EVOH树脂性能改进的研究

对比探讨多种牌号EVOH的改进方法和有关性能,并将最新开发出的几种新型EVOH性能与已广泛使用的牌号性能进行了比较.     

Mechanical properties of graphene and graphene-based nanocomposites

In this present review, the current status of the intrinsic mechanical properties of the graphene-family of materials along with the preparation and properties of bulk graphene-based nanocomposites is thoroughly examined. The usefulness of Raman spectroscopy for the characterization and study of the mechanical properties of graphene flakes and their composites is clearly exhibited. Furthermore, the preparation strategies of bulk graphene-based nanocomposites are discussed and the mechanical properties of nanocomposites reported in the literature are analysed. In particular, through the analyse of several hundred literature papers on graphene composites, we have found a unique correlation between the filler modulus, derived from the rule of mixtures, and the composite matrix. This correlation is found to hold true across a wide range of polymer matrices and thus suggests that the common assumption that the filler modulus is independent of the matric is incorrect, explaining the apparent under performance of graphene in some systems. The presence of graphene even at very low loadings can provide significant reinforcement to the final material, while the parameters that affect the nanocomposite strongly are thoroughly reviewed. Finally, the potential applications and future perspectives are discussed with regard to scale up capabilities and possible developments of graphene-based nanocomposite materials.     

Biodegradation of poly(vinylalcohol-co-ethylene) with the fungus phanerochaete chrysosporium

Under appropriate conditions for lignine peroxidase production in a culture medium that contains spores of Phanerochaete Chrysosporium fungus, the biodegradation of ethylene vinyl alcohol (EVOH) pellets with 27% mole of ethylene content was observed after 30 days. The oxidative degradation was detected by Fourier Transform Infrared Spectroscopy (FTIR) through the formation of hydroperoxides containing chains which were broken with degradation time. Differential Scanning Calorimetry (DSC) initially showed only one melting peak and after 30 days two peaks appeared on the thermogram, one due to the remaining copolymer that did not change with degradation time and the other due to the polymer degradation sequence. When EVOH film with a similar amount of ethylene was used, the initial melting temperature (T_m) decreased during degradation and a second crystalline sequence with a lower T_m was produced, indicating that both copolymer sequences were degraded. Observed differences in the biodegradative behavior between EVOH pellets and EVOH film were mainly due to the changes in crystallinity of the copolymer induced by film processing. The initial EVOH film showed a lower crystallinity and the presence of double bonds, which favors the degradative process. Received: 18 September 2000 / Reviewed and accepted: 20 September 2000     

紫外辐照对EVOH/纳米SiO2复合材料性能的影响

用硅烷偶联剂y-氨丙基三乙氧基硅烷（KH550）对纳米SiO2进行改性,采用熔融共混法制备了合SiO2的质量分数为5％的乙烯-乙烯醇共聚物（EVOH）／纳米SiO2复合材料,并吹塑成薄膜,将复合膜进行不同时间、不同强度的紫外辐照处理。利用FTIR、TEM、SEM对纳米SiO2和复合材料进行了表征分析,测试了复合材料紫外辐照处理前后的阻隔性能和力学性能。结果表明：纳米SiO2与偶联剂KH550形成化学键合,经紫外辐照处理的EVOH／纳米SiO2复合膜的力学性能、阻隔性能得到了较大地提高。     

偶联剂对EVOH/纳米SiO2复合材料结构与性能的影响

采用不同的偶联剂KH550、KH560、KH570和KH8431对纳米SiO2进行表面改性,采用熔融共混法将未改性和改性纳米SiO2(5%(质量分数)SiO2)与EVOH共混制成复合材料,并吹塑成薄膜。利用FT-IR、TEM、SEM对不同偶联剂处理的纳米SiO2和复合材料的结构进行表征,并对复合材料的流变性能、阻隔性能、力学性能、耐热性能和透明性进行了表征。结果表明,纳米SiO2与4种偶联剂均形成化学键合,改性纳米SiO2比未改性纳米SiO2在EVOH中分散性好,加工时熔体的流动性更好。用KH550处理的纳米SiO2在EVOH中分散性最好,与EVOH能形成较大界面相互作用力,与EVOH/未改性纳米SiO2复合材料相比,EVOH/改性纳米SiO2复合材料的拉伸强度和储能模量分别提高17.2%和136%,透湿、透氧系数分别下降11.2%和9.5%,透光率达到74.9%,雾度为14.9%。     

