Nanocellulose: Effect on Thermal, Structural, Molecular Mobility and Rheological Characteristics of Poly(Butylenes Adipate-Co-Butylene Terephthalate) Nanocomposites

The concern with environmental preservation is a very current and relevant topic. Regarding polymers, the search for potentially ecofriendly matters has been the subject of scientific research. In this context, this work aimed to study the effect of adding nanocellulose (nCE) with 1, 3, and 5 wt.% on poly(butylene adipate-co-butylene terephthalate) (PBAT). Thermal, structural, relaxometric, and rheological assessments were carried out. Quantitative evaluation of PBAT copolymer by high field NMR revealed 56.4 and 43.6 m.% of the butylene adipate and butylene terephthalate segments, respectively. WAXD measurement on the deconvoluted diffraction patterns identified that nCE was a mixing of Cellulose I and Cellulose II polymorph structures. At any composition, nanocellulose interfered with the PBAT crystallisation process. Also, a series of new PBAT crystallographic planes appeared as a function of nanocellulose content. PBAT hydrogen molecular relaxation varied randomly with nanocellulose content and had a strong effect on the hydrogen relaxation. PBAT cold crystallisation and melting temperatures (Tcc and Tm) were almost unchangeable. Although Tcc did not change during polymer solidification from PBAT molten state, the sample’s degree of crystallinity varied with composition through the transcrystallization phenomenon. Nanocomposite thermal stability decreased possibly owing to the catalytic action of sulfonated amorphous cellulose chains. For the sample with 3 wt.% of nanocellulose, the highest values of complex viscosity and storage modulus were achieved.

Nonisothermal Crystallization Kinetics of Poly(butylene adipate-co-terephthalate) Copolyester

Nonisothermal crystallization behavior of poly(butylene adipate-co-terephthalate)(PBAT) synthesized via direct esterification and polycondensation reactions was investigated by the differential scanning calorimetry(DSC).The Avrami equation modified by Jeziorny and the Z.S.Mo equation were employed to describe the non-isothermal crystallization kinetics of copolyester samples.The test results showed that the Avrami equation was successful in describing nonisothermal crystallization process of PBAT copolyesters.PBAT copolyester could give birth to secondary crystallization.The crystallization parameter(Zc) increased with an increasing cooling rate and the Avrami exponent(n) was around 2.3.For a given cooling rate,the value of Zc demonstrated a sagging trend with an increase in adipic acid(AA) content.The equation proposed by Z.S.Mo was successful in describing the nonisothermal crystallization kinetics of PBAT copolyesters.

Preparation and Properties of a New Type of Poly(butylene-terephthalate)with Layered Silicate Nanocomposites

In this paper, poly(butylene-terephthalate)-layered silicate of clay nanocomposites (NPBT) are reported. Their thermal properties, heat distortion temperature (HDT) and crystallization nucleation are investigated. NPBT samples have apparent viscosity over 0.85, HDT of 30℃ to 50℃ higher than that of poly (butyleneterephthalate) (PBT) for clay load from 1.0% to 10.0% (by mass), and higher capability to accommodate clay than other polymers. The nonisothermal crystallization experiments indicate that the better thermal degradation behavior and crystallization rate of NPBT are 50% higher than PBT, and its injection mould processing temperature is lowered from ll0℃ to 55℃. NPBT samples are characterized by several techniques. X-ray shows an original clay interlayer distance enlarged from 1.0 nm to 2.5 nm, while both TEM and AFM indicate an average size from 30nm to 100nm of exfoliated clay layers, and 3%(by mass) of particle agglomeration being phase separated from PBT matrix, which are factors on some mechanical properties decrease of NPBT. The disappearance of spherulitic morphology in NPBT resulted from layers nucleation is detected. Improving NPBT properties by treating clay with long chain organic reagent and controlling the way to load it is suggested.

DSC Study of Thermal Properties of Biodegradable Poly(Butylene Succinate-co-terephthalate)

Poly(butylene succinate) (PBS),poly(butylene terephthalate) (PBT) and poly(butylene succinate-co-terephthalate) (PBST)s were synthesized from dimethyl succinate and/or dimethyl terephthalate reacting with 1,4-butanediol through a process of transesterification/polycondensation in the presence of a high effective catalyst and characterized by means of GPC and DSC. The investigation was mainly focused on the influence of content of terephthalate units on the molecular weight and thermal properties of resulting polymers. It is revealed that the melting temperature and crystallinity of synthesized polymers decrease first with the increase of terephthalate units, then shift to rise gradually by DSC measurements. The results of Flory equation suggest sequence structure of PBSTs is random.

