Thermorheology as a method to analyze long-chain branched polyethylenes

This paper presents correlations between polyethylenes of different compositions and branching architectures and their viscoelastic behavior in dependence on the temperature and demonstrates how effectively rheological experiments can be used for analytical purposes. Long-chain branched polyethylenes are known to be thermorheologically complex. But the thermorheological complexity of long-chain branched linear low-density metallocene polyethylenes (LCB-mLLDPE) differs from that of low-density polyethylenes (LDPE) in the way that the activation energy of LDPE becomes constant by a temperature-dependent modification of the moduli whereas a constant activation energy cannot be obtained for LCB-mLLDPE. These findings are explained by the assumption that the LCB-mLLDPE investigated consist of at least two species with distinctly different activation energies. This interpretation is supported by the thermorheological analysis of a blend of known parts of an LDPE and a linear low-density polyethylene (LLDPE). A thermorheological complexity was found similar to that of the LCB-mLLDPE which reflects the different activation energies of the two components. Results of that kind make it possible to get information on the composition of LCB-mLLDPE not available from common analytical methods.     

氮杂冠醚中间体二氨基芳醚制备的新方法

用５０％水合肼，在ＦｅＣｌ２．６Ｈ２Ｏ及活性炭的催化作用下，还原制得了８个开链冠醚桥连的二氨基芳醚。还原产率７７％～９２％之间。     

Evaluation of the mechanical properties of sisal–polyester composites as a function of the polyester matrix formulation

In this work a comparative study on the impact and tensile properties of polyester/sisal fiber reinforced composites was undertaken. The polyester matrix was used bare and modified with: (1) a silane coupling agent; (2) a flame retardant system; and (3) a blend of the silane agent and the flame retardant system. The experimental results show that the flame retardant acts as a particulate reinforcement to the polyester matrix and the silane coupling agent acts as a plasticizer. The simultaneous addition of these two compounds to the polyester resin tended to decrease the performance of the composites. The results obtained show that strength or toughness could be tailored, and although none of the composites manufactured with the modified polyester matrices showed a significant improvement on the fiber–matrix interface strength, a better compromise between impact and tensile properties was obtained with the silane modified matrix. The critical fiber volume fraction was also evaluated and shown to be less than 10% for the sisal–polyester composite investigated here. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1209–1217, 2004     

端-NCO支化聚酯/聚醚改性EP底涂剂制备及性能研究

以甲苯二异氰酸酯(TDI)、支化聚酯/聚醚多元醇等为主要原料,制备了端-NCO支化聚酯/聚醚;然后以此为环氧树脂(EP)的增韧改性剂,制备端-NCO支化聚酯/聚醚改性EP底涂剂。研究了R值[即R=n(-NCO)/n(-OH)]、硅烷偶联剂用量等对该底涂剂的粘接性能、表干时间、耐水性能和冲击性能等影响。结果表明:当R值为2.0、w(硅烷偶联剂)=2%时,该底涂剂的综合性能相对最好;此时底涂剂的表干时间(3.0 min)相对最短、底涂剂与基材之间的粘接强度(>3 MPa)相对最高且耐水性能(浸水后粘接强度降幅仅为4.68%)相对最好。     

Vegetable oil based highly branched polyester/clay silver nanocomposites as antimicrobial surface coating materials

