加速老化贮存过程中子午线轮胎专用NR性能变化的研究

研究在70℃加速老化贮存过程中子午线轮胎专用NR生胶、混炼胶和硫化胶性能的变化。结果表明，随着加速老化贮存时间的延长，生胶的快速塑性值、塑性保持率和门尼粘度均呈线性减小趋势；混炼胶的ML和MH降低，ts1,ts2,t10和t90延长；硫化胶的硬度、拉伸强度和拉断伸长率呈减小趋势，抗湿滑性能和滚动阻力基本保持不变。     

制备工艺对NR性能的影响

采用新鲜天然胶乳分别制备乙酸凝固NR(NR-1)、微生物凝固NR(NR-2)、乙醇胺混合微生物凝固NR(NR-3)和蛋白酶混合自然凝固NR(NR-4),研究制备工艺对NR性能的影响。结果表明:NR-1和NR-2生胶的耐热老化性能和热稳定性好于NR-3和NR-4生胶;NR-4胶料的MH最大,t90最短,NR-3胶料的MH较小,t90最长;NR-4硫化胶的定伸应力和拉伸强度较大,拉断伸长率较小,NR-1硫化胶的定伸应力和拉伸强度较小;NR-4生胶、混炼胶和硫化胶的弹性转矩(S′)和剪切储能模量(G′)最大,损耗因子(tanδ)最小,NR-1生胶、混炼胶和硫化胶的S′和G′最小,tanδ值最大。     

微生物凝固天然橡胶的性能研究

研究微生物凝固鲜胶乳工艺对天然橡胶(NR)性能的影响。结果表明:纯微生物凝固NR生胶的门尼粘度、塑性初值(P0)和塑性保持率均高于甲酸凝固NR,加入助凝剂氯化钙后仍表现出较甲酸凝固NR硫化速率快、拉伸强度大、拉断伸长率高等优良性能;随着微生物凝固剂用量的增大,NR生胶的P0小幅下降,灰分质量分数有所增大;随着助凝剂用量的增大,NR生胶的门尼粘度小幅下降,塑性保持率呈增大趋势;微生物凝固剂和助凝剂用量对NR胶料的硫化特性和老化前后物理性能无明显影响。     

微生物凝固NR和酸凝固NR的性能对比

对微生物凝固NR(NR-m)和酸凝固NR(NR-a)的性能进行对比.结果表明,NR-m胶料的t10,t60和t90显著短于NR-a胶料,NR-m硫化胶的交联密度、定伸应力和拉伸强度远高于NR-a硫化胶,证明微生物凝固法可促进NR的硫化,使NR-m硫化胶的网络分子结构比较紧密,表现出比NR-a硫化胶更好的物理性能.     

微生物凝固天然橡胶与酸凝固天然橡胶的性能差异

为揭示微生物凝固天然橡胶(NR-w)和酸凝固天然橡胶(NR-a)的性能差别,制备了3个系列的NR,并对其性能进行了全面的研究.结果发现,在生胶性能方面,NR-w凝胶含量和塑性初值均高于NR-a,而分子量低于NR-a.对于硫化胶,NR-w纯胶硫化胶的力学性能远高于NR-a纯胶,而NR-w炭黑胶的力学强度与NR-a炭黑胶很接近;此外,NR-a纯胶的抗老化性能远高于NR-w,其炭黑胶的抗老化性能也高于NR-w,在硫化性能方面,NR-w的转矩增大速率快于NR-a,强度也比NR-a高.在动态性能方面,NR-w的抗湿滑性能和滚动阻力均高于NR-a.     

湿凝固胶片悬挂时间对天然橡胶性能的影响

研究乙酸凝固和自然凝固所得湿凝固胶片悬挂时间对天然橡胶性能的影响。结果表明:随着湿凝固胶片悬挂时间的延长,湿凝固胶片的热风干燥所需时间缩短,生胶的氮含量减小,凝胶含量、交联密度和门尼粘度增大;混炼胶的正硫化时间(t_(90))先缩短后稳定;自然凝固硫化胶的拉伸强度变化不大,拉断伸长率先提高后下降,湿凝固胶片悬挂时间超过12 d后乙酸凝固硫化胶的拉伸强度下降,拉断伸长率变化不大。与乙酸凝固的湿凝固胶片相比,自然凝固的湿凝固胶片的热风干燥时间略长,生胶的氮含量较小,凝胶含量、交联密度和门尼粘度较大,硫化胶的拉伸强度较高。     

