The intercalation of poly(methyl methacrylate)/aluminophosphate nanocomposites and the properties improvement

Poly(methyl methacrylate) (PMMA)/dodecylamine templated lamellar aluminophosphate (DDA-LAP) intercalated nanocomposites are prepared by in situ bulk polymerization of MMA. The intercalated structure is characterized. With the intercalation of DDA-LAP in PMMA matrix, the glass-transition temperatures of nanocomposites (T_g) are increased. The nanocomposites obtained keep relatively high transparency in optical property and have a significant improvement in mechanical properties and thermal stability. The mechanism for the properties enhancement is investigated. The strong interfacial interaction between the aluminophosphate layers and the PMMA chains, the homogeneously distribution and the graphitized char formation during heating are three key roles for the properties improvement.     

Synthesis and characterization of nitrated and aminated poly(phenylene sulfide) derivatives for advanced applications

Nitrated and aminated poly(phenylene sulfide) (PPS) derivatives with different extent of modification were synthesized in a one-pot reaction in suspension. Their substitution degree was determined from both elemental analysis and TGA curves. FT-IR and NMR spectra demonstrated the effectiveness of the functionalization reactions, showing the appearance of bands related to the substituent groups. A progressive reduction in thermal stability was observed as the number of functional groups increased. Aminated derivatives were thermally less stable and exhibited higher solubility in aprotic polar solvents than the corresponding nitrated polymers. DSC thermograms revealed a diminution in the crystallization temperature and a rise in the glass transition with increasing functionalization degree, since the presence of substituent groups inhibits the rotation of consecutive elements of the polymer chain. The level of crystallinity decreased upon increasing chain modification, as evidenced from X-ray diffractograms. The steric hindrance of the substituents disrupts the chain packing, leading to smaller crystals. These derivatives are expected to have applications in electromembranes and as matrix materials for the fabrication of high-performance composites suitable for structural and non-structural components.     

Preparation and characterization of novel biodegradable composites based on acylated cellulose fibers and poly(ethylene sebacate)

The preparation and characterization of biodegradable composite materials with improved properties based on poly(ethylene sebacate) (PES) and acylated cellulose fibers is reported. These biocomposites showed improved mechanical properties, as evidenced by the increase in both elastic and Young moduli and in the tensile strength, and also showed low water sensitivity and a high biodegradability rate. These novel biocomposites were prepared essentially from renewable resources and therefore constitute an important contribution to the development of the area of sustainable composite materials.     

Influence of highly branched poly(amido amine) on the properties of hyperbranched polyurethane/clay nanocomposites

The fascinating architecture of hyperbranched polymer imparts a truck load of novel properties to the material. Epoxy resin modified Mesua ferrea L. seed oil based hyperbranched polyurethane (MHBPU) nanocomposites were prepared by in situ technique using s-triazine based highly branched poly(amido amine) (HBPAA) modified organo-nanoclay. The HBPAA was synthesized by A₂ + B₃ technique with good yield (>75%) using urea and s-triazine. The formation of the polymer was confirmed with the help of ¹H NMR, FTIR, UV spectroscopic, and measurements of solution viscosity with other physical properties. This HBPAA was successfully utilized to swell the montmorillonite organo-nanoclay as the interlayer gallery distance increases up to 8.2 Å, obtained by XRD study. The FTIR further confirmed the presence of interactions of the HBPAA moiety with the organo-clay layers. The formation of nanocomposites was confirmed by FTIR, XRD, SEM, TEM and rheological studies. The improvements of tensile strength (1.7 times) and scratch hardness (2.3 times) along with the dramatic enhancement of thermostability and flame retardancy without compromising impact resistance, bending, and elongation at break of the nanocomposites compared to pristine MHBPU thermoset are the noticeable credits of the present investigation. The results signify the great potential of the studied materials for various advanced applications.     

Influence of single-walled carbon nanotubes on the effective elastic constants of poly(ethylene terephthalate)

Poly(ethylene terephthalate) (PET) is one of the most extensively used thermoplastic polyesters out on the market, and it has been implemented in many forms. There has been limited work in the area of PET reinforced with single-walled carbon nanotubes (SWCNT) in mechanical properties. Nanocomposites based on PET with small contents of SWCNT were prepared by in situ polymerization. Elastic constants were determined by tensile tests performed on specimens instrumented with strain gauges. Assuming random orientation distribution of nanotubes, experimental Young’s modulus and Poisson’s ratio values were compared to some micromechanical models (Cox and Krenchel, Halpin–Tsai and Mori–Tanaka) which take into account orientation and aspect ratio of the nanotubes. However, the waviness of the nanotubes is a factor that influences the reinforcing efficiency.     

