The effect of branch density polyoxymethylene copolymers

Today, there is a great need for polymers made from biorenewable resources due to the increasing price and diminishing supplies of petroleum and the overabundance of plastic waste in landfills. Polyoxymethylene can be produced from biorenewable feedstocks, depolymerized to formaldehyde through chemical recycling, and may be a viable alternative to many polyolefins. However, there has been limited research on varying the thermomechanical properties of polyoxymethylene so that it can be used in a wider variety of applications. Our approach employs the cationic copolymerization of trioxane with various amounts of 1,2-epoxyalkanes and 4-alkyl-1,3-dioxolanes to arrive at polyoxymethylene derivatives with controlled branching and morphology. Branching content has been measured by nuclear magnetic resonance (NMR) spectroscopy and correlates well with the comonomer feed fraction. The melting temperatures of the copolymers, determined from differential scanning calorimetry (DSC), are depressed predictably with increasing amounts of comonomer incorporation. The copolymerizations behaved the same regardless of whether the comonomer was an alkyldioxolane or epoxyalkane. 1,2-Epoxybutane/trioxane copolymers and 4-ethyl-1,3-dioxolane/trioxane copolymers gave the best melting point and % crystallinity results using boron trifluoride diethyl etherate as the cationic initiator.