THERMALLY STIMULATED SHAPE MEMORY BEHAVIOR OF(ETHYLENE OXIDE-BUTYLENE TEREPHTHALATE)SEGMENTED COPOLYMER

The thermally stimulated shape memory behavior of ethylene oxide-butylene terephthalate (EOBT) segmented copolymers with different soft segment molecular weight and hard segment content was investigated. The deformation recovery ratio R-f of the EOBT samples increases with the soft segment molecular weight and the hard segment weight content, while the average overall deformation recovery speed V-r increases with the hard segment content. The temperature of maximum deformation recovery speed (T-M) is determined by the melting temperature of the soft segment crystals and the stability of the crystallized hard segment domains.

TRANSESTERIFICATION OF POLY(BISPHENOL A CARBONATE) WITH AROMATIC AND ALIPHATIC SEGMENTS IN BUTYLENE TEREPHTHALATE-CAPROLACTONE COPOLYESTER

In this article, the transesterification of poly(bisphenol A carbonate) (PC) with butylene terephthalate-caprolactone copolyester at a weight ratio 50/50 (BCL(21)) was thoroughly investigated by proton nuclear magnetic resonance spectroscopy ('H-NMR), in conjunction with a model compound. The 1 H-NMR results of the annealed blend PC/BCL(21) show that the formation of bisphenol A-terephthalate ester units is the same as in the annealed blend of PC with PBT, and the transesterification actually occurs between PC and butylene terephthalate (BT) segments in BCL(21). By comparison with the model compound bisphenol A dibutyrate, the new signal appearing at δ= 2.56 in the 1H-NMR spectrum confirms the existence of bisphenol A caprolactone ester units resulting from the exchange reaction of PC with caprolactone (CL) segments. 1H-NMR analysis of the transesterification rates reveals that the reaction of PC with aromatic and aliphatic segments in BCL(21) proceeds in a random manner. The miscibility of the blend PC/BCL(21) copolyester is favorable for the transesterification of PC with BT segments and CL segments.

COMPOSITIONAL HETEROGENEITY OF ETHYLENE OXIDE-BUTYLENE TEREPHTHALATE SEGMENTED COPOLYMER

A series of ethylene oxide-butylene terephthalate (EOBT) segmented copolymers with different soft segment length and hard segment content were synthesized. The compositional heterogeneity was studied by solvent extraction. The results show that the compositional heterogeneity increases when soft segment length and hard segment content increase. The compositional heterogeneity is also reflected in the crystallization behavior and morphology of soft and hard segment in EOBT segmented copolymer. The more compositional heterogeneous the EOBT segmented copolymer is, the more different the morphology and the crystallization behavior between separated fractions. Compared with ethylene oxide-ethylene terephthalate (EOET) segmented copolymer, compositional heterogeneity in EOBT segmented copolymer is weaker. But the compositional heterogeneity in EOBT segmented copolymer with long soft segment and high hard segment content is still obvious.

Studies on the Simultaneous Synthesis of Dimethyl Carbonate and Poly(ethylene terephthalate): I. Catalytic Activity of Metal Acetate in Transesterification of Ethylene Carbonate with Dimethyl Terephthalate

A novel direct method for preparation of dimethyl carbonate and poly（ethylene terephthalate） from ethylene carbonate and dimethyl terephthalate has been demonstrated in the presence of metal acetate catalysts, lithium acetate dihydrate showed highest catalytic activity with 47.9% yield of dimethyl carbonate. This method was a green chemical process.

Stannous-acetylacetonate:A new catalyst for poly(trimethylene terephthalate) synthesis

Stannous-acetylacetonate was prepared efficiently and characterized by ^1H NMR and FT-IR. Its catalytic activity for poly（trimethylene terephthalate） （PTT） synthesis was investigated. By this catalyst, the degree of esterification of pure terephthalic acid was up to 91.7% after reaction at 260 ℃ for 2 h, while the intrinsic viscosity and content of terminal carboxyl groups of the corresponding PTT polymerized at 260 ℃, 60 Pa for 2 h was 0.8816 dL/g and 17 mol/t,respectively. Stannous-acetylacetonate was more active and promising than tetrabutyl titanate and stannous octoate for PTT synthesis.

