The following works for me in Internet Explorer. Note the addition of the table-layout:fixed
CSS attribute
td {
border: 1px solid;
}
<table style="table-layout: fixed; width: 100%">
<tr>
<td style="word-wrap: break-word">
LongLongLongLongLongLongLongLongLongLongLongLongLongLongLongLongLongLongLongLongLongLongLongLongLongLongLongLongLongLongLongLongLongLongLongLongLongLongLongLongWord
</td>
</tr>
</table>