超细聚酰胺6粒子增韧聚丙烯体系的研究

采用磨盘形力化学反应器室温下制备了聚丙烯 (PP) /聚酰胺 6 (PA6 )超细粉体 ,研究了其粒度、粒度分布及PA6超细粒子填充对PP力学性能的影响 .结果表明 ,磨盘形力化学反应器可有效实现PP/PA6的粉碎 ,所得粉体平均粒径达微米级 ,初级粒子尺寸甚至可达纳米级 ,粒度分布呈双峰分布状态 .在PA6和PP熔点之间的温度下加工可制得PA6超细粒于填充的PP/PA6共混体系 ,其力学性能明显好于PP/PA6简单共混体系 ,30 %PA6用量下 ,拉伸强度由 2 3 .2MPa提高至 2 9 3MPa ,Izod缺口冲击强度由 4.6 2kJ/m2 提高到6 .34kJ/m2 .形貌分析结果表明 ,由于基本保持了PA6超细粉体的原始尺寸 ,填充体系中PA6相区尺寸小、分布均匀 ,与使用增容剂得到的相区结构类似 .     

磨盘碾磨制备PA6/PP/SBS共混物的结构与性能

采用磨盘形力化学反应器,在室温下制备了PA6/PP超细混合粉体,与SBS共混制得PA6/PP/SBS共混物,测定了材料的力学性能并用TEM研究了材料在不同加工温度下相结构的变化.结果表明,通过固相力化学粉碎制备的PA6/PP混合微粉,改善了PA6与PP和SBS的相容性,促进了PA6及PP的分散和与SBS的相界面结合.在微粉填充量为4%～8%(质量分数)时,材料的拉伸强度大幅度提高,扯断伸长率保持不变.加工温度变化引起材料相结构的变化对材料性能产生显著影响.在PP熔融温度下加工,PP粒子产生粘连形成链状结构,可提高材料的力学性能.     

磨盘碾磨聚丙烯粒度分布与接枝率的研究

用分形几何方法研究了磨盘碾磨中聚丙烯 (PP)的粉碎和固相力化学接枝 .用粒度分析仪测定经磨盘碾磨聚丙烯的粒度分布 ,用分形理论处理实验数据 .结果表明 ,PP粒度分布存在无标度区 ,具有线性分形特征 ,磨盘碾磨对PP粒子分形行为有较大影响 ,聚丙烯粒度分布的分维值随碾磨次数的增加而增大 .磨盘碾磨中聚丙烯固相力化学接枝的实验结果表明 ,N 羟甲基丙烯酰胺在聚丙烯表面上的接枝率亦随碾磨次数增加而增加 ,即与聚丙烯粒度分布的分维值相关 .因此 ,可用分数维定量描述聚丙烯粒子在磨盘碾磨中的粉碎规律 ,揭示了N 羟甲基丙烯酰胺在聚丙烯表面固相力化学接枝反应的本质 .     

石墨填充高密度聚乙烯基复合材料导热性能的研究

选用导热系数较高的无机填料石墨对高密度聚乙烯(HDPE)进行填充改性;采用偶联剂和磨盘型力化学反应器对石墨进行表面处理,提高石墨与聚合物基体的界面相互作用;用自行研制的升温速率测定装置测试材料的导热性能,并研究材料的导热机理;用SEM观察复合材料的微观形态.实验结果表明:经偶联剂处理后,石墨在HDPE中均匀分布;测试试样的上表面温度随时间的变化可用三次多项式T=A₀+A₁t+A₂t²+A₃t³拟会;HDPE/石墨复合材料升温速率随石墨含量增加而增大;石墨含量为35％的复合材料最大升温速率为HDPE的1.75倍.     

磨盘碾磨力场作用下聚丙烯/石墨体系中聚丙烯晶态结构的变化

通过磨盘碾磨制备了PP 石墨复合粉末 .用FT IR ,XRD和DSC表征了磨盘剪切力场作用下 ,PP 石墨体系中 ,聚丙烯结构与性能的变化 .结果表明 ,磨盘碾磨使PP有序结构破坏 ,分子链断裂并与石墨的表面官能团之间发生了固相力化学反应 ,导致其结晶度降低 (由 5 7 2 %降低到 2 6 4%) ,晶面间距增大 ( ( 0 1 0 )面由 0 62 3nm增加到 0 63 2nnm) ,晶粒尺寸减小 (由 1 2 83nm减小到 6 48nm) ,这些变化 ,在热压成型的非等温过程中部分得到恢复 ,且α 晶的 ( 0 40 )面生长有择优性 ,其XRD强度大大超过 ( 0 1 0 )面 ,微晶尺寸更大 .同时发现 ,在PP 石墨复合粉末和复合材料中 ,α 单斜晶部分地转化为γ 三斜晶 ,在PP 石墨复合材料中 ,γ 三斜晶占 3 4 8%.     

