共聚聚丙烯的球晶形貌研究

利用偏光显微镜和生物显微镜研究了在不同条件下培养的共聚聚丙烯球晶的形貌。结果表明:在淬火条件下,只能得到微米级的微晶;在空气中降温、在培养炉上缓慢降温及恒温培养条件下,均可获得大小不一的大尺寸多面体形貌的球晶;在缓慢降温培养条件下,可培养出典型的带分枝微纤结构的球晶;采用生物显微镜,观察到共聚聚丙烯球晶中的发射状微纤、球晶形貌和晶界。     

尼龙-6球晶形貌的研究

利用偏光显微镜，研究了不同培养条件下制备的PA-6熔融结晶球晶形貌。结果表明：随着培养时间的增加，PA-6球晶的尺寸明显增大且可观察到完整的大小不一的多面体球晶；PA-6的晶核产生以均相成核为主；降温速度对PA-6球晶的生长程度影响显著；在晶体样片的不同区域，PA-6球晶的形貌呈现出明显差异；在负荷作用下培养的晶体，在显微镜下具有较高的衬度。     

成核剂对尼龙66结晶行为和力学性能的影响

分别以四角状氧化锌晶须、蒙脱土和硫酸镁晶须为成核剂,制备了尼龙66的薄膜样品,通过偏光显微镜观察、拉伸性能测试等方法研究了不同成核剂种类和用量对尼龙66结晶行为和力学性能的影响。结果表明,成核剂的添加使尼龙66球晶尺寸变小和结晶度增加,拉伸强度和断裂伸长率增加,其中四角状氧化锌晶须成核剂效果最好。     

PA6/CaCO3复合材料的单边缺口拉伸断裂研究

研究了尼龙6(PA6)/CaCO3复合材料的单边缺口拉伸断裂。结果表明,PA6/CaCO3复合材料在拉伸速率为0.1～300 mm/min的缺口拉伸实验中,裂纹扩展均为脆性断裂。断口主要分为塑性屈服变形区和弹性变形区两部分。塑性屈服变形区形貌是以缺口根部为底边的圆弧型,弹性变形区将塑性屈服变形区包围在里面。塑性屈服变形区面积到达临界尺寸后,材料瞬间断裂。断裂后观察到的塑性屈服变形区面积即为在该实验条件下的裂纹源面积。随着拉伸速率增加,其裂纹源面积减小,而弹性变形区域增加,弹性储存能的储存速度增加,在其裂纹源面积较小的情况下即可发生瞬间脆断。     

苯乙烯–马来酸酐共聚物中空微球在尼龙6轻量化中的应用

采用苯乙烯–马来酸酐共聚物中空微球对尼龙6的轻量化改性进行了研究。采用傅立叶变换红外光谱仪对苯乙烯–马来酸酐共聚物中空微球进行了表征,采用差示扫描量热仪和热失重分析仪对苯乙烯–马来酸酐共聚物中空微球进行了热分析。将苯乙烯–马来酸酐共聚物中空微球以不同比例与尼龙6熔融共混制备轻量化共混料,测定其成型样品的减重效果和拉伸性能并采用扫描电子纤维镜表征共混物中中空微球的结构与形态。结果表明,中空微球具有良好的刚性和耐热性,与尼龙6相容性良好。当中空微球添加量为5%时,尼龙6/苯乙烯–马来酸酐共聚物中空微球共混物的实际质量减轻10%,拉伸强度为40 MPa。     

溶胶-凝胶法制备纳米二氧化硅微球的研究

采用溶胶-凝胶法制备纳米二氧化硅,通过傅里叶红外光谱表征成分,用800倍数码显微镜观察表面形貌,探讨不同反应条件对纳米二氧化硅表面形貌的影响。纳米二氧化硅微球在不同溶剂中的分散性。结果表明,在酸、碱条件下,分别生成纳米二氧化硅溶胶和纳米二氧化硅微球;碱性条件下,反应温度和反应时间分别为40℃和4 h时,纳米二氧化硅微球呈现规整、均一的球型形貌;纳米SiO_2微球在有机溶剂中的分散性都较好,且分散均匀。     

拉伸速率对尼龙6力学性能和颈缩区结晶度的影响

以己内酰胺为原料,通过开环聚合法制备了尼龙6材料。利用电子万能试验机对尼龙6材料进行了10,20,50 mm/min三种不同速率的拉伸实验,结果表明,随着拉伸速率的增加,尼龙6的屈服强度略有增加,而断裂伸长率和断裂能则大为减少。利用差示扫描量热仪对拉伸后试件的结晶度进行了测试,结果表明,在颈缩区有新的晶型生成;随着拉伸速率的增加,结晶度也随之增大,当拉伸速率为50 mm/min时,其颈缩区结晶度比初始结晶度提高了27.5%。     

溶胶-凝胶法制备纳米二氧化硅微球的研究

采用溶胶-凝胶法制备纳米二氧化硅,通过傅里叶红外光谱表征成分,用800倍数码显微镜观察表面形貌,探讨不同反应条件对纳米二氧化硅表面形貌的影响。纳米二氧化硅微球在不同溶剂中的分散性。结果表明,在酸、碱条件下,分别生成纳米二氧化硅溶胶和纳米二氧化硅微球;碱性条件下,反应温度和反应时间分别为40℃和4 h时,纳米二氧化硅微球呈现规整、均一的球型形貌;纳米SiO_2微球在有机溶剂中的分散性都较好,且分散均匀。     

溶解在聚丙烯熔体中的微量空气对聚丙烯聚态结构及球晶氧化脆裂的影响

用热台偏光显微镜法观察了各种稳定体系的PP熔体的等温结晶过程,发现溶解在PP熔体中的微量空气可被排出生长着的球晶边界,在成核密度较低的区域浓集成微气泡。本文讨论了微气泡的行为,表明它不仅有育成核作用,而且对PP球晶的氧化脆裂有直接影响。     

有机化纳米SiO2填充改性尼龙6复合材料的研究

通过酰氯化法制备了有饥化的纳米SiO2，用熔融共混法制备了尼龙6／有机化纳米SiO2复合材料，研究了复合材料的力学性能和结晶形态。研究表明：有机化纳米SiO2的加入能够提高尼龙6的拉伸强度和冲击强度，改性效果明显好于未经表面处理的纳米SiO2；偏光显微镜照片显示，有机化纳米SiO2的加入起到了异相成核的作用，使尼龙6的结晶形态发生了改变，由大的球晶变为细小的晶粒。     

Properties of nylon-6-based composite reinforced with coconut shell particles and empty fruit bunch fibres

Novel natural fibre composites of nylon-6 reinforced with coconut shell (CS) particles and empty fruit bunch (EFB) fibres have been investigated. Fillers were alkali treated before melt compounding with nylon-6. Mechanical, thermal and rheological properties of composites were measured. Tensile modulus was found to improve with both fillers up to 16% for nylon-6/CS composite and 10% for nylon-6/EFB composite, whereas a moderate increase in tensile strength was observed only with CS composites. Differences in the strengthening mechanisms were explained by the morphology of the two fillers, empty fruit bunch fibres having a weaker cellular internal structure. Observation of composite morphology using SEM showed that both fillers were highly compatible with nylon-6 due to its hydrophilic nature. Both fillers were found to cause a slight drop in crystallinity of the nylon matrix and to lower melt viscosity at typical injection moulding strain rates. Moisture absorption increased with addition of both fillers.     

Compared structure and morphology of nylon-12 and 10-polyurethane lamellar crystals

A comparative study of the structure and morphology of nylon-12 and 10-polyurethane (10-PUR) lamellar crystals, was carried out. Lamellar crystals were obtained by isothermal crystallization from diluted solution. Electron diffraction of lamellae combined with WAXS data recorded from crystal sediments indicated that nylon-12 crystallized in either α-form or γ-form according to the solvent chosen for crystallization. The α-form was the crystal modification predominant in doubly oriented films of nylon-12 prepared by epitaxial crystallization. On the contrary, 10-PUR invariably crystallized in α-form regardless crystallization conditions. The α-form of nylon-12 and 10-PUR shared the same crystal structure with hydrogen-bonded sheets made of antiparallel chains and stacked with progressive shifting along both b and c directions. Lamellar crystals of nylon-12 in γ-form and 10-PUR in α-form displayed similar morphological features but only the former appeared to be sensitive to temperature. Upon heating the nylon-12 crystals near to melting, the real-time WAXS analysis evidenced the occurrence of a partial γ-to-α crystal transition, and in situ AFM observations revealed the appearing of more or less regular ridges on the crystal surface. None of these changes were observed in 10-PUR crystals when subjected to similar treatment.     

基布对聚氨酯合成革性能影响的研究

以涤纶非织造布，锦纶非织造布作基布，制作了聚氨酯浸渍试样，研究了其拉伸，弯曲性能，认为由于锦纶与聚氨酯的结合较强，影响了锦纶基布柔软性的发挥。当上浆率超过一临界值时，锦纶基布聚氨酯合成革已不如涤纵横在布聚氨酯合成革柔软。     

A study on blends of nylon-6 and nylon-66

Blending of nylon-6 and nylon-66 was carried out by coextrusion in the whole range of compositions with particular emphasis on small amounts of one polymer in the other. Most significant improvement in properties is achieved at low blend compositions in which the minor component remains amorphous while severely affecting the crystallization behavior of the major component. The nylon-6-rich blends crystallize predominantly in the γ-crystalline form, whereas the nylon-66-rich blends exhibit low crystallinity. Because of this property, the blends are more easily drawable, giving rise to a more highly oriented structure with improved tensile properties and uniformity. High tenacity and modulus are observed in drawn blends containing 70% nylon 6 and 30% nylon-66.     

