Thermomechanical investigation of hydroxyl-terminated polybutadiene-based linear polyurethane elastomers

The present work describes the trend of linear polyurethane elastomers for its thermal and mechanical behavior. The linear polyurethane elastomers have been synthesized in two different series by changing the composition of the polymers. Both series have common macrodiol of hydroxyl-terminated polybutadiene and butanediol while they vary in the presence of diisocyanate. One of the series, contain an aromatic diisocyanate, toluene diisocyanate (TDI), and the other consist of 1,6-hexamethylene diisocyanate (HDI) as an aliphatic diisocyanate. For linear structure, ratio of OH and NCO group has been maintained 1.0. The hydrogen bonding index is determined from Fourier transform infrared to calculate the extent of interchain hydrogen bonding which manifest the microphase separation. Young's modulus (5.79 MPa) and tensile strength (1.14 MPa) are recorded for HDI-derived elastomers, while Young's modulus varies from 1.14 to 1.63 MPa for TDI-based elastomers which also resulted in higher thermal stability. Thermogravimetric curves exhibit two-step degradation with the stability of 300 °C. HDI-based polyurethane elastomers show better tensile properties and HDI but poor thermal stability as compared to TDI-based elastomers. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47289.     

Characterization of functionally terminated polybutadienes of low molecular weight

A difunctional hydroxyl-terminated polybutadiene (sample A) was characterized by light scattering (LS), vapor pressure osmometry (VPO), and gel permeation chromatography (GPC). Sample A was then esterified, and the product (sample B) was also characterized. Light-scattering measurements were carried out in different solvents (some were theta solvents for polybutadiene), and the results were corrected for anisotropy. Values of M_n (3100) and M_w (8000) determined respectively by VPO and LS for samples A and B were similar to those computed by GPC using two sets of columns of different resolution. The value of 2.3 found for the polydispersity index M_w/M_n is higher than the value which is usually reported by other workers (ca. 1.3 to 1.7) for functionally terminated polybutadienes.     

助剂对丁羟聚氨酯弹性体力学性能的影响

通过单向拉伸试验、交联密度和凝胶分数测试等手段,研究了MAPO、TEBA、防老剂H对丁羟(HTPB)聚氨酯弹性体力学性能的影响。结果表明:在不含催化剂的条件下MAPO与TDI完全能够发生反应;由于MAPO和HTPB竞争与TDI反应,进入弹性体交联网络结构中,可能破坏了网络结构的完整性,从而影响了弹性体的单向拉伸性能;TEBA与TDI反应进入弹性体网络结构中,增加了网络链的柔顺性;防老剂H对丁羟弹性体力学性能的影响是扩链作用、改变HTPB的反应分数和增加物理交联点3种作用的综合结果。     

Thermoplastic polyurethane elastomers based on polycarbonate diols with different soft segment molecular weight and chemical structure: Mechanical and thermal properties

A series of thermoplastic polyurethane elastomers based on polycarbonate diol, 4,4′‐diphenylmethane diisocyanate and 1,4‐butanediol was synthesized in bulk by two‐step polymerization varying polycarbonate diol soft segment molecular weight and chemical structure, and also hard segment content, and their effects on the thermal and mechanical properties were investigated. Dynamic mechanical analysis termogravimetric analysis, differential scanning calorimetry, Fourier transform infrared‐attenuated total reflection spectroscopy and mechanical tests were employed to characterize the polyurethanes. Thermal and mechanical properties are discussed from the viewpoint of microphase domain separation of hard and soft segments. On one hand, an increase in soft segment length, and on the other hand an increase in the hard segment content, i.e., hard segment molecular weight, was accompanied by an increase in the microphase separation degree, hard domain order and crystallinity, and stiffness. In phase separated systems more developed reinforcing hard domain structure is observed. These hard segment structures, in addition to the elastic nature of soft segment, provide enough physical crosslink sites to have elastomeric behavior. POLYM. ENG. SCI., 2008. © 2007 Society of Plastics Engineers     

具有交联结构的脂肪族聚氨酯弹性体的性能

以三羟甲基丙烷(TMP)为交联剂制备了具有不同交联密度的脂肪族聚氨酯弹性体,考察了交联密度对弹性体物理机械性能的影响。结果表明,聚氨酯弹性体的交联密度随着TMP的含量线性增加。聚氨酯弹性体的弹性模量、邵尔A硬度和100%定伸应力均随着交联密度的增加而明显提高。由于硬段相有序结构的破坏,拉伸强度则显示出先增大后减小的趋势。     

磁场存在下制备的聚氨酯弹性体的形态

在磁场强度分别为１．５Ｔ,１．０Ｔ及不存在磁场的情况下合成了硬段质量分数均为５０％的聚氨酯（ＰＵ）弹性体,用ＷＡＸＤ和ＳＥＭ表征了它们的形态。结果表明,磁场存在下制备的ＰＵ的结晶度明显增大;磁场强度越强,ＰＵ的结晶度越大。     

邻接交联型端羟基液体丁腈橡胶基聚氨酯弹性体的制备与性能

以端羟基液体丁腈橡胶、二苯基甲烷二异氰酸酯及扩链剂1,4 -丁二醇为原料,加入自由基引发剂2,5-二甲基-2,5-双(过氧化叔丁基)己烷和交联助剂三烯丙基异三聚氰酸酯( TAIC),制备了邻接交联型聚氨酯弹性体(PUE),考察了 TAIC的用量对PUE力学性能的影响,并对PUE的热性能进行了研究.结果表明,随着TA I...     

窄分布低分子质量端羟基聚四氢呋喃的合成与研究

以三氟化硼乙醚配合物(BF3·OEt2)为催化剂,环氧丙烷(PO)为起始剂,二氯甲烷(CH2 Cl2)作溶剂,通过四氢呋喃的阳离子开环聚合合成了窄分子质量分布(Mw/Mn＜1.3)的端羟基聚四氧呋喃(PTHF).研究了三氟化硼乙醚配合物用量、溶剂用量、起始剂用量、反应时间对PTHF分子质量(Mn)及其分布(Mw/Mn)...     

Effects of number-average molecular weight of liquid hydroxyl-terminated polybutadiene on physical properties of the elastomer

The relationship between the molecular weight of liquid hydroxyl-terminated polybutadiene (HTPB) and the physical properties of the elastomers were investigated. HTPB having various molecular weights were cured with 4,4′-diphenylmethane diisocyanate (MDI) by the one-shot method and the physical properties of these elastomers obtained were measured. The tensile strenght, modulus, tear resistance, and the hardness decreased with increase in the molecular weight of HTPB, and this phenomenon was remarkable in the low molecular weight HTPB (below about 3000). On the other hand, the ultimate elongation increased linearly with increase in the molecular weight of HTPB. The effects of incorporating a short-chain diol, N,N-bis(2-hydroxypropyl)aniline, on the physical properties on the elastomers are also discussed.     

Mechanical and thermal properties of polyurethane elastomers based on hydroxyl‐terminated polybutadienes and biopitch

Biopitch is a renewable source of polyol obtained from Eucalyptus tar distillation, which was studied as an active component of polyurethane (PU). The polymerization occurred in one step, with a mixture of biopitch and hydroxyl‐terminated polybutadiene polyols reacted with 4‐4′‐diphenyl methane diisocyanate in the presence of dibutyltin dilaurate. Solid‐state ¹³C‐NMR, IR spectroscopy, elemental analysis, and thermal analysis [thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC)] were used to characterize the biopitch. The biopitch sample showed an aromatic and oxygenated structure with great thermal stability at high temperatures. Multiphasic PUs were synthesized and characterized by IR spectroscopy (attenuated total reflectance), elemental analysis, thermal analysis (TGA and DSC), mechanical assays (tensile strength, elongation at break, toughness, hardness, and resilience), and water absorption resistance (ASTM D 570‐81). In a comparative study of the synthesized elastomers, biopitch content increased tensile strength and hardness and decreased thermal stability, elongation at break, and water absorption. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 759–766, 2003     

Polyurethane elastomers based on molecular weight advanced poly(ethylene ether carbonate) polyols. III. Effects of diisocyanate modified diols

A series of diisocyanate-modified, molecular weight advanced poly(ethylene ether carbonate) diols has been prepared, characterized, and formulated into polyurethane elastomers using a prepolymer process. Properties were compared to a polyurethane elastomer control in which the only variable was the diisocyanate modification. The diisocyanate modification produces polymers with increased modulus (445–730% at 25°C), improved tensile strength and hardness properties and reduced (improved) coefficients of linear thermal expansion, while still passing the notched Izod impact test. The tensile strength at break increases with increasing number of urethane moieties in the soft segment and the elongation at break also increases. The plaques studied appear to have a three-phase morphology—a soft segment continuous phase containing amorphous hard segment, an amorphous hard segment phase plasticized by about 11% of the soft segment material, and a crystalline hard segment. The polymers based on the diisocyanate modified polyols are significantly more phase mixed than the control due to the increased amount of hard segment-soft segment interactions taking place. The improved properties of the polymers made with the modified polyols are due to their higher hydrogen bonding protential which gives more physically crosslinked polymers.     

具有超支化结构的脂肪族聚氨酯弹性体的制备及其物理机械性能

采用预聚体两步合成法制备了含超支化结构（HBS）的脂肪族聚酯型和聚醚型聚氨酯（PU）弹性体。研究结果表明,引入约1%的端羟基超支化聚酯后,PU的物理机械性能显著提高。与无HBS的PU相比,聚酯型PU的拉伸强度提高了18.2倍。     

低相对分子质量聚异丁烯热降解制备遥爪聚异丁烯

高温时将LMPIB[低Mn(数均相对分子质量)聚异丁烯]热降解,用黏数测定产物的Mn,用碘量法测定产物的双键含量,用红外光谱(FT-IR)法和核磁共振碳谱(13C-NMR)法分析产物的分子结构,并研究了反应条件对产物双键官能度的影响。结果表明:当温度≥285℃时,LMPIB降解并生成了不饱和β-末端双键,提高了LMPIB的双键官能度;经315℃反应1.00 h后,产物的双键官能度达到1.57,n(末端α-双键)∶n(末端β-双键)=1∶3,并得到含α-、β-末端双键的遥爪齐聚物与含β-末端双键的齐聚物的混合物,n(遥爪齐聚物)∶n(单官能度齐聚物)≈1∶2。     

Effects of the molecular weight on the properties of thermoplastics prepared from soy protein isolate

Commercial soy protein isolate (SPI) was fractionated into four fractions by an acidifying method from pH 5.7 to 4.5 with 2M HCl. A mixture of SPI with glycerin (50 g/100 g of dry SPI) was compression‐molded to obtain thermoplastic sheets. The weight‐average molecular weight (M_w) of the fractions, the structure, and the mechanical properties of the thermoplastic SPI sheets were investigated with light scattering, IR spectroscopy, wide X‐ray diffraction patterns, differential scanning calorimetry, ultraviolet spectroscopy, scanning electron microscopy, and tensile testing. After heating compression, the SPI sheets were transparent and exhibited a smooth and homogeneous structure. Moreover, the crystallinity degree of the thermoplastic SPI was obviously higher than that of the premix before compression because of the formation of intermolecular hydrogen bonding. The M_w's of the fractions were 1.17 × 10⁵ to 3.21 × 10⁵, and they increased with increasing pH value in fractionation. The mechanical properties and water resistance (R) of the SPI sheets increased with increasing M_w of the SPI fractions. The tensile strength and breaking elongation of the SPI sheets with an M_w value of 3.21 ×10⁵ were 5.7 MPa and 135%, respectively, and the R value was 0.54 after immersion in water for 15 days. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3373–3380, 2001     

端羟基聚丙烯酸酯分子量对PUA性能的影响

异佛尔酮二异氰酸酯(IPDI)、聚己内酯二醇(PCL)为主要原料合成聚氨酯预聚体,甲基丙烯酸甲酯和丙烯酸丁酯合成端羟基共聚物,两者共聚并在水中分散,得到丙烯酸酯改性水性聚氨酯(PUA)。PUA乳液形貌表征结果表明,当聚丙烯酸酯数均分子量达到9 041时,复合乳液的稳定性变差;复合乳液平均粒径随聚丙烯酸酯(PA)分子量增大而增加,但都小于150 nm,并呈现典型的核壳结构。FTIR测试表明,随着PA链段分子量增大,其氢键相互作用相对减弱。DSC测试显示在PA分子量较低时,PA和PU链段是相容的。TG和拉伸测试结果显示,PUA的热稳定性及力学性能都得到明显改善。     

聚碳酸酯二醇/蓖麻油基聚氨酯(脲)弹性体的制备及性能

以蓖麻油和聚碳酸酯二醇(PCDL)为共混软段,分别以1,4-丁二醇(BDO)和3,5-二甲硫基-2,4-二胺基甲苯(DMTDA)为扩链剂,用预聚体法合成出一系列聚氨酯(PU)和聚氨酯脲(PUU)弹性体,考察了异氰酸基(NCO)含量和PCDL用量对弹性体力学性能的影响,并对弹性体的热性能进行了分析。结果表明,随着预聚体中NCO含量的增加,PU、PUU弹性体的硬度和强度逐渐上升,当NCO质量分数为8%时,弹性体的拉伸强度最高,而扯断伸长率呈单调下降趋势;随着PCDL用量的增加,弹性体的拉伸强度先升高后下降,扯断伸长率和永久变形逐渐增加;用DMTDA为扩链剂制备的PUU比用BDO制备的PU具有更高的拉伸强度和撕裂强度;PCDL/蓖麻油基PUU的耐热性能优于纯蓖麻油基PUU,PUU的耐热性优于PU。     

Absorption of low molecular weight solutes into polyurethane in supercritical carbon dioxide

Absorption of a series of low molecular weight solutes into polyurethane was investigated in supercritical carbon dioxide with different conditions. The effect on the amount of solutes absorbed in polyurethane due to these factors such as pressure, temperature, absorption time, decompression time, the character of solutes, and the amount of cosolvent was examined by a gravimetric method. The absorption mechanism was discussed. The desorption of solutes in polyurethane showed a dependence on the logarithm of time. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3162–3168, 2000     

Influence of molecular weight on the thermal and mechanical properties of polyurethane elastomers based on 4,4′-diisocyanato dicyclohexylmethane

Two series of segmented polyurethane elastomers based on 4,4′-diisocyanato dicyclohexylmethane were investigated with respect to their thermal properties and deformation behavior. We used a crystallizable soft segment, 1,4-poly(tetramethylene glycol), for one series and a noncrystallizable soft segment, 1,2-poly(propylene glycol), for the other. Both systems exhibited mechanical self-reinforcement that depended strongly on the deformation rate. We propose a mechanism for the observed stress/strain behavior in terms of two competing processes: (1) the buildup of orientation caused by deformation and (2) the loss of orientation caused by plastic slippage and segmental relaxation during deformation. The kinetics of these processes depend stronly on the deformation rate and overall molecular weight.