EFFECTS OF PHENOL RESIN ADDITIVE ON DYNAMIC MECHANICAL PROPERTIES OF ACRYLATE RUBBER AND ITS BLENDS*

The dynamic mechanical properties of a new blend system consisting of phenol resin and polar polymer (acrylaterubber and/or chlorinated polypropylene) were investigated. It was found that the addition of phenol resin to acrylate rubberand its incompatible blend can cause a remarkable improvement in the temperature dependence of the loss tangent. As a result, the present blends are very good damping materials.     

EFFECT OF PAN-MILLING ON RHEOLOGICAL PROPERTIES OF HIGH DENSITY POLYETHYLENE*

The effect of pan-milling on the rheological properties of high density polyethylene (HDPE) was studied. Aninnovative milling apparatus, viz. an inlaid pan-mill, was used. Melt indexer, capillary rheometer, Haake Rheocord 90 single-screw extruder and Brabender rheometer were used to evaluate the rheologieal properties of HDPE. HDPE with higher initialmolecular weight and larger particle size was easier to degrade under pan-milling stress, as indicated by the melt index.Pressure oscillation in capillary flow occurred at significantly higher shear stress and shear rate for milled HDPE than forunmilled HDPE. The apparent shear viscosity of HDPE decreased with increasing times of milling. After milling, the flowactivation energy decreased and thus the sensitivity of viscosity to temperature was reduced. Die pressure and torque duringsingle screw extrusion were reduced significantly after milling. Plasticizing time as measured in a Brabander mixer decreasedmarkedly with increasing milling times.     

DYNAMIC MECHANICAL RESPONSE OF CRAZES IN POLYSTYRENE

Dynamic mechanical analysis was used to study the mechanical properties and microstructureof crazes in polystyrene produced in air or in methanol at different temperatures. A new loss peakwas found at about 82℃,which is assigned to glass transition peak of craze fibrils. The decreaseof glass transition temperature of polymer in craze fibrils is due to the high values of surface tovolume ratio. The glass transition temperature ratio of craze fibrils to bulk material (T_g~l /Tg) hasbeen expressed as a function of the fibrils diameter (d). From T_g~l of craze fibrils,the value of fibrildiameter can be calculated. Annealing the crazed specimen at room temperature makes the fibrilsplastically deform and cause the fibrils to thin slightly,whereas annealing the crazed specimen atthe temperature near T_g of the craze fibrils makes the fibrils bundle together.     

脂肪族水性聚氨酯的动态力学行为研究

合成了一系列脂肪族水性聚氨酯 .考察了软段的组成、软段分子量及DMPA用量对产物动态力学性能的影响作用 .实验结果表明 ,软段的化学结构对水性聚氨酯的相态结构影响很大 .聚醚型水性聚氨酯具有较低的软段玻璃化转变温度 (Tgs) .聚醚型产物的微相分离程度高于聚酯型产物 .当采用聚酯和聚醚二元醇为混合软段时 ,Tgs随软段中聚醚含量的提高而逐渐降低 .提高DMPA用量 ,软段玻璃化转变温度Tgs移向低温区 ,硬段玻璃化转变温度Tgh移向高温区 ,说明体系的微相分离程度加大 .当软段分子量较低时 ,产物为半相容结构 ,只有一个主转变峰 ,软段的玻璃化转变以肩峰的形式出现 ;当软段分子量较高时 ,产物的微相分离程度较高 ,可以分别观察到软段及硬段的玻璃化转变 .总之 ,通过改变软段的种类、组成和分子量以及DMPA用量 ,可以大幅度地改变水性聚氨酯的形态结构 .     

EFFECT OF PAN-MILLING STRESS ON CRYSTAL STRUCTURES OF HIGH DENSITY POLYETHYLENE

A detailed study was performed on the crystal structures of pan-milled high-density polyethylene (HDPE) usingdifferential scanning calorimetry (DSC) and X-ray diffraction. The crystallinity of HDPE first decreased slightly, followed bya gradual increase with increasing milling times. Monoclinic crystals appeared after 4 cycles of milling. With increasingtimes of milling, the proportion of monoclinic crystals increased significantly while the proportion of orthorhombic crystalsdecreased gradually. With increasing times of milling, the crystallite size of orthorhombic form decreased greatly, while thesize of monoclinic crystallites kept almost constant during milling.     

