顺丁生胶加工行为的流变学表征

<正> 对于不同聚合条件下得到的顺式1,4-聚丁二烯生胶,往往加工行为差异较大,而用传统的溶液分子量测定,门尼粘度等方法不能很好地表征。五十年代以来,发展了以应力松弛求得最大松弛时间的方法,及采用毛细管流变仪研究。关于生胶加工行为与流变性质和高分子结构的关系,已有不少报道。对于顺丁橡胶,不同研究者强调的因素有:     

Tearing of unvulcanized natural rubber

The tear behavior of unvulcanized natural rubber has been studied by using established techniques normally adopted for the study of vulcanized rubbers. Unvulcanized rubber has been found to tear in a relatively steady manner, in contrast to the stick-slip tear behavior of the vulcanized rubber, the tearing energy being dependent on the rate of tearing. Crystallization seems to be an important factor in determining the tear behavior since it has not been found possible to tear unvulcanized SBR under the same conditions. The effect of the pronounced imperfect elastic nature of the material was studied under conditions where the driving force for tearing was solely governed by the rate of release of elastic energy. Under such conditions, it has been found that the tearing energy is determined not by the strain energy required to stretch the material but by the energy which can be recovered on retraction. The set developed in the test piece, due to imperfect elasticity, has also to be taken into account.     

~(13)C-NMR研究聚丁二烯的链结构——顺-1,4与1,2-乙烯基-CH-键合点的S峰

<正> 聚丁二烯(简写PB)是合成橡胶中的一个重要品种,它由顺式-1,4(简写C)、反式-1,4(简写T)和1,2乙烯基(简写V)三种基本单元构成。PB的性能不仅与上述三种结构单元的相对含量与分子量有关,还和C、T、V之间的连接方式,即序列结构有关。例如,高-1,4顺丁橡胶性能有不足之处,在开展改性的PB新品种(如顺丁链结构中引进不同量的T、V链节等)的研究中,对不同催化剂制备的不同序列的PB进行链结构表征,从而找出有关结构与性能的关系,是十分有意义的。     

Filler-filler interaction and filler-polymer interaction in carbon black and silica filled ExxproTM polymer

Due to the presence of reactive benzylic bromide, Exxpro has much better interaction with silica in comparison with polybutadiene as demonstrated by the high bound rubber level. The better silica/Exxpro interaction is further substantiated by the low degree of filler network formation in comparison to that observed for silica filled polybutadiene as demonstrated by the much smaller deviation of low strain shear modulus from the Guth-Gold relationship for the silica filled Exxpro. Silane treatement of silica reduces filler network formation in polybutadiene but has only slight effect on silica filled Exxpro indicating that even without silane treatment silica already disperse well in Exxpro due to high degree of filler/polymer interaction. This result in silica filled Exxpro compound exhibiting better processability (lower shear viscosity) as well as dynamic performances for tire applications (higher tan δ at −20 and 0°C, lower tan δ at 60°C). We speculate that nucleophilic substitution reaction takes place between benzylic bromide and surface hydroxide group of silica.     

茂金属 乙烯的流变性与加工性

研究了丁烯－１共聚的茂金属聚乙烯（mＰＥ）的流变性,发现茂金属聚乙烯的窄分子量分 布导致它在挤出加工剪切范围里熔体粘度高、对剪切敏感性差以及熔体从牛顿型转为非牛顿型所需的剪切速率、转变应力高,在挤出加工条件下流动性差,加工困难。对茂金属聚乙烯（mＰＥ）进行改性制得ＭmＰＥ,ＭmＰＥ熔体对温度、剪切速率的敏感性提高,在加工温 度、加工剪切范围里的天观粘度降低,加工流动性得到了显著的改进,可在普通聚乙烯加工     

茂金属聚乙烯的流变性与加工性

研究了丁烯 １ 共聚的茂金属聚乙烯（ｍＰＥ） 的流变性,发现茂金属聚乙烯的窄分子量分布导致它在挤出加工剪切速率范围里熔体粘度高、对剪切敏感性差以及熔体从牛顿型转为非牛顿型所需的剪切速率、转变应力高,在挤出加工条件下流动性差,加工困难．对茂金属聚乙烯（ｍＰＥ） 进行改性制得ＭｍＰＥ,ＭｍＰＥ 熔体对温度、剪切速率的敏感性提高,在加工温度、加工剪切速率范围里的表观粘度降低,加工流动性得到了显著的改进,可在普通聚乙烯加工设备上,制备性能优良的茂金属聚乙烯薄膜制品．     

端羟基聚丁二烯预聚物的表征

本文用VPO、IR、GPC、TLC方法表征国产端羟基聚丁二烯(HTPB),其结果是:Mn为3220,Mw/Mn为1.69,f_n为2.16,f_w为2.27。证明国产HTPB预聚物的数均官能度随分子量增加而增加。探讨了用TLC法研究HTPB官能度分布的可靠性。     

