聚乳酸的非等温结晶动力学研究

采用差示扫描量热仪研究了聚乳酸(PLA)样品在5种不同升温速率下的非等温结晶行为，采用Jeziorny法、Ozawa法、Mo法等分析了PLA的非等温结晶动力学。结果表明：随着升温速率的增加，PLA的熔融结晶峰向高温端移动，结晶峰变宽，结晶时间变短，同时结晶也变差。利用Jeziorny法和Mo法求得Avrami指数n和Ozawa指数m,在不同升温速率下，结晶初期的Avrami指数n和Ozawa指数m接近，均处于2～3,说明PLA的均相成核以一维方式为主、二维方式为辅；在升温速率为5～20 K/min时，结晶中期的PLA Avrami指数n>5、Ozawa指数m>3.5,均高于结晶初期的Avrami指数n与Ozawa指数m,表明PLA除了呈现均相成核的三维生长方式之外，还出现了结晶堆积的现象；当升温速率为30～40 K/min时，结晶中期的Avrami指数n和Ozawa指数m均与初期表现一致，Avrami指数n在3.5左右，Ozawa指数m为2.5～3.5,表明该条件下PLA以均相一维和二维2种方式共存结晶。应用Mo法得到的升温速率F(T)随着相对结晶度的增加而增加，表明随着结...     

聚乳酸/四针状氧化锌晶须非等温冷结晶行为的研究

采用熔融共混法制备了聚乳酸(PLA)/四针状氧化锌晶须(T-ZnOw).用差示扫描量热仪研究了PLA及PLA/T-ZnOw的非等温冷结晶行为;用Jeziorny法和Mo法对其非等温冷结晶动力学进行了分析研究,并计算了相关的结晶动力学参数.结果表明,Jeziorny法和Mo法均能很好地描述PLA及PLA/T-ZnOw的非等温冷结晶过程,且结果一致.Jeziorny法分析表明,初次结晶阶段PLA及PLA/T-ZnOw的Avrami指数n1值范围分别为4.22～5.43和3.11～4.80,而二次结晶阶段的Avrami指数n2值范围分别为3.10～4.66和2.69～5.57,说明T-ZnOw的加入改变了PLA的成核和晶体生长规律.Mo法分析表明,在相同的X(t)下,PLA/T-ZnOw的F(T)值整体大于PLA,T-ZnOw的加入降低了PLA的结晶速率.偏光显微镜观察结果显示,随着T-ZnOw的加入,PLA球晶尺寸减小,数目增多,T-ZnOw促进了PLA的成核.     

硅烷交联POE的非等温结晶动力学研究

通过差示扫描量热法（DSC）研究了乙烯-1-辛烯共聚物（POE）,过氧化二异丙苯改性POE和硅烷交联POE的非等温结晶动力学。应用Avrami法和莫志深法分别对POE,DCP改性POE和硅烷交联POE进行了非等温结晶动力学的计算。Avrami方法计算得到的结晶速率常数Zc和半结晶时间t1/2表明在同一降温速率下,随着POE的交联程度增加,Zc值减小,而t1/2则增大,结晶速率随POE交联程度的增加而降低,随降温速率增加而增加。莫志深方法计算结果表明,达到相同的结晶度,交联POE所需的降温速率要大于纯POE所需的降温速率,说明交联POE的结晶速率要低于纯POE的结晶速率。     

聚乳酸/聚癸二酸丙三醇酯共混物的形态及结晶性能

用SEM、DSC、光学解偏振光、POM及WAXD研究聚乳酸/聚癸二酸丙三醇酯(PLA/PGS)共混物的形态和等温结晶性能.结果表明:PLA与PGS发生了相分离,PLA分子链之间存在部分PGS.当<110℃等温结晶时PLA/PGS共混物的半结晶时间(t1/2)随PGS含量的增加而降低,其晶体尺寸较纯PLA大;当≥110℃等温结晶时,PLA/PGS共混物的t1/2随PGS含量的增加而变大,共混物的晶体尺寸明显增大,形成球晶.但当PGS的含量为20%并于120℃等温结晶时,晶体产生暗斑.PLA及PLA/PGS共混物的晶形都为α形.     

热喷涂LDPE/n-SiO2复合涂层非等温结晶动力学

采用火焰喷涂法制备了低密度聚乙烯（LDPE）涂层和LDPE/纳米二氧化硅（n-SiO₂）复合涂层。利用差示扫描量热法（DSC）对涂层的非等温结晶行为进行研究,并用Jeziorny法和Mo法进行处理。结果表明,Jeziorny法和Mo法处理涂层的非等温结晶过程比较合理;Jeziorny法得到的结晶速率常数和Avrami指数均随冷却速率的增加而增加,且n-SiO₂的加入使复合涂层的结晶速率常数和Avrami指数略有升高、半结晶时间降低,结晶速率增大,表明n-SiO₂相似文献   

室温自交联低密度聚乙烯结晶动力学的研究

采用硅烷接枝、交联两步法制备了室温自交联低密度聚乙烯（PE-LD）,通过傅里叶变换红外光谱、差示扫描量热仪研究了硅烷接枝和室温自交联对PE-LD结晶性能的影响。结果表明,硅烷接枝和自交联反应对PE-LD的结晶行为有明显的影响,接枝和交联后,PE-LD的Avrami指数在3.8～6.0之间,高于纯PE-LD;Avrami指数随引发剂含量的增加先增加后降低,随催化剂含量的增加而降低;硅烷接枝PE-LD的结晶动力学速率常数高于纯PE-LD,而交联PE-LD的结晶动力学速率常数低于纯PE-LD。     

聚丙烯/聚磷酸铵复合材料的等温结晶行为

采用差示扫描量热法研究了聚丙烯(PP)聚/磷酸铵(APP)复合材料的等温结晶过程。引入APP后,PP/APP复合材料的平衡熔点升高,结晶速率大幅度提高。采用Avrami方程研究了该体系的结晶动力学,发现PP/APP复合材料呈现明显的异相成核特征,随w(APP)的增加,Avrami结晶速率常数增大,半结晶时间降低。     

高相对分子质量成核剂改性聚丙烯的非等温结晶动力学和力学性能研究

采用差示扫描量热仪(DSC)研究了高相对分子质量成核剂（PNA）改性聚丙烯( PP)在不同的降温速率下的非等温结晶动力学,并使用电子万能试验机测定了PP和PNA改性PP的力学系能。用修正Avrami 方程的Jeziorny 法来处理PNA改性PP 的非等温结晶行为。结果表明,在各个降温速率下,PNA的加入都能够明显降低PP相对结晶度达到50%的时间（t1/2）,加入0.3份PNA的PP与纯PP相比,其t1/2仅为纯PP的64.9 %,加入PNA后,结晶动力学常数( Zc ) 增加,结晶速率增加; PP的n值随着降温速率的增加而降低,而加入PNA后,n值随着降温速率的增加而升高,加入PNA后,PP的拉伸强度和冲击强度能够同时提高。     

松香型成核剂成核聚丙烯的非等温结晶动力学研究

采用 DSC 法研究了聚丙烯(PP)和松香型成核剂成核 PP 在不同的降温速率下的非等温结晶动力学。采用修正的 Avrami 方程对 DSC 的测试结果进行了分析。结果表明,松香型成核透明剂和分散剂能显著提高 PP 的结晶温度,用 Jeziorny 法来处理松香型成核 PP 的非结晶等温结晶行为是较为吻合的。加入松香型成核透明剂和分散剂后,PP 的半结晶时间减少,结晶动力学常数 Z_c 增加,结晶速率增加;同一降温速率,松香型成核透明剂和分散剂成核PP 的 n 值较纯 PP 减少,说明结晶成核方式发生了改变。     

PEN非等温冷结晶动力学的研究

采用差示扫描量热(DSC)法对聚萘二甲酸乙二醇酯(PEN)的非等温冷结晶动力学进行研究;通过改变升温速率,讨论了PEN冷结晶起始温度与峰顶温度之间存在差值的原因;对比了两种不同的冷结晶起始点的确定方法对冷结晶动力学常数的影响。结果表明:以DSC曲线偏离基线作为PEN冷结晶的起始点,得到的表观Avrami指数很大;用基线延长线与DSC曲线的切线的交点作为冷结晶的起始点和结束点,得到的表观Avrami指数为2.55,且不随升温速率的变化而变化,与等温熔融热结晶方法得到的结果接近,具有相似的结晶生长方式。     

