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The influence of an elastomeric second-phase on the kinetics of the curing reaction and the gel-time of a standard unsaturated polyester resin, by using the isothermal and dynamic techniques of differential scanning calorimetry (DSC) and a thermocouple was investigated. In particular we examined two different rubbers (polybutadiene hydroxyl-terminated and polybutadiene isocyanate-terminated), that, in the presence of polyester resins, affect the overall curing reaction kinetics in two ways: the former reduces the rate of reaction whilst the latter increases it.

The crystallization and melting behaviour of isotactic polypropylene (iPP) samples synthetized with different catalyst systems (low and high-yield) have been studied by differential scanning calorimetry and optical microscopy. The isothermal crystallization rates from the melt have been found to depend on the catalyst system employed and on the isotacticity index of the sample. Moreover, for low-yield iPP, Avrami analysis of the overall kinetics has provided evidence of the presence of secondary crystallization phenomena. The values of the equilibrium melting point, energy of nucleation and surface energy of folding of iPP lamellar crystals have been calculated according to the ‘Kinetic theories’ of polymer crystallization. The observed variation of such thermodynamic parameters for the various iPP samples has been accounted for by the amount and type of configurational irregularities present along the chains and by the differences in the molecular weight distribution.

The kinetics of the cure reaction of standard unsaturated polyester resin was investigated by utilizing the isothermal and dynamic techniques of differential scanning calorimetry (DSC). The kinetic parameters and heat of the copolymerization reaction were determined. A method is proposed for optimization of the curing and postcuring of a polyester resin composite.

Differential scanning calorimetry and optical microscopy were used to determine the miscibility behaviour of poly- d (−)(3-hydroxybutyrate) (PHB) and poly(ethylene oxide) (PEO) mixtures. It was found that PHB and PEO are miscible in the melt. Consequently the blend exhibits a single glass transition temperature and a depression of the equilibrium melting temperature of PHB. The study of the isothermal crystallization process shows that at a given crystallization temperature the presence of PEO causes a depression in the growth rate of PHB spherulites. The blend exhibits a phase diagram characterized by the presence, below the apparent melting temperature of PHB and PEO, of interlamellar and/or interfibrillar homogeneous amorphous PHB/PEO mixtures. The Flory-Huggins interaction parameter (χ12), obtained from melting point depression data, is composition dependent, and its value is always negative.

The crystallization and thermal behaviour of crystallizable random propene/ethene copolymers (P-co-E) was systematically investigated. Index of crystallinity and, index of γ-form, enthalpy and entropy of fusion, equilibrium melting temperature, spherulite growth rate, and overall kinetic rate constant were determined and correlated with the overall ethene content and with the concentration of specific chemical defects as determined by 13C NMR analysis (PEP, EPP, EPE triads). The samples of the copolymers, obtained with very-high-yield Ziegler-Natta catalysts, were characterized by IR, 13C NMR, wide angle X-ray scattering, and differential scanning calorimetry.

A study on the crystallinity of ethylene-propylene saturated copolymers (EPR) of industrial source is reported. By DSC, with an appropriate choice of annealing experiments, several crystalline areas are found due to polyethylenic-type sequences of different length. The existance of such ordered sequences is confirmed by NMR data and WAXS analysis. The presence of multiple crystalline regions can be interpreted as due to discontinuous sequences distributions, as confirmed by an EPR simplyfied model made of mixtures of n-alkanes in squalane. An attempt is reported to apply classical theories of crystallization in copolymers to our commercial EPR systems.

The influence of glass fibres on the primary nucleation process, isothermal radial growth rate of spherulites and overall kinetic rate constant of isotactic polypropylene (iPP) has been examined. The polypropylene was also modified by means of acrylic acid (iPP*) in order to improve the adhesion between the matrix and the fibres, and the relative properties were compared with those concerning the composites having as matrix plain MR Moreover the mechanical properties of injection-moulded composites containing iPP and iPP* have been studied. These properties improved on increasing the fibre content. It was found that for the same glass-fibre content better values of the elongation at break and creep are observed in the case of reinforced polypropylenes having as matrix acrylic acid modified polypropylene.

