Plastics,Rubber and Composites: Macromolecular Engineering

Ni particles supported on carbon nanotubes (CNTs) were dispersed in a polymethyl methacrylate (PMMA) matrix by solution blending and then cast onto an electrode to get composite films under low magnetic fields. The orientation of CNTs in the films was characterised by scanning electron microscope and optical microscope. Multimeter and high resistance meter were used to study the electrical behaviour of the nanocomposites. The glass transition temperature T _g of PMMA was determined by differential scanning calorimetry. The results show that the alignment of the CNTs dispersed in the PMMA was achieved under a low magnetic strength below 0·5 T. Because of the ferromagnetism of Ni particles, the magnetic alignment of CNTs susceptibly changed. The magnetic alignment units in this work were rod-like CNTs aggregates instead of single CNTs, which took part in the buildup of a specific CNTs network structure in PMMA matrix. The network structure played a key role in significantly improving electrical conductivity and T _g of the nanocomposites.

Acrylonitrile–butadiene–styrene (ABS)/montmorillonite (MMT) nanocomposite was prepared by melt blending of ABS and organomodified montmorillonite (OMMT). X-ray diffraction, TEM and Fourier transform infrared spectra were used to characterise the morphology and structure of the nanocomposites. Thermal stability and flame retardancy of the nanocomposites were studied by thermogravimetric analysis, cone calorimetry, limit oxygen index and UL94 test. The basal spacing of sodium MMT was found to increase from 1·46 to 2·69 nm after modification by cetyltrimethyl ammonium bromide, and ∼3·3 nm after melt blending with ABS. Transmission electron microscope observation showed that organo-MMT was intercalated and exfoliated in ABS. The results by cone calorimetry analysis indicated that the reduction of the peak heat release rate of ABS/OMMT nanocomposites (with 5% OMMT loading) and ABS/OMMT/triphenyl phosphate (TPP) nanocomposites (with 4% OMMT and 10% TPP loading) was 47·3 and 57·3% respectively, while the total heat released decreased by about 10 and 17% and the mass loss rate decreased by about 41 and 53% respectively, as compared with pristine ABS. Limit oxygen index value of ABS/OMMT and ABS/OMMT/TPP nanocomposites increased to 22·8 and 28% from 18% of pristine ABS respectively. The vertical burning test (UL-94V) results revealed that the nanocomposites could achieve V-0 grade.

In order to enhance the bonding force of sisal fibres (SF) and polymer matrix, different surface modifiers (alkali, coupling agent and borax) were used to treat the fibres. The SF/phenol formaldehyde (PF) resin composites were prepared through compression moulding. Thermal properties of the treated SFs and fibre composites were studied by thermogravimetric analysis and thermal expansion analysis. The effect of SF modification on the friction and wear properties of composites was investigated using wear tester under dry condition. The treated fibre surface and the worn surfaces of SF/PF composites were observed by SEM. The results showed that the surface of SF became rough after borax treatment, and the initial decomposition temperature increased by 13·6°C, compared to untreated SF. Thermal stability and wear properties of the PF composites with treated fibre were obviously increased due to the fibre modification. For example, wear volume of the composites with sisal treated by borax decreased by 73·3%. Scanning electron microscopy photos showed that the wear mechanism changed from fatigue wear to slight plough wear.

A novel liquid crystalline epoxy resin, PHQEP, containing aromatic ester mesogen was synthesised from di(p-hydroxyl benzoic acid) hydroquinone (PHQ) and epichlorohydrin by phase transfer catalysis. The molecular structure of PHQEP was characterised by means of Fourier transformed infrared spectroscopy, hydrogen nuclear magnetic resonance spectroscopy, while its liquid crystalline phase behaviour was observed by a polarised optical microscope. The curing behaviour of PHQEP/diglycidylether of bisphenol A (E-51)/4,4′-diaminodiphenyl sulphone (DDS) system was studied by non-isothermal differential scanning calorimetry. Mechanical performance, thermal stability and dynamic mechanical property of PHQEP/E-51 composites were also investigated. The results revealed that PHQEP is a typical nematic liquid crystalline polymer. Impact strength of 5 wt-% PHQEP/E-51 was 2·6 times higher than that of E-51/DDS, and the initial decomposition temperature was 10°C higher than the value of E-51/DDS. The detailed reasons for the improvement of strength and thermal stability lie in the fact that origination of the mesogenic units of PHQEP was kept in the epoxy networks during the curing process.

