Blends of Polypropylene and Syndiotactic 1,2-Polybutadiene: Morphology, Crystallization Behaviors and Mechanical Properties

Morphologies, crystallization behavior and mechanical properties of polypropylene(PP)/syndiotactic 1,2-polybutadiene(s-1,2 PB) blends were investigated. Morphology observation shows the well dispersed domains of s-1,2 PB in PP matrix with the rather small domain sizes from 0.1 to 0.5 mu m when the s-1,2 PB content increases from 5% to 20% (mass fraction) in the blends, and the phase structure tends to become co-continuous as s-1,2 PB content further increases.

Crystallization and phase behavior of crystalline syndiotactic 1,2-polybutadiene/isotactic polypropylene blends in solution-cast thin films

Crystallization and phase behavior in solution-cast thin films of crystalline syndiotactic 1,2-polybutadiene (s-1,2-PB) and isotactic polypropylene (i-PP) blends have been investigated by transmission electron microscopy (TEM), atomic force microscopy (AFM) and field-emission scanning electron microscopy (FESEM) techniques. Thin films of pure s-1,2-PB consist of parallel lamellae with the c-axis perpendicular to the film plane and the lateral scale in micrometer size, while those of i-PP are composed of cross-hatched and single-crystal-like lamellae. For the blends, TEM and AFM observations show that with addition of i-PP, the s-1,2-PB long lamellae become bended and i-PP itself tends to form dispersed convex regions oil a continuous s-1,2-PB phase even when i-PP is the predominant component, which indicates a strong phase separation between the two polymers during film formation. FESEM micrographs of both lower and upper surfaces of the films reveal that the s-1,2-PB lamellae pass through i-PPconvex regions from the bottom, i.e. the dispersed i-PP regions lie on the continuous s-1,2-PB phase. The structural development is attributed to an interplay of crystallization and phase separation of the blends in the film forming process.

1,2-聚丁二烯力学性能的研究

钼体系1,2-PB橡胶屈服强度随1,2-链节含量增加而上升,过屈服后,伸长率相同,1,2-链节含量高的其强度大([η]相近的橡胶)。1,2-链节含量与T’_(11)转变温度呈线性关系,方程为:T’_(11)=1.804W—67(W为1,2-含量),当W趋于零时,T’_(11)=67℃,即为顺丁橡胶的T’_(11)转变温度。1,2-PB的T_g受其1,2-链节含量和间同立构含量的影响,当1,2-链节含量相近时,间同含量高,T_g亦高。在DSC和扭辫动态力学图谱上,存在两个结晶峰。

1,2-聚丁二烯及其硅氢加成物的热性能

对1,2-链节含量分别为89.5％(mol)和30％～53％及顺式-1,4含量98％的聚丁二烯(PB)及其三烷基硅氢加成物的热分析研究表明,侧链乙烯基(外双键)热氧化温度与活化能高于主链双健(内双键),热交联温度则与此相反;PB经硅氢加成后,热氧化温度及热交联温度均随加成率的增加而明显提高。加成产物热分解后有较多残重,并与双键加成率有关。加成产物的流动温度T_(?)有较大提高。PB及其硅氢加成产物经完全氢化后,高1,4-链节PB及其硅氢加成产物室温为结晶状态,而高1,2-链节PB及其硅氢加成物则是非晶态的。

塑炼1,2-聚丁二烯的无扰尺寸

利用测得(?)和[η]数据,由Stockmayer-Fixman-Burchard、Stockmayer-Kurata-Roig和Inagaki-Suzuki-Kurata方程外推,估算了塑炼过程中不同1,2-链节含量的1,2-聚丁二烯(1,2-PB)的无扰尺寸变化规律。1,2-链节含量分别为40％和87.2％时,随薄通次数的增加,无扰尺寸降低;但前者薄通50次后变化很小,后者薄通100次后仍有波动。1,2-链节含量为87.2％的1,2-PB,薄通后放置30d,其无扰尺寸随薄通次数的增加而降低的程度,均大于当日测定的结果。

塑炼过程对1,2-聚丁二烯分子量的影响

采用GPC法与[η]测定相结合的方法,研究了1,2-PB在薄通过程中分子量和分子量分布的变化。结果表明,同一类型的1,2-PB,当[η]>200mL/g时,随薄通次数的增加[η]下降,分子量分布向低分子量方向移动。[η]降到200mL/g左右时,尽管成倍增加薄通次数,[η]降低缓慢,並趋于稳定,[η]≈200mL/g时,在薄通过程中[η]变化极小。比较当日和放置30d后测定的薄通样品,结果表明,薄通样品在放置过程中会产生自由基结合,生成支链结构,致使流体力学体积降低。