声化学反应器基础理论的研究进展

论述了声化学反应器的基础理论,主要涉及反应器中的声化学反应动力学、空化声场中空化泡的分布和检测方法,以及声化学反应器的放大理论,包括反应效率和经济性估算。     

固相力化学改性高聚物的方法研究

在固相应力作用下高聚物分子结构可被削弱或破坏,化学键可能发生畸变或断裂。固相力化学改性高聚物是研究各种高聚物因机械力影响而发生化学或物理化学变化的方法。由于该方法具有适用性广、产品纯净、操作方便、效率高、简便、节能、无污染等优点而成为高聚物改性的重要方法之一。本文系统综述了高聚物的固相剪切粉碎、固相磨盘型碾磨粉碎、高能...     

量子化学模型方法在机械力化学中的应用

机械力化学作为一种无需溶剂的绿色化学技术得到广泛关注。然而,机械力化学反应机制需要从原子和分子尺度上深入理解力诱导的化学反应。在过去的20年中,量子化学模型方法在机械力化学机理研究中得到广泛应用,高精度量化计算可得到外力下变形分子的几何结构、能量、过渡态等诸多性质。本文介绍了目前机械力化学领域的主流量子化学模型的基本原理,同时也关注了这些模型方法在软件上的具体实现,并借助典型的案例阐述了量子化学模型在解释机械力化学机理中的作用与价值。     

前线轨道在磁场中的特殊作用

通过对电磁学理论中洛仑兹力实质的研究，探讨了磁场中前线轨道的特殊作用。提出了磁场影响化学反应的可能机理是洛仑兹力改变前线轨道的伸展状态，以及由此影响化学反应速度和产物结构的观点，并进行了实验验证。     

PbS纳米粒子与全共轭高分子的自组装膜原位复合及其光电转换性质

无机纳米粒子因其在催化、磁学、光子学等方面的特殊性质而越来越受到关注,纳米粒子粒径及分布可以人为控制,由此能够改变与有机聚合物所形成的纳米复合材料性能,在各种无机纳米粒子／有机聚合物复合材料制备方法中,纳米反应器(Nanoreactor)技术正日益受到关注,与常规的作为化学反应特定场所的化学反应器不同,纳米反应器不是一般的具体的机械设备,     

Preparation of Intumescent Flame Retardant Polypropylene composite through Solid State Mechanochemical Method

Polypropylene (PP), with characteristics of good mechanical properties, good resistance to water and low cost, has been widely used in many fields such as building, transport, furniture and electrical industries. However, a fateful drawback of polypropylene is its high flammability,restricting its wider applications. Addition of flame retardants is an effective way to improve its flame retardancy. An effective halogen-free flame retardant system used is the mixture of melamine, ammounium phosphate and pentaerythritol (intumescent flame retardant). But how to enhance the dispersion of this mixture in polypropylene matrix is a big problem. A self-made mechanochemical reactor, pan type milling equipment, can exert strong shear and squeeze forces,and has good mixing function. As a result, a uniform dispersion of flame retardants in the polymer matrix can be expectably obtained by using this equipment.In this paper, flame-retarded Polypropylene (PP) composites with intumescent flame retardant (IFR) were prepared via solid state mechanochemical method (pan-mill) and conventional method (twin-roll masticator) respectively. Particle diameter analysis, melt flow index (MFI), differential scanning calorimetry (DSC) and scanning electronic microscopy (SEM) were used to characterize these composites, and the mechanical properties and flame retardancy were also determined. The experimental results showed that the blend of PP and IFR were effectively pulverized from 3～4 mm to less than 300i m under the strong shear forces of pan-mill. With increasing the milling cycles, the MFI value of IFR/PP blend decreased first and then increased. The mechanical properties and flame retardancy of IFR/PP blends prepared by solid state mechanochemical method were proved to be better than those prepared by conventional method because of the dispersing function of pan-mill.Also it was found that IFRs were the nucleating agent for PP and the crystallinity of PP increased first and then decreased with increasing the milling cycles.     

Morphological and structural development of hardwood cellulose during mechanochemical pretreatment in solid state through pan-milling

Mechanochemical pretreatment of hardwood cellulose was conducted by our self-designed pan-mill equipment which has an unique and smart structure and can exert strong shear forces and pressure on materials in between and break them down. The structure transformations, including particle size, powder morphology, molecular structure, crystalline structure during milling were investigated by Laser Diffraction Particle Size Analyzer, SEM, FT-IR and WAXD, respectively. Compared with standard method of ball-milling, the pan-mill shows a much higher efficiency in mechanochemical pretreatment of hardwood cellulose. The average particle size reduced to 21 μm and the specific surface area increased to 0.8 m²/g after 40 milling cycles. Mechanical milling also led to collapse of hydrogen bonds and reduction of crystallinity. The crystallinity index of cellulose powder decreased from its original 65 to 22, after milling for 40 cycles. Thermal analysis and solubility testing illustrated that pan-milled cellulose has lower thermal stability and higher solubility in aqueous alkali.     

