硬沥青对聚丙烯抗光老化性能的改性

利用深度萃取脱油方法制备高软化点硬沥青材料,通过熔融共混的方法对聚丙烯进行添加改性,并通过人工加速紫外光老化试验,对改性后的聚丙烯进行抗老化性能的测试表征,相应的红外谱图以及力学性能的测试结果表明,硬沥青的添加对聚丙烯材料的抗光老化性能有很好的改善作用。     

改性聚丙烯的Ⅰ型疲劳裂纹及断面微观形貌研究

聚丙烯作为一种优良的化工材料,在生活中的应用是十分广泛的,经过不断地研究、探索,人们通过在聚丙烯中添加各种材质,逐渐研制出了多种改性聚丙烯,使得聚丙烯的多种性能得到了加强,扩宽了聚丙烯的应用范围。为了更好地对改性聚丙烯的性能进行了解,本文从改性聚丙烯疲劳裂纹的概述出发,对Ⅰ型疲劳裂纹及断面微观形貌进行了相关实验,并对实验结果进行了讨论,希望可以对改性聚丙烯疲劳损伤性能的研究工作起到一定的帮助作用。     

纳米蛭石改性聚丙烯薄膜的制备及其透氧性能研究

利用熔融插层法制备了纳米蛭石改性聚丙烯复合材料,测试研究了材料的结晶性能、力学性能、阻氧性能、阻湿性能和表面摩擦系数,并进行了分析。实验结果表明:添加了1%(质量分数)蛭石的改性聚丙烯材料中蛭石纳米级分散效果较好,阻氧性能得到了明显提高,与空白膜相比透氧量降低了12.89%。     

回收汽车用废旧塑料制备复合板材的力学性能

以汽车内饰用废弃塑料为主要原料,粉碎后通过添加新的接枝改性聚丙烯短切玻璃纤维制备出复合板材,研究了改性PP和短切玻纤对材料力学性能的影响.结果表明,改性PP的加入有利于改善材料的成形性能.添加新的改性聚丙烯后,复合材料的压缩强度和压缩模量增大,随着改性PP含量的提高,弯曲强度大幅提高而弯曲模量稍有降低;随着短切玻璃纤维含量的提高,材料的弯曲强度及弯曲模量均明显提高.     

三嗪膨胀阻燃母粒的制备及在聚丙烯中的应用

以高熔指聚丙烯(HM-PP)粉料为基体,通过双螺杆挤出机将聚磷酸铵(APP)、三嗪成炭发泡剂(CFA)和纳米二氧化硅(Si O2)与聚丙烯进行捏合,经挤出、冷却及切粒后,制备三嗪膨胀阻燃母粒,同时研究了膨胀阻燃剂与聚丙烯基体的不同质量比对母粒加工性能的影响。将制备的阻燃母粒以一定的添加量与聚丙烯(M02)混合后直接注塑,制备阻燃聚丙烯材料,通过极限氧指数(LOI)和垂直燃烧(UL-94)测试研究了材料的阻燃性能,通过拉伸、弯曲和冲击性能的测试研究了材料的力学性能,通过扫描电镜对材料截面的测试研究了阻燃剂在材料中的分散性及相容性,同时还研究了阻燃PP材料的耐水性能。结果表明,在阻燃剂添加量为65%的时候,阻燃母粒具有很好的加工性能,加工过程中无断条现象。当母粒的添加量为33.8%(阻燃剂含量为22%)时,材料通过UL-94 V-0级,LOI值达到了34.3%,表现出很好的阻燃效果。与单独添加膨胀阻燃剂的阻燃PP材料相比,阻燃母粒与聚丙烯树脂具有更好的相容性且在树脂中分散均匀,阻燃母粒的加入提高了材料的力学性能,同时材料的耐水性能也得到了很好的提高,材料在耐水测试后依然能保持很好的阻燃性能。     