高1,2-聚丁二烯及通用橡胶的流变性质

采用多速粘度计和Monsanto试验机联用,在表观剪切速率为3×10~(-8)—2.5×10~8s~(-1)时观察了高1,2-聚丁二烯(PB)生胶与顺式1,4-PB,EPDM,SBR 1500在流变性质上的差异。高1,2-PB虽在中等剪切速率下有较高的粘度,但在低、高剪切速率时的粘度均较低,这一特性有利于它的加工。高1,2-PB在低剪切速率下的流动活化能较其他橡胶高,故抗冷流性能优越,易于存放。

不饱和聚合物的辐射效应Ⅱ.EGDMA对无规1,2-聚丁二烯辐射效应的影响

本文研究了双甲基丙烯酸乙二醇酯(EGDMA)对无规1,2-聚丁二烯(1,2-PB)辐射效应的影响。通过辐照1,2-PB和不同EGDMA/1,2-PB比率体系的溶胶分数测定,红外光谱分析及~1H-NMR测试结果,讨论了EGDMA对1,2-PB辐射化学反应(分子间交联及分子内环化)的作用及机理。结果证明,1,2-PB辐射引起的链式交联反应不因EGDMA的存在而改变(无规链反应),但EGDMA的存在将增加1,2-PB的交联引发G(I)值和交联G(c.1)同时导致G(-V)和G(cy)值的减小,抑制或减少,内环化过程。

1,2-聚丁二烯生胶热氧老化性能的研究

本工作用扭辫法、红外光谱法及热分析法等研究了 1,2-聚丁二烯(1,2-PB)生胶的热氧老化性能及其机理。1,2-PB生胶的热氧老化可能是由于乙烯基双键打开进行碳-碳交联和醚式氧桥交联所致。1,2-链节间同立构含量的升高,导致聚合物热氧稳定性变差。1,2-PB生胶的热氧稳定性优于顺丁、丁苯和天然橡胶。防老剂 2246用量为1.0％时,对1,2-PB生胶有较好的稳定作用。

聚丙烯/-1,2-聚丁二烯共混物的形态结构及性能

本文研究了乙烯基含量不同与分子量不同的1,,2-聚丁二烯(1,2-PB)与基聚丙烯(PP)共混物的形态结构和性能。结果表明,1,2-PB 与 PP 具有一定的相容性,相容程度与乙烯含基量有关。1,2-PB 的加入,使 PP 相邻球晶产生片层相互交叉的界面结构,又使 PP 有β型结晶生产。1.2-PB 的最隹增韧效果可与乙丙橡胶相比拟。

溶液介质条件对Fe^3＋共沉淀去除Cu^2＋的影响

采用室内试验方法，研究了溶液介质条件对Fe^3+共沉淀去除Cu^2+的影响。试验结果表明，pH是影响Fe^3+共沉淀去除Cu^2+的主要因素之一，其去除率随pH的增加而增加，并且其固液分配系数Kd的对数值与pH之间显示出较好的线性关系；天然水体中溶解的电解质离子及无机和有机配位体对Cu^2+的去除均产生很大影响，Cu^2+的去除率随加入的NaCl和NaClO4浓度的增加而降低，而随Ca(NO3)2和Mg(NO3)2浓度的增加而增加，除磷酸盐的增强作用外，硫酸钠、碳酸氢钠、甘氨酸、草酸钠、柠檬酸钠以及十二烷基苯磺酸钠的加入则不同程度地减弱了Cu^2+的去除；与Cu^2+共存的等量竞争阳离子Pb^2+、Zn^2+和Cd^2+也同样减弱了Fe^3+对Cu^2+的去除。

Preparation of a clay-modified carbon paste electrode based on 2-thiazoline-2-thiol-hexadecylammonium sorption for the sensitive determination of mercury

