Phase dispersion–crosslinking synergism in binary blends of poly(vinyl chloride) with low‐density polyethylene: Entrapping phenomenon in PVC/LDPE/DCP blend

The co‐crosslinked products and the entrapping phenomenon that may exist in a poly(vinyl chloride)/low density polyethylene/dicumyl peroxide (PVC/LDPE/DCP) blend were investigated. The results of selective extraction show that unextracted PVC was due to not being co‐crosslinked with LDPE but being entrapped by the networks formed by the LDPE phase. SBR, as a solid‐phase dispersant, can promote the perfection of networks of the LDPE phase when it is added to the PVC/LDPE blends together with DCP, which leads to more PVC unextracted and improvement of the mechanical properties of PVC/LDPE blends. Meanwhile, the improvement of the tensile properties is dependent mainly on the properties of the LDPE networks. Finally, the mechanism of phase dispersion–crosslinking synergism is presented. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1296–1303, 2003     

Effect of the various coupling agents on the mechanical and physical properties of thermoplastic‐bagasse fiber composites

Various types of bonding agents have been tried with blends of bagasse fibers and some thermoplastics such as low‐density polyethylene (LDPE), high‐density polyethylene (HDPE), polystyrene (PS), polypropylene (PP), and polyvinyl chloride (PVC). These bonding agents are, namely, pentaerythritol tetracrylate (PETA), 1,6 hexandiol diacrylate (HDA), and dicumyl peroxide (DCP). In addition, a traditional coupling agents 3‐aminopropyltrimethoxy silane (AMPS) and di‐aminopropyltrimetoxy silane (DAMPS) were included for comparison. Electron beam (EB) irradiation is applied only for LDPE and HDPE at 40 and 10 kGy, respectively, before mixing with bagasse fibers. The data obtained reveal that incorporation of bonding agents remarkably increases the mechanical properties for all samples under investigation; the maximum improvement is observed in LDPE followed by HDPE, PP, PS, and PVC composites. Also, the physical properties enhanced but not at the same degree as mechanical properties. Among the tested bonding agents, it was found that PETA, DCP followed by DAMPS have highest efficiency in LDPE, whereas in case of HDPE, EB radiation was higher than PETA followed by DCP. PETA was superior in case of PS composites. Furthermore, PETA and HDA experienced higher efficiency than DAMPS and AMPS in case of PP and PVC composites. Comparison between the properties of thermoplastic composites and medium density fiberboard (MDF) reveals that most of the properties of thermoplastics composites are better than MDF. However, modulus of rupture of MDF was found to be slightly higher than thermoplastics except for PVC composite. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Study on compatibilization-crosslinking synergism in PVC/LDPE blends

Influences of nitrile rubber (NBR, acrylonitrile content 33.5 – 36.5 wt.-%) on the structure and mechanical properties of poly(vinyl chloride) (PVC)/low density polyethylene (LDPE) blends and its synergism with crosslinking agent have been studied. The addition of NBR to the blend is accompanied by a decrease in domain size and improvements in mechanical properties of the blend. When dicumyl peroxide (DCP) is added to the blend together with NBR, good synergism is caused and mechanical properties will improve dramatically. It is concluded that NBR can promote the phase dispersion of PVC and LDPE and their interfacial adhesion. Then, the probability of DCP existing at the interface will increase and more co-crosslinked products will form. Therefore, compatibilization and crosslinking are both exerted sufficiently.     

Application of phase dispersion–crosslinking synergism on recycling commingled plastic wastes

A tetra‐component blend, consisting of low‐density polyethylene (LDPE), polyvinyl chloride (PVC), polypropylene (PP), and polystyrene (PS), was studied as a model system of commingled plastic wastes (LDPE/PVC/PP/PS, mass ratio: 70/10/10/10). Effects of chlorinated polyethylene (CPE), ethylene–propylene–diene monomer (EPDM), styrene–butadiene–styrene (SBS), and their mixture (CPE/EPDM/SBS, mass ratio: 2/2/2) on the mechanical properties and morphology of the system were investigated. With addition of several elastomers and their mixture, the tensile strength of the blends decreased slightly, although both the elongation at break and the impact strength increased. Among these elastomers, EPDM exhibited the most significant impact modification effect for the tetra‐component blends. SBS and the mixture have a good phase‐dispersion effect for the tetra‐component blend. By adding a crosslinking agent [dicumyl peroxide (DCP)], the mechanical properties of the tetra‐component blends also increased. When either SBS or the mixture was added to the blend together with DCP, the probability that the crosslinking agent (DCP) would be at the interface improved because of the phase‐dispersion effect of SBS. Therefore, more co‐crosslinked products will form between LDPE and other components. Accordingly, remarkable improvement of the interfacial adhesion and hence the mechanical properties of the tetra‐component blends occurred. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2947–2952, 2001     

软质PVC鞋底发泡材料的研制

以软质聚氯乙烯（PVC）为主体材料，加入发泡剂偶氮二碳酰胺（AC）、交联剂过氧化二异丙苯（DCP）、柠朦酸、丁腈橡胶（NBR）、泡孔调节剂等，采用一步法模压成型软质PVC鞋底发泡材料。研究AC，DCP、柠朦酸、NBR、泡孔调节剂用量对软质PVC发泡材料密度和力学性能的影响。结果表明，在AC4．0份、DCP0．2份、柠朦酸0．2份、NBR40．0份、泡孔调节剂11.0份时，发泡材料性能优异，其密度和力学性能满足软质PVC鞋底发泡材料的要求。     

PP/LDPE化学交联发泡的研究

聚丙烯(PP)熔融黏度较低,发泡过程中气泡容易从熔体中溢出。在PP中加入低密度聚乙烯(LDPE)和偶氮二异丙苯(DCP),提高PP交联度,从而大大提高PP的熔融黏度。研究了共混聚合物组分的种类和含量对PP交联度的影响。结果表明,在共混过程中,部分PP和LDPE分子在热作用下相互促进,产生了接枝交联;共混物比纯PP的泡孔结构优且发泡效果佳,当LDPE为70%,发泡剂为5%,DCP为0.36%时,PP的发泡效果最好。解决了PP发泡过程中出现的气孔塌陷现象。     

Preparation of Silane-Grafted and Moisture Cross-Linked Low Density Polyethylene: Part I: Factors Affecting Performance of Grafting and Cross-Linking

In the present work, the silane grafting and water cross-linking of low density polyethylene (LDPE) were investigated. The grafting reaction was carried out in an internal mixer and polyethylene cross-linking was done in hot water. The effect of silane, peroxide, catalyst, carbon black, cross-linking time, and cross-linking temperature on the grafting and cross-linking processes are reported. Vinyl trimethoxy silane (VTMO) and di-cumyl peroxide (DCP) were selected as grafting agent and initiator respectively. Silane grafting on polyethylene was determined using Fourier transform infrared (FTIR) spectroscopy and torque monitoring of the mixer. Absorption peak due to –Si–OCH₃ groups in FTIR and torque increasing due to silane grafting in the mixer illustrated that silane-grafting reactions occurred. The FTIR data demonstrated that the extent of silane grafting was increased as the concentration of silane and peroxide was increased. Thermogravimetry analysis (TGA) determined that the thermal stability of LDPE increased by increasing the amount of silane grafting. Gel fraction increased with silane and peroxide concentration. As the percent of of catalyst increase the time scale for specified gel content shifted to shorter times. Incorporation of carbon black into LDPE decreased the extent of silane grafting and gel fraction. Water temperature increasing in cross-linking stage reduced the time to maximum degree of cross-linking.     

LDPE熔融接枝MAH及其增容PA6/LDPE合金的研究

以过氧化二异丙苯(DCP)为引发剂,马来酸酐(MAH)为接枝单体,采用熔融法制备了MAH接枝低密度聚乙烯(LDPE-g-MAH)。研究了不同DCP和MAH配比对接枝反应的影响,并以相对接枝率较高的LDPE-g-MAH作为增容剂,讨论了其用量对尼龙6(PA6)/LDPE合金力学性能的影响。结果表明:LDPE/DCP/MAH质量比为100/0.2/2时,相对接枝率较高,该种配方的接枝物可显著改善PA6/LDPE体系的相容性,在PA6/LDPE(质量比50/50)和PA6/LDPE(质量比80/20)两种体系中,增容剂的最佳用量分别为4~5 phr和2~3 phr。     

层压制备交联LDPE及其形状记忆性能的研究

采用层压成型的工艺,在低剪切应力下制备了交联低密度聚乙烯(XLPE)。对XLPE进行了凝胶含量、形状记忆性能与拉伸强度的测试。结果表明:当过氧化二异丙苯(DCP)质量分数为1.0%时,凝胶含量接近70%并趋于稳定,形状回复率达到100%,XLPE的拉伸强度提高。说明组合加工方法可显著提高DCP的交联效率,XLPE的形状回复与力学性能有明显的改进。     

Influences of contents and molecular weights of LDPE on DOP plasticization of PVC

Influences of contents and molecular weights of low‐density polyethylene (LDPE) on dioctyl phthalate (DOP) plasticization in the poly(vinyl chloride) (PVC) plastisol (PVC/DOP/AO = 100/30/6.5) were investigated using DMA and DSC. The plasticization effects of DOP on the PVC plastisol were found to decrease with increasing LDPE content. A negligible plasticization effect of DOP on the PVC plastisol was found when the LDPE content was equal to or higher than 75 parts per 100 parts by weight of LDPE and PVC together. Based on thermal fractionation experiments, a favorable interaction between LDPE and DOP was developed during melt blending of LDPE and the PVC plastisol. The present interaction enabled the incorporation of DOP into LDPE and decreased the plasticization effects of DOP on the PVC plastisol. A further decrease in the plasticization effects of DOP on the PVC plastisol by the presence of LDPE was found with increasing LDPE molecular weights. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2548–2555, 2002     

Preparation and characterisation of vinylsilane crosslinked low-density polyethylene composites filled with nano clays

The effects of dicumyl peroxide/vinyltriethoxysilane treatment and nanoclay content were investigated for low-density polyethylene (LDPE)/clay nanocomposites. LDPE was treated with 0.1 phr of DCP with, respectively, 1 phr and 3 phr VTES (System A), and with 0.2 phr of DCP with the same amounts of VTES (System B), and then mixed with different contents (1, 3, and 5 wt%) of modified clay (Cloisite 15A). The morphology and extent of crosslinking, as well as the thermal, mechanical, and thermomechanical properties were studied. X-ray diffraction results of all the VTES-treated LDPE/clay nanocomposites showed an increase in interlayer spacing, which indicates that the polymer chains were intercalated between the clay layers. Transmission electron microscopy micrographs of System B showed some evidence of exfoliated clay layers, indicating that the system exhibited a mixed morphology. The clay-containing samples had better thermal stability than LDPE, but the thermal stability did not differ much for the two systems. VTES observably decreased the melting enthalpy of LDPE, while the presence of clay had little influence on this value. This is somewhat contrary to the gel content results that showed a decrease in the extent of crosslinking in the presence of and with increasing clay content. VTES/DCP treatment and the presence of clay observably changed the dynamic mechanical and tensile behaviour of the LDPE.     

Thermal characteristics and temperature profile changes of structurally different polyethylenes with peroxide modifications

Crosslinking and processing characteristics of polyethylenes (PEs) with different molecular architectures, namely high‐density polyethylene (HDPE), linear low‐density polyethylene (LLDPE), and low‐density polyethylene (LDPE), were studied with regard to the effects of peroxide modifications and coolant flow rates. Dicumyl peroxide (DCP) and di‐tert‐butyl peroxide (DTBP) were used as free‐radical inducers for crosslinking the PEs. The characteristics of interest included normalized gel content, real‐time temperature profiles and their cooling rates, exothermic period, crystallinity level, crystallization temperature, and heat distortion temperature. The experiments showed that LDPE exhibited the highest normalized gel content. The real‐time cooling rates, taken from the temperature profiles for all PEs before the crystallization region, were greater than those after the crystallization region. The cooling rate of the PEs increased with the presence of DCP, whereas the crystallization temperature of the PEs was lowered. The HDPE appeared to show the longest exothermic period as compared with those of the LLDPE and LDPE. The exothermic period showed an increase with increasing coolant flow rate, but it was decreased by the use of DCP. As for the effect of peroxide type, the gel content and cooling rate of the PE crosslinked by DCP were higher than those for the PE crosslinked by DTBP. The DTBP was the more effective peroxide for introducing crosslinks and simultaneously maintaining the crystallization behavior of the PE. J. VINYL ADDIT. TECHNOL., 20:80‐90, 2014. © 2014 Society of Plastics Engineers     

Graft copolymerization of oleic acid onto low‐density polyethylene in the molten state

A graft copolymer of oleic acid (OA) onto low‐density polyethylene (LDPE) was prepared using dicumyl peroxide (DCP) as an initiator in the molten state. The grafting was carried out in a Haake rheometer. The effects of the reaction time and the amount of DCP and the monomer on the percentage of grafting were studied. The rheological behavior and the melt‐flow rate of the graft copolymer (LDPE‐g‐OA) were also investigated. FTIR spectroscopy and a mass spectrum were used to characterize the structure of LDPE‐g‐OA. The experimental results showed that when the OA amount was 10 wt % and the DCP amount was 0.4 wt % based on the LDPE the percentage of grafting of LDPE‐g‐OA, prepared by maintaining the temperature at 170°C and the roller speed at 80 rpm, was about 6 wt %. It was found that both LDPE and LDPE‐g‐OA were pseudoplastic fluids. OA was grafted onto LDPE in the form of a monomer and a dimer. The grafted LDPE is expected to act as a compatibilizer between starch and polyethylene. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3299–3304, 2003     

Diallyl orthophthalate as a reactive plasticizer for improving PVC processability, Part III: Curing, properties, and phase separation

Diallyl orthophthalate (DAOP) is investigated as a reactive plasticizer to aid the processing of PVC by reducing the melt's viscosity and thus minimizing the processing temperature so that decomposition of PVC can be effectively avoided during time-consuming processing operations such as rotational moulding. A range of PVC/DAOP blends have been prepared with dicumyl peroxide (DCP) or cumyl hydroperoxide (CHP) as radical initiators, and their chemorheology, properties and morphology have investigated by dynamic rheometry, DMTA, SEM and solvent resistance. DCP was found to be a better initiator than CHP for polymerization of DAOP in blends with PVC because the former's high decomposition temperature matches well with the processing temperature of the PVC/DAOP blends. DMTA indicates that the T_g of the cured PVC/DAOP blends are very close to that of PVC and have a higher storage modulus at the rubbery region. SEM images show that phase separation occurs during cure of the blend and that solid poly(DAOP) nano-particles are embedded in the PVC continuous phase when the PVC content is more than 30 wt%. This cure and phase separation of DAOP from the PVC matrix can successfully recover the PVC's thermal-resistance properties.     

Pyrolysis of waste-derived fuel mixtures containing PVC

This paper describes an experimental analysis of the pyrolysis of PVC and mixtures of PVC with wood (Finnish pine) and LDPE (low density polyethene) in nitrogen at 250-400 °C. The aim is to optimise the temperature range for producing low-chlorine or chlorine-free fuel in a dehydrochlorination reactor without pyrolysing any of the other combustible fractions. Results are presented for various process temperatures for PVC, PVC/wood and PVC/LDPE mixtures. It was found that the PVC tested is dehydrochlorinated at approximately 350 °C, and that secondary pyrolysis is suppressed when LDPE is present.     

Structural changes of PVC in PVC/LDPE melt‐blends: Effects of LDPE content and number of extrusions

This paper investigates the structural changes of polyvinyl chloride (PVC) in melt‐blends of a low‐density polyethylene (LDPE) and polyvinyl chloride (PVC), and the effects of LDPE content and number of extrusion passes. These effects were examined in terms of changes in weight average molecular weight and number average molecular weight, polyene and carbonyl indices, color changes of the blend, and the variations in glass transition and decomposition temperatures. It was found that loading LDPE into PVC led to the formation of short‐chain LDPE grafted PVC (s‐LDPE‐g‐PVC) copolymers, via a macro‐radical cross‐recombination reaction, which had greater weight average molecular weight with unchanged number average molecular weight, increased decomposition temperature, lower glass transition temperature, as compared to the pure PVC sample. The dehydrochlorination reaction of PVC was suppressed by the macro‐radical cross‐recombination reaction with addition of LDPE, the effect being more pronounced at 13.0 wt% LDPE. For a given LDPE content, the macro‐radical cross‐recombination and dehydrochlorination reactions competed with one another, thus causing the increases in molecular weight average and molecular weight number up to the 4th extrusion pass. At the 5th extrusion pass, the dehydrochlorination reaction was predominant owing to a depletion of LDPE content to be grafted onto PVC molecular chains. The glass transition and decomposition temperature decreased with increasing number of extrusion passes. Polym. Eng. Sci. 44:487–495, 2004. © 2004 Society of Plastics Engineers.     

Extrudate swell and texture of PS,LDPE, ABS,PVC melts and their blends in extrusion capillary flow using a magnetic die

The extrudate swell behavior and extrudate texture of various thermoplastic melts, namely, polystyrene (PS), low‐density polyethylene (LDPE), acrylonitrile‐butadiene styrene (ABS) copolymer, poly(vinyl chloride) (PVC), and their blends, were examined weith a magnetic die system in a constant‐shear‐rate capillary rheometer at a shear rate range 5–28 s^?1 and a temperature range 170–230 °C. The extrudate swell results obtained from the magnetic die were then compared with those produced by a nonmagnetic die. The results showed that the extrudate swell increased with shear rate, but decreased with temperature. In a pure polymer system, up to 25% increase in the extrudate swell was observed with the application of the magnetic field to the PS melt, and the effect decreased in the order ABS > LDPE > PVC. The extrudate swell changes were associated with the changes in rheological properties of the melts. The extrudate textures of the ABS and PVC melts were improved by the magnetic field. In PS/LDPE or PS/ABS blend, it was found that the magnetic die resulted in higher values of the extrudate swell than the nonmagnetic die for all blends, the magnetic effect being less as the LDPE or ABS content was increased. For PS/LDPE system, the extrudate swell of the PS melt did not change much with addition of 20% LDPE, but slightly decreased at the LDPE loading of 40%. At higher LDPE loadings, the extrudate swell increased towards the value of the pure LDPE melt. For PS/ABS system, the extrudate swell ratio progressively decreased with increasing ABS content. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 509–517, 2002     

化学改性高熔体聚丙烯的制备及其挤出发泡特性研究

以过氧化二异丙苯(DCP)为交联剂、三烯丙基异三聚氰酸酯(TAIC)为助交联剂,通过平行双螺杆挤出机制备了高熔体强度聚丙烯(HMSPP),研究了DCP用量对PP的流变性能、材料的热性能及发泡特性的影响。结果表明:DCP与TAIC配合使用能有效控制PP交联,从而制得有一定凝胶含量的HMSPP,同时材料的耐热性也得以提高,当DCP用量为0.8份,TAIC为3份时,制备的HMSPP,挤出发泡特性最佳。     

Photocross-linking of low-density polyethylene. I. Kinetics and reaction parameters

The kinetic characteristics and the reaction conditions of photocross-linking of low-density polyethylene (LDPE) in the melt have been studied using benzophenone (BP) and its derivatives such as 4-chlorobenzophenone (4-CBP) as photoinitiator and triallyl cyanurate (TAC) as cross-linker. The efficiency of the photoinitiated cross-linking system LDPEBP-TAC and various factors affecting the cross-linking process, such as photoinitiator and cross-linker and their concentrations, irradiation time, temperature, and atmosphere, and UV light intensity were examined extensively by determining gel content, IR, and UV spectra. It has been found (i) that LDPE samples of 2–3 mm thickness are easily cross-linked to a gel content of about 70% with a UV-irradiation time of about 15 s under optimum conditions; (ii) that the photoinitiating system of a suitable initiator combined with a multifunctional cross-linker such as 4-CBP–TAC can enhance the efficiency of photocross-linking reactions, especially by increasing the initial rate of cross-linking; (iii) that photocross-linking of LDPE should be carried out in the melt, which increases the penetration of UV light by decreasing the scattering by crystallites, and (iv) that the rate of cross-linking is proportional to the square of the light intensity. An increase in light intensity can decrease the concentration of photoinitiator required to reach a certain rate of cross-linking. The photocross-linking of polyethylene is promising for industrial applications. © 1993 John Wiley & Sons, Inc.     

相容剂对LDPE/MVQ并用胶热老化性能的影响

以低密度聚乙烯（LDPE）、相容剂、甲基乙烯基硅橡胶（MVQ）混炼胶为主要原料,加入自由基捕捉剂和硫化剂过氧化二异丙苯（DCP）,在双辊上将各组分进行熔融共混,通过平板硫化机将共混物硫化,制备出了LDPE／MVQ并用胶。本文重点研究了相容剂对LDPE／MVQ并用胶的力学性能和热老化性能的影响。结果表明,适量相容剂可以改善并用胶中LDPE和MVQ的相容性,提高材料的力学性能,而过多相容剂会阻碍LDPE与MVO共硫化反应的进行,降低并用胶机械强度和热老化性能。随着相容剂用量的增加,并用胶的拉伸强度、断裂伸长率和撕裂强度及热老化系数先增大后减小,其用量为15hpr时并用胶的综合性能最好。