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preparation and characteristics of a novel nano-sized calcium carbonate (nano-caco.sub.3)-supported nucleating agent of poly(l-lactide). - characteristics of polyester

by:Cailong     2019-08-15
preparation and characteristics of a novel nano-sized calcium carbonate (nano-caco.sub.3)-supported nucleating agent of poly(l-lactide).  -  characteristics of polyester
Poly (L-lactide)(PLLA)
Because it is biomass, it has attracted a lot of attention.
Derived, biodegradable. biocompatible.
Non-toxic to the environment and human body.
Recent innovations in production processes have significantly reduced production costs.
Further promote the study of its nature and potential applications (1). However.
The Crystal speed of PLLA is very slow.
This greatly limits the practical application.
Add a nuclear agent (NA)
It is proved to be an effective method to increase the crystalline rate by reducing the surface free energy barrier (2-5).
Several nuclear-forming agents have been developed and their effects on the behavior of PLLA crystals have been extensively studied (6-11).
Talcwas is a NA widely used in PLLA (6), (7).
The results show that the crystal is half
When adding 1wt % talc, the time for PLLA can be reduced to less than 1 minute.
Okamoto and colleagues use lowmolecular-
Weight fat amide, that is, N, N-ethylenebis(12-hydroxy-steara-mide).
As NA of PLLA, the crystalline dynamics and morphology of this PLLA/NA system were studied (8).
The results show that the density of the core and the overall crystal rate of PLLA are significantly increased.
Some of the compounds reported by chuanben, such.
The crystals of PLLA can be accelerated and the relationship between the chemical structure and nuclear efficiency of these nas is studied (9).
Li and Huneault studied the effects of nuclear and plastic on PLLA crystals by the addition of talc, sodiumstearate and calcium lactic acid as potential nuclear agents (10), andthe non-
Constant temperature data show that the combination of NA and plasticizer is necessary for the formation of significant crystals at high cooling rates.
In addition to the above nucleator, PLLA and poly (D-lactic acid)(PDLA)
Is one of the most effective and promising ways to increase the rate of poly () crystalslactic acid)(PLA)-
Basic materials (12-28).
It is found that the overall crystalline rate of the gypsum complex is much higher than that of pure PLLA or PDLA, suggesting that it has an extremely high radius growth rate and density (
Unit area or volume)
Compared with PLLAor PDLA spherical crystals, the formation of three-dimensional complex spherical crystals and a very short induction cycle.
However, the high production cost of PDLA greatly limits the wide application of stereo composite PLLA materials.
Metal phosphate is a synthetic inorganic/organic composite material with layered structure (29), (30).
It was reported by Mitomoet al.
The metal phosphate material can speed up the crystal rate of PLLA (31).
Recently, layered metal phosphon salt, zinc benzene phosphon salt (PPZn)
And by melting-
Hybrid technology (32).
PPZn has obvious nuclear effect on PLLA crystals.
Merge of 0.
02 wt % PPZn, PLLA can complete the crystal under the cooling of 10 [degrees]C [min. sup. -1].
In our previous work33)
By using a melting mix of three layered metal phosphate S, a layered metal phosphate with PLLA nuclear has been prepared, I . E. e.
, Pp zinc, calcium benzene phosphon salt (PPCa)
, And ammonium benzene phosphon (PPBa).
Morphology, crystal and biological degradation of layered benzene phosphon salt-nuclear PLLA with different metal ions ([Zn. sup. 2+],[Ca. sup. 2+], and [Ba. sup. 2+])
Was investigated.
The study found that PPZn, PPCa and PPBa as effective nuclear-forming agents can accelerate the non-constant temperature and constant temperature crystal and biological degradation of plla.
Although metal phosphon salts have an excellent nuclear effect on PLLA, which has aroused great interest, the toughness of nuclear PLLA salts is lower than that of non-nuclear PLLA
The high cost of the metal phosphon salt limits its application.
If good dispersion is achieved, the toughness of rigid particles will be more favorable than that of rubber because the former can increase stiffness and toughness (34).
Nano[CaCO. sub. 3]
Or organic modified silica Earth (OMLS)
In order to improve toughness, PLLA matrix has been extensively studied (35).
