高锰酸钾引发淀粉—丙烯腈研制高吸水性聚合物

本文研究了玉米淀粉经糊化后,以高锰酸钾为引发剂,在酸性介质中与丙烯腈的接枝共聚及接枝共聚物在碱性介质中的水解。详细考察了引发剂用量、介质酸度、聚合温度以及碱用量对聚合物吸水性能的影响,并与铈盐等不同引发体系进行了比较。     

纤维素接枝化制备高吸水性树脂

本文研究了纤维素经碱糊化后以铈盐为引发剂与丙烯腈接枝共聚及接枝共聚物在碱性介质中水解。详细考察了引发剂用量、原料配比及皂化碱用量对共聚物吸水性能的影响,并与淀粉—丙烯腈接枝共聚皂化物进行了性能比较。     

橡胶接枝苯乙烯-马来酸酐本体共聚--橡胶粒径及抗冲性能的研究

采用半连续的本体聚合工艺,考察了转相用搅拌转速、反应温度、引发剂用量等聚合工艺条件对橡胶接枝苯乙烯-马来酸酐共聚产物(SMA)中橡胶粒径和性能的影响。实验结果表明,搅拌转速对橡胶粒径的影响比较单一,转速越大,粒径越小;而后两者的影响因素则比较复杂,同时影响两相粘度、剪切强度、基体分子量和接枝效果等,彼此之间相互牵制。通过调整以上工艺参数,可形成2~5 mm大小合适的橡胶粒径,得到抗冲性能较好的SMA。     

高分子多孔膜的表面改性与抗污染研究

采用羟基化预处理、铈盐引发和碱化预处理、Fe2 /H2O2引发两种引发体系,对聚砜(PS)膜和聚丙烯腈(PAN)膜进行表面接枝丙烯酰胺的改性,研究预处理和表面接枝改性对膜污染的影响。采用红外光谱和X光电子能谱对羟基化和接枝改性的膜表面进行表征。研究表明,表面预处理和接枝后,PS膜和PAN膜的水通量均有所下降,但提高了抗牛血清蛋白膜污染能力。     

CAN - KPS体系引发淀粉接枝共聚为絮凝剂的工艺研究

为克服引发剂铈盐较昂贵,工业应用难的缺点,实验采用CAN-KPS复合引发体系引发丙烯腈接枝改性淀粉,采用接枝率和接枝效率作为评价接枝效果的指标,详细研究了接枝工艺及其引发剂浓度、丙烯腈单体的用量和接枝温度对接枝率和接枝效率的影响,结果表明:接枝率达130%以上,接枝效率达90%以上,可较好地代替铈盐引发剂。接枝后对接枝淀粉的结构分析表明:淀粉大分子上已接枝上丙烯腈单体;接枝反应不仅发生在淀粉的无定形区也发生在结晶区,且接枝后接枝淀粉的结晶度有所提高。     

Ce(Ⅳ)盐引发丙烯腈在交联聚乙烯醇微球表面的接枝聚合

以戊二醛为交联剂,在反相悬浮体系中采用直接交联反应成球的方法,制备了聚乙烯醇(PVA)。以硫酸铈铵为引发剂,在酸性溶液聚合体系中实施了丙烯腈(AN)在交联微球CPVA表面的接枝聚合,制备了接枝微粒CPVA-g-PAN,考察了主要因素对交联成球反应与接枝聚合的影响规律。实验结果表明,在一定的搅拌速度下,分散剂用量及油水两相比是影响交联微球CPVA的主要因素。在Ce(Ⅳ)盐的氧化作用下,在含有大量羟基的CPVA微球表面会产生自由基,顺利地实现丙烯腈的自由基接枝聚合反应。反应温度、铈盐浓度和H+离子浓度是影响接枝聚合反应的主要因素。在适宜条件下,可制得PAN接枝度为27 g/100 g的接枝微球CPVA-g-PAN。     

Fe2+-H2O2引发体系对淀粉接枝共聚改性为絮凝剂的影响研究

为克服引发剂铈盐较昂贵,工业应用难的缺点,实验采用Fe2 -H2O2引发体系引发丙烯腈接枝改性淀粉,采用接枝率和接枝效率作为评价接枝效果的指标,详细研究了接枝的工艺及其引发剂浓度、丙烯腈单体的用量和接枝温度对接枝率和接枝效率的影响。接枝后对接枝淀粉的结构分析表明:淀粉大分子上已接枝上丙烯腈单体;接枝反应不仅发生在淀粉的无定形区也发生在结晶区,且接枝后接枝淀粉的结晶度有所提高。     

