Polylactide-Based Nonisocyanate Polyurethanes: Preparation, Properties Evaluation and Structure Analysis

This study investigated the successful synthesis and characterization of nonisocyanate polyurethanes (NIPUs) based on polylactide. The NIPUs were synthesized by a condensation reaction of oligomers with hard segments (HSs) and synthesized carbamate-modified polylactic acid containing flexible segments (FSs). The oligomers with HSs were prepared from phenolsulfonic acid (PSA) or a mixture of PSA and hydroxynaphthalenesulfonic acid (HNSA), urea and formaldehyde. The mixing of oligomeric compounds with different amounts of formaldehyde was carried out at room temperature. Obtained NIPU samples with different hard segment content were tested for their mechanical and thermal properties. The tensile strength (TS) of all NIPU samples increased with an increasing amount of HSs, attaining the maximum value at an HS:FS ratio of 1:3. Samples prepared from PSA and HNSA showed higher tensile strength (TS) without significant change in elongation at break compared to the samples based only on PSA. Thermogravimetric analysis data indicated an absence of weight loss for all samples below 100 °C, which can be considered a safe temperature for using NIPU materials. Maximum degradation temperatures reached up to 385 °C. Fourier transform infrared spectroscopy results confirmed the existence of expected specific groups as well as the chemical structure of the prepared polyurethanes. DSC analysis showed the existence of two characteristic phase transitions attributed to the melting and crystallization of hard segments in the NIPU samples.

Polymer Biocompositions and Nanobiocomposites Based on P3HB with Polyurethane and Montmorillonite

Due to the growing interest in biopolymers, biosynthesizable and biodegradable polymers currently occupy a special place. Unfortunately, the properties of native biopolymers make them not good enough for use as substitutes for conventional polymers. Therefore, attempts are being made to modify their properties. In this work, in order to improve the properties of the poly(3-hydroxybutyrate) (P3HB) biopolymer, linear aliphatic polyurethane (PU) based on 1,4-butanediol (BD) and hexamethylene 1,6-diisocyanate (HDI) was used. The conducted studies on the effect of the amount of PU used (5, 10, 15 and 20 m/m%) showed an improvement in the thermal properties of the prepared polymer blends. As part of the tested mechanical properties of the new polymer blends, we noted the desired increase in the tensile strength, and the impact strength showed a decrease in hardness, in particular at the presence of 5 m/m% PU. Therefore, for further improvement, hybrid nanobiocomposites with 5 m/m% PU and organically modified montmorillonite (MMT) (Cloisite 30®B) were produced. The nanoadditive was used in a typical amount of 1-3 m/m%. It was found that the obtained nanobiocomposites containing the smallest amount of nanofillers, i.e., 1 m/m% Cloisite®30B, exhibited the best mechanical and thermal properties.

Hybrid Epoxy Nanocomposites: Improvement in Mechanical Properties and Toughening Mechanisms—A Review

This article presents a review on the recent advances in the field of ternary diglycidyl ether of bisphenol A epoxy nanocomposites containing nanoparticles and other modifiers. Particular attention is paid to their mechanical and thermal properties. The properties of epoxy resins were improved by incorporating various single toughening agents, in solid or liquid states. This latter process often resulted in the improvement in some properties at the expense of others. The use of two appropriate modifiers for the preparation of hybrid composites, possibly will show a synergistic effect on the performance properties of the composites. Due to the huge amount of modifiers that were used, the present paper will focus mainly on largely employed nanoclays with modifiers in a liquid and solid state. The former modifier contributes to an increase in the flexibility of the matrix, while the latter modifier is intended to improve other properties of the polymer depending on its structure. Various studies which were carried out on hybrid epoxy nanocomposites confirmed the occurrence of a synergistic effect within the tested performance properties of the epoxy matrix. Nevertheless, there are still ongoing research works using other nanoparticles and other modifiers aiming at enhancing the mechanical and thermal properties of epoxy resins. Despite numerous studies carried out so far to assess the fracture toughness of epoxy hybrid nanocomposites, some problems still remain unresolved. Many research groups are dealing with many aspects of the subject, namely the choice of modifiers and preparation methods, while taking into account the protection of the environment and the use of components from natural resources.

Polymer/Layered Clay/Polyurethane Nanocomposites: P3HB Hybrid Nanobiocomposites-Preparation and Properties Evaluation

This paper presents an attempt to improve the properties of poly(3-hydroxybutyrate) (P3HB) using linear aliphatic polyurethane (PU400) and organomodified montmorillonite (MMT)-(Cloisite^®30B). The nanostructure of hybrid nanobiocomposites produced by extrusion was analyzed by X-ray diffraction and transmission electron microscopy, and the morphology was analyzed by scanning electron microscopy. In addition, selected mechanical properties and thermal properties were studied by thermogravimetric analysis, TGA, and differential scanning calorimetry, DSC. The interactions of the composite ingredients were indicated by FT IR spectroscopy. The effect of the amount of nanofiller on the properties of prepared hybrid nanobiocomposites was noted. Moreover, the non-equilibrium and equilibrium thermal parameters of nanobiocomposites were established based on their thermal history. Based on equilibrium parameters (i.e., the heat of fusion for the fully crystalline materials and the change in the heat capacity at the glass transition temperature for the fully amorphous nanobiocomposites), the degree of crystallinity and the mobile and rigid amorphous fractions were estimated. The addition of Cloisite^®30B and aliphatic polyurethane to the P3HB matrix caused a decrease in the degree of crystallinity in reference to the unfilled P3HB. Simultaneously, an increase in the amorphous phase contents was noted. A rigid amorphous fraction was also denoted. Thermogravimetric analysis of the nanocomposites was also carried out and showed that the thermal stability of all nanocomposites was higher than that of the unfilled P3HB. An additional 1% mass of nanofiller increased the degradation temperature of the nanocomposites by about 30 °C in reference to the unfilled P3HB. Moreover, it was found that obtained hybrid nanobiocomposites containing 10 wt.% of aliphatic polyurethane (PU400) and the smallest amount of nanofiller (1 wt.% of Cloisite^®30B) showed the best mechanical properties. We observed a desirable decrease in hardness of 15%, an increase in the relative strain at break of 60% and in the impact strength of 15% of the newly prepared nanobiocomposites with respect to the unfiled P3HB. The produced hybrid nanobiocomposites combined the best features induced by the plasticizing effect of polyurethane and the formation of P3HB-montmorillonite-polyurethane (P3HB-PU-MMT) adducts, which resulted in the improvement of the thermal and mechanical properties.

Biobased poly(3-hydroxybutyrate acid) composites with addition of aliphatic polyurethane based on polypropylene glycols

Poly(3-hydroxybutyrate) (P3HB) is the most important of the polyhydroxyalkanoates. It is biosynthesized, biodegradable, biocompatible, and shows no cytotoxicity and mutagenicity. P3HB is a natural metabolite in the human body and, therefore, it could replace the synthetic, hard-to-degrade polymers used in the production of implants. However, P3HB is a brittle material with limited thermal stability. Therefore, in order to improve its mechanical properties and processing parameters by separating its melting point and degradation temperature, P3HB-based composites can be produced using, for example, linear aliphatic polyurethanes as modifiers. The aim of the study is a modification of P3HB properties with the use of linear aliphatic polyurethanes synthesized in reaction of hexamethylene diisocyanate (HDI) and polypropylene glycols (PPG) by producing their composites. Prepared biocomposites were tested by the scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetry (TGA). Furthermore, selected mechanical properties were evaluated. It has been confirmed that new biocomposites showed an increase in impact strength, relative strain at break, decrease of hardness and higher degradation temperature compared to the unfilled P3HB. The biocomposites also showed a decrease in the glass transition temperature and the degree of crystallinity. Biocomposites obtained with 10 wt. % polyurethane synthesized with polypropylene glycol having 1000 g ⋅ mole-1 and HDI have the best thermal and mechanical properties.

Thermally stable biopolymer composites based on poly(3-hydroxybutyrate) modified with linear aliphatic polyurethanes – preparation and properties

Purpose: Poly(3-hydroxybutyrate) (P3HB) is a biopolymer, but storing products from P3HB causes the deterioration of their properties leading to their brittleness. P3HB has also low thermal stability. Its melting point almost equals its degradation temperature. To obtain biodegradable and biocompatible materials characterized by higher thermal stability and better strength parameters than the unfilled P3HB, composites with the addition of polyurethanes were produced. Methods: The morphology, thermal, and mechanical property parameters of the biocomposites were examined using scanning electron microscopy, thermogravimetric analysis, standard differential scanning calorimetry, and typical strength machines. Results: Aliphatic polyurethanes, obtained by the reaction of 1,6-hexamethylene diisocyanate and polyethylene glycols, were used as modifiers. To check the influence of the glycol molar mass on the properties of the biocomposites, glycols with a molecular weight of 400 and 1000 g/mol were used. New biocomposites based on P3HB were produced with 5, 10, 15, and 20 wt. % content of polyurethane by direct mixing using a twin-screw extruder. The following property parameters of the prepared biocomposites were tested: degradation temperature, glass transition temperature, tensile strength, impact strength, and Brinell hardness. Conclusions: Improvement of the processing property parameters of P3HB-biocomposites with the addition of aliphatic polyurethanes was achieved by increasing the degradation temperature in relation to the degradation temperature of the unfilled P3HB by over 30 °C. The performance property parameters have also been improved by reducing the brittleness compared to the P3HB, as evidenced by the increase in impact strength and the decrease in hardness with an increase in the amount of polyurethane obtained by the reaction of 1,6-hexamethylene diisocyanate and polyethylene glycol with a molecular weight of 400 g/mol (PU400) as modifier.

Thermally stable biopolymer composites based on poly(3-hydroxybutyrate) modified with linear aliphatic polyurethanes - preparation and properties

PURPOSE

Poly(3-hydroxybutyrate) (P3HB) is a biopolymer, but storing products from P3HB causes the deterioration of their properties leading to their brittleness. P3HB has also low thermal stability. Its melting point almost equals its degradation temperature. To obtain biodegradable and biocompatible materials characterized by higher thermal stability and better strength parameters than the unfilled P3HB, composites with the addition of polyurethanes were produced.

METHODS

The morphology, thermal, and mechanical property parameters of the biocomposites were examined using scanning electron microscopy, thermogravimetric analysis, standard differential scanning calorimetry, and typical strength machines.

RESULTS

Aliphatic polyurethanes, obtained by the reaction of 1,6-hexamethylene diisocyanate and polyethylene glycols, were used as modifiers. To check the influence of the glycol molar mass on the properties of the biocomposites, glycols with a molecular weight of 400 and 1000 g/mol were used. New biocomposites based on P3HB were produced with 5, 10, 15, and 20 wt. % content of polyurethane by direct mixing using a twin-screw extruder. The following property parameters of the prepared biocomposites were tested: degradation temperature, glass transition temperature, tensile strength, impact strength, and Brinell hardness.

CONCLUSIONS

Improvement of the processing property parameters of P3HB-biocomposites with the addition of aliphatic polyurethanes was achieved by increasing the degradation temperature in relation to the degradation temperature of the unfilled P3HB by over 30 °C. The performance property parameters have also been improved by reducing the brittleness compared to the P3HB, as evidenced by the increase in impact strength and the decrease in hardness with an increase in the amount of polyurethane obtained by the reaction of 1,6-hexamethylene diisocyanate and polyethylene glycol with a molecular weight of 400 g/mol (PU400) as modifier.

Effect of aging conditions on the mechanical properties and antimicrobial activity of elastomer nanocomposites

The present study investigates the effect of thermooxidative and photooxidative aging on the mechanical and bactericidal properties of elastomer nanocomposites (ENs) based on Nanobent ZR2. The mechanical properties and morphologies were analyzed before and after aging. The addition of nanoparticles had a significant effect on the mechanical properties of ENs. Samples containing Nanobent exhibited higher tensile strength before and after aging compared to the reference composition. The addition of nanoparticles attenuated elastomer aging at elevated temperatures and ultraviolet light. Aged nanocomposites showed an inhibitory effect on the growth of bacteria and yeasts. Antibacterial and antifungal activity was only partially reduced after aging using physical methods compared to the activity of probes without aging. Scanning electron microscopy micrograph analysis showed different rough but homogeneous structures, confirming the uniform dispersion of the modified nanoparticles in the elastomer matrix as well as the retention of mechanical properties after the aging process.

Study on the adhesive properties of reactive liquid rubber toughened epoxy-clay hybrid nanocomposites

The present work investigates the adhesive properties and morphology of diglycidyl ether of bisphenol A nanocomposites modified with reactive butadiene acrylonitrile copolymers having different amine equivalent weight. Tensile adhesive strength and shear adhesive strength of epoxy resin were significantly increased due to reactive rubbers and nanoparticles (ZW1) incorporation to the epoxy matrix. Hybrid composites based on 1 wt% ZW1 and 10 wt% ATBN-16, 1 wt% ZW1 and 15 wt% ATBN-21 exhibited maximum adhesive strength in comparison with neat epoxy resin as well as epoxy nanocomposite containing 1% ZW1. Tensile adhesive strength of hybrid composites containing 1% ZW1 and 10% ATBN-16 as well as 1% ZW1 and 15% ATBN-21 was maximally enhanced. The fracture surfaces of epoxy hybrid composites showed significant plastic yielding together with delaminated and stratified structures, explaining thus the increase of the adhesive strength of tested composites. This finding was confirmed by FTIR spectra in terms of chemical reactions occurrence between the reactive rubbers and epoxy matrix.

Rubber elastomeric nanocomposites with antimicrobial properties

In this paper we show an elastomeric nanocomposite that exhibits antibacterial and antifungal activity. It comprises a rubber blend matrix and a nanofiller, which is a modified bentonite clay (Nanobent® ZR2). We have developed innovative technology for the nanofiller incorporation into the rubber matrix. This new approach was successfully implemented in pilot production at the Polish chemical manufacturer Spoiwo (Spoldzielnia Pracy Chemiczno-Wytworczej 'Spoiwo', Radom, Poland). Here we reveal that addition of the functionalised bentonite affects the mechanical and thermal behaviour of elastomers. For example, by adding 1-3% of bentonite nanoparticles we strongly enhanced elongation and tensile stress at break, whereas stiffness remained unchanged. We observed improvement of the thermal properties of the nanocomposites yielded and extension of the temperature usage range (from -29 to 311°C). As a proof of concept we present the antimicrobial effect of elastomeric nanocomposites verified on a wide range of both pathogenic and opportunistic reference bacteria strains, as well as reference strains of yeasts. The proposed method of hydrophilic nanofiller introduction into the rubber elastomer is economically viable and enables fabrication of elastomeric elements with high added value. Their significant antibacterial and antifungal activity makes them desirable in medicine, biomedical engineering, and the food industry.

Preparation and characterization of reactive liquid rubbers toughened epoxy-clay hybrid nanocomposites

The present work investigates the effect of organomodified nanoclay (ZW1) and butadiene-acrylonitrile copolymer terminated with different amine groups (amine-terminated butadiene-acrylonitrile, ATBN) on the properties and morphology of epoxy resin. The morphologies of the nanocomposites were analyzed by X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The nanocomposites structure was confirmed by Fourier transform infrared (FTIR) spectroscopy, XRD and TEM. The properties evaluation showed that the polymeric modifier and nanoclays strongly influence the fracture toughness and flexural properties of the nanocomposites. Hybrid epoxy composites containing 1% ZW1 and ATBN rubbers showed improved fracture toughness and flexural properties in comparison with unmodified epoxy resin. FTIR spectra showed an increase in the hydroxyl peak height peak height of 3360 cm-1 due to reactive rubber incorporation. SEM micrographs of hybrid epoxy resin nanocomposites showed significant plastic yielding of the polymer matrix with stratified structures and more cavitations, explaining thus the enhancement of fracture toughness and flexural strength of the nanocomposites.

