顺-1,4-聚丁二烯的本体结晶和溶液结晶

以稀土催化剂聚合得到的聚丁二烯(Ln-PB)的顺式含量接近99%,支化度小,分子具有较高的规整性。本工作用电镜,线膨胀仪、体膨胀仪、DSC、GPC、X-光衍射等实验方法在较宽的分子量范围和结晶温度范围下对Ln-PB的本体结晶和溶液结晶行为进行了研究。     

SSBR/TPI共混体系中TPI的结晶、成核及动力学研究

研究了不相容共混体系溶聚丁苯橡胶(SSBR)/反式-1,4-聚异戊二烯(TPI)共混体系的结晶行为.当SSBR含量较低时,SSBR/TPI共混物的成核密度降低,晶体生长速率降低,等温结晶速率降低,非等温结晶峰移向低温,SSBR抑制了α-TPI的生成,SSBR/TPI共混体系总结晶度降低,但TPI的相对结晶度升高,结晶行为与热力学相容的结晶/非晶共混体系一致;当SSBR含量较高时,随着SSBR含量增加,体系的成核密度增加,球晶的生长速率显著降低,SSBR显著抑制了α-TPI的生成,共混体系以β晶为主.     

稀土聚丁二烯的结晶行为与分子量及温度的关系

本工作研究了稀土催化聚合的聚丁二烯(Ln-PB)的结晶速率与分子量的关系。结果表明Ln-PB的结晶速率在_η=5.6×10⁵左右有一极小值,而在_η=3.4×10⁶左右有—极大值。 从实验中还发现,Ln-PB的结晶在-20℃左右,由单二维核生长逐渐转变为多二维核生长。 本作工根据结晶成核理论,计算了不同分子量Ln-PB结晶折叠面的比表面能,σ_e表明当 η<10⁶时,σ₃随分子量的变化很小;当_η>10⁶时,σ_e随分子量的增加明显增大。     

X-射线衍射法研究稀土顺-1,4-聚丁二烯低温结晶动力学

本文用广角X-射线衍射法(WAXD)研究了稀土催化聚合顺-1,4-聚丁二烯(Ln-PB)低温下分子量和温度对结晶过程的影响.随着分子量的改变,结晶速度在M_η=8×10~5左右有一极小值;在M_η=29×10~5左右有一极大值.最大结晶速度发生在T_(c,max)=-60～-70℃之间.最大平衡结晶度值,在M_η大于10~6以上与分子量无关,而最大平衡结晶度值所对应的温度与M_η呈线性关系.随着温度上升,晶胞参数略有增大.Ln-PB主级结晶属于非均相成核,以原纤状和盘状混合生长.     

稀土顺-1,4-聚丁二烯的搅拌溶液结晶

本工作研究了稀土顺-1,4-聚丁二烯(Ln-PB)的搅拌溶液结晶行为,发现当结晶温度为-15—-79℃、搅拌速度为180转/分时,经过一段时间,就有乳白色的丝状物缠绕在搅拌棒上.在电镜下可以看到,这些丝状物是由平行排列的纤维晶组成的.沉积在搅拌棒上的Ln-PB的量随结晶温度的下降而增加,大约在-65℃左右达到极大值.而后又随结晶温度的下降而减少.结晶温度愈高、沉积在搅拌棒上的Ln-PB的平均分子量愈高,分布愈窄,所以可利用搅拌溶液结晶的方法对Ln-PB进行分级.     

反式-/顺式-1,4-聚异戊二烯共混体系的结晶动力学

采用差示扫描量热(DSC)法对反式-/顺式-1,4-聚异戊二烯共混体系的等温及非等温结晶动力学进行了研究,分别采用Avrami方程和莫志深法对其动力学参数进行了解析.研究结果表明,在反式-/顺式-1,4-聚异戊二烯共混体系的等温及非等温结晶过程中,顺式-1,4-聚异戊二烯(CPI)组分的存在会降低反式-1,4-聚异戊二烯(TPI)组分的结晶速率;在等温结晶过程中,CPI组分会提高TPI组分自身的结晶度;而非等温结晶过程中,CPI则提高了共混物中β晶型的相对含量.     