The evidence of micro-mechanical deformation shows that Nano[CaCO. sub. 3]
Increased pressure. at-
The fracture of PLLA is caused by a large number of cracks in the longitudinal direction of the entire instrument, and due to the agglomeration of tiny gaps, the matrix finally fails.
Improving the toughness of nuclear PLLA is a hot research topic in the fields of industry, science and technology.
In order to improve the nuclear efficiency and improve the mechanical properties of the nuclear PLLA, adding nuclear aid to nanoparticles is a promising method.
Based on the principle of efficient preparation-
Nuclear mechanism of olefin polymerization loaded catalyst and metal phosphon salt, nano-loaded Crystal nuclear agent[CaCO. sub. 3]
By supporting the PPCaon nano-[CaCO. sub. 3]
This is the first surface in this work.
Supported Nano[CaCO. sub. 3]
Not only can the active components of the crystal core agent be effectively dispersed and the efficiency be improved, but also the toughness and stiffness of the crystal core PLLA can be increased due to the toughness and enhancement of the nano-materials. [CaCO. sub. 3](35).
Therefore, for Nano[CaCO. sub. 3]
The core efficiency and popularization of nuclear PLLA can be improved by loading the core agent.
The purpose of this paper is to prepare and characterize nanometers[CaCO. sub. 3]supported PPCa.
Morphology, non-isomild and constant temperature crystalline dynamics, spherical morphology and crystal structure of nuclear PLLA prepared by nanoparticles[CaCO. sub. 3]-
The PPCa supported is systematically studied.
Experimental materials PLLA (4032D)
Used for this study, including about 98% liters
C-Ester is a commercial product of Natureworks. Ltd. , USA.
It shows the density of 1. 25 g [cm. sup. -3], a weight-
Average molecular weight ([M. sub. w])of 207 kg [mol. sup. -1].
Benzene phosphate (PPOA)
At about 163. 3[degrees]
C was purchased from Jiaxin alpharm Fine Chemical Co. , Ltd. Ltd. , China. The nano-[CaCO. sub. 3]
Solvay provides an average granularity of about 70 nm at one time (Shanghai)Co. , Ltd. , China.
Coated with a 3 wt % of hard acid.
Its specific surface area is greater than 30 [m. sup. 2][g. sup. -1](
According to the manufacturer).
PPCa was synthesized according to the previous work (33).
Preparation of crystal cores supported by nano-materials[CaCO. sub. 3]PPOA and nano-[CaCO. sub. 3]
Vacuum dry at room temperature before use.
Crystal cores supported by nano-materials[CaCO. sub. 3]
Prepared by dipping method.
PPOA is mixed with nano[CaCO. sub. 3]
Stir in acetone solution at room temperature for 4 hours
Then centrifuge the mixture.
After removing the acetone, stir the centrifugal again, re-disperse the white precipitate in the acetone, and collect the white precipitate.
This dispersioncentrifugation-
In order to remove the unresponsive PPOA, the collection cycle was repeated three times.
Finally, support nano-[CaCO. sub. 3]
Dry in a vacuum oven [80]degrees]
C to considerable weight.
Nano-composite crystal cores prepared[CaCO. sub. 3]
Expressed as NAx, x indicates the initial mass ratio of support/PPOA ([M. sub. Support]/[M. sub. PPOA]).
Before the sample is prepared, all materials are fully dripped in the vacuum furnace at the appropriate temperature.
PLLA nuclear with different [contents of 1 wt %, 3 wt % and 5 wt %M. sub. Support]/[M. sub. PPOA]
Melt the composite at 180 [degrees]
Using Haake Rhine 600 mixer for 8 minutes, the heat transfer speed is 50 rpm, and the mixing weight of each batch is about 60 grams.
In contrast, neat PLLA, 1wt % and 2wt % PPCa nuclear PLLA and 1-filled PLLA5 wt% nano-[CaCO. sub. 3]
Also prepared under the same conditions.
Then the sample is hot.
Press at 190 °c for about 1 minute and then cold-
Press at room temperature to form a film with a thickness of about 1.
Representation of 0mm.
Characterized by infrared (FTIR)
Recording the spectrum using aBIO-Rad Win-
Infrared Spectrometer in 500-range4000 [cm. sup. -1]
Resolution 4 [cm. sup. -1].
The molecular weight parameters of pure PLLA and various samples were determined by gel infiltration chromatography (GPC)
Use a water meter (515 HPLC)
Equipped with Wyatt interferometer.
At 25c, the gel column was eluded with methanol at a concentration of 1 ml. [min. sup. -1].
Calibration of polyethylene ester for molecular weight.
After melting treatment, pure PLLA, melting-
Processed PLLA with 2 PLLA. 0 wt% PPCA. 5. 0 wt%[CaCO. sub. 3]and 5.
0 wt % NA5 was examined, which was 207. 195. 185.
188 and 192 kg [mol. sup. -1]with [M. sub. w]/ [M. sub. n]values of1. 73, 1. 80. 1. 70. 1. 82, and 1.
75 respectively.
The representation of molecular weight parameters confirms this.
The PLLA is mixed with PPCA melting under processing conditions. [CaCO. sub. 3]andnano-[CaCO. sub. 3]-
The supporting nuclear agent did not induce a significant decrease in the mean molar mass of PLLA weight through thermal degradation or hydrolysis of the polyester chain.
Pan et al also reported similar results from PLLA/ppzblendar. (32).
Due to the different molecular weight and melting processing conditions of the initial PLLA, there may be slight differences.
Field emission scanning electron microscopy was used to observe the morphology of the broken surface prepared under liquid nitrogen (SEM)(XL30 ESEM EEG. FEI Co. ).
Before the measurement, the surface of the sample was coated with a thin layer of gold.
Differential Scanning heat meter using TA instrument (DSC)
Q20 and general analysis 2000.
Used for calibration of temperature and enthalpy.
All operations are carried out under nitrogen purification.
The weight of the sample varies between 5 mg and 8 mg.
In the case of non-constant temperature melting crystals, the sample is heated from the ambient temperature to 190 °c at a heating rate of 50 °c [min. sup. -1].
Held for 2 minutes to erase the history.
Then cool to 0 °c at a cooling rate of 10 (7 [min. sup. -1].
Change cooling from 190 ° c at a cooling rate of 10 ° c [min. sup. -1].
These samples are re-heated from 0 °c to 190 °c at a heating rate of 10 °c [min. sup. -1]
To study the subsequent melting behavior.
The peak temperature of the crystal is obtained from the cooling trace.
Ironically, at a heating rate of 10 °c, the melting point temperature and melting enthalpy of the samplemin. sup. -1]
From the normalization of the crystalline enthalpy and the melting enthalpy to the PLLA content, the crystalline enthalpy and the melting enthalpy are calculated.
In the case of a constant temperature melting crystal experiment, the sample is heated at a rate of 50 °c from the ambient temperature to 190 °c [min. sup. -1]. held for 2 min.
Cooling to crystal temperature ([T. sub. c]
The cooling rate is 45 ℃ [min. sup. -1]
Until the end of the amorphous crystal.
The Crystal temperatures selected for this study were 130 °c and 140 °c, respectively.
These exceptions are recorded for data analysis.
Optical microscope (P0M)(Leica DM2500 P)
Temperature Controller (Linkam LTS 350)
Used to study the form of transparency.
The sample was first subjected to annealing at 190 °c 2 times for destruction to eliminate any thermal history and then cooled to 140 °c in a cooling furnace at 50 °c [min. sup. -1]for 50 min. Wide-angle X-
Ray diffraction (WAXD)
Dmax 2500 X-record pattern using aRigaku model
Ray diffraction.
WAXD mode is recorded from 5 to 40 points at [3]min. sup. -1]
In order to study the chemical reaction between PPOA and nanoparticles, the results and discussion of the crystalline behavior and melting properties of PPOA and loaded nuclear agents[CaCO. sub. 3]
The crystalline behavior and melting properties of PPOA and loaded nuclear agents were characterized by DSC.
The DSC curve of PPOA and the supporting nuclear agent are shown in the figure. 1.
He could observe a melting peak at 167 for PPOA.
The enthalpy of melting is about 170. 8 J [g. sup. 1]
Peak at 132.
The enthalpy of crystal is about 156 ℃. 6 J [g. sup. -1]
For the loaded Crystal nuclear agent na5 prepared by the immersion method, no obvious melting and crystalline peaks of PPOA were observed during heating and cooling.
Figure 2 shows the infrared spectrum of nanoparticles[CaCO. sub. 3]
PPOA and the corresponding nuclear agent na5.
In the spectrum of PPOA, P--
Cstretching band properties of P--[C. sub. 6][H. sub. 15]
Group and P = 0 stretch bands exist in 1439 [cm. sup. -1]and 1222[cm. sup. -1]Respectively (36).
Also, C--H out-of-
The plane deformation band of the single-substituted benzene ring is located at [756 and 696]cm. sup. -1]Respectively (36).
For the supported nuclear agent NA5, C--H out-of-
Plane deformation band of a single substituted benzene ring (756 and 696 [cm. sup. -1]
PPOA can be clearly observed, which indicates that the chemical reaction occurs at the nano[CaCO. sub. 3]
And PPOA form PPCa on the Nano Surface[CaCO. sub. 3]
Possible chemical reactions between PPOA and nano during the dipping process[CaCO. sub. 3]
As shown in Scheme 1.
Figure 3 shows the WAXD pattern of the Nano[CaCO. sub. 3]
Support nuclear agent for NA5 and PPCA.
The WAXD mode shows a 2 [theta]value of 5. 6[degrees]
And the d spacing of the mezzanine is 1. 528 nm of PPCa [
From (010)reflection].
Very similar layer spacing of nano-supported PPCa[CaCO. sub. 3]
NA5 was observed, indicating that the crystal structure of the supported PPCa has not changed.
The morphology of the supporting nuclear agent in the plla matrix and the dispersion of the dispersed NAs in the polymer matrix and the interface interaction between the polymer matrix and the NAs play an important role in the crystalline behavior of the polymer.
Uniform dispersion of NAs and strong interface interaction between polymer matrix and NAs can effectively enhance the crystal of polymer.
The structure and dispersion of supporting nuclei in PLLA matrix are revealed.
, The fracture surface of the sample was studied by SEM.
Figure 4 shows the broken surface of the neat PLLA, PLLA containing 1.
0 wt % PPCA, including PLLA 1. 0 wt%, 3. 0 wt%, and5. 0 wt% NA5.
The hierarchical structure of PPCa with severe aggregation can be clearly seen in Figure 1. 4b.
In addition, it was found that some ppca were broken down and debited from the PLLA matrix.
The typical fracture phenomenon of the PLLA/PPCa mixing shows that the interface adhesion between the PPCa and the PLLA matrix is poor.
For pllacontainer containing crystal cores supported in figure 1
4c and d, there are only white spots on the surface of the PLLA matrix, and this feature is more obvious with the increase of the content of the supporting nuclear agent.
Compare with the surface of neat PLLA in figure 1
4a, it can be seen that white spots should be the supporting crystal core agent. Generally,nano-[CaCO. sub. 3]
It is easy to gather due to particles-
Nano particles interacting and gathering[CaCO. sub. 3]
Particles can also be found in PLLA/nano-[CaCO. sub. 3]
Mix as shown in the figure4.
However, Nano[CaCO. sub. 3]
The particles are evenly dispersed in the PLLA matrix with a load of 5wt %, which is due to an increase in sufficient shear force during the melting composite process and the 18-acid coating surface process.
In addition, it is clear that the dispersion and interface adhesion of PLLA combined with PPCa are superior to that of PPCa (
As can be seen from the figure4).
Therefore, some of the properties of the PLLA combined with the load-type nuclear agent may be superior to that of the PPCa, which will be discussed in the following sections.
Effect of Nano-[CaCO. sub. 3]
And the effect of PPCa on the crystalline behavior and melting properties of PLLA containing nano-composite materials[CaCO. sub. 3]
The nuclear active ingredient PPCa was prepared.
During the preparation process, a chemical reaction occurred between PPOA and nanoparticles. [CaCO. sub. 3]
Formation of PPCa nuclear agent on nano-materials[CaCO. sub. 3]surface.
Therefore, the influence of nanotechnology[CaCO. sub. 3]
The effects of PPCa on the crystalline behavior and melting properties of PLLA were first investigated.
Figure 5 shows the DSC crystalline and melting curves of PPCA cores and p1 aa filled with nanometers[CaCO. sub. 3]
, The corresponding data is listed in Table 1.
The degree of crystal has been calculated according to the equation [W. sub. c]=100 x ([DELTA][H. sub. m][DELTA][H. sub. cc])/[DELTA][H. sup. 0. sub. m]where[W. sub. c].
Is the degree of crystal ,[DELTA][H. sub. cc]
Is a specific enthalpy or melting.
It is the specific enthalpy of cold crystal. [DELTA][H. sub. 0. sup. m]
Is it fusion heat or 100% crystalline PLLA, 93 J [J [g. sup. -1]
As reported in the literature (37).
You can see clearly from the picture.
5 there is no crystal peak at the cooling rate of 10 ℃ [min. sub. -1]
Nano-filled neatPLLA and PLLA[CaCO. sub. 3]
: However, there is a molten crystal peak at 114.
9c of PLLA nuclear with PPCA can be observed.
Subsequent melting properties of pure PLLA filled with PPCA[CaCO. sub. 3]
After cooling at a temperature of 10 °c. min. sup. -1]
There are more differences between each other.
As can be seen from the figure
5 h, pure PLLA has glass penetration temperature ([T. sub. g])
About 60 ℃ and cold crystal temperature ([T. sub. cc])of around 111. 7 C.
Nano-[CaCO. sub. 3]
Not showing a big impact on [T. sub. g]and[T. sub. cc]of PLLA.
However, PPCA-nuclear PLLA does not show cold crystals when heated to melting, indicating that the crystals can be completed at a cooling rate of 10 °c [min. sup. 1].
Therefore, PPCA is a PLLA nuclear agent with high nuclear efficiency.
Figure 6a shows the DSC crystalline curve of PLLA which is nuclear By supported crystal cores.
The characteristic parameters based on exotherms are analyzed (38-40)
Other methods used to distinguish the effects of supporting nuclear agents on the overall crystalline process are described below (
Comprehensive effects of nuclear and growth steps)
, Crystalline degree, core rate and crystal size distribution.
As shown in the previous work, the Exotherm parameter (38-40)
Temperature at the beginning of the crystal ([T. sub. onset])
At the point where the exotherm originally deviated from the baseline, peaktemperature ([T. sub. p])
, Which can be called the characteristic temperature, initial slope of the entire crystalline process ([S. sub. i])
, Measured as the slope of the initial linear part of the peak of the exotherm, the width of the exotherm ([DELTA]W)
Crystalline enthalpy normalized with PLLA content ([DELTA][H. sub. c])
This is related to the degree of crystal.
Table 2 shows the value of the Crystal parameter determined from dscgrams determined.
It is clear that the supporting nuclear agent has increased significantly [T. sub. p]of PLLA.
Plla with addition of 1wt % loaded Crystal core NA40 has [T. sub. p]of 112. 7 C and the [T. sub. p]
The content of PLLA increases with the increase of the content of supporting nuclear agent.
In addition, compared with plla, which is nuclear by PPCA ,[S. sub. i]
And the reduction of.
The addition of a supporting nuclear agent was observed.
The increase in the dispersion of the nuclear agent will increase [S. sub. i]
And lead to a nuclear that occurs almost simultaneously.
Causes most crystals to grow at the same time, resulting in spherical crystals distributed in small and narrow sizes.
The degree of crystal is inconsistent with the trend of change [S. sub. i].
This may be due to the fact that when growth is affected by the fluidity of the molecular chain, the nucleus is affected by the nucleator.
Figure 6b shows the DSC melting curve of the PLLA that is nuclear by these filled crystal cores.
Relevant data can be seen in Table 1.
There is no cold junction peak in the melting curve, which is similar to PPCA nuclear PLLA.
For PLLA and PLLA samples with PPCa and [CaC0. sub. 3]
Two melting peaks ([T. sub. m1]and [T. sub. m2])were observed.
The phenomenon of double melting is attributed to melting and re-Crystal-
The process of heating and melting.
The lower temperature peak is attributed to the melting of the primary crystal, and the higher temperature peak or peak corresponds to the melting of the crystalline Crystal (41-45).
When the supported crystal core agent is used, the crystal temperature ([T. sub. p])
Relatively high, forming a perfect crystal (32)
Therefore, the sample melts without temperature
A single absorption peak can be observed during re-Crystal.
In order to quantitatively evaluate the enhanced nuclear activity of the loaded Crystal nuclear agent, we assume that all acids react;
Then the concentration of PPCa in the Nano[CaC0. sub. 3]
Support materials can be calculated.
Figure 7 shows the curve of PPCa content and [in PLLA matrix]T. sub. p]
PLLA nuclear by PPCa and supported nuclear agent.
Although the crystalline behavior and melting properties of PLLA nuclear by supporting nuclear agent are similar to that of PPCA nuclear, PLLA nuclear by supporting nuclear agent nuclear
The dispersion of support nuclear agent in PLLA matrix is better than that of PPCa in PLLAmatrix (
As can be seen from the figure4). Thus, the nano-[CaCO. sub. 3]
Supports a specific crystal surface (
More effective core)
The addition to the crystalline PLLA greatly improves the crystalline behavior of PLLA. Therefore.
The loaded nuclear agent has a high nuclear capacity.
As introduced in the experimental part.
The overall constant temperature crystals of different samples at temperatures of 130 °c and 140 °c were investigated by DSC. respectively.
In the process of constant temperature crystal
Relative degree of Crystal ([X. sub. t])
The crystalline time is defined as the ratio of the region under the heat release curve between the start crystalline time and the crystalline time t to the entire region under the heat release curve from the start crystalline time to the end crystalline time. Figure 8 shows [X. sub. t]
For pure PLLA and PLLA containing 5wt % nanometers, compared with t. [CaCO. sub. 3]. 2 wt% PPCa.
5 wt % NA5 crystals at 130 ° c and 140 ° c, respectively.
It is clear that the addition of a support nuclear agent enhances the constant temperature melting crystals of pllacomon compared to other samples.
The Avrami equation is often used to analyze the constant temperature crystalline dynamics of the polymer.
According to which [X. sub. t]
Dependent on the crystal time t can be expressed (46),(47): 1 -[X. sub. t]= exp(-[kt. sub. n])(1)
Where n is the Avrami index depending on the crystal-like core and growth geometric properties, and k is the total rate constant associated with the nuclear and growth contribution.
The linear form of the equation.
I can express it as follows: log [-ln(1 -[X. sub. t])]
= Logk nlogt (2)
Avrami parameters n and k can be obtained from the slope and intercept, respectively.
Figure 9 shows the Avrami diagram of log [-ln(1 -[X. sub. t])]
For pure PLLA and PLLA containing 5wt % Nano, control log t[CaCO. sub. 3]
, 2 wt % PPCa and 5 wt % NA5 crystalline under 130 [degrees]C and 140 [degrees]
C, respectively.
Table 3 summarizes and lists avrami parameters for various preparations.
As can be seen from table 3, the value of Avrami index n is from 2. 3 to 3.
0, and is almost insensitive to the addition of Nano[CaCO. sub. 3]
, PPCa, as well as the crystal core agent loaded, indicate that the mechanism of crystal may not change.
The DSC results reported in this paper are consistent with the spherical morphology and growth studies in the next section.
On the other hand, the k value of all samples decreases with the increase of the crystal temperature, which indicates that the crystalline process studied in this study is a core-
A process controlled by low overheating ([T. sup. 0. sub. m]-[T. sub. p](48), where [T. sup. 0. sub. m]
Indicates a balanced melting point.
For a given supported nuclear agent.
The value of K increases as the content increases.
The increase in the K value indicates that the addition of the support nuclear agent speeds up the overall crystalline process of PLLA compared to the neat PLLA, this should be attributed to the Isophase nuclear effect of the supporting nuclear agent on the crystal of PLLA. The half-
Time Crystal time ([t. sub. 0. 5])
This is defined as halfperiod (i. e. , 50%)
From the beginning of the crystal to the end of the crystal, it is an important parameter to discuss the dynamics of the constant temperature crystal. The value of[t. sub. 0. 5]
Can he calculate according to the following equation :[t. sub. 0. 5]= [(ln 2/k). sup. l n](3)
The values of [t. sub. 0. 5]
Calculated by Eq.
3 and listed in Table 3. too.
Figure 10 shows the curve between PPCa content and [in PLLAmatrix]t. sub. 0. 5]
PLLA-shaped cores are made by PPCa and supported nucleators.
It can be clearly seen from Table 3 that for PLLA with a support core agent added, the overall crystalline speed is faster than that of pure PLLA.
In the case of similar content to the active ingredient PPCA of the nuclear agent, the overall crystalline rate of PLLA added with the loaded nuclear agent is faster than that of PLLA added with PPCa.
The difference in total Crystal rate may be related to the following factors.
Although the loaded crystal cores and PPCa are both effective NAs that improve the crystal speed of PLLA.
The ability to crystallize and the impact on the overall crystalline process are different.
The crystalline behavior of polymers in the presence of NAs is affected by many factors.
Such as composition.
Interface interaction, size.
And distribution.
Uniform distribution is expected.
A good interface interaction may help to improve the nuclear efficiency.
The dispersion and interface interaction of the supporting nuclear agent is much better than the dispersion and interface interaction of PPCa in the entire PLLAmatrix, as shown in the SEM observations of the previous part.
Therefore, compared with PPCa, the loading crystal core agent is more effective in promoting the crystal of PLLA.
Influence of the existence of nano-[CaCO. sub. 3].
The effects of PPCA and loaded crystal cores on the morphology of PLLA spherical crystals were investigated with POM.
Figure 11 shows the shape of the sphere that crystallizes for 50 minutes at 140 °c.
As for pure C fat,
The size is about 200 [developed]micro]
Diameter m can be observed.
It is clear that in the presence of a supporting nuclear agent, the size of the spherical crystal becomes smaller, indicating an increase in the density of the nuclear shape.
In addition, the diameter of the sphere decreases with the increase of the PPCA content of the active component of the nuclear agent.
The density of the core is the opposite trend.
Spherical morphological studies have shown that due to the presence of an on-transplanted nuclear agent in the PLLA matrix, the nuclear density of the PLLA is greatly increased, which is very consistent with the DSC results in the previous section.
These results clearly show that in the PLLA matrix, the good dispersion of the supporting nuclear agent and the interface interaction effectively affect the spherical morphology and overall crystalline process of PLLA.
Figure 12 shows the WAXD pattern of various formulas that crystallize for 2 hours at 120 °c to ensure a high level of crystals.
PLLA can be crystallized in [alpha][beta]. and [gamma]forms. The [alpha]
Recently, the form of PLLA with restricted disorder modification was discovered and defined [alpha]form (49).
The most common deformation of PLLA is [alpha]
It is considered to grow under normal conditions, such as melting, cold, or crystal of a solution. The [beta]
Forms are usually formed when they stretch their [alpha]
Peers at high and high temperaturesdraw ratio. The[gamma]
The form can be obtained by the extension Crystal on six benzene (HMB)substrate (49).
In this case, WAXD experimental samples were prepared by Crystal from elt;
Therefore, the sample should be crystallized in [alpha]form. As shownin Fig.
12. the neat PLLA presents three main characteristic diffraction peaks at about 15. 0 [degrees], 16. 8[degrees], and 19. 2[degrees]
Corresponding (010), (200), and (203)
This is the typical diffraction peak [alpha]
The form as mentioned earlier (32), (48).
Waxd pattern of nano PLLA[CaCO. sub. 3]
, PPCA, and the supported nuclear-forming agent are almost the same as the corresponding pure PLLA samples, which indicates that the Nano[CaCO. sub. 3]
, PPCA and nano-[CaCO. sub. 3]
After 120 [crystalline], the loaded nuclear agent did not change the crystal structuredegrees]C.
Conclusion in view of the efficient preparation principle-
For the first time, we have prepared a nuclear mechanism for supported olefin polymerization catalyst and PPCa.
By supporting PPCa on nano-materials, an efficient crystal core agent was prepared[CaCO. sub. 3]surface.
Compared to PPCa, the supported nuclear-forming agent exhibits a higher nuclear-forming capability.
The addition of a loaded Crystal core improves the crystal rate of PLLA.
He can get the same degree of nuclear with less quantity.
To: Han Changyu: e-
Email: cyhan @ ciaejl.
Cn or Li Songdong; e-
Email: eils @ eiaejl.
Cn contract gram sponsor: National Natural Science Foundation: contract award number: 50703042: Contract Award sponsor: Jilin provincial science and technology department;
Contract authorization number: 20116025. DOI 10. 1002/pen.
23095 online release in the Wiley Online Library (
Wileyonlinelibrary. com). [C]
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Zhang Huiliang ,(1)Lisong Dong (1)(1. )
Key Laboratory of polymer ecological materials, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China (2. )
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