增容作用对聚乳酸/高密度聚乙烯合金发泡行为的影响

以乙烯甲基丙烯酸缩水甘油酯共聚物（GEMA）为增容剂,采用熔融共混法制备了聚乳酸（PLA）/高密度聚乙烯（PE-HD）增容合金。以CO2为发泡剂进行釜压发泡,制备出PLA/PE-HD增容合金泡沫。结果表明,加入GEMA后,聚合物合金的结晶能力有所下降和流变性能略有提高;随着GEMA含量的增加,PE-HD分散相尺寸减小,数量增多,聚合物合金发泡样品的泡孔结构可以实现从复合泡孔到单一泡孔的转变。     

塑化聚乙烯醇的流变性能及发泡行为研究

采用毛细管流变仪对PVA流变性能进行了表征,用差示扫描量热仪（DSC）研究了降温速率对PVA结晶性能的影响,通过PVA添加化学发泡剂熔融挤出的方法制备PVA发泡材料,并用扫描电镜和密度测试仪分别对发泡材料的泡孔形态和密度进行了表征。结果表明,PVA对剪切作用非常敏感,在低剪切速率下熔体粘度较大,泡孔分布均匀,材料密度较小,在高剪切作用下熔体强度低,气体容易逃逸,导致发泡材料泡孔破裂或合并;低降温速率下熔体粘度小,泡孔易合并、塌陷,合适的降温速度下,PVA熔体粘度适中,发泡材料气泡尺寸小、分布均匀,较快的降温速度下,由于气体压力过大而造成气泡合并,联通,材料密度大。     

发泡片材专用LDPE树脂的结构与性能

通过熔体流动速率仪、红外光谱仪、凝胶渗透色谱仪、差示扫描量热仪等分析了发泡片材专用低密度聚乙烯树脂LD800的分子结构、聚集态结构与流变性能。LD800熔体流动速率为2.5 g/10 min,重均分子量约18.1×104,相对分子质量分布为7.0,熔胀比为1.60,加工性能良好,在保证加工效率的情况下具有较高的发泡倍率和制品回弹性能;应用性能研究表明,采用LD800发泡时发泡倍率高,泡孔均匀,泡孔坍塌率低。     

PP／PE-HD共混体系发泡成型及机理分析

采用PP与PE-HD共混的方法来改善PP的发泡性能，并从共混体系的熔体强度和结晶性能两个方面分析PE-HD含量对泡孔结构的影响机理。结果表明，PP／PE-HD共混体系的熔体强度随着PE-HD含量的增加先升高后减小，在含量为30％（质量分数，下同）时熔体强度最高。随着PE-HD含量的增加，共混体系中PP和PE-HD的熔点先升高后降低，PP的结晶度先减小后增大，而PE-HD的结晶度却逐渐增加。在含量为30％时，PP和PE-HD的熔点最高，PP的结晶度最小。PP与PE-HD共混以后，泡孔结构有了很大改善，且与熔体强度和结晶度相对应，泡孔结构在PE-HD含量为30％时最好。     

聚碳酸亚丙酯/纳米二氧化硅共混体系流变及发泡性能研究

通过同向双螺杆挤出机对聚碳酸亚丙酯/纳米二氧化硅（PPC/nano-SiO2）体系共混造粒,利用旋转流变仪对其流变性能进行了表征,并采用间歇发泡装置进行发泡实验,研究了nano-SiO2含量对PPC流变及发泡性能的影响。结果表明,当nano-SiO2添加量为5份（质量份,下同）时,nano-SiO2与PPC之间形成了逾渗网络,并且此时发泡样品泡孔平均直径最小,达到9.65μm;泡孔密度最大,达到2.37×10^9个/cm3;泡孔直径分布最窄且泡孔结构均匀。     

超高相对分子质量聚乙烯对双峰HDPE树脂性能的影响

为了提高双峰高密度聚乙烯（HDPE）的力学性能,采用超高相对分子质量聚乙烯（UHM—WPE）与双峰HDPE以不同比例共混,对共混物的相对分子质量及其分布、热性能、流变性能和力学性能进行了测试。UHMWPE的加入使高相对分子质量部分显著增加,流变性能下降,添加量小于10％（质量分数）时,共混物粘度在高剪切速率下变化不大;UHMWPE可提高共混物的熔融温度和初始结晶温度,结晶度先增加然后迅速降低;随着UHMWPE含量的增加,混合物的拉伸强度也随之增加,呈线性关系;结晶度与冲击强度成反比。     

聚四氟乙烯原位纤维化对TPEE/PTFE复合材料发泡行为的影响

通过熔融共混法研究了不同加工工艺对聚四氟乙烯（PTFE）纤维化的影响,制备了热塑性聚酯弹性体（TPEE）/PTFE纳米纤维复合材料。在此基础上,研究了PTFE含量对TPEE的结晶行为、流变行为以及发泡行为的影响。结果表明,PTFE纤维可以促进TPEE结晶,改善TPEE的流变性能。纳米纤维的高比表面积为泡孔成核提供了大量成核位点,有效提高了泡孔密度,降低了泡孔尺寸;当PTFE含量为2份时,制备了平均泡孔直径为3.2 μm,平均泡孔密度为3.11×10¹⁰ 个/cm³的复合材料泡沫。     

聚乳酸/马来酸酐接枝线形低密度聚乙烯合金的制备及其发泡行为研究

通过熔融共混法制备聚乳酸（PLA）/马来酸酐接枝线形低密度聚乙烯（PE-LLD-g-MAH）合金,使用差示扫描量热仪、旋转流变仪、扫描电子显微镜、偏光显微镜等仪器研究了不同PE-LLD-g-MAH含量的PLA合金的结晶性能、流变性能、断面形貌及发泡性能等。结果表明,随着PE-LLD-g-MAH含量的增加,PLA/PE-LLD-g-MAH合金的冷结晶温度大幅提高和流变性能明显改善,样品断面出现了明显的“海岛”结构,发泡样品的泡孔尺寸逐渐减小,泡孔密度增加。     

热塑性聚酰胺弹性体的扩链反应及发泡行为研究

采用环氧型扩链剂KL-E4370对热塑性聚酰胺弹性体（TPAE）进行了扩链改性,通过旋转流变仪、差示扫描量热仪（DSC）和扫描电子显微镜（SEM）等对扩链前后TPAE的流变性能、结晶性能和发泡性能进行了表征,并研探讨了扩链反应的机理。结果表明,TPAE的熔体黏弹性较差,可发性差;加入扩链剂能够有效提高TPAE的支化程度;通过对TPAE进行扩链改性可使其复数黏度增加一个数量级以上,提高熔体黏弹性,从而增大发泡倍率,拓宽发泡温区,改善泡孔破裂及合并问题;但扩链后TPAE的结晶性能下降,起始结晶温度降低20 ℃左右,使得泡孔收缩情况明显;扩链剂含量为1 %（质量分数,下同）的TPAE泡沫的发泡倍率从纯TPAE的5.5倍增加到了约9倍,泡孔直径达50 μm。     

具有双峰泡孔结构的交联聚乙烯发泡材料的制备

将高密度聚乙烯(HDPE)和交联剂过氧化二异丙苯(DCP)在转矩流变仪中熔融共混,制备交联聚乙烯。通过扭矩曲线、凝胶含量测试及差示扫描量热仪(DSC)测试,研究了HDPE交联前后流变性能、凝胶含量、熔融和结晶行为的变化。利用超临界二氧化碳作为物理发泡剂对交联HDPE进行降温与降压协同釜压发泡,采用扫描电子显微镜(SEM)观察第一次压力降对双峰泡孔形成的影响,同时采用数学统计方法对大泡孔和小泡孔的尺寸分布进行了统计。最后,采用密度天平对发泡样品的表观密度进行了测试。结果表明,加入DCP后,HDPE发生了交联,形成了部分网状结构;第一次压力降为4 MPa时,材料形成的双峰泡孔较为理想。     

