Preparation and characterization of composites using blends of divinylbenzene‐based hyperbranched and linear functionalized polymers

Abstract

AbstractIn this study, hyperbranched polymers were explored as matrix modifiers to create E‐glass fiber (GF) reinforced polymer composites with enhanced mechanical properties. Hyperbranched polymers have lower viscosities than their linear equivalents, potentially providing enhanced fiber wet out leading to improved stress transfer. Hyperbranched (HB), hydrogenated hyperbranched (H‐HB), and linear functional (LF) divinyl benzene were blended with linear polystyrene (LP) to form a range of composite matrix formulations. Blends of the HB and LP polymers were used since the neat hyperbranched polymers alone proved to be highly brittle when formed into a film. A neat LP‐GF composite was also prepared as control. Of the three matrix modifiers considered, only the H‐HB provided an improvement in mechanical properties in comparison to LP‐GF. With the addition of 10 and 20 wt% H‐HB, respectively, the flexural modulus increased by 25% (p < 0.05) and 36% (p < 0.05) and flexural strength increased by 15% (p < 0.05) and 31% (p < 0.005). The enhanced mechanical properties were attributed to better fiber wetting along with crystallization observed with the addition of 20 wt% H‐HB. The non‐reactive ethyl (CH2CH3) chain end group of the macromolecular H‐HB resulted in a plasticizing effect, which in turn improved its wettability. The LP:HB polymer blends, on the other hand, underwent crosslinking due to the presence of the vinyl (CHCH2) chain ends leading to poor wettability in comparison to the LP:H‐HB and LP:LF blended films and hence lower mechanical properties.