Synthesis and properties of poly(hexamethylene terephthalate)/multiwall carbon nanotubes nanocomposites

Poly(hexamethylene terephthalate) (PHT)/carbon nanotubes (CNT) nanocomposites containing 1% and 3% (w/w) of filler were prepared by two procedures: in situ ring-opening polymerization of hexamethylene terephthalate cyclic oligomers in the presence of CNT and melt blending of PHT/CNT mixtures. Arc discharge multiwalled carbon nanotubes, both pristine (MWCNT) and hydroxyl functionalized (MWCNT-OH), were used. The objective was to evaluate the effect of preparation procedure, nanotube side-wall functionalization and amount of nanotube loaded on properties of PHT. All nanocomposites showed an efficient distribution of the carbon nanotubes within the PHT matrix but interfacial adhesion and reinforcement effect was dependent on both functionalization and nanotubes loading. Significant differences in thermal stability and mechanical properties ascribable to functionalization and processing were observed among the prepared nanocomposites. All the prepared nanocomposites showed enhanced crystallizability due to CNT nucleating effects although changes in melting and glass transition temperatures were not significant.     

Morphology and properties of microfibrillar composites based on recycled poly (ethylene terephthalate) and high density polyethylene

Microfibrillar composites (MFCs) from recycled high density polyethylene (R-HDPE)/recycled poly (ethylene terephthalate) (R-PET) (75/25 w/w) were made through reactive extrusion and post-extrusion strand stretching. The resultant MFCs could be processed at HDPE processing temperature. The compatibility between microfibers and R-HDPE matrix was improved through compatibilizers. Of the three compatibilizers evaluated, ethylene glycidyl methacrylate copolymer (E–GMA) performed the best. The addition of compatibilizers did not obviously change the size of R-PET fibers in MFCs. The toughness of MFC was significantly enhanced, and R-PET phase did not crystallize when 5% E–GMA was used. The process of manufacturing MFCs provides a way to recycle commingled plastics, and MFCs would be potential matrices for natural fiber polymer composites.     

Supermolecular structure and thermal properties of poly(ethylene terephthalate)/lignin composites

Poly(ethylene terephthalate) (PET) has been compounded with lignin (L) by a single-screw extruder. The influence of L presence and its content on the thermal properties and crystalline structure of PET has been studied. Morphological analyses evidenced good dispersion of the L particles in the PET matrix. Polarizing optical microscopy (POM) and small-angle X-ray scattering (SAXS) techniques were employed to measure the L particles dimension. The influence of L on the overall isothermal crystallization of PET was investigated by using differential scanning calorimetry (DSC). L particles acting as nucleating agent in the composite increased the crystallization rate. The crystallization process was composed of primary and secondary stages. As the L content was increased in the composite, the primary crystallization progressively proceeded toward higher percentage of the crystallizable PET fraction. As evidenced by SAXS and wide angle X-ray diffraction (WAXD), the L presence produced a noticeable enhancement of PET crystallinity and crystal dimensions.     

The effect of hygrothermal conditions on the fracture toughness of epoxy/poly(styrene-co-allylalcohol) blends

The influence of water content on the fracture toughness of epoxy/poly(styrene-co-allylalcohol) (PScoPA) blends with different amounts of modifier has been investigated. The water ingress has a double consequence: a considerable plasticization effect of the matrix and a significant weakening of the interphase between the matrix and the thermoplastic particles. The addition of thermoplastic modifier reduces, in the aged samples, the deterioration in fracture toughness. Analytical models, based on plastic voids growth around the dispersed phase particles, have been applied with reasonable agreement.     

Dielectric properties of montmorillonite clay filled poly(vinyl alcohol)/poly(ethylene oxide) blend nanocomposites

Organic–inorganic nanocomposites of poly(vinyl alcohol) (PVA)–poly(ethylene oxide) (PEO) blend filled with montmorillonite (MMT) nanoclay up to 10 wt.% concentration were synthesized by aqueous solution-cast technique. The complex dielectric function, electrical conductivity, electric modulus and impedance spectra of the nanocomposites were measured in the frequency range 20 Hz–1 MHz at ambient temperature. A direct correlation was observed between the real part of dielectric function and the mean relaxation time of the polymer chain segmental dynamics, with the exfoliated and intercalated MMT clay structures, and the extent of miscibility between PVA and PEO due to hydrogen bonded bridging through exfoliated MMT clay nanosheets. The large increase of dielectric relaxation time revealed that the dispersed exfoliated nanoscale MMT clay in the polymers blend matrix produces a large hindrance to the polymer chain dynamics. Results confirm that the real part of dielectric function of the nanocomposites can be tailored by varying amount of MMT clay filler for their use as nanodielectric materials in the microelectronic technology.     

