非晶态聚对苯二甲酸乙二酯膜应力屈服机制的示差扫描量热研究

采用示差扫描量热法、应力应变测量研究了物理老化对非晶态聚对苯二甲酸乙二酯（ＰＥＴ）膜单轴拉伸过程中应力屈服行为的影响．结果表明，非晶高聚物经物理老化后屈服应力，应力屈服峰及热焓吸热峰均增大；屈服前后的ＤＳＣ结果表明，经过屈服点后试样热焓吸热峰消失，屈服后的试样经物理老化后，应力屈服峰又再现．从凝聚缠结的观点解释了非晶高聚物物理老化和应力屈服的本质．     

聚苯基单醚喹噁啉薄膜的性能与物理老化

研究了物理老化对聚苯基单醚喹啉薄膜的结构与力学性能的影响 .用差示扫描量热计 (DSC)及正电子湮没寿命谱 (PALS)方法表征了两种不同物理老化条件试样的凝聚结构以及自由体积的差别 .结果表明 ,物理老化使聚苯基单醚喹啉薄膜玻璃化转变温度移向高温 ,在其末端出现热焓吸收峰 ,分子链堆砌紧密使自由体积减小 ,分子可动性降低 .用动态力学分析 (DMTA)以及静态拉伸性能测试等方法研究了两类试样的力学性能 ,结果表明 ,物理老化后 ,试样的动态储能模量稍有增加 ,力学损耗降低 .而静态拉伸实验的断裂应变降低 ,屈服应力增加 ,断裂能降低 ,试样在宏观上由韧性断裂变为明显的脆性断裂 .     

物理老化对PEK-C、PES-C及其复合材料的玻璃化转变热焓松弛特征的影响

本文用DSC技术研究了物理老化对PEK-C、PES-C及其共混物和复合材料玻璃化转变的影响.老化时间(t)延长,玻璃化转变温度(T_g)、热焓松弛峰温(T_(max))、峰高(△C_(pmax))和热焓(△H)提高;△H与lgt成线性关系.碳黑或碳纤维对PES-C的物理老化行为无影响,而反应性乙炔端基砜(ATS)固化物能限制PEK-C和PES-C在T_g以下温度的物理老化过程.利用物理老化能更为方便地判断多相体系的相容性,结果表明PEK-C/PSF为相容体系,而PEK-C/PES-C相容性较差.     

物理老化对PEK-C、PES-C及其复合材料的玻璃化转变热焓松弛特征的影响

 本文用DSC技术研究了物理老化对PEK-C、PES-C及其共混物和复合材料玻璃化转变的影响.老化时间(t)延长,玻璃化转变温度(T_g)、热焓松弛峰温(T_max)、峰高(△C_pmax)和热焓(△H)提高;△H与lgt成线性关系.碳黑或碳纤维对PES-C的物理老化行为无影响,而反应性乙炔端基砜(ATS)固化物能限制PEK-C和PES-C在T_g以下温度的物理老化过程.利用物理老化能更为方便地判断多相体系的相容性,结果表明PEK-C/PSF为相容体系,而PEK-C/PES-C相容性较差.     

取向对物理老化的聚对苯二甲酸乙二酯纤维溶剂诱导结晶速率的影响

通过密度法、ＤＳＣ、力学性能测试等方法研究了物理老化对聚对苯二甲酸乙二酯（ＰＥＴ）纤维溶剂诱导结晶速率及结构的影响，并进一步探讨了取向程度对ＰＥＴ纤维物理老化过程的影响．发现在一定老化温度下，ＰＥＴ纤维的溶剂诱导结晶（ＳＩＮＣ）速率随老化时间的延长呈现先降低后升高的趋势；取向程度高的样品则经较短的老化时间即可出现这种情况．对上述现象用凝聚缠结的观点加以解释．     