An industrial calcium carbonate (CaCO₃) filler of large particle size was modified with polystyrene (PS) by in situ emulsion polymerisation of styrene. The structure, morphology and thermal stability of the PS/CaCO₃ composite were characterised by Fourier transform infrared spectrograph, scanning electron microscope and thermogravimetric analysis, respectively. The effects of St/CaCO₃ ratio and particle size of CaCO₃ on the encapsulation ratio of the CaCO₃ and the viscosity of the composite in organic solvent were investigated to obtain maximal modification. The results showed that PS had covered the CaCO₃ particles, which changed the surface of CaCO₃ particles from hydrophilic to hydrophobic. The maximal decomposition temperature of the extracted PS/CaCO₃ composite was increased by 17°C in comparison to pure PS. The viscosity of CaCO₃ particles in organic solvent decreased greatly, indicating that the effect of modification was very significant. The large size of the CaCO₃ particle exhibited high encapsulation ratio.

An oil soluble monomer, glycidyl methacrylate, which contains an epoxy group, was grafted onto poly(vinylidene fluoride) (PVDF) powder via pre-irradiation induced graft polymerisation in water under shear dispersion without additives. The existence of graft chains was proven by Fourier transform infrared spectroscopy, and the epoxy groups in graft chains are ready for further chemical modification. Graft polymerisation kinetic was studied, and the results showed high monomer conversion, which exceeded 70%. Microfiltration membranes were cast from grafted PVDF powder via phase inversion method, and the morphology of those microfiltration membranes was investigated by scanning electron microscopy. The images of the membrane cast from grafted powder revealed similar asymmetric morphology to the membrane cast from pristine PVDF powder.

In this paper, the kinetics of poly(ethylene glycol) monomethacrylate (PEGMA) grafted from Si(100) surface to generate poly(poly(ethylene glycol) monomethacrylate) [P(PEGMA)] polymer brush was investigated. A covalently bonded (Si-C bonded) 4-vinyl benzyl chloride (VBC) monolayer (Si-VBC surface) was formed via UV induced coupling of the vinyl group of VBC with the Si-H surface. Then, PEGMA was grafted from Si(100) surface via surface initiated atom transfer radical polymerisation with the aid of the monolayer VBC. The modified silicon surfaces were characterised by X-ray photoelectron spectroscopy, ellipsometry and telescopic goniometre. The presence of grafted P(PEGMA) on the Si-VBC surface was confirmed by X-ray photoelectron spectroscopy and ellipsometry measurements. The results suggested that the chain growth from Si-VBC surface is consistent with a ‘controlled' or ‘living' process.

Scanning electron microscopy was used to observe the microstructures of a cork wood. It showed that the wood consists of countless rectangular and honeycomb wood cells. The wall of each wood cell connects with adjacent wood cells at the middle of the cell wall. More careful observation showed that the walls of the wood cells are a kind of fibre reinforced biocomposite consisting of crystalline cellulose fibre layers and hydrocarbonated polymer matrix. The crystalline cellulose fibres in different fibre layers possess different directions, which compose a kind of fibre helicoidal microstructure. In the microstructure, the helicoidal angle is very large. The maximum pullout force of the fibre helicoidal microstructure, which is closely related to the fracture toughness of the wood, was theoretically and experimentally investigated and compared with that of the fibre parallel microstructure. It showed that the maximum pullout force of the fibre helicoidal microstructure is markedly greater than that of the fibre parallel microstructure and that the larger the helicoidal angle, the more the maximum pullout force will increase compared with that of the parallel microstructure.

The multilayered biaxial weft knitted (MBWK) fabric made of E-glass fibres and stitched with polyester yarns, which is a kind of non-crimp fabrics, has been impregnated with epoxy via resin film infusion technique to manufacture the composite plates. The tensile properties of the MBWK fabric reinforced composite are studied with the multidirectional tensile testing. The classical lamination theory is applied to evaluate both the tensile modulus and Poisson's ratio, which shows good agreements with the experimental results. Failure analyses are also available by means of sample debris examination to identify the failure modes and the scanning electron microscope to reveal the microscopic mechanism. Predictions of the tensile properties provide a way to estimate the mechanical behaviours of the MBWK composite structures. Elongation at break is independent of the testing directions, which can be used as the failure criterion of the composite.

A detailed numerical investigation has been carried out to investigate the effect of local fibre array irregularities on microscopic interfacial normal stress for transversely loaded unidirectional carbon fibre/epoxy composites with random fibre arrangement. Linear elastic finite element analyses were carried out for a two-dimensional image based model composed of 70 fibres. One fibre in this image based model is replaced with resin as the resin equivalent fibre, and the resulting change in microscopic interfacial normal stress distribution is investigated. Three fibres are selected for the resin equivalent fibres to clarify the individual local geometrical irregularity. Calculations were carried out for three loading conditions: case A, cooling of –155 K from the curing temperature; case B, transverse loading of 75 MPa chosen as an example of macroscopic transverse fracture strength and case C, both cooling from the curing temperature and transverse loading of 75 MPa. The effect of fibre array irregularities on the interfacial stress state is limited to the region between the resin equivalent fibre and its first neighbouring fibres. The contribution of the second neighbouring fibre is small and that of further fibres is negligible.