An organic bioactive pro-oxidant behavior in thermal degradation kinetics of polypropylene films

Due to its versatility and low cost, polypropylene (PP) is one of the most widely used polymers in the world. However, since it does not easily degrade in natural environment, various methods have been studied to reduce its lifetime. The pro-degrading additives promote the polymer degradation process by accelerating the polymer degradation under heat and/or UV. Eco-one is an organic bioactive pro-oxidant additive that induces biodegradation when it is incorporated into a polymeric matrix by attracting microorganisms in the biotic phase. The aim of this work was to investigate the abiotic degradability of this organic bioactive pro-oxidant additive in PP films. Thermal oxidation studies of the specimens were carried out to investigate the abiotic degradability. We analyzed compositions of PP films containing 1, 3, and 5% Eco-one by mass. These films were characterized by thermogravimetric analysis to calculate the activation energy (E _α) and to estimate their lifetime. Differential scanning calorimetry was conducted to provide oxidative induction time. The samples were then aged at 80 °C and characterized by Fourier transform infrared spectroscopy to obtain the carbonyl index (CI). Compositions containing 1% Eco-one additive showed the optimal composition with lower activation energy, and shorter predicted lifetime, suggesting easier thermal degradation. Furthermore, high CI was also observed in samples containing 1% additive, indicating thermodegradation for this composition.     

Processing and properties of recycled polypropylene modified with elastomers

Abstract

This work presents a study of the processability and the characterisation of blends of recycled polypropylene (PP) with two different elastomers. The aim of the work was to demonstrate that the introduction of an elastomeric phase could improve the properties of recycled PP without changing the processing characteristics of the blends in terms of viscosity and temperature. The study was carried out using thermal analysis, thermomechanical analysis and rheological measurements. The rheological analysis of blends of recycled PP and elastomeric additives showed that, despite the different rheological behaviour of the added elastomers, the properties of the blends were dominated by the thermoplastic (PP) phase. A thermogravimetric analysis of the selected blends allowed the calculation of the parameters related to the thermal degradation of such materials and the main results indicated that there were no significant differences between virgin and recycled PP in terms of behaviour at high temperatures. Furthermore, the blending of recycled PP with elastomers did not result in a significant change in thermal degradation behaviour. Crystallisation studies showed that blending polypropylene with elastomers influenced the rate and amount of crystallisation, which increased at low additive concentrations and then decreased at a higher elastomer content. Thermomechanical analysis showed the immiscible character of the blends. The mechanical properties of the blends were affected by the concentration of elastomer, which also influenced the crystallinity of the material.     

Characterization by thermal analysis of PP with enhanced biodegradability

Samples of polypropylene (PP) filled with a biodegradable additive marketed under the Bioefect trademark, were subjected to an outdoor soil burial test for 21 months. Samples were initially characterized by thermogravimetry. The kynetics of the thermal degradation of both the carbonated chains of PP and the additive have been studied by means of the Hirata differential method and the Broido integral method. Such analysis reveals that the additive is more affected by the degradation process than the PP matrix. Changes in the morphology of the samples with the exposure time have been analyzed by Differential Scanning Calorimetry, in terms of the crystalline content of PP and its lamellar thickness distribution. The β‐ and α‐relaxation zones of the dynamic mechanical relaxation spectra of both PP and pure Bioefect have been characterized using the Fuoss‐Kirkwood equation and a deconvolution method. The analysis of the relaxation spectra shows that the interfacial and crystalline regions of the PP matrix are quite affected by the degradation process. On the other hand, it has also been found that changes in the crystallinity and the mechanical behavior of the samples take place in different stages. Such an evolution can be adequately represented by polynomial equations. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2174–2184, 2001     

Effect of an epoxy additive on the electrical aging of impregnated polypropylene films

The lifetime of HV capacitors is drastically enhanced when epoxides are added to the liquid impregnant of the polypropylene films. The aim of this work was to understand the mechanism of action of such an additive. Aging of the dielectric was performed at a high AC field [135 MV/m]. The liquid impregnant, pure benzyltoluene or benzyltoluene with specially selected additives, was saturated with O₂ in order to accelerate PP aging. The degradation of the polypropylene films has been evaluated by the variation of their mean breakdown voltage and by FTIR microspectroscopy. The liquid impregnant has been characterized by gas chromatography. Our results show that the electrical stress enhances an oxidative degradation mechanism of the polymer and the liquid. Epoxides with two or more epoxy groups per molecule and other monomers of two or three functionalities inhibit this degradation. In the presence of such additives, electrical aging leads to the formation of a crosslinked polymeric deposit on the electrodes and the films. We attribute the good behavior of these components, and especially of epoxides in HV capacitors, to their ability to polymerize under an electrical stress and to form a protective layer that further prevents degradation. © 1996 John Wiley & Sons, Inc.     

