高温后合成纤维混凝土的强度试验研究

研究了普通混凝土(NC)、聚丙烯纤维混凝土(PPFRC)和聚丙烯腈纤维混凝土(PANFRC)在常温及300,600,1000℃高温后的抗压强度和抗折强度,分析了高温加热方式及加载条件不同的影响。研究表明,300℃高温下混凝土的劣化主要受升温速率的影响;600℃以上高温下混凝土的劣化主要受温度的影响。掺入低掺量的PP纤维和PAN纤维可缓解混凝土的高温劣化,从而提高高温后混凝土的抗压强度和背火面加载时的抗折强度。     

Evaluation and verification of the virgin–recycled mixing ratio of polypropylene plastic

This study has analyzed the properties of blended polypropylene (PP) specimens and employed statistical analysis to develop a method for determining the virgin–recycled mixing ratio of a specimen. Morphological observations and analyses of thermal and mechanical properties were conducted to examine specimen properties. The results were incorporated into regression analysis to create relationship equations. The results revealed that the melt temperature ranged between 167 and 169 °C, melt index (MI) ranged between 7.59 and 18.36 g/10 min, viscosity decreased when the amount of recycled PP and the rotation speed increased, the maximum decomposition temperature decreased with an increase in recycled PP content and increased with the heating rate, activation energy (E_a) ranged between 39.91 and 12.07 kcal/mol, Young’s modulus ranged between 1121.1 and 1910.2 MPa, and impact strength ranged between 37.94and 49.41 J/m (no significant trends). Scanning electron microscopy showed unbroken fibrils distributed on the fracture surface of Specimens 1–3. Additionally, the tensile strain of these specimens was comparatively high. The fracture surfaces of the specimens showed favorable compatibility after undergoing impact tests. The results of regression analysis indicated that the mixing ratio achieved significant correlations with E_a, MI, and Young’s modulus. Thus, regression and multiple regression analysis were performed to create relationship equations.     

Nanotexturing and Wettability Ageing of Polypropylene Surfaces Modified by Oxygen Capacitively Coupled Radio Frequency Plasma

Polypropylene （PP） was treated by an oxygen capacitively coupled radio frequency plasma （CCP） under a radio frequency （RF） power of 200 W for exposure time of 1, 5, and 10 rain. The ageing process of the plasma- treated PP was studied at an ageing temperature of 90 ~C during an ageing time up to 25 h. The formation of the nanotextures with different geometry and aspect ratio and the grafting of large number of oxygen- containing groups were achieved on as-treated PP surfaces under the oxygen CCP treatment for the increased exposure time. The hydrophilicity on the as-treated PP surfaces with the stable nanotextures was rapidly depressed during the ageing process at 90 ℃ due to the restructuring of chemical composition. The surface restructuring rate was dependent on the aspect ratio and the oxygen-containing groups on the nanotextured PP with increasing exposure time. The hydrophobic over-recovery to high hydrophobicity and superhydrophobicity were observed on the post-aged surfaces with the stable nanofibrils from as-treated hydrophilic surfaces. The superhydrophobicity with the low water adhesion was achieved on the post-aged surfaces preserving the nanofibrils with high aspect ratio and large distance due to the decrease of the oxygen-containing groups after the surface restructuring.     

Effect of stick-slip on the scratch performance of polypropylene

For the scratch process of polypropylene (PP), the stick-slip phenomenon always exists and contributes to the observed periodic surface damage patterns. The stick-slip, one main cause for scratch visibility, alters the surface characteristics of substrate and eventually induces scratch visibility. Both ASTM/ISO and Erichsen scratch test methods are employed to study the stick-slip phenomenon and its effects on scratch behavior of PP. Image analysis shows that the stick-slip phenomenon was responsible for material removal and severe surface damage. Possible solutions to improve the scratch performance of polymeric materials are also discussed in this paper.     

不同炭源对膨胀阻燃聚丙烯力学性能的影响

采用聚磷酸铵(APP)、三聚氰胺(MEL)作为膨胀阻燃剂中的酸源及气源,聚丙烯接枝马来酸酐(PP-g-MAH)作为阻燃剂与聚丙烯的增容剂,研究了3种不同炭源(季戊四醇、淀粉、尼龙6)在阻燃剂中用量的变化对阻燃聚丙烯力学性能的影响。     

Development of Structure and Properties during Spunbonding of Metallocene Catalyzed Polypropylene

Spunbonding is one of the most widely used processing techniques to convert polymers into nonwoven fabrics. metallocene-catalyzed polypropylene is becoming more and more important. A study was carried out to understand the development of structure and properties of a metallocene-catalyzed isotactic polypropylene during spunbonding. This research was conducted using the Reicofil spunbond line at the University of Tennessee, Knoxville. The filaments at three different throughput rates were studied for tensile properties and for structural features by birefringence, X-ray diffraction, and thermal measurements. The fabrics produced at different process conditions were tested for various mechanical properties. The failure mechanism of the fabrics at different bonding temperatures was studied using the scanning electron microscope. The results are compared with a conventional polypropylene processed under similar conditions. The results showed that the mPP produced fabrics with better strength and elongation at comparable processing conditions. Also, failure mechanisms were found to be different for the fabrics produced from the two polymers, which are due to differences in the produced structures.     

Progress in Block Copolymers

Monodisperse proteins and polydisperse carbohydrates and polyenes occur in nature. The proteins are random copolymers, but no block or graft copolymers occur in nature.     

Effect of the surface modification of the synthetic meshes used in the surgical treatment of pelvic organ prolapse on the tissue adhesion and clinical functionality

Stress urinary incontinence and pelvic organ prolapse represent important conditions affecting adult women’s health. Lately, the properties and performance of the polymer materials used in the treatment of pelvic organ prolapse have been improved by modulating from their formula. Materials investigated in our study are polypropylene meshes used by clinicians in surgical treatment of urinary incontinence and utero-vaginal prolapse. In order to make a comparative analysis, we confronted the structure and surface morphology of native synthetic polypropylene meshes with explanted fragments from the same mesh type after clinical use. FTIR investigations revealed little change in structure after implantation, somehow insignificant. Scanning electron microscopy (SEM) demonstrates modification in surface morphology even just by passing through the transobturator passage, whereas after implantation the surface deteriorates. SEM on explanted meshes proves the encapsulation process of the mesh to be more similar to a foreign body reaction rather than to the adhesion and integration of the synthetic mesh into the organism. Histological analysis of the surrounding tissues near explanted mesh was made in some relevant clinical cases, because the tissue response is an important factor in order to evaluate the tissue adhesion at the polypropylene mesh surface. Based on our experiments and clinical experience we’ve designed an adhesion score. It applies to meshes used in pelvic organ prolapse surgery measuring the following important factors: tenacity, extent of adhesion, macroscopic and microscopic aspects and ease of dissection from surrounding tissues.     

聚丙烯无卤阻燃剂的研究进展

介绍了水合金属化合物、磷系阻燃剂、膨胀型阻燃剂等非卤系阻燃剂在聚丙烯中的应用情况,指出了聚丙烯阻燃剂的发展方向。     

NA在聚丙烯中的应用

研究成核剂对聚丙烯性能的影响,来提高聚丙烯的性能。通过添加成核剂来改变聚丙烯的晶型,目的是增加材料的弯曲性能,而冲击性能略有下降。