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Surface morphology and bulk structure of polylactide (PLA) modified with halloysite nanotubes (HNT) treated with N,N’-ethylenebis(stearamide) (EBS) and untreated, as well as reference materials – PLA, EBS, and a blend of PLA with EBS, were examined. HNT is known to improve PLA properties, including mechanical and barrier properties. The materials were cold crystallized and tested using DSC, TGA, PLM, SALS, SEM, AFM. The additives affected nucleation and crystallization of PLA, but did not influence crystallinity, which was of approx. 37–40 %. In bulk, PLA crystallized in the form of spherulites in all materials. However, on surfaces of EBS-containing materials, a thin EBS layer with domain morphology was found. The EBS layer induced epitaxial crystallization of PLA in the form of parallel stacks of edge-on lamellae, the phenomenon reported for this polymer pair for the first time. It was observed in PLA with EBS modified HNT and in the PLA blend with EBS. Moreover, the EBS layers imparted hydrophobicity to the EBS-containing materials.

The influence of macromolecular architecture on shear-induced crystallization of poly(L-lactide) (PLLA) was studied. To this aim, three star PLLAs, 6-arm with Mw of 120 and 245 kg/mol, 4-arm with Mw of 123 kg/mol, and three linear PLLAs with Mw of 121, 240 and 339 kg/mol, were synthesized and examined. The PLLAs were sheared at 170 and 150 °C, at 5/s, 10/s and 20/s for 20 s, 10 s and 5 s, respectively, and then cooled at 10 or 30 °C/min. Shear-induced crystallization during cooling was followed by a light depolarization method, whereas the crystallized specimens were examined by DSC, 2D-WAXS, 2D-SAXS and SEM. The effect of shear depended on the shearing conditions, cooling rate and polymer molar mass but it was also affected by the macromolecular architecture. The shear-induced crystallization of linear PLLA with Mw of 240 kg/mol was more intense than that of the 6-arm polymer with similar Mw, most possibly due to its higher Mz. However, the influence of shear on the crystallization of the star polymers with Mw close to 120 kg/mol was stronger than on that of their linear analog. This was reflected in higher crystallization temperature, as well as crystallinity achieved during cooling.

The influence of the crystallization temperature and the pressure on the crystallization kinetics, structure and compression strength of γ-polypropylene was investigated. Samples were produced in a custom-made high-pressure crystallization cell and characterized by differential scanning calorimetry (DSC), wide angle X-ray scattering (WAXS) and transmission electron microscopy (TEM). It could be shown that the strength is mainly affected by the mean lamellar thickness. The strength of γ-PP is at least 40% higher than α-PP at the same mean lamellar thickness. This confirms the hypothesis that the arrangement of non-parallel chains restricts the number of possible slip systems so that almost no mobile dislocations are generated. The mode of nucleation is only slightly affected by the crystallization pressure. The Avrami coefficient is n = 2.5 ± 0.1 at the beginning of crystallization and largely independent of pressure.

Electrically conductive composite polypropylene and poly(ethylene terephtalate) fabrics were obtained by coating with organo-silicon sol containing dispersed graphene particles. The graphene-modified coating was deposited on the fabric using the sol-gel method and the padding technique. To improve bonding of the coating to the fiber surfaces, the latter were activated with atmospheric pressure plasma in the form of corona discharge. The activation resulted in chemical and structural changes of the surfaces, roughening, and the formation of oxygen-containing functional groups, as evidenced by SEM with 3D analysis, EDS and XPS, and also measurements of contact angles with liquids. The padding with graphene-containing organo-silicon sol imparted electrical conductivity to the polymer fabrics. It was found that the pre-coating activation improved durability of the coating and stability of the electrical properties due to better bonding between the conducting coating and the fiber surfaces.

Electrical conductivity was imparted to a cotton fabric through thermal reduction of graphene oxide. The reduction was enhanced by commercial antioxidants used in the plastics industry. The cotton fabric was coated with GO by the padding method and dipped in antioxidant solution. After drying, the antioxidant assisted reduction of GO was conducted at 220 °C in air. The electrical properties and hydrophobicity of thus-modified fabric were examined. The structure of materials was analyzed by atomic force microscopy and scanning electron microscopy. Application of the antioxidants permitted to reach lower values of surface electrical resistivity of the fabric. After the reduction all fabric samples became hydrophobic.

Dual-component fibrous materials were produced by co-extrusion and multiplication technology in combination with a water jet procedure. High density polyethylene/poly(vinylidene fluoride) (HDPE/PVDF) and polypropylene/high density polyethylene (PP/HDPE) systems were obtained. Modification of these fibrous materials with multiwall carbon nanotubes imparted electrical conductivity. Methyltrichlorosilane treatment permitted to reach superhydrophobicity reflected in a water contact angle (WCA) ≥ 160°. Both types of modification decreased a pore size of HDPE/PVDF fibrous material and strongly increased its surface area. The material subjected to both treatments possess pore size of 3.1 μm. This electrically conductive and superhydrophobic HDPE/PVDF fibrous material is characterized by WCA of 164° and low surface resistivity of 87.4 Ω/sq. Electrochemical modification using cyclic voltammetry resulted in the formation of silver nanoparticles (Ag°) on surfaces of the fibers, which imparted antibacterial properties against Staphylococcus aureus and Escherichia coli. Keywords: Smart materials, Dual-component fibrous materials, Lotus effect, Multiwall carbon nanotubes, Cyclic voltammetry

Ternary blends of polylactide (PLA, 90 wt.%) and poly(methyl methacrylate) (PMMA, 10 wt.%) with functionalized polysilsesquioxanes (LPSQ-R) were obtained by solution blending. R groups in LPSQ containing hydroxyethyl (LPSQ-OH), methylglycolic (LPSQ-COOMe) and pentafluorophenyl (LPSQ-F5) moieties of different chemical properties were designed to modify PLA blends with PMMA. The effect of the type of LPSQ-R and their content, 1–3 wt.%, on the structure of the blends was studied with scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (SEM-EDS), dynamic mechanical thermal analysis (DMTA) and Raman spectroscopy. Differential scanning calorimetry (DSC) and tensile tests also showed various effects of LPSQ-R on the thermal and mechanical properties of the blends. Depth-sensing indentation was used to resolve spatially the micro- and nano-scale mechanical properties (hardness and elastic behaviour) of the blends. The results showed clearly that LPSQ-R modulate the structure and properties of the blends.

Electrospun nonwovens of poly(L-lactide) (PLLA) modified with multiwall carbon nanotubes (MWCNT) and linear ladder-like poly(silsesquioxane) with methoxycarbonyl side groups (LPSQ-COOMe) were obtained. MWCNT and LPSQ-COOMe were added to the polymer solution before the electrospinning. In addition, nonwovens of PLLA grafted to modified MWCNT were electrospun. All modified nonwovens exhibited higher tensile strength than the neat PLA nonwoven. The addition of 10 wt.% of LPSQ-COOMe and 0.1 wt.% of MWCNT to PLLA increased the tensile strength of the nonwovens 2.4 times, improving also the elongation at the maximum stress.

Linear ladder polysilsesquioxanes (LPSQ-R) bearing fluoroaryl groups [R: p-fluorophenyl (F), p-trifluoromethylphenyl (F3) or pentafluorophenyl (F5)] were used to modify polylactide (PLA). Vibrational spectroscopy analysis suggested specific, non-covalent interactions between C O of PLA and fluoroaryl groups of LPSQ-R while quantum-chemical modelling performed for representative models indicated that the pattern of possible preferred contacts differs for LPSQ-F3 in respect to LPSQ-F and LPSQ-F5 (H····F hydrogen bonding against n→π* attractive interactions). It may affect interface phenomena in PLA/LPSQ-R systems. Thermal characteristics of PLA/LPSQ-R depended on the type of R and LPSQ-R content. Dielectric relaxation spectroscopy (DRS) studies revealed one relaxation process present in PLA and related to the glass transition. However, for PLA/LPSQ-R blends two processes were identified: glass transition and normal–mode relaxation. The modification with fluorinated macromolecules increased hydrophobicity of amorphous PLA and improved its mechanical and gas barrier properties, which can be of importance for packaging applications.

1,3:2,4-bis(3,4-dimethylbenzylidene)sorbitol (DMDBS) is highly effective in nucleation of the &alpha, form of isotactic polypropylene (iPP). However, its role in high-pressure crystallization of iPP, facilitating the formation of the &gamma, polymorph, has not been explored. The present paper focuses on the influence of DMDBS on nucleation of high-pressure crystallization of iPP. iPP with 0.2&ndash, 1.0 wt.% of the DMDBS was crystallized under elevated pressure, up to 300 MPa, in various thermal conditions, and then analyzed by PLM, WAXD, SEM, and DSC. During cooling, crystallization temperatures (Tc) were determined. It was found that under high-pressure DMDBS nucleated crystallization of iPP in the orthorhombic &gamma, form. As a consequence, Tc and the &gamma, form content increased for the nucleated iPP, while the size of polycrystalline aggregates decreased, although the effects depended on DMDBS content. The significant increase of Tc and the decrease of grain size under high pressure of 200&ndash, 300 MPa required higher content of DMDBS than the nucleation of the &alpha, form under lower pressure, possibly due to the effect of pressure on crystallization of DMDBS itself, which is a prerequisite for its nucleating activity.

Three star-shaped poly(ʟ-lactide)s (PLLAs) were synthesized, two 6-arm with Mw of 120 and 245 kg/mol and one 4-arm with Mw of 123 kg/mol. Linear PLLAs with Mw of 121 and 339 kg/mol were also prepared. Crystallization, both isothermal and nonisothermal, of all PLLAs was studied by means of DSC. The growth rate of spherulites was measured in a broad range of crystallization temperature using PLM. At Mw close to 120 kg/mol the star architecture slowed down the spherulite growth above 120 °C, up to 145 °C. The spherulite growth in PLLAs with Mw > 200 kg/mol was slower than that in the other polymers and unaffected by the macromolecule architecture. The differences in the spherulite growth rate were reflected in overall crystallization kinetics in isothermal conditions and also in crystallization peak temperature and crystallinity developed during cooling. The highest crystallinity developed during isothermal crystallization in linear and 6-arm PLLAs with Mw close to 120 kg/mol, whereas the lowest in PLLAs with Mw > 200 kg/mol. For Mw > 200 kg/mol the star architecture decreased the melting temperature. The glass transition temperature of all PLLAs was the same, at 61–62 °C, regardless of Mw and macromolecule architecture.

Pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), an antioxidant widely applied in the plastic industry, was used to assist thermal reduction of graphene oxide (GO) on a cotton fabric in air. l-ascorbic acid was also applied for comparison. GO was deposited on the fabric by the padding method. Reduction of GO deposited on fiber surfaces at 180 and 220 °C in air imparted electrical conductivity. For all the materials the conductivity worsened after the reduction during cooling and during the first hours of storage at room conditions. However, the most stable effect of GO reduction was achieved using pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), which assisted the reduction of GO at both 180 and 220 °C, and allowed to obtain the cotton fabric with a stable surface resistivity of 6.6 and 3.7 MΩ/sq, respectively. Moreover, superhydrophobicity of the conductive fabric was achieved by modification with methyltrichlorosilane in an anhydrous environment.

Composites of syndiotactic polypropylene (sPP) with 5 to 17 vol.° of halloysite and 2.5 to 7.5 vol.° of stearic acid modified nano-calcium carbonate, having an average grain size of 80 nm, were prepared and examined. The effect of fillers on thermal properties of sPP was different; halloysite increased markedly peak crystallization temperature. The composites with the highest filler contents, 7.5 vol.° of calcium carbonate and 17 vol.° of halloysite, exhibited a solid-like behavior at 170 °C, with the storage modulus exceeding the loss modulus in the entire frequency range, that is 512 to 0.1 rad s−1. The composites with halloysite exhibited decreased Izod impact strength compared to neat sPP. On the contrary, 2.7 fold improvement of the impact strength was found for the composites with nano-calcium carbonate. Moreover, nano-calcium carbonate did not worsen the drawability of the materials during uniaxial drawing. It was found that debonding at calcium carbonate/sPP interface occurred both during the impact test and tensile drawing facilitating the plastic deformation of the polymer.

The relations between crystalline structure and micromechanical properties of α-, β- and γ-phase of isotactic polypropylene (iPP) were investigated. The iPP samples with various crystalline phase compositions were prepared by a controlled high-pressure crystallization that enabled us to obtain not only α-iPP and β-iPP modifications, but also a series of almost pure γ-iPP samples with gradually changing morphology, crystallinity and lamellar thickness. The micromechanical properties were assessed by instrumented microindentation hardness testing (MHI), from which we determined indentation hardness (HIT), indentation modulus (EIT), indentation creep (CIT) and elastic part of the indentation work (ηIT). It was demonstrated that γ-iPP does not necessarily exhibit better mechanical performance than α- and β-iPP, as suggested by some previous studies, because the final properties are strongly influenced not only by the phase composition (i.e. by the content of α-, β- and γ-phase), but also by the overall crystallinity.

Poly(lactide)/halloysite nanotubes (PLA/HNT) nanocomposites with crystalline matrix were obtained by cold crystallization and examined. Neat HNT and HNT treated with N,N′- ethylenebis(stearamide) (EBS) were used as nanofillers. Reference materials, PLA and PLA/EBS blend, prepared in the same way, were also considered. The influence of HNT and/or EBS content on the crystallinity and morphology of PLA matrix, as well as on the dynamic mechanical and optical properties of the materials, was determined. The nanocomposites contained well-distributed HNT, with only occasional agglomerates. HNT, EBS-treated HNT and EBS influenced the morphology of the crystalline PLA matrix and the amounts of the disorder α’ (termed also δ) and order α crystallographic forms of PLA. Crystallinity increased stiffness of the materials compared to their counterparts with the amorphous matrix. Owing to the crystallinity and the presence of the nanofillers, the storage modulus at 20 °C and 60 °C increased by up to 30 and 60%, respectively, compared to neat amorphous PLA. Interestingly, at lower nanofiller content the crystalline nanocomposites with EBS were more transparent than neat crystalline PLA.

Thermal and mechanical properties of polylactide (PLA) composites with different grades of calcium carbonate, 40 nm and 90 nm nanoparticles, and also with submicron particles, unmodified and modified with calcium stearate or stearic acid, obtained by melt mixing, were compared. Films with amorphous and crystalline matrices were prepared and examined. Tg of PLA in the composites remained unaffected whereas its cold crystallization was enhanced by the fillers and predominantly depended on filler content. Filling decreased thermal stability of the materials but their 5% weight loss temperatures well exceeded 250 °C, evidencing stability in the temperature range of PLA processing. The amorphous nanocomposites with modified nanoparticles exhibited improved drawability and toughness without a significant decrease of tensile strength; nearly two-fold increase of the elongation at break and tensile toughness was achieved at 5 wt% content of the modified nanofiller. Lack of surface modification of the filler, larger grain size with an average of 0.9 μm, and matrix crystallinity had a detrimental effect on the drawability. However, the presence of nanofillers and crystallinity improved tensile modulus of the materials by up to 15% compared to neat amorphous PLA.

Amorphous polylactide/halloysite nanotube (PLA/HNT) nanocomposites were prepared and examined. Neat HNT and HNT treated with N,N' - ethylenebis(stearamide) (EBS) were used as nanofillers. The role of HNT and/or EBS content on the cold crystallization of amorphous PLA matrix, HNT dispersion, as well as on the dynamic mechanical and optical properties of the materials was determined. The PLA/HNT-based nanocomposites contained well-distributed nanotubes and occasionally micron-sized aggregates, especially at high loading. HNT, EBS treated HNT and EBS influenced the cold crystallization of PLA, therefore the formation of the disorder α′ and the order α crystallographic forms of PLA. The nanocomposites exhibited increased stiffness and decreased transparency compared to the neat PLA. Due to the reinforcing effect and additional specific features of HNT, the addition of the nanofiller allows tuning of the properties of the nanocomposites with amorphous PLA matrix.