A montmorillonite from Wyoming-USA was used to prepare an organo-clay complex, named 2-thiazoline-2-thiol-hexadecyltrimethylammonium-clay (TZT-HDTA-clay), for the purpose of the selective adsorption of the heavy metals ions and possible use as a chemically modified carbon paste electrode (CMCPE). Adsorption isotherms of Hg 2+, Pb 2+, Cd 2+, Cu 2+, and Zn 2+ from aqueous solutions as a function of the pH were studied at 298 K. Conditions for quantitative retention and elution were established for each metal by batch and column methods. The organo-clay complex was very selective to Hg(II) in aqueous solution in which other metals and ions were also present. The accumulation voltammetry of Hg(II) was studied at a carbon paste electrode chemically modified with this material. The mercury response was evaluated with respect to the pH, electrode composition, preconcentration time, mercury concentration, cleaning solution, possible interferences and other variables. A carbon paste electrode modified by TZT-HDTA-clay showed two peaks: one cathodic peak at about 0.0 V and an anodic peak at 0.25 V, scanning the potential from -0.2 to 0.8 V (0.05 M KNO 3 vs. Ag/AgCl). The anodic peak at 0.25 V presents excellent selectivity for Hg(II) ions in the presence of foreign ions. The detection limit was estimated as 0.1 μg L -1. The precision of determination was satisfactory for the respective concentration level. 2005 © The Japan Society for Analytical Chemistry.

49 ground-penetrating radar lines of Area 2 - Gravel cuspate spit with gravel beach ridges from Potter Cove, King George Island, Antarctic Peninsula

During two field campaigns (Austral springs 2011 and 2012) the sedimentary architecture of a polar gravel-beach system at the southwestern coast of Potter Peninsula (Area 2) was revealed using ground-penetrating radar (GPR, Geophysical Survey Systems, Inc. SIR-3000). 49 profiles were collected using a mono-static 200 MHz antenna operated in common offset mode. Trace increment was set to 0.05 m. A differential global-positioning system (dGPS, Leica GS09) was used to obtain topographical information along the GPR lines. GPR data are provided in RADAN-Format, dGPS coordinates are provided in ascii format; projection is UTM (WGS 84, zone 21S).

Synergy between histone deacetylase inhibitors and DNA- damaging agents is mediated by histone deacetylase 2 in colorectal cancer

Previous studies have associated the overexpression of histone deacetylase 2 (HDAC2) and the presence of TP53 mutations with the progression to advanced stage drug resistant colorectal cancer (CRC). However, the mechanistic link between HDAC2 expression and the TP53 mutational status has remained unexplored. Here, we investigated the function of HDAC2 in drug resistance by assessing the synergistic effects of DNA-targeted chemotherapeutic agents and HDAC inhibitors (HDACis) on two TP53-mutated colorectal adenocarcinoma CRC cell lines (SW480 and HT-29) and on the TP53-wild type carcinoma cell line (HCT116 p53+/+) and its TP53 deficient sub-line (HCT116 p53-/-). We showed that in the untreated SW480 and HT-29 cells the steady-state level of HDAC2 was low compared to a TP53-wild type carcinoma cell line (HCT116 p53+/+). Increased expression of HDAC2 correlated with drug resistance, and depletion by shRNA sensitised the multi-drug resistance cell line HT-29 to CRC chemotherapeutic drugs such as 5-fluorouracil (5-FU) and oxaliplatin (Oxa). Combined treatment with the HDACi suberoylanilide hydroxamic acid plus 5-FU or Oxa reduced the level of HDAC2 expression, modified chromatin structure and induced mitotic cell death in HT-29 cells. Non-invasive bioluminescence imaging revealed significant reductions in xenograft tumour growth with HDAC2 expression level reduced to <50% in treated animals. Elevated levels of histone acetylation on residues H3K9, H4K12 and H4K16 were also found to be associated with resistance to VPA/Dox or SAHA/Dox treatment. Our results suggest that HDAC2 expression rather than the p53 mutation status influences the outcome of combined treatment with a HDACi and DNA-damaging agents in CRC.

A continuum model of the growth of engineered epidermal skin substitutes

We present a porous medium model of the growth and deterioration of the viable sublayers of an epidermal skin substitute. It consists of five species: cells, intracellular and extracellular calcium, tight junctions, and a hypothesised signal chemical emanating from the stratum corneum. The model is solved numerically in Matlab using a finite difference scheme. Steady state calcium distributions are predicted that agree well with the experimental data. Our model also demonstrates epidermal skin substitute deterioration if the calcium diffusion coefficient is reduced compared to reported values in the literature.