导热PE-LD复合材料的制备与性能研究

采用低密度聚乙烯(PE-LD)为基体材料,石墨、Al N为导热填充材料,通过双辊混炼、模压制备了导热复合材料,并对该复合材料的导热性能、力学性能、热行为进行了分析。结果表明,随着石墨或Al N含量的增加,PE-LD/石墨复合材料和PE-LD/Al N复合材料的热导率逐渐增大;PE-LD/石墨复合材料的热导率高于PE-LD/Al N复合材料的热导率。当石墨与Al N的总质量分数为50%、石墨与Al N的质量比为4∶1时,PE-LD/石墨/Al N复合材料的拉伸强度、弯曲强度均达到最大值,分别为12.8,17.15 MPa;此时PE-LD/石墨/Al N复合材料的热导率达到最大值,为0.618 W/(m·K),略低于添加质量分数50%的石墨时的PE-LD/石墨复合材料的热导率[0.634 W/(m·K)];当石墨与Al N质量比为1∶4时,PE-LD/石墨/Al N复合材料的热导率为0.488 W/(m·K),高于只添加质量分数50%Al N的PE-LD/Al N复合材料的热导率[0.410 W/(m·K)]。当石墨和Al N总质量分数为50%时,随着Al N含量的增加,PE-LD的结晶度增大。     

六方氮化硼/碳化硅晶须填充改性聚酰亚胺导热绝缘复合材料的制备及表征

采用固相共混方法将六方氮化硼(h-BN)和碳化硅晶须(SiCw)作为导热填料对单醚酐型聚酰亚胺(PI)模塑粉进行改性,然后通过热模压工艺制备PI导热绝缘复合模压材料,并对其性能进行表征。测试结果表明:h-BN可以有效提高模塑料导热性能、热性能和电绝缘性能,但会降低材料力学性能;SiCw可以有效提高复合材料导热性能、热性能和力学性能,但会显著降低电绝缘性能。将h-BN/SiCw复配使用,在显著提高复合材料导热性能和热性能的同时又可保持其良好的力学性能和电绝缘性能。添加30%(质量分数)h-BN/SiCw(3/1),复合材料导热系数提高至1.21 W/(m·K),是未改性PI材料的4.84倍,弯曲强度为142MPa,体积电阻率为1.27×10~(14)Ω·cm,线性热膨胀系数(CTE)显著降低为55.6μm/(m·℃)。     

聚丙烯/高密度聚乙烯/氮化硼导热复合材料的制备及性能研究

以聚丙烯（PP）/高密度聚乙烯（HDPE）共混物为基体，六方氮化硼（h-BN）为导热填料，聚丙烯接枝马来酸酐（PP-g-MAH）为相容剂，通过熔融共混法制备PP/HDPE/h-BN和PP/HDPE/h-BN/PP-g-MAH导热复合材料。采用导热系数仪、场发射扫描电镜、万能试验机、热分析仪等测试导热复合材料，研究不同含量的h-BN、PP-g-MAH对复合材料导热性、力学性能、结晶性能和耐热性的影响。结果表明：随着h-BN含量的增加，PP/HDPE/h-BN复合材料的弯曲强度、热导率和耐热性提高。当h-BN含量为20%，复合材料的弯曲强度达到41.02 MPa；当h-BN含量为25%，复合材料热导率达到0.372 1 W/（m·K）。h-BN对PP的结晶具有促进作用，提升PP的结晶速率和结晶温度。PP、HDPE与h-BN质量比为64∶16∶15时，添加5%的PP-g-MAH，增强了h-BN和基体材料的界面相容性，复合材料的弯曲强度达到42.72 MPa，拉伸强度达到26.64 MPa，热导率达到0.356 1 W/（m·K）。     

无机填料填充PE-LD/EVA合金的导热及阻燃性能

采用氧化铝（Al2O3）为导热填料、氢氧化镁［Mg(OH)2］为阻燃填料,以低密度聚乙烯（PE-LD）和乙烯醋酸乙烯共聚物（EVA）为基体树脂制备导热阻燃复合材料。通过导热性能测试、燃烧行为表征（极限氧指数和垂直燃烧测试）以及热重分析研究了PE LD/EVA/Al2O3/Mg(OH)2复合材料的导热性能、阻燃性能及热稳定性。结果表明,含有50份Al2O3及50份Mg(OH)2的复合材料,在PE-LD/EVA质量比为1/1时,热导率可达到1.21 W/m·K;材料的阻燃性能及热稳定性都随 EVA 含量的增加而增大,极限氧指数从27.0 % 提高到31.5 %,UL 94 垂直燃烧从无等级提高到V-0级,残炭率从46.5 %提高到57.7 %。     

