Gregor Radonjič

Compatibilization of polypropylene/polystyrene blends with poly(styrene-b-butadiene-b-styrene) block copolymer

The compatibilizing effect of the triblock copolymer poly(styrene-b-butadiene-b-styrene) (SBS) on the morphology and mechanical properties of immiscible polypropylene/polystyrene (PP/PS) blends were studied. Blends with three different weight ratios of PP and PS were prepared and three different concentrations of SBS were used for investigations of its compatibilizing effects. Scanning electron microscopy (SEM) showed that SBS reduced the diameter of the PS-dispersed particles as well as improved the adhesion between the matrix and the dispersed phase. Transmission electron microscopy (TEM) revealed that in the PP matrix dispersed particles were complex “honeycomblike” aggregates of PS particles enveloped and joined together with the SBS compatibilizer. Wide-angle X-ray diffraction (WAXD) analysis showed that the degree of crystallinity of PP/PS/SBS slightly exceeded the values given by the addition rule. At the same time, addition of SBS to pure PP and to PP/PS blends changed the orientation parameters A110 and C significantly, indicating an obvious SBS influence on the crystallization process in the PP matrix. SBS interactions with PP and PS influenced the mechanical properties of the compatibilized PP/PS/SBS blends. Addition of SBS decreased the yield stress and the Youngs modulus and improved the elongation at yield as well as the notched impact strength in comparison to the binary PP/PS blends. Some theoretical models for the determination of the Youngs modulus of binary PP/PS blends were used for comparison with the experimental results. The experimental line was closest to the series model line.

Compatibilization effects of styrenic/rubber block copolymers in polypropylene/polystyrene blends

Compatibilizing effects of styrene/rubber block copolymers poly(styrene-b-butadiene-b-styrene) (SBS), poly(styrene-b-ethylene-co-propylene) (SEP), and two types of poly(styrene-b-ethylene-co-butylene-b-styrene) (SEBS), which differ in their molecular weights on morphology and selected mechanical properties of immiscible polypropylene/polystyrene (PP/PS) 70/30 blend were investigated. Three different concentrations of styrene/rubber block copolymers were used (2.5, 5, and 10 wt %). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to examine the phase morphology of blends. The SEM analysis revealed that the size of the dispersed particles decreases as the content of the compatibilizer increases. Reduction of the dispersed particles sizes of blends compatibilized with SEP, SBS, and low-molecular weight SEBS agrees well with the theoretical predictions based on interaction energy densities determined by the binary interaction model of Paul and Barlow. The SEM analysis confirmed improved interfacial adhesion between matrix and dispersed phase. The TEM micrographs showed that SBS, SEP, and low-molecular weight SEBS enveloped and joined pure PS particles into complex dispersed aggregates. Bimodal particle size distribution was observed in the case of SEP and low-molecular weight SEBS addition. Notched impact strength (ak), elongation at yield (ey), and Youngs modulus (E) were measured as a function of weight percent of different types of styrene/rubber block copolymers. The ak and ey were improved whereas E gradually decreased with increasing amount of the compatibilizer. The ak was improved significantly by the addition of SEP. It was found that the compatibilizing efficiency of block copolymer used is strongly dependent on the chemical structure of rubber block, molecular weight of block copolymer molecule, and its concentration. The SEP diblock copolymer proved to be a superior compatibilizer over SBS and SEBS triblock copolymers. Low-molecular weight SEBS appeared to be a more efficient compatibilizer in PP/PS blend than high-molecular weight SEBS.

The impact and significance of ISO 14001 certification on the adoption of new technologies

Purpose – The purpose of this paper is to assess whether environmental management systems (EMS) according to ISO 14001 requirements have contributed to the implementation and adoption of new technologies and to the issues related to technology performance in industrial enterprises.Design/methodology/approach – The research is based on the questionnaire survey conducted on a sample of ISO 14001 certified Slovene manufacturing companies.Findings – The results revealed that ISO 14001 certified manufacturing companies still mostly used the combination of partly adopted and partly modified technologies in order to reduce environmental impacts. ISO 14001 was considered as a very useful tool for the promotion of technological modernisation. It was shown also that ISO 14001 standard can play a significant role as a support tool for the acceleration of technological innovation activities regardless of the origin of the technology.Research limitations/implications – The research surveyed only industrial ISO 14001 c...