硅灰石、微囊化红磷／天然水镁石复配阻燃聚丙烯的制备与性能

将改性天然水镁石分别与改性硅灰石、微囊化红磷添加到聚丙烯中，制得两种复合材料。对这两种复合材料进行冲击试验、差热分析、氧指数和垂直燃烧性能测试分析，考察了两种复合材料的力学性能和阻燃性能。实验结果表明，天然水镁石微囊化红磷复配阻燃聚丙烯体系较天然水镁石硅灰石复配阻燃聚丙烯体系阻燃性能更好同时力学性能损失较小。     

聚丙烯微孔发泡材料泡孔结构控制的研究进展

聚丙烯微孔发泡材料具有较好的性能和较高的比强度,泡孔结构是影响聚丙烯微孔发泡材料性能的关键因素,其主要由聚丙烯基体性质、共混改性、添加纳米粒子、控制工艺条件等因素控制。从这些影响因素出发,综述了近年来聚丙烯微孔发泡材料泡孔结构控制的研究进展,并展望了其应用前景。     

聚丙烯纤维混凝土性能试验研究

采用普通聚丙烯纤维和辅特维聚丙烯纤维对普通水泥混凝土进行改性,测试其力学性能、耐久性能,并与基准混凝土进行比较,以揭示聚丙烯纤维对水泥混凝土性能的影响规律。试验结果表明：聚丙烯纤维能在一定程度上提高混凝土的力学性能,对混凝土的耐久性能有明显改善作用,并且辅特维聚丙烯纤维对混凝土性能的改性效果要优于普通聚丙烯纤维。     

氧化镧/聚丙烯防X射线复合纤维的制备及性能表征

先采用熔融纺丝方法制备了不同氧化镧含量的氧化镧/聚丙烯复合纤维,然后采用对二甲苯在相同处理时间(1 h)不同温度(105~109℃)下溶解复合纤维中的部分聚丙烯基体以提高纤维中氧化镧含量,并对处理过后的纤维进行扫描电镜、X射线屏蔽性能等测试。此外,采用硅烷偶联剂改性氧化镧,通过熔融纺丝法制备了表面活性氧化镧/聚丙烯复合纤维,并对其作了差示扫描量热分析、扫描电镜、力学测试等性能表征。实验结果表明,随未改性氧化镧添加量增加,纤维力学性能下降,玻璃化转变温度向低温方向移动,纤维热稳定提高;有机改性可改善氧化镧在聚丙烯中的分散,提高纤维的力学性能,纤维玻璃化转变温度较纯聚丙烯纤维升高;用对二甲苯在107℃处理1h所获取的复合纤维中氧化镧含量最高,X射线屏蔽性能最优。     

硅灰石表面改性及其在聚丙烯中的应用

采用硅烷对硅灰石进行了表面改性实验,将活化后的粉体加入聚丙烯材料中,研究了硅烷改性对聚丙烯/硅灰石复合材料性能的影响。通过对改性前后粉体吸油值及红外光谱分析以及对填充聚丙烯材料新鲜断面的扫描电镜分析,研究硅烷改性硅灰石的效果和改性机理。结果表明:硅烷偶联剂适宜用量为硅灰石质量的0.8%~1.2%,改性温度为80℃,时间为15~20 min。表面改性可以显著提高聚丙烯/硅灰石复合材料的拉伸强度、弯曲强度、弯曲模量、热变形温度等性能指标。     

Electrical and morphological studies of polymeric composites based on carbon black

Conventional polymers, polypropylene and polystyrene, containing carbon black as conductor additive, were prepared. Impedance complex-plane analysis is used in order to characterize the composites obtained. Microstructure studies indicate that carbon black affects the size but not the geometrical morphology. The electrical conductivity of polypropylene composites is higher than polystyrene, and is correlated to the microstructural and wettability properties of these polymer matrices.     

