Synthesis, Characterization, and Hydrolytic Degradation of Copolymers of 2-Methylene-1,3-dioxepane with Ethylene and with Styrene

2-Methylene-1,3-dioxepane (MDP) was copolymerized with ethylene (E) at a pressure of approximately 1000 psi and a temperature of approximately 70°C with AIBN as the free radical initiator. The copolymers obtained, poly(MDP-co-E), were characterized by elemental analysis, IR, ¹H-NMR and ¹³C-NMR spectroscopy, DSC, and GPC. The copolymers contained 2–15 mol% ester units. MDP was also copolymerized with styrene (S) at 120°C with di-t-butyl peroxide as the initiator to prepare the copolymer, poly(MDP-co-S). The number-average molecular weights of both types of copolymers were in the range of 6000 to 11,000, and the weight-average molecular weights were in the range of 9000 to 17,000. The melting temperatures of poly(MDP-co-E) decreased with increasing ester unit content in the copolymer. For the MDP-S copolymers, the glass transition temperatures decreased with increasing ester unit content. Both poly(MDP-co-E) and poly(MDP-co-S) were degraded by methanolysis, and their molecular weights decreased by the expected amounts based on the ester unit content.     

Biodegradable Polyesters and Polyamides From Difunctionalized Lauric and Coconut Fatty Acids

In this work, a major fatty acid from coconut oil was used as starting material in preparing biodegradable polymers. Thus, polyesters and polyamides from varying proportions of monomers, hydroxy- and amino- derivatives of lauric acid were synthesized. Initially, the derivatives were prepared by regioselective chlorination of lauric acid, in the presence of ferrous ions in strong acid medium. Subsequent hydroxylation and amination procedures yielded the hydroxy- and amino- derivatives of lauric acid. These monomers were polymerized in a reaction tube by simple polycondensation method at 220–230 °C for 6–8 h without catalyst. Molecular weight determination using –COOH by end group titration and gel permeation chromatography (GPC) gave an average molar mass of 3,000–5,000 g mol⁻¹ with n = 15–25 monomer units. Thermal properties such as glass transition (T_g) and decomposition (T_d) temperatures were obtained using differential scanning calorimetry (DSC). The same processes of synthesis and determinations above were applied to coconut fatty acids, derived from saponification of coconut oil, and resulted to very similar conclusions. A quick biodegradation assay against fungus Aspergillus niger UPCC 4219 showed that the polymers prepared are more biodegradable than conventional plastics such as polypropylene, poly(ethyleneterepthalate) and poly(tetrafluoroethylene) but not as biodegradable as cellulosic (newsprint) paper.     

Effect of Lignosulfonate on the Thermal and Morphological Behavior of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

The effect of lignosulfonate on poly(3-hydroxybutyrate-co-3-hydroxyvalerate), PHBV, was studied by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The PHBV/lignosulfonate samples were prepared by melt mixing in an internal mixer. SEM showed that PHBV/lignosulfonate samples present a cracked surface that is more intense in mixtures with high lignosulfonate proportions. According to DSC, melting and glass transition temperatures of the PHBV matrix decrease with lignosulfonate addition. The same effect was observed for melting enthalpies (ΔH_m), which indicates a decrease of crystallinity. TGA showed that thermal stability of PHBV/lignosulfonate samples was shifted to lower temperatures, which indicates the existence of an interaction between the thermal decomposition processes of PHBV and lignosulfonate.     

Bacterial degradation of a new polyester,polyethylene glycol-phthalate polyester

Microorganisms which can assimilate a new polyester synthesized from polyethylene glycol (PEG) as a dihydroxyl compound and phthalic acid as a dicarboxyl compound were isolated from soils by enrichment culture techniques. Two cultures, K and N, were obtained: Culture K grew on PEG 4000 polyester and culture N assimilated PEG 6000 polyester. Each culture included two bacteria indispensable for the degradation of polyesters: bacteria K1 and K2 for PEG 4000 polyester-utilizing culture K and bacteria N1 and N2 for PEG 6000 polyester-utilizing culture N. Bacteria K2 and N2 were responsible for the hydrolysis of ester bonds in a polyester and both were identified as the same species,Comamonas acidovorans. Bacteria K1 and N6 could assimilate PEG as a sole carbon and energy source. Both are Gram-negative, non-spore-forming rods and resembled each other on their colony characteristics, although strain K1 could not grow on PEG 6000.C. acidovorans N2 (K2) grew on dialkyl phthalates (C₂–C₄) and phthalate and tributyrin, but not on PEG, diphthalic PEG, and PEG phthalate polyesters. Their culture supernatant and washed cells hydrolyzed PEG (400–20,000) phthalate and sebacate polyesters.C. acidovorans had higher esterase activity toward PEG phthalate, isophthalate, and terephthalate polyesters than known esterase and lipases. The esterase seemed to be an extracellular one and attached to the cell surface.     