Cotton fabrics were modified by xerogel coatings with dispersed particles of graphene (Gr) or reduced graphene oxide (RGO). To obtain a stable dispersion of Gr or RGO in organo-silicon sol, sodium lauryl sulfate as an anionic surfactant was used. The fabrics were padded with the organo-silicon sol containing dispersed Gr or RGO, forming a thin xerogel coating after drying. The fabrics coated with the xerogel containing 0.5–1.5 wt% of RGO or Gr were prepared and examined. The best anti-static properties were obtained for the coating with 1.5 wt% of Gr, whose surface resistance and volume resistance were on the order of 105 and 103 Ω, respectively. Such properties make the fabric suitable for protective cloths in the environment with explosive atmosphere.

Polylactide (PLA) composites with 10–30 wt% of commercial fine grain filler of native cellulose were prepared by melt-mixing, and examined. The composite films had esthetic appearance, glossy surface, creamy color and density close to that of neat PLA. Good dispersion of the filler in PLA matrix was achieved. The composites were stiffer than neat PLA; in the glassy region the storage modulus increased by approx. 30 %. The tensile strength of the composite materials in the temperature range from 25 to 45 °C was similar to that of neat PLA. No marked decrease in molar mass of PLA in the composites occurred during processing in comparison to neat PLA. Moreover, thermogravimetry experiments demonstrated good thermal stability of the composites; 5 % weight loss occurred well above 300 °C.

Shear-induced nonisothermal crystallization of two commercial polylactides (PLAs) differing in optical purity was studied. The molten polymers were sheared at selected temperatures (Ts) and subsequently cooled. The crystallization was followed by a light depolarization method, whereas the specimens were analysed ex-situ by DSC, 2D-WAXS and SEM after etching. It was found that the effect of shear, especially on the crystallinity developed during post-shearing cooling, intensified with a decrease of Ts from 160 to 146 °C, and with increasing shear rate and strain. Moreover, the effect of shear on PLA1.5 with d -lactide content of 1.5% was stronger than PLA2.8 with 2.8% of d -lactide, although maximum crystallinity of both polymers was practically the same. A decrease of cooling rate from 30 to 10 °C/min increased crystallinity of both PLAs, except for those shearing conditions which induced high crystallinity even during faster cooling. Although SEM examination revealed some row-nucleated forms, no significant crystal orientation was detected by 2D-WAXS, indicating that, under the experimental conditions, the shear induced predominantly point-like nuclei.

The influence of gold nanoparticle morphology on nucleation of isotactic polypropylene (PP) crystallization was investigated. Previous experiments indicated certain nucleation activity of gold nanoparticles, varying with their size. In this work, eight types of gold micro/nanoparticles were used: vacuum-sputtered nanostructures (nanoparticles, nanoislands, and nanolayers), chemically prepared isometric gold nanocrystals (5, 20, and 100 nm diameters), and two types of gold microcrystals with well-developed crystal facets [with (100) and (111) facets, respectively]. To minimize the effect of particle agglomeration, we used our recently introduced sandwich method, in which the nucleating agent was deposited between thin PP films and the nucleation was evaluated by polarized light microscopy (PLM), X-ray scattering (WAXS), and differential scanning calorimetry (DSC). The nucleation activity of Au particles in PP was lower than it might be expected from the previous studies and depended on their morpho...

Nonwovens of commercially available polylactide (PLA) were produced by electrospinning using laboratory scale equipment. The nonwovens were subsequently coated with an aqueous dispersion of multiwall carbon nanotubes (MWCNT), using the padding technique. MWCNT formed 3D networks on fiber surfaces making the nonwovens electrically conducting, with surface electrical resistivity of 77 Ω/sq – 680 Ω/sq. Modification of the nonwovens with methyltrichlorosilane made them superhydrophobic, what was reflected in the water contact angles of 160 − 175°. In turn, electrochemical deposition of silver particles (Ag°) on the conductive nonwovens imparted antibacterial activity against Staphylococcus aureus (gram-positive) and Escherichia coli (gram-negative).

Oligomeric ladder silsesquioxanes (LPSQ-R) with side substituents (R = COOH, COOMe, OH) capable of acceptor/donor interactions through hydrogen bonds were used for the preparation of blends with polylactide (PLA). Depending on the strength of their interactions with the PLA, LPSQ-R were differently dispersed in the polyester matrix. The blends exhibited different properties and crystallization behaviour depending on the type and content of LPSQ-R. PLA/LPSQ-COOMe exhibited good transparency. Owing to very good dispersion of the modifier, PLA with 5 wt% of LPSQ-COOMe was ductile, which was reflected in nearly 230% elongation at break, retaining however relatively high yield strength of nearly 40 MPa. Moreover, the spherulite growth rate was accelerated in PLA/LPSQ-COOMe, which caused enhancement of the cold-crystallization. In turn, cold-crystallization of PLA/LPSQ-OH was enhanced by strong nucleation.

The influence of shear on non-isothermal crystallization of commercial poly(butylene adipate-co-terephthalate) (PBAT) was investigated. PBAT melt was sheared at 130 and 150 °C at rates of 10–100/s, and then cooled. The crystallization was followed by a light depolarization technique, whereas the crystallized specimens were analyzed by DSC, 2D-SAXS, 2D-WAXS, PLM and SALS. Shear flow shifted crystallization to higher temperature, and the effect was augmented by lower temperature of shearing as well as by higher shear rate and strain. Crystallization peak rate temperature of PBAT, sheared at 130 °C for 5 min at 100/s, increased by up to 12 °C. However, no evidence of crystal orientation due to shear was found, indicating that the shear induced the point-like nucleation. Only a small increase of melting peak temperatures, by up to 2–5 °C, was observed for the specimens sheared at the highest rates (≥50/s).

