Composites & Polycon 2013
COMPOSITES & POLYCON 2013
American Composites Manufacturers Association
January 29, 2012
Orlando, FL USA
Why Titanates & Zirconates May be Better Coupling Agents than Silanes for Glass, Aramid & Carbon Fiber and NanoReinforcements – and Why Endothermic Titanium Is Better Than Exothermic Cobalt for Peroxide Cured Thermoset Composites
by Salvatore Monte
Abstract
Data and references are provided to demonstrate the efficacy of titanates and zirconates in unfilled and filled (inorganic and organic fiber/pigment/nano-particulate) polymers with an emphasis on why titanates & zirconates may be better coupling agents than silanes for glass, aramid & carbon fiber and nano-reinforcements when examined at the interface as explained by the author’s four decades of experience in dealing with titanate, zirconate, aluminate, and silane coupling agents in polymeric composites. And why endothermic titanium free radical reduction is better than exothermic cobalt for peroxide cured thermoset composites.
Introduction
Organometallic Ti or Zr coupling agents provide
significantly different alternative coupling mechanisms
when compared to silanes. The differences are explained
through their chemistry and Six Functions. It will be shown
that the interfacial coupling mechanism of a neoalkoxy
titanate or zirconate via in situ surface proton (H+)
coordination is superior to silane (OH-) pretreatment
condensation mechanisms because of the number of bonds
and the differences in hydroxyl group availability from
interface to interface. E-Glass is the most widely used
reinforcement in MEKP unsaturated polyester composites,
but is it the best one? The paper will show why a zirconate
can adhere silane sized E-Glass to a fluoro polymer such as
ETFE, while the E-Glass alone doesn’t. Salt water boil for
240-hour tests will show silanes fail at the interface while
zirconates and titanates don’t. The paper will also address
questions such as: How can a silane couple CNT’s or
graphene or sulfates or carbonates or cement that have no
hydroxyl groups? How can nano-intumescence be
achieved with a silane that does not have phosphato
heteroatom functionality built into its ligands? The paper
will also address the question: Why does the industry
continue to use cobalt naphthenate as an accelerator in
MEKP cured unsaturated polyester creating exothermic
micro-bubbles and the subsequent problems of strength,
aging and surface finishing, which can be eliminated by
replacing the cobalt with certain titanate coupling agents
thus utilizing titanium’s latent cure effects, which in turn
creates slower endothermic bubble-free cures that can use
heat (40°C) or more aggressive peroxides to speed cures
even faster than cobalt resulting in fourteen-fold increase
in the impact strength of an unfilled and unreinforced
unsaturated polyester? Current work from the literature
will be shown and some of the more interesting
developments in the field of alternate interface
technologies will be reviewed. New generation 1.5-
nanometer hybrid organometallics are also discussed.
Note: The full copy of the technical paper is available
upon execution of a NDA.