Ce4+引发体系对淀粉接枝共聚反应的影响研究

研究和介绍了淀粉-丙烯腈接枝共聚反应中引发剂的作用机理及影响因素,通过实验确定了铈盐引发体系的最佳操作条件。     

Ce^4＋引发体系对淀粉接枝共聚反应的影响研究

研究和介绍了淀粉－丙烯腈接枝共聚反应中引发剂的作用机理及影响因素，通过实验确定了铈盐引发体系的最佳操作条件。     

低密度聚乙烯反应挤出接枝衣康酸的研究

以过氧化二异丙苯(DCP)为引发剂,在双螺杆挤出机中制备了衣康酸(IA)熔融接枝低密度聚乙烯(LDPE)。考察了引发剂用量、单体用量、螺杆转速对接枝反应的影响,并探讨了苯乙烯(St)作共聚单体对接枝反应的影响。结果表明:St共聚单体可显著提高接枝率。     

Effect of stirring on cellulose graft copolymerization

Dissolving pulp was grafted with several monomers ranging from hydrophilic (dimethylaminoethyl methacrylate) to hydrophobic (styrene). The conversion of these monomers to polymer and copolymer was investigated in dependence on the number of revolutions of the agitator. The formation of grafted copolymer was found to be strongly influenced by stirring. For all the monomers employed, almost no copolymer was formed above 400 rpm. The formation of homopolymer was also severely reduced at higher stirring speeds. For some monomers, a maximum was obtained at about 200–300 rpm with both copolymer and homopolymer yields dropping off sharply at both lower and higher stirring speeds. The position of this maximum was affected by the size of the reactor. The behavior displayed by the xanthate? Fe²⁺–H₂O₂, Fe²⁺–H₂O₂, and ceric ion initiation systems was very similar. Also, monomer solubility in water seemed to have little importance in determining the general behavior.     

The combined effect of stirring and oxygen on the graft copolymerization of methyl methacrylate onto cellulose

Methyl methacrylate was grafted onto bleached kraft pulp using ceric ammonium nitrate as initiator. The effect of stirring on the conversion to polymer and copolymer was strongly influenced by the presence of oxygen. In an oxygen-free system, the conversion was found to first increase rapidly with rising stirrer speed and then level off. No decrease in conversion was observed even at very high stirrer speeds (up to 1000 rpm). Inclusion of oxygen resulted in the appearance of a maximum on the conversion versus stirring speed curve, followed by a decrease in conversion at more intense agitation. The presence of oxygen also adversely affected the grafting efficiency.     

Effect of stirring on cellulose graft copolymerization. V. Influence of reaction parameters

Styrene was grafted onto dissolving pulp by the cellulose xanthate–Fe²⁺–H₂O₂ system. Reaction parameters were found to have strong influence on conversion to both copolymer and total polymer, as well as on the dependence of polymerization on stirring. The formation of polymer was almost completely inhibited by pure oxygen, while air only slowed down the reaction. Under inert atmosphere, the effect of agitator speed was found to be strongly dependent on monomer and substrate concentration as well as on the concentration of emulsifier. The location of the maximum on the conversion vs. agitator speed curve was strongly affected by the shape of the stirrer. The presence of emulsifier had a relatively small effect on copolymer formation in the case of acrylamide, a water-soluble monomer. Also the effect of stirring was less marked in the case of acrylamide. In all the systems investigated, the conversion to copolymer and total polymer was found to drop rapidly above a certain limiting agitator speed. The latter was different and characteristic for each system. No polymer formation was observed beyond 1000 rpm regardless of all other reaction conditions.     

Glycidyl methacrylate–grafted linear low‐density polyethylene fabrication and application for polyester/polyethylene bonding

The grafting of glycidyl methacrylate (GMA) onto linear low‐density polyethylene (LLDPE) was investigated. The grafting was performed by free‐radical grafting in the melt state in a twin‐screw extruder using an organic peroxide as initiator. The effect of initial GMA and peroxide concentration, styrene comonomer addition, as well as initial resin viscosity, on the final content in grafted moieties, unbound homopolymer, and unreacted monomer was assessed. The effect of process parameters such as flow rate, screw rotation speed, and barrel temperature was also investigated. Chemical composition was shown to be the main parameter for controlling grafting level and grafting efficiency. Grafting levels up to 1.8% and efficiency of 90% were reported even though in most conditions, the graft efficiency was severely decreased by the homopolymerization of GMA into polyGMA chains not bound to LLDPE. Finally, the effect of grafting level and the presence of unbound GMA‐based species on the efficiency GMA‐grafted LLDPE as adhesive between polyethylene and polyester were discussed. Good adhesion to poly(ethylene terephthalate) copolymer was found for low viscosity grafted polyethylene resins. A significant improvement in adhesive strength on polyester was observed when the molecular weight of the grafted LLDPE was increased. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3180–3191, 2004     

Study of compatibilization of HDPE–PET blends by adding grafted or statistical copolymers

