硅藻土填料对发泡聚氨酯复合材料吸声性能的影响

利用铝酸酯偶联剂对硅藻土进行表面改性,采用一步发泡法制备了聚氨酯(PUR)/硅藻土多孔复合材料,利用傅立叶变换红外光谱研究了铝酸酯偶联剂改性硅藻土的效果,分析了硅藻土粒径和添加量对PUR复合材料组织、力学性能和吸声性能的影响。结果表明,在研究范围内,硅藻土粒径增加,压缩强度先减小后增加,峰值吸声系数增加,峰值吸声频率向高频移动;硅藻土含量增加,压缩强度略有降低,峰值吸声系数增加,峰值吸声频率向低频移动;而对于经铝酸酯偶联剂改性的硅藻土,当其含量为60份,粒径为5μm时,其吸声性能更好,吸声系数峰值达到0.94,对应频率为1000 Hz。     

汽车顶棚用热塑性半硬质聚氨酯泡沫的吸声性能研究

通过驻波管传递函数法测试了不同条件下汽车顶棚用热塑性半硬质聚氨酯泡沫的吸声性能。研究结果表明:泡沫吸声系数随密度增加而提高;泡沫厚度对中低频区吸声性能影响较大,吸声系数随厚度增加而提高;高异氰酸酯指数情况下泡沫吸声性能较好;硅藻土的引入可有效提高泡沫的吸声性能;高回弹聚氨酯泡沫与半硬质聚氨酯泡沫复合且高回弹聚氨酯泡沫为吸声面时吸声效果较好。     

EVA发泡材料吸声性能研究

借助阻抗管法测试了自制的EVA(乙烯–醋酸乙烯共聚物)泡沫材料的吸声系数,探讨了影响EVA泡沫吸声性能的因素。结果表明:不同的发泡温度下,EVA泡沫的吸声系数不同,其中180℃下发泡的材料吸声性能最佳;泡沫的吸声系数随泡沫厚度的增加而增加,但超过30 mm后吸声系数趋于平稳;连续通孔结构泡沫的吸声性能要显著优于闭孔泡沫的;材料的吸声系数随测试样片直径增加呈现先增加后减小的变化趋势。     

EPR改性PVC泡沫材料吸声性能的研究

研究了EPR用量、发泡剂AC用量、泡沫材料厚度和发泡温度等因素对EPR改性PVC泡沫材料吸声性能的影响。结果表明,EPR可显改善PVC泡沫材料吸声性能,随着EPR用量的增大,泡沫材料低频吸声性能得到显提高,而高频吸声性能略有下降;发泡剂AC用量的增大可明显改善泡沫材料的中高频吸声性能,低频吸声性能有所降低;材料厚度的增大可提高全频段吸声性能,低频吸声性能的提高更为显;随着发泡温度的升高,低频吸声性能提高,中高频吸声性能则有所下降。     

橡胶改性PP阻燃泡沫材料吸声性能的研究

研究了ＥＰＲ改性ＰＰ阻燃泡沫材料的吸声特性，探讨了ＥＰＲ、交联剂、发泡剂用量及泡沫材料厚度和材料背后空腔厚度对其吸声性能的影响。结果表明，当交联剂用量为０６７份时，泡沫材料最大吸声系数为０９４；随着泡沫材料厚度和背后空腔厚度的增大，吸声性能有所提高，且最大吸声系数特征频率向低频区域移动。     

PP／EPR基阻燃泡沫材料的动态力学性能及声学性能研究

以ＰＰ／ＥＰＲ为基体，加入发泡剂和阻燃剂，制得阻燃泡沫材料。动态力学实验表明，乙丙橡胶可有效提高泡沫材料的力学损耗值。用驻波管法测试了材料的吸声系数，结果表明：泡沫材料具有良好的吸声性能，在合适的ＥＰＲ含量范围内，随ＥＰＲ质量分数增加，材料的吸声系数提高，超过２０％后，材料的交联发泡工艺难以控制，泡孔分布不均匀，孔隙率降低，吸声性能反而下降。     

