反应挤出原位阴离子聚合尼龙6/石墨烯复合微球的连续制备与表征EI北大核心CSCD

以己内酰胺(CL)、苯乙烯(St)及氧化石墨烯(GO)为主要原料,首先在熔融的CL中经自由基聚合得到聚苯乙烯(PS)/CL/GO混合熔体,然后在双螺杆挤出机中引发CL阴离子聚合生成尼龙6(PA6),获得PS为连续相、GO选择性分布于球状PA6分散相的PA6/PS/GO三元混合物,最后去除PS相制备PA6/GO复合微球。采用扫描电镜、透射电镜、热失重及差示扫描量热等方法,研究了GO在三元混合物中的选择分布、PA6/GO复合微球的结构及耐热性。结果表明,在三元混合物中GO选择性分布于PA6相中;随着GO含量增加,PA6/GO复合微球的直径减小;与纯PA6微球相比,PA6/GO复合微球具有更高的热稳定性。     

粒径可控3D打印用PA6/12粉末制备及热性能研究

以己内酰胺(CL)、十二内酰胺(LL)和聚苯乙烯(PS)为主要原料,通过内酰胺单体阴离子开环聚合制得聚酰胺6/12/PS(PA6/12/PS)合金,通过溶去PS相得到PA6/12粉末。利用FT-IR、SEM、DSC、白度仪等手段对合金体系和PA6/12粉末的微观形貌、热性能等进行研究。结果表明:当PS用量为20%(wt,质量分数),CL∶LL=70∶30时,PA6/12粉末平均粒径达到32μm,性能与市场上的PA12(EOS)粉末接近。     

单分散中空聚苯乙烯微球制备

采用搅拌乳化方法制备水包油(W1/O)型乳状液,经膜乳化法制得单分散的复乳(W1/O/W2)型乳状液,再通过液中干燥法制得单分散中空聚苯乙烯(PS)微球.考察了shirasu porous glass(SPG)膜孔径对乳状液液滴粒径及粒径分布、表面活性剂浓度对PS微球中空率和单分散性的影响.由激光粒度分析仪结果及PS微球的SEM照片证实,制得的PS微球,粒径呈单分散,是SPG膜孔径的2.0～2.4倍且具有中空结构.     

单分散Eu~(3+)-PS荧光微球的制备及性能

采用分散聚合法研究了单分散纳米聚苯乙烯(PS)微球和宽稀土含量荧光PS微球的合成。在沸水排氧条件下,分别研究了单分散纳米PS微球、稀土配合物(Eu(MAA)3phen)与苯乙烯(St)共聚微球的合成和反应体系稳定性控制,成功制备出了粒径范围在120~260 nm的单分散PS微球及Eu~(3+)-PS共聚物荧光微球,拓宽了分散聚合制备PS微球的粒径范围。采用红外光谱、同步热分析、扫描电镜和透射电镜对产物的结构进行了表征,紫外光谱和荧光光谱对产物的光学性能进行了测试。结果表明产物的单分散性良好,具有Eu~(3+)离子的特征荧光发射。     

分散聚合法制备粒径可控的单分散聚苯乙烯微球

以苯乙烯(St)为单体,偶氮二异丁腈(AIBN)为引发剂,聚乙烯吡咯烷酮(PVP)为分散剂,乙醇/水为分散介质,采用分散聚合法制备了聚苯乙烯(PS)微球。研究了单体、引发剂、分散剂的浓度,分散介质中乙醇与水的比例对制备PS微球粒径及粒径分布的影响。采用傅立叶红外光谱(FT-IR)、透射电子显微镜(TEM)、场发射扫描电镜(FE-SEM)、动态光散射(DLS)等手段,对微球的组成成分、表面形貌、粒径及其分布进行了表征。结果表明,在合适条件下,分散聚合法可以制备粒径200～1000nm范围内可控、球形度良好、表面光滑、互不粘连的单分散PS微球。     

PS微球的制备及三维胶晶模板的组装和应用

研究了PS微球合成中单体、引发剂和乳化剂浓度以及聚合温度对粒径及分布的影响。采用高速离心沉淀法、恒温加热蒸发诱导法和自然沉降法对单分散PS微球进行了组装,得PS胶体晶体模板,并以其为模板制备了锂离子筛前驱体Li4Mn5O12。用纳米粒度及ZETA电位分析仪、扫描电子显微镜(SEM)、饱和交换容量等表征了材料的粒径及分布、形貌、结构和离子交换性能。结果表明:通过控制反应条件可以在一定范围内制得粒径均一、单分散性好、表面规整光滑的PS微球;PS胶体晶体模板三维有序,排列规整;酸改性后的离子筛前驱体对Li+饱和交换容量为7.49mol/g锂离子筛。     

胶晶/嵌段共聚物双重模板制备多级孔材料

采用分段乳液聚合法和无皂乳液聚合法制备了聚苯乙烯(PS)微球,以此单分散胶态晶体和嵌段共聚物P123为模板剂,通过Y型分子筛前驱体的填充和模板剂的去除制备了具有大-介-微多级孔的材料.采用XRD、SEM和TEM等手段表征了PS微球及多级孔材料.结果表明,分段乳液聚合可以制备平均粒径为50nm的PS微球,无皂乳液聚合可以制备450nm左右的PS微球;以其作为大孔模板剂分别考察了PS微球粒径、模板剂用量、水用量等因素对多级孔材料合成的影响,结果表明,PS微球的粒径越大,材料中大孔的分散性越好.合成多级孔材料的条件为:PS微球乳液与前驱体的比值(质量比)为1.0~0.5,水与前驱体的比值为7.5,P123与前驱体的比值为0.1.     

用AFM力曲线技术测定聚合物微球的压缩杨氏模量

用无皂乳液聚合法制备了粒径为200-500nm的单分散聚苯乙烯(PS)微球。依靠正负电荷间作用力将样品分散在经过亲水处理的硅热氧化片刚性衬底上,借助原子力显微镜纳米压痕技术测定了PS颗粒样品的力学性质;依据样品的力-位移曲线,根据弹性力学接触模型,计算出PS微球样品的压缩杨氏模量为2-3 GPa(Hertz模型)和2-6 GPa(Sneddon模型)。结果表明,微球样品的杨氏模量计算值略低于PS块体材料,且随着粒径的增加而缓慢增大。Hertz模型更适于计算本文制备的亚微米级PS微球的压缩杨氏模量。     

微晶纤维素的表面改性对己内酰胺聚合的复合材料性能的影响

利用2,4-甲苯异氰酸酯(TDI)对微晶纤维素(MCC)进行改性,将改性前后的纤维素(MCC和TMCC)分散到己内酰胺(CL)中并利用CL阴离子开环聚合制备得到MCC/PA6和TMCC/PA6复合材料,研究TDI对MCC表面改性对复合材料的影响。扫描电子显微镜和傅立叶红外光谱结果表明TDI和MCC表面发生了接枝反应。比较复合材料中CL的转化率,发现TMCC/PA6复合材料中CL的转化率比MCC/PA6复合材料中CL的转化率高;测试复合材料中PA6和纯PA6的分子量,结果表明TMCC/PA6复合材料中PA6的分子量明显高于MCC/PA6复合材料中PA6的分子量;测试MCC、TMCC含量为1%(质量分数)的复合材料与纯PA6在250℃的剪切粘度,发现复合材料在250℃下剪切粘度在低频下均比PA6高,且前者最高,高频时两者趋向一致。     

超声波辅助制备单分散金属包覆聚苯乙烯导电微球

为了制备单分散聚合物基导电微球,以交联聚苯乙烯(PS)微球为基体,通过超声波辅助的化学镀方法制备了单分散Ni/PS导电微球,接着采用置换法在导电微球表面包覆一层导电性更好的Au层。采用FI-IR,SEM,EDS,XRD等测试方法分别对PS微球及导电微球的官能团变化、形貌、元素组成及晶型结构进行表征,结果表明:超声的引入可以改善导电微球的分散性;导电微球形貌规则,镀层连续均一且有纳米级"丘状"突起。经过金层包覆后导电微球的体电阻率可达到6.9×10-3Ω.cm,可以满足ACF中导电微球的使用要求。     

Preparation of micron-sized PA6/12 copolymer microspheres via successive in-situ polymerization

Micron-sized polyamide 6/12 (PA6/12) copolymer microspheres were firstly synthesized via successive in-situ polymerization of styrene (free radical polymerization), equimolar Laurolactam (LL) and Caprolactam (CL) (anionic ring-opening polymerization). The resulting PA6/12 microspheres were regular sphericity, with diameter ranging from 9.2 to 138.0 microns and narrow size distribution (size distribution ranging from 1.2 to 3.3), as confirmed by scanning electron microscopy (SEM) and Laser diffraction size Analyzer. Furthermore, the study on the PA6/12 microspheres in PA6/12 and PS (PA6/12/PS) blends confirmed that the particle size distribution, diameter of PA6/12 microspheres were controllable, and closely related to the content of PS in the blends, which indicated that the formation of the PA6/12 microspheres in the PA6/12/PS blends can be elucidated via a phase inversion mechanism.     