The reactive compatibilization of blends of HDPE–PET [high‐density polyethylene–poly(ethylene terephthalate)] was investigated in this study. The compatibilizers used were two grafted copolymers prepared by reactive extrusion containing 1.20–2.30 wt % GMA such as HDPE‐g‐GMA and one statistical copolymer containing 1 wt % GMA such as Lotader AX8920. HDPE was successfully functionalized using a melt free‐radical grafting technique. Grafting was initiated in two ways: adding an initiator in the polymer–monomer mixture or activation by ozone of polymer. Ozonization of HDPE by the introduction of a peroxide lead to a better grafting yield and to better grafting efficiency of the samples. The effects of the three compatibilizers were evaluated by studying the morphology and the thermal and mechanical properties of HDPE–PET (70/30 wt %) blends. Significant improvements were observed, especially in morphology, elongation at break, and Charpy impact strength of the compatibilized blends. A more pronounced compatibilizing effect was obtained with the statistical copolymer, for which the elongation at break and the impact strength were increased by 100%, while the uncompatibilized blends showed a 60% decrease in the Young's modulus and the strength at break. We also were able to show that the grafting yield increase of 1.20–2.30 wt % of GMA did not affect the properties of the blends because the grafted copolymers possess very similar chemical structures. However, compatibilization of blends with grafted copolymers is an interesting method, particularly for recycled blends, because the synthesis of these compatibilizers is easy and cheap in comparison to statistical copolymer. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2377–2386, 2001     

Photografting of acrylamide on ethylene–vinyl alcohol copolymer film

Photografting (λ > 300nm) of acrylamide on ethylene-vinyl alcohol copolymer film (vinyl alcohol unit = 56 mol%, film thickness = 20μm) was investigated at 60°C in water medium, where photoinitiators were coated on the film earlier. The percent grafting decreased in the order of xanthone ≈ benzophenone > anthraquinone > benzoyl peroxide. The graft efficiencies in each sensitized system were less than 30%, showing a predominant formation of homopolymer. Grafting of acrylamide on the film was also initiated in systems with and without photoirradiation when ceric salt was used as an initiator. Based on electron probe microanalysis of the grafted films, the grafted chains of the sample prepared by photografting were distributed inside the film, while those of the sample prepared by ceric salt-initiated grafting without photoirradiation were located mainly on the film surface. The grafted films prepared by the former system exhibited a higher moisture permeability than those prepared by the latter system.     

Effect of stirring on cellulose graft copolymerization. III. Acrylic and methacrylic monomers

Acrylate and methacrylate monomers were grafted onto dissolving pulp by the xanthate process. All the nine monomers tested showed a well-defined dependence of conversion on stirring speed. Total conversion and conversion to copolymer vs. agitator speed curves for each monomer were very similar in shape, but they varied widely from monomer to monomer. For the homologous series acrylate and methacrylate esters, optimum stirring speed was found to increase with increasing the size of the alkyl group. The breadth of the maximum also depended on the type of monomer. Monomers partially soluble in water forming water-insoluble polymers were found to be the most reactive.     

Graft Copolymerization of Pectin with Polyacrylamide

In the present study, an attempt has been made to modify pectin by grafting polyacrylamide using ammonium ceric sulphate as initiator. The effect of various variables like initiator concentration, monomer concentration, temperature and time has been studied. The grafted copolymer was characterized by Fourier transform infrared spectroscopy (FT-IR), organic elemental analysis, differential scanning calorimetry (DSC) and X-ray diffraction (XRD). FT-IR studies indicated incorporation of amide group. Rheological behavior of pectin solution was compared with that of the grafted copolymer. The comparative rheological properties of pectin and grafted copolymer indicated change in the property of the product. Differential scanning calorimetry and XRD suggested formation of the grafted copolymer.     

Grafting of acrylonitrile onto cellulose initiated by ceric ion

Acrylonitrile was grafted onto cellulose with the use of ceric salt as initiator and the grafting was found to be maximum at 0.6N acid concentration. The effect of monomer and initiator concentration on the extent of grafting was studied. A new method for quantitative estimation of extent of grafting on cellulose was developed and its validity was established. The grafted samples with 20% increase in weight were found to be highly resistant to microorganisms.     

复合引发GMA熔融接枝POE及其增韧PBT的研究

采用双螺杆加工过程中的机械力引发同时添加引发剂的双重引发方法,研究了引发剂的用量、螺杆转速和接枝反应温度对甲基丙烯酸缩水甘油酯（GMA）接枝乙烯-辛烯共聚弹性体（POE）产物的接枝率、熔融指数的影响。对于单纯采用引发剂引发方法和引发剂与机械力双重引发方法所得接枝产物增韧聚对苯二甲酸丁二醇酯（PBT）的效果也进行了比较。后者在接枝物含量为30％时,可使PBT／POE—g—GMA共混材料的缺口冲击强度达到原未改性材料的22倍左右。