Effects of different polypropylene and ammonium lignosulfonate contents on the crystallization behavior, rheological behaviors, and mechanical properties of ethylene propylene diene monomer/ polypropylene/ ammonium lignosulfonate composites

Abstract

Thermoplastic elastomer (TPE), made from ethylene propylene diene monomer (EPDM) and polypropylene (PP) based on reactive blending, has excellent processing performance and characteristics and a wide range of applications. However, there are currently no reports in the literature regarding the usage of TPE in making composite boards. In this paper, EPDM, PP, and ammonium lignosulfonate (AL) were used as the raw materials, polyethylene wax was used as the plasticizer, and a dicumyl peroxide vulcanization system with dynamic vulcanization was used to make a new kind of composite material. This research studied the influences of the PP and AL contents on the crystallization behavior, mechanical properties, and rheological properties of the composites. The results showed that the PP content had a noticeable impact on the performance of the composites. The AL content had a major impact on the modulus of elasticity of the composite board. Accordingly, this kind of composite material can be used as an elastomer material for the core layer of laminated flooring.

Full Article

Effects of Different Polypropylene and Ammonium Lignosulfonate Contents on the Crystallization Behavior, Rheological Behaviors, and Mechanical Properties of Ethylene Propylene Diene Monomer/ Polypropylene/ Ammonium Lignosulfonate Composites

Rui Gou ^a,b and Minghui Guo ^a,*

Thermoplastic elastomer (TPE), made from ethylene propylene diene monomer (EPDM) and polypropylene (PP) based on reactive blending, has excellent processing performance and characteristics and a wide range of applications. However, there are currently no reports in the literature regarding the usage of TPE in making composite boards. In this paper, EPDM, PP, and ammonium lignosulfonate (AL) were used as the raw materials, polyethylene wax was used as the plasticizer, and a dicumyl peroxide vulcanization system with dynamic vulcanization was used to make a new kind of composite material. This research studied the influences of the PP and AL contents on the crystallization behavior, mechanical properties, and rheological properties of the composites. The results showed that the PP content had a noticeable impact on the performance of the composites. The AL content had a major impact on the modulus of elasticity of the composite board. Accordingly, this kind of composite material can be used as an elastomer material for the core layer of laminated flooring.

Keywords: Polypropylene (PP); Ammonium lignosulfonate (AL); Morphology; Rheological properties; Mechanical properties

Contact information: a: Key Laboratory of Bio-based Material Science and Technology (Ministry of Education), Northeast Forestry University, Harbin 150040, China; b: College of Art, Qingdao University of Science & Technology, Qingdao 266061, China; *Corresponding author: gmh1964@126.com

INTRODUCTION

Polypropylene (PP) is a highly crystalline thermoplastic resin with configuration regularization. It is a popular compound because of its low cost and good performance in regard to its abrasive resistance, heat resistance, chemical stability, electrical properties, and processing properties. However, because of its poor resistance to cold and aging, the impact strength and toughness of PP are not satisfactory at lower temperatures. Consequently, its application is restricted (da Costa et al. 2006). A number of techniques have been employed to reinforce and toughen PP, including the addition of various elastomers as modifiers. The modification of a thermoplastic material with an elastomer has demonstrated a four-fold increase in the impact strength (da Silva and Coutinho 1996; Jiang et al. 2000) The thermoplastic polyolefin (TPV) compounded with ethylene propylene diene monomer (EPDM) and PP during dynamic vulcanization has both a rubber elasticity and thermos plasticity; hence, it is widely used in the automotive, construction, and electronics fields, and has maintained a fast growth rate every year.

Lignin is the second most abundant natural polymer in the plant world, next to cellulose. It is also the only natural resource that can provide renewable aromatic compounds (Rastogi and Dwivedi 2008; Stewart 2008). As a by-product of the pulp and paper industry (Belgacem et al. 2003; Fan and Zhan 2008), the annual output of lignosulfonate is approximately one million tons (Belgacem el al. 2003; El Mansouri and Salvadó 2006), but the utilization rate is low. Most lignin is disposed of as waste or burned, which not only wastes resources, but also pollutes the environment (Mohan et al. 2006). Lignosulfonate is a water-soluble anionic surfactant; as such, it has a characteristic surface activity and has many applications (Palmqvist et al. 2006; Vishtal and Kraslawski 2011; Chandra et al. 2015; Khazieva et al. 2015), including as an adhesive for drilling (Zhang and Yin 2002), detergent, glue, animal feed, particleboards (Jin et al. 2010), and cement additive (Grierson et al. 2005; Ansari and Pawlik 2007). Recently, there have many studies on the composite material combined from lignosulfonate with some polymer materials to improve the composite performances, including flame retardancy (Lu et al. 2018), thermal properties and thermal stabilization (Shao et al. 2017), dispersion property (Liu 2018), conductivity (Arvinte et al. 2017; Shao et al. 2018), spinnability (Ouyang et al. 2017), dye-adsorption performance (Lü et al. 2017), absorbency (Lv et al. 2018), crystallization behavior (Ye et al. 2017), and so on.

