Two series of poly(ester urethane)s were prepared, containing polycaprolactone (PCL) as the soft segment with molecular weights of 530 and 2000. In each series, the soft‐segment/hard‐segment ratio was varied, and the morphological changes were monitored with differential scanning calorimetry, dynamic mechanical thermal analysis, wide‐angle X‐ray scattering, and scanning electron microscopy techniques. The polyurethanes with longer PCL segments retained their crystallinity, whereas those with shorter PCL segments did not. A morphological model is proposed, in which a continuous PCL‐rich matrix contains both PCL crystallites and domains of urethane hard segments. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4117–4130, 2002

Two series of segmented polyurethanes were prepared with systematic variation in soft and hard segment length. The soft segment was constituted by polycaprolactone (PCL) blocks of molecular masses 530 or 2000 and the hard segment (HS) by urethane blocks, in a concentration that varied from 12% to 44% in weight of the whole polyurethane. Morphological analyses indicated that the amount of crystallinity of copolymers was strongly dependent on the PCL molar mass and hard segment content. The copolymers with longer PCL soft segments (Mn=2000) were semicrystalline, but those with shorter PCL segment (Mn=530) were unable to crystallize. The primary factor affectingthe biodegradability of copolymers as evaluated by Sturm tests was the extent of the phase separation, and that the segmental blending of the less biodegradable polyurethane (HS) blocks with PCL in the amorphous phase had a critical unfavorable consequence, which may be attributed to the size of the accessible area by microorganisms.

Sumary: Plastics materials are widely used in the manufacturing of many products like bags, packings, electronic components among other applications. Most polymers are extremely durable and this durability cause serious environmental problems because of the large amount of waste discarded mainly in the urban centers. Thus, biodegradable polymers are a potencial way to minimize these problems. Polyurethanes based on poly(ε‐caprolactone) (PCL) as soft segment were prepared taking into account the biodegradable charater of this last compound. The hard segment was built up by reaction between tolylene diisocyanate (TDI) and a chain extender (1,4‐butanediol) or two crosslinking agents (sucrose or glucose). The biodegradation behavior of the polyurethanes was verified using solid and submerged fermentation and using natural conditions under the soil. The analysis indicated that the biodegradation was affected by the PCL segment, hard segment content, intermolecular interations manly H bonds and crosslinking.

Bentonites, which the main clay mineral is montmorillonite, are commercially attractive because of its abundance in nature. The clays can be modified by ion exchange reactions of ions contained in the interlayer region with cationic surfactants that include ammonium or phosphonium salts. The clays origin and the type of surfactants (modifiers) are the main factors in the alteration of physical and chemical properties of these materials. This study aims to characterize and compare the results of natural bentonites commercially available and the effect of treatments with quaternary ammonium salt and an organic compound free of ammonium salt. The FTIR and XRD results indicate the process of organophilization of clays after treatment with the surfactants. These treatments have altered the average particle size, suggesting the formation of agglomerates, which was showed in the SEM images. The results of surface area and particle size data indicated the presence of larger particles. Although the two surfactants have shown similarities in the investigated properties, the organoclays free of ammonium salt are more promising in terms of its use as well as for their preparation and solubility.Keywords: Bentonites; organoclays; surfactante. ResumoAs bentonitas, que tem como principal argilomineral a montmorilonita, são comercialmente atraentes devido sua abundância na natureza. Estas podem ser modificadas geralmente, através de reações de troca iônica dos íons contidos da região interlamelar com os surfactantes catiônicos, que incluem sais de amônio ou fosfônio. A origem das argilas e o tipo dos surfactantes (modificadores) são os principais fatores na alteração das propriedades físicas e químicas destes materiais. Este estudo tem como objetivo caracterizar e comparar os resultados de bentonitas naturais, comercialmente disponíveis, e o efeito dos tratamentos utilizados com sal quaternário de amônio e um composto orgânico livre de sal de amônio. Os resultados de FTIR e DRX indicam o processo de organofilização das argilas naturais após o tratamento com os surfactantes. Estes tratamentos alteraram o tamanho médio das partículas, sugerindo a formação de aglomerados, fato observado nas imagens de MEV. Os resultados das áreas superficiais e os dados de granulometria indicaram a presença de partículas de maior tamanho. Embora os dois surfactantes tenham apresentado similaridades nas propriedades investigadas, as argilas organofílicas livre de sal de amônio são mais promissoras quanto sua utilização, quanto ao seu preparo e solubilidade.Palavras-chave: Bentonitas; argilas organofílicas; surfactantes.

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