Macromolecular Materials and Engineering

Front Cover: Unlike the normal pristine MMT particles, which are compact and plane-shaped, these spray-dried pristine MMT particles display extraordinary flower-shaped morphologies. This indicates that the rapid evaporation process brought about by the spray-drying method achieves structures made of randomly arranged MMT layers in the granule. Further details can be found in the article by M. Lu, Y. Wang, Y. Wu, Y. Quan, X. Wu, L. Zhang,* and B. Guo on page 20.

Back Cover: Well-dispersed SiO₂ nanoparticles localize exclusively in the PP phase of PP/EOC blends, resulting in a good balance of tensile, flexural, and impact properties. In the presence of nanoparticles, the domain size of the dispersed EOC phase is reduced, as evidenced by simple shear and annealing experiments. Further details can be found in the article by S. H. Lee, M. Bailly, and M. Kontopoulou* on page 95.

Reduced-order modeling using population balances and data-driven statistical approaches are employed to study continuous powder mixing. These models can be used for process design, optimization, and design space identification with respect to process operating conditions. The computational efficiency of such models renders them appropriate for online optimization and control purposes.

A facile route to highly dispersed clay/polymer nanocomposites by combining latex compounding and spray-drying is described. The method can be applied to any latex-formed polymer matrix. HR-TEM and XRD results confirm the excellent dispersion of MMT layers in both the styrene/butadiene rubber matrix and the polystyrene matrix.

ICPP is a complex material and contains various ethylene/propylene copolymers in addition to the majority poly(propylene) phase. TREF and CRYSTAF are used to study the differences in the thermo-oxidative degradation of ICPP. A higher ethylene content increases the thermal stability because a larger fraction of ethylene/propylene copolymer with a lower isotacticity is formed that is less prone to degradation.

Mixing torque data from a melt blender for reactions carried out between maleic anhydride-grafted polyethylene and an aliphatic diamine suggest longer reaction times than previously proposed for such systems. Separate mixing torque peaks were observed for melting of polymers and crosslinking resulting from reactions between amines and anhydrides. Analyses suggest that assessing the chemistry and degree of reaction based on the maleic anhydride response in FTIR is misleading.

Well-dispersed carbon-black aggregates can form a filler network in isotactic poly(propylene) melts. The dynamic network formation process shows that a conductive network is easier to be formed than the rheological network. The difference between the two networks is discussed based on the different factors governing the formation of the networks.

Tests are conducted in a shear device to study the effect of flow on the resulting morphology. It is found that the distribution of the spherulite dimensions can be directly correlated to a parameter connected to the Weissenberg number that also considers the time evolution of molecular deformation. The boundary between the oriented skin layer and the spherulitic core is characterized by a single value of this parameter.

Solution melt polymerization followed by extrusion is assessed for the in situ intercalation of PA 6.6/clay nanocomposites, focusing on the influence of the nanofillers as well as on the interactions between monomers and nanofiller. Polymerization enhancement up to ≈75% is found in the presence of fully organically exchanged clays. This is attributed to possible chain extension performance of clay SiOH groups.

By combining PLA and PHBV in a bicomponent fiber and introducing a new spin pack concept enabling individual temperature control for each polymer flow, the known difficulties with spinning of native PHBV can be overcome. Fibers with PLA as a sheath material are strong enough for the successful construction of a textile fabric. In vitro biocompatibility studies reveal that cells proliferate well along the fibers.

The effect of the degree of branching (DB) of a hyperbranched polyester added as modifier in DGEBA thermosets has been studied using ytterbium triflate as cationic initiator. High DB accelerates the curing and lowers the viscosity. Thermal stability and chemical reworkability are not affected by the DB but shrinkage exhibits a significant reduction on increasing it. Thermomechanical characteristics are improved with increasing the DB of the modifier.

The microstructure and mechanical properties of ternary PP/EOC/SiO₂nanocomposites are studied. In the presence of a maleated PP compatibilizer, the well-dispersed SiO₂ nanoparticles localize exclusively in the PP phase, resulting in a good balance of tensile, flexural, and impact properties. In the presence of nanoparticles the domain size of the dispersed EOC phase is reduced.