Polyester Diol Research Articles

Studies on preparation of silicon-containing polyester via ring-opening polymerization and new type of elastomers derived from the resulting diols

Silicon-containing polyesters represent a novel class of polymers that integrate silicone and polyester units within their main chain. Polysiloxanes typically consist of flexible chain segments, while polyesters are characterized by their rigidity. The combination of these two components in the main chain offers the potential for tunable properties across a broad range. For the first time, a new organosilicon cyclic ester monomer (Si-Mon) was synthesized using a pseudo-high dilution condensation method. Both theoretical and experimental studies confirm that the ring-opening reaction site of Si-Mon is the ester group, rather than the Si-O-Si bond. Silicon-containing polyesters (SiPET-Series 1) with molecular weights exceeding 20,000 Da were efficiently and rapidly synthesized at room temperature, utilizing benzyl alcohol as the initiator and t-BuP4 as the catalyst. Organosilicon polyester diols (SiPET-Series 2) with varying molecular weights were produced using 1,4-benzenedimethanol as the initiator. Additionally, a new type of organosilicon polyester elastomer (SiPET-E) was developed by employing SiPET-Series 2 as the base gum and (2,4,6-trioxotriazine-1,3,5(2H,4H,6H)- triyl)tris(hexamethylene)isocyanate (THDI) as the crosslinking agent. The stress–strain behavior of SiPET-E is influenced by the molecular weight of SiPET-Series 2. Notably, SiPET-E exhibits remarkable properties; for instance, it demonstrates superelastic characteristics when the molecular weight of SiPET-Series 2 is 13,000 g/mol, achieving a tensile strength of 2.56 MPa and an elongation at break of 776 % without the use of reinforcing fillers.

Structure, morphology, and properties of aliphatic polyurethane elastomers from bio‐based 1,3‐propanediol

AbstractThe utilization of biomass resources in the production of bio‐based or bio‐recycled polyurethanes (PUs) enhances the sustainable development and eco‐friendliness of PU. Herein, a series of new bio‐based aliphatic poly(propylene dicarboxylate) diols were synthesized using bio‐based 1,3‐propanediol (bio‐PDO) and aliphatic dicarboxylic acids with different chain lengths. These bio‐based polyester diols and 1,4‐butanediol (BDO) reacted with 4,4′‐dicyclohexylmethane diisocyanate to produce aliphatic PU elastomers (PUEs). The study aimed to evaluate the impact of the structure of poly(propylene dicarboxylate) diols on the architecture, morphology, mechanical properties, and degradation of PUEs, thereby expanding the application of bio‐PDO. The results indicate a strong correlation between the degree of microphase separation, tensile properties, and degradation behavior of the synthesized PUEs and the number of methylene groups in the repeating unit of the poly(propylene dicarboxylate) diols. Notably, the PUE derived from poly(propylene pimelate) diol demonstrates the highest level of microphase separation and superior elasticity properties because of the high flexibility of the polyester. On the other hand, PUE prepared from poly(propylene succinate) diol exhibits the fastest degradation performance due to its high density of ester groups. Bio‐PDO based polyester diols show significant potential as raw materials for PUEs with biodegradable and adjustable mechanical properties.Highlights Poly(propylene dicarboxylate) diols were prepared from bio‐based 1,3‐propanediol. The poly(propylene dicarboxylate) diols based polyurethane elastomers (PUEs) have high tensile strength (>22 MPa) and elongation at break (>920%). The morphology, mechanical properties and degradation of PUEs are highly related to the structure of the poly(propylene dicarboxylate) diols. The increasing repeating unit length of the poly(propylene dicarboxylate) diols increases elastic recovery of PUEs.

Preparation and Performance of Fluorocarbon Polyurethane Amino Baking Paint for Graffiti-Resistant Whiteboards

Fluorocarbon polyurethane amino baking paint for graffiti-resistant whiteboards was designed and prepared. Firstly, perfluorohexylethyl alcohol (TEOH6) and hexamethylene diisocyanate (HDI) were reacted under certain conditions to obtain fluorocarbon mono-isocyanate, then fluorocarbon diols were obtained by reacting with trimethylolpropane, and finally fluorocarbon polyurethane hydroxy resin was formed by reacting with hexamethylene diisocyanate (HDI) and polyester diols. The synthesized hydroxyl resin was used as the basis to configure fluorocarbon polyurethane amino baking paint for graffiti-resistant whiteboards and was upgraded by adding hydroxyl silicone oil. Secondly, a series of performance tests, such as hardness, adhesion, flexibility, and corrosion resistance, were conducted to verify that the baking paint possessed excellent properties for use on writing whiteboards. The graffiti resistance of each paint film was evaluated by different methods, and it was found that the graffiti resistance was mainly due to the excellent hydrophobicity and oleophobicity of the paint films after the enrichment of fluorocarbon chains on their surfaces, and the combined effect of low surface energy caused by hydroxyl silicone oil crosslinked with amino resin. This study provides a theoretical basis and technical support for the preparation of fluorocarbon polyurethane baking paint for graffiti-resistant whiteboards.

Dependence of Photothermal Rate Enhancements of Urethane Formation upon the Nature of Light Exposure and Solution Viscosity

The photothermal effect of nanoparticles naturally results in nanometer scale heat sources. Despite their highly localized nature, these heat sources can be used to drive bulk scale chemical transformations. However, due to the localization in both time and space, it is reasonable to expect that the time scale of heating, as well as transport of reactive species into and out of the heated volumes during this time, might play a role in determining the efficacy of photothermal heating for driving chemical reactions. Herein, we report an investigation into these effects for the reaction between hexamethylene diisocyanate and a series of alcohols to form urethane bonds. The length of photothermal heating is controlled via the duration of light exposure, using either a modulated continuous wave (2 min duty cycle) or a nanosecond pulse (8 ns pulses) laser that deliver nearly the same total energy to the system. Mass transport is controlled by changing the alcohol from butanol to butanediol to a polyester diol, resulting in reaction mixtures that change their viscosity from 1.66 to 206 cSt. We use infrared spectroscopy to follow the urethane production and associated isocyanate consumption. We then fit the course of the reaction to a kinetic model from which we extract rate constants used to quantify the degree of photothermal rate enhancement. For the chemical systems used, we find no significant dependence on viscosity. We also find that, for the light sources used, the average rate enhancement is not significantly affected by the length of light exposure, but the rate of the reaction during the time of exposure increases with larger instantaneous power.

Preparation of high‐performance polyurethane elastomers via direct use of alcoholyzed waste PET by high molecular weight polyester diols

AbstractProducts obtained by alcoholysis of waste PET are promising raw materials for the synthesis of polyurethane elastomers (PUEs). Alcoholysis of PET by low molecular weight diols such as ethylene glycol yields low molecular weight products. The latter need to be polymerized to high molecular weight polyols which are subsequently used as soft segments for the synthesis of PUEs. This work aims to look for suitable high molecular weight diols for the alcoholysis of waste PET to yield high molecular weight products which can be directly used as soft segments for the synthesis of PUEs. This approach allows to save the polymerization step for the formation of high molecular weight polyols. Specifically, polyester diols such as polycaprolactone diol (Mn = 2000) were used for the alcoholysis of waste PET. The resulting PUEs exhibited very good mechanical properties: a tensile strength of up to 40.95 MPa, an elongation at break of up to 1219%, and a toughness of up to 237 MJ·m−3, along with good transparency and thermal stability.

Homogeneous polyurethane foaming systems containing polyester diol, ethylene glycol, and alkylated polyethylenimine‐CO2 adducts

AbstractCO2 adducts from alkylated polyethylenimines (PEIs) in powder form are newly developed blowing agents for polyurethanes (PUs) to replace the ozone‐depleting and/or global warming halogen‐containing blowing agents. However, they are difficult to disperse into the raw materials of PUs. Herein, we explored reactive solvents for alkyl‐grafted PEI‐based CO2 adducts (xCn‐PEI‐CO2s, whose alkyl carbon number n = 4, 8, or 12 and grafting rate x = 5%, 10%, or 15%) and found that the most effective solvent was ethylene glycol (EG), with solute mass concentrations exceeding 50%. According to this, we designed homogenous foaming systems for PUs, containing poly(ethylene‐co‐diethylene glycol adipate)diol, EG, and different xCn‐PEI‐CO2 blowing agents, with mass percentages of 85, 11.25, and 3.75, respectively. The xCn‐PEI‐CO2 blowing agents in the ternary mixture could effectively blow PUs, with densities ranging from 210 to 240 kg/m3. The addition of 0.1 g of water as an extra blowing agent reduced the densities down to 110 kg/m3, compared with the 140 kg/m3 density of the control foam blown solely by water. The liquid status of the ternary foaming mixtures and their cooperative performance with water to blow PUs could enhance the suitability of the climate‐friendly xCn‐PEI‐CO2 blowing agents in PU foam industry.

Flame-Retardant and Smoke-Suppressant Flexible Polyurethane Foams Based on Phosphorus-Containing Polyester Diols and Expandable Graphite

A liquid-phosphorus-containing polyester diol, PPE, was prepared via condensation polymerization using commercial reactive flame retardant 9,10-dihydro-10-[2,3-di(hydroxycarbonyl)propyl]-10-phospha-phenanthrene-10-oxide, adipic acid, ethylene glycol, and 1,4-butanediol. PPE and/or expandable graphite (EG) were then incorporated into phosphorus-containing flame-retardant polyester-based flexible polyurethane foams (P-FPUFs). The structure and properties of the resultant P-FPUFs were characterized using scanning electron microscopy tensile measurements, limiting oxygen index (LOI), vertical burning tests, cone calorimeter tests, thermogravimetric analysis coupled with Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. Unlike the FPUF prepared using regular polyester polyol (R-FPUF), PPE increased the flexibility and elongation at break of the resultant forms. More importantly, the peak heat release rate (PHRR) and total heat release (THR) of P-FPUF were reduced by 18.6% and 16.3%, respectively, via gas-phase-dominated flame-retardant mechanisms, compared with those of R-FPUF. The addition of EG further reduced the peak smoke production release (PSR) and total smoke production (TSP) of the resultant FPUFs while increasing the LOI and char formation. Interestingly, it was observed that EG noticeably improved the residual quantity of phosphorus in the char residue. When the EG loading was 15 phr, the resulting FPUF (P-FPUF/15EG) attained a high LOI value (29.2%) and exhibited good anti-dripping performance. Meanwhile, the PHRR, THR, and TSP of P-FPUF/15EG were significantly decreased by 82.7%, 40.3%, and 83.4%, respectively, compared with those of P-FPUF. This superior flame-retardant performance can be attributed to the combination of the bi-phase flame-retardant behavior of PPE and condensed-phase flame-retardant characteristics of EG.

Synthesis and characterization of thermoplastic poly(piperazine succinate) metallopolymers coordinated to ruthenium(III) or iron(III)

AbstractMetal‐containing polymers represent an ever‐expanding frontier of material science. Of the numerous biocompatible ligands used to create a metallopolymer, piperazine‐containing polymers are still in their early development, even though piperazine is a common functional group in drug design and bioengineering scaffolding elements. We report the first synthesis and characterization (with NMR, IR, GPC, UV–vis spectroscopy, and thermal analysis) of two thermoplastic poly(alkyl piperazine succinate) diols with either propyl or hexyl alkane chains bridging the piperazines. These polyester diols were then chain extended with hexamethylene diisocyanate to create highly amorphous polyester urethane thermoplastic polymers. Ru(III) or Fe(III) was then successfully coordinated with these polymers, with approximately 30% of the bulk metallopolymer product becoming 250x the molecular weight of the non‐metal containing polymers. However, coordination of Fe(III), and to a lesser extent Ru(III), to these polypiperazines accelerated the hydrolysis of the polyester linkage in water over 15 days. Thus, these novel polymers are highly biodegradable with Fe(III) metallopolymers hydrolyzing faster than Ru(III) metallopolymers and poly(propyl piperazine succinate) polymers hydrolyzing faster than poly(hexyl piperazine succinate) polymers.

Influence of Skydrol immersion at elevated temperatures on the thermo‐mechanical properties of a high‐Tg anhydride epoxy resin toughened with a hydroxy‐terminated polyester

AbstractCurrently, the application of composites in aerospace parts exposed to higher temperatures and in aggressive media is still severely limited. To replace metal alloys, alternative resins systems with suitable long‐term heat resistance are needed. In this study, the effect of the aviation hydraulic fluid Skydrol on the thermal and mechanical properties of a high‐Tg, anhydride‐cured epoxy resin in the unmodified and toughened state at elevated temperature is investigated. An aliphatic polyester diol was selected as an intrinsic toughener and its impact on the thermal, mechanical, and aging properties was determined. Experimental characterization of the aging effects is carried out with dynamic‐mechanical characterization, infrared spectroscopy, and electron dispersion x‐ray spectroscopy. In addition, the fracture toughness and the fatigue crack propagation behavior are determined. Initially, the toughened system shows an improved fracture toughness. Since oxidation is blocked by the Skydrol fluid only thermal degradation takes place as determined by the decrease in glass transition temperature Tg and network density. The thermal degradation leads to a tougher behavior, which is observed in both systems in static and dynamic mode with toughness decreasing with aging time again.

Enhanced Mechanical and Thermal Properties of Chain-Extended Waterborne Polyurethane Coatings with Cellulose Acetate Butyrate.

A series of waterborne polyurethane (WPU) dispersions were prepared by chain-extending a prepolymer made of polyester diol, isophorone diisocyanate, and dimethylol propionic acid using cellulose acetate butyrate (CAB). The particle size and viscosity of the WPU dispersion were measured. In addition, we investigated the effects of CAB on the thermal, mechanical, and optical properties of WPU films. The use of CAB effectively improved the crosslinking degree of the WPUs, increasing the thermal stability and water resistance of the corresponding films. In particular, CAB increased the tensile strength of the WPU films up to 67%, while maintaining their elongation at break unchanged. In addition, CAB improved the optical transmittance by reducing the microphase separation between the soft and hard segments of PU. The rough surface structure of the WPU films formed by CAB led to improved matting properties.

Tuning Thermal, Morphological, and Physicochemical Properties of Thermoplastic Polyurethanes (TPUs) by the 1,4-Butanediol (BDO)/Dipropylene Glycol (DPG) Ratio.

Thermoplastic polyurethanes (TPUs) are versatile polymers presenting a broad range of properties as a result of their countless combination of raw materials—in essence, isocyanates, polyols, and chain extenders. This study highlights the effect of two different chain extenders and their combination on the structure–property relationships of TPUs synthesized by reactive extrusion. The TPUs were obtained from 4,4-diphenylmethane diisocyanate (MDI), polyester diols, and the chain extenders 1,4-butanediol (BDO) and dipropylene glycol (DPG). The BDO/DPG ratios studied were 100/0, 75/25, 50/50, 25/75, and 0/100 wt.%. The TPUs were characterized by size exclusion chromatography (SEC), Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), UV–vis spectroscopy, and physical-mechanical properties. The results indicate that DPG promotes compatibility between rigid (HS) and flexible (SS) segments of TPUs. Consequently, increasing DPG content (>75 wt.%) reduced the organization of the rigid segments and the degree of phase separation, increasing the polydispersity of the interdomain distance and the transparency in the UV–visible spectrum of the TPUs. Furthermore, increasing DPG content also reduced the amount of hydrogen bonds present in the rigid phase, reducing or extinguishing its glass transition temperature (TgHS) and melting temperature (Tm), and increasing the glass transition temperature of the flexible phase (TgSS). Therefore, increasing DPG content leads to a deterioration in mechanical properties and hydrolysis resistance.

Study on Preparation and Performance of Reactive Polyurethane Hot Melt Adhesives Based on a Polycarbonate Diol and a Polyester Diol

Reactive polyurethane hot melt adhesives (HMPURs) containing a mixture of poly 1,3-propylene sebacate diols (PPSe) and poly 1,6-hexanediol carbonate diols (PHC) as soft segments were prepared to investigate the influence of the relative content of PHC and PPSe on the properties of the HMPURs. The results showed that the HMPURs had excellent thermal stability below 250 °C; when the temperature was above 250 °C but below 360 °C, the HMPURs prepared from PPSe or PHC had better thermal stability than the HMPURs prepared from the mixture. With the increase of PHC content, the melting viscosity and elongation at break (δ) of the HMPURs decreased, while the open time and bond strength of the adhesive on PC substrates increased. When the polycarbonate diol content in the soft segments was higher than 50%, the HMPURs had better hydrolysis resistance than when it was lower.

Metal Ion Augmented Mussel Inspired Polydopamine Immobilized 3D Printed Osteoconductive Scaffolds for Accelerated Bone Tissue Regeneration

Critical bone defects with a sluggish rate of auto-osteoconduction and imperfect reconstruction are motivators for the development of an alternate innovative approach for the regeneration of bone. Tissue engineering for bone regeneration signifies an advanced way to overcome this problem by creating an additional bone tissue substitute. Among different fabrication techniques, the 3D printing technique is obviously the most efficient and advanced way to fabricate an osteoconductive scaffold with a controlled porous structure. In the current article, the polycarbonate and polyester diol based polyurethane-urea (P12) was synthesized and 3D porous nanohybrid scaffolds (P12/TP-nHA) were fabricated using the 3D printing technique by incorporating the osteoconductive nanomaterial titanium phosphate adorned nanohydroxyapatite (TP-nHA). To improve the bioactivity, the surface of the fabricated scaffolds was modified with the immobilized biomolecule polydopamine (PDA) at room temperature. XPS study as well as the measurement of surface wettability confirmed the higher amount of PDA immobilization on TP-nHA incorporated nanohybrid scaffolds through the dative bone formation between the vacant d orbital of the incorporated titanium ion and the lone pair electron of the catechol group of dopamine. The incorporated titanium phosphate (TP) increased the tensile strength (53.1%) and elongation at break (96.8%) of the nanohybrid composite as compared to pristine P12. Moreover, the TP incorporated nanohybrid scaffold with calcium and phosphate moieties and a higher amount of immobilized active biomolecule improved the in vitro bioactivity, including the cell viability, cell proliferation, and osteogenic gene expression using hMSCs, of the fabricated nanohybrid scaffolds. A rat tibia defect model depicted that the TP incorporated nanohybrid scaffold with immobilized PDA enhanced the in vivo bone regeneration ability compared to the control sample without revealing any organ toxicity signifying the superior osteogenic bioactivity. Thus, a TP augmented polydopamine immobilized polyurethane-urea based nanohybrid 3D printed scaffold with improved physicochemical properties and osteogenic bioactivity could be utilized as an excellent advanced material for bone regeneration substitute.

Synthesis, Characterization and Thermal Properties of Intrinsic Self‐Healing Polyurethane Nanocomposites

AbstractA hybrid thermo‐reversible crosslinking polyurethane nanocomposite containing 0.5, 1, and 2 wt.% of nano‐silica was prepared with three intrinsic self‐healing bonds (reversible covalent bonds supported by intrinsic hydrogen bonds and dangling chains). Owing to the introduction of pseudo‐tannin and polyester diol that could form phenol‐urethane networks and using nano‐silica that causes dangling chains and hydrogen bonds, the prepared polyurethanes are capable of being reversed at 110 °C and rejoin at low temperatures. Thermoset self‐healing polyurethane nanocomposites are prepared from pseudo‐tannin, nano‐silica, and a urethane‐based prepolymer. The investigations of chemical structure, self‐healing behavior, and cross‐link network are carried out by Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) technique, and swelling test. dissociation of phenolic urethane at 110 °C was confirmed by temperature variable FTIR. By swelling test, it was found that the self‐healing polyurethane nanocomposites with 0.5 wt.% of nano‐silica have the most hard‐domain, gel content, and crosslink density in the samples. DSC technique shows that polyurethane samples have two heat transfer transitions (dangling chains and self‐healing). Thermogravimetric analysis (TGA) findings show that nanocomposites decompose at elevated temperatures than neat PU, and the rate of degradation diminishes as silica content increases.

Reactive polyurethane hot melt adhesives based on polycarbonate and sebacic acid-based polyester polyols

Reactive polyurethane hot melt adhesives (HMPURs) containing a blend of polyester and polycarbonate diols can typically exhibit balanced performance, such as bonding properties, tensile strength, and heat resistance. Two series of HMPURs made from poly 1,4-butylene adipate or sebacic acid (SeA)-based polyester diols with different molecular weights were prepared and investigated. Increasing the molecular weight of the SeA-based polyester diols was found to significantly improve their mechanical properties and lap shear strengths. Moreover, the HMPURs made from SeA-based polyester diol exhibited better performances than those made from poly 1,4-butylene adipate. Also, the HMPURs were more suitable for bonding on PC substrate.

Synthesis and Characterization of Biodegradable Polyester/Polyether WPU as the Environmental Protection Coating

Polyester diol PCL and PBA, polyether diol PTMG and polycarbonate diol PCDL were used as components of WPU soft segment, respectively. Polyether PTMG-WPU has the worst hydrolytic property and the highest thermal stability. The maximum degradation rate temperature Tmax is 407.8 °C, the water contact angle reaches 89.5 °. Traditional polyester PCL-WPU shows the strongest hydrolysis performance, the smallest water contact angle, only 71.7 °, the water absorption rate of 72 h at room temperature is as high as 26.7%. However, the thermal stability of PCL-WPU is lower, the soft segment Tg is −52.3 °C, and Tmax is only 333.7 °C, but the mechanical property of which is the best, the tensile strength is 58.3 MPa, and the elongation at break reaches 857.9%. The most important thing is that the structure of polyester PCL-WPU is more easily destroyed by lipase and water molecules. The acidic products produced after hydrolysis will further promote the degradation of polyester. Therefore, compared with other WPUs, PCL-WPU has the best biodegradability and the most obvious degradation effect under the same conditions. The degradation rate of PTMG-WPU after 30 days of degradation in 0.6% lipase PBS buffer solution and soil was only 4.2% and 2.3%, while the highest degradation rate of traditional polyester PCL-WPU reached 41.7% and 32.0%, respectively. In addition, polycarbonate PCDL-WPU has the highest hardness, reaching 95.5 HD. But its other performances are lower than PCL-WPU.

Influence of preparation method on adhesion and drying performances of polyurethane dispersion

AbstractWaterborne polyurethane (WPU) dispersions with a high solid content were prepared by one‐step and two‐step methods with polyester and polyether type macromolecular diols as the main raw materials. The effects of two synthesis methods on the properties of WPU of polyester and polyether were studied. Fourier transform infrared spectroscopy, particle size and distribution, and Thermogravimetric analysis (TGA) measurements were utilized to characterize the structure. The dryness test results showed that the WPU synthesized with polyester diol as the soft segment by the two‐step method had the best drying. In addition, the microstructure of WPU was characterized by transmission electron microscopy, which confirmed that WPU was mainly spherical structure. TGA and scanning electron microscopy results showed that the microphase separation between the soft and hard segments of WPU prepared by the two‐step method was weaker, the hydrogen bonding was stronger, the adhesion, and thermal stability of WPU was improved.

Synthesis of reactive DOPO-based flame retardant and its application in polyurethane elastomers

An inherently flame-retardant polyester diol (FRPE) containing phosphorus was successfully synthesized via condensation polymerization with the commercial reactive flame retardant 9,10-dihydro-10-[2,3-di(hydroxycarbonyl)propyl]-10-phospha-phenanthrene-10-oxide (DDP), adipic acid (AA), ethylene glycol (EG), and 1,4-butanediol (1,4-BDO). Flame-retardant polyurethane elastomers (FR-PUEs) were subsequently produced by employing FRPE, 4,4-diphenylmethane diisocyanate (MDI) and 1,4-BDO. The mechanical and thermal properties and flame retardancy of the resulting FR-PUEs were characterized by tensile tests, thermogravimetric analysis (TGA), differential scanning calorimetric (DSC) analysis, dynamic mechanical analysis (DMA), limiting oxygen index (LOI) analysis, vertical burning tests (UL-94), and cone calorimeter (CC) analysis. It was suggested that DDP would increase the interaction between the hard and soft segments, resulting in FR-PUEs of unexpected higher tensile strengths of up to 40.0 MPa. In addition, it was found that the introduction of DDP can give rise to an increase of the residual char yield and limiting oxygen index (LOI), whereas reduces the total heat release (THR). Especially, using a low phosphorus content of 0.72 wt.%, the vertical burning level and LOI of the resultant FR-PUE reached V-0 and 24% respectively, and reduced THR of 52.6 MJ/m2 was obtained. The flame-retardant mechanism of phosphorus in DDP was proposed both in the gas and condensed phases based on cone calorimeter (CC), residual char analyses and TG-IR analysis.

Synthesis and properties of UV-curable polyester acrylate resins from biodegradable poly(l-lactide) and poly(ε-caprolactone)

Three kinds of bio-based polyester diols with different chain lengths, including polylactide diol (PLA-D), poly(ε-caprolactone) diol (PCL-D) and poly(ε-caprolactone-co-lactide) diol (PCLA-D), were synthesized by controlled ring-opening polymerization (ROP). Then UV-curable polyester acrylate resins (PLA-DA, PCL-DA and PCLA-DA) were synthesized by esterification modifying bio-polyols with methacrylic anhydride. Furthermore, the effects of chain length and polymer composition on the UV-curing and mechanical properties of polyester resins were investigated. The viscosity of both PLA-DA and PCL-DA increased sharply with the increase of molecular weight, and PCL can reduce the viscosity of PCLA-DA effectively. In the study of UV-curing kinetics, the increase of viscosity has a negative effect on the conversion and curing of double-bonds. The change trend of gel contents is basically consistent with the curing kinetics. The results of mechanical properties showed that the viscosity and double-bond conversion of the resins had a decisive influence on the mechanical properties of UV-cured materials. It was also found that with the increase of double-bond conversion and cross-linking density, the volume shrinkage of UV-cured materials increased significantly. The results of thermal analysis showed that the thermal stability of PCL-DA was better than that of PLA-DA, and the addition of PCL segments enhanced the thermal stability of PCLA-DA.

Improving water resistance of waterborne polyurethane coating with high transparency and good mechanical properties

Polyester based waterborne polyurethane (WPU) dispersions modified with hydroxypropyl-terminated polydimethylsiloxane (HPDMS) and sulfonate polyester diol were synthesized. The water resistance of WPU coating improved significantly when 5% HPDMS was used for modification, but it also leads to the decreasing of dispersion stability and damages in the mechanical properties and transparency of WPU coating. It was found that incorporating ionic groups in soft segments (sulfonate polyester diol) of WPU can obtain a coating with good water resistance where only 0.5% HPDMS is needed. In this case, the water swelling of WPU coating decreased to 7.0% while the pure WPU was 15.2%. Meanwhile, the mechanical and optical properties of modified coating change slightly. Its tensile strength was 62.6 MPa, and its light transmittance at 532 nm was 83.8%. Zeta potential test indicated the introduction of sulfonate polyester diol could improve the stability of WPU dispersions. The water resistance improvement of the WPU coating could be ascribe to the decrease of surface free energy and the change of phase separation degree. The water swelling, X-ray photoelectron spectroscopy, and contact angle test results demonstrated the migration of HPDMS and sulfonate polyester diol segments on the coating surface. The phase separation of WPU coatings was measured by dynamic thermomechanical analysis. The modified WPU with excellent water resistance is promising in the application of transparent coatings.