Star oligomers and hyperbranched polymers in low VOC polyurethane coatings: Part III

Conclusion  In this paper the effects of the functionality of hydroxyl functional star oligomers and dendritic polys have been demonstrated in a low VOC clear 2-component clear coat crosslinked with a polysocyanate. At a fixed initial composition of the overall system and with the same reactivity of hydroxyl and isocyanate functional groups, the molecular weight increase as a function of time and the conversion can be calculated using the theory of branching processes. The study has shown that the practical results agree quite well with theory and that the potlife is shortened in case of higher functionality as well as in the case of a broad functionality distribution. The hardness in such a system is not only the effect of functionality, but also of solvent evaporation during crosslinking. If the molecular weight increase upon drying is too fast due to a high functionality (and/or distribution), early gel formation can result in a low film glass transition temperature and hardness due to solvent entrapment.     

Linear pendant anhydrides: novel building blocks for high solids, high performance coatings

Increasing sensitivity to environmental issues worldwide has led to unique new driving forces that are shaping the development of coatings technology for the future. While lower VOC (volatile organic compound) levels in paints and coatings offer compliance with legislative mandates, they do not necessarily offer appearance and/or performance benefits consistent with demands from manufacturers and consumers. Therefore, it is incumbent upon materials suppliers and coatings formulators to improve the overall performance of coatings from primers to clearcoats while operating in the higher solids realm which is now necessary. Recent work at DOW has led to the development of unique raw materials for solventborne coatings which allow for medium to very high solids (2.6 lbs VOC/gal or less) formulations that handle and perform like low solids/high VOC formulations. These new raw materials have been coined ‘linear pendant anhydride’ (LPA) resins — a broad term which applies to materials from low molecular weight oligomers to high molecular weight polymers. When formulated with epoxy resins, very high solids levels can be obtained with superior overall performance to other ‘state-of-the-art’ coatings technologies (i.e. 2-component polyurethane enamels). Discussed here are details of the essential resin chemistry, formulation and testing of LPA-based coatings for both ambient and thermal cure applications. Particular emphasis is on the remarkable durability of these coatings.     

Star oligomers with different reactivity in low VOC polyurethane coatings: Part II

Conclusions  In this paper the effects of the reactivity of hydroxyl functional oligomers with a polyisocyanate crosslinking agent have been demonstrated by comparing the potlife/hardness of a 3.5 VOC two-component polyurethane clear coat based on a low TG, high reactive against a high TG, low reactive oligomer. The reaction rate of two polymers forming a crosslinked network becomes diffusion controlled when, during the reaction, the increasing TG comes close to the reaction temperature.⁴ If this reaction takes place in the presence of a solvent which evaporates during film formation and crosslinking, the speed of evaporation will affect both the reaction rate and the film TG. The results of this study have shown that the reactivity determines the potlife whilst the TG controls the hardness. The reactivity of blends of such oligomers against pure oligomers is different as can be calculated using the theory of branching processes and as shown from practical measurements. Blends of oligomers or a pure oligomer with up to 75% of the properties of the high TG, low reactive oligomer do show a hardness close to the properties of the low TG, high reactive oligomer which further proves that the chemical reactivity controls the overall drying performance. A fast chemical reactivity shortens the potlife with a risk of solvent entrapment near to and at the gel point which results in low hardness.     

Low VOC carbamate functional coatings compositions for automotive topcoats

Polymers and oligomers having carbamate functional groups have been used in a variety of curable coating compositions. Carbamate functional polymers offer many advantages for automotive topcoats, such as outstanding resistance to environmental etching, scratching and marring, humidity, and UV exposure. Hydrophobic carbamate oligomers suitable for crosslinking with standard amino resins were synthesized and formulated into stable one-pack automotive clearcoats with low volatile organic compound (VOC) and excellent physical properties. Because of their unusually steep thermal viscosity curves, these oligomers are particularly adaptable to hot spray techniques that enable coatings in the 85–90% weight solids range to be applied with conventional electrostatic mini-bells. Presented at the 27th Annual International Waterborne, High-Solids, and Powder Coatings Symposium, in New Orleans, LA, March 2000. Automotive Coatings Technical Center, Southfield, MI 48034.     

