Surfactants from Recycled Poly (ethylene terephthalate) Waste as Water Based Oil Spill Dispersants

Recycled poly (ethylene terephthalate), PET, can be modified to produce nonionic surfactants. Recycling of PET waste was carried out in presence of different weight ratios of diethanolamine and triethanolamine and manganese acetate as catalyst. The molecular weights of the prepared oligomers were calculated from hydroxyl number and determined from GPC measurements. The produced oligomers were reacted with polyethylene glycol, PEG, which have different molecular weights 400, 1000 and 4000. Interfacial tension and the effectiveness in oil dispersion of the synthesized surfactants were reported. It was found that, the maximum efficiency of oil spill dispersants was reached to maximum when the surfactant molecules ended with two PEG 1000 moities.     

Parallel DNA Synthesis on Poly(ethylene terephthalate)

The fabrication of DNA arrays directly on aminolyzed sheets of poly(ethylene terephthalate) (PET) is described. Array surfaces typically employ bifunctional linkers or layers of covalently attached polymers to provide substrate hydroxy groups as synthesis attachment points. An amine treatment is used here to expose hydroxy groups on films of PET. These hydroxy groups can then be used to couple phosphoramidites and initiate the array synthesis without further functionalization steps. Arrays fabricated on these substrates with a maskless array synthesizer are tolerant of the high number of chemical exposure steps required to synthesize relatively long oligonucleotides. The results might be of the greatest use to the synthetic biology community, for whom a flexible and robust substrate could enable new strategies to enhance the throughput of oligonucleotide synthesis.     

Synthesis and Characterisation of Branched Poly(ethylene terephthalate)

Branched poly(ethylene terephthalate)s (PET) were synthesised with a variety of molar masses and with a large range of degree of branching by introduction of mono-, tri-(glycerol) and tetra-functional (pentaerythritol) comonomers to dimethyl terephthalate and ethylene glycol. The monofunctional alcohols, dodecanol and benzyl alcohol, were used as terminating agents to minimise gelation. The effect of various reaction parameters, such as percentage glycerol or pentaerythritol and polymerisation time, on limiting viscosity number [η] and weight average molar mass (M_w) were investigated. The thermal behaviour of branched PET was studied by differential scanning calorimetry; all samples showed a characteristic double endothermic melting peak and the glass transition temperature was not observed. Some branched PETs were subjected to solid-state polymerisation to increase the molar mass of previously prepared branched polymers. The solid-state polymerisation technique showed that the process not only promoted the molar mass but, more importantly, it increased the crystallinity of the polymer. Overall, the solid-state reaction rate was governed by initial molar mass, crystallinity, reaction temperature and time. © of SCI.     

聚对苯二甲酸乙二醇酯合成催化剂研究进展

探讨了各类锑系催化剂、钛系催化剂(包括乙二醇钛)等不同类型的催化剂在聚酯缩聚反应中的催化性能研究的最新成果,指出在各种类型催化剂中,由于具有作为催化剂时不会带入多余的杂质进入反应体系等优点,乙二醇锑和乙二醇钛的应用前景较为广阔。     

支化聚酯的合成及热性能研究

通过直接酯化-缩聚工艺,在聚对苯二甲酸乙二醇酯(PET)聚合的缩聚过程中分别引入第三组分——3-羟甲基丙烷(TMP)、季戊四醇(PER)或双季戊四醇(DPT)合成了一系列不同的支化PET,并采用氢核磁共振波谱仪(1H-NMR)、差示扫描量热仪(DSC)和热重分析(TG)表征了产物的结构和性能。结果表明:与纯PET相比,经TMP、PER或DPT改性后的支化PET的玻璃化转变温度(Tg)均下降,含摩尔分数0.3%DPT改性的支化PET的Tg最低;除TMP1-PET外,各支化PET的冷结晶温度(Tc)都增大;各支化PET的熔点(Tm)也都呈现下降趋势;除PER3-PET外,各支化PET的结晶焓ΔHc都有所下降,而各支化PET的熔融焓ΔHm却变化不大;所得到的各支化PET具有较好的热稳定性能。     

Non-isothermal Crystallization of Poly(ethylene terephthalate) with Poly(oxybenzoate-p-trimethylene terephthalate) Copolymer

The influence of a poly(oxybenzoate-p-trimethylene terephthalate) copolymer, designated T64, on the non-isothermal crystallization process of poly(ethylene terephthalate) (PET) was investigated. All samples were prepared by solution blending in a 60/40 by weight phenol/tetrachloroethane solvent at 50°C. The solidification process strongly depended on cooling rate and composition of system. The crystallization rate of blends was estimated by crystallization rate parameter (CRP) and crystallization rate coefficient (CRC). From these results of CRP and CRC, it was predicted that the overall non-isothermal crystallization rate of PET would be accelerated by blending with 1–15 wt% of T64. The acceleration of PET crystallization rate was most pronounced in the PET/T64 blends with 5 wt% T64. The observed changes in crystallization behavior are explained by the effect of the physical state of the copolyester during PET crystallization as well as the amount of copolymer in the blends. An Ozawa plot was used to analyze the data of non-isothermal crystallization. The obvious curvature in the plot indicated that the Ozawa model could not fit the PET/T64 blend system well, and there was an abrupt change in the slope of the Ozawa plot at a critical cooling rate.     

