Polycaprolactone Diol Research Articles

Improving adhesion strength between steel and 2K polyurethane containing organic–inorganic hybrid nanoparticles and its performance optimization

This research has developed a novel adhesion promoter using organic-inorganic hybrid nanoparticles (ATS) to address existing limitations, such as the cumbersome separate coating and drying stages and insufficient adhesion. ATS was synthesized through hydrolysis-condensation reactions of an alkoxysilane-functionalized amphiphilic polymer (AFAP) precursor and 3-aminopropyltriethoxysilane (APTES). When directly mixed with resin part of polyurethane, ATS significantly enhanced the adhesion strength of 2 K PU to steel substrates without altering the mechanical properties or chemical structure of the polyurethane. An optimization process was conducted to determine the ideal mixing ratio of ATS with other components of 2 K PU, including different types of glycols (butylene glycol, propylene glycol, and ethylene glycol) and polyols to achieve the highest adhesive performance. The results showed that 2 K PU resin formed by using a mixture of polycaprolactone diol (PCD) and butylene glycol (BG) containing ATS (1−2) with nanoscale size (30.86 nm) exhibited superior adhesion performance over the other modified 2 K PUs and was 2.16 times higher than the common 2 K PU. These results were further validated via predictive model following response surface methodology to assess the precise impact of three parameters: the amount of AFAP (X1), amount of APTES (X2), and amount of BG (X3) on the adhesion strength of 2 K PU. The properties of different types of ATS and modified 2 K PU including particle size, degree of condensation, moisture content, molecular structure, molecular weight, hydrogen bonding intensity, microstructure morphology, and adhesion strength, were characterized.

Toward flexible electronics: A novel polyurethane integrating self‐healing, UV‐protective, reprocessable, and degradable properties

AbstractFlexible electronics are striving in modern society, and they impose harsh and urgent requirements for flexibility on electronic package substrates. However, traditional materials, including ceramics, metals, or polymers are lack of flexibility. Herein, a polyurethane named PU‐D1Q1VF1 is proposed via incorporating carefully selected biobased units and synergistic dynamic bonds, and the PU‐D1Q1VF1 not only meets the basic requirements of flexibility but also possesses properties of self‐heal, UV‐protection, reprocessability, and degradability. The polycaprolactone diol (PCL diol) was employed as the soft segment, and the bis(2‐hydroxyethyl) disulfide (HEDS) and lignin derived model monomer hydroquinone were selected as chain extenders. Moreover, carefully synthesized bio‐based monomer (E)‐4‐(((furan‐2‐ylmethyl)imino)methyl)‐2‐methoxyphenol (VF) was used as the capping agent, which could facilitate the self‐healing process of the PU‐D1Q1VF1.

Synthesis and characterization of bio‐based poly(urethane‐urea) nanocomposite coatings employing cellulose nanocrystals incorporated by two different routes

AbstractDuring the last decades, the interest in the development of materials fully or partially biobased has increased. Polyurethanes are extensively used in a wide range of industries because of their versatility. The present work explores the synthesis of partially biobased poly(urethane‐urea) (PUU) composites employing soy‐based polyol (SPO) and cellulose nanocrystals (CNC). The latter were incorporated during the synthesis (in‐situ) or after the synthesis (ex‐situ). The possibility of a technological application as coatings was investigated for the designed materials. Polycaprolactone diol was used as a soft segment due to high functionality of the soy‐based polyol. The physicochemical, thermal and mechanical properties of the prepared matrices were analyzed. Poly(urethane‐urea)s containing up to 20% by weight of biobased polyol showed coating application potentiality. Compared to a polycaprolactone‐based polyurethane, the utilization of the bioprecursor enhanced light absorption in the UV–Vis region. In addition, partially biobased systems showed better mechanical resistance (Young's modulus increased up to 6 times) and hydrophobicity (sweeling decreased from 60 to 8 per cent by weight). Incorporation of cellulose nanocrystals affected primarily the physicochemical and rheological properties of dispersions. Regarding coating properties, nanocrystals utilization complemented the soy‐based polyol improving the performance of the films. Furthermore, the incorporation route affected the dispersions and films properties.Highlights SPO was incorporated up to 20 per cent by weight in PUU composites. Higher SPO contents improved UV–Vis absorption and tensile strength of films. Films were less hydrophilic as more SPO was incorporated. The CNC‐reinforcement was complementary to the utilization of the SPO. CNC incorporation route affects properties and performance of the coatings.

