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Polymers and Polymer Composites

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Title: HIGH YIELD SYNTHESIS OF FLUORINATED BENZOXAZINE MONOMERS AND THEIR MOLECULAR CHARACTERIZATION
Page Range: p.191-204
Author(s): Liu J; Ishida H
File size: 142K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 10
Issue No: No. 3

Abstract
The synthesis is reported of previously unknown 3,4-dihydro-3-fluorophenyl-2H-1,3-benzoxazines by the reactions of formaldehyde and bisphenol-A with penta-,tri-, di-, and mono-fluoroaniline, under neutral or acidic conditions. This fluorinated benzoxazine monomer has been developed as a potential precursor for a polybenzoxazine in electronic applications, where its advantages in terms of low dielectric constant, low flammability, low refractive index, low coefficient of friction and high Tg temperature will be used. It is found that the pH value of the reaction medium is the controlling factor in the yield of the compound from weak amines, and that a strongly acidic condition is necessary for the synthesis of similar compounds from other very weak amines. The effects of solvents are discussed. 26 refs.

Title: EFFECTS OF FIBER LENGTH AND SPATIAL DISTRIBUTION ON THE STIFFNESS OF SHORT-FIBER REINFORCED COMPOSITES
Page Range: p.205-210
Author(s): Juhlin E; Chen X; Papathanasiou T D
File size: 107K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 10
Issue No: No. 3

Abstract
The results are reported of a computational investigation of the effect of fibre aspect ratio on the stiffness of composite rods reinforced with rigid spheroidal inclusions. Steady-state three-dimensional deformations of composite rods containing up to 50 individual, randomly placed aligned spheroids are considered. Solution of the equations of elasticity for the entire 3D domain yields an effective tensile modulus for the composite rod. Statistical averages of the computed effective moduli are compared to the predictions of the Mori-Tanaka model for the stiffness of the short fibre composites. In addition, the effect is investigated on stiffness of random perturbations in fibre length around a mean value. 15 refs.

Title: EFFECT OF HEAT TREATMENT ON THE FRACTURE TOUGHNESS OF GLASS FIBRE REINFORCED POLYPROPYLENE
Page Range: p.211-218
Author(s): Lin J-S; Wu S-K
File size: 114K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 10
Issue No: No. 3

Abstract
The effect is examined of heat treatment on the fracture toughness of glass fibre reinforced polypropylene. PP blended with short glass fibres was injection moulded and heat treated at 150 degrees C for 30 minutes. The crack growth resistance curve was measured to evaluate the effect of heat treatment on the fracture toughness, and to determine the stress intensity factor at the point of instability. The fracture surface was examined using scanning electron microscopy to analyse the fracture mechanism. By measuring the critical fibre length, it is observed that heat treatment changes the fibre-matrix interfacial shear strength and hence affects the mechanical properties of FRP. 28 refs.

Title: DIELECTRIC PROPERTIES OF POLYMERS FILLED WITH DISPERSED METALS
Page Range: p.219-228
Author(s): Mamunya Y P; Davydenko V V; Zois H; Apekis L; Snarskii A A; Slipchenko K V
File size: 195K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 10
Issue No: No. 3

Abstract
The dielectric properties are studied of composite materials based on PVC and epoxy resin filled with copper or nickel of various particle sizes and shapes. In addition, two types of particle distribution, random and segregated were produced for composites filled with nickel. The effect of the above factors on the dielectric properties of the composites was studied. The concentration dependence of the dielectric parameters is said to demonstrate a critical behaviour in the percolation threshold region, and the dependence of the dielectric parameters on concentration follows power-law behaviour. A model for the structure which explains the behaviour, is proposed. 26 refs.

Title: IMPROVED STORAGE STABILITY OF LDPE/SBS BLENDS MODIFIED ASPHALTS
Page Range: p.229-236
Author(s): Gao G; Zhang Y; Zhang Y; Sun K; Fan Y
File size: 115K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 10
Issue No: No. 3

Abstract
Phase separation has been a major obstacle to the widespread use of polymer-modified asphalt in road surfacing, and to provide a solution to the problem of storage-stable polymer modified asphalts, blends of SBS and LDPE are mixed under high shear stress, and added with sulphur to the asphalt under high speed mixing. Compared to the asphalts modified by LDPE and SBS added directly, the blend modified asphalts showed better storage stability in the presence of sulphur at high temperature, with no visible phase separation or evidence of coalescence. The rheological properties of the asphalts were also improved by the addition of polymers in all cases. 18 refs.

Title: CURE BEHAVIOUR AND STRUCTURE OF DICYANATE-EPOXY NOVOLAC BLENDS
Page Range: p.237-248
Author(s): Guo B; Fu W; Jia D; Qiu Q; Wang L
File size: 227K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 10
Issue No: No. 3

Abstract
The objectives of this work are to investigate the cure behaviour and structure of bisphenol A dicyanate-novolac epoxy blends. The cure characteristics were investigated by gel time determination and dynamic DSC. To disclose the structural differences between cured cyanate-novolac epoxy blends and more traditional cyanate-diglycidyl ether systems, FTIR investigations were performed on the two kinds of blends, and in situ FTIR was used to examine the Bauer mechanism. The effects of epoxy concentration in the blend on the cure kinetics was investigated using two blends with different molar ratios, and in situ FTIR. 33 refs.

Title: IMPROVEMENT OF THE FRACTURE BEHAVIOUR OF POLYBUTYLENETEREPHTHALATE MODIFIED BY HIGHLY DISPERSED METALS
Page Range: p.249-256
Author(s): Ozden S; Borukayev T A; Mashukov N I; Mikitayev A K
File size: 81K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 10
Issue No: No. 3

Abstract
The failure mechanism of PBTP was improved by the addition of highly dispersed iron/iron oxide to the polymer. The mechanical behaviour of the materials under impact was investigated, and the addition of highly dispersed iron particles was shown to stabilise the failure mechanism of PBTP and improve its mechanical properties. This was attributed to increased interphases between crystalline and amorphous phases, decreased crystalline size, increased network entanglement density and decreased critical structural defect length. 14 refs.

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