EVOH基体对EVOH纳米复合物力学性能的影响

为研究乙烯-乙烯醇共聚物(EVOH)基体对复合材料性能的影响,分别制备了EVOH-56(乙烯醇基含量为56%)/纳米TiO2复合材料、纳米ZnO复合材料、纳米蒙脱土复合材料,EVOH-68(乙烯醇基含量为68%)/纳米TiO2复合材料、纳米ZnO复合材料、纳米蒙脱土复合材料。根据TPT方程,分别计算出体系中各组分间相互作用相关的参数B,分析了基体对体系力学性能的影响。结果表明,EVOH-68/纳米TiO2,ZnO体系的参数B值小于EVOH-56/纳米TiO2,ZnO体系,并且相关力学性能数据也证明EVOH-68/纳米TiO2,ZnO体系的相间相互作用好,力学性能优于EVOH-56/纳米TiO2,ZnO体系。EVOH-56/纳米MMT体系和EVOH-68/纳米MMT体系的力学数据与TiO2,ZnO体系一起证明了复合体系的力学性能是两种机理竞争的结果。     

吹膜工艺对EVOH/纳米SiO2复合材料结构及性能的影响

采用熔融共混法制备了乙烯-乙烯醇共聚物（EVOH）/纳米SiO2复合材料,用不同的吹膜工艺对复合材料进行吹膜。通过偏光显微镜（POM）、差示扫描量热分析仪（DSC）、X射线衍射仪（XRD）测试对比了不同吹膜工艺制备的复合材料的结晶行为,并对复合材料的力学性能、阻隔性能和透明性进行了表征。研究发现,不同吹膜工艺改变了EV...     

热致相分离法制备EVOH亲水性微孔膜

以二乙二醇和PEG400为混合稀释剂,以乙烯摩尔分数为38%的乙烯-乙烯醇共聚物(EVOH38)为原料,用热致相分离法制备亲水性微孔膜.微孔膜形态分析表明当二乙二醇与PEG400质量比为2∶8,冷却方式为冰水淬冷时,得到的微孔断面为双连续网状结构.测定了EVOH38/二乙二醇/PEG400体系不同稀释剂组成的雾点和结晶温度,研究了稀释剂组成、冷却方式对微孔膜断面微观形态的影响,并且表征了所得平板膜的拉伸性能和纯水通量,结果表明该膜具有一定力学性能,较好水通量.     

热致相分离法制备平片式EVOH微孔膜研究

采用热致相分离方法,选择乙烯的摩尔分数为32%的乙烯-乙烯醇共聚物(EVOH)为原料,丙三醇为稀释剂制备了亲水性高分子平片式微孔膜,并研究了体系组成、冷却速率等对膜的结构和性能的影响.测试了膜的纯水通量、截留率和孔隙率,用泡点法测得了平均孔径.并用扫描电子显微镜(SEM)表征了微孔膜的断面形态.结果表明:分相的方式及微孔的形态由体系组成及冷却速率决定.降低聚合物浓度,延缓冷却速率,都有利于较大孔径膜的生成并得到较大的纯水通量和孔隙率,同时截留性能有所下降.     

Fracture behaviour of poly[ethylene–(vinyl alcohol)]/organo‐clay composites

BACKGROUND: Ethylene–(vinyl alcohol) (EVOH) copolymer/organo‐modified montmorillonite (OMMT) composites were investigated. Composites with two different percentages by weight of OMMT were prepared using a melt‐extrusion procedure in a twin‐screw extruder, using EVOH as matrix. Films made of EVOH and EVOH/OMMT composites were prepared in a cast‐film extrusion line. RESULTS: The mechanical properties were evaluated by tensile tests and the fracture behaviour was analysed using the essential‐work‐of‐fracture (EWF) method. Fracture characterization was carried out for the two main processing directions: melt flow direction and transverse direction. Fractographic observations were made using scanning electron microscopy. CONCLUSION: The tensile test results indicated good compatibility between EVOH and OMMT. In addition, the fracture tests showed the influence of the clay particle arrangement on the fracture behaviour, showing an increase in the specific essential work of fracture, w_e, which was attributed to the EVOH–OMMT interaction. The plastic term, βw_p, showed different trends depending on the test direction, explained by the size of the plastic zone and the restrictions to the EVOH plastic flow promoted by the clay particles. In this sense, the EWF method is shown to be a very useful tool for the analysis of structure–property relationships in polymer–organo‐clay composites. Copyright © 2009 Society of Chemical Industry