Linear Unsaturated Polyesters Research Articles

Bifunctional and recyclable polyesters by chemoselective ring-opening polymerization of a δ-lactone derived from CO2 and butadiene.

When aiming at the direct use of CO2 for the preparation of advanced/value-added materials, the synthesis of CO2/olefin copolymers is very appealing but challenging. The δ-lactone 3-ethylidene-6-vinyltetrahydro-2H-pyran-2-one (EVP), synthesized by telomerization of CO2 with 1,3-butadiene, is a promising monomer. However, its chemoselective ring-opening polymerization (ROP) is hampered by unfavorable thermodynamics and the competitive polymerization of highly reactive C=C double bonds under usual conditions. Herein, we report the chemoselective ROP of EVP using a phosphazene/urea binary catalyst, affording exclusively a linear unsaturated polyester poly(EVP)ROP, with a molar mass (Mn) up to 16.1 kg·mol-1 and a narrow distribution (Ð < 1.6), which can be fully recycled back to the pristine monomer, thus establishing a monomer-polymer-monomer closed-loop life cycle. In these polyesters, the CO2 content reaches 33 mol% (29 wt%). The reasons for the unexpected chemoselectivity were investigated by Density-functional theory (DFT) calculations. The poly(EVP)ROP features two pendent C=C double bonds per repeating unit, which show distinct reactivity and thus can be properly engaged in sequential functionalizations towards the synthesis of bifunctional polyesters. We disclose here a methodology providing a facile access to bifunctional and recyclable polyesters from readily available feedstocks.

Synthesis, physical properties, and functionalization of biobased unsaturated polyesters derived from Cis-2-butene-1,4-diol

This work describes the synthesis, thermomechanical properties, and functionalization of unsaturated polyesters based on biobased cis-2-butene-1, 4-diol (cB). Under an optimized experimental process, polyesters were synthesized by melt polycondensation employing cB and α, ω-diacids with even chain length. The high molecular weight of Mw up to79.5 kDa was achieved for the poly(cis-butene dicarboxylate)s (PcBX), and meanwhile without isomerization or branching side reactions occurring in the polycondensation. Hence, cB was a suitable unsaturated diol for direct usage in the preparation of linear unsaturated polyester with high molecular mass. The result of mechanical properties indicated that cB outperforms 1, 4-butanediol in regard to enhancing the mechanical property of polyesters. Satisfactory thermal and crystal performances, broad processing window, as well as excellent mechanical properties were presented for PcBX, indicating that these synthetic biobased polyesters were promising candidates for replacing petroleum-based polyesters in practical application. Furthermore, an attempt was made to incorporate the functional group of hydroxyls in the backbones through “click reaction”, and the existence of free hydroxyls on the surface of PcBX results in their greatly improved hydrophilicity. The inserted hydroxyls greatly accelerated the degradation rate of polyesters. Overall, this paper not only offers a straightforward method for the preparation of high molecular mass unsaturated polyesters with adjustable performances, but also presents the potential of functionalization for a broad range of applications.

Hema-Functionalized Graphene Oxide: a Versatile Nanofiller for Poly(Propylene Fumarate)-Based Hybrid Materials

Poly(propylene fumarate) (PPF) is a linear unsaturated polyester which has been widely investigated for tissue engineering due to its good biocompatibility and biodegradability. In order to extend the range of possible applications and enhance its mechanical properties, current approaches consist in the incorporation of various fillers or obtaining blends with other polymers. In the current study we designed a reinforcing agent based on carboxylated graphene oxide (GO-COOH) grafted with 2-hydroxyethyl methacrylate (GO@HEMA) for poly(propylene fumarate)/poly(ethylene glycol) dimethacrylate (PPF/PEGDMA), in order to enhance the nanofiller adhesion and compatibility with the polymer matrix, and in the same time to increase the crosslinking density. The covalent modification of GO-COOH was proved by Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and Raman spectroscopy. The mechanical properties, water uptake capacity, morphology, biodegradability, mineralization and in vitro cytotoxicity of PPF/PEGDMA hybrid materials containing GO@HEMA were investigated. A 14-fold increase of the compressive modulus and a 2-fold improvement in compressive strength were observed after introduction of the nanofiller. Moreover, the decrease in sol fraction and solvent swelling in case of the hybrid materials containing GO@HEMA suggests an increase of the crosslinking density. SEM images illustrate an exfoliated structure at lower nanofiller content and a tendency for agglomeration at higher concentrations. Finally, the synthesized hybrid materials proved non-cytotoxic to murine pre-osteoblast cells and induced the formation of hydroxyapatite crystals under mineralization conditions.

Photoactive linear and hyperbranched polyesters based on 4-methylcyclohexanone and 4-tert-butylcyclohexanone moieties in the main chain: synthetic methodology, characterization and cytotoxicity

In this work, a variety of photoactive linear and hyperbranched unsaturated polyesters P1a-d, P2a-d and P3a-d, were successfully synthesized via ring-opening polymerization of diarylidene epoxy monomers 2a-d with terephthalic acid, isophthalic acid or trimesic acid in presence of TABI as a catalyst. First, diarylidene-epoxy monomers 2a-d were obtained from diols of diarylidene cycloalkanones derivatives 1a-d followed by epoxidation with epichlorohydrin in presence of NaOH and TBAI. These diaryldene epoxy monomers 2a-d were applied in the preparation of P1a-d, P2a-d and P3a-d. The molar masses of the resulting unsaturated polyesters were determined by gel permeation chromatography (GPC); all polymers have moderate molar masses. The photo-responsive properties of selected examples of polymers were tested in THF under UV lamp (450 nm) at different time intervals, This study revealed the occurrence of photocrosslinking behavior in the system under these conditions. The thermal properties of these polyesters were evaluated by thermogravimetric analysis (TGA). The morphological properties of selected examples of polymers were tested using scanning electron microscope (SEM). In addition, the cytotoxicity of the prepared monomers and selected polymers was tested against HeLa cervical cancer cells using MTT cell viability assay. All monomers except 2c showed significant cytotoxic effects with IC50 > 21 μM. In contrast, the tested polymers were less potent against HeLa cells.

The Unsaturated Polyester Via Ring-Opening Metathesis Polymerization (ROMP) of ω-6-Hexadecenlactone

Background: Ring opening metathesis polymerization of lactones using alkylidene catalysts is an alternative to obtain unsaturated linear polyesters with remarkable thermal and mechanical properties. Also, these polyesters have properties of biodegradability which opens up a wide range of applications as environmentally friendly thermoplastics and biomaterials. Objective: This research aims to present one route to obtain an unsaturated linear polyester poly(ω-6- hexadecenlactone) via ring opening-metathesis polymerization of ω-6-hexadecenlactone using the rutheniumalkylidene [Ru(Cl)2(=CHPh)(PCy3)2] (I), [Ru(Cl2)(=CHPh)(1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene)( PCy3)] (II) and [Ru(Cl2)(=CH(o-isopropoxyphenylmethylene))(1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene)] (III) and the ruthenium-vinylidene [RuCl2(=C=CH(p-C6H4CF3))(PCy3)2] (IV) catalysts. Conclusion: The high number-average molecular weights of the poly(ω-6-hexadecenlactone) between Mn = 114,800-155,400 g/mol and yields ranging from 96 to 98 % can be achieved by II and III catalysts. The catalysts II and III with the N-heterocyclic carbene ligand showed superior activity and stability upon catalysts I and IV bearing PCy3 ligands. The hydrogenation of poly(ω-6-hexadecenlactone) using Wilkinson catalyst [RhCl(PPh3)3] was studied. The percent crystallinity of the unsaturated poly(ω-6-hexadecenlactone) was 31% with a melting temperature 47.60ºC. Stress-strain measurements of several poly(ω-6-hexadecenlactone) were determined.

Effects of gate dielectric surface modification on phototransistors with polymer-blended benzothieno[2,3-b]benzothiophene semiconductor thin films

In the present work, we investigated effects of the dielectric/semiconductor interface modification on the photoelectrical properties of phototransistors comprising a UV responsive semiconductor blend 2,7-dipentyl-[1]benzothieno[2,3-b][1]benzothiophene (C5-BTBT) and a linear unsaturated polyester (L-upe). Using various self-assembly monolayers with different end-groups at the dielectric/semiconductor interface we modulated the drain photocurrent and response times under the UV light illumination of phototransistors. Treatment of the SiO2 dielectric surface with organosilanes led to the variation of the max mobility in the dark 0.10–0.18 cm2 V−1 s−1 and under UV light 0.08–0.50 cm2 V−1 s−1. Interestingly, detailed crystal structure analysis using 2D X-ray diffraction and photoelectrical characterization revealed that mobility in the dark predominantly depends on the alignment of C5-BTBT crystallites at the interface. Under UV light, the mobility increased with the electron withdrawing/donating nature of the SAM end-functional group. Additionally, chemical modification of the SiO2 dielectric surface increased photocurrent relaxation/decay times upon UV light removal while retaining fast response times when exposed to UV light, which enhanced memory properties of fabricated phototransistors (fast UV response = writing and long relaxation = long data storage).