Improved method for the formation of recycled resins from depolymerized products of waste fiber-reinforced plastics: simple and effective purification of recovered monomers by washing with water

The synthesis of recycled plastics from recovered monomeric materials obtained from the depolymerization reaction of fiber-reinforced plastics (FRP) was examined. The depolymerization reaction of FRP in the presence of N,N-dimethylaminopyridine (DMAP) smoothly yielded the corresponding monomers, which mainly consisted of dimethyl phthalates. The polymerization reaction with this monomer failed to form the corresponding unsaturated polyesters due to contamination by N-methyl-4-pyridone, a decomposition product of DMAP. An efficient purification of the recovered monomer was achieved by washing with water, and the purified monomer successfully yielded the corresponding polymers. A hardness test revealed that the polymers were as hard as the polyester made from virgin materials. The present modification provides a practical method for the preparation of recycled plastics from depolymerized plastics.     

Construction, Characterization and Biological Activity of Chiral and Thermally Stable Nanostructured Poly(Ester-Imide)s as Tyrosine-Containing Pseudo-Poly(Amino Acid)s

In this paper we studied the synthesis of biodegradable optically active poly(ester-imide)s containing different amino acid residues in the main chain. These pseudo-poly(amino acid)s were synthesized by polycondensation of N,N′-(pyromellitoyl)-bis-l-tyrosine dimethyl ester as a diphenolic monomer and two chiral trimellitic anhydride-derived diacid monomers containing s-valine and l-methionine. The direct polycondensation reaction of these diacids with aromatic diol was carried out in a system of tosyl chloride (TsCl), pyridine (Py) and N,N′-dimethylformamide (DMF) as a condensing agent. The structures and morphology of these polymers were studied by FT-IR, ¹H-NMR, powder X-ray diffraction, field emission scanning electron microscopy (FE-SEM), specific rotation, elemental and thermogravimetric analysis (TGA) techniques. TGA profiles indicate that the resulting PEIs have a good thermal stability. Morphology probes showed these polymers were noncrystalline and nanostructured polymers. The monomers and prepared polymers were buried under the soil to study the sensitivity of the monomers and the obtained polymers to microbial degradation. The high microbial population and prominent dehydrogenase activity in the soil containing polymers showed that the synthesized polymers are biologically active and microbiologically biodegradable. Wheat seedling growth in the soil buried with synthetic polymers not only confirmed non-toxicity of polymers but also showed possibility of phyto-remediation in polymer-contaminated soils.     

Effects of Saturated Acids on Physical Properties of UPE Resins Prepared from Recycled PET Products

In this study, effects of saturated acids on physical properties, including hardness, impact strength, flexural properties and thermal properties, of unsaturated polyester or UPE resins prepared from recycled PET bottles and fabrics were investigated. PET was depolymerized by glycolysis reaction with the excess propylene glycol in the presence of zinc acetate as a catalyst. UPE resins were then synthesized by polyesterification of these glycolyzed products with maleic anhydride as an unsaturated diacid as well as succinic acid and adipic acid as a saturated diacid. With the addition of styrene monomer, UPEs were subsequently casted into specimens by crosslinking reaction using methyl ethyl ketone peroxide and cobalt octoate as an initiator and a catalyst, respectively. Physical properties of the cured specimens were then studied. The results showed that, when a saturated acid was incorporated, the hardness of the cured UPE resins decreased due to the decreasing amount of crosslinks. The extended distance between crosslinking sites on molecular chains facilitated load distribution, resulting in the significant improvement of impact strength. The flexural strength was also improved when the small amount of saturated acid was used. The onset thermal degradation temperatures and the glass transition temperatures of the prepared UPE resins were almost unchanged.     

