Krzysztof Formela

Biowaste chicken eggshell powder as a potential cure modifier for epoxy/anhydride systems: competitiveness with terpolymer-modified calcium carbonate at low loading levels

Biowaste chicken eggshell (ES) powder was applied as a potential cure modifier in epoxy/anhydride systems. Cure behaviour and kinetics of composites filled with very low content (0.1 wt% based on epoxy resin) of ES, calcium carbonate (CaCO3), and terpolymer-modified fillers, mES and mCaCO3, were discussed comparatively. Surface analysis was performed by X-ray photoelectron spectroscopy. Cure kinetics was investigated by differential (Friedman) and integral (Ozawa and Kissinger–Akahira–Sunose) isoconversional methods using dynamic differential scanning calorimetry (DSC) data. Overall, protein precursors naturally existing in the structure of pristine ES facilitated crosslinking of epoxy and hardener of anhydride with functional groups resulting from terpolymer attachment to CaCO3 particles. Accelerated/hindered cure was observed depending on the filler type and surface characteristics, as investigated via the autocatalytic/non-catalytic nature of reactions and comparison of activation energy values of four types of composites. An enhanced cure was identified for composites containing untreated ES, which could be inferred on account of the lower competitive cure of carboxyl groups in the terpolymer backbone with epoxy compared to peptide groups existing in microporous pristine ES. On the other hand, mCaCO3 revealed low values of activation energy compared to pristine CaCO3, but still of the same order as ground biowaste ES.

Processing and structure–property relationships of natural rubber/wheat bran biocomposites

In this work, wheat bran was used as cellulosic filler in biocomposites based on natural rubber. The impact of wheat bran content [ranging from 10 to 50 parts per hundred rubber (phr)] on processing, structure, dynamic mechanical properties, thermal properties, physico-mechanical properties and morphology of resulting biocomposites was investigated. For better characterization of interfacial interactions between natural rubber and wheat bran, achieved results were compared with properties of biocomposites filled with commercially available cellulosic fillers—wood flour and microcellulose. It was observed that wheat bran, unlike commercial cellulosic fillers, contains high amount of proteins, which act like plasticizers having profitable impact on processing, physical, thermo-mechanical and morphological properties of biocomposites. This is due to better dispersion and distribution of wheat bran particles in natural rubber, which results in reduction of stiffness and porosity of the biocomposites. Regardless of cellulosic filler type, Wolff activity coefficient was positive for all studied biocomposites implying reinforcing effect of the applied fillers, while tensile strength and elongation at break decreased with increasing filler content. This phenomenon is related to restricted strain-induced crystallization of NR matrix due to limited mobility of polymer chains in the biocomposites. Furthermore, this explains negligible impact of particle size distribution, chemical composition and crystallinity degree of applied cellulosic filler on static mechanical properties of highly-filled NR biocomposites. The conducted investigations show that wheat bran presents interesting alternative for commercially available cellulosic fillers and could be successfully applied as a low-cost filler in polymer composites.

The emissions of monoaromatic hydrocarbons from small polymeric toys placed in chocolate food products

The article presents findings on the emissions of selected monoaromatic hydrocarbons from childrens toys placed in chocolate food products. The emission test system involved the application of a new type of microscale stationary emission chamber, μ-CTE™ 250. In order to determine the type of the applied polymer in the manufacture of the tested toys, Fourier transform infrared spectroscopy and thermogravimetric analysis coupled with differential scanning calorimetry were used. It was found that the tested toy components or the whole toys (figurines) are made of two main types of polymers: polyamide and acrylonitrile-butadiene-styrene copolymer. Total number of studied small polymeric toys was 52. The average emissions of selected monoaromatic hydrocarbons from studied toys made of polyamide were as follows: benzene: 0.45 ± 0.33 ng/g; toluene: 3.3 ± 2.6 ng/g; ethylbenzene: 1.4 ± 1.4 ng/g; p,m-xylene: 2.5 ± 4.5 ng/g; and styrene: 8.2 ± 9.9 ng/g. In the case of studied toys made of acrylonitrile-butadiene-styrene copolymer the average emissions of benzene, toluene, ethylbeznene, p,m-xylene and styrene were: 0.31 ± 0.29 ng/g; 2.5 ± 1.4 ng/g; 4.6 ± 8.9 ng/g; 1.4 ± 1.1 ng/g; and 36 ± 44 ng/g, respectively.

Polyurethane/ground tire rubber composite foams based on polyglycerol: Processing, mechanical and thermal properties

During the synthesis of rigid polyurethane foams, petrochemical polyol was substituted with polyglycerol, the product of thermo-catalytic polycondensation of waste glycerol, resulting from biodiesel production. Two types of ground tire rubbers, untreated and thermo-mechanically reclaimed, were used to obtain “green” polyurethane-polyglycerol composite foams. Samples were prepared by a single-step method for the ratio of NCO/OH groups equal to 2. Foams containing different types of fillers showed noticeably various appearances, which suggested significant differences in the matrix–filler interactions between materials modified with untreated and reclaimed ground tire rubber. Addition of rubber particles shortened the processing time by more than 20 s and reduced the temperature during synthesis. Incorporation of ground tire rubber increased the size of the cells in comparison to unmodified foam. Modifications of rigid polyurethane foams resulted in the increase of apparent density and compressive strength even by 40% compared to neat foam. Enhancement was stronger for samples containing thermo-mechanically reclaimed ground tire rubber as a result of better developed surface of filler particles and their interfacial interactions with polyurethane matrix. Prepared polyurethane foams filled with untreated rubber particles also showed slightly enhanced thermal stability compared to neat foam.

An investigation on the role of GMA grafting degree on the efficiency of PET/PP-g-GMA reactive blending: morphology and mechanical properties

Glycidyl methacrylate (GMA) has been grafted on polypropylene (PP) with the aid of styrene (St) comonomer, by changing dicumyl peroxide initiator content, GMA level, and St concentration. The performance of the resulting PP-g-GMA reactive material towards static and dynamic mechanical properties of poly (ethylene terephthalate) (PET) was monitored in terms of grafting reaction variables and compatibilizer content. Fourier transform infrared spectroscopy, scanning electron microscopy, mechanical properties, melt flow rate, and impact strength analyses were applied to correlate structural changes due to grafting (or undesired chain scission) with blends’ properties. The competition between the desired reaction, i.e., GMA grafting onto PP chain, and undesired chain scission of PP macroradicals due to thermal degradation, was discussed based on torque–time curves and mechanical properties. Manipulation of grafting variables was responsible for a special behavior over properties, means that optimal or ascending/descending trends, which noticed high sensitivity of PET toughening to GMA grafting efficiency.

Rigid polyurethane foams modified with ground tire rubber - mechanical, morphological and thermal studies

Rigid polyurethane foams, prepared by a single step method, were modified with the two types of ground tire rubber particles, i.e. untreated and thermo-mechanically reclaimed using a co-rotating twin screw extruder. The foaming process as well as the structure and the physical, mechanical and thermal properties of the resulting foams were investigated. The presence of ground tire rubber decreased the rate of polymerization. The incorporation of ground tire rubber decreased the total crosslink density of the produced material, as confirmed by a decrease in glass transition temperature measured by dynamic mechanical analysis and differential scanning calorimetry. The temperatures associated with a 10% and 50% mass loss of foam, determined by thermogravimetric analysis, increased due to the addition of ground tire rubber particles.

Controlled grafting of vinylic monomers on polyolefins: a robust mathematical modeling approach

Abstract Experimental and mathematical modeling analyses were used for controlling melt free-radical grafting of vinylic monomers on polyolefins and, thereby, reducing the disturbance of undesired cross-linking of polyolefins. Response surface, desirability function, and artificial intelligence methodologies were blended to modeling/optimization of grafting reaction in terms of vinylic monomer content, peroxide initiator concentration, and melt-processing time. An in-house code was developed based on artificial neural network that learns and mimics processing torque and grafting of glycidyl methacrylate (GMA) typical vinylic monomer on high-density polyethylene (HDPE). Application of response surface and desirability function enabled concurrent optimization of processing torque and GMA grafting on HDPE, through which we quantified for the first time competition between parallel reactions taking place during melt processing: (i) desirable grafting of GMA on HDPE; (ii) undesirable cross-linking of HDPE. The proposed robust mathematical modeling approach can precisely learn the behavior of grafting reaction of vinylic monomers on polyolefins and be placed into practice in finding exact operating condition needed for efficient grafting of reactive monomers on polyolefins.

In situ processing of biocomposites via reactive extrusion

Abstract Law regulations, economic and environmental factors are the main causes for the rapidly growing interests in biocomposites’ research, conducted currently in a number of academic and industrial scientific centres. However, weak polymer matrix/filler interactions, common in biocomposites, result in unsatisfactory mechanical properties, which limit their practical applications. From many attempts performed to solve this problem, in situ reactive extrusion is gaining lately a noticeable attention as a cost-effective manufacturing technique with the possibility of increasing the level of interfacial adhesion. Moreover, reactive extrusion enables in situ polymerization of matrix, modification of biodegradable polymers, functionalization of biofillers, or chemical bonding between filler and matrix phases and usually can be performed on commonly used extrusion lines. This chapter presents recent advances in processing of biocomposites via reactive extrusion, including a discussion about its advantages and limitations. The compatibilization mechanisms for different types of polymer matrices and fillers are presented. Furthermore, future trends and development in reactive extrusion of biocomposites are discussed.

Chromatografia gazowa jako narzędzie kontroli procesu wytłaczania materiałów polimerowych

Praca stanowi literaturowy przegląd mozliwości wykorzystania chromatografii gazowej (GC) jako narzedzia kontroli procesu wytlaczania materialow polimerowych. Przedstawiono charakterystyke techniki GC oraz mozliwości, jakie niesie ze sobą kontrola fazy gazowej uwalnianej podczas przetworstwa materialow polimerowych. Na podstawie dotychczas opublikowanych prac badawczych omowiono techniki i metody wykorzystywane do izolacji lotnych związkow organicznych z fazy gazowej generowanej podczas procesu wytlaczania.Praca stanowi literaturowy przegląd mozliwości wykorzystania chromatografii gazowej (GC) jako narzedzia kontroli procesu wytlaczania materialow polimerowych. Przedstawiono charakterystyke techniki GC oraz mozliwości, jakie niesie ze sobą kontrola fazy gazowej uwalnianej podczas przetworstwa materialow polimerowych. Na podstawie dotychczas opublikowanych prac badawczych omowiono techniki i metody wykorzystywane do izolacji lotnych związkow organicznych z fazy gazowej generowanej podczas procesu wytlaczania.

Structure and performance properties of environmentally-friendly biocomposites based on poly(ɛ-caprolactone) modified with copper slag and shale drill cuttings wastes

The potential application of two types of industrial wastes, drill cuttings (DC) and copper slag (CS), as silica-rich modifiers of poly(ɛ-caprolactone) (PCL) was investigated. Chemical structure and physical properties of DC and CS fillers were characterized using X-ray diffractometer, X-ray fluorescence spectroscopy, particle size and density measurements. PCL/DC and PCL/CS composites with a variable content of filler (5 to 50 parts by weight) were prepared by melt compounding in an internal mixer. It was observed that lower particle size of DC filler enhanced processing of biocomposites comparing to CS filler. Smaller particles of DC filler and thus the higher specific surface area, enabled better encapsulation of filler by polymer chains, hence lower porosity and consequently higher tensile properties comparing to PCL/CS biocomposites. It was noticed, that the impact of waste filler characteristics on tensile properties became negligible at higher loadings. This indicates weak interactions between waste filler and PCL matrix, due to aggregation of filler particles and formulation of voids in phase boundary. This phenomenon was confirmed by scanning electron microscopy, headspace analysis and thermogravimetric analysis. Microbial tests revealed that prepared biocomposites show no toxic effect towards analyzed bacterial strains, therefore could be considered as environmentally-friendly.