碱矿渣泡沫混凝土的吸声性能试验研究

为了研究开发一种新型的绿色低碳吸声材料,以化学发泡法制备碱矿渣泡沫混凝土试样,通过实验分析了材料容重、碱当量和纤维掺量对碱矿渣泡沫混凝土的抗压强度、吸水率、吸声性能的影响.结果表明:随着容重的增加,材料的抗压强度提高,吸水率下降,低频吸声性能提高,而高频吸声性能下降;随着碱当量的提高,材料的抗压强度提高,吸水率先降低后提高,在50Hz到1600Hz频段内的吸声系数有一定提高;适宜掺量的纤维会提高材料的抗压强度,掺入过多对强度发展不利,同时纤维的掺入会提高材料的高频吸声性能.     

EVA发泡材料吸声性能的研究

通过模压发泡法制备乙烯-醋酸乙烯共聚物(EVA)发泡材料。运用多孔材料吸声机制分析材料孔隙率及空腔厚度对吸声性能的影响。结果表明,孔隙率及空腔厚度对发泡材料吸声性能影响显著;当孔隙率为79.6%时,材料在高频区域内有较好的吸声性能,吸声系数及降噪系数分别为0.249、0.105;随着空腔厚度增加,材料的声波第一共振频率向低频方向移动且提高了吸声性能,当空腔厚度为10mm时,发泡材料的吸声性能较好,吸声系数和降噪系数分别为0.638、0.265。     

承压条件下声子晶体吸声性能研究

声子晶体是一种新的吸声材料,研究了局域共振单元包覆层模量、厚度以及橡胶基体模量对声子晶体共振吸声频率、吸声系数的影响规律。在常压及承压条件下,包覆层模量越高,厚度越小,共振吸声频率越高,其规律符合共振频率与包覆层模量、厚度之间的关系。随着压力的增加,声子晶体的共振吸声频率均向高频移动。承压条件下,包覆层模量较低的样品低频吸声系数略高。包覆层厚度为2mm的样品,常压及承压条件下低频吸声系数数值变化较小。基体橡胶模量对声子晶体吸声频率和吸声系数未见明显影响。     

橡胶薄片共振结构吸声机理及性能研究

本文用驻波管法研究了橡胶薄片共振吸声结构的吸声机理及橡胶薄片厚度、空气层厚度和声波频率对其吸声性能的影响。实验结果表明,橡胶薄片共振结构与普通板共振结构在吸声机理和吸声效果方面均有所不同,前者的吸声效果优于后者;在共振状态,前者的吸声作用主要在于柔性橡胶薄片在声波作用下弹性振动,引起后面腔体内空气压强的变化,因空气层的吸声作用而损耗声能,后者主要依赖于板的内摩擦吸声作用。橡胶薄片共振的吸声系数随空气层厚度的变化而出现一极大值,随着声波频率的增加,达到共振状态所需的空气层厚度减小,随着橡胶薄片厚度的增大,其最大吸收峰向低频方向移动。     

Design of ethylene-propylene-diene monomer foam and its double-layer composite for improving sound absorption properties via experimental method and theoretical verification

In this work, the ethylene-propylene-diene monomer (EPDM) foam was fabricated via 4-4′-oxobisbenzenesulfonyl hydrazide (OBSH) and phenolic resin (PF) in an effort to prepare the sound-absorbing composite which has excellent sound absorption at the medium and low frequency. For single-layer EPDM foams, cell morphology showed a certain pattern, causing the peak of the sound absorption coefficient move to a higher frequency and the peak value reached a maximum of about 0.75 as the OBSH content increased. In addition, with the foaming temperature increasing, the cell morphology had a different tendency and the peak of the sound absorption coefficient moved first to the higher frequency and then to the lower frequency due to the vulcanization reaction. Compared with the single-layer EPDM foams, the sound absorption curve of the double-layer composite made of the single-layer EPDM foam and pure EPDM sheet with cavities moved to a lower frequency by about 400 Hz. The theoretical calculation method was used to verify the accuracy of the experimental results. This work provided a simple approach to control the sound absorption property of EPDM foamed material and its double-layer composite through from an experimental and theoretical perspective.     