氮含量对木瓜蛋白酶凝固天然橡胶性能的影响

利用木瓜蛋白酶凝固天然胶乳制备了不同氮含量的天然橡胶（NR-P）,研究了NR-P的生胶理化性能和混炼胶硫化特性,以及硫化胶的物理机械性能、压缩疲劳生热和动态力学性能,并与酸凝天然橡胶（NR-A）进行了对比。结果表明,随着氮含量的降低,NR-P的塑性初值先降低再趋于稳定,塑性保持率则稍有下降;混炼胶的硫化速率增大;硫化胶的300%定伸应力和拉伸强度均呈现先增大后稍有减小的趋势,压缩温升和滚动阻力都基本呈现减小趋势。与NR-A相比,NR-P的氮含量较低,但其塑性初值较高而塑性保持率稍低,硫化速率及拉伸强度也优于NR-A。当含氮质量分数处于0.18%～0.23%时,NR-P具有较快的硫化速率,较好的物理机械性能、压缩疲劳生热性能和动态力学性能。     

生物凝固天然橡胶的性能及其在子午线轮胎中的应用

研究生物凝固天然橡胶(NR-B)的性能及其在子午线轮胎中的应用,并与马来西亚20~#天然橡胶(SMR20)进行对比。基本性能试验结果表明,与SMR20相比,NR-B的塑性初值和塑性保持率较高,混炼胶的焦烧性能较好,硫化速率较快,硫化胶的定伸应力较小,拉伸强度较大。小配合试验结果表明,与SMR20相比,NR-B配方胶料的拉伸强度、拉断伸长率、撕裂强度和抽出力较大,耐磨性能和耐热空气老化性能较好,但门尼粘度较大,加工性能略差。NR-B可以替代SMR20应用于子午线轮胎生产,但在生产过程中需对其工艺进行适当调整。     

恒粘处理生物凝固胶性能的研究

对生物凝固胶用粘度稳定剂进行不同恒粘处理，研究了不同处理方法对生物凝固胶的塑性初值(Po)、塑性保持指数(PRI)、氮含量、门尼粘度、加速贮存硬化值(△P)和硫化胶的物理机械性能等的影响。结果表明，经恒粘处理后的生物凝固胶的△P较小，氮含量相对较低，其它性能虽有变化，但均能达到天然生胶标准的要求，尤其以恒粘处理2h的生物凝固胶的综合性能最好。     

两种方法凝固天然橡胶的动态性能对比

分别采用自然凝固和酸凝固方法制备天然橡胶(NR),并比较2种方法凝固NR的交联密度、硫化特性、动态性能和生热等的差异。试验结果表明,自然凝固NR的交联密度和弹性模量较高,硫化速度快,动态损耗小,生热低。     

Magnesia induced coagulation of aqueous PZT powder suspensions for direct coagulation casting

Coagulation characteristics of poly(acrylate) dispersed PZT powder suspensions by MgO coagulating agent have been studied. The PZT powder suspensions undergoes coagulation at MgO concentrations much lower than the equivalent amount to react with the dispersant indicating a major shift in the coagulation mechanism from the corresponding alumina powder suspensions. Unlike in alumina powder suspensions, the Mg²⁺ ions generated from the MgO reacts with the ammonium poly(acrylate) adsorbed on particle surface that result in cross-linking of PZT particles by Mg²⁺ through the ammonium poly(acrylate) molecules. The particle bridging induces faster coagulation of the slurry cast in a mould as required for an ideal DCC process. The compressive strength and stability against oscillatory stresses of the wet-coagulated bodies increased with increase in number of cross-links between the particles. The PZT green bodies prepared by the DCC process sintered to near theoretical density and the MgO added as coagulating agent (～0.1 wt%) had only minor influence on its piezoelectric characteristics.     

强化混凝技术的研究进展

综述了强化混凝技术的研究现状,包括原有混凝剂潜力的挖掘、新型混凝剂的研发、反应条件的优化以及混凝设备等对混凝效果的强化,结合目前研究现状及水处理的实际需要,指出了进一步研究中急需解决的问题,以期为我国强化混凝技术的研究与应用提供参考。     