PET/PTT共混聚酯的等温结晶行为

使用差示扫描量热仪(DSC)研究不同比例的PET/P1T共混聚酯在205℃的等温结晶行为,并使用Avrami方程对其等温结晶过程进行研究.结晶半周期t1/2,总结晶速率常数k和Avrami指数n的变化表明:在共混体系中,对于PET和PTT而言,另一组分的加入都会对结晶产生阻碍作用,PET与P1T相互影响成核与晶体生长机理.     

Chemical Recycling of Poly(ethylene terephthalate)

This paper covers the recent research carried out by the authors on the chemical recycling of poly(ethylene terephthalate) (PET) taken from post‐consumer soft‐drink bottles. The chemical recycling techniques used are critically reviewed and the authors' contribution is highlighted. Hydrolysis in either an alkaline or acid environment was employed in order to recover pure terephthalic acid monomer that could be repolymerized to form the polymer again. Alkaline hydrolysis was carried out in either an aqueous NaOH solution or in a non‐aqueous solution of KOH in methyl cellosolve. A phase‐transfer catalyst was introduced in alkaline hydrolysis, in order that the reaction takes place at atmospheric pressure and in mild experimental conditions. The reaction kinetics were thoroughly investigated, both experimentally and theoretically, using a simple, yet precise, kinetic model. Moreover, glycolysis was examined as an effective way for the production of secondary value‐added materials. The glycolysated PET products (oligomers) can be used as raw materials for the production of either unsaturated polyester resins (UPR) or methacrylated oligoesters (MO). UPR can subsequently be cured with styrene in ambient temperature to produce alkyd resins used as enamel paints or coatings. MO are potential monomers that can be cured either by UV irradiation or temperature to produce formulations used as coatings for wood surfaces, paints, or other applications. Thus, recycling of PET does not only serve as a partial solution to the solid‐waste problem, but also contributes to the conservation of raw petrochemical products and energy.

     

Structural investigation of Poly(ethylene terephthalate)/Poly(trimethylene terephthalate) transesterificated blends

Wide-Angle X-ray Diffraction (WAXD) and Small-Angle X-ray Scattering analyses were carried out to evaluate the evolution of the crystalline and supermolecular structure of poly(ethylene terephthalate) (PET) blended with poly(trimethylene terephthalate) (PTT). The conditions adopted in preparing the PET/PTT 50/50 blend induce transesterification between the polyesters; these reactions produce a new molecular characteristics based on PET/PTT copolymer that exhibits its own WAXD profile. The PET/PTT 50/50 copolymers prepared by melt mixing of the homopolymers for increasing times evidence spherulitic morphology and an evolution of the crystalline structure in terms of crystallinity and crystal dimensions. The periodicity of the transesterificated samples is intermediate between the long periods observed for pure PET and pure PTT. For the PET/PTT 50/50 copolymers the value of periodicity and lamellar thickness increase with the increasing of the processing time.     

Non-isothermal Crystallization Behavior of Poly(ethylene terephthalate)/Poly(trimethylene terephthalate) Blends

Summary Non-isothermal crystallization behavior of Poly(ethylene terephthalate)/Poly(trimethylene terephthalate) blends was investigated by XRD and DSC. By XRD spectra analysis, it could be concluded that PET and PTT crystals coexisted. They did not form the cocrystals due to different chemical structures. The Avrami equations modified by Jeziorny and Ziabicki’s kinetic crystallizability analysis were employed to describe the non-isothermal crystallization process of PET/PTT blends. The results suggested that the entanglement of the two polymer chains decrease the crystallizability of PET and PTT in blend. The crystallization activation energies of the blend evaluated by the Friedman method also indicated that the presence of two components in the blends hinders the crystallization process of both components.     