水热老化对含钯La0．9Sr0．1CoO3－δ／α－A12O3催化性能的影响

以浸渍法制备了α-A12O3负载的含钯La0．9Sr0．1CoO3-δ钙钛矿样品，探讨了水热老化对样品催化CO-NO反应性能的影响，并以XRD，TPR和XPS等对样品在水热老化前后的结构进行了表征．结果表明，钯的引入方式直接影响样品的水热性能．掺钯样品(LaSrCoPd)具有良好的水热性能，经水热老化后，其催化活性显著提高，显示出最好的催化性能；样品中钯离子位于钙钛矿晶相内，形成α-A12O3负载的La0．9Sr0．1Co0.95Pd0.05O3-δ,La0．9Sr0．1CoO3-δ／α-A12O3负载钯的样品(Pd／LaSrCo)具有最高的初活性，但经水热老化后，其催化活性明显降低在水热老化过程中，La0．9Sr0．1CoO3-δ钙钛矿的结构稳定，但含钯钙钛矿晶相中的钯离子迁移聚集成独立的PdO颗粒，较小的PdO颗粒聚集成较大的颗粒．水热老化后，Pd／LaSrCo样品表面裸露的钯原子数目减少．导致其催化活性降低；而LaSrCoPd样品表面裸露的钯原子数目增多，导致其催化活性升高．     

水热老化对含钯La0．9Sr0．1CoO3－δ／α－Al2O3催化性能的影响

 以浸渍法制备了α－Al2O3负载的含钯La0．9Sr0．1CoO3－δ钙钛矿样品，探讨了水热老化对样品催化CO－NO反应性能的影响，并以XRD，TPR和XPS等对样品在水热老化前后的结构进行了表征．结果表明，钯的引入方式直接影响样品的水热性能．掺钯样品（LaSrCoPd）具有良好的水热性能，经水热老化后，其催化活性显著提高，显示出最好的催化性能；样品中钯离子位于钙钛矿晶相内，形成α－Al2O3负载的La0．9Sr0．1Co0．95Pd0．05O3－δ．La0．9Sr0．1CoO3－δ／α－Al2O3负载钯的样品（Pd／LaSrCo）具有最高的初活性，但经水热老化后，其催化活性明显降低．在水热老化过程中，La0．9Sr0．1CoO3－δ钙钛矿的结构稳定，但含钯钙钛矿晶相中的钯离子迁移聚集成独立的PdO颗粒，较小的PdO颗粒聚集成较大的颗粒．水热老化后，Pd／LaSrCo样品表面裸露的钯原子数目减少，导致其催化活性降低；而LaSrCoPd样品表面裸露的钯原子数目增多，导致其催化活性升高．     

用调制式差示扫描量热法表征尼龙6和聚乳酸升温热行为

用调制式差示扫描量热法(MDSC)表征尼龙6和聚乳酸升温过程热行为，MDSC把总热流分解成可逆热流ΔHrev和不可逆热流ΔHnon;实验结果表明纯尼龙及其共混体系升温熔融过程中包含了可逆放热峰；共混体系不同，可逆热流ΔHrev不同，都比纯尼龙小；纯尼龙可逆热流ΔHrev随调制周期延长而增大；聚乳酸玻璃化转变区，随老化时间的延长和老化温度的提高，玻璃化转变温度Tg提高，松弛热焓增大。     

聚芳醚酮高温长时间下的断裂行为──2．物理老化的影响

研究了聚芳醚酮在２００℃下长时间放置过程中的密度，热焓，屈服及应力松弛行为随时间的变化规律．结果表明，随放置时间的增长，材料的结构形态与物性随时间的变化速率在１０小时后急剧减慢．文中对物性变化的时间依赖性进行了讨论．在应力松弛过程中出现银纹的现象可归结为物理老化过程中分子链间排列逐渐紧密的结果．     

DSC曲线各特征点的物理意义以及相变热焓的广义Speil公式的推导

按目前差示扫描量热法（DSC）公认的Gray－Speil理论，由于对实际的过程过于简化，以致不能很好地解释DSC曲线上的每个特征点；就相变前后试样的热容量发生改变的普遍情况下，如何定量计算相变潜热，目前尚未有严格的计算理论。本文对差示扫描量热法的基本理论做了一些较深入的探索，通过考虑容器及试样内存在温度梯度这一实际情况，成功地解释了实际DSC曲线上各个特征点具体的物理意义，并就相变前后试样的热容量发生变化且热容量是温度的函数这一普遍情况，推广出广义的Speil公式和热焓计算的普遍法则，得到了与实验更加接近的结果。     

物理老化对聚乳酸玻璃化转变行为的影响

为考察不同链结构的聚乳酸在物理老化过程中聚集态结构的变化 ,分别在 0℃、2 5℃、37℃对聚 (D ,L 乳酸 ) (PDLLA)、非晶态的低左旋度聚 (L 丙交酯 ) (l PLLA)和左旋聚 (L 丙交酯 ) (PLLA)进行长达 6个月的物理老化 ,用温度调制式差示扫描量热法 (MDSC)研究了它们在物理老化过程中的玻璃化转变行为的变化 .结果表明 ,PDLLA和l PLLA对物理老化十分敏感 ,在一定老化温度下 ,它们的玻璃化转变温度 (Tg)随老化时间延长向高温移动 ,老化过程中产生的非可逆热焓 (ΔHnon)逐渐增加 ,这种趋势在老化 1w内变化明显 ,随后趋缓 ;而老化温度越高 ,Tg 升高和ΔHnon增加的速率都越快 .不同温度下老化 ,PDLLA和l PLLA的ΔHnon 与老化时间的对数都有较好的线性关系 ,ΔHnon的变化速率对温度的倒数作图 ,l PLLA的斜率绝对值比PDLLA的略大 ,说明有较高立构规整性的分子链形成物理缠结需要较高的活化能 .PLLA由于结晶度高而非晶相含量较低 ,未观察到明显的玻璃化转变及其在物理老化过程中的变化 .     

ON THE ORIGIN OF STRESS PEAK IN UNI-AXIAL STRETCHING OF AMORPHOUS POLYMERS

Rubber of high molar mass, like cis-polybutadiene, shows a stress peak on theenineering stress-strain curve during stretching at room temperature. In this work cis-polybutadiene samples were swollen in a poor solvent, CHCl_3/EtOH (1/1 v/v), for differenttimes. It was found that both the initial modulus and the stress peak on stretching de-creased in magnitude with increasing swelling time and the peak disappeared entirely after1 hour of swelling. On further swelling the initial modulus increased somewhat and a smallstress peak re-appeared after swelling for 2 h. The disappearance of the stress peak afterswelling is interpreted as the result of disruption of cohesional entanglements present in theinitial rubber sample. The re-appearance of a small stress peak and the increase of modu-lus on further swelling are interpreted as being of the same nature as the phenomenon ofanti-plasticization. It is the result of forming some new cohesional entanglements of largerbinding energies through longer range chain segmental motions excited after the disruptionof the previously existing cohesional entanglements in the rubber. Thus an understand-ing of the stress peak on stretching a high molar mass rubber and the phenomenon ofanti-plasticization on molecular level has been put forward.     

从溶胀平衡研究玻璃态高聚物的凝聚缠结网络

在13~15℃室温条件下对聚苯乙烯(PS)颗粒在二氧六环/水混合溶剂中的溶胀情况进行目视观察,可以看到,当减小混合溶剂二氧六环/水中的水含量时,PS颗粒从玻璃态到溶胀的玻璃态、溶胀的高弹态、流体态的转变,与PS颗粒升温时从玻璃态到高弹态、流体态的转变相对应.选定混合溶剂二氧六环/水(水6·8wt%)对一个单分散PS试样(Mw=1·68×105)在30℃进行分相平衡和溶胀平衡的测定.分相平衡是先将PS/二氧六环/水(混合溶剂水含量6·8wt%)体系加热到130℃使PS溶解成一均相溶液,然后在冷却过程中分相,在30℃达分相平衡(30天)时,浓相高分子体积浓度p″=0·304,稀相几乎为纯溶剂.从Flory-Huggins相平衡理论得出此体系的高分子-溶剂相互作用参数χ=0·63.本工作使用的单分散PS试样在选定的混合溶剂,即二氧六环/水(水6·8wt%)中,30℃时不能溶解只能溶胀,单分散PS颗粒淬冷试样(密度ρp=1·0451g/mL)到达溶胀平衡(80天)时浓相高分子体积浓度p″=0·308.而此淬冷试样经在80℃热处理100h后的老化试样(ρp=1·0470g/mL)达溶胀平衡(70天)时p″=0·312.从溶胀过程中浓相体积变化曲线可知试样经在80℃热处理过程中凝聚网络趋向于更均一,更接近热处理温度下的平衡态,试样密度增大,网络产生了新的链间凝聚,物理交联密度增大(凝聚点间分子量减小).从溶胀平衡理论并取χ=0·63(分相平衡)可得到淬冷试样的物理交联点间分子量Mc=11·6×104,老化试样的物理交联点间分子量Mc=6·9×104.实验结果说明溶胀过程及溶胀平衡的测定可以反映玻璃态高聚物中的凝聚网络结构的细节,而且非常敏感.     

