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236839923

铁杆木虫 (正式写手)
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ksq887: 金币+2, thanks for sharing~ 2022-07-01 14:00:11
on Friday, June 24th, 2022,
In general, tie molecular <molecules are>is considered to pay an important role in the mechanical properties of crystalline polymers under a large strain. distributions of the concentration and the orientation of tie molecules <in a whole polymer>is<are> particularly interesting in a case of the samples which have a wide structure distribution like LLDPE. <then at first,>tie molecule ratio of SGEF fraction can be<was> calculated following the method by Huang and Brown. the basic idea for the calculation is as follows,.  the molecules which has end to end distance in the melt equal or greater than the distance between adjoining lamellar crystals will probably make a tie molecular. in the case that end to end distance is less than the amorphous thickness region between lamella, the tie molecular will never be formed. the probability of a given end to end distance, r, of a random coil is given by,
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十四万人齐解甲，竟无一个是男儿
31楼2022-06-24 08:11:51
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236839923

铁杆木虫 (正式写手)
★ ★
ksq887: 金币+2, good job 2022-07-01 14:00:03
on Monday, June 27th, 2022
the probability of tie molecules of mono-disperse polymer is given by equation 3. where L is the<a> critical distance and P was selected as A+B(A, lamella thickness, B the thickness of amorphous phase).  the probability <was then>was calculated for the cross fractions of the samples. .  the crystallinity, the degree of SCB and the melting temperature of the samples of B-10 were described previously.  Le of the samples were <was>estimated from  Thomson-Gibbs equation<equ. 4>. and La was also calculated from equ.5 by assuming a two phase model <for PE>in solid state, here, JE is the surface free energy, A , the heat of fusion, and Tm , the equilibrium melting temperature of PE<414K>. the densities of the crystalline<P c> and amorphous<Pa> phases are <were>taken to be 1 and 0.85 g/cm3, respectively. by varing only N in equ. 2 into small value, the probabilities of <for >other factions less than 10*104 were estimated to understand the tendency of molecular weight effect . though strictly speaking, the experimental data of Xc and Tm are necessary for each molecular weight because <the dependence of >these values on the SCB would be affected more or less by molecular weight.
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十四万人齐解甲，竟无一个是男儿
32楼2022-06-27 09:52:51
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236839923

铁杆木虫 (正式写手)
★ ★
ksq887: 金币+2, good job 2022-07-01 13:59:51
on Tuesday, June 28th, 2022
The calculated probability was exhibited finally  as a function of crystallinity(Figure 11). the tie molecule fraction (exactly speaking the fraction of molecules having the probability of being a tie molecule) shows a convex type dependence on crystallinity and it decreases steeply in the region of high crystallinity(Xc>70% for molecular weight about A). Further, tie molecules becomes substantial (-10%) for the molecules having molecular weight above A and the crystallinity of 40-50%.
As for the orientation of tie molecules in drawn state, it is not <so>easy still now to evaluate quantitatively.  however IR dichroism is one of the useful methods to estimate them from the structure changes in the amorphous region with drawing samples. the authors studied on the orientational and conformational changes with drawing various ethylene-butene-1 copolymer <of wide range of the crystallinity (XC=0-85%)> using IR dichroism, and found that those changes of amorphous  CH2 sequences in trans conformation which is< are> supposed to be intimately related to tie molecules possessed a considerably dependence on the crystallinity.  the Orientation function and relative concentration of sequence increased with increasing crystallinity, reached a maximum at Xc=60%, and then decreased with the further increase of the crystallinity.
Taking the result into consideration, <the degree of > tie moleuclar orientation of the SGEF fractions in drawn state would be significantly heterogeneous because the fractions contains the components of a wide variety of the crystallinity.
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十四万人齐解甲，竟无一个是男儿
33楼2022-06-28 10:32:50
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236839923

