The Effect of Injection Moulding Temperature on PET Particles/Fibrils in Blends and MFCs

The microfibrillar composites of polypropylene (PP)/poly(ethylene terephthalate) (PET) have been prepared by twin-screw extrusion, followed by cold drawing. The employed stretch ratio was 4. Further processing was done by injection moulding at three different processing temperatures (210ºC, 230ºC, 280ºC) on PP/PET blends with wt% 70/30 Samples were subjected to extensive characterization in each step of MFC preparing. Fourier Transform Infrared (FTIR) spectroscopy was employed to determine the nature of the interaction between the polymers in the composites.. Thermogravimetric Analysis (TGA) were used to investigate degradation of polymers. The crystallization, melting behaviour and the crystallization morphology were investigated by Dynamic Scanning Calorimetry (DSC) and Polarized Optical Microscopy (POM). Influence of processing temperature on morphology was investigated by using Scanning Electron Microscopy (SEM). The observations from the fracture surfaces were discussed and compared with the mechanical properties, and the results have shown a significant influence of the injection moulding temperature on the morphology development and mechanical properties

MILTONOVA SUBVERZIJA GRČKE TRAGIČNE FORME U SAMSONU AGONISTESU

When it comes to analyzing Milton’s moral vision in his major works, his tragedy Samson Agonistes is something of a curiosity. Unlike in Milton’s other major two works, the epics Paradise Lost and Paradise Regained, where themes of morality, sins, punishment and redemption are relatively clear, the situation in Samson Agonistes becomes increasingly ambiguous the more we entangle ourselves with the enigmatic nature of the Old Testament judge Samson, here presented as a tragic protagonist in Milton’ first and only tragedy, published in 1671. An especially interesting issue to consider is Milton’s treatment of the classical tragic structure and conventions in his own play, which is the topic of this discussion. These elements which Milton subverts, modifies and adheres to give Samson Agonistes an intriguing structure that tells a story of its own, a story of a peculiar protagonist whose moral expression starts to assume a mutability which, artistically speaking, establishes Milton’s play as a seemingly inexhaustibly fertile ground for analysis of the abovementioned themes. Especially important here are the two texts, one a critical literary analysis, the other a classical tragedy which inspired Milton a lot: Aristotle’s Poetics and Sophocles’ Oedipus at Colonus. With the comparison of these two texts with Milton’s play, what emerges is a kind of a Miltonic tragic figure greatly congruous with Milton’s ideas on the complex interplay of artistic and moral expression in a literary text.Pri analizi Miltonove moralne vizije u njegovim glavnim djelima ona izražena u tragediji Samson Agonistes predstavlja određenu enigmu. Za razliku od dva velika Miltonova djela, epova Izgubljeni raj i Nanovo stečeni raj, gdje su teme o moralnosti, grijesima, kazni i iskupljenju izražene relativno jasno, situacija u Samsonu Agonistesu postaje sve dvosmislenijom što se više uplićemo u zagonetnu prirodu starozavjetnoga suca Samsona, ovdje predstavljena kao tragična protagonista u Miltonovoj prvoj i jedinoj tragediji, objavljenoj 1671. godine. Posebno je zanimljiva Miltonova obrada strukture i odlika klasične grčke tragedije što je i tema ovoga istraživanja. Ovi elementi, neki kojih se Milton vjerno pridržava, ali i neki koje prerađuje i odbacuje, daju Samsonu Agonistesu neobičnu strukturu koja i sama iskazuje određenu viziju ili ima svoju priču. To je priča o neobičnu protagonistu čiji moralni izražaj počinje poprimati promjenjivost koja, s umjetničkoga gledišta, predstavlja nepresušivo vrelo za analizu tema koje se tiču moralnosti. Pri toj analizi posebno su korisna dva teksta, jedan je rana književna kritika, a drugi klasična tragedija koja je uvelike inspirirala Miltona pri pisanju njegove drame; riječ je, naime, o Aristotelovoj Poetici i Sofoklovoj tragediji Edip kod Kolona. Ono što proizilazi pri usporedbi i analizi ovih tekstova jest svojevrsni miltonovski klasični tragični protagonist, tvorevina koja je u skladu s njegovim idejama o složenoj isprepletenosti umjetničkoga i moralnoga izričaja u književnome djelu