Studies on electrospun nylon-6/chitosan complex nanofiber interactions

Composite membranes of nylon-6/chitosan nanofibers with different weight ratio of nylon-6 to chitosan were fabricated successfully using electrospinning. Morphologies of the nanofibers were investigated by scanning electron microscopy (SEM) and the intermolecular interactions of the nylon-6/chitosan complex were evaluated by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), differential scanning calorimetry (DSC) as well as mechanical testing. We found that morphology and diameter of the nanofibers were influenced by the concentration of the solution and weight ratio of the blending component materials. Furthermore FT-IR analyses on interactions between components demonstrated an IR band frequency shift that appeared to be dependent on the amount of chitosan in the complex. Observations from XRD and DSC suggested that a new fraction of γ phase crystals appeared and increased with the increasing content of chitosan in blends, this indicated that intermolecular interactions occurred between nylon-6 and chitosan. Results from performance data in mechanical showed that intermolecular interactions varied with varying chitosan content in the fibers. It was concluded that a new composite product was created and the stability of this system was attributed to strong new interactions such as hydrogen bond formation between the nylon-6 polymers and chitosan structures.     

有机改性蒙脱土制备聚酰胺6/蒙脱土复合材料

采用有机复合改性的方法制备了改性蒙脱土,并采用原位聚合方法制备了尼龙-6/蒙脱土复合材料,利用FTIR、TG-DTA、XRD对有机蒙脱土进行了表征。结果表明,有机插层剂已进入蒙脱土的层间,使蒙脱土的层间距由原来的1.39 nm增大到2.32 nm,从而改善了它的分散性以及与尼龙-6之间的粘结作用,二者构成的纳米复合材料具有很好的力学性能。当加入2%的有机蒙脱土时,拉伸强度提高16%,冲击强度提高5%。     

Performance of reprocessed multilayer LDPE/nylon-6 film

Multilayer LDPE/nylon-6 films with an overall content of 71 wt% LDPE, 24 wt% nylon-6, and 5 wt% PE-based tie-layer adhesive were reprocessed under both minimal and extensive mixing conditions. Thermal and mechanical properties, oxygen and water vapor permeability, and morphology of the reprocessed samples were determined. The modulus and yield stress of the reprocessed films fell between those of the pure homopolymers, whereas percent elongation at break and energy-to-break for all reprocessed films were less than those of the homopolymers. In minimally reprocessed film, layering of LDPE (low-density polyethylene) and nylon-6 was retained, whereas in extensively mixed samples, nylon-6 domains were spherical and ranged from 0.2 to 7 μm. Minimally reprocessed film exhibited good O₂ and H₂O vapor barrier properties, whereas extensively-mixed samples had poor barrier properties. Properties of well-mixed blends prepared both with and without adhesive showed that 5 wt% adhesive did not compatibilize the LDPE and nylon-6 components.     

Microstructure, nucleation and thermal properties of high-pressure crystallized MWCNT/nylon-6 composites

Multi-wall carbon nanotube (MWCNT)/nylon-6 composites made by in-situ polymerization and subsequently modified by treatment at 1.0 GPa (or 1.7 GPa) and 530 K have been studied by WAXD, DSC and NMR. The pressure treatment gives an amorphous to crystalline transformation where the crystallinity increases from ∼31% to as much as ∼58% concurrently as the nylon-6 crystals increase in size and attain a preferred orientation relative to the applied pressure. A composite of 2.1 wt% purified MWCNT in nylon-6 shows significantly higher melting temperature than neat nylon-6 after identical pressure treatments. The improved thermal stability of the composite is attributed to crystal growth in the presence of reinforcing MWCNTs. The NMR spectrum of a pressure treated composite is similar to that of nylon-6 single crystals, which suggests a reduction of crystal boundaries after treatment, but there is no indication of covalent bonds between the nylon-6 chains and the MWCNTs.     

Crystallization of polyamides under elevated pressure: 3. The morphology and structure of pressure-crystallized nylon-6 (polycapramide)

The morphology and structure of nylon-6, crystallized from the melt under elevated pressure, has been investigated. Scanning and transmission electron microscopy on replicas of the fracture surfaces reveal that crystallization under pressures exceeding 4 kbar (1 kbar = 100 MN/m²) results in rough lamellar structures with some step heights corresponding to the contour lengths of the chains. Infra-red spectroscopy on the pressure-crystallized nylon-6 shows a considerable improvement of crystalline order, a closer packing of the polymer chains within the crystal, and the presence of a large proportion of free N-H groups. An absorption band at 1170 cm^?1 was assigned to the presence of folds in the nylon-6 crystals. Wide-angle X-ray measurements indicate that the crystal modification of the pressure-crystallized nylon-6 is predominantly the alpha phase. Pressure gives rise to an increase in crystallite dimensions as well as to a decrease of the distance between the crystal planes bonded by the hydrogen bonds and by the Van der Waals forces.