Effects of carbon nanotube functionalization and annealing on crystallization and mechanical properties of melt-spun carbon nanotubes/poly(ethylene terephthalate) fibers

To generate poly(ethylene terephthalate) (PET) fibers with enhanced mechanical properties, we prepared melt-spun PET fibers that incorporated pristine, acid-treated, and functionalized multi-walled carbon nanotubes (MWNTs) with 2-phenylethyl alcohol and 4-phenyl-1-butanol. The incorporation of MWNTs into the melt-spun fibers resulted in increased crystallization of PET but lower breaking stress than that of pure PET fibers, even in those containing well-dispersed functionalized MWNTs. The breaking stress of drawn composite fibers was also lower than that of pure PET fibers prepared at the same draw ratio. However, the annealing of melt-spun fibers enhanced the mechanical properties and crystallization, and the annealing effect was more dominant for composite fibers with functionalized MWNTs. These findings indicate that the presence of well-dispersed MWNTs disturbs the crystallization and orientation of PET molecules in highly stressed fibers, which differs from MWNT-induced crystallization of PET molecules in relaxed fibers.     

紫外辐射对聚酯纤维结构与性能的影响

为了延长暴露于大气环境下聚酯纤维材料的使用周期,研究紫外辐射对聚酯纤维材料结构影响,以填充消光剂、纳米紫外线屏蔽剂等方法来合成聚酯复合纤维材料.通过差示扫描量热仪(DSC)、动态热机械分析仪(DMA)以及分子量测定研究了不同紫外辐射周期对聚酯纤维分子量、机械性质、微观结构等影响.研究结果表明,紫外辐射后的聚酯纤维样品的分子量、强伸度大幅度下降,结晶度有所提高,玻璃化转变温度、熔点均有所降低.而聚酯复合纤维材料的抗辐射效果较聚酯纤维有所改善.消光剂、纳米级紫外线屏蔽剂对辐射过程中的聚酯纤维样品起到了明显的稳定作用,其中纳米紫外线屏蔽剂具有更好的效果.     

Effect of the molecular weight of poly(ethylene glycol) on the plasticization of green sheets composed of ultrafine BaTiO3 particles and poly(vinyl butyral)

The effect of the molecular weight (MW) of poly(ethylene glycol) (PEG) on the plasticization of poly(vinyl butyral) (PVB) binder in green BaTiO₃ sheets prepared with PEG with MW values of 400 and 1530 was investigated. The MW of PEG had a profound effect on the rheological properties of the suspension as well as the physical properties of the green sheet. The suspension viscosity decreased with decreasing MW of PEG for shear rates above 4 s⁻¹. PEG 400 gave rise to a higher degree of plasticization of the green sheet than PEG 1530. This was due to the reduction in hydrogen bonding between the vinyl alcohol units in the PVB binder in the green BaTiO₃ sheet, as identified by FT-IR spectroscopy. As the MW of the PEG decreased, the green BaTiO₃ sheets exhibited a lower glass transition temperature, and a noticeably more ductile behavior. These results indicate that the green sheets became more flexible due to a higher plasticizing effect. However, laminated green BaTiO₃ sheets prepared with PEG 1530 showed delamination defects that were observed at a cut surface, which arose because of the low plasticization. This suggests that PEG 1530 has limited utilization as a plasticizer for the BaTiO₃/PVB binder system.     

Synthesis and properties of novel photosensitive poly(arylene ether sulfone) containing chalcone moiety in the main chain

A new series of photosensitive poly(arylene ether sulfone)s containing chalcone moiety in the main chain were synthesized from 4,4′-dihydroxychalcone (4DHC), 4,4′-difluorodiphenylsulfone (DFDPS) and bisphenol A (BPA). This series of polymers were characterized by ¹H NMR, FT-IR, UV spectroscopy, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The polymers were stable up to 400 °C, which indicates that the polymers possess good thermal properties. The polymers were found to be soluble in polar solvents and chlorinated solvents. However, the polymers were insoluble in hydrocarbons and in hydroxyl group-containing solvents. After the irradiation of UV light, the thin polymer film was crosslinked to give an insoluble film in the absence of a photoinitiator or sensitizers. The rate of photocrosslinking was also examined and discussed.     