Amiloid kod aponeurotske ptoze

PURPOSE: Histopathological and immunohistochemical evaluation of levator aponeurosis in patients with aponeurotic ptosis vs. control aponeurosis obtained from autopsies of cadavers without history of ptosis, especially in relation with presence of amyloid deposition. MATERIAL AND METHODS: Seven levator specimens were taken from 6 patients, undergoing anterior levator repair due to aponeurotic ptosis. The control group consisted of 12 levator aponeurosis specimens harvested from both lids of 6 cadavers, during autopsy. Congo red was used to detect amyloid and Orcein stain for elastic fibers. Immunohistochemistry was applied as a final marker for amyloid. RESULTS: In 2 out of 6 (33,3%) aponeurotic patients we demonstrated amyloid. Orbital and systemic involvement was excluded. The levator aponeurosis was attenuated, stretched and grayish in all patients, but still attached to the tarsus. Collagen bundles were thinned with fatty and elastotic degeneration of different grade in all samples. Control group was negative for amyloid. CONCLUSION: We demonstrated amyloid in 33,3% of patients with aponeurotic ptosis, without systemic amyloidosis, which may open a new perspective in aponeurotic ptosis etiology explanation.CILJ: Patohistološka i imunohistokemijska evaluacija aponeuroze m. levator palpebrae superior, posebice istraživanje prisustva amiloidnih depozita, u pacijenata s aponeurotskom ptozom, u usporedbi s kadaverima bez ptoze u anamnezi. SUBJEKTI I METODE: Sedam uzoraka aponeuroze m.levator palpebrae superior su uzeti tijekom operacije ptoze. Kontrolnu skupinu čini 12 uzoraka aponeuroze dobivenih iz obje vjeđe kadavera tijekom obdukcije. Congo red bojenje je korišteno za dokaz amiloida, a Orcein za dokazivanje elastičnih vlakana. Imunohistokemija je poslužila kao krajnji dokaz za amiloid. REZULTATI: Amiloid je dokazan u 2 od 6 (33,3%) pacijenata s aponeurotskom ptozom. Sistemna amiloidoza je isključena. Aponeuroza m.levator palpebrae superior je stanjena, istegnuta i sivkasta u svih pacijenata, ali jo. uvijek pričvršćena za tarzus. Degeneracija kolagenih vlakana, te masna i elastotična degeneracija razlieitog stupnja je dokazana u svim uzorcima. Amiloid je negativan u svim aponeurozama kadavera. ZAKLJUČAK: Dokazali smo amiloid u čak 33,3% uzoraka aponeuroze m.levator palpebrae superior pacijenata s aponeurotskom ptozom, bez sistemne bolesti, što otvara novu perspektivu u rješavanju etiologije aponeurotske ptoze

Structure-properties-processing relationships in PP-PET microfibrillar composites

