Abstract:The objective of this study was to gain a deep understanding of composition and compatibilization effects on the properties of entirely sustainably sourced polymer blends based on polylactide (PLA) and polyamide 11 (PA11). Generally, PLA cannot challenge regular commodity polymers due to its weak thermo-mechanical properties and its poor elongation properties. With this work, however, we present a promising route to overcome these drawbacks in order to enhance the processability of PLA: blending the polymer with various compositions of other ductile biopolymers such as PA11, as well as mixing PLA/PA11 blends with various amounts of a chain extender, Joncryl ADR ® -4368, containing reactive epoxy functions, in a laboratory-scale twin-screw extruder. The effects on the rheological, morphological and mechanical properties were investigated. Results showed that a "self compatibilization" between PLA and PA11 chains can occur but it was found to be insufficient, contrary to recent work reported in the literature. The role of Joncryl as a compatibilizer for the PLA/PA11 system has been demonstrated by the significant decrease of particle size and interfacial tension as well as the improvement of ductile properties. Moreover, a new relaxation peak appeared in the relaxation spectrum, indicating the generation of a copolymer at the polymer-polymer interface.

International audienceAlfa stems are rich in cellulose and they are an inexpensive, easily renewable source of natural fibers with the potential for polymer reinforcement. However, large amounts of non-cellulosic materials, surface impurities and low degradation temperature make natural fibers less attractive for reinforcement of polymeric materials, unless they can be modified in a proper way. In this paper, Alfa stems were treated with NaOH solution with two different concentrations (1 and 5 wt%). Raw and treated stems were crushed to obtain fibers. Stems and fibers were characterized by scanning electron microscopy (SEM) and optical microscopy, respectively. Their crystallinity index was determined by X-ray diffraction, thermal stability by thermogravimetry and structural change by FT-IR and C-13 NMR spectroscopy. Comparison and analysis of results confirmed some thermal, structural and morphological changes of the fibers after treatment due to removal of some non-crystalline constituents from the plant. SEM showed rougher surfaces after alkalization. FT-IR and 13C NMR showed a gradual improvement in cellulose level by alkali treatment with increasing NaOH concentration. The crystallinity index and thermal stability of treated Alfa fibers were also found to be improved

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This paper deals with immiscible blends of poly(ethylene terephthalate) obtained by melt blending with polycarbonate. A large survey of the current knowledge in the field of these blends is presented. Resolved and unresolved issues concerning the effect of exchange reactions on the miscibility of the components are addressed. The experimental part of the paper focuses on the rheological behavior of PET/PC blends. Blends containing various polymer ratios were obtained by melt blending with and without transesterification catalysts. Oscillatory shear flow in the melt was used to characterize the rheology of the various samples. A plot of the oscillatory data, similar to the Van Gurp Palmen plot, is used to point out the broadening of the co‐continuity window when in situ compatibilization takes place.magnified image

ABSTRACT:The objective of this work was to study the effectiveness of low-cost commercial compatibilizers and several processes (internal mixer, single-and twin-screw extruders) for two types of plastic blends: high-density polyethylene/polypropylene and high-density polyethylene/ polystyrene blends, to gain insight into the recycling of wastes from those frequently encountered mixed plastics. Blends going from a pure A to a pure B component, with and without a compatibilizer, were prepared using an internal mixer, a corotating twin-screw extruder, as well as a single-screw extruder to follow an industrial-convenient process. In both cases, the analyses of blend morphologies highlighted the poor adherence between the two phases in the uncompatibilized blends. Compatibilized blends display better adherence between phases and the ability to process blends made from both single-and twin-screw extruders. When adding a compatibilizer, the viscosity of each blend (PE/PP or PE/PS) increased due to a better adhesion of the phases. Charpy impact tests showed that the presence of the compatibilizer in PE/PS blends increased their impact properties. Indeed, the improvement of the adhesion between the two phases enabled stress transfer at the interface. A singlescrew extruder seems to be efficient as a processing method on an industrial scale when a compatibilizer is used.

The plastic materials used for packaging are increasing leading to a considerable amount of undegradable solid wastes. This work deals with the reduction of conventional plastics waste and the natural resources preservation by using cellulosic polymers from renewable resources (alfa and luffa). Plasticized starch films syntheses were achieved at a laboratory scale. These natural films showed some very attractive mechanical properties at relatively low plasticizers levels (12 to 17 % by weight). Furthermore, mixtures including polylactic acid polymer (PLA) and cellulose fibers extracted from alfa and luffa were investigated by melt extrusion technique. When used at a rate of 10 %, these fibers improved the mixture mechanical properties. Both developed materials were biodegradable, but the plasticized starch exhibited a faster biodegradation kinetic compared to the PLA/cellulose fibers. These new materials would contribute to a sustainable development and a waste reduction.

The article addresses the issue of recycling of poly(ethylene terephtalate) (PET) by melt blending with polycarbonate (PC). PET/PC blends containing various amounts of the immiscible polymers were prepared in a twin-screw extruder. Selected compositions were also prepared in the presence of an Sn-based catalyst to assess the influence of transesterification during melt mixing. The degree of miscibility in the blends was studied using differential scanning calorimetry, scanning electron microscopy, and mechanical testing. PET/PC blends exhibit enhanced tensile properties in comparison to neat components for compositions of PET higher than 50% and these properties are improved by the addition of a transesterification catalyst. The PET/PC blend containing 20 wt% of PC, prepared with stannous octoate, shows the smallest size of the dispersed phase because of transesterification reactions that generate copolymer molecules at the interface between the immiscible polymers. The melting temperature of PET is decreased with the increase of the PC content in blends extruded in the presence of the catalyst. Also, the temperatures of the cold crystallization of PET are higher than those of similar blends without added catalyst. Both features give rise to better molding properties because of a shortening of the cooling time in the range of 50-90 wt% of PET

Blends of recycled poly(butylene terephthalate) (PBT) parts obtained from scrapped cars, and virgin polypropylene (PP), were prepared in a twin‐screw extruder at different compositions. Selected compositions were also prepared with the presence of ethylene‐co‐glycidyl methacrylate copolymer (E‐GMA) and ethylene/methyl acrylate/glycidyl methacrylate terpolymer (E‐MA‐GMA) compatibilizers. The effect of the composition and the type of compatibilizer, as well as the mixing conditions, on the morphology phase, thermal, viscoelastic behavior, and mechanical properties of the blends has been investigated. Blends PP/PBT of various composition exhibit a coarse morphology and a poor adherence between both phases, resulting in the decrease of ductility, whereas at weak deformation, PBT reinforced the tensile properties of PP. Addition of E‐GMA and E‐MA‐GMA to the PP/PBT blend exhibited a significant change in morphology and improved ductility because of interfacial reactions between PBT end chains and epoxy groups of GMA that generate EG‐g‐PBT copolymer. Moreover, thermal and viscoelastic study indicated that the miscibility of PP and PBT has been improved further and the reactions were identified. The E‐MA‐GMA results in the best improvement of ductility. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers