含Si原子乙烯基单体的聚合及其膜的制备与研究

近年来,含硅聚合物由于其特殊的化学性质而成为科研热点.文章进行了烯丙氧基三甲基硅烷的均聚以及其分别与甲基丙烯酰氧乙氧基三甲基硅烷和乙酸乙烯酯单体的共聚研究.用凝胶渗透色谱仪测试了共聚物的分子量并计算其聚合度,并将所得聚合物做成气体分离膜,采用膜分离测试分析仪测试它们的气体透过性能.结果表明：烯丙氧基三甲基硅烷与乙酸乙烯酯共聚物膜对CO2具有优先选择透过性,在CH4/CO2的气体透过性测试中分离率达到了3.1,在N2/CO2的气体透过性测试中分离率更是达到了11.5.     

紫外接枝丙烯酸对PVDF膜表面改性的研究

以二苯甲酮为光引发剂,通过紫外辐照将亲水性单体丙烯酸接枝于聚偏氟乙烯(PVDF)膜的表面。考察了光引发剂浓度和辐照时间对接枝率的影响,并利用衰减全反射光谱和扫描电子显微镜对接枝后PVDF膜表面的化学组成和微观形貌进行了表征。结果表明:随着光引发剂浓度的增大,丙烯酸的接枝率先增大后减小。通过纯水接触角和吸水率研究了接枝后的PVDF膜的亲水性,发现接枝后的PVDF膜的亲水性得到明显改善。     

Modification of Natural Leather by Grafting Emulsion Copolymerization Technique

Grafting emulsion copolymerization of methyl methacrylate (MMA) with butyl acrylate (BuA) of different molar ratios onto natural leather was carried out using redox initiation system of potassium persulfate (PPS) developed as an oxidizing agent and some sodium bisulphite adducts as reducing agents. Sodium dodecyl sulphate (SDS) was used as an anionic emulsifier.

The grafted leather was characterized via FTIR, SEM and thermal gravimetric analysis. Moreover, the grafted leather was evaluated through water absorption, tensile strength, dyeing performance and hardness measurements. The obtained results revealed that the physical and mechanical properties of the modified leather were enhanced.     

Influences of Ternary Graft Copolymers on the Morphology and Properties of Polypropylene/Calcium Carbonate Composites

The ternary graft copolymers were synthesized by solid-phase grafting maleic anhydride (MAH), methyl methacrylate (MMA), and butyl acrylate (BA) onto polypropylene (PP), and applied in the interfacial modification of the PP/Calcium carbonate (CaCO₃) composites. Fourier transform infrared (FTIR) spectroscopy was used to analyze the structure of the ternary graft copolymers. Scanning electron microscopy (SEM), thermogravimetry (TG), differential scanning calorimetry (DSC), and dynamic rheological testing were used to investigate the morphology and the properties of the composites. FTIR results confirmed the occurrence of the solid-phase graft copolymerization, and SEM exhibited the improvement of the compatibility between PP and CaCO₃ by PPTM. The properties testing showed that PPTM significantly contributed to the reinforcement of the composites in terms of mechanical properties, thermal properties, and rheological properties by acting as interfacial modifiers and plasticizers. The preferable loadings of PPTM for the properties improvement of the PP/CaCO₃ composites were between 7 and 9 phr.     

GRAFT COPOLYMERIZATION OF POLYPROPYLENE COPOLYMER WITH MALEIC ANHYDRIDE: EFFECT OF GRAFTING ON THERMAL,MECHANICAL PROPERTIES,AND PAINTABILITY

Graft copolymerization of polypropylene copolymer (PCP) with maleic anhydride (MA) was studied in melt in Brabender Plasticorder, Twin Screw Extruder by using peroxide initiators, such as benzoyl peroxide (BPO), lauryl peroxide (LPO), luperox-101 (LPU), and dicumyl peroxide (DCP). The variation of MA and initiator concentrations on percent grafting (G), melt flow index (MFI), torque, and gel formation was investigated. Graft copolymers (PgMA and PgMAT) were characterized by FT-IR, DSC, and TGA. Melt flow index increased and torque values decreased with an increase in initiator concentration. The increase in MFI values are in the order: DCP>LUP>BP0>LPO. Maximum chain scission was observed by using DCP and LUP as indicated by their MFI values. The incorporation of MA in PgMA and PgMAT was confirmed by the presence of carbonyl groups at 1712 cm^?1 and a shift in crystallization peak temperature from 113 to 123°C due to nucleating effect of the poly(maleic anhydride). The thermal stability was increased by the presence of PgMA. Addition of PgMAT as an additive to PCP, PCP/PP, and amines improves mechanical properties and paintability. Primary amines are more reactive towards PgMAT compared to tertiary amines.     