Characterization and Properties of Electroless Nickel Plated Poly (ethylene terephthalate) Nonwoven Fabric Enhanced by Dielectric Barrier Discharge Plasma Pretreatment

In order to develop a more economical pretreatment method for electroless nickel plating, a dielectric barrier discharge （DBD） plasma at atmospheric pressure was used to improve the hydrophilicity and adhesion of poly （ethylene terephthalate） （PET） nonwoven fabric. The properties of the PET nonwoven fabric including its liquid absorptive capacity （WA）, aging behavior, surface chemical composition, morphology of the surface, adhesion strength, surface electrical resistivity and electromagnetic interference （EMI）- shielding effectiveness （SE） were studied. The liquid absorptive capacity （WA） increased due to the incorporation of oxygen-containing and nitrogen-containing functional groups on the surface of PET nonwoven fabric after DBD airplasma treatment. The surface morphology of the nonwoven fibers became rougher after plasma treatment. Therefore, the surface was more prone to absorb tin sensitizer and palladium catalyst to form an active layer for the deposition of electroless nickel. SEM and X-ray diffraction （XRD） measurements indicated that a uniform coating of nickel was formed on the PET nonwoven fabric. The average EMI-SE of Ni-plating of PET nonwoven fabric maintained a relatively stable value （38.2 dB to 37.3 dB） in a frequency range of 50 MHz to 1500 MHz. It is concluded that DBD is feasible for pretreatment of nonwoven fabric for electroless nickel plating to prepare functional material with good EMI-SE properties.

CRYSTAL STRUCTURE AND MORPHOLOGY OF NASCENT SAMPLES OF SYMMETRIC AROMATIC POLYESTERS——Ⅰ.POLY(P-PHENYLENE TEREPHTHALATE)

The morphology and crytal structure of poly(p-phenylene terephthalate) (PPT), prepared by confined thin filmmelt (CTFMP) and solution (CTFSP) and bulk solution polymerization, were characterized by transmission electronmicroscopy, electron dimaction and molecular modeling. The unit cell is monoclinic (P2_1/a space group) with parameters a =7.89, b = 5.49, c = 12.65 A, α=γ= 90°, β=100.33°, density = 1.48 g/cm^3, the a, b and β values differing slightly from thosereported previously in the literature. A degree of variation in relative intensities of hk0 reflections in, apparently, untilted[001] ED patterns was observed from a given sample, suggesting some variation in molecular packing. ED evidence wasfound for a second phase, with [001] appearing the same as for phase Ⅱ of the related poly(p-oxybenzoate) (PpOBA)polymer. CTFMP crystals polymerized above 220℃ (up to 370℃) and CTFSP crystals polymerized at 300℃ consisted oflamellae 100-200 A thick.

Thermal degradation and isothermal crystalline behavior of poly(trimethylene terephthalate)

Poly（trimethylene terephthalate） （PTT） is an excellent fiber material. Its thermal degradation and isothermal crystalline behaviors were in this study investigated using thermogravimetric analysis （TGA）, thermogravimetric analysis-Fourier transform infrared spectroscopy （TGA-FTIR） analysis, differential scanning calorimetry （DSC） and X-ray diffraction （XRD）. The thermal degradation mechanism of PTT follows Mclafferty rearrangement principle. The PTTwithintrinsicviscosity（IV） of 0.74 dL/g has a maximum crystallinity of about 55% at 190 ℃, as demonstrated by DSC and XRD measurements consistently.

Flame Retardancy and Thermal Property of Poly (ethylene terephthalate)/Modified Cyclotriphosphazene Composites

In this study,hexachlorocyclotriphosphazene( HCCP)modified by boric acid and 3-aminopropyltriethoxysilane( KH-550)in solvent diglyme( FR-HCCP) was used as the flame retardant for poly( ethylene terephthalate)( PET) composites. The flame retardancy and thermal property of pure PET and flame-retarded PET composites were mainly investigated. The flame retardancy was investigated by limited oxygen index( LOI) and UL-94 vertical burning test. The results showed that the composites could achieved an increased UL-94 V-0 rating and LOI value 30. 2, when the content of FR-HCCP was just 1%. The pyrolysis-gas chromatography-mass spectrometry( Py-GC / MS) study demonstrated that introducing FR-HCCP into PET would prevent the polymer pyrolysis during heating. TGA analysis showed that the addition of FR-HCCP could improve the char formation of the system. Roman spectra showed the order degree of residue was increasing by adding the additive. The morphology and the chemical structure of the charred residue were detected by SEMand FTIR,respectively. Results demonstrated that a good barrier was formed by the char of the composite,which protected the inside of the composite during burning.