Highly UV‐Sensitive and Responsive Benzothiophene/Dielectric Polymer Blend‐Based Organic Thin‐Film Phototransistor

It is reported on drain current modulation by UV light, in an organic thin‐film phototransistor, based on a small molecule semiconductor 2,7‐dipentylbenzo[b]benzo[4,5]thieno[2,3‐d]thiophene (BTBT‐C5) blended with a linear unsaturated polyester (L‐upe) to form the active channel material. The electrical properties of the phototransistor (L‐upe+BTBT‐C5) and physical properties of thin‐films are evaluated by means of two‐ and three‐terminal current–voltage characteristics (in the dark and under UV light) and structure–morphology analysis, respectively. Upon illumination with UV light, a dramatic change in the electrical properties of the L‐upe+BTBT‐C5 transistors is observed, compared to low responsive control transistors based on a blend of poly(methyl methacrylate) and BTBT‐C5. Drain current is increased by more than six orders of magnitude with maximum photosensitivity and responsivity of 4.0 × 106 and 11.1 A W−1, respectively, using a VG = 0 V. Modulated photoelectrical properties are explained by structure–morphology characteristics and efficient charge trapping at the polymer/semiconductor interface due to the presence of electron‐withdrawing groups in the polymer. Fast rise time of 1.80 s and slow relaxation time of 24.27 s, estimated using bi‐exponential fitting models, confirm a charge trapping/releasing mechanism and reveal sensing‐memory properties of the devices.

Evaluation of effective parameters for the synthesis of poly(propylene fumarate) by response surface methodology

ABSTRACTPoly(propylene fumarate) (PPF) is an unsaturated linear polyester, which was synthesized for potential applications in filling skeletal defects. The synthesis was carried out according to a two‐step polymerization reaction. In this research, a functional relationship among three reaction factors [temperature, reaction time, and stoichiometry of the monomers] in the PPF synthesis was established by responses of the surface methodology/central composite design (CCD). After that, on the basis of the responses of CCD [increasing intensity ratio of the CH/OH peaks in Fourier transform infrared (FTIR) spectra], designed substances were synthesized and analyzed by FTIR spectroscopy. The synthesized PPF, based on the optimized synthesis conditions from CCD, had a high molecular weight, low hydroxyl group content, and optimum viscosity. According to the CCD response, the best product was obtained through with a molar ratio of diethyl fumarate/propylene glycol/ZnCl2/hydroquinone of 1:3.5:0.01:0.002 and a 17‐h reaction time at 140°C. Eventually, the synthesized PPF was characterized by FTIR spectroscopy, NMR, and gel permeation chromatography analyses. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40932.

Development of a biodegradable bone cement for craniofacial applications

This study investigated the formulation of a two-component biodegradable bone cement comprising the unsaturated linear polyester macromer poly(propylene fumarate) (PPF) and crosslinked PPF microparticles for use in craniofacial bone repair applications. A full factorial design was employed to evaluate the effects of formulation parameters such as particle weight percentage, particle size, and accelerator concentration on the setting and mechanical properties of crosslinked composites. It was found that the addition of crosslinked microparticles to PPF macromer significantly reduced the temperature rise upon crosslinking from 100.3°C ± 21.6°C to 102.7°C ± 49.3°C for formulations without microparticles to 28.0°C ± 2.0°C to 65.3°C ± 17.5°C for formulations with microparticles. The main effects of increasing the particle weight percentage from 25 to 50% were to significantly increase the compressive modulus by 37.7 ± 16.3 MPa, increase the compressive strength by 2.2 ± 0.5 MPa, decrease the maximum temperature by 9.5°C ± 3.7°C, and increase the setting time by 0.7 ± 0.3 min. Additionally, the main effects of increasing the particle size range from 0-150 μm to 150-300 μm were to significantly increase the compressive modulus by 31.2 ± 16.3 MPa and the compressive strength by 1.3 ± 0.5 MPa. However, the particle size range did not have a significant effect on the maximum temperature and setting time. Overall, the composites tested in this study were found to have properties suitable for further consideration in craniofacial bone repair applications.

TOUGHNESS AND REINFORCEMENT OF LINEAR UNSATURATED POLYESTER RESINS BY UNSATURATED HYPERBRANCHED POLYMER AND MECHANISM ANALYSIS

Unsaturated hyperbranched polyester resin (UHPR) prepared by ourselves shows best comprehensive performance in linear unsaturated polyester resin (UP-191) curing system and is considered as a kind of toughness and reinforcement additive. The effect of molecular weight and content of the UHPR on the performance of the UHPR/UP-191 hybrid materials are discussed in detail, and their performance has maximum with the increase of content and molecular weight of UHPR. The impact strength of the hybrid materials containing 10–15 wt% UHPR-2 is 1.86 kJ/m2, and which almost is 1.69 times of UP-191 performance, furthermore, the tensile and flexural strength can also be enhanced about 45.71% and 23.66%, respectively. The fracture surface micrograph of hybrid materials show non micro-phase separation of the UHPR/UP-191 blends which facilitates an enhanced interaction to achieve excellent toughness and strength of the cured systems by SEM and the results also are explained by a novel situ reinforcing and toughening mechanism.

Succinic or glutaric anhydride modified linear unsaturated (epoxy) polyesters

The influence of the structure of succinic or glutaric anhydride modified linear unsaturated (epoxy) polyesters on the course of the cure reaction with styrene initiated by benzoyl peroxide (BPO) or the mixture of benzoyl peroxide/tetrahydrophthalic anhydride (BPO/THPA) or benzoyl peroxide/maleic anhydride, as well as viscoelastic properties and thermal behavior of their styrene copolymers have been studied by DSC, DMA, and TGA analyses. Additionally, mechanical properties: flexural properties using three-point bending test and Brinell’s hardness for studied copolymers were evaluated. It was confirmed that the structure of used polyesters had a considerable influence on the course of the cure reaction with styrene, viscoelastic, thermal, and mechanical properties of prepared styrene copolymers. Generally, one or two asymmetrical peaks for the cure reaction of succinic or glutaric anhydride modified linear unsaturated epoxy polyesters with styrene were observed. They were connected with various cure reaction, e.g., copolymerization of carbon–carbon double bonds of polyester with styrene, thermal curing of epoxy groups, polyaddition reaction of epoxy to anhydride groups in dependence of used curing system. In addition, only one asymmetrical, exothermic peak attributed to the copolymerization process of succinic or glutaric anhydride modified linear unsaturated polyesters with styrene was visible. Moreover, the obtained styrene copolymers based on succinic or glutaric anhydride modified linear unsaturated epoxy polyesters were characterized by higher values of \( E_{{20\,^{\circ}{\text{C}}}}^{\prime} \), T g, E″, ν e, E mod, F max, hardness, IDT, FDT but lower e − F max compared to those values observed for styrene copolymers prepared in the presence of succinic or glutaric anhydride modified linear unsaturated polyesters. This supported to the production of stiffer and more thermally stable polymeric structure of copolymers based on unsaturated epoxy polyesters. Moreover, the copolymers prepared in the use of glutaric anhydride modified linear unsaturated (epoxy) polyesters were described by lower values of \(E_{{20\,^{\circ}{\text{C}}}}^{\prime} \), T g, E″, ν e, E mod, F max, hardness, IDT, FDT but higher e − F max than those based on succinic anhydride modified linear unsaturated (epoxy) polyesters. The presence of longer aliphatic chain length in polyester’s structure leads to produce more flexible network structure of styrene copolymers based on glutaric anhydride modified linear unsaturated (epoxy) polyesters than those based on succinic anhydride modified linear unsaturated (epoxy) polyesters.

Study of dynamics of the cross-linking process of hyperbranched polymers

The description of polymer relaxation properties makes it possible to characterize the influence of polymer structure on its useful properties, i.e., stability and resistance. To determine the profile of the relaxation properties of the linear, hyperbranched and dendrite unsaturated polyester resins, the synthesis of the oligoester as the model compounds was performed. The structures of the obtained model compound were confirmed by elemental analysis and 1H NMR and FTIR spectroscopy. The determination of the α relaxation processes for model oligoester allowed us to describe the practical properties of commercial compounds. The description of the relaxation process may facilitate the interpretation of the dependence between useful properties of polyesters and their molecular structure. The results of the experiments allowed us to improve the technology of the synthesis processes and to extend the range of their usage.

Biophysical studies on bone cement composites based on polyester fumarate

AbstractPolypropylene fumarate (PPF) as unsaturated linear polyester crosslinked with three different monomers namely N‐vinyl pyrrolidone (NVP), methyl methacrylate (MMA), and a mixture of NVP/MMA (1 : 1 weight ratio) were prepared. The chemical structure of the PPF was characterized by means of 1H‐NMR, FTIR, as well as GPC. The mixture of PPF resin with the crosslinking monomers filled with (60, 65, and 70 wt %) of gypsum were also prepared as bone cement composites. The dielectric measurements carried out on these prepared samples at frequency range from 100 Hz–100 kHz indicate that the permittivity ε′ and dielectric loss ε″ follow the order NVP &gt; NVP/MMA &gt; MMA. Both parameters were found to decrease by increasing the percentage of gypsum. According to Fröhlich and Havriliak Nagami functions, the relaxation times obtained could be attributed, respectively, to Maxwell‐Wagner effect and to the relaxation process related to carboxyl, hydroxyl, and ester functions associated with main chain. The latter relaxation time was found to increase by increasing gypsum content, whereas the electrical conductivity was found to decrease. The mechanical data of the investigated samples containing 60 wt % gypsum is characterized by the best properties and the behavior of the composites follows the order found in the case of dielectric properties (NVP &gt; NVP/MMA &gt; MMA). Formation of carbonate apatite of composite samples loaded with 60 wt % gypsum after immersing the samples for 4 weeks in simulated body fluid (SBF) was confirmed by the dielectric measurements and FTIR spectroscopy. In addition, the weight loss and the mechanical properties for such systems were also studied. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

The characterization of rheological properties of melt grafting polypropylene for foaming

Large enhancements of the melt strength of polypropylene (PP) were achieved by the introduction of specific unsaturated linear polyester (ULP) branches using melt grafting. The transient torque curves and optical rheology microscope images indicated that branching reactions took place and the ULP had been grafted onto the PP backbone. Shear rheological behaviors of three kinds of PP were investigated using rotational rheometer under dynamic shear mode with periodic shear rate. These PP samples are foamable PP (FPP) with sparse branches obtained by grafting ULP, commercial high melt strength PP (HMS PP) for foaming and conventional linear PP (EPS). It was found that the rheological properties of FPP, the HMS PP, were distinctly different from those of conventional PP. Storage modulus, steady state compliance and zero shear viscosity increased in comparison with EPS, while shear viscosity decreased. This result implied the presence of branching structures that was not revealed in conventional PP. In melt flow measurements, extrusion swell that was a prominent behavior of branching PP was observed also for FPP and PF. Compared to linear PP, FPP and PF showed distinct sag-resistant property and lower melt flow index. On the other hand, to estimate the extent of branching, a detailed method was applied using the obtained zero shear viscosity. The result showed that FPP was grafted by sparse ULP. From these results, it was found that FPP showed obvious enhancements in rheological behaviors similar to PF, although its melt strength was lower than that of PF due to the presence of shorter branching chains grafted on the backbone of FPP.

Study of the Cross-Linking Process of Model Oligoesters by DMTA Method

Some oligoesters were synthesized in order to study changes of the useful properties of hyper-branched unsaturated polyesters. The determination of the polymer relaxation properties allows for characterization of their structure. Useful properties of the polymers such as stability and persistence depend on their structure. The aim of the investigation was to obtain model oligoesters with low molecular weight and to study their properties by spectroscopic and the dynamic mechanical thermal analysis (DMTA) methods. The synthesis was performed with the use of ethylene glycol and the mixture of maleic anhydride and phthalic acid which allowed us to obtain linear unsaturated polyesters. The cross-linking process of synthesized model oligoesters was performed using styrene as a cross-linking agent. The NMR and IR spectroscopy and elemental analysis were used for the description of purity and the structure of the obtained products. Relaxation properties of the synthesized oligoesters, course of their cross-linking and relaxation properties of the cross-linked products were studied by DMTA methods. In the synthesized oligoesters and cross-linked products α and β-relaxation processes were observed.

Improving foamability of polypropylene by grafting modification

AbstractPolypropylene (PP) foam has been considered as a potential substitute for other thermoplastics foams in industrial applications. However, the key concern is the weak melt strength of PP, which leads to a high content of open‐cell structure in PP foams; and, thus, unsatisfactory for a number of applications. In this work, PP was modified by grafting with unsaturated linear polyester (ULP) in a twin‐screw extruder in attempt to improve the melt strength of PP. The grafting reaction on PP and the modified PP were characterized using FT‐IR, DSC, and TGA. The improved foamability was verified by SEM observation. In addition, the rheological behavior of modified PP was investigated using a Hakke rheometer. The results indicated that the melt strength of grafted PP was significantly enhanced, facilitating the foam formation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4114–4123, 2006

Poly( ε-caprolactone) + unsaturated isophtalic polyester blends: Thermal properties and morphology

Miscibility of blends composed by a linear unsaturated polyester (LUP) with poly( ε-caprolactone) (PCL) of different molecular weights ( M w = 50 × 10 3, 18 × 10 3 and 2 × 10 3) has been studied. The blends were subjected to different thermal treatments and have been studied by FT-IR spectroscopy, differential scanning calorimetry (DSC) and scanning electronic microscopy (ESEM). FT-IR results allow proving the miscibility of the blends at temperatures above the melting temperature of neat PCL. DSC measurements confirm the existence of a crystalline phase corresponding to neat PCL. The crystallization of PCL is observed in a wide range of blends composition, being detected in all the blend compositions when the crystallization time increases. Thermograms show clearly the glass transition temperatures of samples that have been rapidly quenched from the melt. However, the change in the heat flow corresponding to the glass transition temperatures is difficult to detect in samples with high PCL crystallization degree. The analysis of the results indicates that the morphology of the amorphous phase is heterogeneous for LUP + PCL blends and changes depending on the thermal treatment. The ESEM measurements, confirm the heterogeneity of the amorphous phase. The decrease of the molecular weight of the PCL favours the miscibility of the blends.

Preparation and Characterization of Polypropylene Grafted with ULP containing Europium as Photoluminescence Films

The films generating photoluminescence have unique properties for various applications. In this work, the chemical or covalent bonding between unsaturated linear polyester (ULP) containing rare earth Europium (Eu) complex (Eu-ULP) and polypropylene (PP) was introduced through a melt-grafting polymerization, which led to an improved approach for the preparation of photoluminescent films. Eu-ULP was synthesized, and then grafted onto PP in melt phase to render the resin fluorescence-active. The grafted PP was systematically characterized using various analytic tools including TG, IR, DSC, WAXS and fluorescence. The results indicated that Eu-ULP was covalently grafted onto polypropylene backbones. The findings from DSC and WAXS measurements revealed that Eu-ULP acted as a nucleating agent, increasing the crystallization rate effectively and destroying the integrity of crystalline as well.

Study on PP grafted with ULP containing rare earth

In this work, an improved approach for preparing the photoluminescence films was developed, in which the chemical or covalent bonding between unsaturated linear polyester (ULP) containing rare earth complex (Eu–ULP) and polymer was introduced through a melt-grafting polymerization. Eu–ULP was grafted onto polypropylene (PP) in melt phase to render the resin fluorescence-active. The grafted PP was systematically characterized using various analytic tools including TG, IR DSC, WAXS and fluorescence. The results indicated that Eu–ULP was successfully grafted to the polypropylene backbone. The findings from DSC and WAXS measurements revealed that Eu–ULP acted as a nucleating agent, increasing the crystallization rate effectively and destroying the integrity of crystallinity as well.

Linear unsaturated polyester + poly(ɛ-caprolactone) blends: Calorimetric behaviour and morphology

Blends of a linear unsaturated polyester (LUP, commercially named Al100) with poly(ɛ-caprolactone) (PCL) of different molecular weights have been studied. The miscibility and crystallinity have been analyzed through FT-IR spectroscopy, differential scanning calorimetry (DSC) and environmental scanning electronic microscopy (ESEM). All the blends were subjected to the same heat treatment consisting of crystallizing during 45 min at constant temperature (10, 20, 30 or 40 °C). The glass transition temperature, T g, and fusion temperature, T fus, have been determined in the whole composition range for each blend. The T g-composition dependence and the high degree of crystallinity detected at intermediate blend compositions denote an anomalous behaviour that could indicate the lack of homogeneity (phase separation) in the different blends studied. The ESEM measurements confirm the lack of homogeneity of the amorphous region in blends with high content of LUP. The results have been discussed as a function of the crystallization temperature and the molecular weight of PCL.