A review of dendritic hyperbranched polymer as modifiers in epoxy composites

• Published in: Composites science and technology Vol. 61; no. 5; pp. 787 - 795
• Main Authors: Mezzenga, Raffaele, Boogh, Louis, Månson, Jan-Anders E.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.04.2001; Elsevier
• Subjects: A. Dendritic hyperbranched polymers, toughness; A. Surface treatment; Applied sciences; C. Residual stress; Exact sciences and technology; Forms of application and semi-finished materials; Laminates; Polymer industry, paints, wood; Technology of polymers; A. Surface treatment; C. Residual stress; A. Dendritic hyperbranched polymers, toughness; Strengthening; Polyfunctional compound; Branched polymer; Laminate; Fiber reinforced material; Mechanical properties; Epoxy resin; Tensile property; Experimental study; Transfer molding; Property processing relationship; Composite material; Surface treatment; Matrix fiber interface; Glass fiber; Carbon fiber; Modified material
• ISSN: 0266-3538; 1879-1050
• DOI: 10.1016/S0266-3538(01)00022-7

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.