Danuše Michálková

Compatibilization as a Procedure for Recycling of Commingled Polyolefin Waste

An efficient reactive compatibilization system based on the combination of liquid polybutadienes (both without and with functional groups) and dialkyl peroxide has been developed for polyolefin blends. Practical applications of the reactive blending procedure for recycling of commingled polyolefin waste were proposed. Tensile impact strength was used as the main criterion of compatibilization efficiency. Liquid polybutadiene without functional groups is an effective compatibilizer for the blends composed of virgin polyolefin components, while the properties of blends prepared from a control damaged polyolefin or from real polyolefin waste are more affected by maleinized liquid polybutadiene. Incorporation of a basic inorganic admixture and a small amount of elemental sulfur can increase the compatibilization efficiency. Uncompatibilized and reactive compatibilized LDPE/HDPE/PP model blends and blends of real polyolefin waste were studied by capillary rheometry. The flow behavior of reactive-compatibilized systems is close to that of uncompatibilized ones; these systems can be processed using current procedures of plastic industry.

Compatibilization of polyethylene/poly(propylene)/polystyrene blends

The compatibilization of mixtures of polyolefins or of polyolefins with polystyrene using either liquid polybutadiene (l-PB)/organic peroxide or styrene-butadiene-styrene (SBS) block copolymers was investigated. Tensile impact strength was chosen as a measure of compatibility. Binary blends LDPE/high-impact polystyrene (HIPS) and LDPE/poly(propylene) (PP) as well as LDPE/HDPE/PP/HIPS blends were prepared by blending in the chamber of a Brabender Plasticorder. Composition of the blends corresponds to real commingled plastic waste. It was found that l-PB-based compatibilizer enhanced the impact strength of LDPE/HIPS blends with LDPE contents higher than 60 wt.-% only. Also SBS copolymer enhanced the impact strength of LDPE/PP blends with LDPE contents higher than 40 wt.-%. Both the compatibilizers substantially increased the toughness of LDPE/HDPE/PP/HIPS blends with composition similar to the municipal plastic waste. Die Kompatibilisierung von Mischungen von Polyolefinen oder Polyolefinen mit Polystyrol unter Verwendung von entweder flussigem Polybutadien (l-PB) und organischem Peroxid oder Styrol-Butadien-Styrol-Blockcopolymeren (SBS) wurde unterucht. Die Schlagzugzahigkeit wurde als Mas fur die Vertraglichkeit herangezogen. In einem Brabender-Plasticorder wurden binare Blends aus LDPE und schlagzahem Polystyrol (HIPS) sowie LDPE und Polypropylen und LDPE/HDPE/PP/HIPS-Blends hergestellt; die Zusammensetzung der Blends entsprach derjenigen von Kunststoff aus Hausmull. Vertraglichkeitsvermittler auf der Basis von l-PB steigerten die Schlagzahigkeit der LDPE/HIPS-Blends mit LDPE-Anteilen uber 60 Gew.-%. SBS erhohte die Schlagzahigkeit der LDPE/PP-Blends mit LDPE-Anteilen uber 40 Gew.-%. Beide Vertraglichkeitsvermittler verbesserten wesentlich die Zahigkeit der LDPE/HDPE/PP/HIPS-Blends mit einer der von Hausmull entsprechenden Zusammensetzung.

Morphology evolution during cooling of quiescent immiscible polymer blends: matrix crystallization effect on the dispersed phase coalescence

The influence of the matrix crystallization on the coalescence of the dispersed phase particles, in quiescent immiscible polymer blends, is a topic that is scientifically addressed scarcely. The coarsening of the phase structure that is induced by the matrix crystallizing domains was studied using the well-established system comprising a polypropylene and an ethylene–propylene rubber (PP/EPR blends). This subject is of great importance as the effectiveness in the toughening of PP is directly determined by the EPR particle size. Cooling experiments were commenced for resolving the correlation among the imposed cooling conditions, the formed matrix crystalline morphology, and the coalescence of the dispersed phase particles. A confirmation of the profound effect of the PP crystallization on the coalescence of EPR particles was undoubtedly obtained. The contribution of the crystallization to the coalescence of the dispersed phase particles is largest at a finite rate of cooling. A thorough discussion regarding the observed effects, encompassing a potential rejection or an engulfing of the dispersed phase particles by the growing crystallites, was undertaken.

Phase Structure Evolution During Compression Molding of Compatibilized Polymer Blends

The phase structures of quenched, annealed, and compression-molded samples of polypropylene/polystyrene/styrene–butadiene block copolymer (PP/PS/SB) blends were compared with the aim to elucidate the phase structure evolution during individual steps of compression molding. It was found that PS particles partitioned with SB are formed by coalescence in a hot press. Measurement of the temperature during cooling of compression-molded samples showed that a decrease of the temperature in molten PP to its crystallization temperature is fast, and coalescence during this step is small. Coalescence induced by rejection of dispersed particles from the crystallizing front of PP matrix gives a remarkable contribution to the size of PS particles in compression-molded samples. This should be considered, besides coalescence in a hot press, for description of the phase structure evolution during compression molding for all blends with a semicrystalline matrix.