Biodegradability of degradable plastics exposed to anaerobic digested sludge and simulated landfill conditions

The biodegradabilities of various plastics by anaerobic digested sludge were measured and compared with the biodegradabilities under simulated landfill conditions. Bacterial poly(3-hydroxy-butyrate-co-3-hydroxyvalerate) (PHB/HV; 92/8, w/w), a natural aliphatic polyester, degraded nearly to completion within 20 days of cultivation by anaerobic digested sludge, while synthetic aliphatic polyesters such as poly-lactic acid, poly(butylene succinate), and poly (butylene succinate-co-ethylene succinate) did not degrade at all in 100 days. Cellophane, which was used as a control material, exhibited a similar degradation behavior to PHB/HV. Under simulated landfill conditions, PHB/HV degraded quite well within 6 months. Synthetic aliphatic polyesters also showed significant weight losses through 1 year of cultivation. The acidic environment inside simulators generated by the degradation of biodegradable food wastes which comprised 34 % of municipal solid waste seems to cause the weight loss of synthetic aliphatic polyesters.     

Biodegradable Polymers from 5-Hydroxylevulinic Acid: 1. Synthesis and Characterization of Poly(5-hydroxylevulinic acid)

As an attempt to synthesize new biodegradable polymers from renewable cellulose resources, melt polycondensation of 5-hydroxylevulinic acid (5-HLA) was reported for the first time. The resulting product, poly(5-hydroxylevulinic acid) (PHLA), was synthesized and characterized with GPC, FTIR, ¹H NMR and DSC. The in vitro degradation behaviors in phosphate-buffered saline (PBS) and in deionized water (DW) were also examined. The molecular weight of PHLA is not high (several 1,000s), but it possesses unordinary high glass transition temperature (as high as 120 °C). This is very different from existing aliphatic polyesters that usually have T _gs lower than 60 °C. The high T _g is attributed to the formation of inter- and/or intramolecular hydrogen bonds due to a characteristic keto–enol tautomerism equilibrium in the polymer structure. PHLA readily degraded hydrolytically in aqueous media.     

One-Pot Reaction of Waste PET to Flame Retardant Polyurethane Foam,via Deep Eutectic Solvents-Based Conversion Technology

Depolymerization of polyethylene terephthalate (PET) is a promising technology for producing recycled monomers. Using a deep eutectic solvent (DES)-based catalyst, the PET glycolysis process produces bis-(2-hydroxyethylene terephthalate) (BHET). This recycled monomer reacts with isocyanate and forms polyurethane foam (PUF). The DES-based one-pot reaction is advantageous because it is a low-energy process that requires relatively lower temperatures and reduced reaction times. In this study, choline chloride/urea, zinc chloride/urea, and zinc acetate/urea based DESs were adopted as DES catalysts for glycolysis. Subsequently, the conversion of PET, BHET yield, and OH values were evaluated. Both filtered and unfiltered reaction mixtures were used as polyols for PUF polymerization after characterization of the acid and hydroxyl values of the polyols, as well as the NCO (–N=C=O) value of isocyanate. In the case of unfiltered reaction mixtures, PUF was obtained via a one-pot reaction, which exhibited higher thermal stability than PUF made from the filtered polyols. This outcome indicated that oligomeric BHET containing many aromatic moieties in unfiltered polyols contributes to the thermal stability of PUF. This environmentally friendly and relatively simple process is an economical approach for upcycling waste PET.

     

New biodegradable polyester-copolymers from commodity chemicals with favorable use properties

Copolyesters composed of aliphatic and aromatic compounds were synthesized by the polycondensation of 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol, sebacic acid, adipic acid, and terephthalic acid. By applying an appropriate ratio of aliphatic to aromatic acids, the synthesized materials proved to be biodegradable, as was verified by several degradation test methods such as aqueous polymer suspension inoculated by a soil eluate (Sturm test), a soil burial test (at ambient temperature), and a composting simulation test at 60°C. The degradability of the polyester-copolymers (measured as weight loss) was investigated with respect to the aliphatic monomer components and the fraction of terephthalic acid. Excellent biodegradability was observed even for copolymers with a content of terephthalic acid up to 56 mol% (of the acid fraction) and melting points in the range up to 140°C. Degradation by chemical hydrolysis of the polyesters was determined independently and was found to facilitate microbial attack significantly only at higher temperatures. The findings demonstrate that biodegradable polymers with advantageous usage properties can easily be manufactured by conventional techniques from commodity chemicals (adipic acid, terephthalic acid, and ethylene glycol or 1,4-butanediol).Dedicated to Prof. J. Klein's 60th birthday.     

