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91.
Poly (vinyl alcohol)/polylactic acid (PVA/PLA) blend film, which is environment friendly and has potential applications in food and electronic packaging fields, was fabricated by melt extrusion casting. Fourier transform infrared spectroscopy analysis confirmed the formation of the hydrogen bonding between PLA and PVA, which improved the compatibility of PLA with PVA, making PLA uniformly dispersed in PVA matrix as small spheres, even when PLA content increase to 15 wt%. In this way, the original hydrogen bond network among PVA was disturbed and the chain mobility of PVA was activated, endowing PVA/PLA blends with lower melt viscosity than bot modified PVA and PLA, and the blend films with the increased crystallinity, mechanical property, and water resistance. Compared with PVA film, the crystallinity, tensile strength and Young's modulus of the blend film with 15 wt% PLA, respectively, increased by 15.1%, 9 and 51 MPa, and the water contact angle enlarged from 23° to 60°. 相似文献
92.
The compulsion to use bioplastics has increased significantly today. One of the important aspects of plastics is their recyclability. Therefore, the important question of this research is that although bio-based compounds containing starch are sensitive to thermal-mechanical recycling processes, are such products thermally recyclable? To answer the question, polypropylene (PP)/thermoplastic starch (TPS) compound granules were extruded up to five times, and in the other part, single-extruded granules were blended at different ratios with virgin granules by extrusion. In order to characterize these samples, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, rotational disc rheometry, tensile properties, and appearance evaluation were used. The results showed that it is possible to recycle PP/TPS granules up to four times repetition of the extrusion operation and the fifth repetition also showed slight changes. There was also a blend of single-extruded granules with virgin material up to a 50:50% composition without significant variation. 相似文献
93.
There has been the expectation that polymers filled with small concentrations of nanosized particles will exhibit superior thermomechanical properties. We demonstrate that dispersing parts-per-million (ppm) polyhedral oligomeric silsesquioxane (POSS) nanochemicals by melt extrusion with polyolefins increased the tensile Young's modulus, yield stress, and toughness of blow molded and extruded films without penalizing extensibility, which is common to polymers reinforced with nano/microparticles. Transmission electron microscopy showed that the key to mechanical reinforcement is the spatial distribution of POSS at ca. single nanocage thus enabling interspersion of the macromolecular network. The thermal stability, water contact angle, and oxygen transmission of the films were also enhanced enabling a single component food package capable to keep food without decay for two weeks. The physical properties are improved when the nanoparticle size <D> is about the size of the virtual tube diameter dt, that is, <D>/dt ≈ 1. The enhancement of physical properties by placing the nanoparticle in the free space of the molecular network is a new paradigm in engineering polymer nanocomposites and opens opportunities for recyclable single component packaging films and tunable lightweight engineering and biomimetic materials. 相似文献
94.
Jing He Stephanie S. Lee Manuk Colakyan Dilhan M. Kalyon 《Polymer Engineering and Science》2021,61(4):1150-1165
Processing of concentrated lignocellulosic biomass suspensions typically involves the conversion of the cellulose into sugars and sugars into ethanol. Biomass is usually pretreated via methods like comminution or steam explosion to form fine cellulosic fibers to be dispersed into an aqueous phase for further treatment. The resulting cellulose suspensions need to be pressurized and pumped into and out of various processing vessels without allowing the development of flow instabilities that are typically associated with “demixing”, that is, the segregation of the cellulosic biomass from the aqueous phase via the formation of mats of cellulosic fibers and the filtration of the aqueous phase. Such demixing can prevent continuous processing at high rates. Here, the development of flow instabilities via the demixing effect for cellulose suspensions is demonstrated using capillary and compressive squeeze flows. It is shown that the use of a gelation agent, hydroxypropyl guar gum, at the critical concentration of 0.5 wt% or higher significantly affects the viscoelastic material functions of cellulosic suspensions, improves the dispersive mixing of the fibers within the aqueous phase, and results in the elimination of the flow instabilities and associated demixing effects that are ubiquitously observed during the pressurization and processing of cellulosic suspensions. 相似文献
95.
Sascha Stanic Thomas Koch Klaus Schmid Simone Knaus Vasiliki-Maria Archodoulaki 《应用聚合物科学杂志》2021,138(28):50659
The influence of two peroxides (peroxydicarbonate/dilauroyl peroxide) with various concentrations (10–200 mmol/kg PP) and their effective opportunity to introduce long chain branched (LCB) were investigated. The dependence of a single and double extrusion step and the changes of the properties were studied. Experiments were carried out in a single screw extruder at 180°C for the first extrusion step (modification) and at 240°C for the second extrusion step (processing simulation). Melt flow rate and dynamic rheological properties were studied at a measuring temperature of 230°C. For the definitive determination of long chain branched polypropylene (LCB-PP) served the extensional rheology measurements. The mechanical properties were examined via tensile test and impact tensile test. Summarized, LCB (melt strength) could be observed via extensional rheology for all modified specimens and the mechanical properties were maintained or even improved for the modified samples. Particularly, samples containing dilauroyl peroxide display excellent mechanical properties in this study. 相似文献
96.
液态挤压过程变形特征研究 总被引:7,自引:1,他引:7
液态挤压是近几年开发的融液态模锻和热挤压为一体的全新金属成形工艺,本文对其凝固过程、受力状态、变形特征进行了分析,探讨了液态挤压制件的微观组织形貌及正常和非正常组织的成因,在此基础上,对液态挤压的成形规律性问题及保证过程稳定进行的条件提出了独到见解。 相似文献
97.
对Φ100mm自动轧管机组穿孔方头缺陷产生的原因进行了分析。方头的形成是由顶杆位置过后,轧辊径向颤动及穿孔变形时椭圆度系数过大等原因造成的。同时提出了相应的解决方法。 相似文献
98.
99.
采用液态挤压代替压力铸造生产铝合金高压缸,不仅克服了压铸件内部易形成气孔和氧化夹杂物的缺陷,而且提高了成品率,降低了产品成本,在分析了高压缸液态挤压成形过程的基础上,提出了成形压力计算的简化模型,并采用变形功法推导了成形压力计算公式,得到了适合实际应用的结果。 相似文献
100.