Effect of heat cycling on melting and crystallization of PHB/TiO<sub>2</sub> compounds

Jaques, Nichollas Guimarães; Silva, Ingridy Dayane dos Santos; Barbosa Neto, Manoel da Cruz; Ries, Andreas; Canedo, Eduardo Luis; Wellen, Renate Maria Ramos

doi:10.1590/0104-1428.12416

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Original Article • Polímeros 28 (2) • Apr-Jun 2018 • https://doi.org/10.1590/0104-1428.12416 copy

Effect of heat cycling on melting and crystallization of PHB/TiO₂ compounds

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Compounds of poly(3-hydroxybutyrate) (PHB) and titanium dioxide (TiO₂) with filler content between 1% and 10% were prepared in a laboratory internal mixer. The effect of heating and cooling rates on the crystallization and melting of PHB/TiO₂ compounds was investigated by differential scanning calorimetry (DSC). Melt and cold crystallization rates rise with increasing cooling/heating rates. A higher cooling rate translates to a lower melt crystallization temperature, while a higher heating rate results in a higher cold crystallization temperature. TiO₂ promotes melt crystallization of PHB, behaving as a nucleant agent. The total crystallinity developed after melt and cold crystallization decreases for low levels of TiO₂, i.e. 2% per weight, and is almost independent of the heating/cooling rate. The melting temperatures and rates are minimally affected by both the heating rate and filler content. The results suggest that the desired PHB microstructure can be controlled by filler content and adjusted heating/cooling rate.

Keywords:
crystallization; DSC; melting; PHB; titanium dioxide

*T_g*	*T_mc*	*T_cc*	*T_mp*
2	71.9	54.3	172.6

Neat PHB
	Melt Crystallization																				Cold Crystallization
ϕ	*T_mp*					*c_max*					ΔH_m					ΔX_c					*T_mp*			*c_max*				ΔH_m					ΔX_c
(°C/min)	(°C)					(min⁻¹)					(J/g)					(%)					(°C)			(min⁻¹)				(J/g)					(%)
5	77.2					0.26					44.01					30.1					--			--				--					--
7.5	69.6					0.25					27.81					19.1					50.8			1.06				11.45					7.8
10	71.9					0.31					17.74					12.2					54.3			1.28				21.61					14.8
15	64.0					0.54					5.21					3.6					64.0			1.52				38.66					26.5
20	--					--					--					--					71.8			1.68				53.56					36.7
30	--					--					--					--					81.2			1.98				28.20					19.3
PHB + 1%TiO₂
		Melt Crystallization																			Cold Crystallization
ϕ		*T_mp*					*c_max*							ΔH_m					ΔX_c		*T_mp*		*c_max*				ΔH_m				ΔX_c
(°C/min)		(°C)					(min⁻¹)							(J/g)					(%)		(°C)		(min⁻¹)				(J/g)				(%)
5		84.3					0.27							31.30					21.4		--		--				--				--
7.5		68.8					0.30							26.78					18.3		46.9		1.13				4.21				2.9
10		65.6					0.42							18.81					12.9		49.1		1.49				9.17				6.3
15		63.1					0.57							7.72					5.3		56.3		1.82				34.0				23.3
20		--					--							--					--		56.3		1.94				31.04				21.3
30		--					--							--					--		78.0		2.12				51.95				35.6
PHB + 2%TiO₂
			Melt Crystallization																		Cold Crystallization
ϕ			*T_mp*					*c_max*				ΔH_m					ΔX_c				*T_mp*	*c_max*			ΔH_m				ΔX_c
(°C/min)			(°C)					(min⁻¹)				(J/g)					(%)				(°C)	(min⁻¹)			(J/g)				(%)
5			79.2					0.36				35.99					24.7				--	--			--				--
7.5			76.9					0.43				30.54					20.9				--	--			--				--
10			70.3					0.47				28.49					19.5				--	--			--				--
15			65.3					0.56				20.15					13.8				53.5	1.86			11.90				8.15
20			--					--				--					--				59.6	2.24			27.08				18.5
30			--					--				--					--				78.2	1.82			36.92				25.3
PHB + 4%TiO₂
				Melt Crystallization																	Cold Crystallization
ϕ				*T_mp*					*c_max*				ΔH_m					ΔX_c			*T_mp*	*c_max*			ΔH_m					ΔX_c
(°C/min)				(°C)					(min⁻¹)				(J/g)					(%)			(°C)	(min⁻¹)			(J/g)					(%)
5				86.3					0.43				29.69					20.3			--	--			--					--
7.5				83.2					0.56				31.12					21.3			--	--			--					--
10				77.8					0.68				28.61					19.6			--	--			--					--
15				69.7					0.71				24.12					16.5			52.9	2.69			0.67					0.5
20				66.4					0.86				26.42					18.1			55.0	2.52			6.24					4.3
30				--					--				--					--			72.5	1.95			15.16					10.4
PHB + 10%TiO₂
					Melt Crystallization																Cold Crystallization
ϕ					*T_mp*					*c_max*					ΔH_m					ΔX_c	*T_mp*	*c_max*				ΔH_m						ΔX_c
(°C/min)					(°C)					(min⁻¹)					(J/g)					(%)	(°C)	(min⁻¹)				(J/g)						(%)
5					91.2					0.58					36.52					25.0	--	--				--						--
7.5					87.9					0.78					37.75					25.9	--	--				--						--
10					83.7					0.92					35.56					24.4	--	--				--						--
15					78.3					1.05					30.82					21.1	--	--				--						--
20					72.9					1.21					31.54					21.6	--	--				--						--
30					--					--					--					--	--	--				--						--

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Effect of heat cycling on melting and crystallization of PHB/TiO2 compounds

Abstract

Effect of heat cycling on melting and crystallization of PHB/TiO₂ compounds