铁杆木虫 (正式写手)
★ ★
ksq887: 金币+2, thanks for sharing~ 2022-07-01 13:59:43
on Wednesday, June 29th, 2022,
it is reasonable to consider how many tie molecules of the same <degree of >orientation  exist in <a>drawn state,  regardless of <being>intrafibriller or interfibriller, strongly influences the mechanical strength of the sample. considering the <remarkable >crystallinity dependences described above, the distributions of  <both>the concentration and orientation of tie molecules of the SGEF fraction would be wide because of a wide distribution of the crystallinity. Particularly,  intermediate crystalline fractions <components >possess much more tie molecules than the high crystalline components and the low crystalline components. Therefore<consequently>  homogeneity of<the> crystallinity and <the >lamella thickness should pay a key role to increase the<actually > efficient tie molecules. Since DSC index indicates the relative concentration of the components having an intermediate crystallinity, the SGEF fractions of large DSC index is thus considered to contain much more efficient tie molecules in the deformed state than that of smaller DSC index, and therefore exhibit a higher mechanical strength as shown in Figures, 7,8./
Finally, it is interesting to note that the result of calculation for the molecular weight dependence of tie molecules concentration seems to correspond to the result of  mechanical test for SGEF fractions. i.e., fractions of molecular weight less than a is extremely brittle, fractions of molecular weight above B exhibited elongation with stress increase, and the tensile strength increase abruptly  from this molecular wight range.
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十四万人齐解甲，竟无一个是男儿
34楼2022-06-29 08:57:41
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236839923

铁杆木虫 (正式写手)
★ ★
ksq887: 金币+2, thanks for sharing~ 2022-07-01 13:59:33
on Friday,  July 1st, 2022
impact polypropylene copolymers can<may> be produced in a two-reactor system to yield a blend of homopolypropylene <homopolymer>with <an >ethylene-propylene rubber(EPR). the polypropylene homopolymer, which is itself brittle and has low impact strength, is markedly toughened by the presence of <the>EPR.  the rubber-like EPR exists as a phase-separated discrete particle in a continued matrix of <hard phase>. the molecular structure analysis of the resulting blends<complex mixuture> is a formidable task.
the purpose of this paper is to describe a preparative and an analytical temperature-raising elution technique as the primary tools to separate and characterize a commercial impact copolymer. these techniques permit the isolation and subsequent characterization <of the components>of the impact copolymersby ancillary techniques, primarily C13 nuclear magnetic resonance. these techniques were applied to the structure analysis of a commercial impact <grade>polypropylene with a melt flow rate of 6. It was found that impact copolymer was composed of about 75%<of> isotactic polypropylene, about 17% <of> highly non-crystalline EPR and about 8%<of>  semicrystalline ethylene-propylene copolymers. a major component of the semicrystalline EPR was ethylene-rich copolymer containing <between>0 and 8% of  propylene comonomer.
the separate characterization of the components of impact compolymer gives insight into chemical synthesis process used to produce these copolymers. furether, it permits one to gain a better understanding of the location and function of <each of >the components of the complex mixture.
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十四万人齐解甲，竟无一个是男儿
35楼2022-07-01 08:43:12
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236839923

铁杆木虫 (正式写手)
★ ★
ksq887: 金币+2, good job 2022-07-14 16:38:04
on Monday, July 4th, 2022
commercial isotactic polypropylene homopolymer is limited in its applications by  its<relatively>low impact strength and high brittleness temperature, the properties of PP can be greatly extended by blending with a minor fraction of <a>rubber-like material.  this is routinely done commercially by synthesizing reactor blending of isotactic PP and ethylene-propylene rubbers(EPR) in situ. these blends of isotactic PP and EPR are wildly known as impact PP and dominate a large fraction of PP market. EPR acts as a toughener for brittle and low impact strength isotactic PP <matrix> . It is well known that the addition of <a>low-Tg rubber-like material into <a>high Tg hard polymer material may result in dramatical improvement <in the toughness o>of the hard polymer.
<the >rubber-like phase is know to act <exist >as <a>phase-separated discrete particle in a continued<continuous> matrix of hard phase . the rubber particles is usually<are typically> added at low concentration and ,<thus>, form<a>discrete phase in tne continued phase<continuous matrix > of the hard matrix<phase>. an example of <a> toughening<toughened> polymer is impact PP. <PP itself has low <poor> impact strength <resistance>and is <very>brittle in<at> low temperatures>  however,<when> about 10-20% <of an> EPR containing around 50% ehtylene  is added into PP, the impact strength increase dramatically, and brittleness temperature <is>decreased markedly. the  EPR is  known to exist as <very>small discrete particles in the <PP>matrix.  theses particles toughen the matrix against crack propagation by dissipating large amounts of energy in the matrix material around the particle,thereby blunting the crack and inhibiting crack propagation.
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十四万人齐解甲，竟无一个是男儿
36楼2022-07-04 10:19:28
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236839923

铁杆木虫 (正式写手)
★ ★
ksq887: 金币+2, thanks for sharing~ 2022-07-14 16:38:12
On Tuesday, July 5th, 2022
Impact polypropylene copolymers may be made either by blending rubbers into polypropylene homopolymer or in situ a two-reactor system.  the in situ method of producing IPC is considered to be more advantageous  than post-reactor blending,               as judged by the superior properties of the resins produced and the commercial success of this method. the polypropylene homopolymer is produced<made> in the first reactor, and EPR is produced<made> in the <a>second reactor. PP was <is >blended with EPR in the <a>sequential process in which PP is added into the second reactor and<while> EPR is being polymerized.
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十四万人齐解甲，竟无一个是男儿
37楼2022-07-05 09:49:11
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236839923

铁杆木虫 (正式写手)
★ ★
ksq887: 金币+2, good job 2022-07-14 16:38:18
on Friday, July 8th, 2022
this product produced<made> in a <this>sequential reactor system, impact polypropylene, is a complex mixture of  homopolypropylene and ethylene-propylene <compolymers>.  The complete molecular structure analysis of such a polymer system is a formidable task. the purpose of this paper  is to molecular structure analysis of a commercial impact polypropylene using TREF  as the primary technique. the TREF technique is primarily employed to separate the complex mixture into discrete fractions, which can then be individually characterized, thereby yielding the identification of the individual components of the complex mixture. this knowledge permits one to gain a better understanding of the location and function of each components in the complex mixture.
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十四万人齐解甲，竟无一个是男儿
38楼2022-07-08 07:32:01
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236839923

铁杆木虫 (正式写手)
★ ★
ksq887: 金币+2, good job 2022-07-14 16:38:28
on Monday, July 11th, 2022
Analytical temperature-rising elution fractionation
Fractionation of the resins was done by TREF. this technique consists of dissovling the sample in trichorobenzene(TCB) at a concentration of 0.007g/cm-3 at 140C.  this solution was deposited on a steel column(250mmx10mmi.d.) packed with inert support, Chromosorb.  The column is then capped and cooled to room temperature at 1.5C/h-1 over about 3 days. the column is then connected into a system through which TCB is pumped at 2ml.min-1 while the temperature is increased at 20C/h.  the species eluting from the column are detected with an IR detector set at a detection wavelength of 3.41um(C-H strentch).  the eluting species can be trapped independently in fractions as a function of elution temperature. only a very small mass in each fraction can be obtained in this primarily analytical technique.
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十四万人齐解甲，竟无一个是男儿
39楼2022-07-11 09:39:15
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236839923

铁杆木虫 (正式写手)
★ ★
ksq887: 金币+2, thanks for sharing~ 2022-07-14 16:38:38
on Tuesday,  July 12th, 2022
Preparative temperature-rising elution fractionation
in order to collect large fractions of fractionated resins, a preparative TREF apparatus is<was> constructed. the construction and operation of the <a>similar version of the <this>apparatus is <has been>described in detail, previously. It is shown in Figure 1.  the polymer is dissolved in TCB  and cooled slowly as in the analytical TREF procedure. the cooled polymer and solvent are then introduced into the chamber of the apparatus in Figure 1, and heated slowly in incremental steps of temperature.  the fractionswas<are> removed from the valve at the bottom of the apparatus. the polymer was recovered by evaporating the TCB solvent and drying thoroughly in a vacuum oven.
in  order to facilitate preparative-scale fractionation, the soluble polymer, which was primarily the EPR, was removed by as a room-temperature-soluble prefraction in a preliminary fractionation step.  the preliminary fractionation was done as follows: the impact copolymer was dissolved at a concentration  of 5.1g in 250 ml  of spectroscopic grade 1.2.4, trichlorobenzene. it was dissolved <dissolution was attained >at approximately 160C with gentle stirring.  the solution was allowed to cool to room temperature and<the> precipitated polymer was recovered by centrifugation and filtration. the soluble polymer remained in the TCB solution at room temperature. the procedure was repeated two<additional> times on the TDB-insoluble polymer to remove exhaustively <all>the soluble polymer.  the soluble polymer was recovered by  evaporative stripping of TCB solvent and drying in a vaccum oven. the soluble polymer is <was>15.3% of  the original impact copolymer. only the insoluble polymer <fraction>was introduced into the preparative fractionation apparatus in Figure 1..
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十四万人齐解甲，竟无一个是男儿
40楼2022-07-12 08:51:03
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