不同含量配比制备聚氨酯泡沫及其性能研究

采用一步法以异佛尔酮二异氰酸酯和聚醚多元醇为原料,选用A～D4种配比制备了聚氨酯泡沫材料,通过红外光谱仪、扫描电子显微镜、差示扫描量热仪、热重分析仪和噪声振动测试系统等对聚氨酯泡沫的泡孔结构、热稳定性及吸音隔音性能进行了测试.结果表明,聚醚多元醇的用量对聚氨酯泡沫成分未造成差异,聚氨酯泡沫中出现闭孔、半闭孔、开孔并存现...     

聚酰亚胺泡沫材料吸声性能对比研究

通过阻抗管法研究了聚酰亚胺(PI)、三聚氰胺(MFF)和聚氨酯(PU)3种泡沫材料对声音的吸收特性。结果表明:与MFF和PU泡沫材料相比,PI泡沫材料具有优异的吸声降噪性能;随着材料密度的增大,3种泡沫的吸声降噪性能都有相应提高。     

Sound absorption properties of polyurethane/nano‐silica nanocomposite foams

In this study, polyurethane (PU)/nano‐silica nancomposite foams were prepared. The effects of isocyanate index, cell size, density, and molecular weight of polyols on the sound absorption ratio of PU/nano‐silica foams were investigated. With increasing nano‐silica content, the sound absorption ratio of PU/nano‐silica foams increases over the entire frequency range investigated in this study. Decrease of isocyanate index, cell size, and increase of density leads to the increase of sound absorption ratio of PU/nano‐silica foams. PU/nano‐silica foams have a broad T_g centered around room temperature by decreasing molecular weight of polyol resulting in good sound absorbing ability. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Acoustic properties of cellular vitreous carbon foams

The present work deals with acoustic properties of highly porous rigid foams derived from flavonoid tannins. Such cellular solids derived from renewable resources were investigated before and after pyrolysis, the latter leading to cellular, vitreous, carbon foams. It is demonstrated here that these lightweight materials have a high air flow resistivity, which depends on the density of the foam. Vitreous carbon foams, especially, have rather low performances for sound absorption. Using a simple model, their sound absorption coefficients were predicted and found to be in very good agreement with measurements in all the investigated frequency range, 50–4300 Hz. However, we have shown that carbon foams are very appropriate materials to apply the double porosity concept since they can produce a high permeability contrast. This paper shows how vitreous carbon foams can become excellent sound-absorbing materials in a targeted frequency range by using the double porosity concept.     

Enhanced airborne sound absorption effect in poly(vinylidene fluoride)/(K0.5Na0.5)NbO3-nanofiber composite foams

Introducing electrical conductive function to discharge local piezoelectric effect is found effective for improving airborne sound absorption performance. In this work, instead of conductive fillers, a composite with two piezoelectric materials with opposite piezoelectric responses was explored aiming at enhanced sound absorption effect. Open-cell poly(vinylidene fluoride)/(K_0.5Na_0.5)NbO₃ (PVDF/KNN)-nanofiber composite foams were proposed and investigated for airborne sound absorption purpose. Structural and thermal analyses showed that the KNN nanofibers were well dispersed in the PVDF matrix and enhanced the degree of crystallinity of polar phase of PVDF. Significantly enhanced airborne sound absorption over a broad frequency range was observed in the PVDF/KNN-nanofiber composite foams, with increasing KNN nanofibers. One possible mechanism for the improved sound absorption with the piezoelectric KNN nanofibers with positive piezoelectric coefficient added in the PVDF matrix with negative piezoelectric coefficient is that electrical discharge could be facilitated for energy dissipation with the opposite charges generated through the piezoelectric effects in the two phases with opposite polarity. The experimental results show that the open-cell PVDF/KNN-nanofiber composite foams are promising for broadband airborne sound absorption application, and our analysis shed a light on the strategy in designing piezoelectric composite foam with high sound absorption performance.     

