Effect of glycols on the properties of polyester polyols and of room‐temperature‐curable casting polyurethanes

A series of liquid polyester polyols (PEs) from adipic acid (AA), phthalic anhydride (PA) and trihydroxymethylpropane (TMP), and such glycols as ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol (TEG), butanediol (BD) and hexanediol (HD), were prepared. Polyurethanes (PUs) were obtained from the PEs and polyaryl polymethylene isocyanate (PAPI) at room temperature. The effects of the structures of the glycols on viscosity, glass transition temperature and crystallinity of the PEs, and the mechanical, thermal and boiling‐water‐resistant properties of PUs were studied. The experiments showed that the viscosities and glass transition temperatures of the PEs decreased as the length of the glycol chains increased. The polyester based on HD lost flowability because of crystallization. The tensile strength and hardness of the PUs obtained decreased with increasing the length of the glycol chains, while the resistance to thermal deformation and boiling water increased. Thermogravimetric analysis demonstrated that thermal degradation of the polyurethane based on DEG proceeded in one step and for the others in two steps. The initial degradation temperature of the polyurethane based on EG was the lowest and that of the polyurethane based on BD was the highest. The residue of the former at 450 °C was the greatest, while that of the latter was the lowest. Copyright © 2004 Society of Chemical Industry     

Polyester hot-melt adhesives. I. Factors affecting adhesion to epoxy resin coatings

The peel strength and tensile shear strength of polyester hot-melt adhesives on metals coated with epoxy resins are affected by four characteristics of the polyester: (1) inherent viscosity, (2) glass transition temperature (T_g), (3) degree of crystallinity, and (4) melting point. The inherent viscosity affects the strength, toughness, and crystallinity of the adhesive. The T_g and degree of crystallinity affect the low-temperature adhesive properties; the peel strength is relatively low when the T_g is appreciably above the use temperature. The T_g, degree of crystallinity, and melting point affect the high-temperature adhesive properties. A hot-melt adhesive with high peel and tensile shear strengths from 0° to 120°C is the polyester of 1,4-butanediol and trans-1,4-cyclohexanedicarboxylic acid.     

Melt Synthesis and Characterization of Aliphatic Low-Tg Polyesters as Pressure Sensitive Adhesives

Polyesters, which are readily synthesized in the absence of solvent, are excellent candidates for a new generation of pressure sensitive adhesives (PSAs) due to their low cost and potential biodegradability. In this study, linear, all-aliphatic polyesters with low glass transition temperatures (T_g) were synthesized using a solvent-free, environmentally friendly melt polycondensation methodology. Polyesters of various compositions were synthesized from different diol and diester monomers to adjust the glass transition temperature and achieve optimum adhesive properties. Melt polycondensation of an isomeric mixture of dimethyl-1,4-cyclohexane dicarboxylate (DMCD), dimethyl adipate (DMAP), diethylene glycol (DEG), and triethylene glycol (TEG) generated a series of linear low-T_g polyesters. The synthesized polyesters were characterized using size exclusion chromatography (SEC), differential scanning calorimetry (DSC), and ¹H NMR spectroscopy. The frequency- and temperature-dependent properties of the low-T_g polyesters were characterized using dynamic mechanical analysis (DMA). The adhesive performance of the polymers was evaluated using tack, peel, and shear strength measurements at ambient humidity and temperature. The low-T_g polyesters exhibited peel and tack properties comparable with commercial acrylic adhesives.     

Preparation and biodegradation of hydroxyl terminated poly(fumaric acid‐co‐diethylene glycol) and its segmented polyurethane

Hydroxyl terminated poly(fumaric acid‐co‐diethylene glycol), poly(FA‐co‐DEG) was prepared by melt polycondensation. The resultant unsaturated aliphatic polyester was characterized by Fourier transform infrared (FTIR) spectroscopy, hydroxyl value, acid value, and intrinsic viscosity. Its enzymatic degradation and crosslinking behavior as well as the effect of crosslinking degree on enzymatic degradation were also investigated. The crosslinking degree and reduction of carbon–carbon double bonds revealed excellent self‐crosslinking nature of poly(FA‐co‐DEG) at high temperature. The results of enzymatic degradation showed that poly(FA‐co‐DEG) has excellent biodegradability and that the biodegradation can be controlled by the crosslinking degree. Polyurethane was prepared by the reaction of poly(FA‐co‐DEG), 2,4‐toluene diisocyanate (TDI), and 1,4‐butanediol (BD). It was found that the biodegradation of the obtained polyurethane was slower than that of the original unsaturated aliphatic polyester poly(FA‐co‐DEG). The peeling strength of the polyurethane was very high, supporting better adhesion property with enhanced crosslinking. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Low glass transition temperature aliphatic polyurethanes

Summary The present paper deals with the single step syntheses of a few aliphatic polyurethanes using some simple glycols like ethylene, propylene, 1,3- and 1,4-butylene glycols and two different bis(chloromethyl) compounds viz., 1,4-bis(chloromethyl)-2,5-dimethyl benzene (I), and 1,5-bis(chloromethyl)-2,4-dimethyl benzene (II). The glass transition temperatures, T_g, of these polymers were determined using dilatometric techniques and they ranged from –12 to –48°C. The polyurethanes derived from 1,4-butylene and ethylene glycols were amorphous gums with T_g well below –30°C.     

Studies on glass transition temperature during staling of bread containing different monomeric and polymeric additives

Glass transition temperature (T_g) of bread containing different antistaling agents and also of bread superquenched and annealed in a DSC cell and outside, was determined using differential scanning calorimeter (DSC). Increase in T_g during the staling of bread correlated with firming as measured by Instron. Singlet T_g was an indication of miscibility or compatibility of bread components with each other. The lowest increase in T_g was found in bread containing propylene glycol (singlet) followed by glycerol (doublet), maltodextrin (broad), gelatin (singlet), antistaling enzyme (singlet), and polypropylene glycol (doublet) in the order of increase in T_g. Superquenching produced a maximum increase in T_g of bread. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1147–1152, 1999     

Engineering plastics from lignin. VI. Structure–property relationships of PEG-containing polyurethane networks

Hydroxypropyl lignin-based thermosetting polyurethanes were synthesized with excess hexamethylene diisocyanate (HDI) and tolylene diisocyanate (TDI) by solution casting. Four polyethylene glycols (PEG) of molecular weight 400, 600, 1000, and 4000 were mixed with lignin polyol to incorporate different proportions of soft segment into the network prior to crosslinking. Neither thermal nor mechanical and limited small angle x-ray scattering (SAXS) analysis provided distinct evidence for phase separation and microstructure formation. The study examines the effect of the soft segment in relation to chain length and weight contribution on the thermal and mechanical properties of the final networks. A significant sensitivity of glass transition temperature (T_g), of swelling in DMF, and of the mechanical properties to soft segment content was observed. Some of this sensitivity must, however, be attributed to differences in crosslink density since the polyol to diisocyanate weight ratio was kept constant throughout the synthesis series. The magnitude of the change of the different properties was found to be influenced by both glycol content and glycol molecular weight. The T_g of the network decreased from 105°C to as low as 38°C (HDI), and from 158°C to 70°C (TDI), with incorporation of up to 17.8% glycol, and it was greater with lower molecular weight glycols than with higher ones at any weight fraction. Swelling in DMF increased as expected with soft segment content. Mechanical properties were affected most if HDI and lower molecular weight glycols were used. The uniformity in structure, reduction in brittleness, and considerable improvement in mechanical properties with inclusion of minor PEG contents indicates that lignin-based network polyurethanes can be synthesized with controllable performance characteristics.     

Effect of polyester polyol chain length on the properties of transparent poly (ester-urethane-acrylate)/MMA copolymer for optical applications

A series of poly(ester-urethane acrylate)/methyl methacrylate (PEUMA) crosslinked copolymers were prepared using hydroxyl terminated aromatic polyesters (PEs) with varying chain lengths. Four kinds of PEs with terminal hydroxyl groups were synthesized by reacting phthalic anhydride (PA) with 1,2- propanediol (PDO), 1,4-butanediol (BDO), 1,6-hexanediol (HDO) and diethylene glycol (DEG) respectively. The resultant PEs were reacted with isophorone diisocyanate (IPDI) in the presence of dibutyltin dilaurate (DBTDL) catalyst and end capped with 2-hydroxyethyl methacrylate (HEMA) to obtain ester-urethane-acrylate (EUA) prepolymer. Thereafter, crosslinked PEUMA copolymer were synthesized by reacting the EUA prepolymer with 40% (w/w) methyl methacrylate (MMA) in the presence of 1% azobisisobutyronitrile (AIBN) chain initiator. The PEs and EUA prepolymer were characterized by Fourier transform infrared (FT-IR) spectroscopy, ¹H NMR, and gel permeation chromatography (GPC) techniques. The average molecular weights (Mc) between two crosslinks of the samples were determined by using the Flory Rehner equation. The tensile modulus, flexural strength, thermal properties and transparency of PEUMA copolymers were also determined and correlated with the average molecular weight and crosslinked density. The transparency of PEUMAs was found to be above 90% and hence it is an excellent alternative to glass for optical applications.     

Synthesis and properties of polyamide derived from piperazine and lower purity dimer acid as hot melt adhesive

Polyamide hot melt adhesive was synthesized from lower purity dimer acid (composition: ∼23% trimer acid, ∼75% dimer acid and ∼3% monomer acid), sebacic acid, ethylenediamine and piperazine. The effect of piperazine and dimer acid concentration on properties of polyamides such as thermal properties: fusion temperature (T_f), heat of fusion (H_f), crystallization temperature (T_c), heat of crystallization (H_c), softening point (T_s) and glass transition temperature (T_g), mechanical properties: tensile strength and hardness, adhesion properties like lap shear strength (LSS) and T-peel strength (TPS), and rheological properties were investigated. Concentration of piperazine was varied from 12.5 to 37.5 mol% while that of dimer from 37.5 to 42 mol%. Piperazine has one hydrogen atom on each of its two nitrogen atoms in the ring structure. When it undergoes reaction with acids to form polyamide, these hydrogen atoms get consumed, making the amide linkage unable to form hydrogen bonding with the neighboring polyamide polymer chains. This leads to decrease in crystallinity of the polyamide. Thus, as the mole percentage of piperazine in the polyamide increases, it becomes more amorphous, decreasing T_f, H_f, T_c, H_c, T_s, T_g, tensile strength, hardness, LSS, TPS and viscosity. Dimer acid and trimer acid are bulky compounds. As their percentages in the polyamide increase, it becomes difficult for the neighboring polyamide chains to come closer. Thus, inter-molecular hydrogen bonding decreases. This leads to decrease in crystallinity of the polyamide, lowering T_f, H_f, T_c, H_c, T_s, T_g, tensile strength, hardness, LSS, TPS and viscosity.     

Room temperature-responsive poly(vinyl hydroxyalkyl ether-alt-dialkyl maleate)-based vitrimers with dynamic boronic ester bonds

Dynamic B O bonds are often applied to fabricate reversible-cross-linking and reprocessable polymer networks due to their high thermodynamic stability and kinetic tunability. However, it is still difficult to tailor boronic ester polymers, which have both excellent mechanical and self-healing properties in the absence of external stimuli. To address the above challenge, a range of room-temperature self-healable vitrimers are prepared by the reactions of various poly(vinyl hydroxyalkyl ether-alt-dialkyl maleate) copolymers and 1,4-phenyldiboronic acid. The dynamic cross-linking networks offer the as-prepared vitrimers superior mechanical properties and thermostability. Because of the presence of dynamic boronic ester bonds, the networks also demonstrated self-healing (the tensile strength recovered to 83% after 3 days at room temperature) and reprocessing capabilities (no significant change in tensile strength after thrice process recycles). Moreover, the vitrimers have potential as promising damping materials with wide temperature windows around room temperature. For example, the vitrimer of poly(ethylene glycol monovinyl ether-alt-dibutyl maleate) and 1,4-phenyldiboronic acid demonstrates its tanδ_max 1.18, T_g = 6.2°C and effective damping temperature range is from −16.4 to 48.5°C.     

Nylon 6/66/11 Copolymer Used for Hot-Melt Adhesives: Synthesis and Properties

A new copolyamide, nylon 6/66/11, used for hot-melt adhesives, was prepared by hydrolytic polymerization and melt polycondensation. Intrinsic viscosity, melting point, glass transition temperature, cold crystallization, thermogravimetry (TG) and adhesion strength of the resultant hot-melt adhesives were investigated. DSC thermograms of the copolyamide showed that both the melting point and glass transition (T _g) temperatures decreased as the molar fraction of aminoundecanoic acid increased. The T _g practically did not change as the mole fraction of aminoundecanoic acid increased from 60% to 80%, but cold crystallinity of the copolyamide decreased. The thermal gravimetric analysis indicated that the resultant copolyamide had a high thermal stability. The copolyamide had the best combination of properties when the molar fraction of aminoundecanoic acid was about 65%.     

Effect of diethylene glycol content and annealing temperature on the structure and properties of poly(ethylene terephthalate)

The effect of 2,2′-oxydiethanol (diethylene glycol, DEG) content (ranging from 2 to 15 mol %) and of the annealing temperature (in the range from 100 to 260°C) on the density, calorimetric, dynamic- and static-mechanical and small angle X-ray scattering (SAXS) behavior of undrawn and drawn samples (granules, films, and bristles) of poly(ethylene terephthalate) (PET) has been studied. The known dependences on the annealing temperature are confirmed. Some discrepancies with earlier investigations of the dependences on the DEG content are established: constant values for the SAXS intensity and long spacing, for the lamellar thickness and for the volume fraction crystallinity a_c. These discrepancies are explained by the variation of the glass transition temperature (T_g) and melting temperature (T_m) of the materials with different DEG contents. The previous hypothesis of the segregation of the comonomer (DEG) units into the amorphous regions is confirmed.     

Polyurethane/amino‐grafted multiwalled carbon nanotube nanocomposites: Microstructure,thermal, mechanical,and rheological properties

A mixture of two different polyols, (polytetramethylene ether glycol and polydimethylsiloxane), were employed to synthesize a new structure of polyurethane (PU) with methylene diphenyl diisocyanate (MDI) and 1,4‐butanediol as chain extender. PU nanocomposites containing variable amount (0.3, 0.5, 1, and 3 wt %) of amino‐grafted multiwalled carbon nanotubes (NH₂‐MWNT) were prepared via in situ polymerization. The dispersion of NH₂‐MWNT into polymer matrix was investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Fourier transform infrared spectroscopy (FT‐IR) confirmed the urethane‐urea chemical bonding between the PU chains and the NH₂‐MWNT. Thermal stabilities of the nanocomposites were examined with thermogravimetric analysis (TGA) and the results indicated a remarkable improvement with increasing NH₂‐MWNT contents. The results of dynamic mechanical thermal analysis (DMTA) including storage modulus (E′) and glass transition temperature (T_g), as well as tensile properties demonstrated that the yield strength, strain‐at‐break, and young modulus were enhanced by increasing NH₂‐MWNT content. Rheological behavior including complex viscosity and storage and loss moduli of the PU nanocomposites improved with increasing NH₂‐MWNT loading, as well. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44411.     

The effect of castor oil on the structure and properties of polyurethane elastomers

Segmented polyurethane elastomers based on a mixture of castor oil and poly(propylene glycol), 4,4'-diphenylmethane diisocyanate, and 1,4-butanediol were prepared. The ultimate, thermal, dynamic mechanical behavior and morphology were studied. The use of castor oil shifts the main transition region of the soft phase to higher temperatures (the glass transition temperature T_g increases) improves abrasion resistance and the tensile strength. The multifunctionality of castor oil leads to the crosslinking of the soft segments and a decrease of the sol and swelling of elastomers.     

Effects of TDI and FA‐703 on physico‐mechanical properties of polyurethane dispersion

A series of water dispersion polyurethanes dispersions (PUDs) were prepared by polyaddition reaction using isophorone diisocyanate (IPDI), toluene diisocyanate (TDI), poly(oxytetramethylene) glycol (PTMG), dimethylol propionic acid (DMPA), and triol (trade name FA‐703). Various formulations were designed to investigate the effects of process variables such as TDI and FA‐703 on the physico‐mechanical properties of PUD. IR spectroscopy was used to check the end of polymerization reaction and characterization of polymer. Evolution of the particle size distribution, contact angle, T_g, molecular weight, viscosity, and mechanical properties of the emulsion‐cast films were significantly affected by variable content of TDI and FA‐703. Average particle size of the prepared polyurethane emulsions and contact angle decrease with increase of content of FA‐703 and TDI. Molecular weight, T_g, tensile strength, tear strength, hardness, viscosity and elongation at break increase with increase of content of FA‐703 and TDI. The increase of molecular weight, tensile strength, tear strength and elongation at break properties are interpreted in terms of increasing hard segments, chain flexibility, and phase separation in high content of FA‐703 and TDI‐based polyurethane. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of nanodiamonds and multi-walled carbon nanotubes in thermoset hybrid fillers system: Rheology,dynamic mechanical analysis,and thermal stability

Recently, the interfacial bonding between nanodiamonds (DNDs) and multi-walled carbon nanotubes (MWCNTs) in epoxy-based nanocomposites were found. In this work, effects of amino functionalization on MWCNTs and DNDs introduction on rheology, dynamic mechanical properties, and thermal stability of MWCNTs epoxy-based nanocomposites are discussed. The results show that pristine MWCNTs increase the complex viscosity, lower the molecular weight of epoxy net chains as well as glass transition temperature (T_g), and expand the phase separation. Amino functionalization of MWCNTs make the behaviors above disappeared nearly. Besides, introduction DNDs improved T_g and restricted the phase separation as well, but the high complex viscosity and non-Newtonian behavior remains. This work may provide inspirations for the further researches about hybrid fillers.     

Chemical,thermal, and mechanical properties and ultraviolet transmittance of novel nano-hydroxyapatite/polyethylene terephthalate milk bottles

Polyethylene terephthalate (PET)/nano-hydroxyapatite (nHAp) composite granules were obtained using twin-screw extruder. Preforms were prepared by injection molding and then PET/nHAp bottles were produced by blow molding. For PET bottles with nHAp, the migration amounts of carboxylic acid (COOH), acetaldehyde (AA), diethylene glycol (DEG), and isophthalic acid (IPA); glass transition temperature (T_g); melting temperature (T_m); and the maximum crystallization temperature (T_cry) were measured. The load-carrying capacity, burst strength, stress cracking, and regional material distribution tests were carried out on the bottles. X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, and ultraviolet transmittance analyses were conducted to explain the changes in mechanical, chemical, physical properties, and light transmission of bottles. It was found out that the COOH amount increased and the AA content decreased with increasing nHAp amount. On the other hand, no change was observed in the amounts of DEG and IPA. Although the mechanical properties such as load-carrying capacity and burst strength of the bottles have improved, it has been determined that the standard environmental stress crack resistance test procedure cannot be applied to such a composite. Experimental findings indicate that nHAp disrupts the chemical structure of PET and it isolates harmful chemicals such as AA by forming intermolecular bonds. Moreover, with the addition of up to 0.8% nHAp, PET bottles block the light transmission approximately 80% within 400–700 nm wave length zone. The study demonstrates that the PET/nHAp composite bottles can be used in the food industry, particularly in the packaging of milk and milk products which are vulnerable to light exposure.     

Biodegradability of poly(ethylene terephthalate) copolymers with poly(ethylene glycol)s and poly(tetramethylene glycol)

Poly(ethylene terephthalate) copolymers were prepared by melt polycondensation of dimethyl terephthalate and excess ethylene glycol with 10–40mol% (in feed) of poly(ethylene glycol) (E) and poly(tetramethylene glycol) (B), with molecular weight (MW) of E and B 200–7500 and 1000, respectively. The reduced specific viscosity of copolymers increased with increasing MW and content of polyglycol comonomer. The temperature of melting (T_m), cold crystallization and glass transition (T_g) decreased with the copolymerization. T_m depression of copolymers suggested that the E series copolymers are the block type at higher content of the comonomer. T_g was decreased below room temperature by the copolymerization, which affected the crystallinity and the density of copolymer films. Water absorption increased with increasing content of comonomer, and the increase was much higher for E1000 series films than B1000 series films. The biodegradability was estimated by weight loss of copolymer films in buffer solution with and without a lipase at 37°C. The weight loss was enhanced a little by the presence of a lipase, and increased abruptly at higher comonomer content, which was correlated to the water absorption and the concentration of ester linkages between PET and PEG segments. The weight loss of B series films was much lower than that of E series films. The abrupt increase of the weight loss by alkaline hydrolysis is almost consistent with that by biodegradation.     

Molecular weight advancement of poly(ethylene ether carbonate) polyols

Poly(ethylene ether carbonate) polyols have been prepared from ethylene carbonate and monoethylene glycol (MEG) or diethylene glycol (DEG) using sodium stannate trihydrate as catalyst. When these polyols (catalyst removed) are heated to elevated temperatures (< 180°C) at reduced Pressures, volatile impurities are removed, as distillate, molecular weight builds in a controllable manner. This is thought to be a transesterification process in which ? OC(O)CH₂CH₂OCH₂CH₂OH end groups on one molecule react with carbonate moieties on a second molecule with loss of DEG. These advanced polyols form rapidly with high CO₂ retention and relatively low polydispersity. This process has been characterized by size exclusion chromatography, quantitative capillary gas chromatography of the distillates, ¹³C-NMR of the products, and alkaline hydrolysis of the products followed by quantification of the resultant glycols. The advanced polyols are largely alternating copolymers of DEG and CO₂. They are valuable polyols for polyurethane fabrication.     

Rheological and physical properties of polyarylate/LCP blend systems

A polyarylate Unitika U-Polymer 100 (PAR) was melt blended with a thermotropic liquid crystalline polymer (LCP) Vectra A950, and the processingmorphology-properties relations were investigated. Inclusion of LCP slightly reduced T_g of PAR. The PAR/LCP blend with the LCP content higher than 50 wt% exhibited a noticeable yield stress, particularly in the vicinity of crystal-to-nematic transition temperature (T_cn). LCP lowered the blend viscosity above T_cn and seemed to play a role as processing aid. The tensile strength of the blends was increased with increasing spin draw ratio and level of LCP, and the spinning temperature influenced tensile strength. The relaxation behavior under dynamic shear and resultant blend morphology based on WAXD and SEM analyses are discussed as well.