乙酸-乙酸乙烯酯橡胶/聚乳酸共混体系的发泡及阻尼性能

以乙烯-乙酸乙烯酯橡胶(EVM)/聚乳酸(PLA)共混物为基体材料,过氧化二异丙苯(DCP)为硫化剂、偶氮二甲酰胺(AC)为发泡剂,经模压发泡制备橡塑共混发泡材料,用扫描电子显微镜观察材料的泡孔结构及泡孔尺寸分布,采用动态黏弹谱仪对发泡材料的阻尼性能进行研究,考察了AC和DCP用量、发泡时间及白炭黑用量对EVM/PLA发泡材料泡孔结构及阻尼性能的影响。结果表明,随着AC用量的增加,材料的泡孔数目增多但孔径相差不大,阻尼性能也无明显变化,在AC用量为4份时材料的阻尼性能较好;随着DCP用量的增加,材料的泡孔尺寸略有减小,阻尼性能变化不大,DCP用量为5份时材料的阻尼性能较好;随着发泡时间的延长,泡孔尺寸逐渐减小,阻尼性能逐渐提高,发泡时间为5 min时,泡孔孔径与损耗因子均出现突变;填料用量增加,泡孔孔径减小,发泡材料整体损耗因子上升。     

Improving the properties of polylactic acid by blending with low molecular weight polylactic acid‐g‐natural rubber

The low molecular weight (M_w) polylactic acid‐g‐natural rubber (PLA‐g‐NR) was synthesized by grafting the maleated natural rubber (MNR) with low molecular weight PLA at a weight ratio of 1:1 in toluene at 80°C. Two types of MNR (MNR10 and MNR20) having anhydride moieties of 10 and 20 wt%, respectively, were prepared. The reaction was followed by IR analysis. Next, the obtained PLA‐g‐NR was blended with pristine PLA using a twin‐screw extruder at PLA to PLA‐g‐NR weight ratios of 90:10, 80:20, 70:30, and 60:40 followed by compression to obtain specimens for testing. In case of 10 wt% PLA‐g‐NR having MNR10, it was found that blending of PLA with PLA‐g‐NR resulted in a 200% improvement in impact strength and twofold percent elongation at break (flexibility). Further SEM analysis confirmed that PLA‐g‐NR was compatible with PLA matrix. In contrast, NR was present as disperse particles which exhibited poor adhesion to PLA. From these findings, it was also found that PLA‐g‐NR was capable of improving the properties of PLA more than NR due to the fact that it exhibited higher compatibility. POLYM. ENG. SCI., 54:2770–2776, 2014. © 2013 Society of Plastics Engineers     

Improving the ductility of polylactic acid parts produced by fused deposition modeling through polyhydroxyalkanoate additions

Polylactic acid (PLA) is one of the most commonly used materials for fused deposition modeling (FDM) due to its low cost, biocompatibility, and desirable printing characteristics. However, its low ductility is a major disadvantage for engineering applications where high damage tolerance is needed. This study investigates the feasibility of polyhydroxyalkanoate (PHA) additions to PLA for improving the ductility of parts produced by FDM. Thermal and mechanical behavior of PLA/PHA specimens containing 12 wt % PHA is investigated for a range of printing nozzle temperatures. All PLA/PHA specimens exhibit amorphous PLA phase with semicrystalline PHA and possess outstanding ductility exceeding 160% for nozzle temperatures in the range of 200 °C–240 °C. Lower and higher nozzle temperatures result in low ductility, similar to that of pure PLA. Overall, PLA/PHA is a very promising polymer blend for FDM processes, providing a combination of sufficient strength with excellent damage tolerance. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48154.     

超支化多元醇对乙烯-乙酸乙烯酯橡胶/聚乳酸共混发泡材料性能的影响

选用乙烯-乙酸乙烯酯橡胶（EVM 700）和聚乳酸作为基质材料,以过氧化二异丙苯为交联体系、偶氮二甲酰胺为发泡剂,并添加超支化多元醇,经模压发泡制备出橡塑共混发泡材料,研究了多元醇对发泡材料发泡性能及阻尼性能的影响。结果表明,加入多元醇后体系中的小泡孔长大,材料的泡孔由大小孔穿插的结构变为大小相对均匀的结构;发泡材料的有效阻尼温域拓宽,其中偶氮二甲酰胺用量为4份（质量）时材料的阻尼温域较宽（78.1℃）;发泡材料的压缩强度减小,发泡后的密度减小,发泡倍率增大。     

Improving the properties of ceramic foams by a vacuum infiltration process

Reticulated ceramic foams are widely used for industrial applications such as metal filtration, exhaust gas and air purification, catalyst support and others. In this work, the compression strength and specific surface area of reticulated foams have been improved, while at the same time maintaining a high level of permeability in the final foam structure. In particular, a vacuum infiltration step by using a suitable slurry, followed by a pre-sintering cycle was adopted for filling up the hollow struts, generated due to the burnout of the PU foam. Furthermore, various mixtures of fine and coarse-grained alumina as well as in combination with zirconia, were utilised with the aim of controlling the foam properties such as compression strength, specific surface area and permeability. The compression strength was improved by a factor of two for alumina foams by infiltrating the hollow struts, and by a factor of four when infiltrating the struts of ZTA foams, with the composition 70 mol% Al₂O₃ and 30 mol% ZrO₂. The weight gain resulting from the vacuum infiltration process was in the order of 10 wt%.     

High-toughening modification of polylactic acid by long-chain hyperbranched polymers

The hyperbranched polyester synthesized by “one-step method” was grafted with stearic acid to obtain long-chain hyperbranched polymers (LCHBPs) with a large number of long stearic acid chains at the end. By means of FTIR and ¹³C-NMR characterization, it was proved that stearic acids were grafted onto hyperbranched polyesters (HBPE) to yield LCHBPs successfully. It was determined by GPC and hydroxyl value titration that the number average molecular weight of HBPE was 4.86 × 10³ and the grafting rate of stearic acid was 47%. Polylactic acid (PLA)/LCHBPs blends were prepared by melt processing method. The results showed that comparing with neat PLA, the tensile strength of PLA/LCHBPs blends decreased slightly with the increase of LCHBPs, but still maintained a high level, while the elongation at break and the impact strength of the PLA with 3.0 phr LCHBPs were greatly improved by 1360.0% and 119.8%, respectively. In addition, the impacted fracture characteristics of PLA changed significantly from brittle fracture to ductile fracture after LCHBPs incorporation, with the formation of a large number of filamentous structures. Thus, LCHBPs was an excellent toughening modifier for PLA and the resulting blends with improved performance possess wider applications.     

An overview of toughening polylactic acid by an elastomer

Due to environmental concern and depletion of fossil fuel, research on biopolymer is gaining interest among researchers. Polylactic acid (PLA) is produced from renewable resources. PLA has high tensile strength and high modulus, and it can be processed by using conventional processing methods. However, some properties of PLA limit the usage, such as brittleness, low impact resistance, low thermal stability, and high cost. Overall, the toughening approach of PLA, blending with elastomer has been one of the main focuses. This review paper is intended to provide general information regarding progress made in PLA toughening by an elastomer.     

聚乳酸微球的制备

以L-乳酸为原料,锡粒为催化剂,实现了丙交酯的开环聚合反应,红外光谱结果表明,合成了分子量可控的聚乳酸。以二氯甲烷为溶剂,聚乙烯醇为表面活性剂,制备了聚乳酸微球,研究了聚乙烯醇浓度对聚乳酸微球的影响。结果表明,当聚乙烯醇浓度增加时,微球半径变小,但粒径分布均匀度下降,聚乙烯醇浓度为1%时,聚乳酸成球效果较好。     

聚乳酸的间接合成研究

以D,L乳酸为原料、ZnO为催化剂,制备中间体丙交酯;再以丙交酯为原料、ZnO为催化剂,开环制得了较高相对分子质量的聚乳酸。用红外光谱仪(IR)对丙交酯及聚乳酸进行了表征,并讨论了影响丙交酯产率、聚乳酸相对分子质量的主要因素。得出在压力1.7×104Pa、催化剂质量分数为2.2%的条件下,两步脱水后制得的丙交酯经多次纯化后,其最大产率可达31%。在压力1.7×104Pa、催化剂质量分数0.06%时,可得到相对分子质量为1.1×105的聚乳酸。     

聚乳酸的热降解性能研究

研究了聚乳酸(PLA)在10-40 min和170-200℃的条件下热降解后的特性粘数和端羧基含量的变化。结果表明,在一定温度下,PLA熔体特性粘数随熔融时间的延长而下降,在一定时间下,随熔融温度升高而下降,端羧基含量随熔融温度升高而增大,在PLA成型加工中,应严格控制加工温度。     

聚乳酸合成工艺研究

以乳酸单体为原料,采用直接缩聚法合成了具有较高粘均分子质量的聚乳酸。研究了催化剂种类、用量、反应时间、真空度因素对聚乳酸粘均分子质量的影响。结果表明,聚乳酸合成的最佳工艺条件为:选取辛酸亚锡为催化剂,催化剂用量为乳酸量0.5%,氮气气氛,反应温度170℃,真空度30 Pa,反应时间10 h。     

聚乳酸的合成和应用

作为新型环保材料,聚乳酸的应用日益受到人们的重视。简要介绍了聚乳酸的合成方法和应用领域,提出合成中亟待解决的问题,对其未来的发展作了展望。     

聚乳酸直接合成的研究

综述了近年来国内外研究聚乳酸直接合成的进展情况,概述了乳酸直接合成的几种方法,研究了熔融聚合、溶液聚合中影响聚乳酸相对分子质量的因素,探讨了固相聚合机理。     

Preparation of multifunctional silicon-phosphorus acrylate particles for the simultaneous improvement of the flame retardancy and mechanical performance of polylactic acid

Polylactic acid (PLA) is a biodegradable plastic that currently has limited application owing to its poor fire resistance and brittleness. Herein, a multifunctional silicon-phosphorus acrylic resin(P/Si-ACR) is designed to endow both flame retardancy and toughness to PLA. P/Si-ACR is prepared by seeded emulsion polymerization with polysiloxane as the core layer and diethyl methylphosphonate acrylate and 9, 10-dihydro-9-oxa-10-phosphophenanthrene-10-oxide acrylate as the shell materials. P/Si-ACR has a particle size of approximately 200 nm and glass transition temperatures of −38 and 152°C for the core and shell layers, respectively. Addition of 7 wt% P/Si-ACR to PLA increases the notched impact strength and elongation at break by 124% and 46%, respectively. This improved mechanical performance is due to the elasticity of silicone rubber and the promotion of crystallization by P/Si-ACR. Combustion testing revealed that the limiting oxygen index increases from 19.1% to 22.5%, while the peak heat release rate decreases by 36%. This enhanced flame retardancy is due to the synergistic effect of phosphorus and silicon, with the former promoting graphitization and inhibiting the free radical degradation of PLA, and the latter stabilizing the char residue. Therefore, P/Si-ACR is a promising multifunctional modifier that can achieve an optimal balance among flame retardancy, crystallization performance, and toughness in polymers.     

功能化纳米羟基磷灰石改性聚乳酸复合材料的研究

采用硬脂酸对纳米羟基磷灰石进行表面改性,通过溶液共混和熔融挤出法制备纳米羟基磷灰石/聚乳酸复合材料。研究发现,改性后纳米羟基磷灰石在复合材料中的分散效果明显改善,同时与未改性的纳米羟基磷灰石/聚乳酸复合材料相比,改性后复合材料的一些力学性能有所提高。     

功能化纳米羟基磷灰石改性聚乳酸复合材料的研究

采用硬脂酸对纳米羟基磷灰石进行表面改性,通过溶液共混和熔融挤出法制备纳米羟基磷灰石/聚乳酸复合材料。研究发现,改性后纳米羟基磷灰石在复合材料中的分散效果明显改善,同时与未改性的纳米羟基磷灰石/聚乳酸复合材料相比,改性后复合材料的一些力学性能有所提高。     

Effect of temperature on stability of adsorbed inhibitors on steel in phosphoric acid solution

Rates of steel dissolution in 35% H₃PO₄/6% butanol (test solution) in the presence of thiosemicarbazide and seven of its derivatives were determined by spectrophotometry, weight loss and potentiodynamic and impedance techniques in the temperature range 303 to 333 K. At all temperatures, the corrosion rate decreased with increasing inhibitor concentration. Increasing temperature decreased the protection efficiency particularly at concentrations less than 2.5 × 10^–4 M. At inhibitor concentrations above 2.5 × 10^–4 M, increasing the temperature did not affect efficiency. Potentiodynamic polarization measurements indicated that the inhibitors have a strong effect on the corrosion behavior of the steel and behave as mixed type inhibitors. Thermodynamic functions obtained from this study indicate that the presence of the inhibitors increase the activation energy. The negative values of G ^* indicated spontaneous adsorption on the metal surface. A kinetic-thermodynamic model was found to describe the experimental well data at different temperatures.     

Influence of structure of hydroxyl-terminated maleopimaric acid ester on thermal stability of rigid polyurethane foams

A series of hydroxyl-terminated maleopimaric acid esters (HTMAEs) and rigid polyurethane (PU) foams based on these HTMAEs were synthesized using chemically modified natural gum rosin and its derivative maleopimaric acid as raw materials. Thermal stability of these polyols and their corresponding rigid PU foams was studied by a thermogravimetric method and a dimensional stability measurement. It was shown that the thermal stability of the final foams was strongly dependent on the structure of their corresponding polyols. The thermogravimetric analysis curves of these rosin-based rigid PU foams displayed two distinct regions of weight loss. It has been shown that at the initial stage of weight loss the process was dominated by polyol component degradation; the second stage was governed by isocyanate component degradation. © 1995 John Wiley & Sons, Inc.     

Effect of coupling agent on polylactic acid/polypropylene and polylactic acid/polyamide 6 foam composites

The main part of polymer materials generated from fossil fuels do not degrade after completing their usage life and then begin to be waste in the environment. This situation has led to the emphasis on environmentally friendly, biodegradable, and bio-based polymers obtained from renewable sources as an alternative. In recent years, several studies are concentrated on especially lightweight and carbon dioxide (CO₂) emission limitations. In this work, the goal was to investigate at the same time environmentally friendly and lightweight polymer foam composites based on polylactic acid (PLA) polymer without lowering the performances of the materials. In this aim, polymer foam composites containing polypropylene (PP), polyamide 6 (PA6) and PLA were produced (PLA/PA6 (30:70) and PLA/PP (30:70)) with a chemical blowing agent (CBA) introduced at 1.5 wt.% to the polymer mixture. To improve the interpolymer compatibility and foaming activity maleic anhydride-grafted polylactic acid (PLA-g-MA) was utilized as coupling agent (CA) in different ratios (1, 3 and 5 wt.%). From the evaluation of the polymer mixtures in terms of their lightness, thermal and mechanical strength, the most appropriate CA ratios were determined as 1 wt.% for foamed PLA/PP (30:70) mixtures and 3 wt.% for foamed PLA/PA6 (30:70) mixtures.