L. Boogh

Dendritic hyperbranched polymers as tougheners for epoxy resins

Reference LTC-ARTICLE-1999-002doi:10.1016/S0032-3861(98)00464-9View record in Web of Science URL: http://www.sciencedirect.com/science/journal/00323861 Record created on 2006-06-26, modified on 2016-08-08

A review of dendritic hyperbranched polymer as modifiers in epoxy composites

Dendritic hyperbranched polymers have been shown to be able to double the interlaminar fracture resistance of epoxy-based composites and to reduce the internal stress level by as much as 80% with only 10 phr of modifier. These property improvements were obtained without affecting the viscosity, and thus the processability, nor the glass transition temperature of the epoxy resin. In the investigation, both fully soluble and phase-separating epoxy-functionalised hyperbranched polymers were used, the latter showing more efficient toughening properties. In these blend formulations, however, a close control of the phase separation mechanism was required, in order to avoid filtering effects before or during fibre impregnation. In composite plaques, the phase separation was investigated as a function of fibre surface treatment. In a few cases, a heterogeneous nucleation of modifier particles occurred at the fibre surface as a consequence of favoured fibre/particle interactions. This reduced the fibre/matrix bonding strength and led to adhesive failures at the fibre/matrix interface. In using dendritic hyperbranched polymer modifiers, maximum toughness enhancement and internal stress reduction, were thus obtained when the modifier nucleated within the matrix phase and adhesive failure at the fibre/matrix interface was avoided by selecting suitable fibre surface treatments.

Adhesion of silicon oxide layers on poly(ethylene terephthalate). I: Effect of substrate properties on coating's fragmentation process

Reference LTC-ARTICLE-1997-008View record in Web of Science URL: http://www3.interscience.wiley.com/cgi-bin/jhome/36698 Record created on 2006-06-26, modified on 2016-08-08

Reactive processing of poly(ethylene terephthalate) modified with multifunctional epoxy-based additives

Keywords: poly(ethylene terephthalate) ; epoxy-additives ; reactive processing Reference LTC-ARTICLE-2000-006doi:10.1016/S0032-3861(99)00768-5View record in Web of Science URL: http://www.sciencedirect.com/science/journal/00323861 Record created on 2006-06-26, modified on 2016-08-08

Morphology build-up in dendritic hyperbranched polymer modified epoxy resins: modelling and characterization

The influence of cure temperature, composition and chemical structure on the morphology resulting from chemically induced phase separation has been investigated for different epoxy functionalized dendritic hyperbranched polymers blended with diglycydil bisphenol A and an aliphatic diamine. The cure temperature window chosen highlighted the influence of both the kinetics of phase separation and the thermodynamics of mixing on the final morphology. In relatively immiscible blends and at low cure temperatures, phase separation occurred immediately after mixing. However, increasing the miscibility by raising the temperature or modifying the chemistry of the dendritic hyperbranched polymers resulted in a homogeneous mixture prior to cure, and at low modifier contents, cure induced phase separation was thought to be associated with homogeneous nucleation of modifier rich spherical domains. Complete suppression of the phase separation could be achieved combining the effects of modifier solubility and reaction kinetics, by increasing the catalyst content in the most compatible blends.

Tailored interfacial properties for immiscible polymers by hyperbranched polymers

The influence of hyperbranched polymer grafted polypropylene (PP-HBP) on the interfacial adhesion between fusion bonded bilayers of polypropylene (PP) and polyamide 6 (PA6) and on the properties of PP/PA6 blends was investigated. The interfacial adhesion between PP-HBP compatibilised bilayers was ten times higher compared to maleic anhydride grafted PP (PP-MAH) compatibilised bilayers. This is attributed to the higher diffusitivity and functionality of PP-HBP leading to the formation of more PP-PA6 copolymers at the interface. The elongation at break, epsib, of PP-HBP and PP-MAH compatibilised PP/PA6 blends were measured as a function of compatibiliser concentration. At low compatibiliser concentrations PP-HBP yielded a higher epsib compared to PP-MAH, while at high concentrations similar values of epsib were obtained. The higher values of epsib at low concentrations are explained by the higher functionality of PP-HBP yielding more copolymers and a higher interfacial adhesion. The similar values obtained at high concentrations show that similar properties are achieved for copolymer saturation at the interface using either compatibiliser. The high diffusitivity of PP-HBP is an asset for multilayer film extrusion, while for blends, the high functionality permits the use of less compatibiliser for similar property improvements.

Influence of hyperbranched polymers on the interfacial tension of polypropylene/polyamide-6 blends

Keywords: hyperbranched dendritic polymers ; interfacial tension ; blends ; compatibilization Reference LTC-ARTICLE-1999-004View record in Web of Science URL: http://www3.interscience.wiley.com/cgi-bin/jhome/36698 Record created on 2006-06-26, modified on 2016-08-08

Chemically induced phase separated morphologies in epoxy resin-hyperbranched polymer blends

Reference LTC-ARTICLE-2000-012View record in Web of Science Record created on 2006-06-26, modified on 2016-08-08

Matrix Modification for Improved Reinforcement Effectiveness in Polypropylene/Glass Fibre Composites

The influence of matrix modification on the interfacial shear strength (IFSS) and the mechanical performance of polypropylene/glass fibre composites is investigated. Two different modifiers were used: a highly reactive hyperbranched polymer grafted polypropylene (HBPgPP) and a maleic anhydride grafted polypropylene (MAHgPP). The interfacial shear strength increased with the addition of the modifiers, with HBPgPP giving the highest values. To evaluate the effects of the matrix modification on the composite strength, a method to normalise the composite strength with respect to fibre orientation and fibre concentration is presented. The normalised strength values followed the same trend as the measured IFSS values, namely that the HBPgPP modified composite displayed the highest strength and the unmodified material the lowest.