This doctoral dissertation has focused on the structure-properties-processing relationships in microfibrillar composites (MFCs) prepared from polypropylene (PP) and poly(ethylene terephthalate) (PET). The MFC concept consists of three processing steps – melt blending via twin-screw extrusion, fibrillation via cold drawing, and isotropization by injection moulding or extrusion, resulting in binary composites of the higher melting temperature component being dispersed as microfibres in a matrix i.e. the lower melting temperature component. The microfibrillar structure of the reinforcement may contribute to improved mechanical properties – both stiffness and toughness. MFCs are considered an interesting class of environment-friendly fibrereinforced composites produced with conventional processing equipment and, as such, they have a large possibility to find their place in numerous applications. Although various experimental studies have been done within the field of MFCs, still, some shortcomings may be found. The development of a microfibrillar structure of the reinforcement and retaining this structure during the final melt processing step was depicted as one of the crucial factors for achieving high-quality composites, but it was not yet investigated in detail. Moreover, the influence of the fibrillation step on certain properties such as degradation and dynamic mechanical properties was not widely reported. Further on, the literature review has shown that additives and compatibilizers may play an important role in the development of the microstructure of MFCs, especially pointing out the importance of the step of production at which they are added. Overall, carefully linking the processing, their structure, with their resulting properties is essential. The research questions of this doctoral research are, therefore, as follows: i) How do the properties of MFCs change upon application of different cold draw ratios?; ii) What are the optimal processing parameters used in MFC production?; iii) What is the effect of the addition of elastomers and elastomerbased compatibilizers at different steps of the MFC manufacturing on the morphology and mechanical properties of MFCs?; and iv) Can the MFC concept be applied to novel applications such as thermoforming and the upcycling of immiscible recycled PP/PET blends? The polymers used in this research were limited to PP as matrix and PET as reinforcement, while a polyolefin based elastomer (POE) and a POE grafted maleic anhydride (POE-g-MA) were used as additives. The first part of the research focused on evaluating the influence of the fibrillation and isotropization processing stages on the development of the MFC microstructure. Fibrillation was found to be a crucial step in the production of the MFCs; therefore, different draw ratios were applied during the experimental part to define an optimal aspect ratio of the microfibres, and the results are discussed in Chapter 4. The optimal draw ratio was found to be equal to eight. Overall, the morphological characterisation proved the existence of an immiscible PP-PET blend after melt blending, and the highly oriented fibrillar state of the reinforcement component after cold drawing. Moreover, after the final isotropization step, the microscopic images showed the PET fibres were preserved and they were well dispersed within the PP matrix. Physical-chemical characterisation has shown a significant influence of the microfibrillar structure on the crystallisation and degradation behaviours of the MFCs. The crystallisation temperature of the PP component has been increased, as the PET fibres act as strong heterogeneous nucleating agents for the PP spherulites, forcing the PP lamellae to orient perpendicular to the PET fibres surface, by forming a transcrystalline layer. The positive influence of this high nucleating effect was noticed in the MFCs’ dynamic mechanical properties, as they have increased with the increment of the fibre aspect ratio. Beside the fibrillation step, in Chapter 5, the effect of different injection moulding temperatures on various properties of the MFCs was studied too. Processing the MFCs at the lowest injection moulding temperature (210 ºC) resulted in the best MFC morphologies and performances. During the experimental work of this PhD, the optimal weight ratio of the polymer components for the PP/PET blend was found to be 80/20, respectively, while 6 wt% was found as the optimum quantity for the additives. Further research was focused on the addition of elastomer-based additives into the MFCs in different stages of processing and their effect on the crystalline microstructure and mechanical properties. Fillers and additives are widely used in polymer blending, hence, Chapter 6 of this dissertation was devoted to study their influence. The main objective of this part was to evaluate the