稀土顺-1,4-聚丁二烯的分子量及分子缠结对结晶行为的影响

本工作以线膨胀、体膨胀、DSC、扭辫等方法,在较宽的分子量和结晶温度范围内研究了稀土顺-1,4-聚丁二烯(Ln-PB)的分子量与结晶速率,结晶熔点,玻璃化温度及结晶比表面能之间的关系。进一步考察了分子链缠结对结晶速率的影响,并在结晶成核理论的基础上引入链缠结的影响,导出Ln-PB的结晶动力学方程,得到了与实验符合较好的结果。     

稀土顺1,4聚丁二烯的分子缠结与结晶

本文用电镜研究了经过分级得到的不同分子量及不同分子量分布的稀土顺1,4 聚丁二烯(Ln-PB)及镍顺1,4 聚丁二烯(Ni-PB)的低温结晶形态、结晶成核及生长机理。发现低分子量 PB以预现成核为主,而高分子量PB以大分子的缠结为中心的散现成核为主,得到两种不同片层缠结形态的PB球晶。其结晶形态及速率主要受高分子量中的大分子缠结影响。     

稀土丁二烯-异戊二烯无规共聚物低温转变的研究

本文研究了稀土丁二烯-异戊二烯无规共聚物的低温转变性能。实验证明,这类聚合物的玻璃化转变温度、结晶速率和最大主级结晶值都随共聚比的变化而变化,当丁/异戊重量组成比为84/16时,系不完全结晶橡胶。从丁二烯-异成戊二烯共聚物(不同共聚比)的最大结晶速率温度(Tc_max)用外推法可求得稀土顺丁橡胶的最大结晶速率温度为-72℃,这在文献上尚未见报导。稀土顺丁橡胶的玻璃化温度(T_g)为-113℃,其Tc_max(°K)/T_g(°K)=0.796,而天然橡胶的Tc_max(°K)/T_g(°K)=0.814,两者具有与0.80相近的值。     

聚丁二烯/二氧化硅杂化新材料等温结晶动力学及结晶形态的研究

研究了所合成的新型高顺式聚丁二烯键合纳米二氧化硅杂化材料(PB-Si)的顺式-1,4微观结构、特性黏数([η])、微观形态及热稳定性与键合纳米二氧化硅含量的关系等,并采用示差扫描量热仪(DSC)和配有在线冷热台的偏光显微镜(POM)研究了杂化材料PB-Si中SiO_2含量及微观链结构特点对其低温下等温结晶动力学及结晶形态、球晶增长速率的影响.结果表明:当SiO_2含量小于2.5%时,杂化材料PB-Si的特性黏数和顺式-1,4结构含量均基本保持不变,短支链结构的杂化材料(PB-Si-Ni)的顺式-1,4结构含量约为96.6%,高度线性链结构的杂化材料(PB-Si-Nd)的顺式-1,4结构含量约为98.6%,热稳定性均随着SiO_2含量增加而有所提高;在PB顺式-1,4微观结构及SiO_2结合含量基本相同的前提下,与共混物PB/SiO_2相比,杂化材料PB-Si具有更快的结晶速率,且随着杂化材料PB-Si中SiO_2结合量增大,其结晶速率加快,半结晶时间(t1/2)缩短;若杂化材料中顺式-1,4微观结构含量和SiO_2结合量同时增加,杂化材料PB-Si的结晶速率进一步加快;在顺式结构含量及SiO_2含量确定的情况下,聚合物的拓扑结构对其结晶速率也有明显影响,高度线性结构(PB-Si-Nd)比短支链结构(PB-Si-Ni)的杂化材料也具有更快的结晶速率;杂化材料PB-Si在低温等温结晶过程中均呈现三维球晶的生长方式,Avrami指数(n)在2.0~3.0之间,球晶增长速率也随SiO_2结合量增加而加快.     

稀土催化丁二烯-异戊二烯共聚物的动态力学性能

有关丁二烯-异戊二烯共聚物的动态力学性能的研究报导不多。Labach及谢德民报导了共聚物序列分布的研究。文献(3)报导了稀土丁/异戊共聚物的低温特性。     

PROPERTIES OF SILK FIBROIN/POLY(ETHYLENE GLYCOL)400 BLEND FILMS

The blend film of silk fibroin (SF) and poly(ethylene glycol)400 (PEG400) with a blend ratio of 2/1 (wt/wt) wasprepared simply by dropping a little PEG400 into the SF solution and then casting the mixed aqueous solution at 50℃. Theresulting film exhibited much better mechanical properties in the dry and wet state than SF itself, owing to theconformational change of SF in the blends from the random coil to the β-sheet structure and intermolecular hydrogen bondformation between SF and PEG400. Thermogravimetric analysis showed that the initial thermal decomposition temperatureof the blend film was 170℃, which was 80℃ lower than that of SF (250℃) and 20℃ higher than that of PEG400 (150℃),and indicated a Strong interaction between two components of the blend. No crystalline peaks were observed in the X-raydiffraction curve of the blend film. Cell culture test showed that SF/PEG400 was a suitable substrate for the growth of humanumbilical vein endothelial cells (HUVEC).     

