US registration brings global status for Avecia's new plastic antimicrobial

Avecia Biocides has obtained US EPA registration for its new Vanquish◐ 100 plastics antimicrobial. The company says that it is the first new biocidal active ingredient to be registered as a preservative for plastics in the US in the past five years. Already a successful product in Europe, Asia, and Latin America, the company says that US registration for this member of the Vanquish^™ product range means that it now has global regulatory status.This is a short news story only. Visit www.addcomp.com for the latest additives and compounding industry news     

Preparation of controlled molecular weight and narrow distribution HALS and its application

A polymerizable hindered amine light stabilizer (HALS) 1,2,2,6,6-pentamethyl-piperidin-4-yl acrylate (PMPA) was synthesized, and it was copolymerized with styrene to prepare poly(St-co-PMPA) by reversible addition fragmentation chain transfer (RAFT) polymerization. The reaction conditions, such as chain transfer agent (CTA)/initiator ratio, monomer/CTA ratio, and St/PMPA ratio, were found to affect the polymerization reaction. Poly(St-co-PMPA) with high molecular weight and narrow distribution could be obtained under suitable conditions. The molecular weight is about 3.0 × 10³ to 5.0 × 10³ and the molecular weight distribution is about 1.07 to 1.25. The result showed that PMPA was effectively added to the polymer chain and the polymerizations were found to proceed in controlled fashions under a lower conversion. Moreover, the tensile strength and notched impact strength of ABS/poly(St-co-PMPA) are significantly improved, respectively, after 800-h UV irradiation, which was both higher than that of pure ABS. The results showed that poly(St-co-PMPA) was an effective high molecular weight HALS.     

Molecular weight characterization of polybutadiene rubber with high molecular weight and broad molecular weight distribution

Following the molecular weight characterization of two polybutadiene samples, it was found that M _w from gel permeation chromatography with universal calibration and light scattering were in agreement, but M _n by gel permeation chromatography was less than M _n from membrane osmometry. A more detailed analysis revealed that the high molecular weight and broad molecular weight distribution of the two samples forced two corrections to the membrane osmometry results for (a) diffusional layer effects caused by high solution viscosities, and (b) solute permeability of the membrane. In the latter effect, the high viscosities of the solutions prevented actual diffusion through the membrane, but “reflection” of these species as defined by the Staverman coefficient prevented an accurate M _n determination. After making these corrections, it was found that M _n from membrane osmometry using a very tight membrane was in very good agreement with M _n from gel permeation chromatography. A method is demonstrated for obtaining M _n from a combination of membrane osmometry and gel permeation chromatography, where membrane osmometry data from membranes of different porosities (after corrections for diffusional layers and membrane reflection) are used to verify the accuracy of the gel permeation chromatography data as representing the true molecular weight distribution, allowing the gel permeation chromatography data to be used to calculate M _n.     

高分子质量阳离子聚丙烯酰胺的合成

将过硫酸铵-亚硫酸氢钠与2,2'-偶氮(2-脒基丙烷)二氢氯化物(V-50)组成的复合引发体系用于丙烯酰胺(AM)与丙烯酰氧乙基三甲基氯化铵(DAC)聚合,制备了高分子质量的阳离子聚丙烯酰胺P(DAC-AM).探讨了单体质量分数、引发剂用量、阳离子单体含量、pH、反应时间等因素对聚合物特性黏数的影响.得到的最佳反应条件为:单体最佳质量分数为35%,引发剂用量为整个体系质量的0.02%,V-50为单体质量的0.005%,最佳pH为5.5～6.5,尿素为单体质量的0.1%,EDTA为单体质量的0.02%,β-二甲胺基丙腈为单体质量的0.03%,反应时间为5～6h.特性黏数η达到13.95 dL/g.     

Flocculating properties of high molecular weight lignosulphonates

The flocculating properties of various molecular weight lignosulphonates have been examined. The low molecular weight polymers were found to act as dispersants at all concentrations even in the presence of alum. In contrast, lignosulphonates having an intrinsic viscosity greater than 0.11 dl/g acted as flocculants at low concentration and dispersants at high concentration. The flocculation rate increased with the molecular weight of the polymer, and was greatly enhanced by the presence of alum. Reducing the pH enhanced the dispersing properties of the low molecular weight lignosulphonates and the flocculating properties of the high molecular weight material.     

Catalysts for the selective dehydrogenation of high molecular weight paraffins

Selective dehydrogenation of high molecular weight linear paraffins is an important process step for the production of biodegradable detergents. Pt, PtSn, PtGe and PtPb supported on -A1₂O₃ doped with alkaline metals were characterized and tested in then-decane dehydrogenation reaction. When alkaline metals are added to Pt/Al₂O₃ a promoting effect on the selectivity to olefins in then-decane dehydrogenation is observed. Regarding PtSn/Al₂O₃ -doped catalysts their performance depends on the alkaline metal used as dopant, the Sn content and the preparation method. Moreover these bimetallic catalysts show a better olefin yield and a lower selectivity to gases and aromatics than the monometallic platinum catalysts. PtGe and PtPb based catalysts have an analogous behavior to the PtSn one but its selectivity to olefins is lower.     

On the real molecular weight of polyethylene oxide of high molecular weight in water

It is shown that water is close to being a theta solvent for polyethylene oxide which is highly aggregated in this solvent. This result is in agreement with the behaviour observed by hydrodynamic measurements (turbulent drag reduction and concentration and shear dependence of the viscosity). With the molecular weight correction proposed in this work, the onset drag reduction data obtained with Polyox agree well with Virk's theory.     