以红外3100～2800cm-1谱分析聚丁二烯

研究了红外3100～2800cm^-1谱区的聚丁二烯图谱,它是聚丁二烯的顺-1,4,反-1,4和1,2微观结构信息叠加谱区。用因素分析技术对聚丁二烯的微观结构进行了定量分析,与传统的分析方法和其它谱区的因素分析进行比较,结果显示3100～2800cm^-1港区的因素分析为现用方法中最佳。     

聚丁二烯1,2-结构含量和SBS中聚丁二烯段1,2-结构含量的调节

以正丁基锂为引发剂,环己烷为溶剂,研究了四氢呋喃(THF)对聚丁二烯1,2-结构和丁苯嵌段共聚物SBS中聚丁二烯段1,2-结构含量的影响,指出在一定温度下,聚丁二烯1,2-结构含量与体系中THF的浓度有指数关系。控制体系中THF的浓度和聚合反应温度,可调节聚合产物中聚丁二烯1,2-结构含量。     

聚丁二烯的链节结构与其氧化性能的关系

利用不同催化剂体系的定向聚合,可使丁二烯聚合成双键在主链和侧基中分布不同的聚合物。对于这些聚合物的氧化性能,尽管早期有人利用不同单体单元的均聚物和共聚物如天然胶、古塔坡胶以及丁钠、丁锂、丁苯、丁基胶等作过比较,认为丁二烯橡胶分子主链和乙烯侧基上所含双键的比例可以极大地影响其反应能力,主链上双键在氧化时较活泼,而乙烯侧基上的双键则在热交联时较活泼。     

长序列乙烯-丁二烯共聚物的合成

研究了稀土催化剂催化乙烯-丁二烯的共聚合。结果表明,在封管条件下用稀土催化剂可以使乙烯-丁二烯共聚,产生高分子量聚合物。产物的溶液性质表明,不含聚乙烯均聚物,含约8％的聚丁二烯均聚物。DSC、X-射线衍射、电子显微镜和~(13)C-NMR等实验表明,所得聚合物是含长乙烯-乙烯序列的乙烯-丁二烯共聚物,其中聚丁二烯链段的微观结构以顺-1,4构型为主。共聚物中乙烯单元增加,乙烯-乙烯链段的熔点和结晶度增高,晶粒尺寸变大,晶胞参数基本不变。共聚物的力学性能表明,其生胶强度可达20—30kg/cm~2,远比聚丁二烯的强度大。     

天然橡胶/聚乙烯共混体相容性的研究

本工作首先对橡胶/聚乙烯共混体系的相容性进行了计算,推测聚乙烯的非晶部分和橡胶间有一定的互容性,提出了橡胶和聚乙烯相互作用模型。然后用动态力学方法、有效网链密度测定、密度测定和广角X-射线衍射方法对天然橡胶分别未交联和交联的天然橡胶(NR)/低密度聚乙烯(LDPE)共混体系的相容性进行了验证。实验结果表明,LDPE非晶部分和NR之间存在一定的相互渗透。     

Correlations between gas permeation and free-volume hole properties of polyurethane membranes

A series of polyurethane films based on hard segments consisting of toluene diisocyanate and 1,4-butanediol and different soft segments consisting of hydroxyl terminated polybutadiene, hydroxyl terminated polybutadiene/styrene and hydroxyl terminated polybutadiene/acrylonitrile were synthesized by solution polymerization separately. Positron annihilation lifetimes were measured at room temperature for all samples studied. We found that both the free volume size and fractional free-volume decreased with the increase of hard segment content. On the other hand, direct relationship between the gas permeability and the free-volume has been established based on the free-volume parameters and gas diffusivity measured. Experimental results revealed that the free-volume plays an important role in determining the gas permeability.     

丁二烯－八甲基环四硅氧烷的嵌段共聚合研究 Ⅰ．嵌段共聚物合成及D_4开环动力学

以α－甲基萘钾为引发剂，按顺序加入丁二烯、八甲基环四硅氧烷（Ｄ４）在ＴＨＦ中进行负离子嵌段共聚，制备了聚了二烯－聚二甲基硅氧烷嵌段共聚物．讨论了聚合条件对嵌段共聚合过程的影响．考察了聚了二烯活性链引发Ｄ４进行嵌段共聚的反应动力学，求得在ＴＨＦ中３０℃时Ｄ４开环链增长的表观速率为１０ｋｇ／ｍｏｌ．ｈ、表观活化能为２８．３ｋＪ／ｍｏｌ．     

Etude de copolymères ABS (acrylonitrile–butadiène–styrène): Solvatation préférentielle du polybutadiène par les promoteurs