potential of adding a compatibilizer during the isotropization step and its influence on the fibrillar morphology. However, postponing the compatibilizer addition did not improve the distribution of long fibres, neither created the best mechanical properties for a compatibilized PP-PET MFC. With the addition of POE-g-MA, the fibre aspect ratio has been reduced, but the nucleating effect of the fibres was still present. Small-angle light scattering indicated a decrease in the PP spherulite size in MFC samples due to the presence of long PET microfibres, as well as in compatibilized samples, although the fibre length was affected. In addition, it was proven that the presence of POE and POE-g-MA also may act as nucleators for the PP matrix; therefore, in these MFC samples, the nucleating effect was more pronounced. Mechanical characterisation confirmed the reinforcing effect of the PET microfibres in the MFCs. Particularly, the increase in tensile modulus was noticed in non-compatibilized MFC due to the large interfacial area between the microfibres and the matrix; therefore, it was considered that some interfacial contact between the components exists, which made the stress transfer more effective. Higher values for yield strength and strain at break, as well as for impact strength, were observed for the MFC containing POEg- MA added during extrusion. Outstanding mechanical properties for this sample were achieved due to the presence of the elastomeric compatibilizer, which has enhanced the interfacial adhesion between PP and PET in the final composite, resulting in better stress transfer under the applied load. The second part of this PhD research was focused on examining novel applications for MFCs. Injection moulding as the final processing step was, for the first time, replaced by extrusion and thermoforming. Applying these two techniques has brought new insight for the production of MFCs, and opens up the possibility of using the MFC concept for producing packaging trays, eventually suitable for food packaging applications. This investigation was presented in Chapter 7 and showed that producing MFCs in the form of sheets for thermoforming could be an innovative processing method. Structural analysis has shown high aspect ratio microfibres dispersed within the matrix and possessing an excellent level of orientation. Yield strength and strain at break increased with the addition of the compatibilizer, thus, facilitating the thermoforming process. However, a real optimisation of the thermoforming process itself was not the focus of this study and remains open for further research. In the end, the feasibility of using the MFC concept to upcycle recycled materials was explored in Chapter 8. Several recycled materials such as mixed bilayer PP/PET films, polyolefins (MPO), and talc-filled PP were selected for this study and used as matrices for MFCs. Recycled MFCs were successfully prepared by the 3-step processing, although these mixtures presented significant difficulties in processability. Unfortunately, outstanding mechanical properties were not achieved for these series of MFCs; they showed little or almost no improvement compared to their recycled matrices. SEM characterisation showed a high level of PET fibre coalescence present in the MFC made out of recycled bilayer film, while in other MFCs, a large heterogeneity of the microstructure was identified. In spite of the disappointing results of these recycled MFCs, the MFC concept can still be considered an interesting approach for upcycling of mixed polymer waste and to improve the original properties of recycled materials. However, this requires further in-depth investigations, taking into account various factors such as viscosity, heterogeneity, presence of different additives, levels of degradation, etc. Overall, this doctoral dissertation presented a deep and extensive study on the MFCs concept, focusing on the relationship between structure, properties, and processing, stressing the importance of each processing parameter, as well as polymer components and additives selected for the final composition. The identified gaps within the MFC field have been covered by the experimental work and reported results. A particular contribution to the scientific world has been made by introducing a novel method for the production of MFCs, i.e., extrusion and thermoforming, and trying to upcycle different recycled mixtures. Despite the current limited commercial use of MFCs, the introduction of new environmental regulations, imposing the utilisation of certain quantity of recycled materials, as well as the recyclability of the manufactured products, may provide a boost for MFCs. The investigations presented within this dissertation have opened some new research questions and proposals for future work, which are presented at the end of this doctoral thesis