聚苯乙烯/聚酰胺-12合金的选择性激光烧结成形

在选择性激光烧结(SLS)成形中,聚苯乙烯(PS)成形件精度高但其力学性能差,而聚酰胺-12(PA12)成形件力学性能高但其尺寸精度较差。为此,通过添加增容剂合成了PS/PA12合金粉末并用于SLS成形,研究了PS/PA12合金、PS及PA12成形件的力学性能、精度及断口微观形貌。结果表明,PS/PA12合金成形件的拉伸强度、断裂伸长率、冲击强度、弯曲强度及弯曲模量分别是PS成形件的4.72倍、1.94倍、4.92倍、4.57倍及1.37倍;PS/PA12合金粉末成形件在x、y及z方向的尺寸误差比PA12分别降低了46.9%,47.3%及20.3%。说明PS/PA12合金粉末成形件兼顾了PS成形件精度高及PA12成形件力学性能好的优点,具有较高的推广使用价值。     

Preparation of PA12 microspheres with tunable morphology and size for use in SLS processing

Materials technology is currently a great challenge in selective laser sintering (SLS). The development of new method for the preparation of a variety of materials has drawn great attention from both industrial and academic organizations. In this work, we described a simple strategy to prepare polyamide 12 (PA12) microspheres through a modified phase-separation process. The phase separation was conducted by adding ethanol as a poor solvent into a formic acid solution of PA12 pellets with polyvinyl pyrrolidone as a dispersant. The mean diameters of the obtained PA12 microspheres, ranging from tens to hundreds of micrometers, were well controlled by adjusting the amount of ethanol and the phase separation temperature. Further investigation by differential scanning calorimetry demonstrated that the sintering window for PA12, between the onset temperatures of crystallization and melting, was drastically stretched during the microsphere formation process. The PA12 particle size and morphology, together with the wider sintering window of the microspheres, demonstrated that the obtained PA12 powder was suitable for SLS processing.     

固相剪切碾磨制备尼龙12/多壁碳纳米管复合粉体及选择性激光烧结3D打印

采用固相剪切碾磨(S~3M)技术并结合冷冻粉碎制备了适于选择性激光烧结(SLS)的尼龙12(PA12)/多壁碳纳米管(CNTs)复合粉体及相应的烧结制品。采用激光粒度分析仪、扫描电镜、透射电镜、动态力学分析、傅里叶变换红外光谱分析、差示扫描量热仪等对所得PA12/CNTs复合粉体和相应SLS制品的结构与性能进行了表征。结果表明,固相剪切碾磨-冷冻粉碎制备的复合粉体颗粒以椭球形为主,平均粒径75μm,SLS加工窗口为10℃左右,满足SLS对被烧结材料的性能要求,通过加入质量分数为0.1%的流动助剂纳米SiO_2能进一步改善复合粉体的SLS加工性能。磨盘碾磨通过其强大的三维剪切力场实现了CNTs的切割及在PA12基体中的良好分散以及CNTs与PA12大分子链的接枝,显著改善了二者之间的界面相容性。此外,通过优化SLS加工参数,成功制备了表面平整、结构复杂、性能良好的PA12/CNTs烧结制品。所得PA12/CNTs烧结样品具有优良的力学性能,拉伸强度达到44.2 MPa,缺口冲击强度达到8.12 k J/m~2。     

Selective laser sintering of porous tissue engineering scaffolds from poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactide)/carbonated hydroxyapatite nanocomposite microspheres

This study focuses on the use of bio-nanocomposite microspheres, consisting of carbonated hydroxyapatite (CHAp) nanospheres within a poly(L: -lactide) (PLLA) matrix, to produce tissue engineering (TE) scaffolds using a modified selective laser sintering (SLS) machine. PLLA microspheres and PLLA/CHAp nanocomposite microspheres were prepared by emulsion techniques. The resultant microspheres had a size range of 5-30 mum, suitable for the SLS process. Microstructural analyses revealed that the CHAp nanospheres were embedded throughout the PLLA microsphere, forming a nanocomposite structure. A custom-made miniature sintering platform was installed in a commercial Sinterstation((R)) 2000 SLS machine. This platform allowed the use of small quantities of biomaterials for TE scaffold production. The effects of laser power; scan spacing and part bed temperature were investigated and optimized. Finally, porous scaffolds were successfully fabricated from the PLLA microspheres and PLLA/CHAp nanocomposite microspheres. In particular, the PLLA/CHAp nanocomposite microspheres appeared to be promising for porous bone TE scaffold production using the SLS technique.     