ABS resins formed by copolymerization of styrene and acrylonitrile (AN) in presence of polybutadiene, consist of a mixture of SAN graft copolymer on polybutadiene (PBut) and of ungrafted SAN copolymer (styrene-co-acrylonitrile). The kinetic study was completed by showing a preferential solvation of polybutadiene by the initiator. This solvation effect was studied as a function of the concentration ratio SAN/PBut and in relation with the type of initiator. The adsorption of initiator appeared to be maximum when its solubility parameter (σ) is close to that of polybutadiene. As a function of the polybutadiene characteristics, this selective adsorption can be given by where I₁ is the quantity of initiator in the polybutadiene medium, I is the total amount of peroxide, [PBut] is the concentration of polybutadiene, and M?_n its molecular weight. It has been shown furthermore that the preferential solvation of polybutadiene by the benzoyl peroxide can be increased by addition of SAN or acrylonitrile. The consequences of this solvation effect on the characteristics of the grafting reaction, more precisely on the molecular weight of grafted and ungrafted SAN and on the rate of polymerization, were examined.     

有较高抗撕裂强度的稀土顺丁充油橡胶的研究

本工作采用电子显微镜(EM)、大角度X射线衍射(WAXD)、热失重分析(TGA)、动态力学测定等方法,研究了几种典型油品的充油Ln-BR的形态结构和结晶动力学,发现减压渣油(9号油)分子量较高,与Ln-BR的相容性较差,且与硫化后的Ln-BR间可能有少量的化学联结。它的存在明显地促进了Ln-BR的应力诱导结晶(SIC)。这些因素均导致这种充油硫化胶有较高的抗撕裂强度。     

梳状聚丁二烯的合成及表征

以次氯酸叔丁酯为氯化剂,在无降解及交联情况下,向阴离子聚合的聚丁二烯主干引入活泼氯。氯化聚丁二烯与活性聚丁二烯阴离子(PB~(?))偶合得到支链沿主干无规分布的梳状聚丁二烯。降低偶合温度,提高[PB~(?)]/[Cl]比值及加入极性溶剂四氢呋喃,均有利于提高偶合接枝效率。渗透压法及GPC法的表征结果表明,沉淀分级净化产物为具有窄分子量分布主干及支链、结构确定的梳状聚丁二烯。其平均支链数可在较大范围内改变。     

Mechanical and Rheological Behavior of Unvulcanized and Dynamically Vulcanized i-PP/EPDM Blends

The mechanical and rheological behavior of dynamically vulcanized PP/EPDM blends is examined and compared with those of unvulcanized blends. The effect of blend ratio and dynamic vulcanization of EPDM rubber on tensile properties and flow are investigated. The mechanical properties of the blends are strongly influenced by the blend ratio. With the increasing of EPDM content the value of yield stress in a solid state decreases with the elastomer volume fractions less than 0.45 for the unvulcanized blends. For the dynamically vulcanized blends the interval of EPDM content, at which the yield peak is seen, is rather limited below 0.25 elastomer volume fractions. It is shown that dynamic vulcanization changes the deformational behavior of PP/EPDM blends. The rheological properties of dynamically vulcanized blends depending on the ratio of the components may be similar to the properties of polymer composites containing the highly disperse structuring filler. The distinction between the rheological behavior of unvulcanized and dynamically vulcanized blends is related to differences of their structures and viscoelastic characteristics of unvulcanized and vulcanized EPDM phase.     

A model study on effect of glucose on the basic characteristics and physical properties of natural rubber

Glucose at various concentrations was incorporated into sugar free purified natural rubber (PNR) latex to model the effect of carbohydrate on the basic characteristics and physical properties of natural rubber (NR). PNR samples treated with various concentrations of glucose were characterized for the basic properties of unvulcanized NR, i.e., gel content, molecular weight distribution and Mooney viscosity to evaluate the effect of sugar on these parameters. In addition, the effect of glucose on the physical properties of vulcanizates derived using sulfur and peroxide vulcanization was investigated. Glucose was shown to affect the viscosity of unvulcanized NR and the discoloration of vulcanized NR. Moreover, glucose was found to have a strong effect on crosslink density, as well as tensile and dynamic properties of sulfur vulcanizates, while those properties of peroxide vulcanizates was not much affected by glucose.     

Cis-trans isomerization of polybutadiene double bonds during olefin metathesis

The cis-trans isomerization of polybutadiene double bonds during metathesis degradation using WCl₆/(CH₃)₄Sn catalyst system has been estimated kinetically along with productive metathesis. The isomerization was followed both for noncrosslinked and for crosslinked polybutadiene. Ninety-six percent cis-1, 4 units are found to isomerize into ca. 75% trans-1, 4 units. The rate of stereomutation is found to be different in the presence and absence of a low-molecular-weight olefin. The results are explained with the help of a stereo model originally proposed by Katz (Advances in Organometallic Chemistry, Academic, New York, 1977, Vol. 16.)