In this study, a new type of thermoplastic polymer material was made by mixing EPDM, PP, and ammonium lignosulfonate (AL). The effects of the PP and AL contents on the properties of the EPDM/PP/AL composites were systematically investigated.

EXPERIMENTAL

Materials

Extrusion-grade isotactic PP was purchased from Sinopec Maoming Branch (Maoming, China), and its model number is PPH-T03 (Melt Mass-flow Rate (MFR) = 3.0 g/10 min ± 0.5 g/10 min). The EPDM was supplied by Petro China Jilin Petrochemical Company (Jilin, China), and its model number is J-3080P (density = 0.87 g/cm³; 70.9% ethylene content; Mooney Viscosity (ML) (4125 °C) = 74 dN•m; 4.2% ENB content). The AL was purchased from Shenyang Xingzhenghe Chemical Co., Ltd. (Shenyang, China) and was used without any further purification. Its composition was as follows: 4.8 wt.% moisture, 10.8 wt.% ash, 51.7 wt.% total lignin, and 26.9 wt.% carbohydrates.

Methods

Composite preparation

The preparation of the EPDM/PP/AL composites was performed in an intermeshing co-rotating twin-screw extruder (SH30, Nanjing Rubber Machinery Plant, Nanjing, China). The EPDM, PP, and AL were mixed according to the quality percentage. The EPDM content was 100 phr, and the PP and AL contents were 50 phr, 100 phr, and 150 phr. After mixing, the vulcanizing agent, active agent, and plasticizer (Table 1) were added into the blends. Following this step, the blends were mixed in a high-speed mixer (SHR-10A, Zhangjiagang Tonghe Plastic Machinery Co., Ltd., Zhangjiagang, China) at 750 rpm for 5 min to 8 min to guarantee that the materials were mixed evenly. The premixes were dynamically vulcanized in a specific twin-screw extruder. The rotation speed of the screw axis and the temperature in the extruder are given in Table 2. The composite was placed between the parallel flat plates (200 mm × 300 mm) of a mechanically controlled oil-heated press (SL-6, Harbin Special Plastic Products Co., Ltd., Harbin, China) for the final pressing process. The composite was pressed at 175 °C for 5 min according to a pre-programmed hot-pressing schedule. In this process, a 3-mm steel thickness gage was used to control the thickness of the board. Seven panels were produced for each of the target conditions. To obtain the final boards, 30 mm were trimmed off the edges and the final board dimensions were 150 mm × 220 mm × 3.3 mm. The panels were stored at room temperature for 2 d prior to the analyses described below.

Table 1. Amounts of Vulcanizing Agents, Active Agents, and Plasticizer

DCP = dicumyl peroxide; TAIC = triallyl isocyanurate; PE wax = polyethylene wax

Table 2. Rotation Speed of the Screw Axis and Temperature in the Extruder

Scanning electron microscopy

The composite microstructures were analyzed with scanning electron microscopy (SEM) (Quanta200, FEI, Hillsboro, OR, USA) at 10.0 kV. Prior to the SEM analysis, the sample surfaces were coated with a thin layer of gold using an ion sputter coater to make the samples conductive.

X-ray diffraction analysis

X-ray diffraction (XRD) patterns were obtained using an X-ray diffractometer (D/max 2200, Rigaku, Japan) operating with Cu K radiation ( = 0.15406 nm) at 40 kV and 30 mA in the 2range from 5 to 50, with the scan rate set to 5 min⁻¹ .