Effect of mixing parameters on the mechanical and thermal properties of a nanoclay-modified epoxy resin

The present work deals with the effect of the sonication amplitude and the mixing time on the mechanical and thermal properties of an epoxy (EP) resin modified with 1 wt% nanoclay. It was confirmed that the mechanical properties of the EP matrix were dependent on the dispersion of nanoclays which in turn are affected by the mixing parameters. At short mixing times, the impact strength (IS) increased with increasing amplitude. Maximum IS and flexural properties values were obtained with ultrasonic amplitude of 260 μm and a mixing time of 10 min. The effect of mixing time was more pronounced on the deflection temperature under load than the sonication amplitude. Moreover, it was shown that longer mixing times resulted in a smoother nanocomposite fracture surface with only few cracks. The fracture surfaces of the EP nanocomposites were rough with significant plastic deformations and several microcracks with nanoparticles embedded in the polymer matrix.

Long saphenous tunnel infiltration with levobupivicaine reduces rescue analgesia requirements following varicose vein surgery: randomized, double-blind, placebo-controlled trial [ISRCTN58431114]

OBJECTIVES

To determine whether local anaesthetic infiltration of the long saphenous tunnel in patients undergoing unilateral, primary long saphenous stripping and multiple avulsions reduces early postoperative pain and requirement for opiate analgesia.

METHODS

Patients were randomized to receive either levobupivicaine or an equivalent volume of normal saline infiltrated around the groin incision and along the long saphenous tunnel. Analgesia and linear analogue pain scores at 1, 6 and 24h postoperatively were recorded.

RESULTS

Fourteen patients received local anaesthetic and 13 patients received saline placebo. The anaesthetic group experienced a 22% reduction in pain scores 1 h postoperatively and a 48% reduction at 6 h although this failed to achieve statistical significance. However, the anaesthetic group were less likely to require morphine in recovery (2/14 [14%] versus 8/13 [62%]; P = 0.01). The high morphine requirements in the control group may have reduced the amount of pain those patients recorded on their pain scores and prevented statistical significance from being achieved.

CONCLUSION

In varicose vein surgery, local anaesthetic infiltration to the groin wound and along the full length of the stripper track is associated with reduced postoperative pain and requirements for opiate analgesia.

The opercular-subopercular syndrome: four cases with review of the literature

We present four cases of the 'opercular syndrome' of volitional paresis of the facial, lingual, and laryngeal muscles (bilateral facio-glosso-pharyngo-masticatory paresis). Case histories and CT brain images are presented, along with a review of the literature concerning this long-recognized but little-known syndrome. The neuroanatomic basis of the syndrome classically involves bilateral lesions of the frontal operculum. We propose, on the basis of our cases and others, that the identical syndrome can arise from lesions of the corticobulbar tracts, not involving the cortical operculum. Our cases included one with bilateral subcortical lesions, one with a unilateral left opercular lesion and a possible, non-visualized right hemisphere lesion, one with unilateral cortical and unilateral subcortical pathology, and one with bilateral cortical lesions. These lesion localizations suggest that any combination of cortical or subcortical lesions of the operculum or its connections on both sides of the brain can produce a syndrome indistinguishable from the classical opercular syndrome. We propose the new term 'opercular-subopercular syndrome' to encompass cases with predominantly or partially subcortical lesions.

Occipital pole area and language dominance

A previous report demonstrated a relationship between asymmetries of occipital lobe length measured on magnetic resonance images (MRIs) and the hemisphere verified as dominant for language. This study sought to discern whether asymmetry in occipital pole area is more predictive of the hemisphere dominant for language. Language dominance was identified by the Wada test in 55 patients evaluated for surgical treatment of epilepsy. In a blinded fashion, an examiner measured bilateral occipital pole area on MRIs for each patient. Asymmetry of the occipital pole area on the MRI made at 10 mm above the tentorium was significantly related to language dominance. This two-dimensional analysis was better than previously described linear measurements in discriminating patients with left-hemisphere dominance for language.

