Description:FIELD
The present disclosure relates to a self-reinforced polymeric blend composition and a process for its preparation.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
Several alternative ways to reinforce isotactic polypropylene (iPP) are known. One such way is mixing and filling of the iPP with non-polymeric fibers such as glass fibers, carbon nano-tubes, carbon fibers and the like. Such fiber reinforced polypropylene composition (FRPCs) exhibit two to three times higher mechanical properties (tensile strength) without a significant increase in weight as compared to the normal iPP. Despite their evident advantages, the challenge for FRPC lies in recyclability and sustainability, which leads to additional operational costs. In comparison, substitution of glass fibers with carbon nanotubes/fibers present similar challenges and adds a substantial price increase in the case of carbon fibers.
The polyethylene can be reinforced by inclusion of ultra-high molecular weight polyethylene (UHMWPE) fraction via melt extrusion. A blend of high density polyethylene (HDPE) and UHMWPE containing up to 30 weight % of the ultra-high molecular weight component has enhanced abrasion resistance, flexural, tensile and impact strength in comparison with pure HDPE. The self-reinforced effect in the blends attribute due to the formation of shear-induced shish-kebab structures during the processing, which is enhanced by the UHMW component. However, the reinforcement of iPP with UHMWPE is nearly impossible due to a poor miscibility. The use of gel-casting can produce iPP and UHMWPE blends, but the viscosity of the blend decreases with the increasing amount of iPP. In order to improve the miscibility of polyethylene (PP) and iPP, several chemical and physical compatibilizers are required.
The use of iPP-PE di-block and tri-block (iPP-PE-iPP) copolymers can gel iPP and HDPE into a high toughness blend. However, the properties of such blends are far from optimal, and the recyclability issues remain unresolved.
Therefore, there is felt a need for self-reinforced polymeric blend composition that mitigate the drawbacks mentioned herein above or at least provide a useful alternative.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows.
It is an object of the present disclosure to ameliorate one or more problems of the background or to at least provide a useful alternative.
Another object of the present disclosure is to provide a self-reinforced polymeric blend composition.
Still another object of the present disclosure is to provide a self-reinforced polymeric blend composition that has high melting temperature.
Yet another object of the present disclosure is to provide a process for the preparation of a self-reinforced polymeric blend composition.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure relates to a self-reinforced polymeric blend composition. The self-reinforced polymeric blend composition comprising 70 mass% to 99 mass% of a low molecular weight isotactic polypropylene matrix with respect to the total mass of the self-reinforced polymeric blend composition; and 1 mass% to 30 mass% of an ultra-high molecular weight isotactic polypropylene with respect to the total mass of the self-reinforced polymeric blend composition.
The present disclosure also relates to a process for the preparation of a self-reinforced polymeric blend composition. Predetermined amounts of a low molecular weight isotactic polypropylene and an ultra-high molecular weight isotactic polypropylene are blended at a predetermined temperature at a predetermined mixing torque for a predetermined time period to obtain the self-reinforced polymeric blend composition.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The present disclosure will now be described with the help of the accompanying drawing, in which:
Figure 1 illustrates a stress vs strain curve of self-reinforced polymeric blend composition containing various concentrations of entangled ultra-high molecular weight isotactic polypropylene (UHMWiPP) ranging from 0 mass% to 25 mass% in accordance with the present disclosure;
Figure 2 illustrates a comparative graph of torque vs time of a self-reinforced polymeric blend composition containing disentangled UHMWiPP (Mw: 1.4 x 106 g/mol) and entangled UHMWiPP in accordance with the present disclosure;
Figure 3 illustrates a comparative graph of stress vs strain of a self-reinforced polymeric blend compositions containing disentangled UHMWiPP (Mw: 1.4 x 106 g/mol) and entangled UHMWiPP in accordance with the present disclosure; and
Figure 4 illustrates a comparative graph of stress vs strain of a self-reinforced polymeric blend composition containing 25% disentangled UHMWiPP (Mw: 1.4 x 106 g/mol), pure low molecular weight isotactic polypropylene (iPP), and pure disentangled UHMWiPP (Mw: 1.4 x 106 g/mol).
DETAILED DESCRIPTION
Embodiments, of the present disclosure, will now be described with reference to the accompanying drawing.
Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, known processes or well-known apparatus or structures, and well known techniques are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," “including,” and “having,” are open ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure are not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.
The terms first, second, third, etc., should not be construed to limit the scope of the present disclosure as the aforementioned terms may be only used to distinguish one element, component, region, layer or section from another component, region, layer or section. Terms such as first, second, third etc., when used herein do not imply a specific sequence or order unless clearly suggested by the present disclosure.
As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed elements.
Several alternative ways to reinforce isotactic polypropylene (iPP) are known. One such way is mixing and filling of the iPP with non-polymeric fibers such as glass fibers, carbon nano-tubes, carbon fibers and the like. Such fiber reinforced polypropylene composition (FRPCs) exhibit two to three times higher mechanical properties (tensile strength) without a significant increase in weight as compared to the normal iPP. Despite their evident advantages, the challenge for FRPC lies in recyclability and sustainability, which leads to additional operational costs. In comparison, substitution of glass fibers with carbon nanotubes/fibers present similar challenges and adds a substantial price increase in the case of carbon fibers.