Investigation the effect of cellulose on the structure and properties of polypropylene fibres

The modification of polypropylene fibre during their production is usually performed with the aim to improve some end-use properties of final polypropylene textiles. The most common procedure for the modification of polypropylene fibres involves adding additives in the form of masterbaches, which are incorporated into polymer by physical means during fibre formation. The presented work is focused on the investigation the effect of natural organic additive cellulose on the preparation, morphology and the thermal properties of polypropylene fibres. The series of modified pre-oriented and drawn polypropylene fibres with different content of cellulose from 0 wt. % to 3 wt. % were prepared via the classical discontinuous process of melt spinning and drawing. The non-isothermal crystallization and melting behaviour of pre-oriented and drawn polypropylene fibres were analysed by differential scanning calorimetry tests under nitrogen atmosphere. The surface morphology of polypropylene fibres and cross-sectional shapes were examined by scanning electron microscopy. The obtained experimental results were compared with reference polypropylene fibres prepared under the same technological conditions.     

Study of the change in polarity of polypropylene modified in bulk by polar copolymers

The adhesive properties of the blends of isotactic polypropylene with ethylene-acrylic acid copolymers were investigated. It was found that the surface free energy, polar component of surface free energy, polar fraction and mechanical work of adhesion increased with concentration of EAA copolymers in the iPP blends to a degree exceeding additive function. The proportionality of mechanical work of adhesion of the polymer blends to polar fraction that reflects the strength of adhesive joint was also revealed. This observation permits us to claim that the increase in polarity or hydrophilicity of iPP due to modification in bulk by the use of polar EAA copolymer raises the strength of adhesive joints between iPP and more polar polymers. The relationship between mechanical properties of the studied polymer blends and their composition showed the functional additivity of the mechanical parameters.     

Transformation of poly(dimethylsiloxane) into thin surface films of SiO x by UV/ozone treatment. Part II: segregation and modification of doped polymer blends

UV/ozone treatment of organic polymers having silicone additives to produce oxidized layers was achieved by doping a host polymer or prepolymer with a silicone additive, poly(dimethylsiloxane) (PDMS). The concentration of PDMS in the host polymer was low, typically in the range of 0.1–2.0% by weight. Host polymers were polyethylene, polyimide, and polyurethane. After film formation, the presence of PDMS was detected on the surface using X-ray photoelectron spectroscopy (XPS), consistent with wetting angle measurements that revealed a hydrophobic surface. The doped blend was then subjected to exposure in a UV/ozone environment such that a thin, stable barrier of SiO _x was formed at the surface of the film. Rate of film modification was monitored by XPS and measurement of advancing contact angle using deionized water. XPS measurements also showed some evidence of modified fragments of the host polymer near the surface. Significant segregation of PDMS and subsequent transformation to silicon oxides has been demonstrated to occur in these doped systems. The stability of the modified glassy surface formed by UV/ozone treatment of a commercially available epoxy formulation containing a silicone additive was shown to be superior to that obtained by other treatment techniques, e.g., oxygen plasma modification.     

Compatibility and morphology of blends of isotactic and atactic polypropylene

The compatibility and morphology of blends of isotactic and atactic polypropylene have been studied by several means: X-ray scattering, differential scanning calorimetry, and electron microscopy. It was found that the atactic polymer was located mainly inside the spherulites of the isotactic polypropylene on a scale approximately equal to that of the crystalline lamellae. This means that these two polymers were more intimately mixed than are blends of polypropylene and ethylene-propylene copolymer, in which the location of the copolymer is unrelated to the spherulite structure. This difference can be explained by the fact that atactic and isotactic polypropylene are miscible in the melt, whereas polypropylene and ethylene-propylene copolymer are not.     

Evaluation of Thermal and Film Forming Properties of Acrylic Aqueous Polymer Dispersion Blends: Application to the Formulation of Sustained-Release Film Coated Theophylline Pellets

Abstract

Aqueous acrylic polymer dispersions were blended in order to improve processing and film formation from acrylic polymers with poor film forming properties and/or to obtain sustained-release film coated pellets with optimal barrier properties according to the physicochemical and pharmacokinetic requirements of the active substance.

Heterogeneous film structures are generally obtained from blends containing an association of hard acrylic polymers (Eudragit* RS30D, S100) with the soft Eudragit* NE30D when the drying temperature is lower than the minimum film forming temperature (MFT) of the hard acrylic polymers. The Tg and MFT values of the hard acrylic polymers are not modified in the presence of the soft polymer as shown by the thermograms of these blends which are generally characterized by two individual glassy transitions.