Thermal Properties and Crystallization Behavior of Novel Biodegradable Poly(hexamethylene succinate-<Emphasis Type="Italic">co</Emphasis>-6 mol% butylene succinate) and Poly(hexamethylene succinate)

In this research, the thermal properties and crystallization behavior of novel poly(hexamethylene succinate-co-6 mol% butylene succinate) (PHBS) and its homopolymer poly(hexamethylene succinate) (PHS) were extensively studied. With respect to PHS, the introduction of a small content of butylene succinate (BS) unit slightly reduces the melting point and equilibrium melting point but hardly influences the glass transition temperature of PHBS. Despite crystallization temperature, PHS and PHBS crystallize through the same crystallization mechanism. At the same crystallization temperature, PHBS crystallizes more slowly than PHS; furthermore, lowering crystallization temperature enhances the crystallization rates of PHBS and PHS. The spherulites morphologies were observed for both of them, with the spherulites nucleation density of the copolymer being smaller than that of the homopolymer. PHBS and PHS share the same crystal structures, indicative of the location of BS unit in the amorphous region.     

Accumulation of poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid-co-4-hydroxyvaleric acid) by mutants and recombinant strains ofAlcaligenes eutrophus

Alcaligenes eutrophus accumulated a terpolyester of 3-hydroxybutyric acid (3HB), 3-hydroxyvaleric acid (3HV), and 4-hydroxyvaleric acid (4HV) during cultivation with 4HV as carbon and energy source under nitrogen starvation. The polyester accumulated by wild-type strains under these conditions contained 4HV at a molar fraction of approximately 5 mol% only. A catabolic pathway of 4HV was postulated, which included the activation of 4HV to 4HV-CoA and a conversion of 4HV-CoA to 3HV-CoA. Tn5::mob-induced mutants were isolated fromA. eutrophus HF39, which were affected in 4HV and/or valeric acid catabolism. Among 83 mutants were 27 4HV-negative or 4HV-leaky mutants; two mutants were identified which accumulated a terpolyester with a molar fraction of 10.1 to 22.7 mol% 4HV. In addition, a further increase in the molar fraction of 4HV in poly(3HB-co-3HV-co-4HV) and a two- to fourfold increase in the PHA synthase activity were monitored in these mutants or others and also in HF39, if the cells were complemented with the hybrid plasmid pHP1014::PP1, which contained the PHA biosynthesis genes ofA. eutrophus H16. Application of mutagenesis plus recombinant DNA techniques resulted in the accumulation of a terpolyester with up to 30 mol% 4HV and with approximately equimolar fractions of 3HB, 3HV, and 4HV.     

Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate)/Polylactide Blends: Thermal Stability,Flammability and Thermo-Mechanical Behavior

Blends of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and polylactide (PLA) with different PHBV/PLA weight ratios (100/0, 75/25, 50/50, 25/75, 0/100) were prepared by melt compounding. Their mutual contributions in terms of thermal stability, flammability resistance, mechanical properties and rheological behavior were investigated. The study showed that the increase in PLA content in PHBV/PLA blends leads to enhanced properties. Consequently, thermal stability and flammability resistance were improved. Further, the rheological measurements indicated an increase in storage modulus and loss modulus of PHBV matrix by addition of PLA.     

Depolymerization of Waste PET with Phosphoric Acid–Modified Silica Gel Under Microwave Irradiation

Chemical recycling of waste poly(ethylene terephthalate) (PET) using phosphoric acid–modified silica gel as a solid catalyst is reported. Advantageously, microwave irradiation was used to progress the depolymerization of PET. In this study, depolymerization of PET with a small amount of water is suggested as a suitable method. The depolymerized product, terephthalic acid was obtained and assigned by ¹H NMR and FT-IR spectroscopy. Finally, over 90 % conversion to terephthalic acid was achieved when waste plastic bottles were treated with the method. This results confirm the importance of the microwave power technique as a promising recycling method for plastic bottles made from PET, resulting in monomer recovery in addition to substantial energy saving.     

Novel Bioactive Chiral Poly(amide–imide)s Containing Different Amino Acids Linkages: Studies on Synthesis, Characterization and Biodegradability

In this paper chiral bioactive poly(amide–imide)s (PAI)s were synthesized from four different diacids containing chiral amino acids with 4,4′-methylene bis(3-chloro 2,6-diethylaniline) as a diamine via direct polycondensation reaction in a system of tetra-n-butylammonium bromide and triphenyl phosphite as a condensing agent. The structures of these polymers were confirmed by FT-IR, ¹H-NMR, specific rotation, elemental and thermogravimetric analysis (TGA) techniques. TGA showed that the 10 % weight loss temperature in a nitrogen atmosphere was more than 378 °C, which indicates that the resulting PAIs have a good thermal stability. The biodegradability of the monomers and prepared polymers was investigated in culture media and soil burial test for assessment of the susceptibility of these compounds to microbial degradation. The results showed that the synthesized monomers and theirs derived polymers are biologically active and nontoxic to microbial growth.     