Studies on Hydrotalcite‐Catalyzed Synthesis of Poly(ethylene terephthalate)

Summary: The hydrotalcite‐catalyzed synthesis of PET was studied to clarify the effect of hydrotalcite properties on its catalytic activity. Hydrotalcite was modified by various treatments to tune its activity as a polycondensation catalyst. Hydrotalcite activity was found to decrease upon calcination. However, rehydration of the calcinated hydrotalcite resumed the catalytic activity. The hydrotalcite activity depends on the ratio of magnesium to aluminum cations in its composition, and highest activity occurs at a molar ratio of 2:1. Replacement of the carbonate anions of hydrotalcite by more nucleophilic ones like hydroxide and alkoxide groups resulted in improved catalytic activity. Hydrotalcite has two assembly orders: primary lamination of sheets into plates and secondary agglomeration of plates into particles. Hydrotalcite with larger sheet size showed lower activity. On the other hand, milling of hydrotalcite particles did not affect its activity as it probably enters the reaction on a plate level, which is not affected by milling. Polycondensation resulted in expansion of the hydrotalcite sheets under the effect of formed polymer. Reuse of hydrotalcite after polycondensation followed by depolycondensation resulted in a large activity enhancement.

High‐resolution SEM micrograph of calcinated HT after rehydration.     

Methanolsis of Poly(ethylene terephthalate) in Supercritical Phase

The depolymerization of poly(ethylene terephthalate, PET) in supercritical methanol is studied using a stainless stirred autoclave at temperature of 255~260℃, pressure of 8.5~14.0 MPa, and methanol/PET weight ratio of 3~8. Under the optimal conditions, the PET is depolymerized completely to its monomers in 60 min. The main products of the reaction are dimethyl terephthalate and ethylene glycol. There are still some small amounts of byproducts, such as methyl–(2-hydroxyethyl) terephthalate, bis(hydroxyethyl) terephthalate, dimers and oligomers. Reversed-phase high performance liquid chrom- atography and gas chromatography are used to analyze solid products and liquid products respectively. The results of depolymerization show that the yield of dimethyl terephthalate and the degree of PET depolymerization are dependent on the reaction temperature, weight ratio of methanol to PET and reaction time. But the reaction pressure has little influence on the depolymerization as long as methanol is in supercritical state.     

Methanolysis of Poly（ethylene terephthalate）in Supercritical Phase

1 INTRODUCTIONPoly(ethylene terephthalate), commonly known as PET polyester, is extensively used for making synthetic fibers and package containers. The volume of PET consumed is rising by year, and thus the chemical recycling and reuse of waste PET are drawing much attention for the preservation of resources and the protection of environment. Through chemical recycling, waste PET is depolymerized into its valuable monomers such as dimethyl terephthalate (DMT), bis (hydroxyethyl) ter…     

Nanofibrillar Single Polymer Composites of Poly(ethylene terephthalate)

Using the experience gained from the development of polymer–polymer nanofibrillar composites (NFCs), an attempt was undertaken to manufacture PET single polymer nanofibrillar composites. For this purpose polypropylene (PP) was removed by selective extraction from a knitted textile manufactured with PP/PET (80:20 by wt) blend. The remaining PET nanofibrillar textile was then sandwiched between lower‐melting PET films and compression molded at 120 °C. The obtained PET single polymer NFCs comprised PET nanofibrils as reinforcement and showed an improvement in the tensile strength and modulus of 37–100 and 40–140%, respectively (depending on the annealing temperature after compression molding and the test direction) compared to those of the starting isotropic matrix film.

     

Preparation of Poly(ethylene terephthalate)/Poly(amino ether) Blends by means of the Addition of Poly(butylene terephthalate)

Summary: Blends based on poly(ethylene terephthalate), PET, with poly(amino ether) (PAE) contents up to 40% were obtained by the addition of 20% poly(butylene terephthalate) (PBT) to the PET matrix. PBT mixed with PET led to a decrease in the T_m of the matrix that was enough to produce homogeneous blends by mixing in the melt state. Despite the presence of a single peak observed by dynamic‐mechanical analysis, the blends were biphasic, with amorphous phases in which minor amounts of the other component, both reacted and mixed, were present. This presence of minor components gave a fine morphology and significant adhesion that, together with the higher orientation of PAE in the blends, produced blends with a clear synergism in the modulus of elasticity, notched impact strength similar to that of the neat components, and high ductility up to 30% PAE.

Young's modulus of the PET‐PBT/PAE blends.     

Poly(ethylene terephthalate)/cellulose blends

Amorphous poly(ethylene terephthalate) (PET) and cellulose blends in film form were obtained by room temperature hydrolysis of PET/cellulose trifluoroacetate solution cast films. Evidence is presented indicating that the cellulose, or the water associated with it, nucleates the crystallization of the PET during differential scanning calorimetry (DSC) runs. At about the 50/50 composition, a phase inversion, from continuous PET to continuous cellulose appears. Hydrolysis and/or annealing in water at the boil yields a mixture of cellulose II and cellulose IV. The nature of the cellulose appears to be different in the case of the room temperature hydrolyzed structures. Hydrolysis appears to proceed more readily when the films are richer in the cellulose component.     