Dispersion of Poly(phenylene ether) in a Poly(phenylene sulfide)/Poly(phenylene ether) Alloy

We have devised and developed a new method for the preparation of a poly(phenylene sulfide)/poly(phenylene ether) (PPS/PPE) alloy, which has micro‐dispersed PPE in the PPS matrix. PPS was chemically treated to activate the reactivity of the PPS end‐group by extrusion in the presence of diphenylmethane diisocyanate (MDI) in its molten state at 300°C. The reactive processing of the MDI‐treated PPS with maleic anhydride‐modified PPE gave a PPS/PPE alloy with micro‐dispersed PPE in the PPS matrix. The PPS/PPE alloy showed mechanical properties superior to those of PPS at elevated temperature (150°C) and also showed precision‐molding ability superior to that of PPS.     

苯乙烯—异戊二烯—苯乙烯热塑性嵌段共聚物

简介近年来国外SIS生产状况、生产工艺技术经济评估、SIS的基本性能和应用以及国外技术发展趋势,井对国内SIS产品开发作出预估。     

Poly(alkylnylstannanes)

Summary The synthesis of poly(alkynylstannanes) was achieved by the step-growth polymerization of bisaminostannanes and ,-diynes. This is a new class of organotin polymers containing tin-alkyne linkages in the polymer backbone. The polymers were obtained in good yield, albeit with relatively low molecular weight. The polymers underwent crosslinking on standing to give insoluble material and required stabilization with radical inhibitors. The thermal properties of these materials, and the influence of the group pendent to tin are discussed.     

Poly(ortho-vinylbenzophenone)

This article reports the synthesis and free radical polymerization of ortho-vinylbenzophenone. The glass transition temperature T_g of the homopolymer is 136°C. The products synthesized appeared to be atactic and amorphous. The Mark-Houwink constants for poly (o-vinylbenzophenone) in tetrahydrofuran are K = 4.2 × 10^?2 cm³ g^?1 and a = 0.765. The pre-exponential constant under theta conditions, K_θ, is estimated to be 5.93 × 10^?2 cm³ g^?1. The ratio of unperturbed dimensions of the actual polymer and free rotating analogue chain is 3.93, which is almost double that of polystyrene. The Flory-Huggins interaction parameter for poly $\text{(o-}\text{vinylbenzophenone}\text{)}\text{tetrahydrofuran}$ is 0.48 at room temperature. The $\text{k}{}_{\mathrm{<mtext>p</mtext>}}\text{k}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}_{\mathrm{<mtext>t</mtext>}}$ ratio at 60°C is $\text{1.1 × 10}{}^{\mathrm{?2}}\text{l}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{mol}{}^{\mathrm{<mtext>?1</mtext><mtext>2</mtext>}}\text{s}{}^{\mathrm{<mtext>?1</mtext><mtext>2</mtext>}}$. In free radical copolymerizations with styrene at 70°C, r₁ (o-vinylbenzophenone) = 1.216, r₂ = 0.751. This copolymerizations is virtually random.     

聚乳酸/聚丁二酸丁二醇酯共混物的研究

通过熔融共混制备了聚乳酸(PLA)/聚丁二酸丁二醇酯(PBS)共混物,采用扫描电子显微镜、差示扫描量热仪、旋转流变仪对其相容性、热性能和黏度等进行了研究,并研究了PBS的加入对PLA力学性能的影响。结果表明,PLA和PBS之间是部分相容的,PBS的少量添加并不影响PLA的拉伸强度,且其冲击强度随着PBS含量的增加呈先上升后下降的趋势,当PBS含量为10份时,共混物的冲击强度最好;与纯PLA相比,共混物的黏度有所增加,且随着PBS含量的增加,共混物的黏度逐渐增大;PBS的添加起到异相成核作用,促进了PLA的结晶。     

New Miscible Poly(ether imide)/Poly(phenyl sulfone) Blends

Summary: Blends of PEI and PPSU were prepared directly during the plasticization step of an injection molding process throughout the full composition range. The molded blends were transparent and showed a single glass transition and no dispersed phase by SEM. These characteristics did not allow the presence of a single miscibilized phase to be inferred unambiguously due to the very similar T_gs and refractive indices of the two components of the blends. Miscibility was inferred after close observation of the position, height and area of the enthalpy relaxation peak of the 50/50 blend. The modulus of elasticity and yield stress changed linearly with composition, leading to polymer materials with intermediate characteristics. The linearity was attributed to the lack of decrease in free volume induced by mixing and to the similar orientation of the components before and after mixing. The PPSU presence only slightly reduced the known tendency towards brittle fracture of PEI under notched impact conditions, but the presence of a single amorphous phase led to an expected ductile behavior of the blends close to that predicted by the single rule of mixtures.

