CRYSTALLIZATION BEHAVIOR OF CROSS-LINKED GRAFTS OF POLYPROPYLENE
0
Citation
0
Reference
20
Related Paper
Abstract:
The cross-linked grafts of polypropylene with high grafting levels and polarity were prepared from isotactic polypropylene (iPP) reacting with maleic anhydride (MAH) and triallyl isocyanurate (TAIC) in solid phase. Rheological characteristic, crystallization and melting behavior, and crystal morphology of the grafts were studied. Addition of TAIC during reaction makes the molecular structure of PP stable and the molten viscosity increases significantly. The crystallization peaks, melt temperatures, crystallinity and crystallization rates of the grafted PP are lower compared to pure PP. But the nucleating ability of the cross-linked graft with higher grafting level is strongest, and the behavior of isothermal crystallization is different from that of PP and MPP. Its nucleation and growth mechanism is two-dimensional growth of crystallites from instantaneous nucleation.Keywords:
Tacticity
Maleic anhydride
Polypropylene
Cite
Abstract Isothermal and nonisothermal crystallizations of isotactic polypropylene (iPP), maleic anhydride (MAH)-grafted PP, and MAH-modified iPP were studied by differential scanning calorimetry (DSC), to evaluate the influence of a small amount of MAH-grafted PP in iPP on its crystallization behavior. Isothermal crystallization was followed in the temperature range from 391 K to 403 K, and the rate constant and Avrami exponents were determined. Nonisothermal crystallization was carried out at different cooling rates (1-20 K/min). It was found that the crystallization kinetics of iPP was significantly altered by modification with the MAH-grafted polymer. A decreased equilibrium melting temperature, as well as decreased surface energy of folding and critical dimensions of a growing nucleus, was determined for the MAH-modified iPP, indicating faster growth of lamellae and a higher rate of crystallization. The improved nucleation ability of the modified polymer was shown to cause a shift in the crystallization peak temperature towards higher values (from 393.7 K to 399.6 K, at a cooling rate of 1 K/min), resulting in crystal structures less disposed to recrystallization. Model composites of iPP and MAH-modified iPP with glass fibers were also analysed. The apparent shear strength of single-fiber model composites with MAH-modified iPP was drastically increased compared with homo-iPP. Keywords: ISOTACTIC POLYPROPYLENEMALEINATED POLYPROPYLENECRYSTALLIZATIONISOTHERMALNONISOTHERMALAPPARENT SHEAR STRENGTH
Maleic anhydride
Tacticity
Polypropylene
Isothermal process
Cite
Citations (18)
Polyvinyl alcohol(PVA)/polypropylene grafted maleic anhydride(PP-g-MAH) blend films were prepared by melting process.The differential scanning calorimetry(DSC) was adopted to develop the crystallization and melting behavior of the blends.Results showed that with the increasing of PP-g-MAH content(less than 50 %),the crystallization and melting temperature of PVA phase increased,the crystallization rate rose,but crystallinity decreased.While with the increasing of PVA content(more than 30 %),the crystallization and melting temperature of PP-g-MAH phase decreased,crystallinity decreased,but the crystallization rate increased.The non-isothermal crystallization kinetics of PVA phase in the blend was studied according to Ozawa′s theory.Results showed that the primary crystallization of PVA phase was in a temperature range of 191~197 ℃,secondary crystallization was in a temperature range of 173~189 ℃.
Maleic anhydride
Polypropylene
Polyvinyl Alcohol
Cite
Citations (0)
High molecular weight polypropylene (HMWPP) with or without a nucleating agent was synthesized in a reactor, and a modified PP was prepared with the materials obtained above and isotactic PP. The crystallization behavior and morphology of the PP compound were investigated by means of differential scanning calorimeter and polarized light microscope. The results show that HMWPP can induce the formation of β-crystals and fine grainy spherulites, and increase the impact strength by 50 %; while the nucleating agent and HMWPP enhance the crystallization temperature and crystallization rate markedly. Moreover, the spherulite size becomes much smaller. The flexural modulus of the material is increased by 32 %, and heat deflection temperature rises by 18 ℃.
Spherulite (polymer physics)
Tacticity
Polypropylene
Flexural modulus
Heat deflection temperature
Polarized light microscopy
Morphology
Cite
Citations (0)
The influence of surface grafting modified nano-silica on the isothermal and non-isothermal crystallization kinetics of isotactic polypropylene (IPP) was investigated by DSC.The silica particles were pre-grafted with styrene,methyl methacrylate,ethyl acrylate and butyl acrylate,respectively.The experimental results show that the addition of nano-silica into PP has an obvious nucleating effect on the crystallization of PP,resulting in higher crystallization temperature and melting point,as well as higher crystallinity and the overall rate of crystallization,but lower crystalline regularity.The surface grafting treatment of the nanoparticles promotes the nucleating effect due to the increased miscibility between the particle and the matrix.The nucleating effect of the particles is also related with their dispersion state in the polymer matrix.The melting behavior of neat PP is different to that of the PP filled with nano-silica.The later has a more uniform crystal structure because the fillers act as nucleates.However,a faster isothermal crystallization process of the PP filled with nano-silica results in a lower equilibrium melting point,implying that the crystalline structure is less perfect in this case.
Tacticity
Polypropylene
Cite
Citations (0)
The non-isothermal crystallization kinetics of polypropylene solid grafted Ethyl methacrylate (PP-g-EMA) at different cooling rate was studied by means of DSC, and the data were analyzed by using Jeiorny, MO and Kissinger methods. The results showed that solid grafted EMA could play a role of heterogeneous nucleating agent in PP, raising the crystallization temperature and crystallinity of PP. Mo method was very suitable to describe the non-isothermal crystallization kinetics of the system. The grafted EMA accelerated the crystallization rate of PP, also changed the mode of the nucleation and the growth of the crystallites. The crystallization activation energies of PP and PP-EMA were calculated by means f Kissinger method. It was found that the grafted EMA increased the crystallization activation energy of PP, hindered the motion of the molecular chain of PP during the crystallization.
Polypropylene
Isothermal process
Cite
Citations (0)
The non-isothermal crystallization behaviors of polypropylene graft poly(vinyl acetate) (PP-g-VAc) with two grafting degrees were studied by differential scanning calorimetry.The kinetics of PP and PP-g-VAc under non-isothermal crystallization conditions were analyzed by Reziorny method and R-t method.The results showed that both Reziorny method and R-t method described the crystallization behaviors successfully,VAc side chains didn't change the nucleation and growth patterns,but decreased the crystallization rate and ability: t_1/2 increased and Z_c decreased,nucleation rate of grafted PP at high graft percentage ( GP) increased,crystallization enthalpy decreased and crystallization parameter F(T) increased with GP.
Polypropylene
Isothermal process
Cite
Citations (0)
Non-isothermal crystallization kinetics of polypropylene/polypropylene grafted 2-acrylamido-2-methylpropanesulfonic acid(PP-g-AMPS) at different cooling rates was studied using differential scanning calorimetry.Jeziorny and Mo methods were used to analyze the DSC data.It showed that both methods described the crystallization behaviors successfully.AMPS side chains did not change the crystallization behaviors obviously,however,increased the crystallization rate.The crystallization activation energy of grafted PP was increased.
Polypropylene
Isothermal process
Cite
Citations (0)
Maleic anhydride
Polypropylene
Tacticity
Avrami equation
Cite
Citations (154)
Halloysite
Polypropylene
Maleic anhydride
Cite
Citations (4)
Abstract This paper describes the nonisothermal crystallization of molten blends of two semicrystalline polymers, polypropylene (PP) and Nylon‐6 (N6). A discussion details the effect of the concentration of the compatibilizing agent, maleic anhydride grafted polypropylene (MAH‐ g ‐PP), on the crystallization behavior. The crystallization thermograms showed one crystallization peak or two crystallization peaks, which were significantly affected by the presence of MAH‐ g ‐PP. The crystallization temperature of N6 levels off down as the concentration of MAH‐ g ‐PP increases, whereas that of PP stays at a roughly constant temperature. These blends containing the compatibilizing agent exhibited concurrent crystallization at the crystallization temperature of PP. The crystallization behavior are also studied by optical microscopy under crossed polarizers. © 1994 John Wiley & Sons, Inc.
Polypropylene
Maleic anhydride
Nylon 6
Cite
Citations (97)