Electrical conductivity and hydrophobicity was imparted to a cotton fabric through a sol-gel method by coating with an organosilicon sol containing dispersed graphene oxide (GO). The coating was followed by thermal treatment causing GO reduction and completion of cross-linking reactions. To enhance the reduction, a reductive sol was synthesized from alkoxysilanes with active groups obtained in the hydrolysis and condensation reactions. A siloxane oligomer with covalently bonded –SiH groups was used as a reducing component. The reductive sol was analyzed by means of 1H and 29Si NMR spectroscopy and ATR FTIR. Surface electrical resistivity and hydrophobicity/philicity of the modified fabric were determined, whereas the fiber surfaces were analyzed by SEM. The resistivity of 2.7 MΩ/sq and water contact angle of approx. 150° was reached. Electrical resistance of the coated fabric was sensitive to strain but returned to its initial value after the strain release. Moreover, neither the electrical conductivity nor hydrophobicity worsened after intense sonication, unlike in the case of reference fabric sample prepared by coating with GO alone and GO thermal reduction.

Nucleating agents used for the monoclinic α-form of isotactic polypropylene (PP), commonly occurring under atmospheric pressure, are able to nucleate its crystallization in the orthorhombic γ-form under high pressure. Nucleation of γ-lamellae is possible through epitaxy involving (001)γ crystallographic plane on substrates nucleating the α-form through epitaxy engaging (010)α plane because of equivalency of both planes. Another possibility is nucleation of α-lamellae through epitaxy involving either (010)α or (110)α plane, and formation of the γ-phase through γ/α epitaxy. The study focuses on the structure and mechanism of nucleation of high pressure crystallization of PP with selected nucleating agents: poly(tetrafluoroethylene) particles, commercial Hyperform HPN-20E and ADK Stab NA11UH. The nucleated PP was isothermally crystallized in the γ-form under pressure of 200 and 300 MPa and studied ex-situ by WAXD, PLM and SEM. Analysis of lamellar structure provided insight into the nucleation mechanism of high pressure crystallization of PP. In all the materials the α-lamellae were nucleated first and served as seeds for the γ-form.

Aromatic component of biodegradable aliphatic–aromatic random copolyester crystallizes. A strong self-nucleation is active with self-nuclei stable below 160 °C. Without self-nuclei the peak crystallization temperature decreases by 25 °C during subsequent cooling. The activity of self-nuclei was incentive to find artificial nucleating agents. Green phthalocyanine, blue phthalocyanine and talc were found to be effective nucleating agents for aliphatic–aromatic copolyester in absence of self-nuclei, increasing both the peak crystallization temperature and the density of nucleation. Crystallization of aliphatic–aromatic copolyester led to the formation of spherulites filling the entire volume of the material although aromatic crystal amounted to 10% of entire volume. SAXS analysis and AFM imaging showed that crystals are neither lamellar nor aligned in stacks. Instead, the crystals are formed as narrow, 3–4 nm thick fibrils radiating from spherulite centers. Crystallization of nucleated copolyester proceeds during cooling in a very peculiar way: first long fibrils are formed that partially immobilize the rest of material. During further cooling partially confined melt crystallizes in the form of short fibrils, however, in significantly smaller amount. The strangest outcome of artificial nucleation is that the crystallinity degree of nucleated copolyester is lower than nonnucleated. By short annealing at 70 °C long fibrils decompose by partial melting and capillary instability freeing the material from constraints.

The influence of diamond powders on properties of isotactic polypropylene (PP) was investigated. PP composites containing 0.2—5 wt % of the powders with particles of average size between 100 nm and 1 μm were prepared, and their structure and properties were examined. Dispersion of each filler depended on its grain size and content. The presence of fillers raised the crystallization temperature of PP matrix by up to few Celsius degrees. The modulus of elasticity of composites increased with increasing filler content, by up to 40 % in comparison to neat PP. The tensile impact strength of the composites with 1 μm powders and also the other composites at the filler content as low as 0.2 wt % improved by up to 30 %. The composites did not exhibit any decrease in the yield strength and retained good drawability. The elongation at break exceeded 1000 % in most cases. Examination of the uniaxially drawn specimens revealed that the filler grains separated from the PP matrix during drawing.

In order to modify its physical properties, particularly the drawability and toughness, polylactide (PLA) was melt blended with a set of PEG-b-PPG-b-PEG block copolymers with varying ratio of the hydrophilic (PEG) and hydrophobic (PPG) blocks. Miscibility of the copolymers with PLA depended on their molar mass and PEG content. Interestingly, the best drawability was achieved in the case of partially miscible blends, in which fine liquid inclusions of the modifier were dispersed in PLA rich matrix with glass transition temperature only moderately decreased, to about 50 °C. About 37 fold increase of the elongation at break and about 1.5 fold increase of the tensile impact strength with respect to neat PLA were reached at small content (10 wt.%) of the modifier. Despite the phase separation, the blends remained transparent. In addition, the barrier properties for oxygen were improved.

Polylactide (PLA) was toughened by blending with a novel biodegradable aliphatic–aromatic copolyester - random poly(butylene succinate-co-glutarate-co-adipate-co-terephthalate) (PBSGAT), with low crystallinity, synthesized from respective dimethyl esters of terephthalic acid, succinic acid, glutaric acid, adipic acid, and 1,4-butanediol. PLA blends with PBSGAT were prepared by melt blending and their structure as well as properties were studied. The copolyester formed particles in the blends and exhibited a separate glass transition. 20-fold increase of the ultimate strain and 2.5 fold increase of the tensile impact strength with respect to neat PLA was achieved in the blends with 25–35 wt.% of PBSGAT. TEM and SEM studies of drawn specimens evidenced that the main mechanism of the toughening was cavitation inside the copolyester particles, which promoted shear yielding and further plastic deformation of PLA matrix.