纤维/气凝胶泡沫混凝土的制备与性能研究

气凝胶因具有低导热系数、高孔隙率、轻质等优异特性而备受关注,同时还具有高疏水性及良好的吸声和减震功能.实验以气凝胶为填充材料,玻璃纤维丝为增强体,制备了一种新型超轻质纤维/气凝胶泡沫混凝土.结果 表明:玻璃纤维的掺入促进了泡沫混凝土的成型,在超轻泡沫混凝土制备过程中起到至关重要的作用.当纤维含量为0.9％时,导热系数为0.058 W/(m·K),其密度为205 kg/m3,远低于普通泡沫混凝土的导热系数(0.08～0.25 W/(m· K))与密度(300～1600 kg/m3).抗压强度为0.32 MPa,符合泡沫混凝土标准JG/T 266-2011中A03级抗压强度的要求.     

不同石墨尺寸复配对NG/UHMWPE复合材料性能的影响

以粒径为6.5μm的单一尺寸鳞片石墨(NG)和粒径为6.5μm和1μm的混合尺寸鳞片石墨为填料,超高分子量聚乙烯(UHMWPE)为基体树脂,通过热处理粉末混合法制备了具有隔离结构的高导热NG/UHMWPE复合材料。研究了NG尺寸对高导热石墨/超高分子量聚乙烯复合材料微观结构、填料取向、导热性能和通路以及力学性能的影响。结果表明,混合尺寸石墨的加入提高了复合材料在垂直于热压方向和平行于热压方向两个方向上的导热系数,最高达到10.5 W/(m·K)和5.08 W/(m·K),相较于纯UHMWPE,导热系数分别提高了20.91倍和9.60倍。此外,当石墨含量一致时,混合尺寸填料的复合材料在保持机械性能不下降的情况下,导热系数更高。     

PDMS/SCF导热复合材料制备工艺对导热性能的影响

采用SCFNA法(即空间限域强制组装法),制备碳纤维质量分数为30%的PDMS/SCF复合材料,并探究了在制备PDMS/SCF导热复合材料过程中,基体与填料混合工艺以及压印过程中的温度对复合材料制品导热性能的影响。研究结果表明,在复合材料制品厚度不变的前提下,当混合转速为2 000 r/min时,随着混合时间由10 min缩短至2 min,复合材料制品的热导率由10.314 W/(m·K)提高至11.188 W/(m·K),提高了8.474%。当混合时间为3 min时,随着混合转速从2 500 r/min降低至1 500 r/min,复合材料制品的热导率由10.140 W/(m·K)提高至10.963 W/(m·K),提高了8.116%。对比不同压印温度对复合材料制品热导率的影响发现,当压印温度在120℃附近时,复合材料制品的导热性能最佳,热导率为11.188 W/(m·K)。控制混合转速、混合时间和压印温度这3个工艺条件能够有效地提高复合材料制品的导热性能。     

碳纳米管-膨胀石墨/环氧树脂复合材料的导热性能

在环氧树脂中添加多壁碳纳米管和膨胀石墨作为填料,以提高环氧树脂的导热性能. 结果表明,添加0.5wt%多壁碳纳米管时,环氧树脂的最佳导热系数为0.3448 W/(m?K),比不添加时提高30%;添加0.75wt%羧基改性多壁碳纳米管时,环氧树脂的最佳导热系数为0.3813 W/(m?K),比添不加时提高40%;同时添加多壁碳纳米管和膨胀石墨后,环氧树脂导热系数可进一步提高到0.4039 W/(m?K),表明在环氧树脂中添加混合填料,二者可在环氧树脂中形成有效的导热网络,能进一步提高聚合物的导热性能.     

高密度聚乙烯/石墨/碳纤维导热复合材料性能的研究

采用高密度聚乙烯(HDPE)、石墨、碳纤维制备高导热、高强度的复合材料。通过SEM照片考察高密度聚乙烯/石墨/碳纤维复合体系的微观结构;研究石墨及碳纤维的加入是否可以形成导热通道以及随着石墨的添加量的提高,复合材料的导热性能及其力学性能的变化。结果表明:当石墨的质量分数为60%,碳纤维的质量分数为5%时,复合材料的导热系数达到7.938 W/(m.K),是纯HDPE的20倍。     

聚丙烯/碳纤维/氮化硼导热绝缘复合材料的制备

研究聚丙烯(PP)/碳纤维(CF)/氮化硼(BN)复合材料的导热绝缘性能。结果表明,CF的含量达15%时,PP/CF复合材料的体积电阻率大幅度下降,出现逾渗现象;基于PP/CF(15%)填加不同含量的BN,当BN的含量达到20%。PP/CF/BN复合材料的热导率达0.939 5 W/(m·K),比纯PP提高近4倍,其体积电阻率为1.3×1014Ω·cm。     

