Eco-Friendly (co)Polyesters Containing 1,4-Cyclohexylene Units: Correlations between Stereochemistry and Phase Behavior

Nowadays the urgency for solving plastic waste problems is inducing academic and industrial research to develop novel environmentally friendly polymers, i.e. materials produced from alternative resources, with low energy consumption, non-toxic to the environment, and biodegradable. These biopolymers should have also good physical performances. In the field of aliphatic polyesters, novel (co)polymers, containing 1,4-cyclohexylene units, appear very promising materials, which are obtainable from biomass, potentially biodegradable and characterized by good mechanical properties. Moreover, these polyesters have the interesting peculiarity that their phase behavior is strictly connected to the ratio of the two possible configurations, cis and trans, of the cyclic units. Indeed, the trans isomer is more rigid and symmetric than the cis. Highly symmetrical units tend to improve the chain packing with a consequent increment in crystallinity and crystalline perfection. On the other hand, the cis isomer introduces kinks into the main chain, which hinder the formation of stable crystals. Thus, at high trans content the polyesters are characterized by relative high degree of crystallinity, whereas at low trans content the polymers are amorphous. Therefore, accordingly to the final cis/trans ratio, the phase behavior of the homopolymers and copolymers significantly changes and the stereochemistry of the cycloaliphatic units result to be a key factor to tailor the final thermal properties of the material. In this paper the properties of some homopolymers and copolymers, containing the 1,4-cyclohexylene units with different cis/trans ratio, are discussed just in terms of the correlations between stereochemistry and phase behavior

Bio-based (Co)polyesters Containing 1,4-Cyclohexylene Units: Correlations Between Stereochemistry and Phase Behavior

Nowadays the urgency for solving plastic waste problems is inducing academic and industrial research to develop novel environmentally friendly polymers, i.e. materials produced from alternative resources, with low energy consumption, non-toxic to the environment, and biodegradable. These biopolymers should have also good physical performances. In the field of aliphatic polyesters, novel (co)polymers, containing 1,4-cyclohexylene units, appear very promising materials, which are obtainable from biomass, potentially biodegradable and characterized by good mechanical properties. Moreover, these polyesters have the interesting peculiarity that their phase behavior is strictly connected to the ratio of the two possible configurations, cis and trans, of the cyclic units. Indeed, the trans isomer is more rigid and symmetric than the cis. Highly symmetrical units tend to improve the chain packing with a consequent increment in crystallinity and crystalline perfection. On the other hand, the cis isomer introduces kinks into the main chain, which hinder the formation of stable crystals. Thus, at high trans content the polyesters are characterized by relative high degree of crystallinity, whereas at low trans content the polymers are amorphous. Therefore, accordingly to the final cis/trans ratio, the phase behavior of the homopolymers and copolymers significantly changes and the stereochemistry of the cycloaliphatic units result to be a key factor to tailor the final thermal properties of the material. In this paper the properties of some homopolymers and copolymers, containing the 1,4-cyclohexylene units with different cis/trans ratio, are discussed just in terms of the correlations between stereochemistry and phase behavior

Effect of phosphorus based flame retardants on UL94 and Comparative Tracking Index properties of poly(butylene terephthalate)

Poly(butylene terephthalate) (PBT) is widely used for electrical and electronic devices as insulating material. For these applications PBT has to combine both good flammability and electrical properties (tracking resistance) measured, respectively, by UL94 and Comparative Tracking Index (CTI) tests. In this paper a simultaneous study of UL94 and CTI performances has been conducted on different PBT formulations with the addition of halogen-free flame retardants (diethylphosphinic acid aluminium salt (AlPi) and melamine polyphosphate (MPP)). A thermosetting resin (Ultem) has also been added. FTIR and TGA analyses have been used in order to relate the action of these additives to flammability and electrical properties. AlPi shows the best flame results achieving a V0 classification in UL94 test. On the other hand, melamine has the best performances in CTI tests. TGA and FTIR analyses show that AlPi acts in the condensed phase forming a consistent amount of char, while melamine acts in the gas phase and is not able to protect PBT during combustion

Eco-friendly (Co)polyesters Containing 1,4-cyclohexylene Units: Correlations between Stereochemistry and Phase Behavior

Nowadays the urgency for solving plastic waste problems is inducing academic and industrial research to develop novel environmentally friendly polymers, i.e. materials produced from alternative resources, with low energy consumption, non-toxic to the environment, and biodegradable. These biopolymers should have also good physical performances. In the field of aliphatic polyesters, novel (co)polymers, containing 1,4-cyclohexylene units, appear very promising materials, which are obtainable from biomass, potentially biodegradable and characterized by good mechanical properties. Moreover, these polyesters have the interesting peculiarity that their phase behavior is strictly connected to the ratio of the two possible configurations, cis and trans, of the cyclic units. Indeed, the trans isomer is more rigid and symmetric than the cis. Highly symmetrical units tend to improve the chain packing with a consequent increment in crystallinity and crystalline perfection. On the other hand, the cis isomer introduces kinks into the main chain, which hinder the formation of stable crystals. Thus, at high trans content the polyesters are characterized by relative high degree of crystallinity, whereas at low trans content the polymers are amorphous. Therefore, accordingly to the final cis/trans ratio, the phase behavior of the homopolymers and copolymers significantly changes and the stereochemistry of the cycloaliphatic units result to be a key factor to tailor the final thermal properties of the material. In this paper the properties of some homopolymers and copolymers, containing the 1,4-cyclohexylene units with different cis/trans ratio, are discussed just in terms of the correlations between stereochemistry and phase behavior

New polymers from renewable resources: synthesis, characterization, and photodurability of aliphatic polyesters containing glycerol

Aliphatic polyesters, synthesized from monomers obtainable from biomasses, are an interesting class of materials which combine excellent properties, such as biodegradability and biocompatibility, with quite poor physical properties and often high costs. For this reason modification of aliphatic polyesters have recently attracted considerable attention. In particular, by considering the poly(alkylene dicarboxylate)s, linear aliphatic polyesters synthesized by combination of diols with dicarboxylic acids, one of the possible strategies to improve the thermo-mechanical characteristics is the chemical modification of the macromolecular architecture, by addition of a multifunctional monomer. Here we present the results of the chemical modification of the poly(butylene dodecanoate), derived from 1,4- butanediol and 1,12-dodecanedioic acid, by addition of glycerol, a threefunctional alcohol, byproduct of the production of biodiesel. The synthesis of the novel polyesters, characterized by a glycerol content varying from 0.5 to 2.0 mol%, has been optimized. The analysis of the molecular structure, carried out by 1H NMR spectroscopy, and the chemical properties of the materials (for example, solubility) reveal a complex polymer network, due to the reactivity of all the \u2013OH groups of glycerol. Even if the thermal properties of the crystal phase seem not affected by the presence of the glycerol, the mechanical properties change with respect to those of the homopolymer. Moreover, as the materials, during their service life, can be submitted to photodegradation, as well as biodegradation and hydrolytic degradation, due to outdoor use, the durability is a property of great importance. Therefore, a study of the photodegradability of the novel polyesters has been carried out and attention has been paid on the molecular structure evolution upon photodegradation monitored by melt rheology. The different mechanisms occurring during photoageing, chain scissions and three-dimensional network formation, have been identified

Eco-friendly poly(butylene 1,4-cyclohexanedicarboxylate): relationships between stereochemistry an crystallization behavior

Poly(butylene 1,4-cyclohexanedicarboxylate) (PBCHD) is an environmentally friendly material, as it can be obtained from biomass (although nowadays it is prepared from petroleum resources) and is potentially biodegradable. Moreover, the aliphatic rings along the chains lend interesting characteristics, for example good mechanical properties and resistance to weather for outdoor applications. As many properties, such as biodegradability, strongly depend on crystallinity, a study of the crystallizability of PBCHDs is very meaningful. Equilibrium melting temperatures and crystallization rates are strongly affected by the cis/trans ratio of the 1,4-cyclohexylene units. Indeed, only the trans isomer can form crystals, whereas the cis isomer is fully excluded from the crystalline phase. All thermal data can be well understood by considering PBCHD as a random copolymer with crystallizable (trans isomer) and noncrystallizable (cis isomer) components, which only differ for the stereochemistry of the aliphatic rings

Eco-Friendly Aliphatic Polyesters Containing 1,4-Cyclohexane Dicarboxylate Units: Effect of Diol Chain Length on Thermo-Mechanical Properties

Aliphatic polyesters containing 1,4-cyclohexylene rings are an interesting class of materials, not yet fully investigated. They potentially have the good characteristics typical of biopolyesters (for example, polyalkylene dicarboxylates and polyhydroxy alkanoates), such as sustainability and biodegradability. Indeed, renewable biomass resources can be used as feedstock to prepare the monomers and some preliminary tests of biodegradation suggest that the aliphatic rings do not hinder the microorganism attack.1 Moreover, the presence of cyclohexyl groups into the main chain provides rigidity to macromolecular chains, raises Tg, and imparts desirable physical-mechanical properties. In this way, the problem of the poor mechanical properties generally found in aliphatic polyesters can be solved. Finally, the 1,4-cyclohexylene unit shows the other remarkable peculiarity that it can have two possible configurations, cis and trans. In a polymer containing the 1,4-cyclohexylene rings, it will suffice to slightly modify the cis/trans isomeric ratio to obtain materials whose phase behavior changes from fully amorphous to semicrystalline.2 Therefore, the final properties of these materials can be easily tailored according to the specific applications. In this work diols with different chain length were tested as monomers for novel polyesters and the effects of the molecular characteristics on final properties were analyzed

Transamidations in melt-mixed MXD6 and PA6I-6T polyamides: 1. Determination of the degree of randomness and block length by 1H-NMR analysis

The evaluation of the randomness degree and block length of polyamides after interchange reactions is a key issue to estimate the transamidation progress, which strongly influences the final properties of the materials. The polymers under examination are poly(m-xylylene adipamide) (MXD6) and poly(hexamethylene isophthalamide-co-terephthalamide) (PA6I- 6T). They were blended by extrusion and then treated in differential scanning calorimeter (DSC) in order to improve transamidations and copolymer formation. The molecular structure of the final materials was analysed by means of an efficient, new and fast method based on 1H NMR analysis. The results were compared to those obtained by the more widely used 13C NMR analysis

Environmentally friendly copolyesters containing 1,4-cyclohexane dicarboxylate units, 1- Relationships between chemical structure and thermal properties

Novel aliphatic, random copolyesters, containing co-units derived from a poly(alkylene dicarboxylate) and a poly(butylene 1,4-cyclohexanedicarboxylate), have been synthesized and characterized in terms of molecular structure and thermal properties. In particular, the effects of the molar composition, the length of the aliphatic sequences, and the cis/trans ratio of the 1,4-cyclohexylene units on the characteristics of the crystalline and amorphous phases are discussed. Some interesting structure-property relationships have been found. The materials result to be very promising new biopolymers as they are characterized by a potential biodegradability and good physical properties, which can be easily modified, according to the requests of specific applications, by little changes in the Molecular structure