J. J. Robin

Study of thermal and mechanical properties of virgin and recycled poly(ethylene terephthalate) before and after injection molding

Abstract In this study, we compared the thermal properties (glass transition, melting point and crystallinity) and mechanical properties (Young’s modulus, elongation at break and impact strength) of post-consumer poly(ethylene terephthalate) (PET) bottles with those of the virgin resin. We studied two types of scraps of recycled PET: one arising from homogeneous deposits of bottles and the other of heterogeneous deposits soiled by contaminants such as PVC and adhesives. The presence of contaminants and residual moisture coming in the shape of scraps facilitate the crystallization of recycled PET compared to virgin PET and induces cleavages of chains during the melt processing. This leads to a reduction in intrinsic viscosity and consequently in molecular weight, and these decreases are more significant when the recycled resin is soiled. Virgin PET exhibited a ductile behavior (>200% of elongation at break),whereas post-consumer PET bottles exhibited a brittle one (

Study of morphological and mechanical properties of PP/PBT blends

SummaryThe synthesis of emulsifiers has been performed by the condensation of terephthaloyl chloride, butanediol and hydrogenated α-ω hydroxy polyisoprenes. The products are carefully characterized by 1H-nuclear magnetic resonance (NMR), infra-red spectroscopy and size exclusion chromatography.The PP/PBT blend, in a 60:40 ratio, was prepared with, and without, emulsifiers by melt-blending. The effect of these emulsifiers on mechanical properties and morphological studies of the PP/PBT blend was examined.

Chemical modification of virgin and recycled poly(ethylene terephthalate) by adding of chain extenders during processing

The processing of recycled poly(ethylene terephthalate) (PET) involves thermal and hydrolitic degradation of a polymer, which reduces the molecular weight, the intrinsic viscosity, and the mechanical properties of recycled materials. Degradative effects can be limited by using chain extenders. Preliminary tests show that the diisocyanates are more reactive toward the end groups of virgin PET than are bis-oxazolines or diepoxides under the experimental conditions used. So, samples of modified virgin PET with diisocyanates possess molecular weight and intrinsic viscosity (Mw > 60,000 g/mol and [η] > 1 dL/g) superior to those of virgin PET (Mw > 40,000 g/mol and [η] > 0.70 dL/g). Chemical modification of recycled PET by diisocyanates leads to an increase in the molecular weight from 30,000 to 51,000 g/mol, the intrinsic viscosity from 0.60 to 0.84 dL/g, and the mechanical properties, particularly the elongation at break, from 5 to 300%. Chemical modification of recycled PET by injection molding is an interesting method from an industrial point of view because it provides a recycled material possessing properties close to virgin PET in one-step processing.

Reactive compatibilization of HDPE/PET blends by glycidyl methacrylate functionalized polyolefins

Blends of high-density polyethylene (HDPE) and poly(ethylene terephthalate) (PET) in weight compositions of 20/80, 40/60, 60/40 and 80/20 were modified with glycidyl methacrylate functionalized polyolefins with the aim of improving the compatibility and in particular elongation and impact strength. The compatibilizers used were ethylene/glycidyl methacrylate copolymers (E/GMA) and ethylene/ethyl acrylate/ glycidyl methacrylate terpolymers (E/EA/GMA) with variable contents of reactive functions ( 1 to 8 wt.-% of glycidyl methacrylate). The effects of the compatibilizers were evaluated by studying the mechanical properties and the morphology of the blends. The addition of 5 wt.-% of functionalized polyolefins was found sufficient to improve ductility and impact strength of all compositions. A more pronounced compatibilizing effect was obtained with the functionalized terpolymer containing the smallest amount of glycidyl methacrylate. With this emulsifying agent, elongation at break is increased by a factor of four for the compositions near the inversion of phases. However, the main interest of this work is that it provides a compatibilization of immiscible blends of polyolefin and polyester by injection moulding. This melt processing is very interesting from an industrial point of view because it proves that materials with good mechanical properties can be obtained in one step of processing.

In situ compatibilization of HDPE/PET blends

The reactive compatibilization of immiscible polymers such as high-density polyethylene (HDPE) and poly(ethylene terephthalate) (PET) by interfacial grafting of maleic anhydride (MA) without initiator in the molten state was investigated in this study. Grafting reaction of MA onto HDPE was carried out in a Rheocord HAAKE mixer varying reaction parameters such as the temperature, the shear rate, and the time of reaction. Then, the purified copolymers were characterized by infrared spectrometry and the MA content of HDPE-g-MA copolymers was determined by volumetric titration. It has been shown that thermomechanical initiation is sufficient to reach grafting yield of 0.3 to 2.5 wt % of MA. We studied then the compatibilization of HDPE/PET blends by interfacial grafting of MA. The in situ interfacial reaction leads to the formation of HDPE-g-MA copolymer which acts as a compatibilizer in the blends. The foremost interest of this work is that it provides a simple way of compatibilization of immiscible blends of polyolefin and polyester in one transformation step without using free-radical initiators. The mechanical properties of the blends are strongly improved by the addition of small quantities of MA. The SEM observations of the compatibilized blends show a deep modification of the structure (i.e., enhanced regularity in the nodule dispersion and better interfacial adhesion).

Synthesis and applications of graft copolymers from ozonized poly(vinylidene fluoride)—II

Abstract The synthesis and the applications of graft copolymers prepared from ozonized poly(vinylidene fluoride) (PVDF) are described. The homopolymer was treated with ozone and then copolymerized with monomers such as styrene, acrylic acid, glycidyl methacrylate or methyl methacrylate. The products were used as emulsifiers in polymer blends and as promoters for the adhesion of PVDF to composites made of epoxide matrices filled with glass fibres. The mechanical properties of these products are described. The copolymers were characterized by the grafting-rate.

Recycling of PET and PVC wastes

A method for recycling mixed PET and PVC wastes is described. Glycolysis of PET leads to oligomers that are polycondensed with caprolactone. The obtained diols are extended with hexamethylene diisocyanate. In certain conditions the polyurethanes are totally miscible with PVC, leading to acceptable mechanical characteristics for the blend. A relation between the structure of the polyurethane and miscibility with PVC is described. The mechanical characteristics of the blend depends on the polyurethane chemical structure.

Radical polymerization of ethyl acrylate with dead end polymerization conditions

Abstract The radical polymerization of ethyl acrylate (EA) with 4,4′-azobis(4-cyanovaleric)acid as initiator was investigated in propionitrile at 363 K in order to obtain carboxy-telechelic oligo(ethyl acrylate). The results of functionality and molecular weights showed that a transfer reaction had occurred. A molecular weight study was performed in order to show the importance of transfer to solvent due to the high reactivity of the EA radical. Finally, the radical polymerization was investigated at very low temperature (253–273 K), using a redox system initiation. A behavior of dead end polymerization was observed but the activation energy of propagation for EA is still high and does not allow the synthesis of a telechelic oligomer.