The use of ethylene/propylene copolymers as compatibilizers for recycled polyolefin blends

Compatibilizing effects of ethylene/propylene (EPR) diblock copolymers on the morphology and mechanical properties of immiscible blends produced from recycled low-density polyethylene (PE-LD) and high-density polyethylene (PE-HD) with 20 wt.-% of recycled poly(propylene) (PP) were investigated. Two different EPR block copolymers which differ in ethylene monomer unit content were applied to act as interfacial agents. The morphology of the studied blends was observed by scanning- (SEM) and transmission electron microscopy (TEM). It was found that both EPR copolymers were efficient in reducing the size of the dispersed phase and improving adhesion between PE and PP phases. Addition of 10 wt.-% of EPR caused the formation of the interfacial layer surrounding dispersed PP particles with the occurrence of PE-LD lamellae interpenetration into the layer. Tensile properties (elongation at yield, yield stress, elongation at break, Youngs modulus) and notched impact strength were measured as a function of blend composition and chemical structure of EPR. It was found that the EPR with a higher content of ethylene monomer units was a more efficient compatibilizer, especially for the modification of PE-LD/PP 80/20 blend. Notched impact strength and ductility were greatly improved due to the morphological changes and increased interfacial adhesion as a result of the EPR localization between the phases. No significant improvements of mechanical properties for recycled PE-HD/PP 80/20 blend were observed by the addition of selected block copolymers.

Phase morphology and mechanical properties of iPP/SEP blends

The effects of the addition of diblock copolymer poly(styrene-b-ethylene-co-propylene) (SEP) to isotactic polypropylene (iPP) on the morphology and mechanical properties were investigated. Phase morphologies of iPP/SEP blends up to a 70/30 weight ratio, prepared in Brabender Plasticoder, were studied with optical microscopy, scanning electron microscopy, transmission electron microscopy, and wide-angle X-ray diffraction. The addition of 2.5 wt % SEP caused a nucleation effect (by decreasing the crystallite and spherulite size) and randomization of the crystallites. With further SEP addition, the crystallite and spherulite size increased because of prolonged solidification and crystallization and achieved the maximum in the 80/20 iPP/SEP blend. This maximum was a result of the appearance of β spherulites and the presence of mixed α spherulites in the 80/20 iPP/SEP blend. Dispersed SEP particles were irregular and elongated clusters consisting of oval and spherical core–shell microdomains or SEP micelles. SEP clusters accommodated their shapes to interlamellar and interspherulitic regions, which enabled a well-developed spherulitization even in the 70/30 iPP/SEP blend. The addition of SEP decreased the yield stress, elongation at yield, and Youngs modulus but significantly improved the notched impact strength with respect to the strength of pure iPP at room temperature. Some theoretical models for the determination of Youngs modulus of iPP/SEP blends were applied for a comparison with the experimental results. The experimental line was closest to the Takayanagi series model.

Reliability of carbon footprint as a decision-making tool for product development – a critical review

Various methods exist for evaluating the environmental consequences of products. With climate change high up on the political and corporate agendas, carbon footprint (CF) calculations are in strong demand. However, there are certain serious shortcomings related to the CF concept which every practitioner and potential user should be aware of. Although building upon a life cycle approach, CF addresses only impacts on climate change that may give a misleading picture of the environmental impacts and shift environmental burdens to other impacted areas, thus leading to incomplete decisions for sustainable development policies. Another very important issue is how the CF results are presented to the customer. All these conceptual and methodological shortcomings demand better understanding of the value of CF results within product development and marketing activities. In addition, understanding of the uncertainties can be crucial for properly interpreting CF results.