Mechanical Relaxation in Solid-state Polymerized Poly(ethylene terephthalate)

Abstract

The dynamic mechanical tensile properties, storage modulus E′ and loss modulus E″, of the amorphous and semi-crystalline PET samples, ranging in molecular weight from 15,000 to 300,000 g/mol, were measured over temperature T range from 150°C to +250°C at four frequencies v=3.5, 11, 35 and 110 Hz. The samples with molecular weight larger than 15,000 were produced by solid-state polymerization in high vacuum. An increase in the height of loss β-peak, at T= ?60… -30°C, with an increase in molecular weight was found both in the amorphous and semi-crystalline PET. On the other band, the height of loss β-peak for the amorphous samples appeared to be smaller in comparison with that for the semi-crystalline samples. By contrast, the height of loss δ-peak, at T= + 90. +110°C, for the amorphous samples was larger than for the semicrystalline samples. An increase in the E value with an increase in the molecular weight of the amorphous polymer was accompanied by an increase in the E″ value. This behavior was explained by the effective interpenetrated network of the high-molecular-weight polymer and better short-range ordering in the low-molecular-weight polymer. The intensity of the β-process was found to weaken with an increase in the chain ends concentration in both the amorphous and semi-crystalline samples. This result indicates that there is no contribution of the chain ends to the process of β-relaxation in PET.     

Effects of pH and Neutral Salts on the Adsorption of the Poly(ethylene glycol terephthalate) Condensates Toward Poly(ethylene terephthalate) Fiber

This study deals with the effects of pH and neutral salts on the adsorption of PET fiber with four kinds of poly(ethylene glycol terephthalate) condensated from dimethyl terephthalate (DMT) and poly(ethylene glycol) (PEG). The surface properties of the aqueous solution, the contact angle of polyol‐treated PET fabrics, and its parameters were also discussed. The pH of the solution or the adding of neutral salt in the polyol solution largely affected the contact angle of polyol‐treated PET fabrics as well as the surface tension of the solution. A lower pH of the polyol solution or adding neutral salts in the solution showed a lower surface tension and a lower contact angle that resulted in a better adsorption between polyol and poly(ethylene terephthalate) fibers. The lower pH of the solutions and a higher valence of the added neutral salt in the solution showed a largely positive effect on the adsorption parameters, and the order of effectiveness is Al₂(SO₄)₃ > MgSO₄ > Na₂SO₄.     

Poly(ethylene terephthalate) blends for permeability barrier applications

Poly(ethylene terephthalate) (PET) offers good properties as a material of choice for various packaging, electronic, and other applications. In these applications in general, the PET articles achieve improved toughness and other physical properties through molecular orientation resulting from stretching at temperatures slightly above its T_g. Without such orientation, these articles suffer from poor impact toughness. We have been investigating modifications of PET for improving toughness and retaining the permeability properties. PET having intrinsic viscosities of 0.5 to 0.7 have been modified with low modulus polymers, particularly ethylene copolymers such as ethylene-methacrylic acid (EMAA) copolymers. The effect of crystallinity on toughness was determined. The crystallinity was established by Differential Scanning Calorimetry (DSC) techniques. Many of these modified PET compositions have good toughness and permeability barrier properties for various packaging and other controlled permeability applications such as containers and films.     

Synthesis and characterisation of copolyesters from poly(ethylene terephthalate) and poly(hexamethylene terephthalate)

Copolyesters containing poly(ethylene terephthalate) and poly(hexamethylene terephthalate) (PHT) were prepared by a melt condensation reaction. The copolymers were characterised by infrared spectroscopy and intrinsic viscosity measurements. The density of the copolyesters decreased with increasing percentage of PHT segments in the backbone. Glass transition temperatures (T_g). melting points (T_m) and crystallisation temperatures (T_c) were determined by differential scanning calorimetry. An increase in the percentage of PHT resulted in decrease in T_g, T_m and T_c. The as-prepared copolyesters were crystalline in nature and no exotherm indicative of cold crystallisation was observed. The relative thermal stability of the polymers was evaluated by dynamic thermogravimetry in a nitrogen atmosphere. An increase in percentage of PHT resulted in a decrease in initial decomposition temperature. The rate of crystallisation of the copolymers was studied by small angle light scattering. An increase in percentage of PHT resulted in an increase in the rate of crystallisation.