EFFECT OF PAN-MILLING ON RHEOLOGICAL PROPERTIES OF HIGH DENSITY POLYETHYLENE*

The effect of pan-milling on the rheological properties of high density polyethylene (HDPE) was studied. Aninnovative milling apparatus, viz. an inlaid pan-mill, was used. Melt indexer, capillary rheometer, Haake Rheocord 90 single-screw extruder and Brabender rheometer were used to evaluate the rheologieal properties of HDPE. HDPE with higher initialmolecular weight and larger particle size was easier to degrade under pan-milling stress, as indicated by the melt index.Pressure oscillation in capillary flow occurred at significantly higher shear stress and shear rate for milled HDPE than forunmilled HDPE. The apparent shear viscosity of HDPE decreased with increasing times of milling. After milling, the flowactivation energy decreased and thus the sensitivity of viscosity to temperature was reduced. Die pressure and torque duringsingle screw extrusion were reduced significantly after milling. Plasticizing time as measured in a Brabander mixer decreasedmarkedly with increasing milling times.     

Selecting parameters and limits for equipment operational qualification

While operational qualification (OQ) is a well-established term within equipment qualification, users of equipment often become unsure when it comes to implementation. The biggest problem is how to select procedures and acceptance criteria. Should these be the vendor's specifications or should the users define their own limits, and, if so, how? Should all instruments of the same type have the same values or should these be optimized for each individual instrument? This article will provide an overall strategy and specific examples for HPLC on how to select procedures and acceptance limits that are based on efficient use of resources, on practicality and on the intended use of the equipment.     

A practical preparation of aryl β-ketophosphonates

The condensation of alkyl phosphonates with aryl esters to give β-ketophosphonates may be carried out at elevated temperatures mediated by LiHMDS under Barbier type conditions. The reaction is scalable, does not require specialized cryogenic equipment, and is general for all aryl and heteroaryl esters examined.     

The derivatograph-C

The latest type of derivatograph, operated by a microcomputer, is described. The equipment is suitable for simultaneous TG, DTG, DTA, TD and EGA measurements under dynamic, isothermal, quasi-isothermal and quasi-isobaric heating conditions. As practical examples, the decompositions of bauxite and manganese(II) sulphate pentahydrate are demonstrated.     

Dynamic mechanical analysis of the SAN co-polymer and the SBR latex co-mixture

Useful experimental data based on the dynamic effects of the SAN/SBR mixture at higher temperatures were acquired. This data can allow us to gather information about the molecular motion and any interesting behavior of this mixture at elevated temperatures and increases in the SAN to SBR weight proportion. The importance of dynamic mechanical experiments of multi-phase polymer systems is presented. A series of (SAN/SBR) co-mixed samples were prepared with varying weight proportions over a temperature interval. TBA equipment (a type of torsional braid set of equipment) was used to make the dynamic mechanical analysis of the SAN/SBR co-mixture.     

Mechanochemical and Size Reduction Machines for Biorefining

In recent years, we have witnessed an increasing interest in the application of mechanochemical methods for processing materials in biomass refining techniques. Grinding and mechanical pretreatment are very popular methods utilized to enhance the reactivity of polymers and plant raw materials; however, the choice of devices and their modes of action is often performed through trial and error. An inadequate choice of equipment often results in inefficient grinding, low reactivity of the product, excess energy expenditure, and significant wear of the equipment. In the present review, modern equipment employing various types of mechanical impacts, which show the highest promise for mechanochemical pretreatment of plant raw materials, is examined and compared—disc mills, attritors and bead mills, ball mills, planetary mills, vibration and vibrocentrifugal mills, roller and centrifugal roller mills, extruders, hammer mills, knife mills, pin mills, disintegrators, and jet mills. The properly chosen type of mechanochemical activation (and equipment) allows an energetically and economically sound enhancement of the reactivity of solid-phase polymers by increasing the effective surface area accessible to reagents, reducing the amount of crystalline regions and the diffusion coefficient, disordering the supramolecular structure of the material, and mechanochemically reacting with the target substances.     

Direct Mechanocatalysis: Using Milling Balls as Catalysts

Direct mechanocatalysis describes catalytic reactions under the involvement of mechanical energy with the distinct feature of milling equipment itself being the catalyst. This novel type of catalysis features no solubility challenges of the catalysts nor the substrate and on top offering most facile way of separation.     

A new sensing material for optical oxygen measurement,with the indicator embedded in an aqueous phase

A new type of oxygen-sensitive material is obtained by preparing an aqueous emulsion of a solution of an oxygen-sensitive fluorescent dye in a rigid polymer. The fluorescence of this emulsion is related to the oxygen partial pressure, but a Stern-Volmer plot is not linear over the whole pressure range. Aside from high sensitivity and specificity for oxygen, this new type of sensing material has favorable analytical wavelengths allowing the use of low-cost opto-electronic equipment. Since the indicator is embedded in an aqueous environment, the sensor should be capable of monitoring various kinds of reactions occurring in the aqueous phase, for instance enzymatic reactions which are accompanied by production or consumption of oxygen.