THE EFFECT OF HOT DRAWN ON THE PHYSICAL AGING OF ATACTIC POLYSTYRENE

The physical aging behavior of atactic polystyrene (aPS) films achievedunder different drawing conditions has been studied by optical birefringence and modulatedifferential scanning calorimeter (m.d.s.c.). The results show that on annealing at specifictemperature below glass transition temperatue (T_g), the enthalpy relaxation (△H) and T_gdecrease with increasing of birefringence (△n). On the other hand, the effect of moleculardraw ratio (MDR) is confusing: △H and T_g decrease with increasing of MDR in the earlystage of aging, but the MDR's effect become unobvious with the development of aging.It may be concluded that the ordered domain generated by the drawing below or aboveglass transition temperature will affect the development of physical aging behavior. Theviewpoint of cohesional entanglement is used to account for the above observations.     

SEM OBSERVATION OF THE CRAZING FOR POLYPHENYLQUINOXALINE FILMS DURING IN SITU STRETCHING*

The crazing of polyphenylquinoxaline (PPQ-E) films during in situ stretching has been observedby SEM. The crazing phenomena and craze morphology of PPQ-E films were interpreted. The strain values atcritical crazing and yielding and the craze stability of PPQ-E samples depend on the thermal-dealingcondition for the samples. From the point of view of cohesional entanglements and energy absorbed bysamples, the experiment results were explained.     

Study of the dissolution process of polystyrene in concentrated cyclohexane solution by MNR relaxation

 ¹³C-NMR relaxation times of polystyrene (PS) chains in its theta solvent, cyclohexane, have been measured at different temperatures. It was found that relaxation of carbon nuclei of the side-chain-phenyl groups and those of main chains have remarkably different temperature-dependent relaxation behaviors in the solvent. A two-step model for the dissolution process is proposed. According to the model, swelling of the polymer below θ temperature corresponds mainly to the gradual dispersion of the side-chain phenyl groups; while the complete dissolution above θ temperature corresponds mainly to the gradual dispersion of the main chains at a molecular level. These dispersions reflect the fact that cohesional interaction among side-chain-phenyl rings or main chains are weakened by solvent molecules, which shows the existence of the cohesional entanglements among polymer chains. The results of T ₁(C) are confirmed by the biexponential dependence of ¹H-NMR spin–spin relaxation on temperature. Received: 2 July 1997 Accepted: 21 October 1997     

INVESTIGATION OF THE FRIEDEL-CRAFTS REACTION OF THE CHLOROMETHYLATED COPOLYMER OF STYRENE-DIVINYLBENZENE

In the presence of Friedel-Crafts catalyst, the chloromethylated copolymer of styrene-divinylben-zene may react with each other and cross-link by itself Thus a new type of polymeric adsorbent wasobtained, and its structure was identified by its physical properties and infrared spectra. The Friedel-Crafts reaction is manifestly affected by the nature of the solvent, the kind and amount of catalystused, reaction temperature and reaction time, etc. The porous structure and physical properties of the adsorbent prepared have been investigatedsystematically. The adsorbent has high specific surface area (1000--1300m~2/g), porosity, narrowpore distribution,high skeleton density and good mechanical properties.     

Study of entangled network formation in concentrated solutions of polymer by ~(13)C NMR

Information about the exact location of topological and cohesional entanglements at molecular level has been obtained by 13C NMR relaxation analysis. The results show that about 20% of the carbon atoms in the main chain are entangled in the 25% (by weight) solution, which is independent of the content of the 1,2-segment in polybutadiene and of the kind of solvent. However, the entanglement of the carbon atone on the end group of the side chain is very weak, they behave as slipping freely at the junctions.