A new method for determining molecular weight distributions of copolymers

Measurement of the molecular weight distributions of copolymers by size exclusion chromatography (SEC) presents problems because the elution volume of any species may depend on its composition as well as its molecular weight. Also, the response of the usual concentration detectors may also be influenced by the copolymer composition as well as its concentration. These problems arise when the copolymer composition may vary with molecular size. Conventional SEC techniques are suitable for copolymers with invariant compositions. This article describes and illustrates a method for measuring molecular weight distributions of copolymers. In many cases, the variation of copolymer composition with molecular weight can also be determined. The technique uses three detectors: (a) an evaporative detector (ED) to measure the concentration, Δc, of the eluting species; (b) a differential refractive index detector (DRI) to measure the refractive index difference, Δn, between the solution and solvent at any given elution volume; and (c) a low-angle laser light scattering (LALLS) detector that measures the corresponding molecular weight of the eluting solutes. This latter measurement is possible because the appropriate values of Δn/Δc are available from the outputs of the other two detectors. For LALLS measurements of molecular weight all the species in the detector cell at any instant must have the same composition or, at least not have Δn/Δc that varies with composition. The method is illustrated with data from ethylene-propylene and ethylene-propylene-diene copolymers.     

超高分子量聚烯烃聚合催化剂及聚合工艺

讨论了在超高分子量聚烯烃生产中 ,新催化剂系统、新聚合工艺方法的使用 ,提供了人们在催化剂中选择的改性组分。叙述了在预聚条件下和无预聚条件下 ,得到的超高分子量聚烯烃的物理性能 ,特别是高碳烯烃参与预聚 ,得到了含微量共聚单体的超高分子量聚烯烃。     

The forming properties of high molecular weight polyethylene

The formabilities of cold-rolled high molecular weight polyethylene (HMWPE) sheets have been studied by measuring their plastic anisotropy ratio (R value), strain-hardening exponent (n value), strain distribution, and the forming limit diagram (FLD). The deep drawability of the polymer is improved by rolling. After 40% or more reduction in thickness by cold rolling, the HMWPE sheet could be deep-drawn into a cylindrical cup. The results of R value measurement indicate that the R value is responsible for improved drawability. Cold rolling also increases the n value but decreases the strain gradient. Stretch forming tests have also been carried out, and the results show that cold working could also improve the stretchability of this polymer. The results of the FLD are in agreement with the other properties studied. The mechanical properties, environmental stress cracking resistance, and shape, size, and property stability of the deep-drawn HMWPE cups have also been investigated.     

超高分子量聚乙烯溶解均匀性研究

超高分子量聚乙烯纤维生产工艺中,超高分子量聚乙烯溶解设备普遍使用双螺杆挤出机。文章研究了如何使用双螺杆挤出机,具体涉及到螺纹元件的组合、双螺杆挤出机的转速以及各区温度控制等关键技术,制备溶解均匀的超高分子量聚乙烯溶液,以达到纺丝要求。     

高分子量聚丙烯酸钠聚合动力学的研究

采用水溶液法合成了高分子量聚丙烯酸钠(PNaAA),研究了聚合温度、引发体系及无机盐类等对PNaAA聚合动力学的影响。实验结果表明：在50℃下,选择高活性的过硫酸铵,三乙醇胺(其表观活化能为40．18kJ／mol)作为引发体系,可同时保证高聚合反应速率及高分子量。另外,在体系中加入适量的盐类(如NaCl、乙酸钠),可影响水相单体溶液的离子强度和自由基周围的电势,从而使聚合反应速率增加。     

Extrusion processing of ultra-high molecular weight polyethylene; a new method for the production of high performance structures

We report preliminary findings relating to a method of processing ultra-high molecular weight polyethylene (UHMWPE) in order to obtain extrusions that possess significant molecular orientation and improved mechanical properties. We also show that the method can be used to produce oriented extrusions of composite materials consisting of glass or carbon fibres in a matrix of UHMWPE.     

Size-exclusion chromatography of high molecular weight water-soluble polymers

A preparative-scale, aqueous size-exclusion chromatography system was constructed for fractionation of large molecular weight polymers. Calibration of molecular weight to elution volume was accomplished without polymer standards by using an eluent viscosity detector in series with a refractometer. The system was found to have a hydrodynamic size-separation resolution that ranged from 500 to 3500 Å.     

Die drawing technology of high molecular weight polyethylene

A comprehensive investigation of the die drawing technology of a high molecular weight polythylene (HMWPE) rod has been carried out. The effect of draw temperature, draw speed, nominal draw ratio, and exit diameter of the dies has been studied. The oriented HMWPE products were characterized mainly by the determination of the three-point bend modulus and the tensile strength. The tensile strength and the modulus of the drawn HMWPE rod could reach 700 MPa and 18 GPa, respectively. In addition, it was found that forced cooling at the die exit was essential when drawing billets with large section areas. © 1993 John Wiley & Sons, Inc.     

超高分子量聚乙烯材料的研究进展

超高分子量聚乙烯(UHMWPE)是高性能聚烯烃材料的典型代表,稳定的线性长链结构使其具有高强度、耐冲击、耐磨损、自润滑、耐化学腐蚀、耐低温等诸多优异性能。近年,UHMWPE加工、改性技术日益扩展、优化,形成了多种多样的UHMWPE制品,广泛应用于军民各项领域。本文综述了UHMWPE在催化聚合、纤维、膜、管材、板材及型材等方面的最新进展,重点介绍在各领域应用、加工、改性等方面的研究成果和发展趋势。