Break stress (?) and break strain (○) of PEI/PPSU blends as a function of composition.     

聚β-羟基丁酸酯和聚碳酸亚丙酯的共混体系研究

采用溶剂挥发法和熔融共混法分别制备了聚β-羟基丁酸酯(PHB)和聚碳酸亚丙酯(PPC)的共混物,采用DSC、X-射线衍射、扫描电镜、偏光显微镜等手段系统研究了共混物配比对体系热、力学性能、形貌的影响.结果表明,随着共混物中PHB含量的增加,共混物断裂强度增大,PPC的加入可明显改善材料脆性,断裂伸长率增大.PPC的存在可以抑制PHB的结晶过程,降低PHB的熔点,拓宽PHB的熔融加工窗口.上述共混物在可降解塑料领域具有良好的应用前景.     

聚羟基烷酸酯改性聚氯乙烯的研究

通过熔融共混的方法分别制备了聚氯乙烯/邻苯二甲酸二辛酯/聚羟基烷酸酯（PVC/DOP/PHA）和PVC/PHA共混物。研究了PHA逐步代替DOP对共混物力学性能和熔体流动性能的影响规律,利用扫描电子显微镜对所制备的试样进行微观结构分析。结果表明,随着共混体系中PHA用量的增加和DOP的等量减少,与PVC/DOP共混物相比,PVC/DOP/PHA共混物的拉伸强度由21 MPa提高至42 MPa,断裂伸长率先增加而后降低,在PHA含量为10.7 %(质量分数,下同)时出现极大值(350 %);在PVC/PHA体系中,PHA含量增加,PVC/PHA共混物的力学性能及熔体流动速率都显著提高,说明PHA可以作为PVC的一种有效的绿色增塑剂和增韧剂。     

A Novel Quaternary Blend System of Poly(ethy1ene terephthalate), Poly(trimethy1ene terephthalate), Poly(butylene terephthalate), and Poly(ether imide)

Summary A quaternary blend system composed of three low-T_g semi-crystalline aryl-polyesters namely, [poly(ethylene terephthalate) (PET), poly(trimethylene terephthalate) (PTT), and poli(butylene terephthalate) (PBT)] and an amorphous high-T_g poly(ether imide) (PEI) was prepared and investigated using thermal and morphology characterization techniques. This study, for the first time, demonstrated miscibility and phase behavior of a quaternary blend comprising four different polymers. A single and composition-dependent T_g was found for each of all quaternary blend samples. In addition, various thermal transition characteristics, single and composition-dependent T_c,c, increasingly suppressed ΔH_c,c at higher PEI contents, are also indication of phase miscibility of the quaternary blend. SEM morphology characterization (3000X) revealed no discernible domains and homogeneous phase morphology in the quaternary blends was also substantiated using optical and scanning electron microscopy results. Received: 14 November 2002/Revised version: 17 February 2003/ Accepted: 22 February 2003 Correspondence to Eamor M. Woo     

Thermal Behavior of Isotactic Poly(propylene)/Maleated Poly(propylene) Blends

This paper analyzes the thermal and thermo‐oxidative degradation behavior, phase separation, melting, and crystallization of blends consisting of isotactic poly(propylene) (IPP) and poly(propylene) grafted with maleic anhydride (PP‐g‐MA). It has been established that, depending on the blend composition and crystallization/preparation procedure, the blends of IPP and PP‐g‐MA can either co‐crystallize or evidence phase separation. This conclusion has been attained by comparing the DSC results of crystallization under dynamic and isothermal conditions with X‐ray diffraction results. On the basis of the obtained results, the optimum mixing ratios have been established as 95–85 wt.‐% IPP/5–15 wt.‐% PP‐g‐MA. Thermo‐oxidative behavior has been studied by thermogravimetry and differential thermal analysis.