Synthesis and characterization of copolymers of poly(m-xylylene adipamide) and poly(ethylene terephthalate) oligomers by melt copolycondensation

Poly(m-xylylene adipamide)/poly(ethylene terephthalate)(MXD6/PET) copolymers are synthesized by melt copolycondensation with 1–5 wt% low molecular weight PET oligomers into the MXD6 oligomers at 260 °C.FR-IR and1 H NMR analysis results indicate that the interchange reaction has occurred between MXD6 oligomers and PET oligomers. The thermal behavior of copolymers shows that the melting temperature of MXD6/PET copolymers decreases with the increasing of amount of PET oligomers, while the crystallization temperature accordingly increases. And the equilibrium temperature Tm0 is evaluated to be 251.8 °C for the copolymers with5 wt% PET oligomer adding, which is very close to that of neat MXD6. The tensile and impact strength of MXD6/PET copolymers are significantly improved than that of pure MXD6 by mechanical properties test, and the microfibril structure in the impact fracture sample's surface reveals the feature of ductile fracture.

FOURIER TRANSFORM INFRARED STUDIES OF POLY (ETHYLENE TEREPHTHALATE) FILM IN THE GLASS TRANSITION REGION

Three specimens from a solution-cast poly (ethylene terephthalate) (PET) film, one being liquid-N_2 quenched from 92℃(Q), one being slowly cooled from 92℃(SC) and one being quenched and sub-T_g annealed at 67℃(AN), have been studied by specimen difference spectra Q-SC and AN-Q and temperature difference spectra T-70 and T_2-T_1 for every 2℃ steps on heating to 90℃ at 2℃ /min. SC and AN showed more gauche conformers than Q. That means that the PET chain has more trans conformers at higher temperatures and some of these are frozen during quenching through T_g. A band at 1340 cm^(-1) has been found to be complex containing overlapping bands reflecting trans in crystalline regions and trans in amorphous regions. The temperature difference spectra on heating through T_g showed that the spectral changes in Q are gradual while a rather abrupt change occurs in AN at 80—82℃ for the bands at 1340, 1042 and 1020 cm^(-1). No new conformational structure or new vibrational mode is involved. A kind of locking mechanism is suggested which hinders the molecular vibrational changes in AN below T_g until a sudden release occurs at T_g. These locking sites can be nothing else than sites of tighter local packing of chain segments. Consequently it is believed that inter-chain van der Waals attraction energy plays a dominating role in the volume relaxation and sub-T_g annealing of quenched amorphous polymers.

Enzymatic Degradation of Poly(butylenesuccinate)/Thermoplastic Starch Blend

The degradation of thermoplastic starch blend in the presence of commerciala-amylase and unpurified amylase of microbial origin was investigated.The blends consisting of thermoplastic starch and poly(butylene succinate)have potential use in packaging applications thus,it is essential to establish susceptibility to degradation.Molar mass loss,gravimetric weight loss,and molecular structure were evaluated.The changes in the surface were observed with scanning electron microscopy.It was confirmed that there was a significant difference in gravimetric weight loss between the blends degraded in two different solutions.Unpurified enzymes of microbial origin,produced by Rhizopus oryzae cultures decomposed analyzed materials more efficiently than purified commercial ones.Moreover,it was proved that in applied conditions,the molar mass of PBS fraction did not change significantly.