Polylactide (PLA), a main biodegradable and biobased candidate for the replacement of petrochemical polymers, is stiff and brittle at room conditions. It is therefore of high interest to formulate new PLA-based materials suitable for applications demanding flexibility and toughness. In this work, novel blends of PLA with polyhedral oligomeric silsesquioxanes (POSS) grafted with longer (P1) and shorter (P2) arms of ethylene glycol derivatives were prepared and studied. It was hypothesized that, owing to their architecture with the central POSS cage grafted with arms, miscibility and stability of the blends could be improved. Indeed, PLA/P1 blends were homogeneous despite P1 relatively high M w of 9,500 g mol−1. The blend with 20 wt% of P1, having T g at 16 °C, was transparent and flexible, elastomer-like material with excellent drawability. The blend remained homogeneous and retained its good drawability as well as flexibility during 6 months of aging at room temperature: a 2 % secant modulus of elasticity well below 100 MPa, a low yield stress below 2 MPa, and and a large strain at break of 8 (800 %). Contary to that, PLA/P2 blends were only partially miscible. Nevertheless, owing to the liquid state of the dispersed phase, the blend with 15 wt% of P2 was transparent and ductile, with T g at 49 °C, a relatively high yield strength of 29 MPa, and a large strain at break of 2.3 (230 %). The toughening mechanism involved the initiation of crazes and facilitation of their propagation by the liquid inclusions via the local plasticization effect.

New aliphatic–aromatic copolyester containing three different aliphatic comonomers: butylene adipate, butylene succinate and butylene glutarate, and one aromatic butylene terephthalate comonomer, all of petrochemical origin, has been synthesized (PBASGT) and its molecular characteristic, crystallization aptitude and morphology were examined by various techniques. Using the assignment of 1H NMR resonances due to homogeneous and heterogeneous dyads, the average block lengths were determined and it was found that PBASGT is a nearly random copolymer. During solidification only butylene terephthalate blocks are able to crystallize. However, some of the reflections from crystal planes are shifted towards lower diffraction angles as compared to butylene terephthalate homopolymer. Nonisothermal crystallization revealed the peak of crystallization at 37 °C while melting of those crystals occurred at 108 °C, in contrast to a homopolymer of butylene terephthalate (228 °C). PBASGT crystallizes in the form of thin fibrous crystals, few nanometers thick, which is the main factor influencing the depression of its melting temperature. Although the crystallinity degree is low (around 20%) the crystals form spherulitic aggregates filling the entire volume of the material. The chemical structure, morphology and crystallization behavior of PBASGT were compared with commercial aliphatic–aromatic copolyester of butylene terephthalate and butylene adipate (PBAT), Ecoflex. It appeared that, in contrast to aliphatic part of PBAT, aliphatic part of PBASGT is unable to crystallize, when annealed below room temperature. It appeared also that, similarly as PBAT, PBASGT is biodegradable.

The influence of poly(tetrafluoroethylene) (PTFE) nanofibers on the extensional viscosity of various molten thermoplastic polymers, including isotactic polypropylene (iPP), high density polyethylene (HDPE), low density polyethylene (LDPE), and atactic polystyrene (PS), has been investigated. It has been shown that PTFE nanofibers, generated in situ by shearing of crystalline PTFE inclusions during compounding with another molten polymer, formed an entangled network, which in turn drastically changed the rheological behavior of polymers studied. The entangled network of PTFE nanofibers induced the strain hardening effect in the nanocomposites based on iPPs, HDPE, and PS, which do not show the strain hardening themselves. Moreover, the strain hardening in the nanocomposite with LDPE was enhanced in comparison to neat LDPE. The higher the content of PTFE nanofibers and the larger the strain rates applied, the more pronounced the strain hardening occurred. Additionally, the presence of PTFE nanofibers significantly improved the melt strength of studied thermoplastic polymers.

International audience; The crystallization of isotactic polypropylene (PP) in γ-modification, which forms under high pressure but also at high temperature, can be nucleated by nucleating agents used for PP α-modification crystallizing under atmospheric pressure, like poly(tetrafluoroethylene) (PTFE) particles and commercial Hyperform HPN-20E. The study focuses on answering the question whether these nucleants are sufficiently active under high pressure to nucleate crystallization of PP during cooling in the temperature range of crystallization of the γ-form. To this aim, neat PP and PP with 0.2 wt% of nucleating agents were annealed at 250 °C for 5 min and subsequently cooled under a pressure ranging from 1.3 to 300 MPa. After releasing pressure, the specimens were analyzed by DSC, WAXD and PLM to have an insight into morphology, crystallinity and content of crystallographic forms. Both, Hyperform HPN-20E and PTFE, nucleated the crystallization of PP during cooling under high pressure in the γ-form causing an increase of crystallization temperature, the γ-form content and a decrease of grain size, although the first nucleant was more efficient. Calcium pimelate, a known nucleant of the β-form, studied for comparison, was ineffective.

Recently, agricultural by-products, for instance, corn husks, oat husks, or cocoa shells, have gained attention as a source of cellulose fibers and fillers because they can save the land and other natural resources required to grow fiber crops. It has to be noted, however, that textile processing, for example, shearing, is also a source of waste fibers. Our study focuses on utilization of waste cotton fibers, amassed during shearing of textiles, as a filler for polylactide (PLA). PLA composites with 10–30 wt% of waste cotton fibers were prepared and their thermal and mechanical properties were studied. The composite with 30 wt% of fibers exhibited markedly higher storage and loss moduli as compared with neat PLA; at 25°C the storage moduli increased by 53% whereas the loss modulus increased by 76%. In addition, the yield strength was slightly improved, by 11% at 25°C. Although the composites were thermally less stable than neat PLA, their 5% weight loss temperature remained high, about 300°C. POLYM. COMPOS., 35:747–751, 2014. © 2013 Society of Plastics Engineers

An idea to deform highly crystalline polymer particles with unentangled macromolecules into nanofibers by shearing via viscous media has been exploited in the paper. It has been shown that nanofibers can be generated during uniform shearing of solid polytetrafluoroethylene, PTFE, particles dispersed in a molten polymer. PTFE powder particles should be of high crystallinity with unentangled macromolecules and should consist crystals with melting temperature exceeding that of equilibrium melting temperature (332–336 °C). The larger the deformation ratios and shear rates, and the longer the shearing times the thinner and stronger PTFE nanofibers are obtained. Shearing during compounding results in generation of PTFE nanofibers and thus, forming all-polymer nanocomposite. Isotactic polypropylene, high density polyethylene, low density polyethylene and atactic polystyrene were used as polymer matrices for the generation of all-polymer nanocomposites during compounding with selected PTFE powders. The process is characterized by simplicity just by shearing the dispersed crystalline polymer inclusions in another molten polymer.

We hypothesized that polymer crystal anisotropy is advantageous for toughening of polymer composites involving easy slip network of oriented crystalline layers around filler particles. To this end, composites of syndiotactic polypropylene (sPP) with high concentration of submicrometer calcium carbonate particles were prepared and examined because usual sPP crystals exhibit high packing anisotropy. The specific orientation of sPP lamellae around chalk grains was found, which is supposed to facilitate the plastic deformation of polymer matrices. The compression molded bars of the composite exhibited markedly higher Izod impact strength than those of neat sPP. Toughening was even enhanced in the injection molded composite, for which 4.5-fold increase in the impact strength was achieved. Injection-induced orientation of the disordered form I sPP crystals was enhanced in the composite. The injection molded tensile specimens exhibited also a good drawability. Debonding at chalk–sPP interface occurred both during the impact and tensile tests facilitating the plastic deformation of sPP matrix. Chalk did not have any significant influence on the thermal properties of the composites but it affected the rheological behavior, increasing the loss and storage moduli, and the viscosity. Highly filled sPP composite exhibited solid-like behavior in a molten state with the storage modulus exceeding the loss modulus in the entire frequency range. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43651.

Polylactide reinforced with 3 wt% of organo-modified montmorillonite, 5 wt% of stearic acid-modified calcium carbonate nanoparticles, 15 wt% of cellulose fibers (PLA/MMT, PLA/NCC, PLA/CF) and hybrid composites containing 15 wt% of fibers in addition to montmorillonite (PLA/MMT/CF) or calcium carbonate (PLA/NCC/CF) were prepared and examined. The nanoparticles were dispersed in polylactide almost homogeneously; montmorillonite was exfoliated during processing. T g of polylactide remained unaffected but its cold crystallization was enhanced; the cold-crystallization behavior of the hybrid composites was dominated by nanofillers nucleating ability. The fibers and calcium carbonate decreased whereas exfoliated montmorillonite improved the thermal stability of the materials. Polylactide, PLA/NCC and PLA/MMT exhibited ability to plastic deformation, although the latter the weakest. Tensile behavior of the hybrid composites was strongly influenced by the fibers and similar to that of PLA/CF. All the fillers increased the storage modulus below T g ; that of PLA/MMT/CF and PLA/NCC/CF was improved with respect to polylactide by 50% and 45%, respectively.

International audience; Through applying both a probabilistic approach and a combination of probabilistic and the Avrami ‘extended volume’ approaches we have derived a theory of overall crystallization kinetics of polymers reinforced with nanofibers. The theory describes the crystallization kinetics in the presence of straight or curved nanofibers, with different nucleation ability and orientation, and allows to account for their variable length. The analytic results are supported by computer simulations of spherulitic structures. The derived mathematical formulas are in exponential forms suggesting the use of the Avrami logarithmic coordinates for detailed analysis of experimental data. Experimental data on crystallization of several nanocomposites, including polypropylene reinforced with poly(tetrafluoroethylene) nanofibers and polyamide 12 with carbon nanotubes, are in a good agreement with the theoretical predictions.

Dispersions of isotactic polypropylene (PP) particles in polystyrene (PS) were produced by interfacially driven breakup of nanolayers in multilayered systems that were fabricated by means of layer-multiplying coextrusion. The droplet size was controlled by the individual PP layer thickness ranging from 12 to 200 nm. In addition, PP was melt blended with PS to produce PP droplets larger than those formed by breakup of nanolayers. The dispersions of PP particles in the PS matrix were melted and annealed under high pressure of 200 MPa. Only the largest PP droplets, with average sizes of 170 μm, crystallized predominantly in the γ form. In the 42-μm droplets obtained by breakup of 200 nm layers, a minor content of the γ form was found whereas the smaller droplets obtained by breakup of the thinner nanolayers contained the α form and/or the mesophase. The results showed that the γ phase formed only in the droplets sufficiently large to contain the most active heterogeneities nucleating PP crystallization under atmospheric pressure. It is concluded that the presence of nucleating heterogeneities is necessary for crystallization of PP in the γ form under high pressure.

Nucleation of isotactic polypropylene (PP) crystallization by gold particles with various sizes and shapes was studied. The morphology of gold particles ranged from microcrystals with well-developed crystal facets (AuMC) to vacuum-sputtered 5 nm gold nanoparticles (AuNP), 30 nm gold nanoislands (AuNI), and compact gold nanolayer (AuNL). To minimize agglomeration of Au particles in molten PP, the nucleated crystallization was studied by means of the improved sandwich method, which consisted in the controlled deposition of a homogeneous nucleant layer between ∼ 100 μm PP films, followed by the careful thermal treatment and the evaluation of the nucleation activity by three independent methods: polarized-light microscopy, two-dimensional wide-angle X-ray scattering, and differential scanning calorimetry. It was demonstrated that the nucleating activity of gold strongly depended on its morphology: The nucleation effect of microcrystalline AuMC resulted in a transcrystallization comparable to that caused by a strong commercial α-nucleant (Hyperform HPN-68), whereas the effect of vacuum-sputtered layers of nanocrystalline AuNL, AuNI, and AuNP was extremely weak. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

In this study, plasticization of polylactide (PLA) with PEG–PPG–PEG triblock copolymers was examined. Two different copolymers were utilized, with molecular weight of 1100 and 1900 g mol−1, and with PEG contents of 10 and 50 wt %, respectively. A PPG plasticizer with molecular weight of 1000 g mol−1, close to that of PPG block in the copolymers, was also used for comparison. Melt blends containing 10 and 15 wt % of the plasticizers were prepared. Thermal properties, mechanical properties, and structure of quenched and annealed films of the blends were studied. The crystallization driven phase separation occurred in all the annealed blends but led to different structures depending on the plasticizer used. Distinct inclusions of the plasticizer were visible under the scanning electron microscope only in PLA with PPG but not in the blends of PLA with the copolymers. The drawability of the plasticized systems was improved when compared with neat PLA. In the quenched and annealed blends, elongations at break at the level of 5 and 0.7, respectively, were reached. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

A novel composite material containing 2 wt% of cellulose nanofibers well dispersed in PLA matrix, both materials being biodegradable, was prepared and studied. Biodegradable composites with 2 and 20 wt% of cellulose fibers with standard diameters were also obtained and examined for comparison. The nanocomposite exhibited markedly higher storage modulus as compared to neat PLA and the composite with the same content of cellulose standard fibers. In addition, yield strength of the nanocomposite was improved in comparison with neat PLA, especially at elevated temperature of 45 °C, at which it was higher by 50%. No negative effect of standard fibers and nanofibers on molar mass of PLA matrix was observed. Moreover, the composite materials, including the nanocomposite, did not show weight loss up to 300 °C.

International audience

Nucleation of crystallization of isotactic polypropylene (iPP) and polyoxymethylene (POM) with dispersed submicron particles of another polymer – poly(tetrafluoroethylene) (PTFE) was studied. The polymers were mixed with various contents of PTFE particles, in the range from 0.005 to 0.5 wt.%. iPP and POM with PTFE particles are all-polymer systems with enhanced nucleation of crystallization. PTFE particles with sizes below 300 nm added to POM and iPP efficiently decreased sizes of polycrystalline aggregates. Moreover, nonisothermal crystallization temperature of iPP by increased by up to 14 °C. iPP and POM with PTFE exhibited the elastic modulus slightly higher, by up to 10–13%, than that of the neat polymers. Other mechanical properties remained unchanged, with the exception of reduced elongation at break of POM with PTFE.

Although gold particles are known to nucleate isotactic polypropylene (PP), the nucleating effect of chemically pure 5 nm Au, prepared in vacuum sputter coater, was found to be hardly observable. In order to detect such a weak effect, we deposited a homogeneous layer of Au nanoparticles between thin PP films and evaluated the nucleation activity by a combination of three independent methods: polarized light microscopy (PLM), differential scanning calorimetry (DSC), and 2D wide-angle X-ray scattering (2D-WAXS). This new technique, which was called sandwich method, allowed us to demonstrate that gold nanoparticles were able to nucleate PP crystallization, although the effect was much weaker than that produced by commercial α-nucleant [1,2,3,4-bis(3,4-dimethylbenzylidene)sorbitol] and β-nucleant (N,N-Dicyclohexyl-2,6-naphthalene dicarboxamide). The sandwich method appeared to be quite universal and applicable for any micro-sized nucleants or nanonucleants.

Nucleation of isotactic polypropylene (iPP) crystallization by gold (Au) nanoparticles was studied. Regardless of their size, 4.3, 8.8, 28.3, and 84.5 nm, all particles were able to nucleate spherulites when deposited on the iPP surface. However, when added and melt-mixed with iPP, only the smallest particles affected significantly the iPP bulk crystallization. Au nanoparticles larger than 4.3 nm, at the concentration of 0.001 wt %, did not influence the crystallization of iPP. Contrary to this, 0.001 and 0.005 wt % of Au nanoparticles having the size of 4.3 nm increased crystallization temperature of the iPP by 7-8 °C and decreased markedly the sizes of polycrystalline aggregates. Aggregation of Au nanoparticles in the polymer matrix was evidenced by electron microscopy and contributed to their decreased effectiveness in the nucleation of iPP crystallization.