On the other hand, a wide range of drug dissolution profiles can be obtained from film coated pellets either by using, in different proportions, the insoluble but readily permeable Eudragit* RL30D in association with the less permeable Eudragit* RS30D in order to obtain pH-independent permeability membrane, or by mixing the anionic methacrylic acid copolymers (L30D, S100) with the neutral NE30D in order to obtain pH-dependent permeability film coated pellets showing higher dissolution release rates at intestinal pH values.     

Evaluation of Thermal and Film Forming Properties of Acrylic Aqueous Polymer Dispersion Blends: Application to the Formulation of Sustained-Release Film Coated Theophylline Pellets

Aqueous acrylic polymer dispersions were blended in order to improve processing and film formation from acrylic polymers with poor film forming properties and/or to obtain sustained-release film coated pellets with optimal barrier properties according to the physicochemical and pharmacokinetic requirements of the active substance.

Heterogeneous film structures are generally obtained from blends containing an association of hard acrylic polymers (Eudragit^* RS30D, S100) with the soft Eudragit^* NE30D when the drying temperature is lower than the minimum film forming temperature (MFT) of the hard acrylic polymers. The Tg and MFT values of the hard acrylic polymers are not modified in the presence of the soft polymer as shown by the thermograms of these blends which are generally characterized by two individual glassy transitions.

On the other hand, a wide range of drug dissolution profiles can be obtained from film coated pellets either by using, in different proportions, the insoluble but readily permeable Eudragit^* RL30D in association with the less permeable Eudragit^* RS30D in order to obtain pH-independent permeability membrane, or by mixing the anionic methacrylic acid copolymers (L30D, S100) with the neutral NE30D in order to obtain pH-dependent permeability film coated pellets showing higher dissolution release rates at intestinal pH values.     

Synthesis of modified guanidine-based polymers and their antimicrobial activities revealed by AFM and CLSM

Modified guanidine-based polymers with chain extension were synthesized by condensation and cross-linking polymerizations in an attempt to increase molecular weight and charge density of the antimicrobial polymers. The antimicrobial activity and the corresponding mechanisms were investigated by several approaches. The results indicated that the antimicrobial activities of the modified guanidine-based polymer, based on the minimum inhibition concentration (MIC) against E.coli, varied with alkyl monomer ratios. UV absorption at 260 nm further quantified the amount of intracellular components leaked into bacteria suspension. The UV absorption measurements were also used to monitor inhibition processes dynamically. It was found that the modified guanidine-based polymer inhibited the growth of bacteria by causing membrane compromised and intracellular leaked. Dual fluorescent dyes were used to stain all bacteria including the dead ones, which enabled us to utilize CLSM to visualize the viability of bacteria in the presence of various modified guanidine-based polymers without causing any damage. The morphologies of bacteria untreated and treated with modified guanidine-based polymer were observed using an atomic force microscope (AFM), which further demonstrated the damage of E.coli membrane and the leakage of intracellular component induced by the modified guanidine-based polymers.     

Capillary electrophoresis of N-acetylneuraminic acid polymers and hyaluronic acid: correlation between migration order reversal and biological functions

High-resolution analysis of polymers of N-acetylneuraminic acid and hyaluronic acid was performed by capillary electrophoresis in a buffer containing a neutral polymer. Both polysaccharides having more than 100 monosaccharide residues were well separated into their molecular species by capillary electrophoresis using a combination of a chemically modified capillary and a buffer containing poly(ethylene glycol) as an additive. During optimization of the separation conditions, small oligomers of both polysaccharides were observed to migrate in the reverse order of their molecular masses on the electropherograms. However, oligomers larger than pentamer and decamer for N-acetylneuraminic acid polymers and hyaluronic acid, respectively, migrated in the order of their molecular masses. We propose that these unusual migration patterns are closely related to the stereochemical structures and the oligomer migrating the fastest is the minimum unit that forms the regular three-dimensional structure required for the biological function.