具有高界面压应力的高分子共混物Ⅰ.制备和拉伸性能

考察了高界面压应力对不相容聚对苯二甲酸乙二醇酯(PET)/聚乙烯(PE)和聚碳酸酯(PC)/PE共混物拉伸性能的影响.高界面压应力是共混物低温成型(PE的成型温度)时,分散相与基体从加工温度冷却到室温过程中基体的收缩比分散相粒子大产生的.尽管PET/PE和PC/PE共混物极不相容,但拉伸强度和模量随着PET和PC含量增加而增加.PET与PC含量相同时,PC/PE的拉伸强度和模量高于PET/PE的.采用Takayanangi方程计算共混物的拉伸模量时,具有高界面压应力的PC/PE共混物的拉伸强度高于界面有良好粘结的共混物的理论值,表明在不添加增容剂时,可通过控制加工条件改善共混物界面相互作用,提高共混材料的性能.     

PC／PET共混物相容性和结晶行为的研究

本工作用差动扫描量热计(DSC)、动态粘弹仪(DMA)、密度梯度、激光小角散射仪(SALS)和光学解偏振仪研究了国产聚碳酸酯/聚对苯二甲酸乙二醇酯(PC/PET)共混物的相容性和结晶行为。DSC研究结果表明,共混物中在PET含量为60％以下时,只有一个玻璃化转变温度(T_g),说明共混物是完全相容的;在PET含量大于60％时,共混物呈现出两个玻璃化转变温度,并发生内移,说明共混物是部分相容的。用DMA测试也得到同一结果。共混物中PET的结晶动力学与一般结晶高聚物相似,等温结晶前期符合Avrami方程,等温结晶后期偏离Avrami方程。     

PE接枝共聚物增韧聚碳酸酯/PE共混体系的研究

本文采用聚乙烯的马来酸酐接枝共聚物(PE-g-MAH)作为第三组份,与PC/PE共混物形成三元共混体系,进行PC共混改性研究。随着PE-g-MAH量的增加,PC/PE共混物的缺口冲击强度有明显的提高,而机械强度和工作温度影响不大。用扫描电镜对掺入不同量的PE-g-MAH的PC/PE共混物进行了形态研究,观察到在PC/PE共混物中,PE分散在PC的连续相中成为两相结构,但分散得很不均匀,随着PE-g-MAH含量增加,分散渐趋均匀,在用CHCl_8蚀刻,PC/PE共混物的扫描电镜各呈许多小球(PE)分散在PC连续相中,小球边界十分清晰。加了20％PE-g-MAH后,边界清晰的小球消失,PE-g-MAH起了相容剂的作用,并用动态力学性能测试作了证实。     

PET/PC/氨基硅油共混物的制备及阻燃机理

采用熔融共混法在密炼机上制备了聚对苯二甲酸乙二醇酯(PET)/聚碳酸酯(PC)/氨基硅油(ASO)阻燃共混材料,研究了氨基硅油用量对PET/PC共混材料阻燃性能和燃烧行为的影响,并探究了氨基硅油的阻燃机理。结果表明,ASO的加入有效改善了PET/PC共混物的阻燃性能。当ASO添加量为0.5 phr时,PET/PC/ASO共混物通过UL 94 V-0级,氧指数达28%。锥形量热测试结果显示,ASO的加入显著降低了热释放速率峰值(199.9 kW/m~2),并促使基体分解更加完全以释放出大量的不可燃性气体(CO_2)。结合烧结残炭的傅里叶变换红外光谱和扫描电镜-能谱仪分析,ASO的加入同时起到了气相与凝聚相阻燃的作用。此外,由于ASO类似偶联剂的作用,使得PET/PC/ASO三元共混物的韧性得到了很大的提升。     

PET/PC共混物配比对其高压结晶行为的影响

利用SEM及W AXD等测试手段研究了配比对PET/PC共混物高压结晶行为的影响。SEM观察表明,随PC比例的增加,共混物高压下主要结晶形态以伸直链晶体,生长成熟的立体开放球晶,大尺寸球晶的方式变化。拟合分峰法和W arren-A verbach傅氏分析法的计算结果表明,随PC含量的增加,高压结晶共混物的结晶度降低,PET的平均晶粒尺寸总体呈减小趋势,晶粒尺寸分布则变窄,而晶格畸变平均值在一定PC比例范围内达到极大值。     

PET/PLA共混物中小分子扩散行为的分子动力学模拟

采用分子动力学(MD)模拟方法研究了O2、CO2小分子在不同质量比(90/10、70/30、50/50、30/70和10/90)聚对苯二甲酸乙二醇酯(PET)/聚乳酸(PLA)共混物中的扩散行为,基于Einstein关系式计算了小分子在共混物中的扩散系数。讨论了不同探针半径对自由体积分数(FFV)的影响以及自由体积分数与扩散系数的关系。研究结果表明,探针半径越大,自由体积分数越小;扩散分子的动力学半径越小,在同一比例PET/PLA共混物中的扩散系数越大,与自由体积理论取得统一。当PET/PLA共混物质量比为70/30时共混物的阻隔性能最好。     