PPESK/PES共混物热性能及动态机械性能研究

采用熔融共混法制备了不同重量比例的新型含二氮杂萘酮结构聚芳醚砜酮(PPESK)与聚醚砜(PES)共混物.利用热失重(TGA)及动态热机械仪(DMTA)对该共混物的热性能及动态机械性能进行了研究.研究结果表明,在氮气氛围中,PPESK热分解分为两步反应进行,反应级数n=1,说明PPESK在氮气氛围中的热分解反应类型与β(升温速率)无关而与材料物性有关;采用Ozawa方法得出在15%热失重前,热分解活化能的平均值为240 kJ/mol;随着升温速率的提高,PPESK热降解速率有减缓趋势.在280℃以前,PPESK储能模量值随温度变化较小,保持在较高值,温度在280~330℃之间,储能模量值降低幅度突变.另外,PPESK中加入PES会降低其储能模量值及其热稳定性.     

双组份网状共聚物的动态力学性质

本文研究了端乙烯基聚氨酯预聚物(VTPU)同乙烯类单体甲基丙烯酸甲酯(MMA)、苯乙烯(St)、醋酸乙烯酯(VAc)、和甲基丙烯酸丁酯(BMA)聚合得到的双组份网状共聚物(BCN′s)的动态力学性能及形态结构。四种BCN′s试样两组份在动态力学谱上均有半相容的特征。体系的交联密度增大,混合熵增加,相容性改善,试样中可溶性组份含量随BCN′s的组成而变化。溶胶组份可改善体系中两组份的相容性。     

STUDIES ON THE NATURE OF THE MACROMOLECULAR CONDENSED STATE OF "NASCENT" ULTRA HIGH MOLAR MASS POLYETHYLENE*

 Ultra high molar mass polyethylene (UITPE) powder as polymerized in a slurry process has been studied, in its nascent state, after recrystallization on rapid cooling from the melt and after hot compression molding to a film, by DSC,effect ofannealing the recrystallized specimen at 120～I30℃, morphology by polarizing optical microscopy and small angle X-ray scattering. Based on the experimental results obtained the macromolecular condensed state of the nascent UHPE powder is a rare case of a multi-chain condensed state of non-interpenetrating chains, involving interlaced extended chain crystalline layers and relaxed parallel chain amorphous layers. On melting, a nematic rubbery state of nanometer size domain resulted. The nematic-isotropic transition temperature was judged from literature data to be at least 220℃, possibly higher than 300℃, the exact temperature is however not sure because of chain degradation at such high temperatures. The recrystallization process from the melt is a crystallization from a nematic rubbery state. The drop of remelting peak temperature by 10 K of the specimen recrystallized from its melt as compared to the nascent state has its origin in the decrease both of the crystalline chain stem length and of the degree of crystallinity. The remelting peak temperature could be returned close to that of the nascent state by annealing at 120～130℃.     

THE EFFECTS OF HINDERED AMINES ON METHYL METHACRYLATE POLYMERIZATION

The effects of hindered amines, such as TMP, TMPM, TUV-770, on MMA and St homopoly-merization have been studied. It was found that in the MMA polymerization initiated with BPO orAIBN, the presence of TMPM, TUV-770 prolonged the induction period and a little change on R_p wasobserved. However, in the presence of TMP R_p increased slightly. The activation energy of poly-merization and polymerization rate equation were determined.     

A DYNAMIC MECHANICAL ANALYSIS STUDY OF THE TRANSITION BEHAVIOUR OF I-PP/EPDM BLENDS

The transition behaviour of the blends of isotactic polypropylene (i-PP) with ethylene-propylene terpolymer (EPDM) containing 42 wt% propylene was investigated by dynamic mechanical analysis technique (DMA). Owing to its high propylene content, EPDM is compatible with i-PP to some degree. The interaction between the two components was strengthened. As expected, for partially compatible system the glass transition temperature of i-PP in the blends shifted to lower temperature. It was found that there existed two transitions, αEPDM and βEPDM, for the EPDM used in this work. The former was considered to be the glass transition of the random chain segments of EPDM, while the latter the local motion of the long ethylene sequences in EPDM. The unusual transition behaviour of αEPDM in the blends was explained in terms of the greater thermal expansion of EPDM and the compatibility of the two components. On the other hand, the βEPDM changed with the composition of the blends in a regular manner.     

