Polyamide hydrolysis accelerated by small weak organic acids

It is well known that acidity, pH, of a solution accelerates the hydrolysis of soluble amides. Here we describe the unexpected result that weak small organic acids at low concentrations hydrolyze a polyamide at rates approximately twice that of a water HCl solution of the same pH. The effect of three small organic acids in dilute solutions, acetic, propanoic, and butanoic was studied. It is observed that the effect on the hydrolysis rate increases as the organic acid gets weaker. Butanoic, the weakest acid, has the strongest effect on increasing the hydrolysis rate. Measurements on the concentration of these acids in the polyamide reveal that there is a selective desire for these weak organic acids to diffuse into the polyamide. The concentration of these acids in the polyamide is found to be several multiples of the concentration in the water environment. And the acid concentration is highest for butanoic. The hydrolysis rate is shown to be governed by solubility, not pH of the water environment. The longer hydrocarbon tail on the carboxylic group increases its compatibility with the polyamide's monomer structure. Results are reported on the hydrolysis of polyamide-11 polymerized from aminoundecanoic acid, both neat and a commercial plasticized composition, placed in water at 100 °C and 120 °C under anaerobic conditions in high pressure glass tubes.     

Novel composite nanofibers based on polyamide 66/graphene oxide- grafted aliphatic- aromatic polyamide: preparation and characterization

New polyamide 66/graphene oxide (GO)-grafted aliphatic-aromatic polyamide (polyamide-imide) (PAI) (PA66/GOF) composites nanofibers were successfully prepared via electrospinning method for the first time. An polyamide imide (PAI) was synthesized using polycondensation reaction from a dicarboxylic acid and a diamine based on 4,4′-(4,4′-isopropylidenediphenyl-1,1′-diyldioxy) dianiline, and characterized by ¹HNMR and FTIR. Morphological, structural, thermal and mechanical characteristics of the nanocomposite fibers were investigated by means of SEM, TEM, WAXD, DMTA and TGA techniques. Composites nanofibers of PA66/GO, PA66/PAI and PA66/GOF with smooth surface, uniform structure as well as with diameter ranging from 195 to 784 nm were obtained. The GO incorporation caused a reduction in the nanofibers diameters. The TEM images showed that the GO was well dispersed in the PA66 nanofibers without significant aggregation. An approximately 10 °C temperature increase in the glass transition temperature of PA66 was achieved by addition of 0.5 wt% of PAI, resulting from aliphatic-aromatic structure of PAI. By the TGA results, an increase about 40 °C was observed in the thermal stability of PA66/PAI composite nanofibers in comparison with that of pure PA66 nanofibers.     

成核剂和乙烯马来酸酐共聚物混杂改性玻璃纤维增强聚酰胺复合材料

利用静电吸附方法制备了成核剂(P22)和乙烯马来酸酐共聚物(EMA)混杂改性的玻璃纤维(GF)增强体,并通过挤出成型制备了聚酰胺66(PA66)/改性GF增强体复合材料。采用扫描电子显微镜观察复合材料断面和刻蚀后断面。结果表明,P22吸附在GF表面可以诱导PA66在GF表面结晶,而EMA分子中的酸酐基团则可以与PA66分子链末端的氨基发生反应,使PA66附着在GF表面,改善了GF与基体的界面结合;良好的界面结合使PA66/GF-P22 、PA66/GF-EMA、PA66/GF-EMA-P22复合材料的层间剪切强度和动态储能模量(室温25 ℃)分别提高了18.3 %、25.4 %、32.4 %和15.4 %、24.1 %、35.9 %。     

Influence of thermal processing on the perfection of crystals in polyamide 66 and polyamide 66/clay nanocomposites

A study of the changes in crystal perfection of polyamide 66 (PA66) and polyamide 66/clay nanocomposites (PA66CN) due to different thermal processing was carried out. We designed three series of thermal processing including melt-quench (MQ), post-annealing MQ sample (MQA), and melt–slow cooling–annealing (MSA). The annealing temperature was set as 180 or 210 °C, which is within Brill temperature range of PA66. Fourier transform infrared (FT-IR) spectroscopy and wide angle X-ray diffraction (WAXD) were employed to characterize the perfection in short-range order and long-range order structures, respectively. The results showed that the crystal perfection of PA66 and PA66CN with different thermal processing is quite different, and the changing fashions with thermal processing for different ordered structures are not similar. In this work, MSA is optimal thermal processing for high crystallinity and crystal perfection. Exfoliated nanoclay layers exert considerable impact on the perfection of long-range ordered structures, but little on that of short-range ordered ones.     

溶剂沉淀法制备的聚酰胺粉末之溶剂与粉末结构和热稳定性的关系

使用粒度分布仪、白度仪、电子显微镜和差热仪测定四种溶剂沉淀法制备的聚酰胺粉末发现：每种方法所获得的粉末粒径、比表面积、白度均不相同；以乙醇 氯化钙混合溶剂制备的粉末内部具有多孔结构；以乙醇 盐酸 水混合溶剂制备的粉末热稳定性较高     

The Effect of Compatibilizer on Morphology and Mechanical Properties of PA6/UHMWPE Blends

Abstract

This work deal with the effect of compatibilizer on the morphological and mechanic properties of polyamide 6 and ultrahigh molecular weight polyethylene (PA6/UHMWPE) blends. The blends were prepared by means of a twin-screw extruder. The compatibilizer was produced by grafting maleic anhydride (MAH) onto high density polyethylene (HDPE). The resulting HDPE-g-MAH was used to prepare ternary blends of PA6/HDPE-g-MAH/UHMWPE by melt mixing. The size of domain of UHMWPE in PA6/HDPE-g-MAH/UHMWPE blends is much smaller than that in PA6/UHMWPE blends. It was found that mechanical properties of PA6/HDPE-g-MAH/UHMWPE blends obviously surpassed that of PA6/UHMWPE blends. These behavior could be attributed to chemical reactions between MAH in HDPE-g-MAH and terminal amino groups of PA6. Thermal analysis were performed to confirm the possible chemical reactions taken place during the blending process.     

聚酰胺类合金分离膜研究进展

介绍了聚酰胺分离膜材料共混对膜的亲水性、耐污染性、物化稳定性的影响;总结了合金膜材料间相容性对膜结构和性能的影响以及影响膜材料相容性的因素。     

Solid State Shear Milling to Prepare Magnesium Hydroxide Flame-Retardant Polyamide 6 with High Performance

A novel processing method, that is, solid state shear milling (S3M), was adopted to compound high loading inorganic flame-retardant magnesium hydroxide with polyamide 6 by using our self-designed pan-mill equipment. S3M can effectively pulverize PA6, increase the interfacial interaction of the resin and magnesium hydroxide, and achieve their even blending, thus effectively controlling the state of the dispersion phase in solid state. With the co-milled composite powder as flame retardant master batch filled in original PA6 pellets, it can greatly improve the compatibility of the system, modify the distribution process of magnesium hydroxide, and decrease the dispersion phase size in the following melt processing. As a result, S3M technology can remarkably increase the melt flowability of the composite materials, and obtain obviously enhanced flame retardance and mechanical performance, thus providing an effective solution to the poor processibility and deteriorated performance of magnesium hydroxide flame-retardant PA6 obtained through direct melt processing.     

纳米磷灰石晶体/聚酰胺复合骨组织工程支架材料的研究

采用常压共溶、共沉淀和水热处理的方法制备了纳米磷灰石晶体／聚酰胺复合骨组织工程支架材料。纳米磷灰石在复合材料中含量高达60wt％(重量比),纳米磷灰石和聚酰胺之间有化学键结合,材料的力学性能接近自然骨水平。复合材料可加工成块状多孔体,材料的孔隙率为55％-70％,平均孔径为300μm,多孔支架不仅有大孔,而且大孔壁上含有丰富微孔,是一种非常有发展前景的组织工程材料。     

Photo-induced alignment behavior of azobenzene compound in thin film

Photo-induced molecular alignment behavior of spin-coated poly(4,4′-azobenzene pyromellitamic acid) (PAA(azo)) film was investigated by Fourier transform infrared spectroscopy measurement, atomic force microscope and transmission electron microscope observation. As-spun PAA(azo) flm was found to be smooth and uniform with an amorphous structure. Upon irradiation of linearly polarized ultraviolet light, the molecular ordering and crystallization were induced, and the film surface was roughened slightly. The PAA(azo) film converted to poly(4,4′-azobenzene pyromellitimide) (PI(azo)) film with higher ordering and crystallinity by subsequent thermal treatment. The PI(azo) film was useful as an active layer to introduce the molecular alignment of copper phthalocyanine (CuPc).