Ultimate Tensile Properties of Segmented Polyurethane Elastomers: Factors Leading to Reduced Properties for Polyurethanes Based on Nonpolar Soft Segments

1986 ◽  
Vol 59 (3) ◽  
pp. 405-431 ◽  
Author(s):  
T. A. Speckhard ◽  
S. L. Cooper
Keyword(s):  
Molecular Weight ◽  
Glass Transition ◽  
Phase Separation ◽  
Block Copolymers ◽  
Tensile Properties ◽  
Soft Segment ◽  
Low Molecular Weight ◽  
Polyurethane Elastomers ◽  
Soft Segments ◽  
Available Information

Abstract Factors that could explain the lower tensile properties of nonpolar soft-segment-based polyurethane block copolymers relative to those of conventional polyether or polyester polyurethanes have been examined. Many of the materials studied in the literature have suffered from the use of soft segments with poor functionality, which has led to low molecular weight, network defects, and an unfavorable amount of crosslinking. Additionally, most of the materials have been based on soft segments whose molecular weight appears to be too high to obtain optimum properties. Polyurethanes based on nonpolar soft segments are also likely to suffer from premature phase separation during polymerization leading to low molecular weight and compositional heterogeneity, especially if the reaction is done in bulk. The lower soft-segment glass-transition temperature of, in particular, the polydimethylsiloxane polyurethanes can also contribute to their lower tensile properties at room temperature. However, if differences in the soft-segment glass-transition temperatures are accounted for by comparing samples at equivalent values of T−Tg and other parameters are optimized, it appears that only a lack of soft-segment crystallizability under strain and possibly an excessively high degree of phase separation are inherently limiting the tensile properties of nonpolar soft-segment-based polyurethane block copolymers. The limited amount of available information concerning the effects of many of these factors suggests a need for additional work in this area.

The Effect of Triacetin on the Plasticization Efficiency and Tensile Properties of Polyvinyl Chloride/di-2-Ethyl Hexyl Phthalate/Triacetin Compounds

2016 ◽  
Vol 1133 ◽  
pp. 206-210 ◽  
Author(s):  
Arjulizan Rusli ◽  
Nur Farhana Asul Kahar
Keyword(s):  
Molecular Weight ◽  
Tensile Strength ◽  
Glass Transition ◽  
Tensile Properties ◽  
Polyvinyl Chloride ◽  
Chemical Structure ◽  
Low Molecular Weight ◽  
Migration Ability ◽  
Elongation At Break ◽  
Before And After

The use of triacetin as an alternative plasticizer to polyvinyl chloride (PVC) was studied in term of plasticizer efficiency and tensile properties before and after ageing. The efficiency of plasticizers was evaluated based on the glass transition temperature (Tg) and the hardness value of the compounds. The Tg and hardness of all PVC/DEHP/Triacetin compounds are lower than PVC/50DEHP and PVC/50Triacetin compounds indicating synergistic plasticisation effect between both DEHP and Triacetin within the PVC compounds. The low molecular weight and chemical structure of triacetin are believed to contribute to the highest tensile strength, elongation at break and modulus of the PVC/triacetin compared with PVC/DEHP and PVC/DEHP/triacetin compounds. However, the migration ability of the triacetin plasticizer is believed to result in the biggest changes of the tensile properties of PVC compounds plasticized with triacetin before and after ageing.

scholarly journals Impact of Macrodiols on the Morphological Behavior of H12MDI/HDO-Based Polyurethane Elastomer

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2060
Author(s):  
Shazia Naheed ◽  
Mohammad Zuber ◽  
Mahwish Salman ◽  
Nasir Rasool ◽  
Zumaira Siddique ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Contact Angle ◽  
Chain Length ◽  
Microphase Separation ◽  
Soft Segment ◽  
Group Identification ◽  
Degree Of Crystallinity ◽  
Polyurethane Elastomers ◽  
Hard Segments ◽  
Morphological Behavior

In this study, we evaluated the morphological behavior of polyurethane elastomers (PUEs) by modifying the soft segment chain length. This was achieved by increasing the soft segment molecular weight (Mn = 400–4000 gmol−1). In this regard, polycaprolactone diol (PCL) was selected as the soft segment, and 4,4′-cyclohexamethylene diisocyanate (H12MDI) and 1,6-hexanediol (HDO) were chosen as the hard segments. The films were prepared by curing polymer on Teflon surfaces. Fourier transform infrared spectroscopy (FTIR) was utilized for functional group identification in the prepared elastomers. FTIR peaks indicated the disappearance of −NCO and −OH groups and the formation of urethane (NHCOO) groups. The morphological behavior of the synthesized polymer samples was also elucidated using scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The AFM and SEM results indicated that the extent of microphase separation was enhanced by an increase in the molecular weight of PCL. The phase separation and degree of crystallinity of the soft and hard segments were described using X-ray diffraction (XRD). It was observed that the degree of crystallinity of the synthesized polymers increased with an increase in the soft segment’s chain length. To evaluate hydrophilicity/hydrophobicity, the contact angle was measured. A gradual increase in the contact angle with distilled water and diiodomethane (38.6°–54.9°) test liquids was observed. Moreover, the decrease in surface energy (46.95–24.45 mN/m) was also found to be inconsistent by increasing the molecular weight of polyols.

Stereo-chemical contributions to the glass transition and liquid–liquid phase separation in high molecular weight poly(N-vinyl carbazole)

RSC Advances ◽  
2016 ◽  
Vol 6 (35) ◽  
pp. 29326-29333 ◽  
Author(s):  
Abdul G. Al Lafi ◽  
James N. Hay
Keyword(s):  
Molecular Weight ◽  
Glass Transition ◽  
Phase Separation ◽  
Liquid Phase ◽  
High Molecular Weight ◽  
Structural Properties ◽  
Thermal History ◽  
Liquid Phase Separation ◽  
High Molecular Weight Poly ◽  
Liquid Liquid Phase Separation

Thermal history and purification effects on the structural properties of PVK were investigated. Liquid–liquid phase separation is suggested to occur by separation of isotactic rich segments from a matrix which is predominantly atactic.

Effect of Block Molecular Weight on the Mechanical Properties of PA1010-b-PEG Segmented Block Copolymers

2012 ◽  
Vol 512-515 ◽  
pp. 2127-2130
Author(s):  
Li Huo ◽  
Cai Xia Dong
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
Block Copolymers ◽  
Microphase Separation ◽  
Soft Segment ◽  
Mechanical Measurements ◽  
Wide Range ◽  
Hard Block ◽  
Higher Temperature ◽  
Hard Segments

The mechanical properties were investigated of a series of PA-PEG thermalplastic elastomer based on PA1010 and polytetramethylene glycol (PEG) with varying hard and soft segment content. Dynamic mechanical measurements of these polymers have carried out over a wide range of temperatures. The block copolymers exhibit three peaks, designated as α, β and γ in the tanδ-temperature curve. The α transition shifts to higher temperature with increasing hard block molecular weight. However, at a constant hard molecular weight, the α transition shifts to higher temperature and the damping increases on increasing the soft segment molecular weight. DMA results show that the block copolymers exhibit a microphase separation structure and both soft and hard segments were found to be crystallizable. The degree of phase separation increases with increasing hard block molecular weight.

8 Final Report on the Safety Assessment of Polyquaternium-11

1983 ◽  
Vol 2 (5) ◽  
pp. 161-178 ◽  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Skin Irritation ◽  
Low Molecular Weight ◽  
Final Report ◽  
Dermal Toxicity ◽  
Molecular Weight Polymer ◽  
Patch Tests ◽  
Skin Patch ◽  
Available Information

Polyquaternium-11 is a quaternized copolymer of vinylpyrrolidone and di-methylamine ethylmethacrylate, and is used at concentrations up to 50% in a variety of hair care preparations. The acute oral LD50 in test animals of high molecular weight Polyqua-ternium-11 is estimated to be greater than 12.8 g/kg; the LD50 for the low molecular weight polymer is calculated to be 6.2 g/kg. At concentrations of up to 50% in water, the raw ingredient produced no signs of skin or eye irritation. There was no evidence of dermal toxicity in subchronic tests nor in a maximization test for sensitization. In clinical studies, 1 of 19 subjects showed slight skin irritation after a 24-hour single insult skin patch with 9.5% Polyquaternium-11 in water. Repeated insult patch tests at concentrations up to 50% produced no instances of skin sensitization and only isolated instances of transient skin irritation. Clinical photoreactivity studies on both low and high molecular weight polymers showed no evidence of phototoxicity or photoallergenicity. From the available information, it is concluded that Polyquaternium-11 is safe as a cosmetic ingredient in the present practices of use.

Glass Transition and Ultrasonic Relaxation in Polystyrene

1996 ◽  
Vol 455 ◽  
Author(s):  
A. Sahnoune ◽  
L. Piché
Keyword(s):  
Molecular Weight ◽  
Relaxation Time ◽  
Glass Transition ◽  
Low Temperatures ◽  
Relaxation Modulus ◽  
Low Molecular Weight ◽  
Relaxation Model ◽  
Fragility Index ◽  
Molecular Weights ◽  
Ultrasonic Relaxation

ABSTRACTWe present measurements of the glass transition and the ultrasonic relaxation modulus in a series of monodisperse polystyrenes. The temperature dependence of the modulus was analyzed using Havriliak-Negami relaxation model (HN) and Vogel-Tammann-Fulcher equation (VTF) for the relaxation time. The results allowed us to determine the fragility index, m, which decreases with increasing molecular weight, Mn. Furthermore, the relaxation time was found to saturate at high molecular weights and varies as Mnp, in the low molecular weight region. The exponent is p≈2 at high temperatures and p ≈ 7 at low temperatures close to Tg.

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