A STUDY ON MECHANICAL PROPERTIES OF γ-RAY IRRADIATED HDPE FILLED WITH SERICITE-TRIDYMITE-CRISTOBALITE*

The effect of γ-ray irradiation on the mechanical properties of high densitypolyethylene(HDPE) filled with sericite-tridymite-cristobalite(STC) was studied. The ex-perimental results show that γ-ray irradiation can improve the affinity between HDPE andSTC, and the dispersion of STC in HDPE matrix. Compared with HDPE/STC (80/20)blend, the yield stress and impact strength of irradiated HDPE (10kGy)/STC (80/20) blendare increased from 22.8 MPa and 70J/m to 28.5 MPa and 144J/m. The yield stress andimpact strength of HDPE/irradiated HDPE/STC (48/32/20) are 27.8MPa and 210J/m,respectively.     

EFFECTS OF CHAIN STRUCTURE OF POLYPYRROLONES ON THE ELECTRICAL PROPERTIES OF PYROLYZED POLYPYRROLONES

Three kinds of polypyrrolones (PMDA-DAB, PMDA-TADPE and DEDA-DAB) werepyrolyzed at high temperature in order to study the effect of the chain structure of polypyrro-lones on the electrical properties of the pyrolyzed polymers. Results show that the num-ber of fusing rings in the main chain of polymers has a little effect on the pyrolysis pro-cess, whereas, the ether bond in the main chain plays an important role during pyrolysis.Structure characterizations by elemental analyis, XPS spectra, X-ray diffraction and SEMimages indicate that because the ether bond is easy to break, it is difficult to form largearea planar network. This hampers the formation of the graphite-like structure in thepolypyrrolones containing ether bond even after being pyrolyzed at 1200℃.     

ELECTRICAL AND MECHANICAL PROPERTIES OF POLYANILINE FILMS——EFFECT OF NEUTRAL SALTS ADDED DURING POLYMERIZATION*

The electrical and mechanical properties of polyaniline (PANI) films syn-thesized by the presence of the selected neutral salts in the polymerization were measuredas a function of the properties and the concentration of the selected neutral salts, andthe protonation state. It was found that both the electrical and mechanical properties ofPANI films were enhanced by adding neutral salts in the polymerization. The adding ofthe neutral salts in the polymerization resulted in extended conformation of polymer chainand increasing of molecular weight of PANI, which may be the reasons why the electricaland mechanical properties of PANI films were improved by the presence of neutral salts inthe polymerization.     

氯化聚乙烯对甲基丙烯酸甲酯／苯乙烯共聚动力学的影响

将甲基丙烯酸甲酯（ＭＭＡ）／苯乙烯（Ｓ）在氯化聚乙烯（ＣＰＥ）存在下进行悬浮溶胀接枝共聚，考察了ＣＰＥ对ＭＭＡ／Ｓ共聚动力学行为的影响．ＣＰＥ提高了聚合体系的粘度，使自动加速提前，扩散因素增加，对共聚有阻滞作用．ＣＰＥ是链转移剂，使ＭＭＡ／Ｓ共聚物分子量降低．ＣＰＥ对ＭＭＡ的吸附渗透优于对Ｓ的吸附，造成接技部分与非接技部分组成的差异．ＣＰＥ含量、溶胀时间、转化率、硫酸用量对共聚组成均有影响。     

聚丙烯／氯化聚乙烯共混物的形态结构

用透射电子显微镜方法研究了聚丙烯（ｉＰＰ）和氯化聚乙烯（ＣＰＥ）共混物溶液浇铸膜的形态结构．共混物中ＣＰＥ含量≤７０％时不妨碍ｉＰＰ球晶两种结构（交叉结构和条状结构）区域的生成．在ＣＰＥ含量≥８０％时，分散相ｉＰＰ形成近乎直角（８０°）交叉的稀疏的片晶网络．在共混物的全组成范围内，ＣＰＥ结晶在ｉＰＰ片晶上附生生长，二者结晶Ｃ轴的交角为５０°     

EFFECTS OF COMPATIBILIZERS ON THE MECHANICAL PROPERTIES OF LOW DENSITY POLYETHYLENE/LIGNIN BLENDS

Low density polyethylene(LDPE)/lignin blends were prepared using melt blending.Two kinds of compatibilizers, ethylene-vinylacetate(EVA) which is softer than LDPE and polyethylene grafted with maleic anhydride(PE-g-MA) which is harder than LDPE were used to improve the interfacial adhesion.Scanning electron microscope(SEM) was used to investigate the dispersion of lignin in LDPE matrix.The results showed that both of the compatibilizers could improve the interaction between the low density polyethylene an...     