Crossed aphasia. Functional brain imaging with PET or SPECT

OBJECTIVES

To study patients with crossed aphasia (aphasia secondary to lesions in the right hemisphere in right-handed patients) with functional brain imaging using positron emission tomography (PET) or single photon emission computed tomography (SPECT); to see whether left hemisphere structures were metabolically depressed during the acute phase and, in 1 patient, during recovery; and to review the modern literature on crossed aphasia, with special reference to left hemisphere involvement.

DESIGN

Case studies of 3 patients with crossed aphasia, including language testing, computed tomographic scanning, and functional imaging with PET or SPECT.

SETTING

Hospital case studies.

PATIENTS

Three right-handed patients with crossed aphasia secondary to acute infarctions in the right hemisphere and left hemiparesis.

METHODS

All 3 patients were studied by means of bedside language testing, computed tomographic scanning, and functional brain imaging with PET or SPECT. Patient 1 also underwent serial testing with the Boston Diagnostic Aphasia Examination and follow-up PET scanning after 2 months of recovery.

OUTCOME MEASURES

Clinical examination in all 3 patients and follow-up Boston Diagnostic Aphasia Examination and PET scanning in patient 1.

RESULTS

Two patients had severe global aphasia and 1 had Broca aphasia. In all cases, computed tomographic scans failed to reveal any left hemispheric lesions. Functional imaging with PET or SPECT showed extensive hypometabolism or hypoperfusion in the right hemisphere, with initial reductions in the left hemisphere as well. In patient I, a follow-up PET image showed only persistent hypometabolism in the right hemisphere.

CONCLUSIONS

These findings suggest that abnormal dominance for at least some language functions in the right hemisphere underlies the syndrome of crossed aphasia. Diaschisis, or functional depression of the anatomically normal left hemisphere, was seen in all 3 patients during the acute phase, but not in patient 1 after recovery had begun.

99Tcm-HMPAO brain SPET in patients with pseudotumour cerebri

The aim of this study was to look for regional cerebral blood flow (rCBF) abnormalities in patients with a recent diagnosis of pseudotumour cerebri (PTC) and to compare 99Tcm-hexamethylpropylene amine oxime (99Tcm-HMPAO) cerebral single photon emission tomographic (SPET) findings with those of X-ray computed tomography (CT) and magnetic resonance imaging (MRI). Seventeen consecutive patients aged 14-50 years (mean = 29 years) without previous drug treatment for PTC underwent 99Tcm-HMPAO SPET, cranial CT and MRI studies. No patient had evidence of intracranial mass lesions on the CT or MRI scans. Qualitative analysis of the 99Tcm-HMPAO SPET studies revealed impaired rCBF in nine (53%) patients. The CT and MRI studies revealed an empty sella in two patients, dural sinus thrombosis in one and a slit ventricle in another. Eight of the 13 patients with normal CT and MRI results had rCBF abnormalities. In contrast, three patients with CT and MRI abnormalities had a normal 99Tcm-HMPAO scan. Our results suggest that patients with PTC have functional abnormalities that are revealed by 99Tcm-HMPAO brain SPET.

Paraneoplastic neurological syndrome in systemic cancer

Paraneoplastic syndrome refers to a group of disorders caused by or associated with cancers that are not direct effects of the primary tumor mass or a metastasis to the involved organs. Neurologically, the phrase describes a group of disorders that are diagnosed with increasing frequency in cancer patients. In this study, we investigated 36 patients with malignant diseases and various neurological paraneoplastic syndromes. Lung cancer is the most frequent malignancy associated with neurological paraneoplastic syndromes, and polyneuropathy is the most important manifestation among them.

Syndromes of language dissolution in aging and dementia

This article has reviewed the language deterioration of aging, dementia, and the syndrome of primary progressive aphasia. Language deterioration is generally mild in normal aging but is a universal accompaniment of dementing diseases. Isolated, progressive language disturbance, especially nonfluent aphasia, is the hallmark of the syndrome called ¿Primary Progressive Aphasia¿ or PPA. The language findings in these patients illustrate that distinctions between focal and generalized brain disease are difficult. Much remains to be learned about the spectrum of diseases that can produce progressive aphasia. The discovery of biological or genetic markers for these diseases is likely to lead to a better understanding of their behavioral characteristics.