Sound absorption performance of a lightweight ceramic foam

Porous materials can be effective for sound absorption and noise reduction. A kind of lightweight cellular ceramic foam with bulk density of 0.38–0.56 g cm^-3 was successfully prepared by conventional molding with pore forming agent. The porosity is from 76.4% to 83.7% for the sample with relatively large pores (the average pore size: 5.3–5.6 mm), and from 74.1% to 81.1% for the sample with relatively small pores (the average pore size: 1.5–1.7 mm). The effects were investigated for processing parameters on the structure of samples, and for the pore size, sample thickness and porosity on the sound absorption performance of samples. The results show that the absorption performance of the ceramic foam product with relatively large pores may be superior to that with relatively small pores in the case of the approximately same porosity. The first absorption peak moves from a higher frequency to a lower frequency with the increase of sample thickness. When the porosity increases, the average sound absorption coefficient increases for all of the samples, and the first absorption peak moves from a higher frequency to a lower frequency for the sample with relatively large pores but does not change for that with relatively small pores.     

Development,characterization, and modeling of environmentally friendly open‐cell acoustic foams

This study shows the development of new polymeric open‐cell foams from polypropylene (PP) and polylactide (PLA) resins with a focus on sound absorption properties and modeling of these foams. The objective is to develop new environmentally friendly foams to replace the existing non‐recyclable Polyurethane foams are currently used for sound insulation in industry. Through this research, open‐cell foams of about 90% porosity were fabricated from PP and PLA. These resins were selected since PP is a recyclable thermoplastic polymer, and PLA is a bio‐based thermoplastic polymer made from renewable resources. Polyurethane (PU) foam which is currently used for sound absorption and noise control in industry was compared to the fabricated PP and PLA foams. As the first attempt to fabricate environmentally friendly acoustic foams, the resulting foam structures show improved properties as compared to the existing materials. The average absorption of PP and PLA foams fabricated is in the range of 0.42–0.55 which is comparable or even higher than the average absorption of PU foam. To better understand the effect of structural and material properties on sound absorption and further improve the acoustic performance of bio‐based foams, an analytical model based on Johnson–Champoux–Allard model was used to numerically simulate the acoustic performance of foams under study. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers     

Mechanical and acoustic performance of compression‐molded open‐cell polypropylene foams

Open‐cell materials are lightweight and multifunctional capable of absorbing acoustic energy and supporting mechanical load. The acoustic and mechanical performance of open‐cell materials can be optimized through processing. In this article, the relationships between processing parameters and acoustic and mechanical performance are shown for polypropylene (PP) foams. PP foam samples are fabricated using a combined compression molding and particulate leaching process. The results from a parametric study showed that both salt size and salt to polymer ratio affect the acoustic and mechanical performance of open‐cell PP foams. As salt size increases, cell size increased and cell density decreased. The salt to polymer ratio had opposite affect on cell density, and increasing the salt to polymer mass ratio increased the open‐cell content. The airflow resistivity decreased significantly by increasing the cell size, which means that foam samples with smaller cell size have better sound absorption. When foam samples were thin, smaller cell sizes produced better sound absorption; however, as thickness of the sample increases, medium cell size offered the best acoustic performance. The compressive strength of the foams was increased by increasing the relative density. Acoustic performance results from the parametric study were compared to the Johnson‐Allard model with good agreement. Finally, optimal cellular morphologies for acoustic absorption and mechanical performance were identified. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010