical Industry     

Unsaturated polyester/montmorillonite nanocomposites with improved mechanical and thermal properties fabricated by in situ polymerization

Although organically modified montmorillonite (OMMT) has been incorporated into unsaturated polyester (UP) resin to enhance properties, the aggregation often leads to defects which directly affect the properties of nanocomposites. In this work, OMMT slurry modified by a new allyl surfactant with carbon–carbon double bond, hexadecyl allyl dimethyl ammonium chloride (C₁₆‐DMAAC), was employed to prepare nanocomposites by in situ polymerization. The results illustrated that the existence of OMMT slurry helped monomers enter the OMMT galleries, leading to well‐dispersed OMMT in the UP matrix. The mechanical properties and thermal properties of OMMT nanocomposites were improved. With OMMT loading of 5 wt %, the tensile strength and flexural strength can be improved by 22% and 38%, respectively. Meanwhile, the onset thermal decomposition temperature (T_–10) value was ameliorated from 310.6 °C to 330.6 °C. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45251.     

Epoxidized Mesua ferrea L. seed oil‐plasticized thermostable PVC and PVC‐clay nanocomposites

The use of vegetable‐oil‐based polymeric plasticizers with nanotechnology can create new applications for plasticized poly(vinyl chloride) (PVC). Epoxidized Mesua ferrea L. (Ceylon Ironwood) seed oil was used as a plasticizer for PVC. Further, nanocomposites were prepared through an ex‐situ technique using epoxidized‐oil‐swelled organically modified montmorillonite (5 wt%) and PVC. Notable improvement in thermal and processing characteristics of the nanocomposites was observed over those of the virgin polymer (in both unplasticized and plasticized PVC), as studied by TGA. The prepared nanocomposites were characterized by FTIR, SEM, TEM, and XRD techniques. A dramatic decrease in viscosity (7‐fold) was observed in THF for a 10% solution of epoxidized‐oil‐modified PVC compared to unplasticized PVC in THF, as measured by Brookfield viscometer. Isothermal analysis at three different temperatures (100, 150, and 200°C) reveals sufficient stability of the epoxidized oil modified PVC nanocomposites, as confirmed by gravimetric and FTIR analysis. Augmentation of thermostability and good retention of mechanical properties of the (Mesua ferrea L.)‐plasticized‐PVC/clay nanocomposites with respect to rigid PVC vouch for the utility of the former as advanced industrial materials. J. VINYL ADDIT. TECHNOL., 18:168–177, 2012. © 2012 Society of Plastics Engineers     

Highly filled multilayer thermoplastic/graphene conducting composite structures with high strength and thermal stability for electromagnetic interference shielding applications

Polyvinyl chloride (PVC)/graphene and poly(methyl methacrylate) (PMMA)/graphene nanocomposites were made by solution casting technique with graphene weight fractions of 1, 5, 10, 15, and 20%. Multilayer structures of the composites were made by hot compression technique to study their electromagnetic interference shielding effectiveness (EMI SE). Tensile strength, hardness, and storage modulus of the nanocomposites were studied in relation with graphene weight fraction. There has been a substantial increase in the electrical conductivity and EMI SE of the composites with 15–20% filler loading. Differential thermal analysis of the composites shows improved thermal stability with an increase in graphene loading. PMMA/graphene composites have better thermal stability, whereas PVC/graphene composites have superior mechanical properties. About 2 mm thick multilayer structures of PMMA/graphene and PVC/graphene composites show a maximum EMI SE of 21 dB and 31 dB, respectively, in the X band at 20 wt % graphene loading. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47792.     

Study on BMI modified allyl‐functional novolac resin/silica cloth composites: Effect of allylation degree on thermal and mechanical properties

A series of allyl‐functional novolac resin with various allylation degree, from 32.4 to 114.6%, were synthesized and then blended reactively with 4,4′‐bismaleimide biphenyl methane (BMI) at a weight ratio of 2.50:1 to get BMI‐modified allyl‐functional novolac (BMAN) resins. BMAN resins were used as matrix resin to fabricate BMAN/Silica cloth composites by compression molding process. Heat‐resistant properties of the composites were evaluated by means of dynamic mechanical analysis. The results indicated that thermal resistance of the composites increased as allylation degree of BMAN resins increased. Mechanical properties of the composites, including interlaminar shear strength (ILSS) and flexural strength at room temperature and 300°C, were determined, and the results showed that with increase in allylation degree of matrices the ILSS and flexural strength values of composites at room temperature decreased, but the values of ILSS and flexural strength at 300°C increased. Scanning electron microscope morphology analysis of fracture surface for composites revealed that tough interphase was responsible for the better mechanical properties of the composites based on lower allylation degree resins. POLYM. COMPOS., 28:180–185, 2007. © 2007 Society of Plastics Engineers     