Fluorine-free waterborne polyurethanes modified with bis-amino silane coupling agent: Synthesis and properties

Series of anionic waterborne polyurethanes (WPU) were synthesized with isophorone diisocyanate (IPDI) and polycaprolactone diol (PCL). Silane coupling agent (KH-792) was introduced into waterborne polyurethane system as modifiers. The effect of KH-792 contents on the properties of waterborne polyurethane was investigated. The Si-O bonds in KH-792 would be hydrolyzed into Si-O-Si bonds in the WPU system, forming a cross-linked network and improving the hydrophobic properties of WPU. The experimental results showed that the introduction of KH-792 significantly improved the glass transition temperature, thermal stability and water resistance of films. When the content of KH-792 was 1.5%, the comprehensive property of film was the best: the tensile strength was 26.80 MPa, the elongation at break was 693.83%, the adhesion was 1.74 MPa, and the T-type peel strength was 13.95 MPa. This offered a research basis for developing a new type of waterborne polyurethane fabric coating with strong adhesion, high mechanical properties and good water resistance.

The effect of polycaprolactone polyol molecular weight and chain extender type on the physico-mechanical properties and gas permeability of polyurethane thermoplastic elastomer membranes

ABSTRACT In this study, polyurethane thermoplastic elastomers (TPU) were synthesized using isophorone diisocyanate (IPDI), 1,4-butanediol (BDO), and 1,6-hexanediol (HDO) as the chain extenders, and polycaprolactone diol (PCL-diol) with three different molecular weights (2000, 4000, and 10,000 g/mol) as polyols. Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) patterns, and differential scanning calorimetry (DSC) were conducted to analyze the chemical microstructure and phase morphology of the prepared samples. The results showed that the change in the chain extender’s type (BDO and HDO) leads to a decrease in the hydrogen bonding index (HBI). Increasing the molecular weight of PCL-diol in BDO-based TPUs has led to an increase in their crystallinity, Young’s modulus, melting temperature, tensile strength, and a decrease in glass transition temperature and elongation at break. Moreover, the increase in the molecular weight of PCL-diol in HDO-based TPUs demonstrated an increase in the crystallinity and elongation at break and tensile strength up to the molecular weight 4000 in PCL-diol, after that, there was a decrease in those properties due to the increase of the soft segments content and change in the chain extender type. Permeability on TPU membranes was performed for N2 and CO2 at three different pressures 3, 6, and 9 atm at room temperature. An increase in pressure led to an increase in membrane permeability due to the increase in gas solubility in TPU based on Henry’s law. The permeability of CO2 is higher than N2 due to the proper interactions of CO2 gas with the polar carbonyl groups of polyurethane. It is observed that the permeability increases in BDO-based samples with an increase in the molecular weight of PCL-diol, while the increase in permeability of HDO-based TPU is up to PCL-diol molecular weight 4000 and after that is decreased. The selectivity of CO2 has decreased with increasing pressure due to the higher rate of dissolution of N2 at higher pressures.

Harnessing leather waste in polymer matrix for sustainable smart shape‐stable phase change materials

AbstractThe utilization of leather waste (LW) in a polyurethane (PU) matrix makes a smart and novel shape stable phase change material (SSPCM). This is essential for sustainability as it reduces landfill waste after use. The PU is synthesized in bulk with a 90% yield, using biodegradable polycaprolactone diol and bio‐based polyol (castor oil), along with tolylene‐2,4‐diisocyanate. PL and PLG composites are prepared by blending of constituent components PU (P), LW (L), and poly(glycidyl methacrylate) (PGMA, G), as specified by their code names. Role of LW (hydrogen bonding and chemical crosslinking) and morphology are elucidated by FTIR and SEM, respectively. Self‐healing time (2 h), shape fixity ratios (Rf) (PL: 60–80% and PLG: 60–70%) and shape recovery ratios (Rr) (100% for both) are determined at 60°C. PLG displays faster shape recovery in water (<30 s) compared to air (>300 s). Shape stability and thermal properties of the SSPCM are examined using the temperature responsive leakage study, TGA, and DSC. This research introduces a new approach for using leather waste (LW) in SSPCM, with self‐healing and 100% Rr. This material may find application where SSPCM with high durability and flexibility is essential such as textile and footwear materials.

Polyurethane Microstructures for 2'-Deoxycytidinic Acid Delivery: Preparation and Preliminary Characterization.

Background and Objectives: Nucleotide delivery has emerged as a noteworthy research trend in recent years because of its potential utility in addressing a range of genetic defects resulting in the presence of incorrect nucleotides. The primary goals of this research were to create and to characterize polyurethane microstructures, with the aim of utilizing them for nucleotide transport. Materials and Methods: Two samples were prepared using an aliphatic diisocyanate in reaction with a mixture of polyethylene glycol and polycaprolactone diol, where 2'-deoxycytidinic acid was used as the active agent and glycerol 1,2-diacetate was used as an enhancer of the aqueous solubility. The solubility, pH, size distribution, and surface charge of the samples were measured, and encapsulation efficacy and release, cell proliferation, and irritation tests on mouse skin were conducted. Results: The results showed almost neutral acidic-basic structures with a high heterogeneity, and a medium tendency to form clusters with non-cytotoxic and non-irritative potentials. Conclusions: Future research could explore the efficacy of this carrier in delivering other nucleotides, as well as investigating the long-term effects and safety of these microstructures in vivo.

Versatile ionic liquid gels formed by dynamic covalent bonding and microphase separated structures.

It is challenging for ionic liquid gels to achieve the combination of rapid self-healing with high toughness. Here, ionic liquid gels (DI-PR) were prepared from readily available materials. A dynamic covalently bonded oxime-carbamate was prepared from polycaprolactone diol, isophorone diisocyanate and dimethylethyleneglyoxime, followed by addition of the "rigid-flexible" cross-linking agent rutin to chemically cross-link the polymer chains and afford the ionic liquid gels, DI-PR. The tensile strength, elongation at break and toughness of the DI-PR gels were as high as 16.5 MPa, 1132.6%, and 52.6 MJ m-3, respectively. The toughness is similar to that of natural silkworm silk (70 MJ m-3) and wool (60 MJ m-3). After stretching, the DI-PR can rebound within 1 s, their room temperature self-healing rate is as high as 92%, they remain functional over the temperature range -50 °C to 140 °C and the interface with a steel plate has an adhesion toughness of >2000 J m-2. These properties mean that the DI-PR gels are particularly suitable for use as anticorrosion coatings for submarine and underground gas and oil pipelines. The use of rutin, which combines rigid quercetin-based structural units with flexible glycoside-based structural units, as a cross-linking agent, provides a new method for improving the toughness of soft materials through its synergistic interaction with hard and soft chain fragments of polyurethanes.

Preparation and properties of shape memory polyurethane filaments triggered by human body temperature

To utilize the human body heat to trigger the shape memory smart textiles, shape memory polyurethane filaments (SMPUF) with three different transition temperatures were prepared based on modified polycaprolactone diol (PCL) by dry spinning. The chemical structure was characterized systemically. The shape memory properties, tensile properties, resilience, and viscoelasticity were studied comprehensively. The results revealed that the phase transition temperatures were close to human body temperature which measured 19.97°C, 27.33°C, and 30.37°C, respectively. Additionally, the fraction of hydrogen bonds in the samples was about 30% less than that of polyurethane filaments (PUF). The best shape fixity ratio was 88.5% and the shape recovery ratio was 96.7% belonging to samples with a transition temperature of 30.37°C. At 55°C, the elastic recovery was 45.2% higher than that at 22°C. As the temperature rose, the elastic modulus of SMPUF decreased until it reached that of PUF. The static and dynamic viscoelasticity of SMPUF indicated that the phase transition of the soft segment affects the movement of the molecular chain. SMPUF can be used as compression garments, and wearable orthopedic devices, such as the elastic bands prepared in this work.

Bio-inspired self-healing and anti-corrosion waterborne polyurethane coatings based on highly oriented graphene oxide

In the face of ubiquitous corrosion threats, the development of high-performance elastomer protective materials with active self-healing functions is extremely challenging and significant. We propose an approach by combining WPU elastomer with GO to create the multifunctional pearl layer structured polymers with interface hydrogen bonds. By crosslinking the polycaprolactone diol (PCL) chain with a hydrogen bond array, the elastomer with high mechanical strength, extensibility, elasticity, excellent damage resistance, and healing properties was successfully synthesized. The elastomer exhibits remarkable mechanical properties, including a tensile strength of 39.89 MPa, toughness value of 300.3 MJ m−3, and fracture energy of 146.57 kJ m−2. The enhanced damage resistance of the elastomer can be attributed to the decomposable hydrogen bond array as well as the strain-induced crystallization of PCL fragments, which effectively dissipate energy. Importantly, due to the reversibility of the hydrogen bonding array, the fractured WPU can easily heal and restore its original mechanical properties when subjected to heating at 50 °C. Moreover, the photothermal properties of GO enable the biomimetic polymer coating to achieve damage recovery after being irradiated with NIR for 30 s. The obtained biomimetic coating exhibits a highly oriented lamellar structure, thereby greatly enhancing physical barrier performance and anti-corrosion performance. Electrochemical impedance spectroscopy (EIS) shows that the impedance modulus is one order of magnitude higher than that of the blank coating. Additionally, scanning vibrating electrode (SVET) confirmed that the self-healing performance and protection effect of the biomimetic coating in 3.5 wt% NaCl solution were also reliable. This highly reliable biomimetic coating presents a revolutionary solution for creating multi-functional, high-performance smart material in harsh environments.

Polyol-dependent adhesion mechanism of XDI- and H6XDI-based polyurethanes

Polyurethanes (PUs) consisting of m-xylylene diisocyanate (XDI) exhibit excellent thermal stability and optical properties. To further enhance the optical properties, 1,3-bis(isocyanatomethyl)cyclohexane (H6XDI) is considered a potential isocyanate for optically clear adhesives; however, a detailed analysis of the adhesion mechanism has not been investigated. Herein, we synthesized PUs using diisocyanates (XDI, H6XDI) and polyols [polypropylene glycol (PPG), polycaprolactone diol (PCL), and polycarbonate diol (PCD)]. To investigate the adhesion mechanism, the interaction between each PUs and functionalized self-assembled monolayers was analyzed using a Surface Forces Apparatus at the nanoscale. Additionally, macroscopic surface energy measurement and probe tack testing were performed. Overall, higher hydrophobic interaction in PCD-containing PUs and predominant hydrogen bonding in PPG-containing PUs was measured. Also, hydrophobic interaction was stronger for H6XDI compared to that of XDI in all polyols. These findings clarified polyol-dependent adhesion mechanisms of XDI- and H6XDI-based PUs and could be used to design PUs with controlled strength of hydrogen bonds and hydrophobic interactions.

Organic Nitrate Additive for High-Rate and Large-Capacity Lithium Metal Anode in Carbonate Electrolyte.

Lithium nitrate has been widely used to improve the interfacial stability of Li metal anode in ether electrolyte. However, the low solubility limits its application in carbonate electrolytes for high-voltage Li metal batteries. Herein, nitrated polycaprolactone (PCL-ONO2 ), which is prepared via the acylation of polycaprolactone diol (PCL-diol) followed by the grafting of nitrate group, has been proposed as an electrolyte additive to introduce high-concentration NO3 - into carbonate electrolytes for the first time. The theoretical calculations and X-ray photoelectron spectroscopy depth profiling demonstrate that the PCL-ONO2 additive preferentially reacts with Li metal and in situ constructs a stable dual-layered solid electrolyte interphase film, presenting an inner nitride-rich layer and an outer flexible PCL-based layer on the surface of Li metal anode. As a result, the Li metal anode delivers an impressive long-term cycling performance over 1400h at an elevated area capacity of 10.0mAhcm-2 and an ultrahigh current density of 10.0mAcm-2 in the Li symmetrical cells. Moreover, the PCL-ONO2 additive enables the full cells constructed by coupling high-loading LiFePO4 (20.0mgcm-2 ) or LiNi0.5 Co0.2 Mn0.3 (16.5mgcm-2 ) cathode and thin Li metal anode (≈50µm) to demonstrate greatly improved cycling stability and rate capability.

Impact of Soft Segment Composition on Phase Separation and Crystallization of Multi-Block Thermoplastic Polyurethanes Based on Poly(butylene adipate) Diol and Polycaprolactone Diol

In this work, we explore the influence of soft segment structure on the crystallinity and phase separation of semicrystalline multi-block thermoplastic polyurethanes (TPUs) based on poly(butylene adipate) diol, polycaprolactone diol, and their mixture. According to thermal and structural analyses, the crystal growth rate and degree of crystallinity decrease with an increase in the PCL/PBA ratio and reach a minimum at the equimolar composition of polyesters. A reduction in crystal phase content leads to an improvement in elastomeric behavior. TPU samples with high PCL content demonstrate enhanced crystallinity but a lower melting temperature compared to TPU with PBA crystals. Crystallization of TPU below room temperature results in an enhancement of total crystallinity and a change in the phase composition of the PBA block. The difference in semicrystalline morphology and crystallization kinetics can be explained by the efficiency of phase separation and the density of hydrogen bonding between soft and hard segments. Our findings show that the ratio of the two crystallizable polyesters, combined with the choice of crystallization temperature, allows for independent control over the melting temperature and the overall degree of crystallinity of the TPUs. This significantly impacts the mechanical characteristics of the materials. The effect of adding a second crystallizable polyester on the crystallization behavior, phase composition, and mechanical properties of TPU is discussed for the first time.

Biodegradability and Thermostability of Renewable Waterborne Polyurethane Synthesized from Trihydroxyl poly(L-malic acid)/glycol Based Polyols and Polycaprolactone Diol

Biodegradability and Thermostability of Renewable Waterborne Polyurethane Synthesized from Trihydroxyl poly(L-malic acid)/glycol Based Polyols and Polycaprolactone Diol

The Influence of Soft Segment Structure on the Properties of Polyurethanes.

A series of polyurethanes (PU) were synthesised via one-step polymerisation without a chain extender, using toluene diisocyanate as well as a variety of soft segments composed of different macrodiols. Poly(D,L-lactide) (PDLLA) and polycaprolactone diol (PCL) were synthesised as a polyester type polyols to obtain soft segments. The process of varying the molar ratio of newly synthesised PDLLA in soft segments has been confirmed as a powerful tool for fine-tuning the final properties of PU. Fourier-transformed infrared spectroscopy was used for evaluation of molecular structures of synthesised PDLLA polyol and final PU. Nuclear magnetic resonance spectrometry was used to confirm the presumed structure of PU. The influence of soft segment composition on polyurethane thermal characteristics was examined using thermogravimetric analysis and differential scanning calorimetry. The composition of soft segments had little impact on the thermal stability of PU materials, which is explained by the comparable structures of both polyester polyols. Wide-angle X-ray scattering was utilised to evaluate the effect of amorphous PDLLA on the degree of crystallinity of PCL in soft PU segments. It was discovered that not only did the PDLLA ratio in the soft segment have a substantial influence on the degree of microphase separation in the soft and hard segments, but it also influenced the crystallisation behaviour of the materials. Furthermore, the restriction of crystallisation of the PCL soft segment has been verified to be dependent on the hard segment concentration and the ratio of PDLLA/PCL polyols. The sample with pure PCL as the polyol component achieved the highest degree of crystallinity (34.8%). The results demonstrated that the composition of soft segments directly affected the properties of obtained polyurethane films. These results can be utilised to easily achieve a desirable set of properties required for application in biomaterials.

Synthesis and properties of biodegradable waterborne polyurethane modified as castor oil

A series of biodegradable waterborne polyurethane (WPU) based on polycaprolactone diol and castor oil is synthesized through the process of the polyaddition reaction. Biodegradable WPUs are designed by using polycaprolactone diol and 4,4′- methylene dicyclohexyl diisocyanate as the main domain of urethane, dimethylol butanoic acid as the anionic internal emulsifier and trimethylamine as the neutralizing agent. Castor oil is introduced as a key component to induce or maximize the biodegradability and biocompatibility of a WPU series. The biodegradable ability of WPUs are changed by the control of Castor oil content and molecular weight (MW). The biodegradation of a WPU series prepared in this study is analyzed in field emission scanning electron microscopy through visual modifications in bio-enzyme evaluation. The effects of Castor oil and MW on the physical properties are evaluated using gel permeation chromatography (GPC), universal test machine (UTM), dynamic light scattering (DLS), differential scanning calorimetry (DSC), and field emission scanning electron microscopy (FE-SEM). The WPU with high level of MW and Castor oil shows enough enhancement in tensile strength and Young's modulus, ranging from 12.28 to 23.47 MPa and from 0.04 to 0.137 MPa, respectively. SEM results point to a significant microphase biodegradation of a WPU series by bio-enzymes. It can be an environmental-friendly candidate to apply various biofields.

Thermoplastic polyurethane-based shape memory polymers with potential biomedical application: The effect of TPU soft-segment on shape memory effect and cytocompatibility

Stimuli-responsive biocompatible polymer blends with adjustable properties are highly desirable for biomedical applications. It is crucial to meticulously consider the chemical structure and composition of each polymer to prepare a melt-miscible blend system that possesses desirable shape memory and cytocompatibility performance. Herein, we developed thermo-responsive SMPs by melt-blending Polycaprolactone (PCL) with two different Thermoplastic polyurethanes (TPU) composed of the same hard segment, but different soft segments derived from adipic acid polyester and polycaprolactone diols and the critical role of TPU chemical structure on the thermomechanical properties and biocompatibility of TPU-based SMPs were investigated and uncovered. Cyclic thermomechanical tests show that compared with adipic acid-based TPU/PCL blends, PCL diol-based TPU/PCL blends exhibit remarkable shape memory properties (Rf and Rr >90%) with the ability to start recovery at lower temperatures (∼45 °C), while the cytotoxicity and wettability studies implied higher biocompatibility and hydrophilicity of adipic acid-based TPU/PCL blends making them more favorable substrates for cell proliferation.

Mechanically robust waterborne polyurethane with excellent room temperature self-healing and shape memory performance

Achieving severe damage restoration and the ideal combination of good mechanical properties and healing efficiency are two significant challenges for self-healing materials. In this study, a series of shape-memory, self-healing aqueous polyurethane (SMPU) were synthesized based on the molecular self-assembly design of 5-(2-hydroxyethyl)-6-methyl-2-aminuracil (HMA), 4-aminopyridine (4-APD) and polycaprolactone diol (PCL) moieties. The effects of HMA and 4-APD on mechanical properties, self-healing properties, and shape memory properties of SMPU were investigated. The dynamic crosslinking network generated by quadruple hydrogen bonds and multiple coordination bonds not only consumed strain energy but also promoted rapid re-formation after fracture, resulting in superior self-healing ability (healing efficiency 96.3%), excellent mechanical properties (tensile strength 39.1 MPa and elongation at break 908%) and recyclable capabilities of SMPU. Meanwhile, the SMPU showed a noteworthy shape memory effect; its shape fixation rate and recovery rate could reach 99% and 98%, respectively. The temperature and time dependence of the self-healing process were studied by molecular dynamics (MD), and the self-healing mechanism was clarified further. When SMPU was used for leather finishing, the finished and self-healing samples exhibited excellent wear resistance (wear rating: 4 ∼ 5). These advantageous properties endow SMPU with great potential applied value in leather and other regions.

Green construction and release mechanism of lignin-based double-layer coated urea

BackgroundLignin played an important role in the establishment of coated fertilizers coating material as a substitute for petrochemical raw materials. However, so far, the lignin-based coated fertilizers was limited in only the poor slow-release performance. To achieve good slow-release performance of lignin-based coated fertilizers, hydrophilic of lignin need to be resolved to establish an green and better controllable lignin-based coated fertilizers.ResultsIn the study, a novel green double layer coating with lignin-based polyurethane (LPU) as the inner coating and epoxy resin (EP) as the outer coating was effectively constructed for coated urea. Fourier transform infrared spectra confirmed that lignin and polycaprolactone diol successfully reacted with Hexamethylene diisocyanate. The loss weight and water contact angle (WCA, 75.6–63.6°) of the LPUs decreased with the increased lignin content. The average particle hardness of the lignin-based double-layer coated urea (LDCU) first increased from 58.1 N (lignin of 30%) to 67.0 N (lignin of 60%), but then decreased to 62.3 N (lignin of 70%). The release longevity of the coated urea was closely related to the preparation parameters of the coating material. The optimal cumulative nutrient release rate (79.4%) of LDCU was obtained (lignin of 50%, –CNO/–OH molar ratios of 1.15, EP of 35%, and coating ratio of 5%). The aggregates of hydrone on the LDCU caused the dissolution and swelling of nutrients, and then the diffusion of nutrients through the concentration gradient.ConclusionsA though the nutrient release of the LDCUs was affected by many factors, the successful development of the LDCUs will help improve the rapid development of the coated fertilizer industry.

Development of amylopectin based polyurethanes for sustained drug release studies

In this research work, the crosslinked structure of polyurethane has been exploited for sustained drug delivery. Polyurethane composites have been prepared by the reaction of isophorone diisocyanate (IPDI) and polycaprolactone diol (PCL), which were further extended by varying the mole ratios of amylopectin (AMP) and 1,4-butane diol (1,4-BDO) chain extenders. The progress and completion of the reaction of polyurethane (PU) were confirmed using Fourier Transform infrared (FTIR) and nuclear magnetic resonance (1H NMR) spectroscopic techniques. Gel permeation chromatography (GPC) analysis showed that the molecular weights of prepared polymers were increased with the addition of amylopectin into the PU matrix. The molecular weight of AS-4 (Mw ≈ 99,367) was found threefold as compared to amylopectin-free PU (Mw ≈ 37,968). Thermal degradation analysis was done using thermal gravimetric analysis (TGA) and inferred that AS-5 showed stability up to 600 °C which was the maximum among all PUs because AMP has a large number of –OH units for linking with prepolymer resulting in a more cross-linked structure which improved the thermal stability of the AS-5 sample. The samples prepared with AMP showed less drug release (<53 %) as compared to the PU sample prepared without AMP (AS-1).