The influence of draw ratio on morphology and thermal properties of MFCs based on PP and PET

The main goal of this study is to investigate the influence of draw ratio on morphology and properties in microfibrillar composites (MFCs). In situ MFCs based on polypropylene (PP) and poly(ethylene terephthalate) (PET) have been prepared at the weight ratio of 80/20 by twin-screw extrusion, followed by cold drawing and injection moulding. In order to study the differences in MFCs caused by draw ratio, the samples were prepared at different ratios and subjected to extensive characterization in each step of the MFC preparation process. The morphology of MFC and influence of draw ratio were investigated by using Scanning Electron Microscopy (SEM). The thermal decomposition of the polymers in MFCs was studied by Thermogravimetric Analysis (TGA), the melting and crystallization behaviour by Dynamic Scanning Calo-rimetry (DSC)

MFC concept as a possible solution for closed-loop recycling of food packaging trays

Flexible plastic films from food packaging trays make up one of the largest fractions of the plastic waste stream and recycling is one of the most important actions to deal with this fraction, reducing the impact of these plastics on the environment. However, the recyclability of multi-layered films is not straightforward and in most of the cases these fractions are landfilled or incinerated. Recycling of discarded mixed polymers without previous separation often results in low mechanical properties which have lead researchers to investigate novel solutions for recycling. In this research, the concept of microfibrillar composites (MFCs) was investigated aiming to upcycle mixed polymer waste streams. A blend based on polypropylene (PP) and poly(ethylene terephthalate) (PET) at a weight ratio of 80/20 PP/PET was studied. The final step of the MFC processing was conducted using a conical twin screw extrusion. The morphological results confirmed the presence of PET microfibrils in the composites, leading to an improvement in mechanical properties such as in the tensile yield strength and strain at break. Subsequently, the MFC samples were successfully moulded into trays via thermoforming

MODELI INDIVIDUALIZACIJE RAZREDNE NASTAVE

It is exactly the awareness of differences between the children that makes the initial incentive of considering and of practical attempts as to how to adjust teaching to their individual capabilities. The ever increasing need to strongly individualize work with children at any level of education, that is to say, to adjust it to their personal characteristics, has become even more prominent in the last decades in the world. This is due to the tendency that respect of human rights, respect of differences between people and respect of a man, as an individual, should be considered as the most important legacies of the civilized society, in which it is inconceivable to have an educated person who cannot express himself/herself properly, either in oral or written form, or who has a scarce active vocabulary, or who does not know the basic laws of the standard literary language. Bearing in mind that the importance of mother tongue is essential, we decided to analyze the efficiency of the model of individualization of teaching grammar and orthography. The aim of the empirical research was to establish whether individualization of lower elementary teaching of grammar and orthography can reach significantly better educational results in terms of statistics than in the case with teaching which is not individualized, that is to say, which is traditional. In this written work we will represent results of research which show that by individualization of lower elementary teaching of grammar and orthography can achieve significantly better educational results in terms of statistics can be achieved than in the case with teaching which is not individualized, that is to say, which is traditional. The obtained results can represent a very significant contribution in resolving of a current and highly important issue of our contemporary education and upbringing. Previous considerations, presentations and interpretations may encourage further research in this field.Svijest o razlikama među djecom jesu polazni poticaj razmišljanja i praktičnih pokušaja o tome kako da se nastava prilagodi njihovim individualnim sposobnostima. Sve izraženija potreba da se rad sa djecom na bilo kom nivou školovanja u što većem obimu individualizira, odnosno, prilagodi njihovim osobinama ličnosti, posljednjih decenija je u svijetu još naglašenija, zbog tendencije da se poštovanje ljudskih prava, uvažavanje razlika među ljudima i poštovanje čovjeka, kao posebnog bića, smatraju najvažnijim tekovinama civiliziranog društva, u kojem se ne može zamisliti obrazovan čovjek koji se jezično usmeno i pismeno pogrešno izražava, koji ima siromašan aktivni rječnik, koji ne poznaje osnovne zakonitosti našeg standardnog književnog jezika. Imajući u vidu da je značaj materinjeg jezika fundamentalan, opredijelili smo se da ispitamo efikasnost modela individualizacije nastave gramatike i pravopisa. Cilj empirijskog istraživanja je utvrditi da li se individualizacijom razredne nastave gramatike i pravopisa postižu statistički značajno bolji rezultati nego nastavom koja nije individualizirana, tj. koja je tradicionalna. U ovom radu prikazat ćemo rezultate istraživanja iz kojih se vidi da se individualizacijom razredne nastave gramatike i pravopisa postižu statistički značajno bolji obrazovni učinci nego nastavom koja nije individualizirana, tj. koja je tradicionalna. Dobiveni rezultati mogu predstavljati izuzetno značajan prilog rješavanju jednog nadasve aktualnog i važnog pitanja našeg suvremenog obrazovanja i odgajanja. Prethodna razmatranja, prezentacije i interpretacije mogu poticati daljnja istraživanja u ovoj oblasti

Three Stories

Književni prijevo