New publication
Structure formation in oligomers
How can the thermal stability and crystallinity of oligomers be controlled? Four members of a homologous series of chlorinated poly(vinyl ester) oligomers from poly(vinyl acetate) to poly(vinyl stearate) with degrees of polymerisation of 10 and 20 were prepared by telomerisation with carbon tetrachloride. All oligomers are thermally degraded in two main steps, whereby HCl and side chains are lost before the backbone is degraded. The polymers with short side chains, up to poly(vinyl octanoate), are amorphous and show internal plastification, while those with long side chains are semi-crystalline due to side chain crystallisation. The glass transition and melting temperatures as well as the initial decomposition temperature are more strongly influenced by the side chain length than by the degree of polymerisation. Thermal stability is improved when both the size and the number of side chains increase, but only long side chains lead to a significant increase in decomposition resistance.
D. Heinze, T. Mang, C. Popescu, O. Weichold
Effect of side chain length and degree of polymerization on thedecomposition and crystallization behaviour of chlorinated poly(vinylester) oligomers
Thermochimica Acta 2016, 637, 143-153. http://dx.doi.org/10.1016/j.tca.2016.05.015
Cold as Ice – gently dry
With Coolsafe Pro freeze drying, we can gently dry sensitive materials using an established process. The frozen water sublimates directly into the vapour phase. The process enables efficient, resource-saving drying, which increases the quality and shelf life of the materials. We use it to dry lignified starting materials, reaction products from aqueous syntheses or gels.
Tg, Tm, OMG – Understanding polymers
With every change in a system (e.g. phase transformation, chemical reactions), heat is either absorbed or released. This can be analysed quantitatively using differential scanning calorimetry. We can use a DSC 204 F1 Phoenix from Netzsch to measure cooling and heating processes from approx. -50 to 600 °C. The cooling and heating rates can be set from 0.1 to 100 K•min−1 .
New publication
Poly(vinyl acetate) plasticises itself
No additional plasticiser required. Poly(vinyl acetate), PVAc, with a degree of polymerisation Xn≈10 was produced by free radical chain transfer polymerisation with carbon tetrachloride and used as an oligomeric plasticiser for commercial PVAc. After H/Cl exchange at the chain ends, the product exhibits high thermal stability and excellent melt compounding properties. Blends of oligomeric and commercial PVAc show simple glass transition temperatures, which decrease with higher oligomer content, and exhibit small negative deviations from Fox’s linear additivity rule. This suggests that plasticisation and miscibility are mainly due to entropic effects. Injection moulded thick specimens show ductile behaviour at oligomer contents >10 wt%, while sheets with a thickness of 0.2-0.5 mm appear flexible already at 7.5 wt%. The oxygen permeability coefficients are an order of magnitude lower than those of low-density polyethylene. Due to the sum of their properties, the plasticised sheets represent a promising alternative for the production of barrier materials.
D. Heinze, T. Mang, K. Peter, M. Möller, O. Weichold
Synthesis of Low Molecular Weight Poly(vinyl acetate) and Its Application as Plasticizer
J. Appl. Polym. Sci. 2014, 40226. https://doi.org/10.1002/APP.40226