The polyethylene can be reinforced by inclusion of ultra-high molecular weight polyethylene (UHMWPE) fraction via melt extrusion. A blend of high density polyethylene (HDPE) and UHMWPE containing up to 30 weight % of the ultra-high molecular weight component has enhanced abrasion resistance, flexural, tensile and impact strength in comparison with pure HDPE. The self-reinforced effect in the blends attribute due to the formation of shear-induced shish-kebab structures during the processing, which is enhanced by the UHMW component. However, the reinforcement of iPP with UHMWPE is nearly impossible due to a poor miscibility. The use of gel-casting can produce iPP and UHMWPE blends, but the viscosity of the blend decreases with the increasing amount of iPP. In order to improve the miscibility of polyethylene (PP) and iPP, several chemical and physical compatibilizers are required.
The use of iPP-PE di-block and tri-block (iPP-PE-iPP) copolymers can gel iPP and HDPE into a high toughness blend. However, the properties of such blends are far from optimal, and the recyclability issues remain unresolved.
Therefore, there is provided a self-reinforced polymeric blend composition and a process for its preparation.
In an aspect, the present disclosure provides a self-reinforced polymeric blend composition.
The self-reinforced polymeric blend composition comprising 70 mass% to 99 mass% of a low molecular weight isotactic polypropylene matrix with respect to the total mass of the self-reinforced polymeric blend composition, and 1 mass% to 30 mass% of an ultra-high molecular weight isotactic polypropylene with respect to the total mass of the self-reinforced polymeric blend composition.
In accordance with the present disclosure, the self-reinforced polymeric blend composition has an average Young’s modulus (E) in the range of 0.5 GPa to 2.00 GPa. In an exemplary embodiment, the average Young’s modulus (E) is 1.48 GPa. In another exemplary embodiment, the average Young’s modulus (E) is 1.91 GPa. In still another exemplary embodiment, the average Young’s modulus (E) is 1.1 GPa.
In accordance with the present disclosure, the self-reinforced polymeric blend composition has an average stress at yield (sy) in the range of 35 mPa to 50 mPa. In an exemplary embodiment, the self-reinforced polymeric blend composition has an average stress at yield (sy) of 46 mPa. In another exemplary embodiment, the self-reinforced polymeric blend composition has an average stress at yield (sy) of 40 mPa.
In accordance with the present disclosure, the self-reinforced polymeric blend composition has an average strain at yield (ey) in the range of 4.0% to 7.0%. In an exemplary embodiment, the self-reinforced polymeric blend composition has average strain at yield (ey) of 5%. In another exemplary embodiment, the self-reinforced polymeric blend composition has an average strain at yield (ey) of 6%.
In accordance with the present disclosure, the self-reinforced polymeric blend composition has an average maximum stress (sm) in the range of 35 mPa to 50 mPa. In an exemplary embodiment, the self-reinforced polymeric blend composition has an average maximum stress (sm) of 46 mPa. In another exemplary embodiment, the self-reinforced polymeric blend composition has an average maximum stress (sm) of 41 mPa.
In accordance with the present disclosure, the self-reinforced polymeric blend composition has an average stress at break (sb) in the range of 15 mPa to 35 mPa. In an exemplary embodiment, the self-reinforced polymeric blend composition has an average stress at break (sb) of 34 mPa. In another exemplary embodiment, the self-reinforced polymeric blend composition has an average stress at break (sb) of 27 mPa.
In accordance with the present disclosure, the self-reinforced polymeric blend composition has an average strain at break (eb) in the range of 15% to 75%. In an exemplary embodiment, the average strain at break (eb) is 19%. In another exemplary embodiment, the average strain at break (eb) is 22%. In still another exemplary embodiment, the average strain at break (eb) is 62%.
In accordance with the present disclosure, the low molecular weight isotactic polypropylene matrix has a molecular weight in the range of 100,000 g/mol to 300,000 g/mol. In an exemplary embodiment, the low molecular weight isotactic polypropylene matrix has a molecular weight of 245,000 g/mol.
In accordance with the present disclosure, the low molecular weight isotactic polypropylene matrix has a melting point in the range of 155 oC to 160 oC when heated at a rate of 10 oC/minute. In an exemplary embodiment, the low molecular weight isotactic polypropylene matrix has a melting point of 158 oC when heated at a rate of 10 oC/minute.
In accordance with the present disclosure, the low molecular weight isotactic polypropylene matrix has a molecular weight distribution selected from unimodal and bimodal.
In accordance with the present disclosure, the ultra-high molecular weight isotactic polypropylene has a molecular weight in the range of 1.0 x 106 g/mol to 4.0 x 106 g/mol. In an exemplary embodiment, the ultra-high molecular weight isotactic polypropylene has a molecular weight of 1.2 x 106 g/mol. In another exemplary embodiment, the ultra-high molecular weight isotactic polypropylene has a molecular weight of 1.4 x 106 g/mol. In still another exemplary embodiment, the ultra-high molecular weight isotactic polypropylene has a molecular weight of 2.4 x 106 g/mol. In still another exemplary embodiment, the ultra-high molecular weight isotactic polypropylene has a molecular weight of 3.0 x 106 g/mol.
In accordance with the present disclosure, the ultra-high molecular weight isotactic polypropylene has a bulk density in the range of 0.01 g/cc to 0.98 g/cc.
In accordance with the present disclosure, the ultra-high molecular weight isotactic polypropylene has a polydispersity index in the range of 1.2 to 7.
In accordance with the present disclosure, the ultra-high molecular weight isotactic polypropylene has a complex viscosity ? at a shear stress of 0.1 rad/s at 190 °C in the range of 160,000 Pa•s to 700,000 Pa•s.
In accordance with the present disclosure, the ultra-high molecular weight isotactic polypropylene has a unimodal molecular weight distribution.
In accordance the present disclosure, the ultra-high molecular weight isotactic polypropylene is disentangled.
In accordance with the present disclosure, a mixing torque is in the range of 1200 N to 1800 N, when the self-reinforced polymeric blend composition is disentangled. In an exemplary embodiment, the mixing torque is 1500 N when the self-reinforced polymeric blend composition is disentangled.
In accordance with the present, disclosure, the ultra-high molecular weight isotactic polypropylene is entangled.
In accordance with the present disclosure, the self-reinforced polymeric blend composition has a mixing torque in the range of 500 N to 3250 N, when the ultra-high molecular weight isotactic polypropylene is entangled. In an exemplary embodiment, the self-reinforced polymeric blend composition has a mixing torque of ~3000 N, when the ultra-high molecular weight isotactic polypropylene is entangled.
In accordance with the present disclosure, the self-reinforced polymeric blend composition has a moulded injection impact resistance in the range of 1.2 kJ/m2 and 3.0 kJ/m2 as determined by ASTM D256, when the ultra-high molecular weight isotactic polypropylene is entangled.
In accordance with the present disclosure, the self-reinforced polymeric blend composition has a crystallization temperature in the range of 110 oC to 130 oC as determined by differential scanning calorimetry (DSC), when the ultra-high molecular weight isotactic polypropylene is entangled.
In accordance with the present disclosure, the self-reinforced polymeric blend composition is disentangled.
In accordance with the present disclosure, a moulded injection impact resistance in the range of 1.2 kJ/m2 and 3.5 kJ/m2 as determined by ASTM D256, when the self-reinforced polymeric blend composition is disentangled.
The self-reinforced polymeric blend composition has high stiffness. In accordance with the present disclosure, the stiffness increases with an increase in Young’s modulus (E). The Young’s Modulus (E) increases with an increase in the percentage of ultra-high molecular weight isotactic polypropylene.
The self-reinforced polymeric blend composition has high average maximum stress and Young’s modulus (elastic modulus) under uniaxial tension in comparison to iPP matrix.
The self-reinforced polymeric blend composition can be used for making pipes, sheets, liner, machine parts and articles with high abrasion resistance.
In another aspect, the present disclosure provides a process for the preparation of a self-reinforced polymeric blend composition.
The process is described in detail.
Predetermined amounts of a low molecular weight isotactic polypropylene and an ultra-high molecular weight isotactic polypropylene are blended at a predetermined temperature at a predetermined mixing torque for a predetermined time period to obtain the self-reinforced polymeric blend composition.
In accordance with the present disclosure, the predetermined amount of the low molecular weight isotactic polypropylene is in the range of 70 mass% to 99 mass % with respect to the total mass of the self-reinforced polymeric blend composition. In an exemplary embodiment, the predetermined amount of the low molecular weight isotactic polypropylene is 98 mass% with respect to the total mass of the self-reinforced polymeric blend composition. In another exemplary embodiment, the predetermined amount of the low molecular weight isotactic polypropylene is 80 mass% with respect to the total mass of the self-reinforced polymeric blend composition. In still another exemplary embodiment, the predetermined amount of the low molecular weight isotactic polypropylene is 75 mass% with respect to the total mass of the self-reinforced polymeric blend composition.
In accordance with the present disclosure, the predetermined amount of the ultra-high molecular weight isotactic polypropylene is in the range of 1 mass% to 30 mass% with respect to the total mass of the self-reinforced polymeric blend composition. In an exemplary embodiment, the predetermined amount of the ultra-high molecular weight isotactic polypropylene is 5 mass% with respect to the total mass of the self-reinforced polymeric blend composition. In another exemplary embodiment, the predetermined amount of the ultra-high molecular weight isotactic polypropylene is 10 mass% with respect to the total mass of the self-reinforced polymeric blend composition. In still another exemplary embodiment, the predetermined amount of the ultra-high molecular weight isotactic polypropylene is 25 mass% with respect to the total mass of the self-reinforced polymeric blend composition.
In accordance with the present disclosure, the predetermined temperature is in the range of 150 oC to 250 oC. In an exemplary embodiment, the predetermined temperature is 200 oC.
In accordance with the present disclosure, the predetermined mixing torque is in the range of 1200 N to 1800 N, when the ultra-high molecular weight isotactic polypropylene is disentangled. In an exemplary embodiment, the predetermined mixing torque is 1500 N, when the ultra-high molecular weight isotactic polypropylene is disentangled.
In accordance with the present disclosure, the predetermined mixing torque is in the range of 500 N to 3250 N, when the ultra-high molecular weight isotactic polypropylene is entangled. In an exemplary embodiment, the predetermined mixing torque is ~3000 N, when the ultra-high molecular weight isotactic polypropylene is entangled.
In accordance with the present disclosure, the predetermined time period is in the range of 2 minutes to 10 minutes. In an exemplary embodiment, the predetermined time period is 3 minutes.
In accordance with the present disclosure the present disclosure, the self-reinforced polymeric blend composition is cooled in a mold at a temperature in the range of 20 oC to 35 oC to obtain the self-reinforced polymeric blend composition of a desired shape. In an exemplary embodiment, the self-reinforced polymeric blend composition is cooled in a mold at a temperature of 25 oC.
In accordance with an embodiment of the present disclosure, the self-reinforcing polymeric blend composition is prepared by using melt extrusion to obtain articles of desired shape.
The self-reinforcing polymeric blend composition of the present disclosure has better mechanical response and bulk density as compared to mixed component polymeric blend, thereby improving the overall costs.
In accordance with the present disclosure, the bulk density of the self-reinforcing polymeric blend composition of the present disclosure is in the range of 0.01 g/cm3 to 0.98 g/cm3. In an exemplary embodiment, the bulk density of the self-reinforcing polymeric blend composition is ~0.4 g/cm3.
The self-reinforcing polymeric blend composition of the present disclosure is made of 100% isotactic polypropylene solving the problem of separating the filler from the polymeric matrix during recycling, thereby increasing the sustainability of the composition.
The self-reinforcing polymeric blend composition of the present disclosure has high stiffness.
Low entanglement density of the ultra-high molecular weight isotactic polypropylene of the present disclosure improves the melt process by reducing the torque needed for mixing. Thereby enabling higher contents of ultra-high molecular weight isotactic polypropylene in the blend composition.
In accordance with the present disclosure, the reinforced component is chemically the same as the matrix solving the intrinsic problem of compatibility without compromising the mechanical response.
Entangled UHMWPP is difficult to process due to very high molecular weight and higher entanglement Whereas the disentangled UHMWPP polymer is already in disentangled form, it is easy to process compared to pure entangled UHMWPP. The high value applications of the self-reinforced polymeric blend composition are in the form of tapes and oriented fibrils with enhanced properties. These self-reinforced polymeric blend compositions have potential to be used in high impact defence Armor type applications such as helmets, gloves and protective jackets.
The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
The present disclosure is further illustrated herein below with the help of the following experiments. The experiments used herein are intended merely to facilitate an understanding of the ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the experiments should not be construed as limiting the scope of embodiments herein. These laboratory scale experiments can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial/commercial scale.
EXPERIMENTAL DETAILS:
Experiment 1: Process for the preparation of self-reinforced polymeric blend composition in accordance with the present disclosure
An entangled UHMWiPP was prepared by using slurry polymerization process in the presence of Ziegler-Natta catalyst (for process see patent IN401932) and a disentangled UHMWiPP was prepared by using a slurry polymerization process in the presence of pyridyl-amido Hafnium post-metallocene catalyst (for process see patent application IN 202021037842).
The viability of blending low molecular weight iPP 515 A (Sabic, Mw: 245,000 g/mol) with UHMWiPP (Mw: 1.2 x106 g/mol) was conducted by using a twin screws mini-extruder (DSM Explore 1000). The content of UHMWiPP were varied and provided in table 1.
The conditions for blending were as follows: A mixture of iPP 515 A and UHMWiPP were loaded in an extruder at 50 rpm at 200 °C for 4 to 6 minutes. The mixture was agitated/stirred at 100 rpm for 3 minutes and then injected into a stainless steel dog-bone like mold (2 mm × 4 mm × 70 mm, with a gage length of 25 mm) using a DSM Xplore IM 5.5 micro injection mold with a barrel temperature of 200 °C and a mold temperature of 25 °C.
Table 1: Self-reinforced polymeric blend compositions prepared from a low molecular weight iPP and an entangled UHMWiPP
Sample no. UHMWiPP
(mass %) Low molecular weight iPP
(PP515A)
(g) UHMWiPP
(g)
1 0 4 0
2 2 3.92 0.08
3 5 3.80 0.20
4 10 3.60 0.40
5 15 3.40 0.60
6 25 3.00 1.00
# Total weight of each sample was 4 grams
The composition as disclosed in Table 1 and the process as described above was for both the self-reinforced polymeric blend compositions containing entangled UHMWiPP.
Characterization of the self-reinforced polymeric blend composition in accordance with the present disclosure
Mechanical properties of the self-reinforced polymeric blend compositions prepared by using entangled UHMWiPP
The measurements of mechanical properties were conducted by using a Zwick/Roell tensile tester machine equipped with 1 kN load cell. Test velocity varied from 0.5 mm/minute to 50 mm/minute after 2% strain point. Each sample was measured 5 times and the results were averaged. An overview of the results is presented in table 2, and figure 1.
Table 2: Mechanical properties of the self-reinforced polymeric blend compositions containing entangled UMMWiPP
Sample E sy ey sm sb eb
no. (GPa) (MPa) (%) (MPa) (MPa) (%)
1 1.44 35 6.9 35 32 449
2 1.48 36 6.9 36 25 355
3 1.59 38 6.9 38 21 316
4 1.66 39 6.2 39 21 155
5 1.78 42 5.6 42 19 62
6 1.91 46 5.0 46 34 19
E: Average Young’s Modulus, sy: Average stress at yield, ey: Strain at yield, sm: Average maximum stress, sb: Average stress at break, eb: Average strain at break
It can be seen from Table 2 that all the samples displayed a tough behaviour during the test, and a reduction in the cross-section area of the tensile bars that indicated the presence of necking and thus the ability of the extruded blend compositions to yield under the applied force. Both the Young’s modulus (E) and stress at yield (sy) increased with higher content of entangled UHMWiPP in the blend composition. On the other hand, the strain at break was considerably reduced for the extruded blend compositions with high content of entangled UHMWiPP. For pure low molecular weight iPP the strain was 449% and for 25 mass% of entangled UHMWiPP, the strain was reduced to 19%. Figure 1 illustrates a stress vs strain curve of self-reinforced polymeric blend composition containing various concentrations of entangled UHMWiPP in the range of 0 mass% to 25 mass% in accordance with the present disclosure, which depicts that the strain was 449% and for 25 mass % of entangled UHMWiPP, the strain was significantly reduced to 19%. The blend composition samples having 15% and 25% of entangled UHMWiPP were found to be the best performing samples.
Single notched IZOD impact test of the self-reinforced polymeric blend composition prepared by using entangled UHMWiPP
The impact strength of the self-reinforced polymeric blend composition of experiment 1, prepared by using entangled UHMWiPP, were evaluated by using compressed molded samples. However, after the compression moulding, these samples displayed surface defects, which might affect the real impact properties. Therefore, impact test samples were prepared by using injection moulding process according to the norm ASTM D256. This injection moulding process allowed control over the surface defects.
Six different blend compositions were obtained by using a twin screw mini-extruder. The amount of entangled UHMWiPP was varied from 0, 2, 5, 10, 15 and 25 mass %. The samples were loaded in the extruder at 50 RPM and 200 °C. Once the materials were loaded, the polymers were mixed at 100 RPM. Finally, the extrudate was injected into a stainless steel dye at 40 °C.
Single notched IZOD impact test was carried out by using 5.5 J pendulum and the results are shown in Table 3.
Table 3: Single notched IZOD impact test of the self-reinforced polymeric blend composition containing entangled UHMWiPP
Sample no. Impact resistance
Injection moulding (kJ/m2)
1 1.7± 0.2
2 1.9± 0.3
3 1.7± 0.4
4 2.2± 0.2
5 2.6 ± 0.4
6 2.6 ± 0.2

A maximum and a minimum value of 2.63 kJ/m2 and 1.65 kJ/m2 were obtained for the blend compositions containing 25 and 0 mass % of entangled UHMWiPP, respectively. Impact resistance of the blend compositions increases as the amount of entangled UHMWiPP increases as the higher molecular weight fraction increases in the blend composition.
Non-isothermal crystallization of the self-reinforced polymeric blend composition prepared by using entangled UHMWiPP
In order to evaluate the effect of the self-reinforced polymeric blend composition for the crystallization behaviour, polarized optical microscopy (POM) experiments were conducted.
Using a LINKAM hot-stage, 1 mg of the blend composition sample was placed between two cover glass plates and the following heating procedure was applied:
50 °C -> 200 °C (10 °C/min)
Isothermal at 200 °C for 20 minutes
200 °C -> 50°C (5 °C/min)
The crystallization temperature was determined when a first spherulite (crystal) was observed. A shift in the crystallization temperature to higher values was observed with increasing content of entangled UHMWiPP (see Table 4). The sample with 0 mass % of UHMWiPP displayed a crystallization temperature around 140 °C, whereas the sample with the highest content of entangled UHMWiPP (25 mass%) started crystallizing at 145 °C.
Table 4: Crystallization temperature of self-reinforced blend compositions containing entangled UHMWiPP as determined by POM
Blend compositions containing entangled UHMWiPP
(mass%) Estimated Tca
(°C)
0 140.0
15 141.5
25 145.0
aDetermined when a first crystallite appeared
In order to corroborate the POM results, Differential scanning calorimetry (DSC) analysis was conducted for all the blend compositions by using the same thermal protocol as POM and the results are summarized in Table 5. Table 5 represents crystallization temperature, onset temperature and crystallization enthalpy of the blend compositions in the first cooling cycle as determined by DSC. DSC determines the complete crystallization temperature of the composition whereas POM results show first crystallite formation temperature.
Table 5: Crystallization temperature of the self-reinforced polymeric blend composition containing entangled UHMWiPP as determined by DSC
Sample no. Tc (°C) Tc onset (°C) ?Hc (J/g)
1 120.1 124.8 126
2 120.0 123.8 123
3 122.3 126.6 127
4 123.7 127.9 123
5 123.9 128.1 125
6 123.9 129.6 125

The DSC results of the blend compositions indicated that the crystallization temperature was increased with the increase in the amount of entangled UHMWiPP. Similarly, POM results of the blend compositions indicated crystallization temperature Tc for the first crystallite formation was increased with increase in the amount of entangled UHMWiPP in the blend compositions.

Torque measurements over time: entangled vs disentangled samples
During the mixing, the differences in the torque were evaluated for both the blend compositions containing 25 mass% of entangled UHMWiPP and 25 mass% of disentangled UHMWiPP (Mw: 1.4 x 106 g/mol). Entanglement density has advantageous differences during the mixing of the blend compositions. Figure 2 illustrated the loading and mixing behaviour of the blend compositions prepared by using entangled UHMWiPP and disentangled UHMWiPP (Mw: 1.4 x 106 g/mol).
As seen from figure 2, the blend compositions containing disentangled UHMWiPP (Mw: 1.4 x 106 g/mol) required less torque than for that containing entangled UHMWiPP and there was a clear difference of torque of around 1000 N for the blend composition. The disentangled UHMWiPP (Mw: 1.4 x 106 g/mol) displayed a low entanglement density compared to entangled UHMWiPP. The torque required for the self-reinforced polymeric blend compositions containing 25% of entangled UHMWiPP was 1500 N.
Single notched IZOD impact test of the self-reinforced polymeric blend composition prepared by using disentangled UHMWiPP
Evaluation of the impact strength of iPP- disentangled UHMWiPP (Mw: 1.4 x 106 g/mol) has been evaluated by using injection moulding samples according to the norm ASTM D256.
Five different blends were obtained by using a twin screw mini-extruder. The amount of disentangled UHMWiPP was varied from 2, 10 and 25 mass%. The samples (3 g total) were loaded in the extruder at 50 RPM and 200 °C. Once the materials were loaded, the polymers were mixed at 100 RPM. Finally, the extrudate was injected into a stainless steel dye at 40 °C.
Three different disentangled UHMWiPP samples were used having: (1) Mw: 1.4 x 106 g/mol, (2) Mw: 2.4 x106 g/mol and (3) Mw: 3.0 x106 g/mol.
Single notched IZOD impact test was carried out by using 5.5 J pendulum.
Table 6: Single notched IZOD impact test of the self-reinforced polymeric blend composition containing disentangled UHMWiPP
Blend composition sample containing disentangled UHMWiPP UHMWiPP
mass % Impact resistance
injection moulding (kJ/m2)
UHMWiPP (Mw:1.4 x 106 g/mol) 2 1.4 ± 0.1
UHMWiPP (Mw: 1.4 x 106 g/mol) 10 2.5 ± 0.2
UHMWiPP (Mw: 1.4 x 106 g/mol) 25 3.2 ± 0.4
UHMWiPP (Mw: 2.4 x106 g/mol) 25 3.0 ± 0.1
UHMWiPP (Mw: 3.0 x106 g/mol) 25 3.2 ± 0.4

As shown in the table 6, the impact resistances were increased with increasing amount of disentangled UHMWiPP (Mw: 1.4 x 106 g/mol) in the injection moulded samples of the blend compositions. However, in case of blend composition samples containing high amount of the disentangled UHMWiPP, the impact resistances were not much affected by the molecular weight of the disentangled UHMWiPP. The impact strength increases with the increasing amount of the disentangled UHMWiPP.
Effect of entanglement density on impact resistances of the blend compositions in accordance with the present disclosure
For studying the effects of entanglement densities on impact resistances of the blend compositions containing entangled UHMWiPP and disentangled UHMWiPP (Mw:1.4 x 106 g/mol), similar molecular weight Mw~ 1.2 x106 g/mol were chosen. Table 7 shows a comparative effect of entanglement density on impact resistance of the self-reinforced polymeric blend compositions.
Table 7: Effect of entanglement density on impact resistance of the blend compositions
Sample containing UHMWiPP UHMWiPP
mass % Impact resistance
of blend composition
Injection moulding (kJ/m2)
Entangled UHMWiPP 2 1.9 ± 0.3
Entangled UHMWiPP 10 2.2 ± 0.2
Entangled UHMWiPP 25 2.6 ± 0.2
Disentangled UHMWiPP (Mw: 1.4 x 106 g/mol) 2 1.4 ±0.1
Disentangled UHMWiPP (Mw: 1.4 x 106 g/mol) 10 2.5 ±0.2
Disentangled UHMWiPP (Mw: 1.4 x 106 g/mol) 25 3.2 ± 0.4

Table 7 indicates that for the blend composition samples having similar molecular weight of entangled UHMWiPP and disentangled UHMWiPP (Mw: 1.4 x 106 g/mol), it was observed that there was higher impact resistance for the blend compositions having disentangled UHMWiPP (Mw: 1.4 x 106 g/mol). The blend composition samples having 10% to 25% of disentangled UHMWiPP was found to be best performing samples.
Effect of entanglement density on the uniaxial tension properties of the blend compositions in accordance with the present disclosure
The uniaxial tensile test was performed on the self-reinforced polymeric blend composition having 25 mass% of both entangled UHMWiPP and disentangled UHMWiPP (Mw: 1.4 x 106 g/mol). The effect of the entanglement density on the mechanical response by using uniaxial tensile test was performed. Triplicate of each samples were tested at room temperature under the same test conditions of strain rate. Tensile measurements were conducted by using a Zwick/Roell tensile tester machine equipped with 1 kN load cell. Test velocity varied from 0.5 mm/minute to 50 mm/minute after 2% strain point.
All the specimens displayed a tough behaviour during the test, a reduction in the cross-section area of the tensile bars indicated the presence of necking and thus the ability of the material to yield under the applied force. The following table represents the average values for the different sample properties when submitted to uniaxial tensile test.
Table 8: Mechanical properties of different blend composition samples when submitted to uniaxial tensile test
Blend composition samples
containing - E
(GPa) sy
(MPa) ey
(%) sm
(MPa) sb
(MPa) eb
(%)
25 wt% entangled UHMWiPP 1.9 46 5.0 46 34 19
25 wt% disentangled UHMWiPP (Mw: 1.4 x 106 g/mol) 1.1 40 6.0 41 27 22
E: Average Young’s Modulus, sy: Average stress at yield, ey: strain at yield, sm: Average maximum stress, sb: Average stress at break, eb: Average strain at break
In general, the self-reinforced polymeric blend composition containing 25 wt% of entangled UHMWiPP displayed higher mechanical properties when compared to the self-reinforced polymeric blend composition containing 25% of disentangled UHMWiPP (Mw: 1.4 x 106 g/mol).
Further, Figure 3 indicates that the blend composition samples containing 25 wt% of entangled UHMWiPP had higher Young’s modules, which indicates more stiffness, whereas the blend composition samples containing 25 wt% of disentangled UHMWiPP showed higher strain at yield and strain at break.
Determination of melt process ability of the self-reinforced polymeric blend composition by evaluating tensile properties
The melt process ability of the self-reinforced polymeric blend compositions containing 25 wt% of UHMWiPP, pure UHMWiPP and pure low molecular weight iPP 515 A were evaluated by using a mini-extruder and an injection-molding machine.
For tensile test blend composition samples were prepared by using (1) disentangled UHMWiPP (Mw: 1.4 x106 g/mol), and (2) entangled UHMWiPP (Mw: 1.2 x106 g/mol). In short, 3.5 g of the polymers or blend compositions were placed in the twin-screw mini-extruder at 200 °C and mixed at 100 RPM for 3 minutes. The extrudate was injection molded into a stainless steel dog-bone like mold (2 mm × 4 mm × 70 mm, with a gage length of 25 mm) by using a DSM Xplore IM 5.5 micro injection mold with a barrel temperature of 200 °C and a mold temperature of 25 °C. Tensile measurements were conducted by using a Zwick/Roell tensile tester machine equipped with 1 kN load cell. Test velocity varied from 0.5 mm/minute to 50 mm/minute after 2% strain point.
It was observed that the blend composition samples prepared by using disentangled UHMWiPP (Mw: 1.4 x 106 g/mol) was successfully injection molded and the cavity of the molds were filled completely with the polymer. This was an indication of the good melt process ability of the composition and attributed to the low entangled state of UHMWiPP.
In contrast to this, the blend composition samples prepared by using entangled UHMWiPP suffered from poor melt process ability, and an increase in the viscosity hinder the injection molding process. These composition samples were not suitable for tensile test. The poor melt process ability of composition samples of entangled UHMWiPP indicate high entanglement density of UHMWiPP.
A result of tensile test of the composition prepared by using 25% of disentangled UHMWiPP (Mw: 1.4 x 106 g/mol) are presented in the figure 4. The result of tensile test of the composition prepared by using 25% of UHMWiPP (Mw: 1.4 x 106 g/mol) were compared with pure disentangled UHMWiPP (Mw: 1.4 x 106 g/mol) sample and the pure 515A sample (low molecular weight iPP). The pure disentangled UHMWiPP (Mw: 1.4 x 106 g/mol) samples did not display a normal yield behaviour when compared to the blend composition containing 25 mass% UHMWiPP (Mw: 1.4 x 106 g/mol) and the pure iPP 515 A sample. For the blend composition prepared by using 25% of disentangled UHMWiPP (Mw: 1.4 x 106 g/mol), the stress was continuously increased as the strain reached the higher values and a sudden decrease was observed upon sample failure. Nonetheless, a clear and similar trend was observed with increasing amount of disentangled UHMWiPP (Mw: 1.4 x 106 g/mol) component. There was increase in the maximum stress (the samples can withstand) with an increase in the amount of UHMWiPP (not shown in figure). This may be due to the disentangled UHMWiPP chain of PP 200117 sample converted in to entangled form with respect to time.
Further, the chain disentanglement increases with higher molecular weight of the UHMWiPP, so with an increase in the strain there was increase in the stress.
Furthermore, the pure disentangled UHMWiPP (Mw: 1.4 x 106 g/mol) displayed an average increase of 10% on the strain at break when compared to the compositions prepared by using 25% disentangled UHMWiPP (1.4 x 106 g/mol). The pure disentangled UHMWiPP (1.4 x 106 g/mol) sample displayed an average elastic modulus (E) of 2.3 in comparison to the 1.1 GPa value of the blend composition and 1.4 GPa of the pure 515A sample.
Thus, it was clear that the use of disentangled UHMWiPP samples enhanced the melt process ability of the blend compositions. The mechanical properties of the self-reinforced polymeric blend compositions were greatly benefitted from the addition of the disentangled UHMWiPP component and were strongly affected by its molecular weight.
TECHNICAL ADVANCEMENTS AND ECONOMICAL SIGNIFICANCE
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of:
the self-reinforced polymeric blend composition that:
• requires low torque for mixing;
• has high melting temperature;
• has high abrasion resistance; and
• has improved mechanical response, thermal properties and processability;
and
the process for preparation of the self-reinforced polymeric blend composition that:
• is simple and economic.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The foregoing description of the specific embodiments so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation. , Claims:WE CLAIM:
1. A self-reinforced polymeric blend composition comprising:
(a) 70 mass% to 99 mass% of a low molecular weight isotactic polypropylene matrix with respect to the total mass of the self-reinforced polymeric blend composition; and
(b) 1 mass% to 30 mass% of an ultra-high molecular weight isotactic polypropylene with respect to the total mass of the self-reinforced polymeric blend composition.
2. The self-reinforced polymeric blend composition as claimed in claim 1, wherein said low molecular weight isotactic polypropylene matrix has
- a molecular weight in the range of 100,000 g/mol to 300,000 g/mol;
- a melting point in the range of 155 oC to 160 oC when heated at a rate of 10 oC/minute; and
- a molecular weight distribution selected from unimodal and bimodal.
3. The self-reinforced polymeric blend composition as claimed in claim 1, wherein said ultra-high molecular weight isotactic polypropylene has
- a molecular weight in the range of 1.0 x 106 g/mol to 4.0 x 106 g/mol,
- a bulk density in the range of 0.01 g/cc to 0.98 g/cc,
- a polydispersity index in the range of 1.2 to 7;
- a complex viscosity
- ? at a shear stress of 0.1 rad/s at 190 °C in the range of 160,000 Pa•s to 700,000 Pa•s; and
- a unimodal molecular weight distribution.
4. The self-reinforced polymeric blend composition as claimed in claim 1 is characterized by having:
• an average Young’s modulus (E) in the range of 0.5 GPa to 2.00 GPa;
• an average stress at yield (sy) in the range of 35 mPa to 50 mPa;
• an average strain at yield (ey) in the range of 4.0% to 7.0%;
• an average maximum stress (sm) in the range of 35 mPa to 50 mPa;
• an average stress at break (sb) in the range of 15 mPa to 35 mPa; and
• an average strain at break (eb) in the range of 15% to 75%.
5. The self-reinforced polymeric blend composition as claimed in claim 1, wherein said ultra-high molecular weight isotactic polypropylene is disentangled.
6. The self-reinforced polymeric blend composition as claimed in claim 5, wherein a mixing torque is in the range of 1200 N to 1800 N; and a moulded injection impact resistance is in the range of 1.2 kJ/m2 to 3.5 kJ/m2 as determined by ASTM D256.
7. The self-reinforced polymeric blend composition as claimed in claim 1, wherein said ultra-high molecular weight isotactic polypropylene is entangled.
8. The self-reinforced polymeric blend composition as claimed in claim 7, wherein a mixing torque is in the range of 500 N to 3250 N; a crystallization temperature is in the range of 110 oC to 130 oC as determined by differential scanning calorimetry (DSC); and a moulded injection impact resistance is in the range of 1.2 kJ/m2 and 3.0 kJ/m2 as determined by ASTM D256.
9. A process for the preparation of a self-reinforced polymeric blend composition, said process comprising blending predetermined amounts of a low molecular weight isotactic polypropylene and an ultra-high molecular weight isotactic polypropylene at a predetermined temperature at a predetermined mixing torque for a predetermined time period to obtain said self-reinforced polymeric blend composition.
10. The process as claimed in claim 9, wherein said blend composition is cooled in a mold at temperature in the range of 20 oC to 35 oC to obtain said self-reinforced polymeric blend composition of a desired shape.
11. The process as claimed in claim 9, wherein said predetermined temperature is in the range of 150 oC to 250 oC; and said predetermined time period is in the range of 2 minutes to 10 minutes.
12. The process as claimed in claim 9, wherein said predetermined mixing torque is in the range of 1200 N to 1800 N, when said ultra-high molecular weight isotactic polypropylene is disentangled.
13. The process as claimed in claim 9, wherein said predetermined mixing torque is in the range of 500 N to 3250 N, when said ultra-high molecular weight isotactic polypropylene is entangled.
14. The process as claimed in claim 9, wherein the predetermined amount of:
• said low molecular weight isotactic polypropylene is in the range of 70 mass% to 99 mass% with respect to the total mass of the self-reinforced polymeric blend composition; and
• said ultra-high molecular weight isotactic polypropylene is in the range of 1 mass% to 30 mass% with respect to the total mass of the self-reinforced polymeric blend composition.

Dated this 31st day of October, 2023

_______________________________
MOHAN RAJKUMAR DEWAN, IN/PA – 25
of R.K.DEWAN & CO.
Authorized Agent of Applicant

TO,
THE CONTROLLER OF PATENTS
THE PATENT OFFICE, AT MUMBAI