Poly[(R)-3-hydroxy butyrate] Melt Processing: Strategy for Prevention of Degradation Reactions

Poly[(R)-3-hydroxy butyrate] (PHB) as well as all the components of the poly[(R)-3-hydroxy alkanoate]s (PHAs) family tend to degrade during processing at temperatures above their melting point via a hydrolytic mechanism induced by moisture attack and a concerted reaction mechanism induced by temperature. Therefore, the PHAs stabilization in the molten state is particularly important for production of biodegradable ecocompatible plastic items of commercial value. In order to refrain the indicated negative degradation effects, PHB was melt processed in a torque rheometer in the presence of a polymeric carbodiimide agent. Processed specimens were characterized by using FTIR, GPC, DSC, TGA and tensile properties. GPC analysis showed that the increase of the additive content in the formulation resulted in an increase of PHB molecular weight. However, decreasing in PHB thermal stability, glass transition temperature and mechanical properties, was observed with the increase of the additive amount. This behaviour most likely arises from the formation of new chemical structures promoted by the presence of the additive aimed at preventing the onset of hydrolitic processes.     

Environmentally Friendly Oil-Modified Polyesters as Polymeric Plasticizers for Poly(vinyl chloride)

Oil-modified polyesters were synthesized to serve as polymeric plasticizers for PVC. A total of four polymeric plasticizers with different average molecular weights were prepared. Characterizations were done using Fourier-transformed infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, and gel permeation chromatography. Some of the tests conducted on PVC films include thermal stability test using thermogravimetric analyser, determination of glass transition temperature (T_g), plasticizer migration and leaching resistance test, morphology study of plasticized PVC films using field emission scanning microscope, toxicity test, and tensile test. Owing to the plasticizing effect of the palm oil-based compound, T_g of the plasticized PVC has decreased to an average of 65 °C at 20 wt% loading. The polymeric plasticizer is also able to contribute positively to the thermal stability and mechanical properties of the PVC films. Some of the advantages of incorporating polymeric plasticizer with high molecular weight includes lower rate of leaching from plastic, and improved tensile strength and elongation at break. Besides, thermal stability of the plastic studied using Kissinger’s and Flynn–Wall–Ozawa’s approaches shows that PVC blended with high molecular weight oil-modified polyester is more thermally stable, evidenced by the increase in the activation energy of decomposition, E_d. Toxicity test using brine shrimp egg shows encouraging results, where the oil-based plasticizer is considerably less toxic compared to some of the commercial plasticizers.     

A New Unsaturated Poly(ester-urethane) Based on Terephthalic Acid Derived from Polyethylene Terephthalate (PET) of Waste Bottles

The new unsaturated poly(ester-urethane) was synthesized by the reaction of 4,4??-methylenediphenyldiisocyanate with 4,4??-di(2,3-butenhydroxyl) terephthalate in the ratio of 1:1. 4,4??-di(2,3-butenhydroxyl) terephthalate was first prepared by reacting 2?mol of cis-2-butene-1, 4-diol with 1?mol of terephthalic acid. The terephthalic acid used was derived from the recycling of PET bottles via subjection to saponification process. The synthesized compounds were characterized by CHN analysis, FT-IR, ¹H NMR and UV?CVis spectroscopy, with consistency of results showing the presence of the new unsaturated poly(ester-urethane) II. Thermal properties of the new polymer was verified by differential scanning calorimetry and thermogravimetric analysis, whereas the mechanical properties were characterized by tensile, elongation, hardness, adhesion and impact testing. The electrical conductivity and the electrical resistance of the compound were observed with increasing applied voltage.     

Miscibility and Biodegradability of Poly(Butylene Succinate)/Poly(Butylene Terephthalate) Blends

As one of the biodegradable polymers, the blend of poly(butylene succinate) and poly(butylene terephthalate) is dealt with in this study. In our previous work, it was demonstrated that PBS and PBT are immiscible not only from the changes of T _g but also from logG–log G plots. It is expected that the biodegradability of the blends could be improved by enhancing the miscibility. We tried to induce the transesterification reaction between two polyesters with various time intervals to enhance the miscibility of the blends. The extent of transesterification reaction was examined by ¹H-NMR. We utilized a dynamic mechanical thermal analyzer and a rotational rheometer to investigate the changes in miscibility. We also verified the biodegradability of PBS/PBT blends after the transesterification reaction by the composting method.