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The phase behaviour of a series of blends containing poly(hydroxybutyrate) with poly(hydroxybutyrateco- hydroxyvalerate) or a mixture of two copolymers of differing hydroxyvalerate (HV) content has been investigated using calorimetric methods backed up by morphological observations. Under static conditions, liquid-liquid phase separation (LLPS) was found to occur in blends where the relative HV level (i.e. difference in HV between the blend and the component of lowest HV) exceeded about 12%. The region of LLPS is asymmetrically placed at the high HV side of the phase diagram and the extent of phase separation increases as the relative HV level between the blend components is increased. Phase separation was promoted by shear. The results are compared with similar behaviour found in blends of linear with branched polyethylene


Blends of polyamide-6 (PA6) and acrylic core-shell impact modifiers (CSIM) were made by an extruder process as well as a reactor process. On the extruder blends, the impact behaviour was studied as a function of temperature while changing the type of CSIM, the CSIM concentration (0--40%) and the blending conditions. Reactor blends were prepared from caprolactam/CSIM mixtures via a hydrolytic polymerization process initiated either with water or with aminocapronic acid. The aminocapronic acid-initiated process is faster. The influence of reaction conditions on the deagglomeration of the CSIM, the melt flow index and the impact behaviour of the blends were studied. The degree of grafting of PA6 on the CSIM and the melt rheological behaviour of some samples have been investigated. The CSIM agglomerates were found to be broken up in the caprolactam starting mixture and did not coalesce to bigger particles. With the reactor blend method, often highly viscous melts were obtained. This is probably due to the formation of a comb-like structure of CSIM chains dissolved in caprolactam to which PA6 chains had been grafted


Novel copolymers of poly(ether ether ketone) containing ring trifluoromethyl groups have been synthesized by starting with trifluorobenzophenone monomers. Unlike poly(ether sulfone) analogues, it is possible to prepare copolymers which contain CF 3 groups ortho to the ether bridges. The CF 3 unit decreases the crystallinity of the polymer, with 50% and 100% copolymers being amorphous. This is accompanied by a rise in the glass transition temperature, although the thermal stability, mechanical properties and hydrophobicity of the polymer are largely unaffected


A range of reactions have been carried out using 11-bromoundecanoic acid attached to polymer supports in an attempt to prepare the first catenated polymers. In one series of reactions, cyclization of the polymer-supported polyester chains was effected in the presence of sharp fractions of polydimethylsiloxane rings, but no evidence of catenane formation could be found. Instead, a white crystalline product polyester was obtained. Its identity is discussed here. In another series of reactions, polymer-supported linear polyesters were cyclized in the presence of recycled cyclic polyesters. Gel permeation chromatographic analyses showed that substantial quantities of high molar mass material had been formed. This material may prove to be the first catenated polyesters to be prepared.


The oscillatory shear flow properties, dynamic storage and loss moduli (G' and G"), of a thermotropic liquid-crystalline polymer (TLCP) in both the isotropic and nematic regions were measured as functions of angular frequency (~o), using a cone-and-plate rheometer. For the study, an aromatic polyester, poly[(phenyl sulfonyl)-p-phenylene 1,10-decamethylene-bis(4-oxybenzoate)] (PSHQ10), was synthesized in our laboratory. The PSHQ10 was found to have (1) a glass transition temperature of 88°C, (2) a melting point of 115°C, and (3) a nematic-to-isotropic transition temperature of 175°C. We found that the oscillatory shear flow properties of PSHQ10 in the nematic region were strongly dependent on its thermal history (i.e. annealing temperature and the duration of annealing) and shear history. Thus, in order to completely erase the thermal history associated with polymerization and sample preparation, a solvent-cast PSHQ10 specimen was first heated to the isotropic region (e.g. 190°C), sheared there at a very low shear rate (0.0085 s- 1) for ~ 5 min, and then cooled very slowly down to a predetermined temperature (130, 140, 150, 160 or 170°C) in the nematic region. We found that in the isotropic region time-temperature superposition holds and plots of log G' versus log G" give rise to a temperature-independent correlation. On the other hand, we found that in the nematic region preshearing has a profound influence on the oscillatory shear flow properties and log G' versus log G" plots show temperature dependency. This suggests that time-temperature superposition would not hold in the nematic region of PSHQ10 (and also of other types of TLCPs). We thus conclude that log G' versus log G" plots are very sensitive to variations in the morphological state of PSHQ10 as the temperature varies in the nematic region. We found that the Cox-Merz rule holds for PSHQ10 in the isotropic region and the morphological state of a specimen plays an important role in determining whether or not the Cox-Merz rule holds in the nematic region; specifically an unsheared specimen does not follow the Cox-Merz rule, whereas a sheared specimen does.


Commercial emulsion-made impact modifiers with a shell of poly(methyi methacrylate) (PMMA) chains grafted onto a rubber core, either acrylate or butadiene based, cannot be adequately dispersed in a matrix of poly(butylene terephthalate) (PBT) to achieve useful toughening. However, it is known that tough materials can be achieved when these blends also contain polycarbonate (PC). It is demonstrated here that 10 wt% or less of PC greatly facilitates the dispersal of such core-shell impact modifiers in a PBT matrix and leads to tough blends even at low temperatures. It is known that PC wets PBT and PMMA better than PBT and PMMA wet each other, which allows the PC to act as a dispersing agent for these impact modifier particles in the PBT matrix. The morphology and mechanical properties of ternary blends where PC is a major matrix component rather than simply a dispersing agent are also examined.