Rotational rheological properties

The pellets prepared for the EPDM/PP/AL composites were injection-molded into test samples measuring 25 mm (diameter) × 2.2 mm (thickness) using a mini injection molder (Haake MiniJet, Thermo Scientific, Hanau, Germany). Prior to testing, the sample was heated to 200 °C and equilibrated for 5 min to erase the previous thermal and deformation history. Tests were run using a rotational rheometer (Discovery HR-2, TA Instruments, New Castle, DE, USA) equipped with a pair of parallel plates (2 mm in working distance and 25 mm in diameter). The dynamic frequency sweep was run at 200 °C from 0.01 rad/s to 100 rad/s at a 0.5% strain amplitude in the linear region. Three replicates were tested for each formulation.

Mechanical properties

Dumbbell-shaped tensile specimens with the dimensions 165 mm × 13 mm × 3 mm were measured using a universal mechanical machine (RGT-20A, Shenzhen Regear Instrument Cooperation, Shenzhen, China) according to ASTM D638-14 (2014). The tests were conducted at a crosshead speed of 5 mm/min and the deflections were measured using a 50-mm extensometer (RGT-20A, Shenzhen Regear Instrument Cooperation, Shenzhen, China).

Specimens with the dimensions 80 mm × 13 mm × 3 mm were measured under three-point bending using the universal mechanical machine in accordance with ASTM D790-17 (2017). A crosshead speed of 5 mm/min and a span length of 56 mm were used for the test.

Analysis method

SPSS13.0 was used for data statistics and analysis. Analysis of covariance was used for analysis of the influence of the content of PP and AL on the properties of EPDM/PP/AL composites. The Duncan new multiple range test (DMRT) was used to compare the mechanical properties and rheological properties of composites. The letters A, B, and C were used to indicate the significance of differences. If the letters are the same, it means the difference is not significant. If the letters are different, it means the difference is significant.

RESULTS AND DISCUSSION

Mechanical Properties of the Composites

The amount of EPDM used was fixed, and the amount of PP and AL used were varied. This was assumed to have a fixed effect, and the performances of the EPDM/PP/AL composites were analyzed using the linear mixed model of the type III test. Table 3 shows that the mechanical properties of the composites were significantly affected by the amount of PP, while the tensile modulus, flexural strength, and flexural modulus were all significantly affected by the amount of AL.

Table 3. Variance Analysis of the Linear Mixed Model for the Mechanical Properties with Different PP and AL Contents

Effects of the PP content on the mechanical performances of the composites

Table 4 shows the standard deviations of the mechanical test results of the EPDM/PP/AL composites with different PP contents. Figure 1 shows that the amount of PP had a significant influence on the mechanical properties of the EPDM/PP/AL composites.

Table 4. Descriptive Statistics for the Mechanical Properties with Different PP Contents

Fig. 1. Effects of the different PP contents on the mechanical properties of the composites: (a) flexural strength, (b) flexural modulus, (c) tensile strength, and (d) tensile modulus

The flexural strength, flexural modulus, tensile strength, and tensile modulus of the composites increased with an increase in the amount of PP. The flexural and tensile strengths had significant differences when the PP dosage was 50 phr, 100 phr, and 150 phr. This was because the PP is a crystalline polymer (Mandal et al. 2014); therefore, when its content increased, the crystallinity of the EPDM/PP/AL composite increased. As such, the composite material had a better resistance performance to external forces. These factors led to a better mechanical performance. This conclusion is consistent with previous results reported in the literature (Choudhary et al. 1991; Shibryaeva et al. 2001; Humbert et al. 2011). Also, the tensile and flexural moduli of the composites increased as the PP content increased. This was because the elastic modulus and degree of crystallinity of the composites have a linear relationship (Niesten and Gaymans 2001; Humbert et al. 2011; Xiong et al. 2011). The PP content of the EPDM/PP/AL composites led to an increase in the crystallinity of the composite material; thus, the elastic modulus of the composite was improved.

Figure 2 shows the SEM photos for the EPDM/PP/AL composites with different PP contents. The EPDM particles with different PP contents were all at the micron level distributed uniformly as an “island” in the “sea” phase of the PP and formed an obvious “sea-island” two-phase structure. With an increasing PP content, the particle size of the EPDM particles decreased and the interfacial compatibility improved. When the PP content was 50 phr, the EPDM particle size was the largest and the phase interface was clear. This was probably because of the following reasons. When the rubber content is high, EPDM particles easily coalesce. Also, when the PP content was 100 phr, the EPDM particle size decreased and the combination of the two phases improved, but there was still a lot of phase interface. Lastly, when the PP content was 150 phr, the EPDM particle size was the smallest with more uniform dispersion and the phase interface was greatly reduced, which indicated that the two phases were closely combined. This was why the mechanical properties of the composites were improved with an increase in the PP content.

Fig. 2. SEM photos of the EPDM/PP/AL composite with different PP contents: (a) 50 phr, (b) 100 phr, and (c) 150 phr

Effects of the AL content on the mechanical performances of the composites

The main innovation of this paper was the addition of AL to the blends as the main raw material. Therefore, the key research focus of this paper was to determine the influence of different AL contents on the properties of the composite materials. In this paper, the AL amounts were 50 phr, 100 phr, and 150 phr, and the composite properties were studied accordingly. Table 5 shows the standard deviations of the mechanical test results of the EPDM/PP/AL composites with different AL contents. Figure 3 shows that the flexural and tensile moduli of the EPDM/PP/AL composites increased with an increasing AL content, and the difference was significant. This was because the AL functional groups can impart colloid properties (Areskogh and Henriksson 2011).

Table 5. Descriptive Statistics for the Mechanical Properties with Different AL Contents

Fig. 3. Effect of the different AL contents on the mechanical properties of the composites: (a) flexural strength, (b) flexural modulus, (c) tensile strength, and (d) tensile modulus

As the AL content increased, the viscosity and elastic modulus of the EPDM/PP/AL composites increased. This indicated that the function of AL in the composite system was similar to the function of natural lignin in plant fibers and had a reinforcing effect on a mixed system. Additionally, AL can produce free radicals under a high temperature shearing force (Shen et al.2013). These free radicals can combine with side chains of rubber molecules, improve the ability of composite materials to resist deformation, and improve the composite stiffness.

The flexural and tensile strengths of the composites were not significantly influenced by the AL content. The flexural strength increased with an increase in the AL content. The tensile strength increased at first and then decreased as the AL content increased. When the AL dosage was 100 phr, the tensile strength of the composites was at its highest. These results were not consistent with the research results of Toriz et al. (2002), who studied PP and lignosulfonate composites. According to Toriz et al. (2002), the tensile and flexural strengths of the composites decreased with an increase in the lignosulfonate dosage. This was because of the existence of EPDM in the composite. Lignin can increase the mechanical properties of EPDM (Zhang and Ding 2001; Xu et al. 2015). Accordingly, with certain increases in the lignin content, the mechanical properties of the EPDM/PP/AL composites increased.

Figure 4 shows the SEM photos of the EPDM/PP/AL composites with different AL contents. The photos show that with increases in the lignin content, the composite interface condition worsened and the phase interface became clearer. When the lignin content was 50 phr, the specimen section had a good continuity and interfacial bonding, without obvious classification between the different phases. When the lignin content was 100 phr, the specimen section had a good continuity and close interfacial bonding, but there was obvious separation between the different phases. When the lignin content was 150 phr, the phase interface was clear and the gap between the phases became bigger. The stress concentration increased, which led to a decrease in the tensile strength of the composite.

Fig. 4. SEM photos of the EPDM/PP/AL composites with different AL contents: (a) 50 phr, (b) 100 phr and (c) 150 phr

Rheological Properties of the Composites

Table 6 lists the effects of the different PP and AL dosages on the rheological properties of the EPDM/PP/AL composites. The results showed that the PP content had significant impacts on the rheological properties. Furthermore, the AL content had significant impacts on the storage and loss moduli of the composites.

Table 6. Variance Analysis of the Linear Mixed Model for the Rheological Properties with Different PP and AL Contents

G’ = storage modulus; G” = loss modulus; η* = complex viscosity

Effects of the PP content on the rheological performance of the composite

Figures 5 and 6 show that the PP content had significant effects on the rheological properties of the EPDM/PP/AL composites.

Fig. 5. Relationship of the storage (a) and loss moduli (b) with the different PP contents

Fig. 6. Relationship of the complex viscosity of the composite with the different PP contents

Specifically, there were significant differences in the storage and loss moduli between the three different dosages of PP. The storage and loss moduli were the highest when the PP content was 50 phr, and they decreased as the PP content reached 100 phr. When the PP content was 150 phr, these values were the lowest. The complex viscosity of the composites had similar trends. These results were in compliance with the results of a study done by Zhou et al. (2008) on high-density polyethylene/PP/EPDM blends. These results were because of the “island” of EPDM scattered in the “sea” of PP within the blend system containing EPDM, PP, and AL (Sengers et al. 2004). The AL worked as a reinforcing agent in the system. The increase in the PP content led to an increase in the “sea” area and a reduction in the density of the EPDM. Therefore, the viscosity of the system was reduced and the storage and loss moduli of the system decreased.

Effects of the AL content on the rheological performances of the composites

Figure 7 shows that the AL content had a significant effect on the storage and loss moduli of the EPDM/PP/AL composites. With an increase in the AL dosage, the storage and loss moduli of the composites increased.

Fig. 7. Relationship of the storage (a) and loss moduli (b) with the different AL contents

Fig. 8. Relationship of the complex viscosity with different AL contents

Figure 8 shows that the AL content had little impact on the complex viscosity of the composites, but the value increased with an increase in the AL content. This was a result of the AL molecule size being larger and the hindrance on the aromatic ring being large; as such, the molecule was not easy to move (Dong et al. 2008). Similarly, under a high temperature shear force, there were interactions between the free radicals of the AL (Shen et al. 2013) and side chain of the EPDM molecule (Xu et al. 2015). These interactions led to an increased viscosity, as well as an increase in the storage and loss moduli of the composites.

Crystallization Behavior of the Composites

Table 7 shows that the amount of PP and AL has a significant influence on the crystallization behavior of EPDM/PP/AL composites. The content of PP has a significant effect on the peak area and peak height of the crystallization, and the content of AL has a significant effect on the peak area and the full width half maximum (FWHM) of the crystallization peak of the composites.

Table 7. Variance Analysis of the Linear Mixed Model for the XRD diagrams data with Different PP and AL Contents

Effects of the PP content on the miscibility of the composite

Figure 9 shows that the diffraction peak area, peak height and FWHM of the composites increase with the increase of PP contents.

Fig. 9. XRD diagrams data of the composite with the different PP contents

Especially for the diffraction peak area which has significant differences. As shown in Fig. 10, with the increase of PP content the diffraction peaks intensity of the composite increases. But the main diffraction peaks remain the same positions, and they are in the same crystal structure. This indicates that the crystallinity of the mixed system increases with the increase of PP content. This is because PP is the main crystalline substance in the mixed system, so that the amount of PP has a significant effect on the crystallization behavior of the composites. This conclusion is consistent with previous studies.

Fig. 10. XRD patterns of the composite with the different PP contents

Effects of the AL content on the miscibility of the composite

Figure 11 shows that the peak area and peak height of the composites decreased with the increase of Al content. And the difference was significant between the AL content in 50phr and 150phr. The FWHM of the composites increased with the increase of AL content, and there were significant differences between AL content in 50 phr and 150 phr. This is because AL content had significant impact on the viscosity of the composite system and the viscosity increased with the increases of AL content, which led to the uneven dispersion of the components in the system. This hampers the intermolecular force of polypropylene and reduces the crystallization area. With the increase of AL content, the strength of the composite increased, but the overall crystallization level of the composites decreased. The results are consistent with the study carried by Kong et al. (2015), who research on the AL content effects on the crystallization while they preparing lignin-based polyester polyols.

Figure 12 shows the XRD patterns of EPDM/PP/AL composites with different Al contents. It is apparent from the figure that the diffraction peak strength of the EPDM/PP/AL composites decreased with the increase of Al content, but the main diffraction peaks remained in the same position, which means that they are the same crystal structure. This indicates that the PP is the main crystalline substance in the system, and the AL only affected the crystallization process of PP. The molecular chain of AL does not pass through the crystallization of PP. It only plays a local effect in the amorphous region of PP. This conclusion is consistent with the study carried by Jiang and Jiang (1999), who studied the crystallinity of the dynamically vulcanized EPDM/PP.

Fig. 11. XRD diagrams data of the composite with the different AL contents

Fig. 12. XRD patterns of the composite with the different AL contents

CONCLUSIONS

EPDM/PP/AL composites were made using a dynamic vulcanization method with a peroxide vulcanization system. The effects of the PP and AL contents on the properties of the EPDM/PP/AL composites were studied. The main conclusions were as follows:

1. The effect of the PP amount on the properties of the composites was significant. With an increase in the PP content, crystallinity and the strength of the composites increased, the viscosity decreased, the mechanical properties were improved, and the plastic characteristics were more significant.
2. The amount of AL had a significant influence on the modulus of elasticity of the composite. With an increase in the AL content, the modulus of elasticity of the composites increased as well. Similarly, the viscosity of the composites increased with an increase in the AL content. However, the viscosity increase was insignificant when the content of AL exceeded 100 phr. The crystallinity of the composite decreases with the increase of AL content.
3. When the PP and AL contents were both 100 phr, the composite had the best comprehensive performance and is suitable for use as the core layer of elastic materials in composite flooring.

ACKNOWLEDGMENTS

This project was supported by Scientific Research Projects of the Forestry Public Welfare Industry. The project code is 201404506.

REFERENCES CITED

Ansari, A., and Pawlik, M. (2007). “Floatability of chalcopyrite and molybdenite in the presence of lignosulfonates. Part I. Adsorption studies,” Miner. Eng. 20(6), 600-608. DOI: 10.1016/j.mineng.2006.12.007

Areskogh, D., and Henriksson, G. (2011). “Immobilisation of laccase for polymerisation of commercial lignosulphonates,” Process Biochem. 46(5), 1071-1075. DOI: 10.1016/j.procbio.2011.01.024

Arvinte, A., Ignat, M., Pinteala, M., and Ignat, L. (2017). “Electrochemical survey of silver nanoparticles-lignosulfonate formation and their assessment in the electrocatalytic oxidation of p-nitrophenol,” Current Analytical Chemistry 13(5), 370-378. DOI: 10.2174/1573411012666161102143930

ASTM D638-03 (2003). “Standard test method for tensile properties of plastics,” ASTM International, West Conshohocken, PA.

ASTM D790-03 (2003). “Standard test methods for flexural properties of unreinforced and reinforced plastics and electrical insulating materials,” ASTM International, West Conshohocken, PA.

Belgacem, M. N., Blayo, A., and Gandini, A. (2003). “Organosolv lignin as a filler in inks, varnishes and paints,” Ind. Crop. Prod. 18(2), 145-153. DOI: 10.1016/S0926-6690(03)00042-6

Chandra, R. P., Gourlay, K., Kim, C. S., and Saddler, J. N. (2015). “Enhancing hemicellulose recovery and the enzymatic hydrolysis of cellulose by adding lignosulfonates during the two-stage steam pretreatment of poplar,” ACS Sustain. Chem. Eng. 3(5), 986-991. DOI: 10.1021/acssuschemeng.5b00124

Choudhary, V., Varma, H. S., and Varma, I. K. (1991). “Polyolefin blends: Effect of EPDM rubber on crystallization, morphology and mechanical properties of polypropylene/EPDM blends. 1,” Polymer 32(14), 2534-2540. DOI: 10.1016/0032-3861(91)90332-D

da Costa, H. M., Ramos, V. D., and Rocha, M. C. G. (2006). “Analysis of thermal properties and impact strength of PP/SRT, PP/EPDM and PP/SRT/EPDM mixtures in single screw extruder,” Polym. Test. 25(4), 498-503. DOI: 10.1016/j.polymertesting.2006.02.003

da Silva, A. L. N., and Coutinho, F. M. B. (1996). “Some properties of polymer blends based on EPDM/PP,” Polym. Test. 15(1), 45-52. DOI:10.1016/0142-9418(95)00012-7

Dong, X.-b., Li, Q., and Tong, G.-l. (2008). “Research and development of PVC/lignin composite,” China Forest Products Industry 35(1), 13-15. DOI: 10.3969/j.issn.1001-5299.2008.01.003

El Mansouri, N.-E., and Salvadó, J. (2006). “Structural characterization of technical lignins for the production of adhesives: Application to lignosulfonate, kraft, soda-anthraquinone, organosolv and ethanol process lignins,” Ind. Crop. Prod. 24(1), 8-16. DOI: 10.1016/j.indcrop.2005.10.002

Fan, J., and Zhan, H. (2008). “Optimization of synthesis of spherical lignosulphonate resin and its structure characterization,” Chinese J. Chem. Eng. 16(3), 407-410. DOI: 10.1016/S1004-9541(08)60097-X

Grierson, L. H., Knight, J. C., and Maharaj, R. (2005). “The role of calcium ions and lignosulphonate plasticiser in the hydration of cement,” Cement Concrete Res. 35(4), 631-636. DOI: 10.1016/j.cemconres.2004.05.048

Humbert, S., Lame, O., Séguéla, R., and Vigier, G. (2011). “A re-examination of the elastic modulus dependence on crystallinity in semi-crystalline polymers,” Polymer 52(21), 4899-4909. DOI: 10.1016/j.polymer.2011.07.060

Jiang, W., Tjong, S. C., and Li, K. Y. R. (2000). “Brittle–tough transition in PP/EPDM blends: Effects of interparticle distance and tensile deformation speed,” Polymer 41(9), 3479-3482. DOI: 10.1016/S0032-3861(99)00747-8

Jiang T., and Jiang, X.-L. (1999). “Study on crystallinity and crystal structure of PP phase in dynamically vulcanized EPDM/PP blends system,” Journal of Functional Polymers 4, 371-375, DOI: 10.14133/j.cnki.1008-9357.1999.04.004

Jin, Y., Cheng, X., and Zheng, Z. (2010). “Preparation and characterization of phenol-formaldehyde adhesives modified with enzymatic hydrolysis lignin,” Bioresource Technol. 101(6), 2046-2048. DOI: 10.1016/j.biortech.2009.09.085

Khazieva, E. B., Naboichenko, S. S., and Bolatbaev, K. N. (2015). “Influence of lignosulfonates on the cementation velocity of copper with zinc,” Russ. J. Non-Ferr. Met.+ 56(2), 142-145. DOI: 10.3103/S1067821215020091

Kong, X.-Z., He S.-S., Liu T., and Di, M.-W. (2015). “Synthesis and characterization of lignin based polyester polyols,” Chemistry and Adhesion 37(3), 171-174.

Liu, Q. (2018). “Properties of sodium lignosulfonate/naphthalene composite CWS dispersant,” Chemical Engineering Design Communications, article no. 2018-01.

Lü, Q.-F., Xie, Q.-L., and Cao, J. (2017). “Synthesis and dye-adsorption performance of polyaniline-lignosulfonate composite: Introducing a comprehensive research experiment,” University Chemistry 32(3), 49-54.

Lu, W. M., Li, Q., Zhang, Y., Yu, H. W., Hisoe, S., Hatakeyama, H., Matsumoto, Y., and Jin, Z. F. (2018). “Lignosulfonate/APP IFR and its flame retardancy in lignosulfonate-based rigid polyurethane foams,” Journal of Wood Science 64(3), 1-7. DOI: 10.1007/s10086-018-1701-4

Lv., G. L., Han, F. Q., and Zhang, C. T. (2018). “Preparation of sodium lignosulfonate-g-AA-AM super-absorbents composites,” Applied Chemical Industry, http://www.cnki.net/kcms/doi/10.16581/j.cnki.issn1671-3206.20180118.033.html, DOI: 10.16581/j.cnki.issn1671-3206.20180118.033

Mandal, A. K., Chakraborty, D., and Siddhanta, S. K. (2014). “Effect of the compatibilizer, on the engineering properties of TPV based on Hypalon^® and PP prepared by dynamic vulcanization,” J. Appl. Polym. Sci. 131(11). DOI: 10.1002/app.40312

Mohan, D., Pittman Jr., C. U., and Steele, P. H. (2006). “Single, binary and multi-component adsorption of copper and cadmium from aqueous solutions on kraft lignin – A biosorbent,” J. Colloid Interf. Sci. 297(2), 489-504. DOI: 10.1016/j.jcis.2005.11.023

Niesten, M. C. E. J., and Gaymans, R. J. (2001). “Tensile and elastic properties of segmented copolyetheresteramides with uniform aramid units,” Polymer 42(14), 6199-6207. DOI: 10.1016/S0032-3861(01)00088-X

Ouyang, Q., Xia, K., Liu, D., Jiang, X. F., M, H. B., and Chen, Y. S. (2017). “Fabrication of partially biobased carbon fibers from novel lignosulfonate–acrylonitrile copolymers,” Journal of Materials Science 52(12), 7439-7451. DOI: 10.1007/s10853-017-0977-x

Palmqvist, L., Lyckfeldt, O., Carlström, E., Davoust, P., Kauppi, A., and Holmberg, K. (2006). “Dispersion mechanisms in aqueous alumina suspensions at high solids loadings,” Colloid. Surface. A 274(1-3), 100-109. DOI: 10.1016/j.colsurfa.2005.09.039

Rastogi, S., and Dwivedi, U. N. (2008). “Manipulation of lignin in plants with special reference to O-methyltransferase,” Plant Sci. 174(3), 264-277. DOI: 10.1016/j.plantsci.2007.11.014

Sengers, W. G. F., Sengupta, P., Noordermeer, J. W. M., Picken, S. J., and Gotsis, A. D. (2004). “Linear viscoelastic properties of olefinic thermoplastic elastomer blends: Melt state properties,” Polymer 45(26), 8881-8891. DOI: 10.1016/j.polymer.2004.10.030

Shao, Y., Guizani, C., Grosseau, P., Chaussy, D., and Benefenti, D. (2017). “Thermal characterization and kinetic analysis of microfibrillated cellulose/lignosulfonate blends,” Journal of Analytical & Applied Pyrolysis 124, 25-34. DOI: 10.1016/j.jaap.2017.03.001

Shao, Y., Guizani, C., Grosseau, P., Chaussy, D., and Beneventi, D. (2018). “Biocarbons from microfibrillated cellulose/lignosulfonate precursors: A study of electrical conductivity development during slow pyrolysis,” Carbon 129, 357-366. DOI: 10.1016/j.carbon.2017.12.037

Shen, P., Chen, F., Cen, L., and Zhou, Y. (2013). “Modification of lignin and its application in rubber,” China Rubber Industry 60(10), 630-635. DOI: 10.3969/j.issn.1000-890X.2013.10.011

Shibryaeva, L. S., Lunis, G. V., and Popov, A. A. (2001). “Polymer compounds based on the three-component blend PP-EPDM-oil: Effect of their structure on physical properties,” Polym.-Plast. Technol. 40(5), 715-725. DOI: 10.1081/PPT-120000310

Stewart, D. (2008). “Lignin as a base material for materials applications: Chemistry, application and economics,” Ind. Crop. Prod. 27(2), 202-207. DOI: 10.1016/j.indcrop.2007.07.008

Toriz, G., Denes, F., and Young, R. A. (2002). “Lignin-polypropylene composites. Part 1: Composites from unmodified lignin and polypropylene,” Polym. Compos. 23(5), 806-813. DOI: 10.1002/pc.10478

Vishtal, A., and Kraslawski, A. (2011). “Challenges in industrial applications of technical lignins,” BioResources 6(3), 3547-3568. DOI: 10.15376/biores.6.3.3547-3568

Xiong, L., Xiong, D., Yang, Y., and Jin, J. (2011). “Friction, wear, and tensile properties of vacuum hot pressing crosslinked UHMWPE/nano-HAP composites,” J. Biomed. Mater. Res. B 98B(1), 127-138. DOI: 10.1002/jbm.b.31842

Xu, G., Yan, G., and Zhang, J. (2015). “Lignin as coupling agent in EPDM rubber: Thermal and mechanical properties,” Polym. Bull. 72(9), 2389-2398. DOI: 10.1007/s00289-015-1411-7

Ye, D. Z., Zhang, X., Gu, S., Zhou, Y., and Xu, W. (2017). “Non-isothermal crystallization kinetics of eucalyptus lignosulfonate/polyvinyl alcohol composite,” International Journal of Biological Macromolecules 97, 249-257. DOI: 10.1016/j.ijbiomac.2017.01.010

Zhang, J., and Ding, Y. H. (2001). “Effect of lignin as couplant added in rubber,” Special Purpose Rubber Products 22(6), 22-23. DOI: 10.16574/j.cnki.issn1005-4030.2001.06.005

Zhang, L.-M., and Yin, D.-Y. (2002). “Preparation of a new lignosulfonate-based thinner: Introduction of ferrous ions,” Colloid. Surface. A 210(1), 13-21. DOI: 10.1016/S0927-757(02)00211-X

Zhou, S., Ai, G.-j., Zhang, Z.-c., He, X-.r., and Yi, F. (2008). “Study on the properties of HDPE/PP/EPDM blend,” Plastics Additives 2, 39-42. DOI: 10.3969/j.issn.1672-6294.2008.02.009

Article submitted: June 14, 2018; Peer review completed: September 9, 2018; Revised version received: November 10, 2018; Accepted: December 28, 2018; Published: January 25, 2019.

DOI: 10.15376/biores.14.1.2079-2096