Preparation and characterization of light‐cured methacrylate/montmorillonite nanocomposites

Polymer/clay nanocomposites were prepared from dimethacrylate monomers, commonly used in dental restorative resins, and an organically modified silicate (montmorillonite). The photopolymerization process was hardly affected by the presence of the silicate filler, and thus 2 mm thick samples containing 3 wt% clay were extensively cured. Transmission electron microscopy revealed that the montmorillonite platelets were either intercalated or exfoliated. Nevertheless, for all formulations, intermediate‐sized aggregates of about 1 µm were present and their fraction increased as the amount of filler increased. The presence of the clay was found to have no major effect on the flexural modulus and compressive yield strength of the nanocomposites. Moreover, the water uptake of nanocomposites containing 3 wt% clay was about 10–15% higher than that of unfilled monomers. Modification of the clay surface with alternative organic cations is certainly necessary in order to achieve an optimal dispersion of the clay in the polymer matrix. Copyright © 2010 Society of Chemical Industry     

Effect of melt processing conditions on mechanical properties of polyvinylchloride/organoclay nanocomposites

Abstract

Polyvinylchloride compositions have been prepared by the melt intercalation method using a single screw extruder. Different types of nanofiller based on natural sodium montmorillonite were tested. In particular, intercalating agents containing amine groups combined with co-intercalating agent (low or high molecular weight plasticiser) were examined to determine which is the most suitable not only for producing the largest basal spacing and subsequently the best exfoliation of clay tactoids in polymer matrix, but also for the highest beneficial influence on mechanical properties. In the case of improved exfoliation, the effect of compounding was investigated. Therefore, three values of screw speed were studied and some blends were compounded twice to study the retention time in a single screw extruder and the influence on orientation, dispersion and exfoliation of clay particles in the PVC matrix. Moreover, the effect of different types of plasticiser on mechanical properties was also studied. Bis(2-ethylhexyl) phthalate, Bis(2-ethylhexyl) adipate and Lankroflex epoxy plasticiser were tested. Dynamical thermo-mechanical properties were examined and the tensile properties of thin PVC sheets prepared by calendaring. Using X-ray diffraction and transmission electron microscopy, it was found that partially intercalated and disordered structures arose in polyvinylchloride composites containing sodium montmorillonite, while a fine dispersion of partial exfoliation of individual montmorillonite layers in polyvinylchloride matrix was observed when this clay was organically modified. Finally, the value of the tensile modulus for PVC nanocomposites containing as little as 5 wt-% montmorillonite was increased three times provided that the optimum melt processing conditions were used.     

A facile route for the synthesis of mechanically strong MWCNTs/NDs nanobifiller filled polyacrylate composites

ABSTRACT

We present here the synthesis of novel Nano-Bifiller filled composites with extremely promising material properties. To achieve this goal, initially, poly (methyl methacrylate) (PMMA) and poly (ethylene glycol) (PEG) blend were formed. Later, the matrix was reinforced with purified carbon (P-CNT), amino modified carbon nanotube (PDA-CNT) and amino modified carbon nanotube nanodiamond (PDA-CNT-ND). In this way, three series of nanocomposites, i.e. PMMA/PEG/P-CNT, PMMA/PEG/PDA-CNT, and PMMA/PEG/PDA-CNT-ND were synthesized with varying P-CNT, PDA-CNT and PDA-CNT-ND loading (i.e., 1 wt.%, 3 wt.%, 5 wt.%, 10 wt.%, 30 wt.% and 50 wt.%) by a solution blending route. The reinforcement and loading effect of these three types of nanofillers on the matrix was studied. Studies were performed using Fourier transform infrared spectroscopy (FTIR), mechanical testing, thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM) and X-ray powder diffraction (XRD) to explore the structural, morphological, mechanical and thermal properties of nanocomposites prepared. The inter-association of poly (methyl methacrylate) and poly (ethylene glycol) (PMMA/PEG) due to hydrogen bonding and covalent attachment of matrix to the sidewalls of nanotubes was confirmed by FTIR spectra. The experimental results showed that a loading of 5 wt. % filler in matrix produced a tensile strength and modulus of 26.4 (MPa) and 1255.75 (MPa) in PMMA/PEG/P-CNT nanocomposites, while 28.8 (MPa) and 1411.04 (MPa) in PMMA/PEG/PDA-CNT nanocomposites and 29.4 (MPa) and 1419.41 (MPa) in PMMA/PEG/PDA-CNT-ND nanocomposites as compared to neat PMMA which has tensile strength and modulus of 21.79 (MPa) and 1083.84 (MPa) respectively. These results depict that bifiller nanocomposites showed better mechanical properties as compared to pristine and amine functionalized MWCNT. Scanning electron microscopy revealed granular morphology with few protruding out carbon nanotubes. Thermal stability of PMMA/PEG/PDA-CNT-ND nanocomposites was found higher than PMMA/PEG/PDA-CNT and PMMA/PEG/P-CNT nanocomposites. The T_o (369^°C) and T₁₀ (515^°C) values for PMMA/PEG/PDA-CNT-ND composites was higher than PMMA/PEG/PDA-CNT [T_o (354^°C) and T₁₀ (420^°C)] and PMMA/PEG/P-CNT composites [T_o (312^°C) and T₁₀ (390^°C)]. These results suggest that the bifiller nanocomposites were thermally more stable. The XRD spectra showed a pronounced XRD peak at 25.9^°, corresponding to (002) reflection of the nanotubes indicating that MWCNT structure was not destroyed during composite formation. The peak appeared at 75.3^° were indexed to (220) reflections due to nanodiamond structure.     