Morphological changes resulting from the elongation of poly(tetrafluoroethylene) (PTFE) have been examined using rheo-photoacoustic Fourier transform infra-red (r.p.a. FTi.r.) methodology. Based on the quantitative analysis of the r.p.a. FTi.r. data, several transitions in the film permeability are identified over the range of examined elongations, and the mechanism responsible for these transitions is discussed. Electron microscopy and X-ray diffraction measurements were utilized in an attempt to further support the proposed mechanism of elongation in the negative Poisson ratio region. In contrast to polyethylene and other polymers, this phenomenon is characteristic of PTFE. The strain dichroic ratios obtained using transmission FTi.r. spectroscopy are not sensitive to these transitions.


A polymer containing photochromic moieties is obtained by means of the transesterification of poly(vinyl acetate) with 2-phenyl-5-carboxy-1,3-indandione. Upon u.v. irradiation of a solution and film of this polymer a transition to its benzalphthalide form is observed. It is assumed that the photochemical isomerization of 2-phenyl-l,3-indandione can also start from its enol form


We have fully characterized the three-dimensional morphology of thin films of mixtures of polystyrene and polybutadiene cast from a toluene solution, using nuclear reaction analysis, neutron reflectometry and transmission electron microscopy. Polystyrene-rich phases wet both the air and substrate interfaces and are separated by a polybutadiene-rich phase; these layers are very well defined and the interfaces between them are sharp (down to < 20 A). Within the polybutadiene-rich central layer, lateral phase separation is also evident, with polystyrene-rich domains of oblate spheroidal shape. Under certain circumstances thin polystyrene-rich layers exist within the polybutadiene-rich phase. We discuss possible mechanisms for this unusual morphology in terms of surface effects on the mechanism of phase separation in the ternary polymer-solvent system from which the films are cast.


A novel process for the fabrication of optical quality thin films of rigid-rod polymers by coagulation from an isotropic solution is reported. This process consists of the following steps: (1) extrusion or doctor-blading of an isotropic rigid-rod polymer solution into a uniform thin solution layer; (2) relaxation of the solution in an atmosphere containing the vapour of a non-solvent for an appropriate length of time; and (3) coagulation of the solution in a non-solvent bath. Thin films of rigid-rod poly(p-phenylene benzobisthiazole) (PBZT) thus prepared do not show the large voids or line defects commonly observed in the extruded and subsequently coagulated PBZT thin films. A processing window based on the solution thickness and relaxation duration is outlined for a 1 wt% PBZT solution in methanesulfonic acid to fabricate void-free PBZT thin films up to 6 #m in thickness at room temperature. Optical spectra and micrographs show that the PBZT thin films prepared by the current process compare favourably with those extruded and then coagulated in terms of low optical loss and fewer defects.


Корисні статті

Комп'ютер для інженера

У сучасному світі комп'ютери дуже поширені. Складно уявити людину, не знайому з цим поняттям. Багато професій зобов'язані своїм виникненням саме комп'ютеру, вони б просто не з'явилися без створення електронно-обчислювальної техніки.

І хоча відносно недавно, на початку XX століття, комп'ютери були розкішшю і використовувалися лише для самих складних розрахунків, у наш час комп'ютери та комп'ютерна техніка дуже глибоко інтегрувалися у наше життя. Сучасне людство залежить від комп'ютерів, що викликає подиву, якщо розглянути, коли і в яких випадках вони використовуються.

Вибір професії

Кожна людина зіштовхується у своєму житті з вибором, який найсильніше вплине на все її подальше життя. Йдеться про вибір професії та вибір вищої освіти. Закінчуючи школу, молоді люди стикаються з величезним вибором професій та спеціальностей: інженер, економіст, юрист, менеджер, маркетолог, логіст, фінансист і т.д. При цьому навколо можна чути безліч стереотипних фраз: "Юристи багато заробляють", "Фінансисти працюють з грошима, тому у них хороші зарплати", "Маркетолог - основний людина в будь-якому бізнесі", а часом і просто без обґрунтування - "Менеджер - це круто ". Часом, такі "поради" впливають на вибір професії.

Хто такий інженер

Інженер - професія нелегка, але одночасно з цим дуже цікава і захоплююча. Адже інженер це людина, у якого народжуються в голові нові ідеї і тому він здатний винаходити.

У багатьох виникає питання: хто такі інженери? Інженер (франц. Ingénieur) - фахівець з вищою технічною освітою. Спочатку інженерами називали людей, які керували військовими машинами. Поняття громадський інженер з'явилося в XVI столітті в Голландії, застосовано до сфери будівництва мостів і доріг, потім інженери з'явилися в Англії, а потім в інших країнах.


Хто такий інженер-конструктор? Даним питанням задаються багато людей, які бажають пов'язати своє життя з цією професією. Варто відзначити, що ця професія однією з найбільш високооплачуваних на сучасному ринку праці, яка характеризується високим попитом з боку роботодавців. Інженер-конструктор машинобудування повинен володіти аналітичним складом розуму, підвищеною уважністю до деталей і відповідальним підходом до роботи. Дана діяльність пов'язана з прорахунками і різноманітним обладнанням. Першокласний інженер-конструктор механік володіє також такими рисами характеру, як раціональність і ерудованість. Важливу роль відіграє стресостійкість, адже робочий процес є досить трудомістким і при потребі замовника вимагає готовності швидко вносити зміни в готові креслення.

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