超高分子量聚苯乙烯的合成和聚合反应动力学

杯芳烃钕与Mg(n Bu) 2 、HMPA所组成的三元络合催化剂用于苯乙烯配位聚合能以高收率制得超高分子量聚苯乙烯 .以甲苯为溶剂 ,在一定条件下制成三元配位催化剂 ,当 [Nd]=8× 10 - 4mol L ,[St]=4 .0mol L ,Mg Nd =2 0 .0 (摩尔比 ) ,HMPA Mg =1.0 (摩尔比 ) ,5 0℃聚合 4 5min ,聚合转化率可达到 80 %左右 .所得聚苯乙烯的重均分子量高达 2 10× 10 4 ,分子量分布指数为 1.6 1.间规聚苯乙烯含量为 81% .动力学研究表明 ,聚合反应速率与单体和主催化剂 杯 [6 ]芳烃钕的浓度分别呈 1次方关系 ,聚合反应的表观活化能为 4 1.7kJ mol     

Effects of sulfone/ketone in poly(phthalazinone ether sulfone ketone) on the gas permeation of their derived carbon membranes

A series of copolymer, poly(phthalazinone ether sulfone ketone)s (PPESKs) with the sulfone over ketone unit (S/K) ratio varying from 20/80, 50/50 to 80/20, were used as precursors to prepare carbon membranes. The effects of chemical structure as S/K ratio of PPESKs on the microstructure and gas separation performance of their derived carbon membranes were mainly investigated. The properties of PPESKs were detected in terms of density, fractional free volume, char yield, interlayer distance and glass transition temperature. During the formation process of carbon membranes (i.e., stabilization and pyrolysis), the changes in functional groups, microstructural parameters and gas permeation were monitored by FTIR, X-ray diffraction, TEM and single gas permeation techniques. The results have shown that the microstructure and gas permeation of obtained carbon membranes are significantly affected by the S/K ratio in precursor PPESKs. Carbon membranes exhibit higher selectivity and lower permeability when prepared at low pyrolytic temperature (i.e., 650 °C and 800 °C) and from PPESKs with S/K ratio equaling 50/50, followed with 20/80 and 80/20. As for carbon membranes prepared at high pyrolytic temperature (i.e., 950 °C), the selectivity order of them is well in accordance with S/K mole ratio in precursor PPESKs: 20/80 > 50/50 > 80/20, and vice versa for permeability.     

Compounding,mechanical and morphological properties of carbon-black-filled natural rubber/recycled ethylene-propylene-diene-monomer (NR/R-EPDM) blends

Blends of natural rubber/virgin ethylene-propylene-diene-monomer (NR/EPDM) and natural rubber/recycled ethylene-propylene-diene-monomer (NR/R-EPDM) were prepared. A fixed amount of carbon black (30 phr) was also incorporated. The effect of the blend ratio (90/10, 80/20, 70/30, 60/40 and 50/50 (phr/phr)) on the compounding, mechanical and morphological properties of carbon-black-filled NR/EPDM and NR/R-EPDM blends was studied. The results indicated that both the carbon-black-filled NR/EPDM and NR/R-EPDM blends exhibited a decrease in tensile strength and elongation at break for increasing weight ratio of EPDM or R-EPDM. The maximum torque (S′M_H), minimum torque (S′M_L), torque difference (S′M_H?M_L), scorch time (ts₂) and cure time (tc₉₀) of carbon-black-filled NR/EPDM or NR/R-EPDM blends increased with increasing weight ratio of virgin EPDM or R-EPDM in the blend. SEM micrographs proved that, for low weight ratios of virgin EPDM or R-EPDM, the blends exhibited high surface roughness and matrix tearing lines. The blends also showed a reduction in crack path with increasing virgin EPDM or R-EPDM content over 30 phr. This reduction in crack path could lead to less resistance to crack propagation and, therefore, low tensile strength.     

用一稀土催化剂合成高分子量聚苯乙烯

由Nd(oct)3(Nd)、Al(i-Bu)3(Al)和C4H9Cl(BCL)三组分组成稀土催化体系,催化苯乙烯(St)在环己烷溶剂中进行配位聚合,考察Al/Nd摩尔比、BCL/Nd摩尔比、陈化温度、陈化时间、催化剂用量、聚合温度与时间等因素对苯乙烯聚合、催化活性以及聚苯乙烯产物(PS)分子量与分子量分布的影响.当Al/Nd=8-12(摩尔比),BCL/Nd=5-25(摩尔比),Ta=40-50℃,ta=6-20 h,Tp=40-50℃时,可以得到高分子量聚苯乙烯,其中重均分子量可高达7.6×105.聚合产物中不溶于丁酮的聚苯乙烯的熔点高达268℃,主要含有间规结构聚苯乙烯和少量等规结构聚苯乙烯;偏光显微镜观察结果表明,可溶于丁酮的聚苯乙烯也是含有部分立构规整链段的聚合物.     