Investigation on physicomechanical and wear properties of new green thermoplastic composites

This study was aimed at fabrication of green composites of polypropylene (PP) matrix 5, 10, 15, and 20 wt% of saw palmetto spent (SPS) (a spent of nutraceuticals) as filler material. Two wt% organically modified montmorillonite clay (MMT) was used as a co‐filler in all formulations and composites were fabricated by melt blending. The fabricated PP/SPS/MMT composites were characterized for physicomechanical and tribological properties. Improvement in tensile modulus of the composites was noticed with increase in SPS content. The tensile strength of composites was decreased by 14% with increase in filler content from 5 to 20 wt%. Flexural strength of the composites increased from 31.3 to 37.8 MPa (21% improvement) and also flexural modulus improved from 956 to 1383 MPa (45% improvement) with increased SPS content. Composites were subjected to three‐body abrasion with different loads and abrading distances. Scanning electron microscope (SEM) study revealed that the predominant wear mechanisms of composite material sliding against continuous flowing sand were microploughing and filler detachment from the polymer matrix. POLYM. COMPOS., 37:2306–2312, 2016. © 2015 Society of Plastics Engineers     

Effect of heat treatment on the microstructure and strength of yttrium silicate matrix-modified SiCf/SiC composites

Yttrium silicate was introduced into the matrix of SiC_f/SiC composites via the slurry impregnation and reactive chemical vapor infiltration (RCVI) methods to improve the water and oxygen corrosion resistance of the modified composite materials. The effects of heat treatment on the modified matrix and strength of the composites were systematically investigated. The results showed that the modified matrix was composed of a mixture of yttrium monosilicate, yttrium disilicate, and silicon carbide. The modified yttrium silicate matrix (named Y-Si-O matrix) and the silicon carbide matrix were laminated and well combined. After heat treatment, the amount of Y-Si-O in the mixed matrix increased. The modified composites with yttrium silicate had a similar flexural strength as SiC_f/SiC composites (∼400 MPa). After treated at 1000 °C – 1300 °C, the strength of the modified composites increased by 17 %–26 %. The highest strength was measured for composites treated at 1200 °C.     

Synthesis,fabrication, mechanical,electrical, and moisture absorption study of epoxy polyurethane–jute and epoxy polyurethane–jute–rice/wheat husk composites

Bisphenol‐C‐epoxy‐toluene diisocyanate polyurethane (PEBCT) has been synthesized and used for the fabrication of jute, jute–rice husk (JRH), and jute–wheat husk (JWH) composites. The composites have been fabricated by hand lay‐up technique under a hydraulic pressure of 30.4 MPa at 135°C for 2.5 h. PEBCT‐J, PEBCT‐JRH, and PEBCT‐JWH possess respectively, tensile strength of 37.4, 9.5, and 14.7 MPa, and flexural strength of 39.6, 12.9, and 21.3 MPa, electric strength of 1.3, 1.8, and 1.9 kV/mm and volume resistivity of 1.40 × 10¹³, 1.84 × 10¹³, and 1.91 × 10¹³ ohm cm. Tensile strength and flexural strength have decreased, while electric strength and volume resistivity are improved upon hybridization. PEBCT‐JWH has better interfacial bond strength and stiffness as compared to PEBCT‐JRH. Moisture uptake behavior of PEBCT‐J in water, 10% HCl and 10% NaCl at room temperature is quite different. Equilibrium moisture content of PEBCT‐J in 10% NaCl (5.5%) is almost half of those in water (11.3%) and 10% HCl (13.6%) environments. Equilibrium time for saline environment is also comparatively low. Equilibrium moisture uptake in boiling water has increased 1.84 times, while equilibrium time has decreased 15.3 times. The composites may be useful for low load bearing in construction industries and for marine applications. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Influence of adding Mesocarbon Microbeads into C/C composites on microstructure and properties during carbonization

