An investigation of the effect of silane water‐crosslinking on the properties of poly(L‐lactide)

Abstract

A silane‐grafting water‐crosslinking approach was developed to crosslink poly(L‐lactide) (PLLA) by grafting vinylalkoxysilane onto PLLA using dicumyl peroxide, followed by silane hydrolysis to form siloxane linkages between PLLA chains. The degree of silane grafting onto PLLA was qualitatively characterized using Fourier transform infrared spectroscopy and quantitatively determined using inductively coupled plasma mass spectrometry. Crosslinked PLLA films were obtained by curing of silane‐grafted PLLA in hot water. Gel fractions were evaluated in order to calculate the crosslinking reaction kinetics and crosslinking density. Various techniques were used to investigate the effect of silane water‐crosslinking on the thermomechanical properties, hydrolysis resistance and biodegradation of PLLA. In addition to an improvement in thermal stability and mechanical properties, hydrolysis resistance was significantly enhanced as a result of silane water‐crosslinking of PLLA. Moreover, the biodegradation of silane water‐crosslinked PLLA was retarded compared with neat PLLA. Copyright © 2010 Society of Chemical Industry

Silane crosslinking of poly(lactic acid): The effect of simultaneous hydrolytic degradation

“…Han et al [11] reported an increase of thermal stability for silane crosslinking of PLA. The main reason for the contradictory results is the difference in crosslinking temperature.…”

“…The swelling ratio decreases with increasing gel content and decreasing M -c . According to the theory of Flory and Rehner [31], M -c is defined by Equation (3): (3) where " -is the specific volume of the polymer, " 2 is the volume fraction of the polymer in the swollen mass, V 1 is the molar volume of the solvent (80 cm 3 ·mol -1 ), # 12 is the Flory solvent-polymer interaction parameter (0.1 as reported in the literature [11]), M -n is the primary molecular mass, and M -c is the average molecular mass between cross links. The amount of crosslink bonds in a unit volume is known as the crosslink density ($).The crosslink density is related to M -c through Equation (4): (4) where !…”

“…This method was applied to create crosslinked PLA by Han et al [11]. In this study, vinyltrimethoxysilane (VTMO) and vinyltriethoxysilane (VTES) were used and the results showed that siloxane linkage were successfully formed and the thermal and mechanical properties were improved.…”

“…The influence of crosslinking on degradability of PLA has been reported and the results indicated that enzyme was less effective towards crosslinked PLA than neat PLA. In other words, the deterioration of the biodegradability of PLA is affected by crosslinking due to reduction of enzyme diffusion in PLA [11,29]. Södergård et al [30] showed peroxide modifying of PLA with tert-butylperoxybenzoatein melt mixing.…”

“…Crosslinking could be a good strategy to overcome this disadvantage. Radiation and chemical crosslinking are two well-known methods for osslinking and have been reported in the literatures [7][8][9][10][11][12][13][14][15].…”