TIME-DEPENDENT MORPHOLOGY OF POLYETHYLENE-POLYPROPYLENE BLENDS

The effect of time-temperature treatment on morphology of polyethylene-polypropylene (PE-PP) blends wasstudied to establish a relationship between thermal history, morphology and mechanical properties. Polypropylene (PP)homopolymers were used to blend with various polyethylenes (PE), including high density polyethylene (HDPE), lowdensity polyethylene (LDPE), linear low density polyethylene (LLDPE), and very and ultra low density polyethylene(VLDPE and ULDPE). The majority of the blends were prepared at a ratio of PE:PP = 80:20, while blends of PP and LLDPEwere prepared at various compositions. Thermal treatment was carried out at temperatures between the crystallizationtemperatures of PP and PEs to allow PP to crystallize first from the blends. On cooling further, PE crystallized too. A verydiffuse PP spherulite morphology in the PE matrix was formed in some partially miscible blends when PP was less than 20%by mass. Droplet-matrix structures were developed in other blends with either PP or PE as dispersed domains in a continuousmatrix, depending on the composition ratio. The scanning electron microscopy (SEM) images displayed a fibrillar structureof PP spherulite in the LLDPE-PP (80:20) and large droplets of PP in the HDPE-PP (80:20) blend, providing larger surfacearea and better bonding in the LLDPE-PP (80:20) blends. This explains why the blends with diffuse spherulite morphologyshowed greater improvement in tensile properties than droplet-matrix morphology blends after time-temperature treatment.     

SYNERGISTIC MODIFICATION OF EPDM AND CROSSLINKING AGENT IN IMMISCIBLE BLENDS OF POLYVINYL CHLORIDE WITH LOW DENSITY POLYETHYLENE

The synergism of ethylene-propylene-diene monomer copolymer （EPDM） and dicumyl peroxide （DCP, a crosslinking agent） in low density polyethylene （LDPE）/poly（vinyl chloride） （PVC） blends was investigated. When EDPM and DCP are added to the blends simultaneously, the tensile properties could be improved significantly, especially for the blends with LDPE matrix. For example, incorporation of 10/1 （mass ratio） EPDM/DCP improves the tensile strength of the LDPE/PVC （mass ratio 80/20） blend from 7.9 MPa to 8.5 MPa and the elongation at break from 25% to 503%. Results from selective extraction, phase-contrast microscopy and thermal analysis reveal that the improvement in the tensile properties of the blends with LDPE matrix is principally due to the formation of a fine crosslinking network of the LDPE and EPDM phase. The outstanding modification effect of EPDM is explained by its dual functions： molecular entanglement with LDPE and the enhanced efficiency of DCP in the blends.     

Blends of polycarbonate and ethylene-1-octylene copolymer

The mechanical properties and morphology of polycarbonate/ethylene-1-octylene copolymer (PC/POE) binary blends and PC/POE/ionomer ternary blends were investigated. The tensile strength and elongation at break of the PC/POE blends decreased with increasing the POE content. The impact strength of the PC/POE blends showed less dependence on thickness than that of PC. And the low-temperature impact strength of PC was modified effectively by addition of POE. The morphology of the PC/POE blends was observed by scanning electron microscope. The PC/POE weight ratio had a great effect on the morphology of the PC/POE blends. For the PC/POE (80/20)/ionomer ternary blends, low content (0.25 and 0.5 phr) of ionomer could increase the tensile properties of PC/POE (80/20) blend and had little effect on the impact strength. And 0.5 phr ionomer made the dispersed domain distribute more uniformly and finely than the blend without it. But with high content of ionomer, the degradation of PC made the mechanical properties of the blends deteriorate. Blending PC and ionomer proved the degradation of PC, and the molecular weight decreased with increasing the ionomer content.     

Miscibility, mechanical and thermal properties of poly(lactic acid)/polyester-diol blends

We found new plasticizers with high molecular weight and low mobility for poly(lactic acid) (PLA). The new plasticizers are polyester-diols (PED) with nominal molecular weight 2000. Temperature dependence of oscillatory tensile moduli of PLA/PED blends in solid states was measured and miscible pairs of the blends were found. The miscible pairs are PLA/poly(ethylene adipate) and PLA/poly(diethylene adipate). Observation by scanning electron microscope and results of differential scanning calorimetry also indicate that these blends are miscible with PLA at weight ratio of PED less than or equal to 20%. In these blends, glass transition temperature is significantly lower than that of PLA. On the other hand, poly(butylene adipate) and poly(hexamethylene adipate) are partially miscible with PLA at weight ratio of PED 20%. The difference of the miscibility is discussed in terms of solubility parameter, which is calculated using the method by Small and configurational entropy.