(668a) Copolymers of Styrene, Methyl Methacrylate, and Ethylene with a Series of Vinyl Esters: A Study of Thermal Mechanical and Rheological Properties | AIChE

(668a) Copolymers of Styrene, Methyl Methacrylate, and Ethylene with a Series of Vinyl Esters: A Study of Thermal Mechanical and Rheological Properties

Authors 

Wang, H. - Presenter, University of North Dakota
Kolodka, E. - Presenter, University of North Dakota


Copolymers of Styrene, Methyl
Methacrylate, and Ethylene with a Series of Vinyl Esters: A Study of Thermal
Mechanical and Rheological Properties

A number of new processes are being
developed which produce bio-sourced fatty acids of various molecular weights.
These fatty acids can easily be converted into vinyl esters using common
processes. However, vinyl esters larger than vinyl propionate are not suitable
for homopolymerization due to the low glass transition temperatures (Tg)
of the homopolymers. Therefore, this work will focus on the copolymerization of
vinyl esters of various molecular weights with both styrene and ethylene.
Particular emphasis will be placed on the influence of vinyl ester molecular
weight on the polymerization kinetics and thermomechanical characteristics of
the resultant copolymers.

In this study copolymers of styrene (St)
and methyl methacrylate (MMA) with a series of vinyl esters (VEs) including
vinyl acetate (VAc), vinyl propionate (VPr), vinyl hexanoate (VHe), and vinyl
decanoate (VDe) were prepared by bulk copolymerization initiated by azobisisobutyronitrile
(AIBN) at 60 °C. Copolymers of ethylene with the VEs were synthesized by
solution copolymerization initiated by AIBN also at 60 °C. The compositions and
molecular weight distributions (MWD) of all the copolymers were determined by
GPC. The impact of compositions and branch lengths on the thermal mechanical
properties of copolymers including glass transition temperature (Tg),
melting point (Tm), storage modulus (G') and loss modulus (G'') was
determined by dynamic mechanical analysis. In addition, the rheological
responses (complex viscosity versus shear rate) of the copolymers of MMA-VEs
and ethylene-VEs were studied.

Current results showed that the molecular
weights (MWs) of the copolymers decreased as the mole fraction of VEs in the
feed increased. Meanwhile, copolymers with similar VE incorporations had higher
MWs for poly (St-co-VHe) and poly (St-co-VDe) than those of poly (St-co-VAc)
and poly (St-co-VPr). It could be explained by the significantly higher
reactivity ratios of both VHe and VDe than those of VAc and VPr. Incorporating
VEs with different chain lengths from 1 mol% to 19 mol% reduced the Tg
of PS by up to 32 °C. The Tg of poly (St-co-VEs) decreased as the
mole fraction of VEs increased. Poly (St-co-VEs) with longer branches, such as
poly (St-co-VHe) and poly (St-co-VDe), exhibited a larger drop in Tg
than VAc and VPr copolymers at similar compositions. However, the branch
effects on Tg were not significant for copolymers containing VEs
less than 5%.