STAGO全自动血凝仪在人凝血因子活性测定上的应用

目的探讨STAGO全自动血凝仪在人凝血因子活性测定上的应用。方法对STAGO全自动血凝仪按照GMP要求进行安装确认(installation qualification,IQ):实施信息核查并记录;运行确认(operational qualification,OQ):准确度、精密度(批内精密度及批间精密度)、干扰试验及参考范围的验证确认;性能确认(performance qualification,PQ):按STAGO凝血分析仪相关SOP检测6份人凝血因子Ⅷ样品活性,并计算6份样品检测值间的相对标准偏差(relative standard deviation,RSD)。结果已核实STAGO全自动血凝仪基本信息,安装环境及安装过程均符合要求,并已进行记录。厂家提供的正常及病理值质控血清测定3次的均值均在厂家提供的质控范围内;批内及批间精密性的变异系数(coefficient of variation,CV)均10%;随机组与对照组相比平均偏差10%;20份体检样本的均值、标准偏差(standard deviation,SD)及结果在正常参考范围的例数与总标本数的比例(R值)0.9。6份人凝血因子Ⅷ样品检测值的RSD值为1.95%。结论经全面的设备确认,STAGO全自动血凝仪符合人凝血因子活性测定的要求。     

凝固浴氨化对PAN湿法纺丝凝固行为的影响

在二甲基亚砜/水(DMSO/H_2O)凝固体系中加入氨水,以pH值控制凝固浴氨化程度,研究了凝固浴氨化对聚丙烯腈(PAN)湿法纺丝凝固行为的影响;采用扫描电子显微镜表征PAN初生纤维的皮层结构,采用卡尔费休水分仪和气相色谱仪研究了氨化对水和DMSO扩散系数的影响。结果表明:当凝固浴pH值为8.0时,PAN初生纤维的皮层最薄;随着凝固浴pH值的增大,水的扩散系数逐渐减小,DMSO的扩散系数(D_(DMSO))先减小后增大,当pH值为8.0时,D_(DMSO)出现最小值;氨化的作用机理是通过氨与水和DMSO分子间的氢键作用来实现的。     

混凝试验中效果评判的新方法

通过对两类不同的水源进行混凝试验,发现用混凝后水的浊度来评判混凝效果的方法,对一般水质的水源是有效的,但对某些特殊水质的水源如低温低浊水,或对混凝处理后水质要求较高的场合如反渗透进水,就无法准确找出最佳的混凝剂和混凝条件.因此,提出了用测量矾花(絮凝体)大小及生长速度和泥渣虚度的指标来评判混凝试验效果的新方法,与常用的以混凝后水的浊度来评判混凝效果相比,用此方法更能准确地评判混凝试验效果的优劣.     

Controlled coagulation of emulsion polymers

Coagulation of latex particles is most often carried out in the diffusion limited aggregation (DLA) regime where the time for coagulation to take place is on the millisecond timescale. This process produces aggregates of low density, irregular shape, and a broad particle size distributions. When the coagulation is carried out in the reaction limited aggregation (RLA) regime, a coagulation time of about 1–120 sec, the system can be controlled by mixing to yield dense, spheroidal aggregates with a very narrow particle size distribution. The important variables in the RLA process for butyl acrylate/methyl methacrylate (BA/MMA) latexes were found to be mixing intensity, latex copolymer composition, and coagulation temperature. Dried aggregates formed in the RLA process were found to have excellent powder flow properties and low dustiness.     

聚丙烯酸酯胶乳的凝聚

采用甲基丙烯酸甲酯、丙烯酸丁酯经种子乳液聚合得到聚丙烯酸酯类接枝聚合物(AIM)乳液,在此AIM乳液中加入凝聚剂硫酸镁(MgSO4)或氯化铝(AlCl3)水溶液进行凝聚,以制备抗冲击改性剂粉料。讨论了凝聚剂种类、搅拌时间和凝聚剂浓度等条件对凝聚过程的影响。结果表明:AlCl3的凝聚能力比MgSO4的凝聚能力强;AlCl3盐浓度由0.05 mol/L增至0.2mol/L,聚合物粉料的表观密度值由0.26 g/cm3增加到0.48 g/cm3。     

Kinetics of pseudo-boehmite sol coagulation

The kinetics of coagulation of spherical drops of the sol obtained in an ammonia solution by peptization of pseudo-boehmite with nitric acid has been investigated. The chemical reaction rate constants and coefficients of the ammonia cations diffusion in the formed gel were calculated from the experimental data in accordance with the model of a particle with noninteracting core.     

Mechanical coagulation in emulsion polymerizations

Coagulum formation for different emulsion polymerizations was correlated to various agitation parameters. For low Reynolds numbers, rotational speed was shown to be important, whereas, for high Reynolds numbers, power consumption was the important parameter. These results were theoretically tied to first-order coagulation kinetics by incorporating shear rate relationships for flow in an agitated tank. For low Reynolds numbers, the average shear rate was assumed to be proportional to the rotational speed of the impeller. And for high Reynolds numbers, Kolmogorov's theory of locally isotropic flow was employed to relate the average shear rate to the power consumption.