Cant select time on custom form

Hi

When I try and include the datepicker in a custom form, the time part is missing and I can only select the date. I have using the following custom code in my form:

 $date_format = 'Y-m-d H:i';

    $form['dateAndTime'] = [
      '#type' => 'materialize_date_time',
      '#title' => t('Start Date'),
      '#date_format' => $date_format,
      '#default_value' => \Drupal\Core\Datetime\DrupalDateTime::createFromTimestamp(time()),
      '#weight' => '3',
    ];

Am I missing something to get it to fire the time part? If I switch back to 'datetime' the time component appears in the standard format?

Thanks

Billy