The unison of nanotechnology and polymer science enables the development of novel silver-based polyester nanocomposite as an antimicrobial coating material. Highly branched polyester/clay silver nanocomposites based on vegetable oil with different loadings of silver were prepared via reduction of silver salt by employing dimethylformamide as solvent as well as reducing agent at room temperature. Organically modified montmorillonite clay of 2.5 wt% was used as the nanofiller for the property improvement of the pristine polymer. The highly branched polyester resin was synthesized by condensation of 2,2-bis(hydroxymethyl) propionic acid with Mesua ferrea L. seed oil based carboxyl terminated pre-polymer, as reported earlier. FTIR, UV–vis, XRD, SEM and TEM studies substantiate the formation of well-dispersed silver nanoparticles within the clay gallery with an average size of 15 nm. The thermostability of the silver nanocomposites obtained by thermogravimetric analysis was enhanced by 20 °C. The mechanical properties such as tensile strength and scratch hardness were improved 4.5 and 2.6 units respectively and impact resistance improved a little by nanocomposites formation. The antimicrobial efficacy of the as-prepared silver nanocomposites was also premeditated and highly antibacterial activity against Gram negative bacteria (Escherichia coli and Psuedomonas aeruginosa) was observed. Excellent chemical resistance in various chemical media except in alkali has also been noticed. The study reveals that the polyester/clay silver nanocomposites based on vegetable oil show the potential to be applicable as antibacterial surface coating materials.     

涂料用支化型饱和聚酯树脂的合成及表征

采用溶液缩聚的方法,以对苯二甲酸、间苯二甲酸、己二酸、新戊二醇、一缩二乙二醇和1,1,1-三羟甲基丙烷(TMP)为原料,合成了一类新型的涂料用支化型饱和聚酯树脂。介绍了合成工艺及原材料的选择。通过红外光谱分析、X-射线衍射、热重分析和差热分析等测试其结构、形态和热性能。结果表明,合成的涂料用支化型饱和聚酯树脂的热稳定性较高。     

Application of a thermostable Baeyer–Villiger monooxygenase for the synthesis of branched polyester precursors

BACKGROUND

It is widely accepted that the poor thermostability of Baeyer–Villiger monooxygenases limits their use as biocatalysts for applied biocatalysis in industrial applications. The goal of this study was to investigate the biocatalytic oxidation of 3,3,5‐trimethylcyclohexanone using a thermostable cyclohexanone monooxygenase from Thermocrispum municipale (TmCHMO) for the synthesis of branched ?‐caprolactone derivatives as building blocks for tuned polymeric backbones. In this multi‐enzymatic reaction, the thermostable cyclohexanone monooxygenase was fused to a phosphite dehydrogenase (PTDH) in order to ensure co‐factor regeneration.

RESULTS

Using reaction engineering, the reaction rate and product formation of the regio‐isomeric branched lactones were improved and the use of co‐solvents and the initial substrate load were investigated. Substrate inhibition and poor product solubility were overcome using continuous substrate feeding regimes, as well as a biphasic reaction system with toluene as water‐immiscible organic solvent. A maximum volumetric productivity, or space–time‐yield, of 1.20 g L^‐1 h^‐1 was achieved with continuous feeding of substrate using methanol as co‐solvent, while a maximum product concentration of 11.6 g L^‐1 was achieved with toluene acting as a second phase and substrate reservoir.

CONCLUSION

These improvements in key process metrics therefore demonstrate progress towards the up‐scaled Baeyer–Villiger monooxygenase‐biocatalyzed synthesis of the target building blocks for polymer application. © 2018 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

     

利用废聚酯薄膜制备不饱和聚酯树脂工艺研究

以废聚酯薄膜(PET)为原料制得了不饱和聚酯树脂(UPR),通过产物酸值测定研究了反应温度、催化剂种类对聚酯薄膜降解反应的影响,通过固化性能测试及其浇注体和玻璃钢制品的力学和热性能测试确定了废聚酯薄膜的用量,并将制品的性能与邻苯型196#不饱和聚酯树脂作了比较。结果表明:采用有机锡类和醋酸锌的复合催化剂,反应温度210～225℃,废聚酯薄膜与顺丁烯二酸酐物质的量比1:2.7时UPR产品性能最优,其力学性能、耐热性和耐腐蚀性均优于196#UPR。     

可吸湿排汗的新型聚酯纤维的研制

介绍了具有吸湿排汗性能的新型聚酯纤维的研制。探讨了共混原料的均匀性及配比,异形喷丝板的选择,后加工工艺,及其对纤维相关性能指标的影响。简述了吸湿排汗织物的评价方法。     

Modification of hyperbranched epoxy by vegetable oil-based highly branched polyester resin

