Structure-Property Relationships of Perfectly Alternating Polycarbonate-Polydimethylsiloxane Block Copolymers, Part II

1984 ◽  
Vol 57 (1) ◽  
pp. 184-202 ◽  
Author(s):  
S. H. Tang ◽  
E. A. Meinecke ◽  
J. S. Riffle ◽  
J. E. McGrath
Keyword(s):  
Molecular Weight ◽  
Tensile Strength ◽  
Block Copolymers ◽  
Dynamic Mechanical Properties ◽  
Block Length ◽  
Structure Property ◽  
Two Phase ◽  
K Value ◽  
Mechanical Coupling ◽  
Molecular Weights

Abstract The relationships between the properties and microstructures of two series of perfectly alternating bisphenol A-polycarbonate-polydimethylsiloxane block copolymers were studied. In the first series, the polycarbonate (PC) block length was kept constant while the block length of polydimethylsiloxane (PDMS) was varied. The tensile properties of these block copolymers were found to be a function of composition. Dynamic mechanical properties measured as a function of temperature revealed the two-phase nature of these materials. Transmission electron micrographs showed that all samples had a sponge-like morphology independent of composition. The rheological maximum viscosity for the sample containing PC and PDMS blocks of equal molecular weight and extrudate swells increased with PC content. Takayamagi's mechanical coupling model was used to predict the maximum loss tangent at the glass transition temperature of PDMS using the known properties of pure components. The predictions agreed fairly well with the experimental results. In a second series of block copolymers, the block molecular weights of both PC and PDMS were varied to keep the composition constant. The tensile strength of these samples was found to increase with block molecular weights, except for the sample having the highest block molecular weights. The lower tensile strength of this material was attributed to its lamellar type morphology. Cold crystallization of PDMS blocks was found for samples having high PDMS block molecular weight (greater than 8000 g/mole). The Tg of PC blocks followed the Fox-Flory equation with a higher K value than expected. The PDMS content in PC domains was calculated to range from 11% for material of low block molecular weights to about 1.3% for high block molecular weight material.

Synthesis of Cyclic Polysulfides and their Properties as Curing Agents

2004 ◽  
Vol 77 (2) ◽  
pp. 380-390
Author(s):  
Wonmun Choi ◽  
Tomoyuki Matsumura
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
Tensile Strength ◽  
High Molecular Weight ◽  
Mass Spectra ◽  
Elongation At Break ◽  
Molecular Weights ◽  
Aging Properties ◽  
Curing Agents ◽  
Polysulfide Polymer

Abstract The reactions of dichloroalkanes and sodium tetra-sulfide (Na2S4) were carried out in a mixture of water and toluene to produce corresponding cyclic polysulfides and polysulfide polymer. The low molecular weights of cyclic sulfides were obtained by the reaction at 90 °C, while the high molecular weight of polysulfide polymer was obtained by the reaction at 50 °C. GPC chromatograms and Mass spectra revealed that the structures of cyclic polysulfide were 1:1, 2:2, and 3:3 adducts of dichloroalkane and sodium tetra-sulfide. The mechanical properties of vulcanized NR at 148 °C with cyclic sulfides were similar to that with sulfur. However, both tensile strength and elongation at break of vulcanized NR at 170 °C with cyclic sulfides are much higher than that with sulfur. The aging properties of vulcanized NR at 148 °C or 170 °C with cyclic polysulfides indicate better stability.

Mechanical and Viscoelastic Characterization of Hyperbranched Polyisobutylenes

2002 ◽  
Vol 75 (5) ◽  
pp. 853-864 ◽  
Author(s):  
Judit E. Puskas ◽  
Christophe Paulo ◽  
Volker Altstädt
Keyword(s):  
Molecular Weight ◽  
Butyl Rubber ◽  
Structure Property ◽  
Carbocationic Polymerization ◽  
Molecular Weights ◽  
Structure Property Relationships ◽  
Molecular Weight Distributions ◽  
Weight Distributions ◽  
Living Carbocationic Polymerization

Abstract Structure-property relationships were investigated in hyperbranched polyisobutylenes, in comparison with commercial linear butyl rubber. The gel-free, soluble hyperbranched polyisobutylenes, synthesized by living carbocationic polymerization, had molecular weights, Mw≈400,000 to 1,000,000 g/mol, molecular weight distributions, MWD ≈1.2 to 2.6, and branching frequencies, BR ≈ 4 to 60. The mechanical and viscoelastic characterization of these polymers revealed interesting properties, including the characteristics of crosslinked rubbers.

Properties of Random and Block Copolymers of Butadiene and Styrene. III. Three Sequence Styrene-Butadiene-Styrene Block Polymers

1967 ◽  
Vol 40 (4) ◽  
pp. 1183-1199 ◽  
Author(s):  
C. W. Childers ◽  
G. Kraus
Keyword(s):  
Tensile Strength ◽  
Block Copolymers ◽  
Polymer Chains ◽  
Two Phase ◽  
Styrene Copolymers ◽  
Relaxation Measurements ◽  
Styrene Butadiene Styrene ◽  
Increasing Temperature ◽  
Styrene Butadiene ◽  
Butadiene Styrene

Abstract In butadiene styrene copolymers containing long block sequences chain segments associate with like segments to form a two phase structure. Properties of such polymers are dependent not only on composition and molecular weight but also on block sequence along the chain. Polymers containing two or more polystyrene blocks per molecule form networks and exhibit elastomeric properties in the uncured state resembling those of filler reinforced vulcanizates. This behavior is shown both by linear styrene-butadiene-styrene elastomers and multichain block copolymers branched in the polybutadiene blocks. A prominent loss tangent peak was observed around —40° C for the multichain polymers. Stress strain following prestretching and stress relaxation measurements indicate some shifting of polystyrene associations during stretching. Tensile strength is reduced by increasing temperature and addition of plasticizers. Reinforcement by polystyrene domains in vulcanized block copolymers is evident from tensile strength, dynamic modulus, and swelling measurements, but decreases with increased crosslinking. The number of styrene sequences in the primary molecules is less important after vulcanization as crosslinking destroys the individuality of the original polymer chains.

Rheological behaviour of block copolymers in the disordered state: effects of molecular weight and block length ratio

Polymer ◽  
1992 ◽  
Vol 33 (2) ◽  
pp. 294-305 ◽  
Author(s):  
Chang Dae Han ◽  
Deog Man Baek ◽  
Jin Kon Kim ◽  
Sung Gun Chu
Keyword(s):  
Molecular Weight ◽  
Block Copolymers ◽  
Rheological Behaviour ◽  
Length Ratio ◽  
Block Length

EPDM RUBBER PLASTICIZED WITH POLYMERIC SOYBEAN OIL OF DIFFERENT MOLECULAR WEIGHTS

2017 ◽  
Vol 90 (4) ◽  
pp. 667-682 ◽  
Author(s):  
Zoran S. Petrović ◽  
Jelena Milić ◽  
Mihail Ionescu ◽  
James R. Halladay
Keyword(s):  
Molecular Weight ◽  
Tensile Strength ◽  
Soybean Oil ◽  
Cross Linking ◽  
Tear Strength ◽  
Soybean Oils ◽  
Molecular Weights ◽  
Compression Set ◽  
Diene Rubber ◽  
Processing Aids

ABSTRACT Polymerization of soybean oil produces higher-viscosity liquids, which may serve as processing aids and plasticizers in certain rubbers as a replacement of petrochemical oils. Four polymerized soybean oils of different molecular weights showed good compatibility with ethylene–propylene–diene rubber (EPDM), but because of the presence of double bonds and copolymerization with EPDM, they decreased the cross-linking density when compared with paraffinic extender oil. As a consequence, polymeric soybean oils reduced tensile strength and modulus but increased elongation, tear strength, and compression set. Higher-molecular-weight plasticizers are expected to reduce sweating out of oils. Pure soybean oil was not completely compatible at the concentration tested, but it showed a strong plasticizing effect; dramatically lowered tensile strength, tear strength, and modulus; and increased elongation and compression set. No clear effect of molecular weight of polymerized soybean oils on properties was observed, but increasing the sulfur content was found to be beneficial. Using polymeric vegetable oils instead of petrochemical extenders in EPDM rubbers is economical and environmentally desirable, but the curing system requires optimization to accommodate loss of cross-linking density.

Steady Flow and Dynamic Viscosity of Branched Butadiene-Styrene Block Copolymers

1972 ◽  
Vol 45 (4) ◽  
pp. 1005-1014
Author(s):  
G. Kraus ◽  
F. E. Naylor ◽  
K. W. Rollmann
Keyword(s):  
Molecular Weight ◽  
Glass Transition ◽  
Block Copolymers ◽  
Steady Flow ◽  
Domain Structure ◽  
Viscoelastic Behavior ◽  
Significant Degree ◽  
Two Phase ◽  
Total Molecular Weight ◽  
Block Structures

Abstract Steady flow and dynamic viscosities were determined for symmetrical linear and star-branched block copolymers of butadiene and styrene above their upper (polystyrene) glass transition. Block structures examined were B-S-B, (B-S-)3, S-B-S, (S-B-)3 and (S-B-)4. At constant molecular weight and total styrene content viscosities were greater for polymers terminating in styrene blocks, irrespective of branching. Branching decreased the viscosity of either polybutadiene-terminated or polystyrene-terminated block polymers, compared at equal Mw. However, comparisons at equal block lengths showed that the length of the terminal blocks, not the total molecular weight, governs the viscoelastic behavior of these polymers to a surprisingly good approximation. This unusual result is rationalized in terms of the two-phase domain structure of these polymers, which persists to a significant degree in the melt. Below the glass transition of the polystyrene blocks the effects of branching were masked by differences in the morphology of the domain structure unrelated to branching.

Dynamic Mechanical Properties of Cross-Linked Rubbers. II. Effects of Crosslink Spacing and Initial Molecular Weight in Polybutadiene

1966 ◽  
Vol 39 (4) ◽  
pp. 905-914
Author(s):  
Etsuji Maekawa ◽  
Ralph G. Mancke ◽  
John D. Ferry
Keyword(s):  
Molecular Weight ◽  
Crosslink Density ◽  
Low Frequency ◽  
Dynamic Mechanical Properties ◽  
Cross Linking ◽  
Loss Mechanism ◽  
Low Frequencies ◽  
Molecular Weights ◽  
Monomeric Friction Coefficient ◽  
Lower Frequencies

Abstract The complex shear compliances of eight samples of polybutadiene crosslinked by cumyl peroxide and four samples crosslinked by sulfur have been measured over a frequency range from 0.2 to 2 cps at temperatures from − 6 to 45° C by a torsion pendulum. On four of the samples, measurements were extended by the Fitzgerald transducer from 45 to 600 cps at temperatures from − 71 to 55°. The vulcanizates had been prepared from polymers of two different molecular weights (180,000 and 510,000) with sharp molecular weight distribution; the physical crosslink density ranged from 0.57 to 2.68×10−4 mole/cm3, and the chemical crosslink density calculated following Kraus ranged from 0.22 to 1.49×10−4 mole/cm3. The mechanical data were all reduced to T0=298° K by shift factors calculated from the equation log aT=−3.64(T−T0)/(186.5+T−T0). In the transition zone of frequencies, the viscoelastic functions of the cumyl peroxide vulcanizates were closely similar, except for a shift toward lower frequencies with increasing crosslinking, corresponding to a small but unexpected increase in the monomeric friction coefficient. Cross-linking by sulfur caused a somewhat larger shift toward lower frequencies at a comparable crosslink density. In the rubbery zone, the sample with least cross-linking exhibited a substantial secondary loss mechanism at very low frequencies. The low-frequency losses are evident in all the samples, but their magnitude falls rapidly with increasing crosslink density as previously found for natural rubber. It also falls somewhat with increasing initial molecular weight, indicating a contribution from network strands with loose ends. The possible relation of the low-frequency losses to trapped entanglements is discussed.

Mechanical and Dynamic Mechanical Properties of Degradable Polyurethane Foams with PEG/PCL Mixed Soft Segments

2011 ◽  
Vol 183-185 ◽  
pp. 1611-1615 ◽  
Author(s):  
Jian Hua Wang ◽  
Shuen Liang ◽  
Yan Yan Wang ◽  
Chun Rong Tian ◽  
Xiu Li Zhao
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
Tensile Strength ◽  
Compressive Strain ◽  
Dynamic Mechanical Properties ◽  
Polyurethane Foams ◽  
Elongation At Break ◽  
Dynamic Mechanical ◽  
Soft Segments ◽  
And Storage

Polyurethane (PU) with mixed poly(ethylene glycol) / poly(ε-caprolactone) (PEG/PCL) soft segments is a representatively kind of degradable polyurethane material. Polyurethane foams (PUF) with mixed PEG/PCL soft segments were synthesized by using one pot method, and their mechanical and dynamic mechanical properties were investigated. Influences of PEG/PCL weight ratio and molecular weight of soft segments on PUF's mechanical and dynamic mechanical properties were studied. The results showed that: with increasing content of PCL, PUF's tensile strength, elongation at break, stress at certain tensile/compressive strain and storage modulus increased gradually; with increasing molecular weight of soft segment, PUF's elongation at break increased, but tensile strength, stress at certain tensile/compressive strain and storage modulus all decreased accordingly; glass transition temperature (Tg) of PUF with various soft segments decreased according to the following sequence: PEG-400, PCL-210N, PEG-1000 and PTMG1000; loss factor of PUF with PEG/PCL mixed soft segments was higher than that of PUF with individual PEG or PCL soft segments.

Effect of Molecular Weight on Dynamic Mechanical Properties of SKD cis-1,4-Butadiene Rubber

1967 ◽  
Vol 40 (2) ◽  
pp. 517-521
Author(s):  
A. I. Marei ◽  
E. A. Sidorovich
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
Average Molecular Weight ◽  
Dynamic Mechanical Properties ◽  
Considerable Effect ◽  
Butadiene Rubber ◽  
Dynamic Mechanical ◽  
Temperature Range ◽  
Molecular Weights ◽  
Dynamic Mechanical Behavior

Abstract In the high-elastic temperature range the molecular weight has a considerable effect on the dynamic mechanical properties of linear (uncrosslinked) SKD cis-1, 4-butadiene rubber. In this temperature range an unequivocal correlation exists between the rebound resilience at a given temperature and the viscosity average molecular weight, and the determination of the resilience can therefore be recommended as a rapid method of finding the molecular weight of SKD. A similarity is found in the dynamic mechanical behavior of rubbers of different molecular weights in the high-elastic temperature range. In the low-temperature range an increase in the molecular weight of crystalline polymers of SKD is accompanied by an impairment of their elastic properties.

scholarly journals Effect of Different Molecular Weight and Concentration of Polyethylene Glycol (PEG) on Tensile and Morphology of Sago Starch Film

2021 ◽  
Vol 16 ◽  
pp. 1-10
Author(s):  
Norzita Yacob
Keyword(s):  
Molecular Weight ◽  
Tensile Strength ◽  
Polyethylene Glycol ◽  
Tensile Stress ◽  
Sago Starch ◽  
Elongation At Break ◽  
Molecular Weights ◽  
Peg 4000 ◽  
Starch Films ◽  
Ftir Technique

Sago starch is a seasonal based plantation and widely found in Asia country. Its application mainly in cooking such as biscuits and as a thickener in jellies. To further utilize its application, bioplastic from sago starch was developed. In this study, sago starch films were prepared through a blending and casting method using polyethylene glycol (PEG) as a plasticizer by varying its molecular weights and concentrations. The interaction between starch and PEG in the blend was studied using FTIR technique. The effect on transparency, tensile stress, Young’s modulus as well as elongation percentages of the films was also examined. The results suggested that the addition of low molecular weight PEG (400 g.mol-1) increased the tensile stress of sago films from 33.51 MPa up to 39.11 MPa. Nevertheless, incorporation of high molecular weight of PEG (4000 g.mol-1) decreased the tensile strength of the film. Tensile strength and elongation at break of sago films increased with increasing of PEG concentration up to 2% and decreased with further increased of PEG content. Results indicated that there was a miscibility between these two components.

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