PF泡沫塑料对PF/EPS复合泡沫塑料性能的影响

研究出一种具有较好稳定性、保温性能、力学性能和阻燃性能的酚醛树脂(PF)/可发性聚苯乙烯(EPS)复合泡沫塑料。在PF泡沫塑料颗粒基体中加入EPS发泡颗粒,充分混合固化,使PF泡沫塑料颗粒与EPS发泡颗粒紧密结合,EPS发泡颗粒被PF泡沫塑料颗粒包围并相互隔离,再用模具发泡成型得到该复合泡沫塑料。实验结果表明,PF的含量越高,稳定性、力学性能和阻燃性能越好,保温性能呈现先升高后下降的趋势,当PF的含量为80%时,PF/EPS复合泡沫塑料的表观密度为38.4 kg/m3,热导率为0.024 W/(m·K),弯曲强度为0.134 k Pa,压缩强度为323 k Pa,极限氧指数为47.9%,烟密度等级小于15,热释放速率峰值小于250 k W/m2,综合性能最好。     

硬质聚氨酯/二氧化硅纳米粒子复合材料泡沫形貌和性能研究

利用2种不同粒径的球形二氧化硅（SiO2）纳米粒子作为填料,制备了硬质聚氨酯（PU-R）/SiO2纳米粒子复合材料泡沫。利用扫描电子显微镜考察复合材料的形貌,通过压缩试验、尺寸稳定性测试和热导率测试表征复合材料的力学性能、尺寸稳定性和热导率。结果表明,球形SiO2纳米粒子对复合材料的泡孔结构有明显的细化作用（孔径从纯PU-R泡沫的303 μm降低到170 μm）,可以有效提高复合材料的压缩性能（与纯PU-R泡沫相比,比强度和比模量分别提高了8.3 %和12.5 %）,降低了其线膨胀系数,并使热导率略微下降,而对尺寸稳定性无明显影响。与粒径为400 nm的SiO2纳米粒子相比,粒径为700 nm的SiO2纳米粒子较易均匀分散,对PU-R泡沫力学性能的改善效果更为明显。     

蒸馏水含量对三明治结构硬质聚氨酯泡沫性能的影响

采用异氰酸酯、聚酯多元醇、发泡剂（水）等原料通过一体发泡成型技术制备出一种新型的三明治泡沫夹心复合材料。利用热重分析、扫描电子显微镜等对不同水含量（质量分数分别为0、0.5 %和1.0 %）的硬质聚氨酯泡沫材料的泡孔直径、密度、热导率、压缩性能、三点弯曲和热力学性能等做了研究,进而确定提高硬质聚氨酯性能的最佳工艺。结果表明,随着水含量的增加,硬质聚氨酯泡沫材料泡孔直径增大,密度变小,热导率降低,保温性能提高,而压缩性能和三点弯曲却呈下降趋势;综合考虑硬质聚氨酯泡沫材料泡孔结构和良好的保温隔热及弯曲等力学性能,其最佳含水量为0.5 %。     

A study of composite foams for diving suits subjected to high hydrostatic pressure

In order to obtain foams possessing flexibility and at the same time heat insulation under high hydrostatic pressure, composite foams with spherical rigid foams filled in flexible rubber foam at certain intervals were prepared and their thermal conductivity and flexural rigidity were studied. The following points were found: (1) With a unit model having a spherical rigid foam in the middle, the thermal conduction of a composite foam was analyzed under the conditions of steady one-dimensional heat flow. Theoretical equations giving overall coefficients of heat transmission under atmospheric and hydrostatic pressures were obtained, and the adequacy of these theoretical equations was confirmed by the measurement of overall coefficients of heat transmission of composite foams in an apparatus so constructed as to allow heat conduction experiments under pressures ranging from atmospheric to the hydrostatic pressure corresponding to 100-m depth in water. (2) The effect of the filled spherical rigid foams on heat insulation is notable under hydrostatic pressures corresponding to a 20-m depth or more in water. Under the hydrostatic pressure corresponding to a 100-m depth in water, the coefficient of heat insulation of the most closely filled composite foam used in the experiment was approximately 35% larger than that of the unfilled foam, while the theoretical most closely filled composite foam gives an approximately 110% increase. (3) Under the hydrostatic pressure corresponding to a 100-m depth in water, the flexural rigidity of the most closely filled composite foam used in the experiment was approximately one half that of an unfilled foam of the same heat insulating property.     