This work tests the effect on microstructure, flexural strength, flexural moduli, plus the electrical and thermal conductivity of carbon/carbon composites with Mesocarbon Microbeads (MCMBs) content ranging 0–30% by weight during carbonization. These composites were reinforced by oxidative PAN Base fiber felts, and matrix precursor was resol‐type‐phenolic resin. MCMBs with a weight fraction of 0–30% were added to the matrix to elucidate the effect. Liquid‐phase impregnation was applied to reinforce matrix carbon. Cured composites were stabilized at 230°C, then heat‐treated at 400, 600, 800, 900 and 1000°C for carbonization. The measured flexural strength after heat‐treated at 1000°C was 51.20, 49.59, 43.55, and 38.76 MPa for MCMBs with 0, 10, 20, and 30% added to composites; mean flexural moduli were l.73, 1.24, 0.73, and 0.57 MPa, respectively. Adding MCMBs reduced both strength and modulus because of cracks and avoids caused by different shrinkage between resin and MCMBs; adding 30 wt % MCMBs raised thermal conductivity of C/C composites from 1.55 to 1.78 W/mK and reduced electric resistivity from 1.8 × 10^?2 to 5.97 × 10^?3 Ω cm. effect. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3102–3110, 2006     

Poly(methyl methacrylate)/montmorillonite nanocomposites prepared by bulk polymerization and melt compounding

This article focuses on structural, thermal, and mechanical properties of nanocomposites in dependence of preparation method and poly(methyl mathacrylate) (PMMA)/organically modified montmorillonite (OMMT) ratio. PMMA/OMMT nanocomposites were prepared by bulk polymerization and by melt compounding. Properties of nanocomposites of the same composition prepared by the two methods were compared. It was observed that nanocomposites prepared via melt compounding at 200°C had a highly oriented structure with lower interlayer spacing values than nanocomposites prepared via bulk polymerization. Two reasons for the observed smaller interlayer spacing obtained by melt compounding were identified. The first is enhanced PMMA penetration and/or formation between layers in the case of bulk polymerization, which was confirmed by determination of stronger interactions between OMMT and PMMA by Soxhlet extraction, infrared spectroscopy, and differential dynamic calorimery. The second reason for smaller interlayer spacing for nanocomposites prepared by melt compounding is organic modifier degradation during melt compounding process, which was confirmed by thermogravimetric analysis. Both reasons lead to the fracture of melt compounded nanocomposites on the OMMT‐polymer interface, which was observed by scanning electron microscopy. For nanocomposites with disoriented structure and larger interlayer spacing prepared via bulk polymerization the fracture occurred in the polymer matrix. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Polylactide,nanoclay, and core–shell rubber composites

Three types of composites, namely, polylactide (PLA)/nanoclay, PLA/core–shell rubber, and PLA/nanoclay/core–shell rubber, were melt compounded via a corotating twin‐screw extruder. The effects of two types of organically modified montmorillonite nanoclays (i.e., Cloisite®30B and 20A), two types of core (polybutylacrylate)–shell (polymethylmethacrylate) rubbers (i.e., Paraloid EXL2330 and EXL2314), and the combination of nanoclay and rubber on the mechanical and thermal properties of the composites were investigated. According to X‐ray diffraction and transmission electron microscopy analyses, both types of PLA/5 wt% nanoclay composites had an intercalated morphology. In comparison with pure PLA, both types of PLA/5 wt% nanoclay composites had an increased modulus, similar impact strength, slightly reduced tensile strength, and significantly reduced strain at break. On the other hand, PLA/EXL2330 composites with a rubber loading level of 10 wt% or higher had a much higher impact strength and strain at break, but a lower modulus and strength when compared with pure PLA. The simultaneous addition of 5 wt% nanoclay (Cloisite®30B) and 20 wt% EXL2330 resulted in a PLA composite with a 134% increase in impact strength, a 6% increase in strain at break, a similar modulus, and a 28% reduction in tensile strength in comparison with pure PLA. POLYM. ENG. SCI. 46:1419–1427, 2006. © 2006 Society of Plastics Engineers     