具有高界面压应力的高分子共混物Ⅱ.拉伸过程中形态演化与增强机理

研究了聚对苯二甲酸乙二醇酯(PET)/聚乙烯(PE)和聚碳酸酯(PC)/PE共混物在拉伸过程中形态的演化和增强机理.结果表明,高界面压应力是共混物在基体加工温度成型时,从成型温度冷却到室温过程中基体收缩比分散相大产生的;两种共混物在拉伸中有不同的形态演化过程:PC粒子原位形成了微纤,粒子与基体间没有明显的界面滑动,而PET粒子只产生较小的塑性变形,成为椭球状粒子,粒子与界面间存在滑动.PC对基体PE的增强效果比PET的更好,因为PC/PE共混物拉伸过程中形成了良好增强作用的原位微纤.在拉伸过程中,PET/PE试样的细颈在靠近非浇口端形成,并从此扩展开.部分拉伸后,PC/PE试样比PET/PE试样的弹性回复大,回复到平衡状态时间长,这是两种共混物分散相变形机理不同引起的.     

高磷含量阻燃聚酯及其与聚对苯二甲酸乙二醇酯共混物的制备研究

以阻燃剂2-羧乙基苯基次磷酸(CEPPA)作为第三单体采用共缩聚法制备了高磷含量的阻燃聚酯,然后通过熔融共混技术制备了聚对苯二甲酸乙二醇酯(PET)/阻燃聚酯共混物。通过红外光谱、核磁、差示量热、扫描电镜(SEM)、极限氧指数及元素分析对高磷含量的阻燃聚酯和PET/阻燃聚酯共混物的结构及性能进行表征。结果表明:大多数CEPPA以无规共聚形式分布在大分子链中,少部分以短嵌段形式存在于大分子链中。SEM结果表明:PET与高磷含量阻燃聚酯之间有很好的相容性。当磷含量达到6mg/g时,PET/阻燃聚酯共混物的极限氧指数超过28%,具有很好的阻燃性。     

不同因素对聚碳酸酯/聚对苯二甲酸乙二醇酯共混物的性能影响研究

通过挤出和注塑制备聚碳酸酯/聚对苯二甲酸乙二醇酯(PC/PET)共混物，探究成核剂对PC/PET共混物的结晶形态、热行为、形貌及力学性能的影响。此外，对相容剂添加量和PC/PET质量配比等变量也做了性能影响分析。最佳条件为：相容剂添加0.5%、PC/PET=3/7、成核剂TiO₂添加1%。适量粒径均匀、细小的TiO₂作为成核剂能很好地分散在PC/PET基体内，得到的PC/PET共混物形貌平整光滑，拉伸强度、弹性模量及冲击强度分别为40.5MPa、7654.0N/mm²及14.3J/m,在DSC曲线上出现明显的冷、热结晶峰，热结晶的结晶温度均高于冷结晶，且DMA结果显示成核剂的加入使玻璃化转变温度降低，不相容PC相和PET相的T_g不断靠近。     

SEBS-g-MAH增容PS/PC体系的结构与力学性能

研究了不同配比的聚苯乙烯/聚碳酸酯(PS/PC)共混体系的结构与力学性能及彼此之间的关系,讨论了增容剂氢化苯乙烯-丁二烯共聚物接枝马来酸酐(SEBS-g-MAH)对共混物相容性及力学性能的影响。差示扫描量热分析表明,PS/PC表现出2个玻璃化转变温度(Tg),而PS/PC/SEBS-g-MAH则只有1个Tg。扫描电镜的分析结果表明,PS为连续相,PC为分散相,而且SEBS-g-MAH的加入使PS与PC的界面变得模糊。可见增容剂对共混体系具有明显的增容作用。共混物的冲击强度在PC用量大于30 phr时明显提高,拉伸强度和冲击强度在低PC含量时较纯PS有一定程度的下降,但随PC含量增加又逐渐提高;增容共混物的力学性能比未增容的有较大提高;当PC用量约40 phr时共混物具有最好的综合性能。     

Thermomechanical properties of a polymer blend: Investigation of a third phase

This paper deals with immiscible blends of poly(ethylene terephthalate) with polycarbonate obtained by melt mixing. Miscibility of the polyester blends is influenced by transesterification reactions, that are catalyzed either by catalyst residues in the polyesters or by catalysts added on purpose in the blend. These reactions convert the initial homopolymers into block and even random copolymers and affect both the miscibility of the system and the adhesion between the phases. The effect of catalysts and stabilizers on the morphology of PET/PC 50/50 blends was investigated using dynamic mechanical thermal analysis, rheology, microscopy and tensile tests. PET/PC 50/50 containing 0.05 wt.% of lanthanide acetyl acetonate exhibit a irreversible transition occurring at temperature higher than the glass transitions of PET and PC. This transition induces a large increase of the shear modulus and it was attributed to the formation of a third phase in the blend.     

Effects of composition and transesterification catalysts on the physico-chemical and dynamic properties of PC/PET blends rich in PC

Melt blending of polycarbonate (PC)/poly(ethylene terephthalate) (PET) rich in PC at absence/present of different type of tranesterification catalysts was carried out by using reactive extrusion method. The thermal, dynamic, and morphological properties were studied. It was found that all blends are formed by a PC matrix and a semicrystalline (12–20% of crystallinity) of PET dispersed phase. The addition of a catalyst in the mixing process promotes a refined and homogeneous dispersion of PET, as well as it enhances the dynamicmechanical behavior of PC/PET blends compared with PC. These effects are attributed to the emulsifying effect of the PC–PET copolymer generated by transesterification. Additionally, this copolymer contributes to the miscibility between phases as demonstrated by the glass transition (T _g) shift of PC phase and PET phase.     

Morphology-tensile behavior relationship in injection molded poly(ethylene terephthalate)/polyethylene and polycarbonate/polyethylene blends (I) Part I Skin-core Structure

The skin-core structure of injection molded poly(ethylene terephthalate) (PET)/polyethylene (PE) and polycarbonate (PC)/PE blends was investigated. The results indicate that both shape and size of the PET and PC phases depended not only on the nature properties of PET/PE and PC/PE blends, but also on the injection molding parameters such as injection speed and the positions in the molded bars. The morphology in the section perpendicular to the melt flow direction included four layers, surface, sub-skin, intermediate layers as well as core zone. The surface layer was ignored in the present study. The sub-skin layer contained more or less fibrous structure and its thickness gradually decreased along the molded bar from the gate toward the non-gate end. At the same injection speed, the concentration of the injection-induced fibers in PC/PE blend was much higher than that in PET/PE blend. In the core region, the dispersed phase was mainly composed of spherical particles whose diameter increased along the melt flow pathway. Between these two layers, there was an intermediate layer where the dispersed particles mainly assumed the form of fibers, ellipsoids or spheres. Generally, no matter whether the dispersed particles were elongated or not during injection molding, the PET particles were larger than PC ones.     

Effects of nematic polymer liquid crystal on crystallization and structure of PET/Vectra blends

We investigate the effects of a nematic liquid crystalline polymer, Vectra A, on the structure and properties of its blends with a semicrystalline polymer, poly(ethylene terephthalate),PET. PET/Vectra blend composition ranged from 100/0 to 60/40. Real-time, in situ studies ofisothermal and non-isothermal melt crystallizations of these blends were conducted usingsimultaneous wide and small angle X-ray scattering (WAXS and SAXS), differentialscanning calorimetry (DSC), and quantitative polarizing optical microscopy. All techniquesconfirm that the addition of Vectra nematic liquid crystal delays the onset of crystallization,and affects the degree of crystallinity and structural parameters such as Bragg long period,lamellar thickness and linear stack crystallinity. SAXS results indicate that some of theVectra component penetrates into the interlamellar regions of the crystal stacks. Vectrainterrupts the entangled polymer network making it more difficult for lamellar crystals tonucleate. Slower nucleation and growth result in increased perfection of the PET crystalsgrown isothermally, but reduces the crystallization temperature of PET crystals grownnon-isothermally causing these crystals to be less perfect.     

PC／PET共混体系的形态,结构和性能及催化剂对它们的影响

本文研究了PC/PET熔融共混体系组分比和酯交换反应对共混物形态、结构和性能的影响。结果表明:随PET含量增加,体系中两个组分的互容性增加。酯交换反应可以增大两个组分的互容性。加入催化剂所引起的酯交换反应改变了共混物的结构,使共混物的力学性能有所下降。     

PC／PET共混物的非等温结晶动力学

采用等速变温ＤＳＣ法对ＰＣ／ＰＥＴ共混体系的非等温结晶动力学进行了研究，结果表明，从玻璃态结晶时，随着ＰＣ含量的增加，ＰＥＴ组分的结晶速率先增加后降低。耐从熔体结晶时，体系的结晶速率随着ＰＣ含量的增加而增加，讨论了ＰＣ对ＰＥＴ组分结晶过程的影响。     

Dielectric properties of polyarylate blends

Dielectric properties and molecular motion were studied by use ofdielectric spectroscopy and differential scanning calorimetry for twoblends, fully transesterificated polyarylate of bisphenol A withterephthalate/isophthalate (50/50) (PA)/polycarbonate of bisphenol A(PC) blends and PA/poly(ethylene terephthalate) (PET) blends. All thequenched PA/PC and PA/PET blends were amorphous and the glasstransition temperature (Tg) was varied with the blends ratioaccording to Gordon-Taylor equation. The PA/PET blends with more than60% of PET crystallized above the crystallization temperature. ThePA/PC and PA/PET blends showed two dielectric relaxations, above Tg and below Tg, which are related to a glasstransition and a local motion of short segment, respectively. The relaxation moved to lower temperatures as PC or PET contentincreases, reflecting the lowering Tg faithfully. In the PA/PETblends, the static (₀) and the limiting dielectricconstant (), and the increment () for the relaxation decreases with increasingtemperature and the decrease falled on one curve, independent of theblend ratio. Any ferro- and piezoelectricity were not observed fortwo blends.