Characterization by thermal analysis of high density polyethylene/polypropylene blends with enhanced biodegradability

Blends of high density polyethylene (HDPE) and polypropylene (PP) with different biodegradable additives have been subjected to an outdoor soil burial test. The effect of the degradation process on the structural and morphological properties of the samples has been studied by thermogravimetry, differential scanning calorimetry, and dynamic‐mechanical spectroscopy. The thermogravimetric results show that the additive is more affected by the degradation process than the polymeric matrix. Changes both in the crystalline morphology and the activation energies of the relaxation processes take place in different stages, and can be described using polynomial equations. These changes occur on different time scales depending on the additive used. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 174–185, 2002     

Adsorption and recovery of nonionic polymers by neutralization of cellulose fiber surface charge via cationic polyamide‐epichlorohydrin resins

Gelatin‐based graft copolymers of polypropylene (PP), has been synthesized by chemical method using benzoyl peroxide (BPO), as radical initiator. Biodegradation studies of pristine PP and PP‐g‐Gelatin have been carried out by soil burial test in simple soil and soil enriched with nitrogenous content by adding urea. The microbial degradation was substantiated by the direct attack of the microbes on the grafted samples. The rate of degradation by the direct attack was fast in comparison to the degradation in soil burial studies. The biochemical tests performed on the organisms isolated from the soil, identified these organisms as Bacillus circulans, Kurthia gibsonii, and Flavobacterium sp. which helped biodegradation of PP‐g‐Gelatin samples. The degradation of the grafted samples was further confirmed by carrying out the physical characterization of the original samples and the degraded samples by SEM, XRD, and TGA. The XRD and thermal data indicate an increase in the crystallinity of the degraded samples. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

耐划伤剂对车用聚丙烯材料耐划伤和散发性能的影响

采用熔融共混挤出的方法,制备了聚丙烯/滑石粉/弹性体三元共混材料,并考察了两种耐划伤剂对材料耐划伤性能、散发性能和力学性能的影响。采用十字划伤仪和色差仪对材料在常温和热老化(102℃,168 h)条件下的耐划伤性能进行了评价;采用气味评定、顶空–气相色谱、挥发性有机化合物(VOC)袋子法以及雾度仪分别对添加两种耐划伤剂后材料的气味、总挥发性有机化合物(TVOC)以及VOC和雾度进行了测试。结果表明,采用酰胺类和有机硅类耐划伤剂可改善聚丙烯材料表面的耐划伤性能,常温下两者效果相当,但热老化后前者耐划伤性能消失,而后者仍具有良好的耐划伤性能。在散发性能方面,采用有机硅类耐划伤剂在气味等级、VOC、雾度等方面均优于酰胺类划伤剂。相对于酰胺类耐划伤剂,添加有机硅类耐划伤剂的材料韧性和熔体流动速率有所提升。通过使用有机硅类耐划伤剂制备了在耐划伤性能和散发性能上均满足材料要求的汽车零部件。     

Flammability and thermal degradation of intumescent flame‐retardant polypropylene composites

The flammability of polypropylene (PP) composites containing intumescent flame‐retardant additives, i.e., melamine pyrophosphate (MPP) and 1‐oxo‐4‐hydroxymethyl‐2,6,7‐trioxa‐1‐phosphabicyclo[2.2.2]octane (PEPA) was characterized by limiting oxygen index (LOI), UL 94 test, and cone calorimeter. In addition, the thermal degradation of the composites was studied using thermogravimetric analysis (TG) and real‐time Fourier transform infrared (RTFTIR). It has been found that the PP composite only containing MPP (or PEPA) does not show good flame retardancy even at 30% additive level. Compared with the PP/MPP binary composite, the LOI values of the PP/MPP/PEPA ternary composites at the same additive loading are all increased, and UL 94 rating of the ternary composite (PP3) studied is raised to V‐0 rating from no rating (PP/MPP). The cone calorimeter results show that the heat release rate of some ternary composites decreases in comparison with the binary composite. It is noted from the TG data that initial decomposition temperatures of ternary composites are lower than that of the binary composites. The RTFTIR study indicates that the PP/MPP/PEPA composites have higher thermal oxidative stability than the pure PP. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

UV degradation of clay‐reinforced polypropylene nanocomposites

The aim of this work is to experimentally characterize the UV‐degradation process at both the surface and at different layers across the thickness of injection‐molded polypropylene (PP) matrix containing different amounts of nanosized montmorillonite (MMT) clay particles. These nanocomposite materials have been exposed to UV irradiations (λ = 320 nm) at different preset temperatures (25, 45, and 65°C) in the presence of oxygen and during different exposure times. The extent of such process at these layers was determined using both the FTIR spectroscopy and the wide‐angle X‐ray diffraction analyses. The micromechanical properties across the thickness have been characterized using the nanoindentation technique. The obtained results have indicated that the UV‐degradation process for the nanocomposite materials is much more intense than the one observed for the neat PP. Moreover, it has been noted that such degradation process is not uniform across the thickness of the exposed materials. Results obtained from the X‐ray analysis have shown an increase of the crystallinity of the polymer molecules at only the external surface of the exposed materials. This was confirmed using the nanoindentation test as an increase of the Young's modulus at this layer was noted. POLYM. ENG. SCI., 56:469–478, 2016. © 2016 Society of Plastics Engineers     

Study on correlation of filtration performance and charge behavior and crystalline structure for melt‐blown polypropylene electret fabrics

Melt‐blown polypropylene (PP) electret fabrics are widely used as air filter media due to the specific mechanism of electrostatic filtering. In this article, two additives, stearate and modified rosin, are doped to PP fabrics during melt‐blown process. The filtration performance of doped PP gets improved greatly, with filtration efficiency increased by 6% at room temperature but its temperature stability promoted dramatically. As a result, the filtration efficiency of doped PP still remains above 95% of its initial, whereas that of non‐doped PP only remains 58% at 110°C. By XRD characterization the structure modification is observed after doping. The crystallinity increases from 14.17% to 22.64% and 29.62%, respectively. Meanwhile, the crystallite has a smaller size, respectively, 89Å and 86Å as compared to 107Å for non‐doping in the direction vertical to lattice plane (110). This demonstrates that additive doping can give rise to larger crystallinity and more fine‐grained crystallite. Therefore, doped PP improves its charge storage behavior ascribing to expanding interface between crystallite and amorphous region and then enlarging charge trap density. Furthermore, the effect of additive doping on electret charge storage behavior is investigated by short‐circuit TSD, and the filtration performance can be explained relevantly with TSD. A charge storage profile is also adopted to illustrate that the space charge captured by charge traps is in the form of space‐charge dipole with the rigidity of crystallite. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42807.     

Electron spin resonance studies on photodegradable polymers

Films of polyethylene (PE), polypropylene (PP), and polystyrene (PS) containing 1% of selected halogen compounds and films without additives were UV irradiated (253.7 nm) at 77°K and their electron spin resonance (ESR) spectra compared. In each case, the spectra were characteristic of the polymer, and the presence of the additive mainly enhanced the radical yield. No signal was observed for the additives alone after irradiation, suggesting that when incorporated into the polymer, they serve as photosensitizers rather than as primary sources of free radicals in promoting photo-chemical degradation.     

Polypropylene nanocomposites with oxo‐degradable pro‐oxidant: Mechanical,thermal, rheological,and photo‐degradation performance

The objective of the study was to generate degradable polypropylene nanocomposites by incorporation of pro‐oxidant and different fillers like silica, silicate, and thermally reduced graphene. Graphene‐based composites exhibited higher crystallinity attributed to better dispersion and high aspect ratio platelets. Graphene composites with 2.5% additive content significantly enhanced the peak degradation temperature to 464°C as compared to 448°C for pure polymer. The processing conditions used for the nanocomposite generation were optimum as a uniform distribution of filler particles (or platelets) was observed in the PP matrix. The tensile modulus of the graphene composite with 2.5% additive content was 80% higher than pure PP, as compared to 60 and 30% for silicate and silica composites, respectively. Similarly, the storage modulus of the graphene nanocomposite with 1% additive content had 30% increment at 40°C as compared to pure PP. PP‐additive blends as well as PP nanocomposites with silica and silicate were observed to attain 100% degree of embrittlement within 6 months of UV exposure at 30°C. Graphene composites, though, had delayed photo‐degradation due to UV absorption by the platelets and high aspect ratio platelets acting as oxygen barrier for PP matrix, but the pro‐oxidant was successful in attaining controlled degradation. POLYM. ENG. SCI., 56:1229–1239, 2016. © 2016 Society of Plastics Engineers     

Intensification of cavitational activity in sonochemical reactors using different additives: Efficacy assessment using a model reaction

Sonochemical reactors offer excellent promise for the intensification of different chemical processing applications. The current work deals with intensification of cavitational activity using different additives with an objective of decreasing the processing cost as well as enhancing the applicability of sonochemical reactors for different applications. Potassium iodide oxidation has been used as a model reaction. Experiments have been carried out in a laboratory scale ultrasonic horn reactor. The effects of different additives such as air, solid particles (cupric oxide and titanium dioxide), salts (sodium chloride and sodium nitrite) and radical promoters (hydrogen peroxide, ferrous sulphate, iron metal, carbon tetrachloride and t-butanol) on the degradation of potassium iodide have been investigated. Combination of additives has also been investigated for examining the possible synergistic effects in comparison to the use of individual additions. It has been observed that based on the type of additive, optimum concentration needs to be selected and it may not be desirable always to use different additives in combination. It is desirable to select an additive which can give additional reaction mechanism in the system to aid the desired application under question.     

Parameters regulating interfacial and mechanical properties of short glass fiber reinforced polypropylene

The performance of thermoplastic composites is known to depend on the intrinsic properties of the two composite components, the quality of the fiber–matrix interface, and the crystalline properties of their matrix. The objective of this work is to characterize the effect of the addition of modified polypropylene (PP) and silane coupling agent on the mechanical and interfacial properties of short fiber reinforced PP composites. Differential scanning calorimetry (DSC), single fiber composite fragmentation tests (SFC), and mechanical testing are used to understand the different parameters regulating the interfacial properties of composites. No influence of the modified PP on the level of crystallinity is observed. Some differences in the size of the spherulites are observed for acrylic acid grafted PP (PP‐g‐AA). Those samples also show lower mechanical properties in spite of good interfacial interactions. Maleic anhydride grafted PP (PP‐g‐MAh) leads to better mechanical performances than PP‐g‐AA. A high MAh content PP‐g‐MAh grade with low viscosity is the best polymeric additive used in the present work. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2047–2060, 2000     

Efficacy of waterborne polyurethane to prevent the enzymatic attack on paper‐based materials

The chemical and biological deterioration of paper‐based materials is mainly due to the degradation of its main component, the cellulose. However, paper also contains small amounts of organic and inorganic additives which might influence its biodegradability. To protect the paper‐based materials against various degradative agents, coating treatments with polymeric materials might be developed. In this study, the protective effect of commercial waterborne polyurethanes (WPU) against an enzymatic attack was investigated. Uncoated and coated samples with WPU of newsprint were subjected to degradation by enzymatic complexes (cellulosomes) produced by Clostridium cellulolyticum for different incubation times and then characterized using several analytical techniques (energy dispersive X‐ray fluorescence, scanning electron microscopy, nuclear magnetic resonance, Raman and infrared spectroscopy) with the aim to assess if waterborne polyurethanes can be used in paper conservation, looking at their efficacy against the biodegradation induced by enzymes. The selected waterborne polyurethanes showed a high effectiveness in the protection of paper‐based materials when they were submitted to the enzymatic attack. Indeed, their presence delayed the destruction of the cellulose matrix and the release of both soluble sugars and paper additives. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Phase modification of SEBS block copolymer by different additives and its effect on morphology,mechanical and dynamic mechanical properties

The objective of this study is to examine the phase modification of styrene–ethylene butylene–styrene (SEBS) block copolymer by different additives and its influence on morphology and mechanical, and dynamic mechanical properties. The additives chosen are the coumarone–indene (CI), phenol–formaldehyde (PF), paraffin hydrocarbon (PAHY) resins, as well as aromatic oil (AO), polystyrene (PS), polypropylene (PP), ethylene vinyl acetate (EVA) (VA 28 and 45%), and ethylene propylene diene monomer (EPDM) rubber. It is interesting to note that of all the additives, PP has the most prominent effect. The mechanical properties of SEBS polymer are enhanced to a large extent by PP. The value of tan δ maximum of SEBS at both the low and the high temperature transitions is decreased. All the resins and PS increase the storage modulus and the tensile modulus of the SEBS polymer. CI resin and AO modify the hard and soft phases of SEBS polymer. AO, EPDM rubber, and EVA lower the mechanical strength of the SEBS polymer. The results are explained on the basis of morphologystudied with the help of scanning electron microscopy. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:2015–2025, 1998     

纺细旦PP纤维用阻燃树脂制备及其可纺性研究

通过对一系列添加型阻燃剂的阻燃性、可纺性、纺丝环境的对比研究，确定了一种复配阻燃剂。结果表明：该阻燃ＰＰ体系的流动性好、热性能稳定，所纺制的细旦丙纶初生纤维具有较好的可拉伸性能。     

Morphology and Properties of Modified Polypropylene for Extruded Film Applications

Abstract

Change in crystallization morphology of polypropylene (PP) on blending with high density polyethylene (HDPE), and on incorporation of cross-linking agent, trimethyl propane triacrylate (TMPTA), and nucleating agent, aluminium dibenzoate (DBS), was studied using differential scanning calorimetry (DSC), polarizing light microscopy (PLM), and small angle light scattering (SALS). In all, three blend systems: PP-HDPE, PP-HDPE-TMPTA, and PP-HDPE-DBS were developed. Analysis of crystallization exotherm, PLM, and SALS studies indicate that DBS is an effective nucleating agent for PPHDPE system and results in appreciable reduction in spherulite size and increase in percent crystallinity, while on cross-linking there is reduction in both percentage crystallinity and spherulite size. Improvement in overall mechanical properties is observed in all the systems studied. As it is desirable to work with PP having a high degree of crystallinity, low spherulite size and low melt flow index (MFI) for oriented film applications, PP-HDPE-DBS system with a low MFI grade HDPE is found to be most suitable.     

Improving the low-temperature properties of alternative diesel fuels: Vegetable oil-derived methyl esters

This work explores near-term approaches for improving the low-temperature properties of triglyceride oil-derived fuels for direct-injection compression-ignition (diesel) engines. Methyl esters from transesterified soybean oil were evaluated as a neat fuel and in blends with petroleum middle distillates. Winterization showed that the cloud point (CP) of methyl soyate may be reduced to −16°C. Twelve cold-flow additives marketed for distillates were tested by standard petroleum methodologies, including CP, pour point (PP), kinematic viscosity, cold filter plugging point (CFPP), and low-temperature flow test (LTFT). Results showed that additive treatment significantly improves the PP of distillate/methyl ester blends; however, additives do not greatly affect CP or viscosity. Both CFPP and LTFT were nearly linear functions of CP, a result that compares well with earlier studies with untreated distillate/methyl ester blends. In particular, additives proved capable of reducing LTFT of neart methyl esters by 5–6°C. This work supports earlier research on the low-temperature properties; that is, approaches for improving the cold flow of methyl ester-based diesel fuels should continue to focus on reducing CP.     

Biodegradation studies of LDPE filled with biodegradable additives: Morphological changes. I

Low‐density polyethylene (LDPE) samples filled with three commercial biodegradable additives (Mater‐Bi, Cornplast, and Bioefect) have been subjected to an accelerated soil burial test in a culture oven for 1 year. By means of Differential Scanning Calorimetry (DSC), the effect of the degradation in soil in the samples morphology has been analyzed, in terms of their melting temperature, their crystalline content, and their lamellar thickness distribution. These morphological parameters evolve in different stages, depending on the additive used. It has been found that the LDPE–Mater‐Bi samples are the ones exhibiting faster changes in their crystalline content. However, the LDPE blends with Cornplast and Bioefect display more significant changes in their lamellar thickness distribution. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1683–1691, 2002