High‐density polyethylene foams. I. Polymer and foam characterization

The density and morphology of closed‐cell high‐density foams were investigated with four different molecular weights of high‐density polyethylene (HDPE). The characterization of polyethylene via rheological methods was used to determine its influence on foam density and morphology. We found that foaming grade decreased with increasing molecular weight and increased with blowing agent content. The average cell size was also a strong function of molecular weight and blowing agent content. Increasing both the molecular weight and amount of blowing agent decreased the cell size. Cell size also increased for our lowest molecular weight HDPE but decreased for the others. Cell density also increased with increasing HDPE molecular weight. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2111–2119, 2003     

黏度对水发泡聚苯乙烯发泡性能的影响

采用水作为物理发泡剂,对聚苯乙烯(PS)进行挤出发泡。研究了低温PS水发泡的流变性能,并研究了黏度对PS发泡制品性能的影响。结果表明:水会影响PS在发泡加工过程中的黏度;在低温情况下,水发泡后的PS仍然具有流动性;其黏度随剪切速率的增大而减小,在相同的剪切速率下,温度越高黏度越低。当模头温度为140℃、螺杆转速为15r/min时,可制备出表面光滑、泡孔细密均匀、质轻的PS水发泡制品。     

Preparation and characterization of chain extended Poly(butylene succinate) foams

In order to improve the viscoelasticity and foamability, poly (butylene succinate) (PBS) was modified through reactive melt mixing with chain extender (CE) having multi epoxy‐groups. Subsequently, the prepared chain extended PBS (CEPBS) was foamed in a high pressure stainless steel autoclave using CO₂ as physical blowing agent. The molecular weight, thermal properties, rheological properties, and foam properties of various PBS samples were characterized using gel permeation chromatography, differential scanning calorimetry, rotational rheometer, and scanning electron microscope, respectively. With the introduction of CE, the molecular weight, the crystallization temperature, the complex viscosity and storage modulus of PBS were increased and the crystallization degree of PBS was decreased. At the CE content of 0.75 phr, the cross‐linking structure was formed and the expansion volume ratio increased to nearly 15 times, which meant the chain extension played an important role in the foaming process of PBS. POLYM. ENG. SCI., 55:988–994, 2015. © 2014 Society of Plastics Engineers     

Effect of the high‐density polyethylene melt index on the microcellular foaming of high‐density polyethylene/polypropylene blends

The effect of high‐density polyethylene (HDPE)/polypropylene (PP) blending on the crystallinity as a function of the HDPE melt index was studied. The melting temperature and total amount of crystallinity in the HDPE/PP blends were lower than those of the pure polymers, regardless of the blend composition and melt index. The effects of the melt index, blending, and foaming conditions (foaming temperature and foaming time) on the void fractions of HDPEs of various melt indices and HDPE/PP blends were also investigated. The void fraction was strongly dependent on the foaming time, foaming temperature, and blend composition as well as the melt index of HDPE. The void fraction of the foamed 30:70 HDPE/PP blend was always higher than that of the foamed 50:50 HDPE/PP blend, regardless of the melt index. The microcellular structure could be greatly improved with a suitable ratio of HDPE to PP and with foaming above the melting temperature for long enough; however, using high‐melt‐index HDPE in the HDPE/PP blends had a deleterious effect on both the void fraction and cell morphology of the blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 364–371, 2004     

Preparation and properties of foamed cellulose acetate/polylactic acid blends

In order to improve the foaming performance of pure cellulose acetate (CA), blends were prepared by mixing polylactic acid (PLA) in CA and foamed by supercritical CO₂ (ScCO₂) in this study. The effect of PLA content (percentage by mass of blend) on structure, thermal properties, rheological properties, foaming properties and mechanical properties of the blends was investigated. The results showed that the addition of PLA destroyed the original hydrogen bonds of CA, while the blends had good crystallization properties. At the same time, compared with pure CA, the glass transition temperature (T_g) of the blends decreased, and the initial decomposition temperature (T₀) was reduced from 349.41°C (pure CA) to 334.68°C (CA/20%PLA). In addition, the rheological properties of the blends were improved, and the viscosity was reduced, which was obviously beneficial to foaming process. The pore size and density of the foamed blends both reached the maximum value at 20%PLA. The presence of PLA could degrade the mechanical properties of the blends. However, the overall drop (1.01 KJ/m²) of impact strength of the blends after foaming is much smaller than that before foaming (12.11 KJ/m²), indicating that the improvement of foaming performance was beneficial to improve its impact strength.     

