Melting point elevation in compatible polymer blends

Summary An expression is presented which relates the experimentally observed melting point depression in crystallizable, compatible polymer blends to changes in lamellar thickness and thermodynamic considerations.Considering a given crystallization temperature, this relationship suggests that one should observe a depressed blend melting point, despite an increase in lamellar thickness over the pure crystallizable material.Possible explanations for the melting point elevation observed in some compatible blends are discussed.     

Process behavior of compatible polymer blends

It is a common industrial practice to blend virgin polymer with the same polymer recycled from scrap plastic that, in general, has not undergone relevant degradation. In this article, the influence that incorporating recycled material has on injection processes, especially on the rheological behavior of the material was studied. With this aim in mind, a mixture of two materials with the same nature or composition and similar viscosity was used, which is the system that is most commonly seen in industry. The mixture studied is composed of virgin PP (polypropylene) typically found in injection processes, and recycled copolymer PP from scrap plastic. A complete characterization of the materials and applied existing models was carried out to predict the mechanical behavior of the mixtures. A model to predict the behavior of the mixtures during processing, based on the rheological characteristics of the materials used was developed. This predictive model has been experimentally validated using filling tests in injection molding machines, as well as by specific simulation software. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Solvent-induced crystallization of a compatible polymer blend

We studied solvent-induced crystallization (SINC) in a compatible blend of poly (butylene terephthalate) (PBT) and a polyarylate (PAr) over a range of blend compositions and temperatures; liquid acetone was the crystallizing agent. Acetone transport kinetics were followed by mass uptake measurements in thin films and by optical microscopy. Crystallization kinetics were followed by density measurements. For the 0.2 mm thick films used, those with higher weight fractions of PST (50 to 60 percent by weight) exhibit diffusion controlled transport and crystallization over the entire range of temperatures studied (0 to 55°C). Those with lower weight fractions of PBT (～30 percent by weight) display Case II sorption and crystal growth controlled crystallization at 0°C. The latter is rare for SINC in homopolymers and results from a sharp reduction in the PBT crystallization rate in the presence of the noncrystallizable PAr.     

Mechanical and morphological behavior in polystyrene based compatible polymer blends

Mechanical and morphological behavior of polystyrene (PS) based compatible polymer blend systems were studied using a tensile tester and scanning electron and optical microscopes. Four different binary compatible blend systems were employed and characterized: PS and poly (2,6-dimethyl 1,4-phenylene oxide) (PPO), PS and poly(vinylmethylether)(PVME), PS and poly(α-methyl styrene)(PαMS), and PPO and PαMS. The compositional dependence of the mechanical properties showed a synergistic effect with respect to modulus, but a negative deviation from the rule of mixtures relationship for strain at break. From the scanning electron microscope (SEM) observations, a deformation mode transition from crazing to crazing and shear banding occurs at ˜25 wt% PPO in the PS/PPO blends, as indicated by the patch and river patterns above this composition. In the PS/PVME blends, a similar transition was observed at >10 wt% PVME. The PS/PαMS blends showed brittle fracture regardless of composition. The PPO/PαMS blends showed a brittle fracture for a PαMS content >25 wt%. Optical microscope (OM) observations showed that blending of PS/PPO and PS/PVME resulted in a decrease of craze density and length as the PPO and PVME content was increased. PS/PαMS and PPO/PαMS blends showed few crazes, all of which were localized near the fracture surface. The mechanical and morphological behavior can be explained using models of intermolecular interactions and entanglement density in compatible blends, respectively. Overall the mechanical property and the consequent morphological behavior were similar to the effect of antiplasticization.     

Coalescence in three-component polymer systems

The change in the ratio on incorporation of a third (noncoalescing) disperse component between the number of coalescence and dispersion events alters the polydispersion and increases the degree of dispersion of the second (basic) component in a fibre-forming polymer blend melt. Incorporation of a third highly disperse component is a method of changing the degree of dispersion in fibre-forming melts of polymer blends. __________ Translated from Khimicheskie Volokna, No. 5, pp. 24–26, September–October, 2006.     

Hydrogen bonding in polymer systems

The importance of hydrogen bonding interactions in promoting polymer miscibility has been the subject of much recent investigation. In this study, we address the question of the effect of molecular size and geometry on the intensity of the hydrogen bonding interaction. To this end, the interaction of the functional group in various molecules with a variety of acid and base polymer matrices has been monitored using infrared spectroscopy. The “probes” used in this study each contained only one functional group per molecule to prevent intra-molecular association. The probes were acetone, di-n-hexyl ketone, 10-nonadecanone, cyclohexanone, cyclododecanone, isopropanol, 4-decanol, 10-nonadecanol, cyclohexanol, and cyclododecanol. The interactions of the base probes with poly-(vinyl chloride), poly(vinylidine fluoride), phenoxy, poly(styrene-co-allyl alcohol), and a variety of cellulosic polymers were studied. Acid probe interactions were measured in poly(pivalolactone), poly(butanediol-1,4-terephthalate), poly-(acetal), poly(?-caprolactone), poly(vinyl methyl ether), poly(4-methoxy styrene) and poly(ethylene oxide). The effect of the presumably inert poly(styrene) and ethylene-propylene rubber matrices on the probe's functional group was studied for comparison.     

An introduction to blood compatible polymer surfaces for use in artificial internal organs

While the body is a hostile environment for all types of polymers, an even more serious problem is that of thrombus formation induced by all foreign surfaces, including polymeric surfaces. This is a still largely unsolved problem which hinders the development of artificial internal organs. The thromboresistant materials presently proposed and used in artificial organs include heparinized surfaces and materials found to be thromboresistant in certain implantation cites. In this article tissue-polymer interactions are first discussed and then followed by a discussion of blood-polymer interactions. The mechanism of thrombus formation is presented and some of the possible interactions of blood with surfaces are suggested. Representative nonthrombogenic and thromboresistant materials are discussed.     

Thermodynamics of polymer systems

Summary Gas chromatography has been employed to determine partial molar free energies of sorption, C₁ ^s, as well as partial molar free energies of mixing, C₁ , of atactic poly(styrene) with linear and branched alkanes (C₆-C₉), alkenes (C₈), cyclohexane and alkylbenzenes (Ph-H to PhC₆H₁₃) within the temperature range from 403 to 463 K. The influence of nature and constitution of the solute molecule on sorption and mixing properties in poly(styrene) are discussed in terms of the competing group contributions of the components. Knowledge of this influence may be transduced to understand polymer-polymer compatibility. The cohesive energy density concept has been used to calculate the infinite dilution solubility parameter for the polymer, with the aid of G ₁ . From the high temperature range the HILDEBRAND parameter ₂ was extrapolated to 298 K. The value obtained, 9.14, indicates that gas chromatography is an promising alternative to the conventional methods for determination of the solubility parameter for polymers.Herrn Prof. Dr. R. C. Schulz zu seinem 65. Geburtstag herzlichst gewidmet     

On mixing in polymer flow systems

The mixing of polymers is an important subject which has received considerable and recent attention. This study shows that residence time distribution curves give information on the distribution of material along the primary flow direction, but do not quantify in polymer flow systems. Several polymer processing systems have been analyzed and the degree of mixing has been related to strain in each of these systems. Strain correlates directly with transverse mixing, which is the most important aspect of polymer mixing. Mixer design is shown to influence the amount of strain needed to achieve a specified degree of mixedness.     

Curing behaviour of compatible interpenetrating polymer networks based on epoxy and methacrylated epoxy

Compatible interpenetrating polymer networks (IPNs) based on diglycidyl ether of bisphenol A (DGEBA) and methacrylated diglycidyl ether of bisphenol A (MADGEBA) in weight ratios of 100/0, 75/25, 50/50, 25/75 and 0/100 were blended and cured simultaneously by using dicumyl peroxide (DICUP) and hexahydrophthalic anhydride (HHPA) as curing agents. Fourier transform infrared spectroscopy (FTIR) was employed to investigate the intermolecular interactions and functional group changes. Viscosity increases during crosslinking were examined with a Brookfield viscometer. Curing exothermic peaks were studied with differential scanning calorimetry (DSC). The gel fractions of various IPN compositions were measured with a Soxhlet extractor. Samples thus prepared were checked for their compatibility by measuring glass transitions with DSC and damping peaks with rheometric dynamic spectroscopy (RDS). Experimental results revealed that good compatibility between components induced a network interlock, which subsequently resulted in incomplete cure of the IPN materials. ©1997 SCI     

Interactions in aqueous polypeptide derivative/surfactant systems

Summary A new class of compounds of water-soluble polypeptide derivatives have been synthesized and the interactions with the anionic surfactan sodium dodecylsufate (SDS) studied by rheological and light scattering investigations. The viscosity of the aqueos polypeptide solution passes through a distinct maximum with increasing surfactant concentration. This behaviour, so far only known for hydrophobically modified cellulose derivatives, can be explained by a formation and decay of polymer surfactan networks. The changes caused by microscopic structural parameters through surfactant adsorption are observed by dynamic light scattering and can be correlated with the macroscopic behaviour of the solutions.     

Interactions between volatiles and lipids in complex systems

Partition equilibria of three aroma compounds in three different biphasic systems were studied by a liquid/liquid partition technique to investigate interactions that occur between volatiles and lipids in biphasic solutions. The lipids used were linoleic acid and ricinoleic acid and tetradecane as a model. The three aroma compounds were ethyl acetate, 2,5-dimethylpyrazine, and oct-1-en-3-ol. The results showed that the intermolecular forces involved were weak. Infrared spectroscopy was then performed on binary systems (tetradecane and linoleic acid or aroma compound) and on ternary systems (tetradecane, linoleic acid, and aroma compound) to determine the nature of the interactions. This method confirmed the presence of hydrogen bonds between linoleic acid and 2,5-dimethylpyrazine or oct-1-en-3-ol and also between molecules of oct-1-en-3-ol when the latter are present at high concentrations in lipids. The observations provided sufficient information to explain the behavior of oct-1-en-3-ol in biphasic solutions, but further work is needed to fully elucidate the nature of interactions between ethyl acetate or 2,5-dimethylpyrazine and lipids and also to explain the behavior of these compounds in biphasic solutions.     

Non-linear PEG-based thermoresponsive polymer systems

Poly(ethylene glycol) (PEG) is one of the most used polymers in medical and biological applications. Its non-toxicity, non-immunogenicity, biocompatibility and solubility in a wide range of solvents offer various possibilities of utilization and explain the amount of studies dealing with this polymer. More recently, non-linear PEG-based monomers attracted much interest due to their thermal behavior. The present review aims at presenting many PEG-based thermoresponsive systems from structural and synthesis point of view and at highlighting all their fascinating properties from their behavior in solution, the fine-tuning of the transition temperature until the formation of smart materials.     

Bubble nucleation in nonpressurized polymer foaming systems

The mechanism of bubble nucleation in the foaming process under atmospheric pressure is investigated in the present study. The experimental observations using a plastic‐foaming visualization setup revealed two stages of nucleation, primary nucleation in interstitial regions and secondary nucleation in the polymer melt, which followed the sintering and densification of the polymer matrix. Statistical analysis of the evolving cellular structure during the nucleation stage was used to study the significance of rheology on the behavior of polymer materials during the nucleation. The role of viscosity on the nucleation rate was also investigated theoretically by using a modified form of the classical nucleation theory and it was verified with the experimentally observed data. POLYM. ENG. SCI., 54:1201–1210, 2014. © 2013 Society of Plastics Engineers     

改性松香印刷水墨用乳液的研制

概述一种与松香印刷水墨混合效果理想的苯丙高分子乳液的制备、特性 ,以及乳液与松香墨混合提高墨的干燥速度、耐摩擦、耐水等性能。     

Interactions between flame retardants and stabilizers in polyethylene systems

The influence of flame retardants and stabilizers on the thermooxidative and thermal stability of polyethylene systems has been investigated. In the present study 18 polymeric composites were prepared and their stabilities investigated by static and dynamic methods; their flammability parameters were also determined.     

Interactions between basecoats and clearcoats in car refinish systems

The introduction of VOC compliant waterborne basecoats and solventborne basecoats on one hand and the introduction of VOC compliant clearcoats on the other hand forces to look to the interactions between the two systems. As well known from studies in the automotive OEM area small molecules like HALS and UV-absorbers additives diffuse from the clearcoat into the basecoat. This influences the durability performance of the system.The main question addressed in this paper is the interaction of the binder system of the basecoat and clearcoat. In general crosslinkers (e.g. poly-urethane coatings) are rather low molecular weight materials which may diffuse between layers as well. Also the lower molecular weight functional resins of the binder may move throughout the system.The interactions of basecoat/clearcoat combinations were investigated by means of chemical and physical techniques. The effect of a medium solid clearcoat, a VOC compliant p-urethane clearcoat and UV-clearcoat on interpenetration, physical and paint properties were studied.Also some attention is paid to the diffusion of HALS and UV-absorbers from the clearcoat into the basecoat.