Two-component high-solid polyurethane coating systems based on soy polyols

Soybean oil based polyols—soybean oil phosphate ester polyols (SOPEPs)—having varying hydroxyl content and viscosity were prepared as low cost and low-VOC polyols for coatings applications. These SOPEPs were used as the hydroxyl component of “two-component polyurethane (2K-PU)” coating compositions and their film properties were studied. Blends of commercial polyester polyol and SOPEP in varying proportions were also used to formulate PU coatings. Their film properties were studied and compared. We found that SOPEP can be used as the sole hydroxyl component or as the reactive diluent for polyester polyols in 2K-PU coating systems. SOPEP, is derived from a relatively inexpensive and renewable resource and the use of SOPEP can substantially reduce VOC and cost of PU coating formulations. Presented at the International Waterborne, High-Solids, and Powder Coatings Symposium, New Orleans, LA, February 2002.     

改善冰箱用环戊烷-异戊烷发泡体系流动性方法的探讨

探讨了冰箱用硬质聚氨酯泡沫塑料环戊烷一异戊烷发泡体系中聚醚、催化剂、匀泡剂及环戊烷／异戊烷比例等因素对发泡物料流动性的影响。结果表明，采用低粘度、与环戊烷／异戊烷混合物互溶性好、有适当官能度和羟值的聚醚有助于改善发泡流动性；采用适当的催化体系能改善代表发泡流动性的泡沫上升高度和降低泡沫密度分布梯度；采用合适的匀泡剂并且用量适当，能改善发泡流动性，促进泡沫分布均匀；采用适当的环戊烷／异戊烷比例，可改善泡沫流动性。     

High performance waterborne coatings based on dispersions of a solid epoxy resin and an amine-functional curing agent

A novel, waterborne epoxy system comprised of non-ionic stabilized dispersions of a solid epoxy resin and an amine curing agent has been designed for ambient-cure coatings. The performance characteristics of coatings formulated from the new system have been compared to a standard system. The new system produced formulated coatings with robust performance over a wide range of amine-to-epoxy stoichiometries (65 to 130%). At 100% stoichiometry, the new system was found to have lower VOC, faster hardness development, better gloss, and higher impact resistance than the standard system. The new formulations also exhibited superior water and salt spray resistance, and a definitive viscosity rise at the end of potlife. Unlike the standard system, coating morphology of the new waterborne system was found to be similar to a solvent-based coating. For the new system, good coalescing solvents, as judged by gloss and gloss potlife, were found to have low solubility parameters and high boiling points. Presented at the 76th Annual Meeting of the Federation of Societies for Coatings Technology, on October 15, 1998, in New Orleans, LA. P.O. Box 1380, Houston, TX 77251-1380.     

Preparation and characterization of high-solid polyurethane coating systems based on vegetable oil derived polyols

A series of bio-based polyols with high functionality and low viscosity were synthesized from 5 different vegetable oils (refined or crude). Their chemical structures and the distribution of oligomers in these polyols (known as Liprol™) were characterized. Liprol structures varied due to the fatty acid profile of the starting oils and their overall degree of unsaturation, along with the extent of oligomerization during their formation. These polyols were then used as starting materials for the production of high-solid content polyurethane (PU) coatings, by reacting them with commercial petrochemical derived diisocyanate and other additives. All of the PU coatings obtained had a bio-based content of around 60% and showed good thermo-mechanical and mechanical properties. NuLin^® flax PU, made from oil with the highest linolenic acid content, had the highest glass transition temperature, high contact angle with water, good abrasion resistance and Shore hardness, low degree of solvent swelling and formed highly cross-linked networks.     

Oligomeric Composition of Polyols From Fatty Acid Methyl Ester: The Effect of Ring‐Opening Reactants of Epoxide Groups

Commercial availability of fatty acid methyl ester (FAME) from palm oil targeted for biodiesel offers a good feedstock for the production of structurally well‐defined polyols for polyurethane applications. The effect of molecular weight (MW), odd and even carbon numbers, and the linear and branched structure reactants used in the ring‐opening reaction of epoxidized fatty acid methyl ester (E‐FAME) on the properties of polyols was investigated. Conversions of E‐FAME to PolyFAME polyols were confirmed by Fourier transform infrared analysis, oxirane oxygen content, and hydroxyl number. Gel permeation chromatography (GPC) calibrated against polyether polyols as a standard and vapor pressure osmometry were used for MW determination. GPC chromatograms of PolyFAME polyols clearly demonstrated the formation of oligomers during ring‐opening reactions. MW, and odd and even carbon numbers in a structure of linear diols and branched diol used in the syntheses of PolyFAME polyols did not have an effect on crystallinity, glass transition, or melt temperatures measured using Differential scanning calorimetry (DSC). PolyFAME polyols ring‐opened with water, methanol, and 1,2‐propanediol contained secondary hydroxyl groups, whereas PolyFAME polyols ring‐opened with linear diols contained a mixture of primary and secondary hydroxyl groups. It was found that the concentration of primary hydroxyl groups increased significantly by increasing the number of carbons from C2 to C3 in the linear diols. The viscosity of PolyFAME polyols also increased with the MW of linear diols used in the E‐FAME ring‐opening reaction. These findings would be beneficial for formulators in choosing the most cost effective polyols for polyurethane formulations.     

双金属氰化物催化剂的研究进展

综述了近年来双金属氰化物（DMC）催化剂的研究进展，指出DMC催化剂是一类用于环氧化物的高效催化剂，与传统的环氧化物催化剂相比，其制得的聚醚多元醇具有分子量高、不饱和度低、分子量分布窄、平均官能度高等优点。但该催化剂在应用过程中仍存在一些缺点。针对这些缺点，国内外的高校、企业已进行了大量的改性研究工作。     

Calibration procedures in gel permeation chromatography

Procedures for the determination of the log molecular weight vs. elution volume calibration relation are reviewed for linear homopolymers. The calibration curve is readily established with narrow molecular weight distribution fractions. For broad molecular weight distribution fractions the peak molecular weight at the peak elution volume of a fraction's gel permeation chromatogram has to be calculated from average molecular weights. When well-characterised fractions of the polymer requiring analysis are unavailable, a calibration curve can be established by procedures which assume that the hydrodynamic volume of a polymer molecule in solution controls fractionation in gel permeation chromatography. These universal calibration procedures require information on Mark-Houwink viscosity constants or polymer unperturbed dimensions. The validity of hydrodynamic volume as the universal calibration parameter is discussed with special reference to the goodness of the solvent for a polymer and polymer polarity. Examples are given of the various calibration procedures which are employed in the determination of molecular weight distribution and average molecular weights for poly(methylmethacrylate), polyethylene and polyisoprene.     

Properties of polyisobutylene polyurethane block copolymers: 2. Macroglycols produced by the ‘inifer’ technique

The structure-property relationships of a series of 4,4′-diphenylmethane diiscoyanate (MDI) based polyisobutylene (PIB) polyurethanes were investigated. The PIB glycol was synthesized via the ‘inifer’ technique and had a narrow functionality distribution with a number average functionality of 2.0. The use of a PIB glycol with improved functionality and solution polymerization of the polyurethane led to improved mechanical properties compared with previously studied PIB polyurethanes. However, the mechanical properties were still low compared with conventional polyurethanes; the absence of soft segment strain-induced crystallization and compositional heterogeneity due to reactant incompatibility are cited as possible causes of low mechanical properties. Sample compositions were designed for independent investigation of the effects of hard segment content and soft segment molecular weight on the properties of the materials. Increasing hard segment content resulted in improved dynamic and tensile modulus, lower elongation at break, and larger hard segment domains. Increasing soft segment molecular weight led to larger domains and reduced mechanical properties. The degree of phase separation as measured by the soft segment T_g and the amount of interfacial mixing measured by small angle X-ray scattering (SAXS) were unaffected by hard segment content and soft segment molecular weight and were indicative of a high degree of phase separation compared with conventional polyurethanes.     

Novel Self-Crosslinking Epoxy Oligomers for Cationic-Cure Coatings Applications

ABSTRACT

Novel epoxy functional oligomers containing phosphate-esters, carboxylate-ester, and urethane linkages with varying molecular weight and functionality have been synthesized from commercially available epoxy compounds. These oligomers are characterized for the parameters relevant to the study by physical, spectroscopic, and chemical methods. Two series of cationic thermal-cure coating compositions have been formulated using these oligomers as principal film-forming components. The cured films of these self-crosslinked oligomers have been studied and compared. A correlation between structure of these oligomers and their film properties has been established.     

Preliminary study on bio-based polyurethane adhesive/aluminum laminated composites for automotive applications

Composite materials that are offered for real applications in the automotive industry vary from thermoplastics to laminated structures. This study focuses on a preliminary study on the processing and characterization of bio-based polyurethane (PU) adhesive/aluminum-laminated composites. Five different formulations of PU adhesives were prepared from five different formulations of polycaprolactone (PCL) polyols. The PCL polyols were synthesized by a ring opening polymerization of ɛ-caprolactone initiated by a blend of palm kernel oil polyesteramide (PPKO) and 1,6-hexanediol (HDO) with various weight ratios of PPKO:HDO (0:100, 25:75, 50:50, 75:25, and 100:0). The PCL polyols were reacted with a mixture of aromatic and cycloaliphatic diisocyanate. Physical and chemical analyses of PCL polyols such as viscosity, OH number, molecular weight, and proton nuclear magnetic resonance (¹H-NMR) were carried out. The swelling and mechanical testing were performed to explore the correlation between the structure of PU network and its properties. The adhesion strength of bio-based PU/aluminum-laminated composites was found to be influenced by the structure of the PU network system. The ratio of 75:25 (PPKO:HDO) was found to be the optimum based on the mechanical strength of laminated composites and the thermal stability of the PU adhesive.     

The physical and mechanical properties of polyurethanes from oleic acid polyols

Three different polyester polyols, with various oleic acid content, were used in the preparation of polyurethane (PUR) coatings. The polyols were designated as Alk28, Alk40, and Alk65, in which 28, 40, and 65 represent the percentage of oleic acid of the polyol formulations. These polyester polyols were reacted with aromatic diisocyanate [toluene diisocyanate (TDI)] to form PUR coatings. The acid value, hydroxyl value, molecular weight, and viscosity of the polyols have been determined. The reaction between the polyols and TDI was studied by Fourier Transform Infrared spectroscopy and X‐ray diffraction (XRD). The effects of varying NCO/OH ratio and oleic acid content of polyols on physical and mechanical properties of PUR films were studied. XRD results indicate that the samples are amorphous. PURs, made with Alk28, have the best mechanical properties followed by Alk40 and Alk65. The mechanical properties of the samples have increased as the NCO/OH ratio was increased from 1.2 to 1.6. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Gel permeation chromatography of polyethylene. I. Calibration

An accurate GPC calibration is essential if computer techniques are to be utilized in obtaining the molecular weight distribution and degree of long-chain branching from an intrinsic viscosity and GPC trace of a polymer. The use of the National Bureau of Standards Linear Polyethylene Standard Reference Material, SRM 1475, to calibrate GPC is described. Employing this calibration, the Mark–Houwink relationship for linear polyethylene in 1,2,4-trichlorobenzene was established utilizing narrow molecular weight fractions derived through fractionation of SRM 1475 and other polymers. This Mark–Houwink equation was subsequently employed for the evaluation of high molecular weight fractions which were then used to extend the GPC calibration to the high molecular weight region not covered by SRM 1475. An iterative technique was used to obtain coincidence of the measured intrinsic viscosity and the viscosity calculated from the GPC data. The accuracy of the GPC calibration was demonstrated by obtaining coincidence of the measured and calculated viscosity of high and low molecular weight polymers of both narrow and broad polydispersity.     

Use of gas-liquid chromatography in the analysis of rigid polyurethane foam polyols

Detailed characterization of the low molecular weight polyols used as intermediates in rigid polyurethane foam production has not been feasible to date. Gas-liquid chromatography of the trimethylsilyl ether derivatives of the polyols now offers a more complete picture of polyol composition, particularly with regard to the molecular weight distribution. The data may be interpreted on a semiquantitative basis. The study of processing variables in polyol manufacture, detection of impurities and analysis of unknown polyols or those based on mixed initiators may all be facilitated by use of this GLC technique.     

聚醚多元醇对单组分聚氨酯泡沫填缝胶性能的影响

研究了聚醚多元醇的官能度及相对分子质量对单组分聚氨酯泡沫填缝（密封）胶性能的影响。聚醚二醇和聚醚三醇复配使用，可制得综合性能良好的单组分聚氨酯泡沫胶体系。     

Structural Effects on the Adhesive Properties of Butadiene/Styrene Radial Teleblock Copolymers

The effects of butadiene/styrene ratio, monomer distribution, and molecular weight distribution and branching on the pressure sensitive adhesive properties of butadiene/ styrene radial teleblock copolymers are reported. Styrene content of polymers with varying structures shows a close relation with tack response, and styrene content and structure affect solution viscosity and shear adhesion. When part of the styrene is incorporated into the polybutadiene segment to yield a block progressively enriched in styrene (tapered block), solution viscosity and shear adhesion are reduced. When the butadiene segment is replaced by a block of randomly copolymerized butadiene and styrene, the polymers provide lower solution viscosities and shear adhesion but unchanged tack.

The molecular weight distribution of the radial teleblock polymers can vary from broad, highly branched compositions to narrow molecular weight distributions of almost Iinear polymers. The latter have relatively high solution viscosity and low shear adhesion, whereas the former polymers produce moderate solution viscosity but high shear adhesion. Tack is generally unaffected.