选择性激光烧结用尼龙12覆膜Cu粉的制备

提出了溶剂沉淀法制备选择性激光烧结(SLS)用尼龙12覆膜Cu粉复合粉末材料,利用扫描电镜(SEM)观察了复合粉末材料的微观形貌,通过差示扫描量热分析(DSC)、热重分析(TGA)对复合粉末材料的熔融、结晶行为,烧结温度窗口及热稳定性进行了研究,并测试了其烧结件的力学性能。结果表明,复合粉末材料的熔点、结晶速度及热稳定性较纯尼龙粉末有所提高,烧结温度窗口变宽,因而烧结性能优于纯尼龙粉。复合粉末材料烧结件的弯曲强度、弯曲模量、硬度均高于纯尼龙粉的烧结件。     

Viscoelastic Properties and Creep-Fatigue Behavior of PA2200/HA Composites Manufactured by Selective Laser Sintering

Porous(polyamide/hydroxyapatite)composites were manufactured via SLS(selective laser sintering)process.Specimens with different PA2200/HA contents(100/0;95/5;90...     

尼龙12覆膜铝粉激光烧结成形件的性能研究

常用的机械混合法很难将尼龙12和金属粉末材料混合均匀,容易出现偏聚,因而会造成选择性激光烧结(SLS)成形件中存在局部强度弱点、翘曲等缺陷.为此,提出了通过溶液沉淀法制备SLS成形用尼龙12覆膜铝粉,利用扫描电镜观察了尼龙12覆膜铝粉及烧结件断口的微观形貌,研究了铝粉含量及粒径对SLS成形件性能的影响.结果表明:尼龙12均匀地包覆在铝粉表面,无裸露铝粉颗粒存在,表明成功制备得到了尼龙12覆膜铝粉材料;当铝粉含量从0增大到50%时,烧结件的热变形温度、拉伸强度、弯曲强度、弯曲模量及硬度比纯尼龙烧结件分别提高了87℃、10.4%、62.1%、122.3%及70.4%;烧结件的拉伸强度、断裂伸长率及冲击强度均随着铝粉平均粒径的减小而增大.     

A novel method for the synthesis of polyamide 6 magnetic microspheres

Polyamide 6 (PA6) magnetic microspheres were firstly prepared via successively in situ polymerization using phase inversion technology of polymer pairs polyamide 6/polystyrene (PA6/PS) at extremely low PS content. The properties of PA6 magnetic microspheres, such as morphologies, diameter size distribution, magnetic properties, thermal stability, and the functional groups of the magnetic microspheres, were investigated by different techniques (i.e. SEM, TEM, DLS, VSM, FTIR, and DSC). The results indicated that the diameter distribution of PA6 magnetic microspheres was narrow, and the mean diameter size was about 7.7 μm. The saturation magnetization of magnetic microspheres reached 12.50 emu/g. Furthermore, the magnetic microspheres had abundant functional groups and better thermal stability.     

Preparation, characterisation and processing of carbon fibre/polyamide-12 composites for selective laser sintering

Aiming at developing carbon fibre/polyamide-12 (CF/PA) composite powders for manufacturing high-performance components by selective laser sintering (SLS), the preparation, characteristics and sintering process of the composite powders and mechanical properties of sintered components were studied. Surfaces of the carbon fibres were treated by the oxidation modification and coated with polyamide-12 through the dissolution-precipitation process to provide good interfacial adhesion and homogenous dispersion within the polyamide-12 matrix. The particle size and micro-morphology analyses show that the CF/PA composite powders with 30 wt%, 40 wt% and 50 wt% carbon fibres present the suitable powder sizes and format for SLS. The incorporation of carbon fibres into the polyamide-12 matrix decreases the initial melting temperature and consequently lowers the SLS part bed temperatures, implying lower energy requirement and less thermal degradation in the sintering process. The CF/PA composites also represent higher thermal stability than the pure polyamide-12. The CF/PA sintered components with 30 wt%, 40 wt% and 50 wt% carbon fibres exhibit the greatly enhanced flexural strengths by 44.5%, 83.3%, 114%, and the flexural modulus by 93.4%, 129.4%, 243.4%, respectively, as compared with the pure polyamide-12 sintered parts. Fractured surface analysis shows that the carbon fibres are encapsulated and bonded well with the polyamide matrix. The complex SLS parts with the thinnest wall of 0.6 mm, the density of 1.09 ± 0.02 g/cm³ and the relatively density of 94.13 ± 1.72% were manufactured using the CF/PA composite powder with 30 wt% carbon fibres. This study demonstrates that the CF/PA composite powders prepared by the surface treatment and dissolution-precipitation method represent suitable interfacial adhesion, filler dispersion, particle sizes and sintering behaviours for SLS and enable the manufacture of complex components with high performance.