SILICA-SUPPORTED NICKEL AND ZIRCONIUM CATALYSTS FOR BRANCHED POLYETHYLENE*

8-Aminoquinoline nickel dichloride and bis(cyclopentadienyl)zirconium dichloride (Cp_2ZrCl_2) were supportedsimultaneously on silica to produce branched polyethylene successfully by combined polymerization. The supportedpolymerization results showed that the molecular weight of polyethylene increased while the molecular weight distributionbecame wider and the molecular chains of oligomers remaning in the final solution became shorter as compared to theoligomers obtained in polymerization processes with pure 8-aminoquinoline nickel dichloride catalysis, as well as theCp_2ZrCl_2 and nickel combination system. With decreasing amount of Ni catalyst in the supported catalyst, the molecular chains of oligomers in the resulting solution became shorter, while α-olefin selectivity increased.     

SHAPE MEMORY EFFECT OF SLIGHTLY-CROSSLINKED POLYETHYLENE

A series of slightly crosslinked polyethylenes (SXLPE) was prepared by aone-step method using dicumyl peroxide as crosslinking agent in a Haake Mixer. The gelcontents G (Soxhlet extracted) of the samples are in the range from 5% to 20% by weight.Their shear viscosity, crystallization and melting behavior, dynamic mechanical propertiesand shape recovery effect were systematically investigated in terms of the content of thecrosslinking agent. It shows that under certain experimental conditions the SXLPE's mayexhibit good shape fixation ability and shape memory properties, which are similar to thoseof the commercially available shape memory polyethylenes prepared by gamma-irradiationtechnique. However the shape memory behavior of these samples is not very stable due totheir low crosslinking degree, or gel content. Thus their application is limited in specialcases with fast strain fixing procedures.     

含刚性链节和脲端基聚醚增韧剂改性环氧树脂的研究———反应活性及力学性能

合成了一系列既含环氧丙烷聚醚（ＰＰＧ）柔性间隔基、又含刚性介晶结构单元的端脲基活性改性剂（ＬＣＥＵＰＰＧ），并对其改性环氧树脂Ｅ ５１／双氰双胺（Ｅ ５１／ｄｉｃｙ）体系的固化反应活性、改性剂含量对增韧体系动态力学性能及冲击性能的影响进行了研究．结果表明：ＬＣＥＵＰＰＧ的加入对固化体系具有明显的增韧作用，冲击强度提高了３～７倍；其对Ｅ ５１／ｄｉｃｙ固化反应具有明显的促进作用，可使固化反应表观活化能（Ｅａ）降低５０～７０ＫＪ／ｍｏｌ、固化温度降低３０～４０℃；体系的玻璃化转变温度（Ｔｇ）略有下降，但模量基本不降低或略有升高；β 转变向低温方向移动．     

纳米微晶纤维素对炭黑补强天然橡胶力学性能和动态性能的影响

采用酸水解工业微晶纤维素(MCC)制备纳米微晶纤维素(NCC),将其与天然胶乳共凝沉,混炼时加入炭黑(CB),制备了天然橡胶(NR)/NCC/CB复合材料,研究了NR/NCC/CB和NR/NCC/CB/RH(间苯二酚-六亚甲基四胺络合物)复合材料的力学性能和动态性能,并与NR/CB体系的性能进行对比.结果表明NCC可以均匀分散在天然橡胶基体中,且依拉伸方向取向,随着NCC替代炭黑的份数增加,Payne效应减弱,说明NCC本身并不构成强的填料网络,NR/NCC/CB与NR/CB比较,前者整体的网络化程度减弱,体系的损耗因子变化不大,NCC的加入改善了NR/CB的力学性能和抗屈挠龟裂性能,降低压缩疲劳温升和压缩永久形变,当NCC取代5～20 phr CB后,仍然保持高耐磨炭黑补强天然橡胶的耐磨耗性能.动态力学性能显示NR/NCC/CB的玻璃化转变温度较NR/CB变化不大,0℃的tanδ略有下降的同时60℃的tanδ明显降低.NR/NCC/CB/RH体系的Payne效应较NR/NCC/CB明显减弱,力学性能、抗屈挠龟裂性能和耐磨耗性能进一步改善,体系的压缩疲劳温升和压缩永久形变更小.