Effect of molecular structure and rheology on the compression foam molding of ethylene‐α‐olefin copolymers

The morphology and mechanical properties of foams made out of a series of ethylene‐α‐olefin copolymers having well‐characterized rheological properties were investigated. A compression foaming molding technique was implemented, using azodicarbonamide as the blowing agent. The polymers differed in the amount of comonomer contained (resulting in a range of densities), type of comonomer (octene vs. butene) and molecular weight, resulting in variable thermal properties and different rheological responses under shear and extensional flow. The results showed that the majority of the octene‐based copolymers with comparable rheological properties had similar foam morphology. A distinct behaviour was observed for the butene‐based copolymer, as well as the octene‐containing one having the lowest density and lowest melting/crystallization points. The poor foamability of these grades was attributed to their differences in extensional and thermal properties, respectively. Increasing density resulted in a higher secant modulus of the foamed samples. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

聚乳酸/聚己二酸对苯二甲酸丁二酯合共混体系发泡行为研究

采用多环氧基团增容剂制备了聚乳酸/聚己二酸对苯二甲酸丁二酯(PLA/PBAT)共混物,研究了增容剂含量对于PLA/PBAT共混体系的结晶和流变性能的影响。并采用高压釜发泡的方法进行PLA/PBAT共混物的间歇发泡,研究增容剂对发泡材料泡体结构的影响。结果表明,增容剂加入后会降低其绝对结晶度,以及显著改善PLA/PBAT共混体系的熔体弹性,提高其可发性;增容剂可以有效地改善共混体系的泡体结构,降低共混物发泡密度,提高其发泡倍率。     

Improving polypropylene microcellular foaming through blending and the addition of nano‐calcium carbonate

This article reports an attempt to improve polypropylene (PP) microcellular foaming through the blending of PP with high‐density polyethylene (HDPE) as a minor component and the incorporation of nano‐calcium carbonate (nano‐CaCO₃) into PP and its blends with HDPE. Three HDPEs were selected to form three blends with a viscosity ratio less than, close to, or greater than unity. Two concentrations of nano‐CaCO₃, 5 and 20 wt %, were used. The blends and nanocomposites were prepared with a twin‐screw extruder. The foaming was carried out by a batch process with supercritical carbon dioxide as a blowing agent. The online shear viscosity during compounding and the dynamic rheological properties of some samples used for foaming were measured. The cell structure of the foams was examined with scanning electron microscopy (SEM), and the morphological parameters of some foams were calculated from SEM micrographs. The rheological properties of samples were used to explain the resulting cell structure. The results showed that the blend with a viscosity ratio close to unity produced a microcellular foam with the minimum mean cell diameter (0.7 μm) and maximum cell density (1.17 × 10¹¹ cells/cm³) among the three blends. A foamed PP/nano‐CaCO₃ composite with 5 wt % nano‐CaCO₃ exhibited the largest cell density (8.4 × 10¹¹ cells/cm³). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

聚乳酸扩链改性及其挤出发泡的研究

采用扩链剂对聚乳酸（PLA）进行扩链改性,研究了扩链剂对PLA流变性能的影响。采用3种不同类型的化学发泡剂：发泡剂A（发泡母粒）、发泡剂B\[自制复合发泡剂：偶氮二甲酰胺（AC发泡剂）/碳酸氢钠(NaHCO3)\]、发泡剂C(自制改性AC发泡剂),利用单螺杆挤出机对PLA进行挤出发泡。采用扫描电子显微镜观察分析了发泡材料的断面泡孔结构。结果表明,加入扩链剂可有效提高PLA的熔体强度和黏度及降低其熔体流动速率,改善PLA的发泡效果,扩链剂含量为0.8份（质量分数,下同）时,发泡材料的发泡效果最好;实验所用的3种发泡剂中,发泡剂C的发泡效果最好,发泡剂含量为1.5份时,发泡样品的表观密度较小（0.6 g/cm3）,泡孔直径最小(约为57 μm),泡孔密度最大（约为7.69×10^6个/cm3）,泡孔分布均匀,无明显泡孔破裂和连通现象。