Modification of existing polymers by physico-chemical technique is not only interesting and useful to the academic community but the resulted product is attractive to industrial application too. In this investigation, hyperbranched epoxy was modified by vegetable oil-based highly branched polyester resin at different weight percentages and properties of the cured systems were evaluated in order to justify them as advanced thin film materials with high adhesive strength. Modified systems were studied using FTIR, XRD, TGA and SEM analyses. Curing reaction was confirmed by FTIR study and swelling test. Performance characteristics like tensile strength, impact strength, adhesive strength, flexibility, scratch hardness, gloss and chemical resistance of cured films have also been studied. Modified systems showed improved properties over pristine epoxy. Comparison study of modified systems showed that hyperbranched epoxy with 30 wt% polyester content is the best composition w.r.t performance and might be utilized in advanced thin film application.     

以聚酯薄膜为载体制备超薄镍箔的工艺

以厚度为0.05 ～ 0.20 mm的耐高温、平整度好的PET薄膜作为载体,利用高真空磁控溅射技术使薄膜单面金属化,然后预镀光亮铜,接着浸涂羧基苯并三唑溶液形成一薄层有机物离析层,继而采用氨基磺酸盐镀镍工艺在其表面沉积规定厚度的镍层,最后将镍层从基材上剥离,即获得超薄镍箔材料.给出了各工序的操作条件,指出了预镀光亮铜、...     

Melt-spinning of in-situ composites of a thermotropic liquid crystalline polyester in a miscible matrix of poly(ether ether ketone) and poly(ether imide)

Blends of a thermotropic liquid crystalline polyester (TLCP) and a thermoplastic matrix of 75 wt% poly(ether ether ketone) and 25 wt% poly(ether imide) were melt-spun into fibers. The fibers were evaluated in terms of morphology and mechanical properties. Composite fibers containing more than 25 wt% TLCP exhibited a morphology in which the TLCP was dispersed as very long fibrils with good alignment of the molecules in the spinning direction; correspondingly the fibers followed the rule of mixtures behavior for stiffness versus composition. For fibers containing 5 and 10 wt% TLCP, both fibril aspect ratio and molecular orientation were lower, and the stiffness was below the rule of mixtures. This difference can be explained by interfacial tension effects, which are of paramount importance in the deformation of TLCP particles into fibrils.     

Properties of branched polymer chains adsorbed on a patterned surface

The aim of this study was to investigate the properties of polymer chains strongly adsorbed on a planar surface. Model macromolecules were constructed of identical segments, the positions of which were restricted to nodes of a simple cubic lattice. The chains were in good solvent conditions, thus, the excluded volume was the only interaction between the polymer segments. The polymer model chain interacted via a simple contact potential with an impenetrable flat surface with two kinds of points: attractive and repulsive (the latter being arranged into narrow strips). The properties of the macromolecular system were determined by means of Monte Carlo simulations with a sampling algorithm based on the local conformational changes of the chain. The structure of adsorbed chains was found to be strongly dependent on the distance between the repulsive strips, whenever this distance was very short. The mobility of the chains was also studied and it was found that diffusion across repulsive strips was suppressed for large distances between the strips.     

Effect of the hybrid catalysts preparation method upon direct synthesis of dimethyl ether from synthesis gas

Direct synthesis of DME from synthesis gas attains more attention recently due to higher conversion and lower cost in comparison to dehydration of the methanol. In this work Synthesis gas To Dimethylether (STD) conversion was examined on various hybrid catalysts prepared by seven different methods. These catalysts had the same general form as CuO/ZnO/Al₂O₃ with theoretical weight ratio 31/16/53, respectively. A novel preparation method for hybrid catalyst namely sol–gel impregnation has also been developed which showed better performance in comparison with the other methods. Also, in order to find out the effect of various alumina contents at a fixed CuO/ZnO ratio on the performance of the hybrid catalyst, a series of catalysts with different contents of alumina have been prepared by sol–gel impregnation method. The optimum weight ratio for CuO/ZnO/Al₂O₃ catalyst has been found to be about 2:1:5, respectively. These catalysts characterized by TPR, XRD, XRF, BET, TGA, N₂O absorption. The catalysts performance were tested at 240 °C, 40 bar and space velocity 1000 ml/g_cat.h, with the inlet gas composition H₂/CO/N₂ = 64/32/4 in a micro slurry reactor.     

