Structure and mechanical properties of isotactic polypropylene and iPP/talc blends functionalized by electron beam irradiation

The structure and mechanical properties of isotactic polypropylene (iPP) functionalized by electron beam irradiation are investigated by differential scanning calorimetry, wide‐angle X‐ray diffraction, thermogravimetry, thermomechanical analysis, melt index and mechanical measurements. The experimental results show that the degree of crystallinity, the thermal degradation temperature and the dimensional stability increase with dose in the range 0–5 kGy. At 5 kGy, the initial and final degradation temperatures of the irradiated iPP are raised by 66 °C and 124 °C, respectively. The melt index increases with increasing dose. The mechanical measurements show that the stiffness of iPP is greatly enhanced by electron beam irradiation. A small dose of irradiation (0.75 kGy) can increase the Young's modulus to 1284 MPa compared with 1112 MPa for unirradiated iPP. Adding 10 % by weight of irradiated iPP powder into iPP/talc (70/20 % by weight) blends, changes the processing parameters significantly and makes the Young's modulus rise substantially. At a dose of 40 kGy the Young's modulus of iPP/talc blend jumps to 3611 MPa against the original 2201 MPa. © 2000 Society of Chemical Industry     

Structure and morphology of isotactic polypropylene functionalized by electron beam irradiation

The structure and morphology of isotactic polypropylene (iPP), functionalized by electron beam irradiation at room temperature in air, are investigated by elementary analysis, FT‐infrared (FTIR) spectroscopy, electron spectroscopy for chemical analysis (ESCA), polariscope, and static contact angle. Elementary analysis reveals that the element oxygen has been introduced onto iPP chains after electron beam irradiation. In addition, as shown from FTIR spectra, oxygen‐containing groups, such as carbonyl, carboxyl, and ether groups, are introduced onto iPP molecular chains. The dependence of oxygenation extent (as measured by O_1S/C_1S value of ESCA spectra) on electron beam dose is obtained. Under polariscope, it can be observed that the dominant alpha phase appears to become more enhanced, and there is no crystalline phase transition. The static contact angle of iPP decreases with increasing dose. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 75–82, 2000     

固相氯化法氯化等规聚丙烯结构分析

借助ＤＳＣ,ＩＲ,＾１Ｈ－ＮＭＲ方法对搅拌式固相氯化制备的氯化等规聚丙烯的宏观氯原子分布和微观氯原子分布进行了分析。结果表明,搅拌式固相氯化法能够迅速破坏等规聚丙烯的结晶,从而得到宏观氯原子分布均匀的ＣＩＰＰ。此方法制备的ＣＩＰＰ主要为等丙烯分子链上的仲氢原子被取代的产物。     

高熔体强度聚丙烯树脂的结构与性能

采用差示扫描量热法、傅里叶变换红外光谱、毛细管流变、熔体拉伸等方法,从结晶性、黏弹性及物理机械性能等方面对高熔体强度聚丙烯(HMSPP)树脂进行结构表征与性能分析。结果表明:HMSPP树脂具备较高的弯曲模量,同时具备优异的抗熔垂能力和更宽的加工温度;拉伸黏度随拉伸速率的增大而增大,呈现出HMSPP应变硬化这一明显行为,使得熔体在热成型过程中具有均匀变形的自我调节能力,从而克服普通聚丙烯在热成型加工中的严重熔垂问题;含有较长接枝链段的HMSPP树脂在刚性、熔体强度、结晶性能等方面均优于普通聚丙烯。     

The morphology of irradiated isotactic polypropylene

The research in this article explores the response of semicrystalline isotactic polypropylene to gamma radiation in air, and relates the morphological changes of the polymer to corresponding changes in mechanical properties. The effect of the initial morphology of the polymer on its response to irradiation is considered using infrared spectroscopy (FTIR), small‐ and wide‐angle X‐ray scattering, dynamic mechanical thermal analysis (DMTA), and mechanical testing. The extent of chain scission and crosslinking is dependent on the dose but not the initial starting morphology. These chemical changes cause the crystallinity to increase slightly, and the glass transition temperature to rise by a few degrees in all samples, but the overall morphology is only subtly changed. In contrast, a major deterioration in mechanical properties is caused. The effects of the irradiation observed under these conditions are similar in each material and the ultimate properties determined by the properties seen in the original material. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2234–2242, 1999     

Studies on high density polyethylene (HDPE) functionalized by ultraviolet irradiation and its application

The structure and properties of high density polyethylene (HDPE) functionalized by ultraviolet irradiation at different light intensities in air were studied by electron analysis, FTIR spectroscopy, contact angle with water, differential scanning calorimetry and mechanical properties measurement. The results show that oxygen‐containing groups such as C?O, C—O and C(?O)O were introduced onto the molecular chain of HDPE following irradiation, and the rate and efficiency of HDPE functionalization increased with enhancement of irradiation intensity. After irradiation, the melting temperature, contact angle with water and notched impact strength of HDPE decreased, the degree of crystallinity increased, and their variation amplitude increased with irradiation intensity. Compared with HDPE, the yield strength of HDPE irradiated at lower light intensity (32 W m^?2 and 45 W m^?2) increases monotonically with irradiation time, and the yield strength of HDPE irradiated at higher light intensity (78 W m^?2) increases up to 48 h and then decreased with further increase in irradiation time. The irradiated HDPE behaved as a compatibilizer in HDPE/polycarbonate (PC) blends, and the interface bonding between HDPE and PC was ameliorated. After adding 20 wt% HDPE irradiated at 78 W m^?2 irradiation intensity for 24 h to HDPE/PC blends, the tensile yield strength and notched Izod impact strength of the blend were increased from 26.3 MPa and 51 J m^?1 to 30.2 MPa and 158 J m^?1, respectively. Copyright © 2003 Society of Chemical Industry     

A study of LLDPE functionalized through ultraviolet irradiation and interfacial interaction of PA66/functionalized LLDPE blends

Some oxygen‐containing groups, such as C? O? C, C? OH, C?O, C(?O)O, and C(?O)OH, were introduced onto linear low‐density polyethylene (LLDPE) chains during ultraviolet irradiation under air, without adding any monomers and auxiliaries and without environmental pollution. After ultraviolet irradiation, the molecular weight of LLDPE decreased and its distribution became wider. The melting temperature and crystallinity of irradiated LLDPE decreased with irradiation time. The copolymer LLDPE‐g‐PA66 was formed by reaction between oxygen‐containing groups of irradiated LLDPE and amine or carboxyl end groups and amide linkage of polyamide 66 (PA66) during preparation of PA66/irradiated LLDPE blends. Compared with PA66/LLDPE blend, the mechanical properties of PA66/irradiated LLDPE blends were improved greatly because of the improved interface interaction and dispersion. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Graft copolymerization of methacrylic acid onto isotactic polypropylene by radiochemical methods

Graft copolymerization of methacrylic acid onto isotactic polypropylene has been studied in water–methanol medium using γ-rays as the source of initiation. Graft copolymerization has been conducted by (1) mutual irradiation, (2) preirradiation, and (3) double irradiation methods. All of the reaction parameters that seem to influence grafting have been studied, and the optimum conditions leading to maximum percentage of grafting have been evaluated. A plausible mechanism for radiation-induced grafting of methacrylic acid onto polypropylene has been suggested, and the results have been explained on the basis of the proposed mechanism. A comparative study of graft copolymerization by different radiation methods has been made, and it was observed that the preirradiation method affords the best results. Evidence of grafting has been obtained from differential scanning calorimetric analysis and the dyeing behavior of the grafted material. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 143–152, 1998     

紫外辐射交联改善UHMWPE纤维蠕变性能研究进展

超高分子量聚乙烯(UHMWPE)纤维较差的抗蠕变性能影响了其应用。该文介绍了纤维发生蠕变机理及蠕变行为,综述了采用紫外辐射方法改善UHMWPE纤维蠕变性能的技术进展,并讨论了工艺特点和处理效果。     

Structure and thermal molecular motion at surface of semi-crystalline isotactic polypropylene films

Surface crystalline structure in isotactic polypropylene (iPP) films was explored by in-plane grazing incidence X-ray diffraction measurement. Apparent crystallinity in the surface region was lower than the bulk one. After an etching treatment with a droplet of potassium permanganate solution, a clear crater was formed at the surface, and the step height between etched and intact regions was approximately 3 nm. This means that the iPP surface was covered with 3 nm thick amorphous layer. Then, surface molecular motion in the iPP films was examined by lateral force microscopy. Surface α_a-relaxation process arisen from the segmental motion was observed at about 250 K, and its apparent activation energy was 230±10 kJ mol⁻¹. The both were lower than the corresponding bulk values, indicating that surface molecular motion is more active than the bulk one even in the semi-crystalline iPP films. An iPP film with 1.5 nm thick surface amorphous layer was prepared. In this case, the enhanced mobility was still observed at the surface, but the extent of the enhancement was not remarkable as that for the iPP film with 3 nm thick surface amorphous layer. These results imply that surface mobility is affected by the presence of underneath crystalline phase, if the surface amorphous layer is thin enough.     

抗冲聚丙烯结构与性能研究

对部分国内外抗冲聚丙烯(PP)产品进行了微观形态和结构分析，研究其对材料宏观力学性能的影响。实验结果表明：抗冲PP是一个含有PP均聚物、丙烯与乙烯-丙烯两嵌段共聚物、乙丙橡胶(EPR)、聚乙烯均聚物等的多相体系。EPR的分子序列结构对聚合物抗冲击性能起主要作用。在序列结构中，丙烯、乙烯单体在分子链上的位置交换越频繁，抗冲击性能越得到提高。丙烯序列平均长度的增大对抗冲击性能有一定的削弱作用。     

低能紫外辐照聚丙烯的结构与性能

用低能紫外辐照聚丙烯,在聚丙烯分子链上引入含氧极性基团,改善聚丙烯与填料或其他工程塑料共混的相容性。通过光电子能谱（ＥＳＣＡ）、偏光显微镜、熔体流动速率（ＭＦＲ）仪、接触角和动态粘弹谱（ＤＭＴＡ）仪、毛细管流变仪等近代分析测试,研究了紫外辐照聚丙烯的结构、形态与性能。随紫外辐照时间的增加,聚丙烯的熔体流动速率增加,接触角下降。经过紫外辐照,聚丙烯的结晶形态发生了变化。对比紫外辐照聚丙烯及与绢英粉共     

The effect of some fluoropolymers' structures on their response to UV irradiation

The response of three commercial fluoropolymer films, untreated and γ-irradiated poly(vinyl fluoride) (PVF), poly(vinylidene fluoride) (PVDF), and poly(ethylene-co-tetrafluoroethylene) (ETFE), to ultraviolet (UV) irradiation was studied. The changes in tensile properties, thermal behavior, and chemical structure were investigated. The UV resistance of the PVF film is the lowest, and that of ETFE is the highest among the studied films. The biaxially oriented PVF films undergo massive chain scission under the UV irradiation. The chain scission process in both oriented PVF and PVDF films, although at different levels, is accompanied by increased solubility, increased upper glass transition temperatures, and decreased elevated temperature shrinkage. The UV exposure at 50°C, above the polymers' T_g has annealing effects, mainly reflected by a shift to higher temperatures of their upper glass transition. PVF films are unaffected by a low-dose ionizing radiation. However, the γ-irradiated films show reduction of their UV resistance. PVDF films undergo both chain scission and crosslinking by γ radiation, and the addition of UV exposure mainly causes further chain scission. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1471–1481, 1998     

The relationships between morphology,irradiation and the ductile–brittle transition of isotactic polypropylene

The effect of the morphology of polypropylene, as controlled by annealing, on the material's micro‐mechanical response before and after irradiation is explored using simultaneous SAXS/tensile deformation experiments. Morphology moderates the effects of cross‐linking and scission on the deformation behaviour. The micro‐mechanisms of deformation can be related to these morphological and chemical changes. It appears that a high tie‐chain density and a low crystal thickness, which may be achieved by crystallisation at low temperatures, will encourage resistance to mechanical property deterioration under irradiation. © 1999 Society of Chemical Industry     

Thermo-oxidative degradation of isotactic polypropylene film: Structural changes and its correlation with properties

Degradation of isotactic polypropylene has been studied by ageing the film samples at 70°, 80° and 90°C in air. Reactions involved in changing the molecular structure and formation of oxygenated and unsaturated groups, during thermo-oxidative degradation, are discussed. The increase in molecular weight ($\text{M}\text{?}{}_{\mathrm{v}}$) suggests molecular enlargement mainly by recombination of alkyl and alkoxy radicals which produces non-radical products. Tensile strength has been found to increase initially and then decreases with ageing time. Increase in isotacticity and density of polypropylene may be due to the cleavage of the backbone chain in the amorphous intercrystalline region, facilitating poorly ordered molecular segments into a more ordered helical form.     

Effect of electron beam irradiation on mechanical and dielectric properties of polypropylene films

In the present investigation the effect of electron beam irradiation on the mechanical properties of thin films of Polypropylene (PP) were measured. The dielectric properties of PP films were carried out in the frequency range from 20 Hz to 1 MHz at various DC bias potential. All measurements were carried out at room temperature. It is found that the electron beam irradiation caused an increase in Young's Modulus of PP film dose of up to 70 kGy were applied, but tensile strength and % elongation at break were found to be decrease with the increasing dose rate. The significant changes were observed in the case of dielectric constant and dielectric loss for electron irradiated PP films. The DSC results indicate that irradiation on PP films changes the thermal behavior. Minor differences in FTIR spectra were observed after irradiation treatment. It is observed that, the effect of radiation damage results in improvement in mechanical strength of the films. The increased dielectric constant and dependence of the bias voltage in case of irradiated and unirradiated PP films has been reported. It is suggested that, the PP films modified with the electron beam irradiation can be used as a good dielectric material for different electronic devices. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

芳纶浆粕增强聚丙烯复合材料的结构与性能

利用双螺杆挤出机制备了聚丙烯(PP) /芳纶浆粕(PPTA-pulp)以及聚丙烯(PP)/芳纶浆粕(PPTA-pulp)/马来酸酐接枝聚丙烯(MAH-g-PP)复合材料。采用力学性能测试、差示扫描量热仪（DSC）、扫描电子显微镜(SEM)、平板流变仪,研究了PP/ PPTA-pulp复合材料的力学性能、结晶行为、断面形态结构及流变行为。结果表明：随着PPTA-pulp含量的增加,复合材料的拉伸强度和弯曲模量增加,缺口冲击强度和断裂伸长率下降,芳纶浆粕对聚丙烯结晶起了成核剂的作用。马来酸酐接枝聚丙烯(MAH-g-PP)作为相容剂,改善了PPTA-pulp与基体PP分子之间的亲和性,提高了界面作用力,并使复合材料的储存模量、损耗模量和力学性能进一步改善。     

聚丙烯/含锌聚醚酯酰胺共混纤维的结构与性能

以氧化锌、己二酸、聚己二醇、己内酰胺和二苯甲烷二异氰酸酯(MDI)为原料制备含锌聚醚酯酰胺(M-PEEAM)。将聚丙烯(PP)与M-PEEAM共混制备PP/M-PEEAM共混物及其纤维,研究了PP/M-PEEAM共混物的热性质,考察了PP/M-PEEAM共混纤维的结构与力学性能。结果表明:PP/M-PEEAM共混物在166～167℃附近有大的吸热峰,在50℃和218℃附近有2个小吸热峰,多峰效应表明PP和M-PEEAM为不相容体系,M-PEEAM含量对PP/M-PEEAM共混物熔点影响不大;PP/M-PEEAM共混物具有两相结构,M-PEEAM呈球形分布在PP基体之中,M-PEEAM含量增加,球的直径增大,长度增加。PP/M-PEEAM共混纤维的断裂强度随着M-PEEAM含量增加而减小。     

Structure and mechanism of functional isotactic polypropylene via in situ chlorination graft copolymerization

This paper discusses the structure and mechanism of maleic anhydride (MAH) grafted onto isotactic polypropylene (iPP) via in situ chlorination graft copolymerization (ISCGC). The molecular structure of the grafted iPP was characterized using ¹H NMR and ¹³C NMR spectroscopy, viscosity‐average molecular weight and gel content. The structure of un‐grafted MAH present in the reaction system was investigated using Fourier transform infrared spectroscopy in order to explore the grafting of MAH on iPP. The main side‐reactions, including iPP chain scission and crosslinking, during the grafting reaction were explored. From the experimental results obtained, the reason for controlled macromolecular chain degradation and crosslinking of grafted iPP in ISCGC is proposed. Based on the structural characterization of the grafted polymer, the mechanism of grafting onto iPP obtained via ISCGC was deduced. Mechanical properties, both static and dynamic, of grafted iPP were also investigated and the results showed that the properties of the material changed due to grafted MAH. Copyright © 2011 Society of Chemical Industry     

Influence of structural organization on tensile properties in mesomorphic isotactic polypropylene

The effects of annealing on the structure and mechanical properties of mesomorphic isotactic polypropylene have been investigated using wide-angle and small-angle X-ray scattering and rheo-optics in addition to tensile tests. Young's modulus of mesomorphic phase was estimated to be 5 GPa using Takayanagi model. The α-crystallitic iPP prepared by annealing the quenched mesomorphic iPP was transparent because of the absence of spherulitic structure. It was found that the mechanical yielding of α-crystallitic iPP is dominated by the plastic flow of crystalline structural units whereas the yield process of α-spherulitic iPP quenched at 80 °C is caused by the fracture or fragmentation of crystalline structural units.