环管工艺氢调法生产高熔体流动速率抗冲击共聚PP M30RH

在双环管反应器与气相反应器串联的聚丙烯(PP)装置上,通过非对称给电子体注入技术,利用氢调法并控制气相反应器中乙烯含量以及乙烯气与乙烯和丙烯混合气的摩尔比,使产品中橡胶相含量合理,最终生产出刚性和韧性相对平衡的高熔体流动速率(30.0 g/10 min)、抗冲击共聚PP M30RH。M30RH在-20℃时的缺口冲击强度达3.9 kJ/m2以上,弯曲模量可达1 200 MPa以上,各项性能均达到国内同类产品水平,产品得到用户认可并应用于多个领域。     

AM/NIPAM对P(NIPAM-co-AM)温敏凝胶性能影响

以丙烯酰胺(AM)、N-异丙基丙烯酰胺(NIPAM)为单体,过硫酸铵(APS)-亚硫酸氢钠(SBS)为氧化-还原引发体系,N,N'-亚甲基双丙烯酰胺(BIS)为交联剂,制备了亲水型温敏凝胶P(NIPAM-co-AM)。研究了投料比AM/NIPAM对凝胶性能的影响。结果表明：随着凝胶体系中亲水单体AM比例的增大,共聚凝胶溶胀率、保水率、硬度均提高。当AM从0增大到100%时,凝胶硬度从84.929g增为1255.222g。DSC表明,当AM含量从2%提高到10%时,凝胶LCST从38.61℃增加到57.95℃。随着AM比例降低,凝胶LCST向低温方向移动,相变范围温敏性越好。     

原位聚合法制备吸水膨胀天然橡胶

采用过硫酸铵/硫代硫酸钠氧化还原引发体系,使丙烯酸和氢氧化钠单体在天然胶乳乳液状态下发生原位聚合,同时接枝到天然橡胶分子链上,制备出高吸水倍率的吸水膨胀天然橡胶。通过研究具体条件对单体接枝率和产品吸水倍率的影响,得出制备吸水膨胀天然橡胶(WSNR)的最佳工艺条件为:温度45.0℃,引发剂用量为总固体质量的0.7%,反应时间1.5小时,单体与橡胶的用量比为1.0∶1.0,交联剂用量为2.0×10-4mol。在此条件下,单体最高接枝率和产品最高吸水倍率为49.8%和584.7倍。红外谱图分析表明丙烯酸钠已接枝到天然橡胶的分子链上;热重测试分析表明接枝丙烯酸钠后的天然橡胶的热稳定性提高。     

Pre-irradiation grafting of styrene and maleic anhydride onto PVDF membrane and subsequent sulfonation for application in vanadium redox batteries

A poly(vinylidene difluoride) (PVDF) membrane was grafted with styrene (St) and maleic anhydride (MAn) using an electron-beam-induced pre-irradiation grafting technique. The grafted membrane (PVDF-g-PS-co-PMAn) was then sulfonated and hydrolyzed to give an ion exchange membrane (denoted as PVDF-g-PSSA-co-PMAc) for vanadium redox flow batteries (VRB) use. Micro-FTIR analysis indicated that PVDF was successfully grafted and sulfonated at the above condition, and the membrane with a high grafting yield (GY) can be easily prepared in a St/MAn binary system at low dose due to a synergistic effect. The water uptake and ion exchange capacity (IEC) of the PVDF-g-PSSA-co-PMAc membrane increased with GY, so too did the conductivity. At a GY of 33.6%, the resulting PVDF-g-PSSA-co-PMAc membrane showed a much higher IEC and conductivity than a conventional Nafion117 membrane, and a much lower permeability of vanadium ions: ca. 1/11 to 1/16 of that through Nafion117. Open circuit voltage measurements showed that the VRB assembled with the PVDF-g-PSSA-co-PMAc membrane maintained values above 1.3 V after a period of 33 h, which was much longer than that with the Nafion117 membrane. It is expected that this work provides a new approach for the fabrication of ion exchange membranes for VRB.     

Significantly enhanced charge conduction in electric double layer capacitors using carbon nanotube-grafted activated carbon electrodes

Carbon nanotube (CNT)-grafting by chemical vapor deposition was conducted to reduce the resistance of activated carbon fiber serving as an electrode for electric double layer capacitors. Sputtering deposition of Ni catalyst particles led to a uniform growth of CNTs on the carbon fiber surface through the tip-growth mechanism. Because sputtering deposition ensures little pore blockage (in comparison with wet-impregnation), the surface area decrease of the carbon fiber due to Ni loading was minimized. By using H₂SO₄ aqueous solution as the electrolyte, a capacitor cell assembled with the CNT-grafted fiber showed higher electron and electrolyte-ion conductivities relative to a cell assembled with the bare fiber. By increasing the discharging current density from 1 to 150 mA cm⁻², the bare fiber exhibited a capacitance loss of 17% while the CNT-grafted fiber showed a mitigated capacitance loss of only 7%. This developed CNT-grafting technique renders activated carbon fiber a promising electrode material for a variety of electrochemical applications.