Stiffening of poly(ethylene terephthalate) by means of polyamide 6 nanocomposite fibers produced during processing

Polymer nanocomposites based on poly(ethylene terephthalate) (PET) with up to 40% polyamide 6 (PA6) reinforced with up to 7% of a fully dispersed organoclay were obtained in the melt state presenting a highly fibrillar morphology of the dispersed phase. The organoclay was located in the dispersed PA6 phase, as was expected given the nature of the chemical modification of the organoclay and the mixing procedure selected. Fibrillation was possible thanks to the presence of some PA6 in the PET-rich phase which assured compatibility and allowed the development of these high surface/volume ratio structures. The increases obtained in the elasticity modulus were higher than any previously observed in PET matrix Ncs. This indicated that the location of the organoclay in the dispersed fibrillated phase was more effective in terms of stiffening than a location in the matrix.     

9,10-Diphenylanthracene-containing poly(arylene ether sulfone)s with improved glass transition temperature and photocrosslinking properties

In this study, novel poly(arylene ether sulfone)s containing 9,10-diphenylanthracene units were synthesized and their thermal and optical properties were investigated. This new bisphenol monomer, 9,10-bis(4-hydroxyphenyl)anthracene, was facially synthesized in two steps and showed similar reactivity for SNAr reactions as other bisphenol monomers, such as bisphenol A. The introduction of an anthracene unit to poly(arylene ether sulfone)s can obviously improve glass transition temperature and retain good solubility and high decomposition temperatures. The glass transition temperature of poly(arylene ether sulfone) reached up to 265 °C when the bisphenol A was entirely substituted by bis(4-hydroxyphenol)anthracene. These polymers are soluble in chloroform, N,N-dimethylformamide and N-methyl-2-pyrrolodone and can be film-formed through spin-coating. Interestingly, anthracene units endowed these polymers with photocrosslinkable properties and further improved their thermal stability.     

Structural characteristics and thermal properties of plasticized poly(l-lactide)-silica nanocomposites synthesized by sol-gel method

Plasticized poly(l-lactide)-silica nanocomposite materials have been successfully synthesized by sol-gel process. The resultant nanocomposites were characterized by infrared spectra (IR), X-ray diffraction (XRD), thermogravimetry (TG), Tensile testing and scanning electron microscope (SEM). IR measurements show that vibration of C-O-C group is confined by silica network. Also the crystallization of poly(l-lactide) is partly confined by silica network. The presence of even small amount of silica largely improves the tensile strength of the samples. TGA results reveal that the thermal stability of samples is improved with silica loading.     

Ternary nano-CaCO3/poly(ethylene terephthalate) fiber/polypropylene composites: Increased impact strength and reinforcing mechanism

The binary nano-CaCO₃/polypropylene (PP), poly(ethylene terephthalate) (PET) fibers/PP and ternary nano-CaCO₃/PET fibers/polypropylene composites were prepared by melt blending method, and their structure and mechanical properties were investigated. The results show that the ternary nano-CaCO₃/PET fibers/PP composite displays significantly enhanced mechanical properties compared with the binary PET fibers/PP and nano-CaCO₃/PP composites, and neat PP. The X-ray diffraction, dynamic mechanical analysis, scanning electron microscopy and analysis of the non-isothermal crystallization kinetics were used to investigate the reinforcement mechanism of composites. The results indicate that the interfacial action and compatibility between PET fiber and PP are obviously enhanced by the addition of modified nano-CaCO₃ particles in the ternary composites and the mechanical property enhancement in the ternary system may be mainly originated from the formation of β-form crystallites of PP induced by the synergistic effect between PET fibers and nano-CaCO_3.     

The effect of bagasse fibers obtained (from rind and pith component) on the properties of unsaturated polyester composites

In the present study, two major component of bagasse, namely rind (outer part) and pith (inner part) were used as reinforcement in unsaturated polyester (USP) composites. The bagasse fiber filled USP composites were produced by vacuum bagging method and the volume percentage of fiber was varied at 0%, 5%, 10% and 15%. Characterizations such as flexural, impact and water absorption were carried out to measure the properties of the composites. Based on the result, it was found that the rind fiber composites produced higher flexural and impact properties, and lowered water absorption rate compared to inner fiber composite. In short, the flexural, impact and water absorption properties of bagasse composites are governed by the two major component of bagasse; rind and pith.