One of the major deficiency of rigid thermoplastic materials as polystyrene, polyvinylchloride, isotactic polypropylene and polyamides is the resistance to impact, especially at lower temperatures. This limitation is commonly remedied by blending these polymers with rubbers.

Polyamides PA have poor impact resistance at temperatures below Tg particularly in the dry state. This inconvenience can be eliminated by incorporating in polyamide matrix a rubbery toughening agent. To improve the adhesion between the phases, minimize the interfacial energy, and influence the dimension of the dispersed rubber particles, a third component, such as a graft or block copolymer of appropriate chemical structure, can be added to such PA/rubber blends. These copolymers are generally referred to as “interfacial agents”1. Suitable interfacial agents for PA/rubber blends can be preformed and then added to the homopolymers to be blended or can be formed in situ by chemical reactions during the mixing process. In both cases it is necessary to modify the rubbery polymer in order to introduce appropriate functional groups along the ch ain2–6. In this paper we report on the preparation of a functionalized ethylene-propylene random copolymer (EPM) and on the synthesis of EPM-g-PA 6 graft copolymers utilizing the functionalized EPM. Preliminary results on the use of modified EPM rubbers in PA 6/EPM blends have been previously reported6.

Most of theoretical and practical investigations on the properties of polymer blends have been concerned mainly with systems containing amorphous components, while the properties of blends with crystalline components have received less attention. Only few examples of blends with crystallizable components have been investigated so far: poly(butyleneterephtalate)/poly(ethyleneterephtalate) (PBT/PET)1, high density polyethylene/low density polyethylene (HDPE/LDPE)2, nylon 6/nylon 113, isotactic polystyrene/poly(2,6-dimethyl-1,4-phenylene oxide) (iPS/PPO)4, isotactic polypropylene/isotactic poly(l-butene) (iPP/iPB)5, high density polyethylene/isotactic polypropylene (HDPE/iPP)6.

In recent years, scientific and industrial interest has been focused on the preparation of organic/inorganic nanocomposites because of their unique hybrid properties correlated with the enormous interfacial adhesion region that is a characteristic of nanoparticles. The objective of the whole research was to improve poly-caprolactone (PCL) mechanical and barrier performances by using silica spherical nanoparticles for filling. In particular, in order to improve the polymeric matrix/inorganic nanofiller's interfacial adhesion and consequently to achieve a fine nanometric dispersion, silica nanoparticles have been chemically modified by grafting onto them a hydroxyl endcapped PCL, after wheich they have been melt blended with high molecular weight PCL. In the present paper, details on the synthesis, morphology and mechanical properties of the prepared nanocomposites are reported. Moreover, a numerical tool has been used to predict the mechanical properties of the nanocomposite, starting from the morphology of the material observed by scanning electron micrography, and the individual properties of the constituents.

International audience; Vegetable fibers deriving from the basts of broom plants have been used as reinforcement for two polypropylenic matrices: a conventional isotactic polypropylene (iPP) and a maleate modified one (iPPMA). Before mixing the fibers were subjected to two different extraction procedures: a conventional alkaline treatment and an innovative steam explosion process. Afterwards, the composites obtained by compression moulding were thermally, morphologically, and mechanically characterized. Moreover, water absorption tests, to examine the behaviour of these materials in wet conditions, were also performed.

Multicomponent polymeric systems containing Biopol as one of the phases are described as obtained according to two different procedures : radical polymerization of an acrylic polymer in the presence of Biopol, and melt-mixing of Biopol with polycaprolactone in the presence of peroxide. The decomposition of peroxide causes, in both cases, the formation of intergrafted species responsible for interfacial activity and compatibilization. The results of chemical, chemical-physical, morphological and mechanical tests, confirming the occurrence of such interactions, are reported.