Isothermal Crystallization Behavior of Poly (ethylene terephthalate)/Carbon Black Masterbatch

Poly(ethylene terephthalate) (PET)/carbon black (CB) masterbatch was prepared by melt blending using a separate feeding technique and its homogeneous dispersion morphology was confirmed by transmission electron microscope (TEM). The Avrami and Hoffman-Lauritzen secondary nucleation theories were employed to analyze the effect of high CB content on crystallization kinetics of PET, providing theoretical support for the development of masterbatch with high content of functional components. The Avrami exponents,average values of n,for PET and PET/CB masterbatch are both greater than 3, which indicates three-dimensional growth of crystals. In addition,no significant evidence for regime transition of PET is found applying Hoffman-Lauritzen secondary nucleation theory,though such observations have been reported previously in the literature. Furthermore,appropriate U* value for PET is determined to be 12 800 J/mol. For PET/CB masterbatch,a transition from regime I to regime II around 225℃ is observed with appropriate U* value (12 800 J/mol) . This phenomenon is consistent with a transition point in plot of G versus Tc . The fold surface free energy σe (100. 3 mJ/m 2) of PET is much greater than that of PET/CB masterbatch (48. 3 mJ/m 2) ,which indicates heterogeneous nucleation effect of CB particles.

Simultaneous Synthesis of Dimethyl Carbonate and Poly（ethylene terephthalate） Using Alkali Metals as Catalysts

Dimethyl 碳酸盐(直接数字控制) 并且(乙烯 terephthalate ) 被乙烯碳酸盐(EC ) 的 transesterification 同时 poly 在这篇论文与暗淡乙醇 terephthalate (DMT ) 综合。没有有毒的物质，这反应是一个优秀绿化学过程。各种各样的碱金属被用作催化剂。结果证明碱金属在某个程度举办了催化活动。反应状况的效果也被学习。当反应在下列条件下面被执行时：反应温度 250 ° C，到 DMT 3:1 的 EC 的臼齿的比率，反应时间 3h，和催化剂总计 0.004 (到 DMT 的臼齿的比率) ，直接数字控制的收益是 68.9% 。

In-situ Polymerization-modification Process and Foaming of Poly（ethylene terephthalate）

Most of traditional linear poly(ethylene terephthalate)(PET)resins of relatively low molecular mass and narrow molecular mass distribution have low melt strength at foaming temperatures,which are not enough to support and keep cells.An in-situ polymerization-modification process with esterification and polycondensation stages was performed in a 2 L batch stirred reactor using pyromellitic dianhydride(PMDA)or pentaerythritol(PENTA)as modifying monomers to obtain PETs with high melt strength.The influence of amounts of modifying monomers on the properties of modified PET was investigated.It was found that the selected modifying monomers could effectively introduce branched structures into the modified PETs and improve their melt strength.With increasing the amount of the modifying monomer,the melt strength of the modified PET increased.But when the amount of PENTA reached 0.35%or PMDA reached 0.9%,crosslinking phenomenon was observed in the modified PET.Supercritical carbon dioxide(ScCO2)was employed as physical foaming agent to evaluate the foaming ability of modified PETs.The modified PETs had good foaming properties at 14 MPa of CO2pressure with foaming temperature ranging from 265°C to 280°C.SEM micrographs demonstrated that both modified PET foams had homogeneous cellular structures,with cell diameter ranging from 35μm to 49μm for PENTA modified PETs and38μm to 57μm for PMDA modified ones.Correspondingly,the cell density had a range of 3.5×107cells·cm 3to 7×106cells·cm 3for the former and 2.8×107cells·cm 3to 5.8×106cells·cm 3for the latter.

High-efficiency acetaldehyde removal during solid-state polycondensation of poly(ethylene terephthalate) assisted by supercritical carbon dioxide

The concentration of acetaldehyde(AA) is the main quality index of poly(ethylene terephthalate)(PET) used in food and drink packaging.A new method for AA removal has been developed by using supercritical carbon dioxide(sc CO2) during the solid-state polycondensation of PET.The influence factors of AA removal including the temperature,pressure,reaction time and the size of pre-polymer particles are systematically studied in this work.The results indicate that it is a highly efficient way to obtain high molecular weight PET with relative low concentration of AA.Correspondingly,the polymerization degree of PET could increase from 27.9 to 85.6 while the concentration of AA reduces from 0.229 × 10^(-6) to 0.055 × 10^(-6) under the optimal operation conditions of 230 °C,8 MPa and size of 0.30–0.45 mm.Thermodynamic performance tests show the increasing extent of PET crystallinity due to the fact that the plasticization of sc CO_2 is not obvious with extended reaction time,therefore the increasing crystallinity has no significant influence on AA removal.SEM observations reveal that the effects of sc CO_(2-) induced plasticization and swelling on PET increase significantly with the decrease of prepolymer size,and the surface of PET becomes more loose and porous in favor of the AA removal.