木粉／低密度聚乙烯复合材料的发泡研究

用模压法制备木粉／低密度聚乙烯发泡材料。通过差示量热扫描分析,考察了纯偶氮二甲酰胺(AC)及与 ZnO共混物、纯NaHCO3及与柠檬酸(L)共混物的热分解特性,探讨了发泡剂AC、NaHCO3、柠檬酸、交联剂过氧化二异丙苯等对材料力学性能的影响,并在扫描电镜下观察了材料断面的微观形态。结果表明:采用放热发泡剂和复合发泡剂都能使复合材料密度下降20％左右,发泡后材料的冲击性能为发泡前体系的1．5倍左右;复合发泡剂的发泡效果优于单放热发泡剂的效果。     

Effects of liquid‐type silane additives and organoclay on the morphology and thermal conductivity of rigid polyisocyanurate‐polyurethane foams

This article investigates the effects of liquid‐type silane additives and organoclay as a solid‐type additive on the morphological, mechanical and thermal insulating properties of polyisocyanurate‐polyurethane (PIR‐PUR) foams. The organoclay likely acted as nucleating agents during the formation of PIR‐PUR foams. When the liquid silane additives and organoclay were added, the cell size and thermal conductivity of the PIR‐PUR foams appeared to be decreased. However, organoclay did not contribute to reduce the cell size distribution of the foam. PIR‐PUR foams synthesized with tetramethylsilane as a liquid‐type additive showed a smaller average cell size and lower thermal conductivity than that of PIR‐PUR foams synthesized with the other silane additives or with organoclay as a solid‐type additive. For the PIR‐PUR foam with organoclay/TEMS (1.5/1.5 php) mixture, cell size and thermal conductivity of the foam showed similar to the foam with TEMS. These results suggest that smaller cell size appears to be one of the major factors in the improvement of thermal insulation properties of the PIR‐PUR foams. Silane additives did not seem to have a strong effect on the flammability of the PIR‐PUR foams. However, heat resistance was more dominant for the foam with the organoclay at the higher temperature. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Glass bubble reinforced polyurethane foams with high mechanical strength for cryogenic temperature insulation

In this study, glass bubble (GB) is added to polyurethane (PU) foams at different weight ratios—0, 0.25, 0.5, 0.75, and 1 wt% —to investigate the changes in the mechanical and thermal properties of the foam. By conducting several tests and measurements, the density, cell morphology, compressive strength, and thermal conductivity of the foam are studied. In particular, the effect of GB additives is examined by conducting compression tests at various temperatures (−163, −100, −40, and 20°C). Scanning electron microscopy and X-ray microscope reveal that the foams exhibit higher stability below 0.5 wt%, which improves the thermal performance. On the other hand, the compressive strength of the foams increases for all weight ratios of GB, and it increases sharply at 0.75 wt%. In addition, the chemical interactions and the dispersion of additives in the PU matrix are investigated through Fourier transform infrared and X-ray diffractions analysis. It is found that the synthesis of PU foams with GB nanoparticles is an efficient method for improving the mechanical properties and insulation performance of the foam for LNG insulation technology.     

Highly porous YSZ ceramic foams using hollow spheres with holes in their shell for high-performance thermal insulation

Yttria-stabilized zirconia (YSZ) porous ceramic foams were fabricated using YSZ microspheres with holes on the surface to determine their properties as insulation materials. Highly porous YSZ ceramics with bimodal pore structures, such as internal pores in single hollow spheres and external pores between the spheres, were successfully prepared using YSZ spheres as raw materials. Additionally, holes were added to the shells to reduce continuous thermal pathways and significantly enhance the insulation properties. Furthermore, by adding holes on the surface of the sphere, the porous foams using a hollow sphere exhibit a maximized porosity of 80.69%, remarkably enhanced their insulation properties with low thermal conductivity (0.10 W/m-K), and have sufficient compressive strength to protect the green body (5.7 MPa). The mechanical strength of the YSZ porous foam was maintained owing to the uniform arrangement of the supports.     

Preparation and characterization of polyurethane/silica aerogel nanocomposite materials

In this investigation, silica aerogel (SA)/Rigid Polyurethane (PUR) foam composites and silica aerogel/Polyurethane (PU) composites were prepared by dry mixing of granular and grinded silica aerogels with polyol part. They were then combined with diisocyanate part. Three different types of PUR foams and an elastomeric coating grade of PU were studied as well. Results show that thermal conductivity of foams did not decrease by adding silica aerogel. It even increased for some grades which is assumed to be due to the change in cell configuration of these foams. It was also found that sound insulation performance of these cellular composites did not improve significantly. Unlike foam composites, addition of silica aerogel into elastomeric PU improved its thermal and acoustic insulation properties. Because of the more promising properties of elastomeric PU composites, further examinations including measurements of compression strength and water contact angle of silica aerogel/PU composites were also taken. Final results showed a significant improvement in general properties of PU coatings by adding little amounts of silica aerogel (1–4 wt %). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44521.