Poly(β.-hydroxybutyrate) (PHB) is a biotechnologically produced polyester, highly crystalline, totally biodegradable with low versatility in mechanical properties. To overcome this problem we performed a reactive blending procedure with a glassy acrylic polymer, poly(methyl methacrylate) (PMMA), via water suspension polymerisation of the acrylic monomer precursor onto poly(β-hydroxybutyrate). It was possible to isolate the co-polymeric phase formed between the two polymers and to characterize it using NMR and differential scanning calorimetry (DSC) techniques. Fracture tests on the blends gave a satisfactory response: in fact the Critical Energy Release Factor (Gc) calculated by Linear Elastic Fracture Mechanism (LEFM) theory of a PHB/PMMA 70/30 wt/wt blend is less than two times larger than that of neat PHB.

The influence of molecular weight and its distribution on the nucleation density, crystallization, thermal and mechanical behavior of isotactic polypropylene based composites has been investigated. The composites were prepared by compression molding. The ability of carbon and Kevlar fibers to nucleate the polypropylene has been studied during isothermal and nonisothermal crystallization, by optical microscopy and differential scanning calorimetry (DSC), as function of crystallization temperature T c and iPP molecular weight. Two extreme crystallization conditions were tested : quenching and slow crystallization to obtain crystals and amorphous phases of different structure. The ability of fibers to enhance mechanical properties in polypropylene based composites was examined by tensile tests at room temperature. It was found that nucleation density, crystallization parameters, and the results of tensile tests strongly depend on the molecular weight Mw of iPP, molecular weight distribution, and thermal history of polypropylene. The numerical values of the nucleation density have been found to strongly depend on the nature of fiber. In fact, Kevlar fiber has shown a better nucleating ability than carbon fiber. The results of tensile tests have been related to the sample morphology. The analysis of fractured specimens also provided useful information about fiber-matrix adhesion.

Nanocomposite based on PEI and PTFE-nanoparticles was obtained by solution blending method, using dichloromethane as a solvent. PEI-PTFE nanocomposite was used as a matrix for glass fibre reinforced composite. The obtained composites were characterized by DSC, TGA, flexural test and DMTA. Using SEM analysis, the homogeneity of distribution of nanoparticles was analysed. The main improvement for fibre reinforced nanocomposite matrix was recorded in their thermal stability and thermal resistance.

The influence of stereochemical composition of the radial growth rate of spherulites, the nucleation density, the overall rate of crystallization and the thermal behaviour of fractions of iPP samples synthesized with different catalyst systems (low, high and very high yield) was investigated. The study used 13C n.m.r., differential scanning calorimetry (d.s.c.) and optical microscopy. The 13C n.m.r. analysis showed that due to the presence of catalytic sites with different stereoregulating capability the catalyst system produces polypropylene with different stereoregularity. It was found that the growth rate of spherulites and the overall rate of crystallization are strictly related to the stereochemical structure of the polypropylene. Moreover, for the low yield iPP, phenomena of secondary crystallization were observed by Avrami analysis of the overall kinetics. Values of the equilibrium melting temperature (Tm), energy of nucleation (Δo∗) and surface free energy of folding (σe) of iPP lamellar crystals have been determined according to the kinetic theory of polymer crystallization. The values of such thermodynamic quantities as well as the thermal behaviour of various iPP are strongly dependent upon the amount and distribution of configurational irregularities existing along the chains and upon the molecular mass distribution.

Special anhydrides, such as hexahydrophthalic, methyl-hexahydrophthalic, nadic, methylnadic and methyl-tetrahydroxyphthalic, have been polycondensed with glycols such as propylene and di-propylene, to obtain new formulations for unsaturated polyesters. The properties of these resins, such as tensile behaviour and ultraviolet resistance, neat or mixed with anti-shrinkage additives have been examined and compared to standard polyester resins. Particular attention was paid to the study of the influence of low-profile agents on the resulting phase structures of cured systems. Moreover, the role played by the different phases on the fibre/matrix addition in composite materials reinforced with coated glass fibres was also investigated.

Microplastics may be accumulated in different marine ecosystems at increasing rates. They can be uptaken by a wide range of marine organisms. Direct consumption of microplastic is prevalent in suspension feeders, including zooplankton, oysters, and mussels, and deposit feeders, owing to their inability to differentiate between microplastics and prey. As a consequence, potentially adverse effects may be caused by the particles or chemicals added during the particle manufacturing or sorb to the microplastics.