表面活性剂和硅烷偶联剂有机复合改性蒙脱土的制备及性能表征

为增加蒙脱土与有机物的相容性,采用十六烷基三甲基溴化铵(CTAB)与硅烷偶联剂(KH-560)对蒙脱土进行了有机复合改性。X-射线衍射和红外光谱的结果表明,CTAB已插入蒙脱土片层,平均层间距离从1.54 nm增大到3.98 nm和2.08 nm,而KH-560未插入蒙脱土片层,只是覆盖在蒙脱土表面,未改变蒙脱土的插层结构;分散性实验表明,表面活性剂和硅烷偶联剂有机复合改性的蒙脱土在苯乙烯、液体石蜡中的分散性好于其他改性蒙脱土;有机复合改性不仅增大了蒙脱土层间距,且改善了蒙脱土与聚氯乙烯的界面效果,提高了蒙脱土在聚氯乙烯基体中的分散均匀性,从而使聚氯乙烯/蒙脱土复合材料玻璃化转变温度的提高和力学性能的改善更明显。     

Preparation and characterization of PVA/OMMT composites

In this study, polyvinyl alcohol/organically modified montmorillonite (HDA/MMT; organoclay) composite was prepared for the intercalation processes. Firstly, the rheological behavior of aqueous montmorillonite dispersions was investigated as a function of solid content. Hexadecylamine (HDA) was added to the montmorillonite dispersion (2%, w/w) in different concentrations in the range of 5 × 10^?4 – 9 × 10^?3 mmol/L. The basal spacing of the organoclay (OMMT) was studied by X‐ray diffraction. The FTIR spectra are obtained from the modified montmorillonite products, which revealed the characteristic absorbencies after treatment with HDA. HDA/MMT/PVA composite, which was produced by the reaction of 1 wt % PVA solution with organoclay complex, is characterized by the rheology, electrokinetic, XRD, FTIR, and SEM techniques. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:2315–2323, 2006     

Modification of a carbon/carbon composite with a thermosetting resin precursor as a matrix by the addition of carbon black

Carbon/carbon composites were made through the pyrolysis of stabilized PAN felt and phenolic resin with the addition of 5 or 10 wt % carbon black to the matrix and then heat treatment at 600–2500°C. The effects of adding carbon black to the matrix precursor on the physical properties, microstructure, and mechanical properties of the resultant composites were investigated. Adding carbon black not only reduced the weight loss but also limited the shrinkage of the resultant composites. Adding carbon black also accelerated the formation of carbon basal planes in the matrix. At 2500°C, the crystalline stacking height in the composite with 10 wt % added carbon black was 200% greater than that with no additive. The flexural strength of the composite also increased from 15 to 42 MPa (almost 300%). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 333–337, 2006     

Rigid PVC/(layered silicate) nanocomposites produced through a novel melt‐blending approach

On the basis of the fusion behavior of poly(vinyl chloride) (PVC), the influence of compounding route on the properties of PVC/(layered silicate) nanocomposites was studied. Four different compounding addition sequences were examined during the melt compounding of PVC with montmorillonite (MMT) clay, including (a) a direct dry mixing of PVC and nanoclay, (b) an addition of nanoclay at compaction, (c) an addition of nanoclay at the onset of fusion, and (d) an addition of nanoclay at equilibrium torque. Both unmodified sodium montmorillonite (Na⁺‐MMT) and organically modified montmorillonite (Org.‐MMT) clays were used, and the effect of the addition sequence of the clay during compounding on its dispersion in the matrix was evaluated by X‐ray diffraction and transmission electron miscroscopy. The surface color change, dynamic mechanical analysis, and flexural and tensile properties of PVC/clay nanocomposites were also studied. The experimental results indicated that both the extent of property improvement and the dispersion of nanoparticles in PVC/(layered silicate) nanocomposites are strongly influenced by the degree of gelation achieved in PVC compounds during processing. The addition of nanoclay to PVC must be accomplished at the onset of fusion, when PVC particles are reduced in size, in order to produce nanocomposites with better nanodispersion and enhanced mechanical properties. Overall, rigid PVC nanocomposites with unmodified clay (Na⁺‐MMT) were more thermally stable and exhibited better mechanical properties than their counterparts with organically modified clay (Org.‐MMT). J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers