Preparation of a Crosslinked Chitosan Coated Calcium Sulfate Whisker and Its Reinforcement in Polyvinyl Chloride

doi:10.1016/j.jmst.2016.06.006

Abstract

Abstract:

A calcium sulfate whisker (CSW) coated with glutaraldehyde crosslinked chitosan (GACS) was prepared to reinforce polyvinyl chloride (PVC) in this study. The results show that the optimum concentration of both chitosan (CS) and glutaraldehyde (GA) is 0.05?wt%. The tensile strength, impact strength, flexural modulus and vicat softening temperature of the PVC composite with 12?wt% of modified CSW are increased by 17.5%, 40.4%, 0.8% and 3.8% compared with those of the PVC composite with 12?wt% of unmodified CSW, and by 2.9%, 42.4%, 27.1% and 6.8% compared with those of pure PVC, respectively. The dynamic mechanical analysis results indicate that the modified CSW/PVC composite exhibits much higher storage modulus and glass transition temperature than those of unmodified CSW/PVC composite and pure PVC. In addition, the modified CSW/PVC composite also demonstrates good thermal properties with a high rapidest decomposition temperature (T_rpd) and char residue. The scanning electron microscopy images of tensile-fractured surfaces show that the modified CSW has a strong interfacial adhesion with PVC matrix.

Key words: Polyvinyl chloride, Polymer composites, Surface modification, Calcium sulfate, Mechanical properties

Cui Jiayang,Cai Yangben,Yuan Wenjin,Lv Zhongfei,Xu Shiai. Preparation of a Crosslinked Chitosan Coated Calcium Sulfate Whisker and Its Reinforcement in Polyvinyl Chloride[J]. J. Mater. Sci. Technol., 2016, 32(8): 745-752.

Figures/Tables 17

Scheme 1. Mechanism schematic diagram.

Scheme 2. Procedure schematic diagram.

Fig. 1. FTIR spectra of (a) unmodified CSW, (b) CS-coated CSW, and (c) GACS-coated CSW.

Fig. 2. SEM micrographs of (a) unmodified CSW, (b) CS-coated CSW, and (c) GACS-coated CSW.

Table 1. EDS data of unmodified CSW, CS-coated CSW, and GACS-coated CSW

Sample	CSW		CS-coated CSW		GACS-coated CSW
Sample	Weight (wt%)	Atom (at.%)	Weight (wt%)	Atom (at.%)	Weight (wt%)	Atom (at.%)
O	41.9?±?1.6	55.8?±?2.8	40.5?±?1.0	54.0?±?2.1	41.1?±?2.2	51.1?±?3.5
Ca	29.8?±?0.5	15.8?±?0.5	30.0?±?0.3	16.0?±?0.5	25.9?±?2.9	12.9?±?2.2
S	19.6?±?0.3	12.9?±?0.4	19.6?±?1.3	13.0?±?1.2	17.6?±?1.5	10.9?±?1.5
C	8.7?±?2.2	15.4?±?3.7	8.2?±?1.9	14.6?±?3.3	13.7?±?3.2	22.7?±?3.5
N	0.8?±?0.3	1.4?±?0.4	1.6?±?0.3	2.4?±?0.4	1.6?±?0.3	2.4?±?0.4

Fig. 3. Effect of CS concentration on tensile strength and elongation at break of CSW/PVC composites with 5?wt% of CSW.

Fig. 4. Effect of GA concentration on tensile strength and elongation at break of CSW/PVC composites with 5?wt% of CSW.

Fig. 5. SEM micrographs of tensile fractured surfaces for CSW/PVC composites: (a) unmodified CSW; (b) CS-coated CSW; (c) and (d) GACS-coated CSW (the concentrations of CS and GA are 0.05?wt%, the content of CSW is 5?wt%).

Fig. 6. Tensile strength and elongation at break of PVC and PVC/CSW composites with varying content of CSW.

Fig. 7. SEM micrographs of tensile-fractured surfaces for PVC composites with 12?wt% of CSW: (a) unmodified CSW; (b) modified CSW.

Fig. 8. Notched impact strength of unmodified and modified CSW/PVC composites with varying content of CSW.

Fig. 9. SEM micrographs of impact-fractured surfaces for PVC composites with 12?wt% of CSW: (a, c) unmodified CSW; (b, d) modified CSW.

Fig. 10. Flexural strength (a) and flexural modulus (b) of PVC and PVC/CSW composites with varying content of CSW.

Fig. 11. Storage modulus and tanδ of pure PVC and its composites with 12?wt% of unmodified or modified CSW as a function of temperature.

Fig. 12. The curves of displacement as a function of temperature for pure PVC, PVC composites with 12?wt% of unmodified or modified of CSW (a) and VST of PVC and PVC/CSW composites with varying content of CSW (b).

Fig. 13. TGA (up) and DTG (down) curves of pure PVC (a) and its composites with unmodified (b) and modified CSW (c).

Table 2. Trpd and char residue of pure PVC and PVC composites with unmodified or modified CSW

	PVC	Unmodified CSW/PVC	Modified CSW/PVC
Trpd (°C)	309.4	311.0	314.0
Char residue (%)	8.3	16.2	17.0

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