Blends of high-density polyethylene (HDPE) and polypropylene (PP) were prepared in different twin-screw extruders. Two additives, a peroxide initiator and a polymerizable monomer, were added to the polymeric feed components. A large influence on the physical properties, such as toughness and impact strength,. and on the morphology was observed. Reactive extrusion substantially improves mechanical properties: a three-fold increase of elongation at break and doubling of the impact strength. Variation of extruder settings also had a large influence on the product; the f i n a l properties were improved when the shear rate was raised, but sufficient residence time is necessary in reactive compatibilization. Scanning electron micrographs of the fracture surfaces of blends indicate a refinement of the surface structure.

This article describes the radical copolymerization of styrene (St) and n‐butyl‐methacrylate (BMA) in a counter‐rotating twin‐screw extruder. In order to investigate the effect of the polymer melt viscosity on the working domain in reactive extrusion, the copolymer was crosslinked with different amounts of divinylbenzene (DVB). Crosslinking of the polymer resulted in a higher polymer melt viscosity. It was demonstrated that not only the product properties but also the process characteristics were strongly influenced by the addition of divinylbenzene to the reaction mixture. The product properties changed as expected: more crosslink agent led to a higher molecular weight or an increase in gel fraction, and a much higher melt viscosity of the polymer. Besides these effects on the product properties, the addition of DVB resulted in a more stable process, leading to an enlarged working domain.

The objective of this study is to investigate the effect of reactive processing of commingled bottle waste polymer in an extruder. A variety of peroxides and monomers were tested to assess their influence on the final mechanical properties of the product. The reactive extruded polymer blends were prepared in two types of extruders: a co-rota-twin-screw extruder and a Buss co-Kneader single-screw extruder. Blends were analyzed for mechanical and thermal properties. The effectiveness of the different monomers and peroxides was evaluated in terms of improvement in impact properties. It has been found that the toughness of the polymer blend is improved by reactive processing. Depending on the amount and type of reactants, the impact strength can be improved by 220%. with a slight reduction in the modulus compared to an unmodified physical blend. The most suitable monomers were n-butylmethacrylate (BMA), t-butylamino ethylmethacrylate (TBBMA) and a combination of styrene/maleic anhydride (ST/MAH). The peroxide should have a short half-lifetime compared to the average residence time in the extruder. The most effective monomers have a high initial reactivity and low rate of evaporation at the processing conditions used. Changes in processing conditions in the extruder influence the reaction conditions and therefore the final properties of the blend. Results were interpreted in terms of residence time, melting profile and peroxide concentration. EXPERIMENTAL Raw Material and AdditiveaThe waste polymer used in these experiments consisted of shredded and washed shampoo bottles provided by =KO, lot 2360, sample M043210. DSC was used to determine the relative melting enthalpies of both the PP and the HDPE fraction. From the melting enthalpies of the bottle waste, the HDPE fraction was determined to be 90% ( 2 2%). This material was compounded in the twin-screw extruder and the mechanical properties of compression-molded samples were determined as shown in Table 1 (abreviations and symbols are explained in the Nomenclatura section).