Segmented copolymers of poly(phenylene ether) and polyester

Copolymers of telechelic poly(2,6-dimethyl-1,4-phenylene ether) (PPE) segments with terephthalic methyl ester end groups (PPE-2T, 3500 g/mol) and poly(dodecane terephthalate) (PDDT) were made via a polycondensation reaction in the melt. The inherent viscosities of the segmented copolymers were high. The thermal properties of the copolymers were studied by DMA. The segmented block copolymers had a transparent melt at low (12 wt%) PDDT contents. The segmented block copolymers had at higher PDDT contents a non-transparent melt and two glass transition temperatures. The glass transition temperature of the PPE phase decreased strongly with PDDT content in the copolymer. The glass transition temperature of the PDDT phase increased moderately with PPE content. At low PPE contents the modulus of the PDDT increased strongly with increasing PPE content.     

Studies on the preparation of branched polymers from styrene and divinylbenzene

The self‐condensing vinyl polymerization of styrene and an inimer formed in situ by atom transfer radical addition from divinylbenzene and 2‐bromoisobutyl‐tert‐butyrate using atom transfer radical polymerization technique was studied. To study the polymerization mechanism and achieve high molecular weight polymer in a high polymer yield, the polymerization was carried out in bulk at 80°C. Proton nuclear magnetic resonance (¹H‐NMR) spectroscopy and gel permeation chromatography (GPC) coupled with multiangle laser light scattering (MALLS) were used to monitor the polymerization process and characterize the solid polymers. It is proved that the polymerization shows a “living” polymerization behavior and the crosslinking reaction has been restrained effectively due to the introduction of styrene. Polymers with high molecular weight (M_w.MALLS > 10⁵) can be prepared in high yield (near 80%). Comparison of the apparent molecular weights measured by GPC with the absolute values measured by MALLS indicates the existence of branched structures in the prepared polymers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

高吸湿聚酯母粒的制备及性能研究

研究了PET、CDP与无机超细微粒在不同的共混比例下的共混条件以及共混后母粒的流变性能。结果表明:在母粒制备中,共混体系均为切力变稀非牛顿流体,随着成孔剂含量的增加,共混体系表观粘度ηa随的 γw增大而下降,并趋于缓慢;在相同的条件下,用CDPET制成的母粒流动性好于PET。     

可生物降解聚酯的制备及性能研究进展

相对于传统高分子材料,生物降解高分子材料由于其能够在自然环境下降解为环境无害的物质,作为解决塑料白色污染的重要手段之一,近年来获得快速发展。对本课题组生物降解聚酯结构设计、改性及产业化等方面的研究进展进行了总结。通过无规/嵌段共聚的方式在聚二元酸二元醇酯中引入共聚单体单元、长/短支化结构可有效对材料的结晶性能、熔体强度等性能进行调控,进而实现对材料加工性能、力学性能以及生物降解速率的调控。通过对聚合工艺的创新优化,实现高分子量不饱和聚酯的合成,并阐明了其聚合机理;进一步,通过在不饱和聚酯中引入Diels-Alder反应/金属配位活性位点实现可逆交联弹性体的制备。对聚二元酸二元醇酯的结晶结构调控与结晶机理进行了深入的研究,提出了一种基于结晶成核动力学测定高分子结晶次级临界核尺寸的方法;基于类质同晶构型构象匹配设计了新型高效大分子型成核剂。在实验室研究的基础上,与企业合作建成了年产万吨生物降解聚酯及其共聚酯的生产线,生产的产品已应用于一次性餐具、超市购物袋和地膜的制备,并在新疆进行了农田可降解地膜的应用示范。